(Source: Electrical Safety First)
Replacing a consumer unit in domestic premises.
Guidance on the management of electrical safety and safe isolation procedures for low voltage installations.
Connecting a microgeneration system to a domestic or similar electrical installation (in parallel with the mains supply).
Electrical installation condition reporting: Classification Codes for domestic and similar electrical installations.
Electrical installations and their impact on the fire performance of buildings. Part 1 – domestic premises: Single family units (houses, flats, maisonettes, bungalows).
Now merged with Best Practice Guide No. 1.
Test instruments for electrical installations: Accuracy and consistency.
Selection and use of plug-in socket-outlet test devices.
Safe installation of retrofit LED lamps.
Further information about Microgeneration please visit the Microgeneration Certification website.
Replacing a consumer unit in domestic premises where lighting circuits have no protective conductor
This Best Practice Guide fully recognises that unearthed lighting circuits do not comply with BS 7671. In following the guidance, the installer accepts this and must be satisfied that all new work on any particular installation addresses the risks.
In all cases, the initial approach should be to persuade the customer that protective conductors should be provided.
This Best Practice Guide has been produced by Electrical Safety First in association with the bodies indicated on page 2. It is intended to promote best practice, and takes into account the requirements of BS 7671: 2008
By following the guidance it is considered that the installer will have provided protection for the customer so far as is reasonably practicable.
The purpose of the guidance is to protect customers and installers against dangerous situations that could arise from an old installation where an installer is replacing a consumer unit or other main switchgear in a home built before 1966 and wired in accordance with the 13th Edition, or earlier, of the IEE Wiring Regulations.
These regulations did not require a protective conductor to be taken to every lighting point and related accessory as is the current requirement.
A consumer unit need not be replaced simply because it has rewireable fuses, cartridge fuses or older-type circuit-breakers, as these devices can provide satisfactory overcurrent protection. Similarly, a consumer unit need not be replaced because it does not incorporate RCD protection, as there may be ways to provide this protection other than by replacing the consumer unit.
Best Practice Guide Number 6 provides further general advice and guidance for designers, installers, verifiers and inspectors where a consumer unit or other main switchgear is to be replaced in a home wired in accordance with the Sixteenth Edition or earlier of the IEE Wiring Regulations.
This Best Practice Guide applies only to the reconnection of existing lighting circuits in domestic premises that do not have circuit protective conductors.
There is no legal requirement, and no regulation in BS 7671, requiring an existing electrical installation to be upgraded to current standards.
However, there is a requirement under the Building Regulations for England and Wales to leave the installation and the building no worse in terms of the level of compliance with other applicable parts of Schedule 1 to the Building Regulations than before the work was undertaken. (Schedule 1 gives the requirements with which building work must comply,)
Similarly, the Scottish Building Standards Technical Handbooks, which provide guidance on achieving the standards set in the Building (Scotland) Regulations 2004, require that any work associated with the replacement of a service, fitting or equipment by another of the same general type is to a standard no worse than at present.
Main earthing and bonding
The installation of a replacement consumer unit must comply with the current edition of BS 7671. In particular, the installer must, as a minimum, verify that:
a) the main earthing terminal of the installation is connected to an adequate means of earthing via a suitably sized earthing conductor
b) the main protective bonding is adequate, and
c) the meter tails and the distributor’s equipment have adequate current-carrying capacity.
Note. Some electricity distributors have requirements regarding the earthing conductor, main bonding conductors and meter tails that exceed the requirements of BS 7671.
If any of the above conditions (a), (b)or (c)is not met, the customer should be informed that upgrading is required. If the customer refuses, the installer should not proceed with fitting the new consumer unit.
Reasons for change
Where possible, when an installer is pricing the replacement of a consumer unit, checks should be made at a switch, a lighting point and the consumer unit, to ascertain if circuit protective conductors are present. If the presence of circuit protective conductors cannot be established, it is essential that the customer is advised that there is a possibility that some lighting points may not be earthed.
To enable the work to comply fully with the current standard and improve safety, it is necessary to install protective conductors to every lighting point and related accessory. This could involve considerable additional cost, not only in installing new cables, but also in the renewal of decorations unless the customer is willing to accept surface wiring.
In the circumstances where the customer is unable or not prepared to accept either the cost or disruption of re-wiring the circuit(s) or installing separate circuit protective conductors, but still requires a new consumer unit to be installed, the installer needs to carry out a risk assessment before agreeing to replace only the unit.
Where cables are lead or rubber-sheathed, then deterioration of the cables is likely to necessitate re-wiring when the consumer unit is replaced.
A distress change occurs when the consumer unit has suffered mechanical or fire damage, has become unusable through overheating or found to be in a dangerous condition with exposed live parts. This situation usually requires immediate replacement of the consumer unit.
It should be explained to the occupant before the consumer unit is replaced that:
• if an immediately dangerous condition is found in an existing final circuit, it will not be possible to reconnect that circuit until remedial action is carried out, and
• it will be necessary to return to the installation to carry out any further work that would have been required if the replacement of the consumer unit had been planned. This further work, where required, must be carried out without delay.
In all cases, the initial approach should be to persuade the customer that protective conductors should be provided.
Where it is proposed to replace a consumer unit, but the customer is unable, or not prepared, to accept either the cost or disruption of re-wiring the circuit(s) or installing separate protective conductors, a risk assessment should be undertaken for the purpose of advising the customer as to the level of risk that would exist on completion of the proposed work.
A disclaimer does not absolve the installer from responsibility.
The risk assessment requires inspection and testing:
Inspection is required to establish whether or not, for the circuits concerned, there are:
1. Class I light fittings or metal accessories 2. Class I light fittings or metal accessories that are simultaneously accessible to earthed metalwork or extraneousconductive-parts, including conductive flooring
3. Accessible Class I light fittings or metal accessories in special locations or outdoors
4. Lighting circuits that supply socket-outlets that may be used for portable equipment.
Testing is required where there are items that fall into categories 1 to 4 above.
There are two tests to be applied (with the main switch off):
(1) To establish whether or not equipment is earthed. This test should be applied between the earth terminal in the existing consumer unit and all Class I light fittings and metal plate accessories. If the resistance value is 1 ohm or less, the equipment may be considered to be earthed.
(2) To establish whether or not the insulation resistance of the circuits is satisfactory.
a)This test should be applied separately to each lighting circuit between the live conductors (line and neutral connected together) and the earthing terminal in the consumer unit, with that terminal connected to the means of earthing. The resistance should be at least 1 megohm.
b)The test should then be applied between line and neutral connected together and the exposed-conductive-parts of every Class I lighting fitting and metal switch plate that Test (1)has shown not to be earthed. The resistance should be at least 1 megohm.
If the circuit does not fulfil the requirements of either (a)or (b), there would be a risk of electric shock if the circuit were to be re-energised. The customer must be advised in writing that this danger exists, and that the equipment must be disconnected from the supply unless it is agreed to install 30 mA RCD protection as part of the work.
Action following risk assessment
1. If none of the items in the risk assessment indicate that there is a significant shock risk, the replacement of the consumer unit may proceed.
2. A notice with black letters on a yellow background should be fixed on or adjacent to the consumer unit stating:
3. If the risk assessment indicates that there is a shock risk due to there being unearthed Class I lighting fittings or metal accessories that can be touched simultaneously with earthed metal parts or extraneousconductive-parts, these lighting fittings and metal accessories should be replaced with Class II lighting fittings and insulated accessories. If the customer declines to have the Class I lighting fittings and metal accessories replaced, the installer should decline to commence the replacement of the consumer unit.
4. If the risk assessment indicates that the insulation resistance is less than 1 megohm, the installer should decline to carry out the replacement of the consumer unit without further investigation and appropriate remedial work.
BS 7671 does not permit a residual current device (RCD) to be the sole means of protection against electric shock. RCDs should not be used as an alternative to adequate earthing. However, a 30 mA RCD will provide additional protection and could be used where unearthed Class I lighting fittings or accessories are not simultaneously accessible with earthed metal parts or extraneous-conductive-parts. This method will not satisfy the requirements of BS 7671 and should be listed as such on the electrical installation certificate for the replacement consumer unit.
If the customer refuses to accept the advice to install circuit protective conductors to lighting circuits and related accessories, the installer is advised to fit 30 mA RCD protection to the circuit(s) concerned to reduce the risk of electric shock.
Where a consumer unit is being replaced, additional protection by means of RCDs in accordance with Regulation 415.1 must be provided to the extent required by the current edition BS 7671, such as for:
• socket-outlets (Regulation 411.3.3 refers)
• mobile equipment for use outdoors (Regulation 411.3.3 refers)
• cables concealed in walls or partitions, where required by Regulations 522.6.6 to 522.6.8, and
• circuits of locations containing a bath or shower (Regulation 701.411.3.3).
Circuits that are to be provided with RCD protection must be divided between a sufficient number of RCDs or otherwise designed as necessary to avoid hazards and minimise inconvenience in the event of a fault (Regulations 314.1 and 314.2 refer).
Inspection, testing and certfication
The work carried out should be inspected and tested and an electrical installation certificate in accordance with BS 7671, detailing the work, should be given by the installer to the customer.
The certificate should state in the noncompliances section that lighting circuits nos. xxx do not have protective conductors and that the installation of the consumer unit has been carried out in accordance with the recommendations in this Best Practice Guide.
The installer should state on the certificate that a full periodic inspection and test of the complete installation has not been carried out.
A strong recommendation that the installation has a full periodic inspection and test as a matter of urgency should be made to the customer.
• Ascertain consumer unit requirements
• Ascertain adequacy of existing earthing and bonding arrangements
• Identify any circuits without circuit protective conductors
• Determine whether the customer will agree to the installation of circuit protective conductors.
If the customer will not agree to the installation of circuit protective conductors:
• Carry out a risk assessment including inspection and testing
• Replace metal fittings and accessories, or separately earth metal fittings
• Fit a warning notice as necessary
• Issue an electrical installation certificate, detailing non-compliances if any
• Advise the customer in writing of any risks remaining on completion of the work.
Guidance on the management ofelectrical safetyand safe isolation procedures for low voltage installations
This Guide explains what needs to be done to make sure workers on site are not exposed to danger when working on or near live electrical systems and equipment in buildings, particularly in the final stages of construction.
Every year, people working on construction sites and on refurbishment and maintenance activities suffer electric shock and burn injuries some of which, tragically, are fatal. Electrical contractors should be aware that many of these accidents are a direct consequence of electricians not implementing safe isolation procedures on low voltage installations (that is, those operating at up to 1000 V a.c. or 1500 V d.c.).
An example of one such fatal incident is given below.
Experience shows that electricians employed by electrical contractors are particularly at risk of death or serious injury from electric shock or burns if they fail to follow safe working procedures. To achieve compliance with the legislation explained in this Guide, electrical contractors should not allow or condone dangerous work practices and should arrange for the safe working practices explained in the Guide to be implemented diligently.
Whereas this Guide is aimed primarily at electrical contractors and their employees, principal contractors and non-electrical subcontractors have a significant role in managing electrical risks during construction and refurbishment projects. Principal contractors and their non-electrical subcontractors should make themselves familiar with this Guide to ensure, firstly, that they do not place electrical contractors under pressure to implement unsafe practices; and, secondly, that they understand how their own employees may achieve safety from electrical risks.
The Health and Safety at Work etc. Act 1974sets out the general health and safety duties of employers, employees and the selfemployed. The Electricity at Work Regulations 1989, which were made under the Act, require precautions to be taken against the risk of death or personal injury from electricity in work activities.
Duties are placed on employers to ensure, amongst other things, that employees engaged in such work activities on or near electrical equipment* implement safe systems of work, have the technical knowledge, training or experience to carry out the work safely, and are provided with suitable tools, test equipment and personal protective equipment appropriate to the work they are required to carry out.
Under the Health and Safety at Work etc Act, employees are required to co-operate with their employer to enable the requirements of the regulations to be met. This includes complying with any instructions given on matters such as safe systems of work. The Electricity at Work Regulations 1989require that employees themselves comply with the regulations.
The Management of Health and Safety at Work Regulations 1999require employers to make a suitable and sufficient assessment of the risks to the health and safety both of their employees and of other persons arising out of, or in connection with, the conduct of their undertakings. Where five or more persons are employed, the employer must record the significant findings of these risk assessments.
Generic guidance on safe working practices for work on electrical equipment is published by the Health and Safety Executive (HSE) in its guidance note entitled Electricity at Work – Safe Working Practices(HSG85).
It provides information on dead and live working and on isolation procedures when working on both Low Voltage (LV) and High Voltage (HV) systems. This Guide covers LV systems only and is targeted at the work of electrical contractors, particularly in the construction sector. Extra precautions need to be taken when working with HV equipment and circuits, and reference should be made to the detailed guidance provided in HSG85 in such circumstances.
The Memorandum of guidance on the Electricity at Work Regulations 1989HSR25 is intended to help duty holders meet the requirements of the regulations. It will be of interest and practical help primarily to engineers, technicians and their managers (including those involved in the design, construction, operation or maintenance of electrical systems and equipment).
It sets out the regulations and gives technical and legal guidance on the regulations. Its purpose is to amplify the nature of the precautions in general terms so as to help in the achievement of high standards of electrical safety in compliance with the duties imposed.
In the context of risks arising from live work, regulation 14 of the Electricity at Work Regulations 1989requires that:
No person shall be engaged in any work activity on or so near any live conductor (other than one suitably covered with insulating material so as to prevent danger) that danger may arise unless –
(a) it is unreasonable in all the circumstances for it to be dead; and
(b) it is reasonable in all the circumstances for him to be at work on or near it while it is live; and
(c) suitable precautions (including where necessary the provision of suitable protective equipment) are taken to prevent injury.
It should be noted that all three conditions must be met in order for work on or near live conductors to be carried out.
To comply with regulation 14 of the Electricity at Work Regulations 1989 (work on or near live conductors), dead working should be the normal method of carrying out work on electrical equipment and circuits.
Live working, which includes not only working on live uninsulated conductors but also working so near live uninsulated conductors that there is a risk of injury, should only be carried out in circumstances where it is unreasonable to work dead.
Typically this would include some types of fault finding and testing (including the live testing requirements of BS 7671 – Requirements for Electrical Installations (IET Wiring Regulations)), but only where the risks are acceptable and where suitable precautions are taken against injury, including the provision of adequate training and personal protective equipment (PPE).
Pressure to carry out live work is common in areas such as construction sites, high cost manufacturing and in retail outlets operating twenty-four hours per day, seven days a week.
Irrespective of these pressures, the requirements of the regulations still apply in such situations and live working should only be carried out when justified using the criteria explained in HSG85.
For systems where the supply has been cut off to allow dead working, regulation 13 of the Electricity at Work Regulations 1989applies as follows:
Adequate precautions shall be taken to prevent electrical equipment, which has been made dead in order to prevent danger while work is carried out on or near that equipment, from becoming electrically charged during that work if danger may thereby arise.
This regulation therefore requires that adequate precautions are taken to ensure that conductors and equipment cannot inadvertently be energised while the work is taking place – this is the process of isolation.
The Electricity at Work Regulations 1989definition of ‘isolation’is given in regulation 12 and means the disconnection and separation of the electrical equipment from every source of electrical energyin such a way that this disconnection and separation is secure.
In effect this means not just cutting off the supply but also ensuring that the means of disconnection is secure, as described in this Guide. In most instances this will require securing the means of disconnection in the OFF position and it is highly recommended that a caution notice or label is posted at the point of disconnection as described in the Guide under ‘Safe isolation procedures’.
Of equal importance is regulation 16. This requires that employers ensure that all employees involved in work on electrical equipment are competent.
Employees should be instructed on, and trained in, the implementation of safe systems of work. If they have not received such training and instruction, they should only work under the supervision of a competent person.
Site safety management
It is essential from the outset that effective management and control of the working practices on electrical systems and equipment, particularly in relation to safe isolation procedures, are established and maintained.
It should be noted that although this Guide is mainly aimed at construction sites, the general principles of management and control also apply to all electrical installation work including refurbishment and maintenance activities.
Directors and managers of companies employing electrical operatives should ensure that their requirements for safe working practices are clearly explained in company-specific electrical safety policy documents including site-specific risk assessments and method statements.
Guidance on how to carry out risk assessments and the form they should take is published by the HSE on its website at www.hse.gov.uk/risk/index.htm
All operatives should be shown these documents and have the contents including their responsibilities clearly explained. This can be done during site inductions and/or regular tool-box talks.
Managers should ensure that operatives understand the information regarding safe working practices, particularly where they may not have a good command of English.
It is very important for managers to ensure that these safety management documents are regularly reviewed. They should be updated as required if and when the risks change significantly, particularly during the period of a specific contract.
Directors and managers are expected to involve themselves and show visible and positive leadership, in the management of every aspect of health and safety on their sites.
Guidance on the roles and responsibilities of directors and managers is given in guidance leaflet Leading Health and Safety at Work(INDG417). This is a joint publication of the Institute of Directors and HSE, It is available at www.hse.gov.uk/leadership
Managers should also ensure that their operatives are provided with all the tools, suitable test equipment, personal protective equipment, locking clips, padlocks, keys and caution and danger notices identified in their risk assessments and method statements.
The Scottish Joint Industry Board (SJIB) handbook National Working Rule C2.4requires operatives to provide particular tools and test equipment, including a proprietary test lamp or voltage detector (see Scottish JIB website www.sjib.org.uk/nationalworking-rules).
The same rule requires employers to carry out periodic tool kit inspections to ensure that their employees are in possession of all the items listed in the handbook and they are of suitable quality and in good repair.
For projects where work is being carried out in the presence of other trades, and sites involving more than one electrical operative, it is essential that a suitably experienced and competent person is appointed to oversee the work on site during the construction of the electrical installation.
This appointed person’s responsibilities should include the overseeing of the working practices of the operative(s) to ensure that they consistently and diligently follow the practices set out in the risk assessments and method statements.
They may also be given responsibility for controlling the work of appointed sub-contractors, who must provide appropriate method statements and risk assessments for their work.
The appointed person or manager may delegate (in writing) control of specific tasks and procedures to other competent persons who have appropriate training and competence in the performance of these tasks and procedures.
On construction projects, once the electrical installation is nearing completion, ready for inspection and testing, and certainly before energising switchgear, suitable doors should be fitted to all switch-rooms and riser entrances, and heavy duty locks or padlocks fitted accordingly.
Access to these areas should be controlled and restricted to competent persons or persons who are under supervision in accordance with the site electrical safe systems of work.
The access doors should be locked when electrical operatives are not working in these areas and danger notices warning of any live services present posted at all times. Plant and materials should not be stored in locked electrical switch-rooms or electrical risers.
It is always preferable to avoid energising any outgoing electrical distribution services until the distribution switchgear and all connected circuits are complete and have been inspected and dead-tested in accordance with the requirements of BS 7671.
The inclusion of clauses within contracts regarding stage payments to contractors initiated by energising parts of an installation should be discouraged as they may encourage the contractors to energise prematurely due to financial pressures.
If live services are required by others before all installation work and inspection and testing associated with the relevant distribution boards have been fully completed, and this cannot be resisted, distribution boards and circuits should not be energised unless the electrical contractor has a written request from the principal contractor or the principal contractor’s agent, and the electrical contractor agrees it is safe to do so.
In such cases, and before use of any distribution board or circuit, the following should be implemented:
• Blanking plates must be fitted in unused ways of the affected distribution boards, covers fitted and circuit schedules marked up to show the precise status of the installation; and
• Managers should review their risk assessments and method statements and update them as necessary to reflect the changed circumstances. Any changes to working practices should be brought to the attention of the operatives and any other workers at the site who may be affected; and
• No circuit should be made available for use until it has been fully completed and inspected and tested in accordance with BS 7671 including checks to ensure that earthing arrangements and protective conductors (including main protective bonding conductors) are in place; and
• Any circuit that is incomplete or has yet to be fully inspected and tested must remain securely isolated at the supply end.
All workers, supervisors and managers on construction sites should be made aware that it is not considered reasonable to work on or near uninsulated live conductors solely on the grounds of convenience, or of saving time or cost. When live services are provided prior to final commissioning and handover, in order to make sure that everyone working on site is aware of any live circuits in an area, danger notices should be displayed on the following items:
• Energised main and sub-main switchgear and distribution boards
• Energised plant
• Exposed cables which are liable to be damaged by other trades or the environmental conditions.
People entering completed and energised areas working under instructions from the principal contractor or client’s representative must be made aware of the extent of the live services within the respective areas by the electrical contractor, principal contractor or client’s representative. They should assume that all services within such areas are energised.
The electrical contractor must inform the principal contractor when they intend to complete and energise the electrical installation in an area. The principal contractor must then ensure that the client’s representative and all persons on site are informed that the electrical installation in that area has been energised.
All contractors should advise their employees of this fact at appropriate site inductions and toolbox talks.
Safe isolation procedures
For all work on LV electrical equipment or circuits, it is important to ensure that the correct point of isolation is identified, that an appropriate means of isolation is used, and that the supply cannot inadvertently be reinstated while the work is in progress. The conductors must be proved to be dead at the point of work before they are touched and where necessary caution notices should also be applied at the point(s) of isolation.
In the interests of avoiding inadvertent energisation, a good principle to adopt is that the point of isolation should be under the control of the person who is carrying out the work on the isolated conductors.
If alternative means of controlling the security of the isolation are adopted, such as the point of isolation being kept under the control of an appointed (authorised) person, these means should be equally effective at preventing inadvertent reinstatement of the supply.
The means of isolation can be an adjacent local isolation device such as a plug and socket-outlet, fused connection unit, switch-disconnector, circuitbreaker, fuse etc, as appropriate, which is under the direct control of the competent person carrying out the work.
When isolating the main source of energy, it is also essential to isolate any secondary sources (such as standby generators, uninterruptible power supplies and microgenerators).
A comprehensive list of devices that can be used for isolation is given in Table 53.4 of BS 7671: 2008, as amended which is reproduced in Annex 1 of this guide.
These devices can be used without further precautions provided there is no foreseeable risk that the supply could be reinstated by others prior to the work being completed by the competent person.
Circuit-breakers conforming to BS EN 60898 are suitable for isolation and may be marked with the following symbol:
However, miniature circuit-breakers (MCBs) manufactured to earlier standards (such as BS 3871) are unlikely to be suitable for isolation.
Switchgear conforming to BS EN 60947-3 and circuit-breakers and RCDs conforming to BS EN 60947-2 are suitable for isolation if marked with the symbol shown above.
See Annex 1 for further guidance on the identification of devices suitable for isolation.
Where there is no such local means of isolation or where there is a risk of reinstatement of the supply, the circuit or equipment to be worked on should be securely isolated by one of the following methods:
Isolation using a main switch or distribution board switch disconnector.
Isolation of equipment or circuits using the main switch or distribution board switch-disconnector is the preferred method. The point of isolation should be locked off using a unique key or combination retained by the person carrying out the work or the appointed person, and a caution notice attached to the point of isolation.
Where more than one operative is working on circuits supplied from an isolated distribution board, a multi-lock hasp can be used to prevent operation of the main isolator until such time that all persons working on the installation have completed their work and removed their padlocks from the hasp.
If locking-off facilities are not provided on the relevant switch, then a locked distribution board which prevents access to the switch-disconnector is acceptable provided the key or combination is unique and is retained by the person doing the work or the appointed person.
Again, multi-lock hasps can be used to control the isolation where more than one person is working on the installation. An alternative to a multi-lock hasp is a key box or similar system which provides effective control of access to the key for the point of isolation.
Isolation of individual circuits
Where it is intended that more than one person will be working on circuits supplied from a distribution board (that is, multiple isolations) and a multi-lock hasp cannot be used to secure the main switchdisconnector or the distribution board has to remain energised to supply other circuits, each circuit supplied from the distribution board on which work is to be carried out should be isolated by one or more of the following methods to prevent inadvertent reinstatement of the supply.
The principle is that each person carrying out such work should have control of their own point(s) of isolation and not rely on others, except an appointed person, to prevent deliberate or inadvertent energisation.
It is preferable that a final circuit distribution board is not energised until all of its final circuits have been completed, and inspected and tested.
It is also preferable for an appropriate locking-off device to be used at the point(s) of isolation. However, if any items required for carrying out the procedures recommended below are not manufactured for the distribution board in question or cannot be obtained through retail/trade outlets, it is acceptable to disconnect the circuit from the distribution board provided the disconnected conductors are made safe by being coiled and the conductors insulated or otherwise protected against inadvertent re-energisation.
Suitable labelling of the disconnected conductors using a caution notice is vital to prevent the supply being reinstated, particularly if other electricians are present.
Work carried out inside a live distribution board, such as disconnecting a circuit for isolation, is classed as live working when there is access to exposed live conductors. In this case, the appropriate precautions should be taken as described in HSG85 with respect to regulation 14 of the Electricity at Work Regulations.
1. Isolation of individual circuits protected by circuit-breakers
Where suitable circuit-breakers are used as the means of isolation, the relevant device should be locked-off using an appropriate locking-off clip with a padlock which can be opened only by a unique key or combination. The key or combination should be retained by the person carrying out the work or the appointed person. A caution notice should be attached at the point of isolation.
The practice of placing insulating tape over a circuit-breaker to prevent inadvertent switch-on is not an adequate or acceptable means of securing the device in the OFF position. Such unsafe practice will not achieve compliance with the Electricity at Work Regulations 1989.
Note: Some distribution boards are manufactured with ‘slider switches’ to disconnect the circuit from the live side of the circuit breaker. These devices should not be relied upon as the only means of isolation for circuits, as they do not meet the requirements for isolation and the wrong switch could easily be operated on completion of the work.
2. Isolation of individual circuits protected by fuses
Where fuses are used, the removal of the fuse is an acceptable means of disconnecting the supply to an individual circuit for the purpose of isolation.
To prevent the fuse being replaced by others, the fuse should be retained by the person carrying out the work, and a lockable fuse insert with a padlock should be fitted to achieve secure isolation. A caution notice should be attached at the point of isolation.
Where lockable fuse inserts are not available, the following must be considered:
• Where removal of the fuse exposes live terminals that can be touched, a dummy fuse (that is a fuse carrier which is not fitted with a fuse link and which is clearly marked or coloured to make it conspicuous) should be inserted in the fuse way to cover live parts. When this is not possible, the incoming supply to the fuse will need to be isolated
• A caution notice should be attached to deter inadvertent replacement of a spare fuse
• In addition, if possible, the fuseboard door or cover should be locked to prevent access as advised above under ‘Isolation using a main switch or distribution board switchdisconnector’.
Temporary disconnection of the incoming supply
For some types of work on existing installations, such as the replacement of main switchgear and consumer units, it is necessary for the distributor’s service fuses to be withdrawn in order to disconnect the incoming supply for the purpose of isolation.
Legally, service fuses can be withdrawn only by the electricity supplier or distributor, or by those they have expressly authorised to carry out such work.
Note: In TT systems, the incoming neutral conductor cannot reliably be regarded as being at Earth potential. This means that for TT supplies, a multi-pole switching device which disconnects the line and neutral conductors must be used as the means of isolation. For similar reasons, in IT systems, all poles of the supply must be disconnected.
In these circumstances, single pole isolation, such as by fuses or single-pole circuit-breakers, is not acceptable.
An electrical permit-to-work must be used for work on HV systems that have been made dead, and can be useful in certain situations for LV work, such as where there is more than one source of supply. These permits are primarily a statement that a circuit or item of equipment is isolated and has been made safe to work on. They must not be used for live working as this can cause confusion.
Details on the use of these permits, including an example form, are given in HSG85.
In allinstances where there is anyrisk that the supply could be reinstated, an appropriate warning/caution notice should be placed at the point of isolation. For distribution boards with ‘multiple isolations’, a single suitably worded notice on each distribution board, such as the example shown below, would suffice:
Example of a warning notice
Proving dead isolated equipment or circuits
It is important to ensure that the correct point of isolation is identified before proving dead.
Where possible and safe to do so, this may include testing with the isolating device first in the ON position and then in the OFF position to establish that the equipment or circuit is under the control of that device.
Following isolation of equipment or circuits and beforestarting work it should be provedthat the parts to be worked on, and those nearby, are dead.
It should never be assumed that equipment is dead because a particular isolation device has been placed in the OFF position.
The procedure for proving dead should be by use of a proprietary test lamp or two-pole voltage detector as recommended in HSE Guidance Note GS38,
The use of multimeters, makeshift devices and noncontact voltage indicators (voltage sticks) is not advised for voltage detection as such use has caused accidents.
The test lamp or voltage detector should be proved to be working before and after use. This should be achieved preferably by the use of a proprietary proving unit or in built self test facility rather than by accessing live terminals. All line, neutral and protective conductors of the circuit should be tested and proved to be dead.
Electricians who regularly work on installations that have been energised should be equipped with devices for proving that conductors are dead.
Electricians who may occasionally work on installations that have been energised should have ready access to devices for proving conductors dead.
New installations can be a particular hazard as some of the circuits or equipment may need to be modified after the installation has been energised. It is therefore important that every protective device is correctly identified at each distribution board before any energising takes place, and safe isolation procedures, such as locking-off circuit breakers as described above, are adopted, particularly where a number of electricians are working on the same installation.
Alterations and additions
Alterations and additions to existing installations can also be particularly hazardous. Records including circuit identification may not be available, or may be inadequate or incorrect. It is therefore particularly important to ensure that circuits to be worked on have been correctly identified for isolation purposes prior to work commencing.
Circuits under automatic control
It is particularly important to correctly identify circuits for isolation purposes if they are under automatic control, such as by time switch or photocell. Deaths and injuries have occurred where circuits have been proved to be dead at the point of work before work commenced, only for the circuits to be energised unexpectedly by automatic controls as work was underway.
Care should be taken when working on neutral conductors of circuits, particularly where single-pole isolation is used. The practice of ‘borrowing’ neutrals, that is using the neutral of one circuit as the neutral for another circuit, is not permitted by BS 7671. This dangerous practice, however, is not uncommon.
Lighting and control circuits are the most common examples of where this practice is found. In these circumstances, the neutral conductor can become live when it is disconnected, if an energised load on another circuit is connected to it.
It is also difficult to identify specific neutral conductors in ‘bunches’ of single core cables, such as where enclosed in trunking or conduit, and care should be taken when severing such cables that the correct conductor has been identified.
If doubt exists, live working measures, such as the use of eye protection, electricians’ insulating gloves and insulated tools, should be employed until the circuit has been proved to be dead.
Protective conductors Protective conductors of circuits having high protective conductor currents are effectively live, and should be treated with caution. Significant protective conductor currents can be present in both power and lighting circuits.
Proving dead unused or unidentified cables
Where there is uncertainty regarding isolation when removing unidentified cables or proving dead an ‘unused’ cable, particularly where insufficient conductor is exposed to enable the use of test probes, those conductors should be assumed to be live until positively proven to be dead, and any work carried out on them should employ live working practices until the conductors are proved to be dead, and isolated.
If the cable cores are accessible, a clamp meter can be used as a means of identifying a cable by testing for current flow in the conductors. If the cores are not accessible, cable detection equipment may be used in conjunction with a signal generator.
Non-contact voltage indicators (voltage sticks) can also be useful in these situations to make a preliminary test for voltage where cables without a metallic sheath are to be identified.
If a non-contact indicator shows a cable to be live, it may be assumed to be so. However, if it does not, the cable must not be assumed to be dead.
Once insulation is removed using live working practices to reveal the underlying conductors, contactvoltage detectors should be used as the means of proving that the conductors are dead.
Electrical safety First has developed a safe isolation App for smartphones and handheld devices based on the content of this Guide. For further information on this App and details of how to download it visit www.electricalsafetyfirst.org.uk/electricalprofessionals/safe-isolation-app
Connecting a microgeneration system to a domestic or similar electrical installation (in parallel with the mains supply)
The aims of this Guide are:
• to provide an overview of microgeneration intended to produce electrical energy, otherwise known as small-scale embedded generation (SSEG),
• to provide information on the legal and contractual issues relating specifically to the installation of microgenerators with electrical rating up to 16 A per phase (including the relationship of the consumer with the electricity supplier and the distribution network operator (DNO)), and
• to give guidance on the particular electrical issues, including electrical safety issues, that arise when installing or connecting a microgenerator.
The Guide takes into account the publication of Amendment 1 to BS 7671: 2008.
The Guide does not provide installation guidance specific to any particular types of microgeneration. BS 7671: 2008 Section 712 contains particular requirements for photovoltaic installations, as does DTI Publication URN 06/1972*, Photovoltaics in Buildings, Guide to the installation of PV systems (2nd Edition), dated 2006. For any microgenerator installation, the instructions of the manufacturer or supplier should be followed.
The Guide does not provide installation guidance where it is intended to install more than one microgenerator. In such cases it is necessary to consider the possibility of interaction between the protection and control equipment of the microgenerators, and the specific advice of the manufacturers or suppliers of each of the microgenerators should be obtained and followed.
Where multiple microgeneration installations are to be installed in a close geographical region (such as in a housing development), it is also necessary to obtain the permission of the DNO in advance.
A ‘route map’ for getting a generation scheme connected to the distribution network can be found in the Energy Networks Association’s
(It should be noted that Engineering Recommendation G83/1-1, referred to in the above ENA Guide, applies also to single microgeneration installations.)
The Guide does not cover Feed-in Tariffs in detail. On 1 April 2010 the Government launched Feed-in Tariffs (FITs), which are payments to microgenerators based on both what they generate, and what they export to the grid if they choose to do so. More information on FITs is available from
To be FIT-eligible, electricity-led microgenerator installations with a Declared Net Capacity of 50 kW or less must conform to the Microgeneration Certification Scheme (MCS). Other schemes may in future be approved as being equivalent.
An MCS installation is one in respect of which both the equipment being used and the installation company have been certificated by a UKASaccredited Certification Body. The product will have been tested against performance, quality and safety standards before being certificated.
For an installation company to become certificated, a Certification Body will assess its technical competence, as well as checking that it has appropriate business processes (such as quality standards, complaints handling procedures etc). The installation company must also be party to an Office of Fair Trading-approved Consumer Code of Conduct.
More information on becoming an MCS installer, and on what equipment is currently approved under the scheme, is available from www.microgenerationcertification.org
The UK Government is committed to encourage the wider use of renewable energy generation, and to technologies such as combined heat and power (CHP) that offer improved efficiency compared to traditional bulk generation in large power stations. This commitment reflects undertakings made with the UK’s partners in the European Union and internationally to reduce greenhouse gas emissions and reliance on fossil fuels.
Generation of electricity closer to the point of use avoids some of the losses that arise in the transmission and distribution of electricity to consumers. This currently amounts to up to 10% of units dispatched. Even for the most modern combined cycle gas generating stations with production efficiencies of 50-60%, the efficiency from the point of generation up to the point of use in a consumer’s installation is generally well below 50%.
Decentralised generation, if sufficiently widely adopted, could also improve the reliability and resilience of the electricity supply system, though this clearly depends on the types and relative amounts of generation that are installed. For example, photovoltaic systems do not generate at night, and wind power does not function at very low or very high wind speeds.
Types of generation
It is, of course, possible to install and operate a generator and installation completely independently of the normal mains supply and to run certain appliances entirely on this separate system. This Guide, however, considers only generators that are intended to work in parallel with an existing mains supply, as this represents the most practical approach for most consumers.
The assumption is that consumers generally will wish to continue to use electricity as and when required at the throw of a switch, without needing to be aware as to whether the generator is working or not.
Currently, the options can be divided into two broad classes from the point of view of connection into an existing installation: • Renewable sources of electricity, powered by wind, light or hydro-power, or fuel cells. Many of these generate at d.c. and are connected to the mains through a d.c. to a.c. inverter
• Gas, oil and biomass fired micro-cogeneration (combined heat and power (CHP)) systems. The primary function of these systems is to provide for heating and hot water needs, in place of a traditional boiler or water heater. However, they include a small generator that provides electricity, powered by some of the heat energy produced for the water heating process. This Guide does not give guidance on the heat production aspects of microgenerators. Renewable sources of heat using solar thermal panels, ground or air source heat pumps or biomass boilers that do not generate electricity are not covered by this Guide.
As previously mentioned, microgenerators are generally characterised as having an output of no more than 16 A per phase. In the case of microcogeneration (CHP) systems, because the electricity generation is ancillary to the heating of water and so represents only a part of the output of the system, the electrical output is typically in the range of 4 to 6 A.
Legal and related issues
When at work, even in domestic premises, an electrical installer is subject to relevant Health and Safety legislation, including the Electricity at Work Regulations.
Installers of microgenerators will need to be aware of the requirements of the relevant Building Regulations. In domestic premises in England and Wales, the installation of a microgenerator is notifiable under Part P. In Scotland, a Building Warrant may be required (further information is available at www.scotland.gov.uk/Topics/BuiltEnvironment/Building/Building-standards).
Some forms of microgenerator may be subject to planning law and to the non-electrical aspects of the Building Regulations, in particular structural considerations.
Although an electrical installer might not be involved in such issues on behalf of his client, they may impact on an unwary electrical installer in carrying out his work.
Therefore, before commencing work, it is advisable to consider the issues covered below.
The installation of renewable energy sources often requires Planning permission. Therefore whether the proposed work is subject to these requirements or is considered ‘permitted development’ should be determined before the work commences. This is undertaken by contacting the local Planning Authority, who, should Planning permission be required, will indicate what information they require to be provided with the Planning application.
In England and Wales, the relevant Building Regulations will normally apply to work in the domestic situation. Depending on the nature of this work, these regulations may cover electrical installations, various structural implications (such as the ability of the existing building to carry the additional load or forces produced at the fixing points) and damp penetration issues, as appropriate. Compliance is achieved either through the appropriate ‘Competent Person Scheme’ or by applying to a building control body, such as the Local Authority Building Control.
• Before fixing microgeneration equipment to a building, consideration should be given by the installer to the structural condition of the building. This may involve a structural survey. • In Scotland, a Building Warrant may be required. • Hydro turbines may require planning consent and will also require a water abstraction licence.
The Electricity Safety, Quality and Continuity Regulations 2002 contain, in regulation 22, requirements for the installation and operation of generators in parallel with the distributor’s network. These generally prohibit the connection of a generator without prior consent of the distributor (typically the relevant regional distribution network operator (DNO)), and contain requirements concerning design and operation that are likely to prevent parallel operation of generators in domestic premises.
However, an exemption is given in regulation 22(2) for the installation of generation rated up to a total of 16 A per phase, provided: • it has protection that will disconnect from the mains supply automatically in the event of the loss of the mains supply • the installation complies with the edition of BS 7671 (Requirements for Electrical Installations) current at the time of installation, and • the installer notifies the DNO before or at the time of commissioning the microgenerator.
Details of the general requirements for connecting an SSEG and the characteristics for the protection scheme necessary to provide automatic disconnection following loss of mains or variation of voltage or frequency from the declared values are contained in the Energy Networks Association’s Engineering Recommendation G83 (version G83/1-1†) and in BS EN 50438. The installer should refer to the manufacturer’s documentation to confirm that the microgenerator complies with the relevant requirements of G83 or BS EN 50438.
Details of the requirements for notifying the DNO before the time of commissioning the microgenerator are contained in G83 and in BS EN 50438. In addition to notifying the DNO before or at the time of commissioning a microgenerator, the installer must provide the DNO with an Installation Commissioning Confirmation Form, a copy of the circuit diagram showing the circuit wiring, and the manufacturer’s Verification Test Report, all within 30 days of the microgenerator being commissioned (clause 5.1.1 of G83/1-1† and clause 7.3.1 of BS EN 50438: 2007 refer).
Where generation exceeding 16 A output in total is to be provided in a single installation, or where multiple microgeneration installations are to be installed in a close geographical region (such as in a housing development), it is necessary to obtain the permission of the DNO in advance.
Contract with the electricity supplier
Generators rated at up to 50 MW are exempted from licensing under the Utilities Act, so microgenerators covered by this Guide are exempt.
Energy users will have a contract with an electricity supplier for the purchase of electricity. Invariably the supply is provided through a meter. The meter will be either a prepayment meter (the customer pays in advance with cash or tokens) or a credit meter (the meter is read and the customer is billed retrospectively). In either case, the contract is for the supply of electricity to the premises.
If at any time the consumer's microgenerator generates more electrical power than is being used in the premises, the surplus will go into the electricity network.
The exporting of energy from the premises in this way will only be covered by the consumer’s contract with the electricity supplier if a specific written agreement to that effect has been entered into by the consumer with the supplier, as will be the case if the customer applies to that supplier for the payment of Feed-in Tariffs.
Where this is the case, the electricity supplier may arrange for an export meter to be installed at the premises. However, where the installed capacity of the generator is less than 30 kW, the supplier may defer doing this until smart meters are rolled out.
In the absence of an export meter, the amount of energy exported will be deemed to be a percentage of the energy generated by the microgenerator. The energy generated will be ascertained from the generation meter, which forms part of the microgeneration installation. The fixed display unit of the generation meter must be installed in an accessible location.
The existing meter at the premises (the import meter) may not require replacement until smart meters are rolled out. However, the electricity supplier is likely to arrange for this meter to be replaced if it does not have a ‘backstop’ to prevent the energy register from running backwards during export, which would lead to double counting of exported energy.
In the unlikely circumstances that an agreement and the associated metering equipment are not in place for the export of electrical energy from the premises, the reverse flow of energy can have an impact on the supplier’s electricity meter at the premises in one of the following ways:
• Where the meter is fitted with a backstop to prevent the energy register from running backwards, the consumer will receive no compensation for exported energy.
• Some meters with a backstop have a flag that is tripped by reverse power flow, which could result in the consumer being accused of stealing energy.
• A prepayment meter may have an internal contactor that cuts off the mains supply if the energy flow is reversed. Some older meters do not have a backstop and the register will run backwards while energy is being exported, effectively ‘crediting’ the consumer with energy at the rate at which they normally pay for the electricity. This could be treated by the electricity supplier as a form of theft.
Installing a microgenerator brings particular additional electrical safety concerns, which include the following:
• Persons must be warned that the electrical installation includes a microgenerator so that precautions can be taken to avoid the risk of electric shock. Both the mains supply and the microgenerator must be securely isolated before electrical work is performed on any part of the installation.
• Adequate labelling must be provided to warn that the installation includes another source of energy. Suitable labelling is suggested in G83 and, for photovoltaic systems, in DTI Publication URN 06/1972*, Photovoltaics in Buildings, Guide to the installation of PV systems (2nd Edition), dated 2006.
• It must be remembered that wind turbines are likely to produce an output whenever they are turning and PV cells will produce an output whenever they are exposed to light. Additional precautions, such as restraining the turbine from turning or adopting the means given in DTI Publication URN 06/1972* to improve safety on the d.c. side of a PV system, will be necessary when working on those parts of the circuit close to the source of energy and upstream of the means of isolation.
In some respects, microgenerators can be considered to be similar to any current-using equipment. For example:
• live parts will invariably be insulated or have an earthed or insulating enclosure
• the metallic enclosure of a Class I microgenerator will need to be connected to the circuit protective conductor.
However, there are other aspects that require care to ensure that the existing level of electrical safety is maintained for the users following the installation of a microgenerator.
As mentioned previously, the exemption to the requirement for prior consent of the DNO, contained in Regulation 22(2) of the Electricity Safety, Quality and Continuity Regulations 2002, requires compliance with BS 7671 (DTI Publication reference - URN 02/1544, which gives guidance on the Electricity Safety, Quality and Continuity Regulations 2002, refers). Prior to commencing the installation of a microgenerator, the installer must confirm such compliance, for example, by examining a recent Electrical Installation Condition Report (Periodic Inspection Report) for the existing installation (if available), or by carrying out a Periodic Inspection.
In order for a microgenerator to be placed on the market, the manufacturer or supplier of the microgenerator is required to declare compliance with the Electrical Equipment (Safety) Regulations and the Electromagnetic Compatibility Regulations. The components of the microgenerator will be CE marked to confirm this. Also, for an MCS compliant installation, it is a requirement that the equipment being used has been certificated by a UKASaccredited Certification Body where applicable (such as for the modules of a PV system). Inverters do not require such certification.
Compliance with these requirements should ensure that the microgenerator will be satisfactory in an installation in terms of the power factor, generation of harmonics, and voltage disturbances arising from starting current and synchronisation.
Any synchronising system should be automatic and of a type that considers frequency, phase and voltage magnitude. The microgenerator should also have documentation confirming, amongst other things, the acceptability of the means of protection against operation in the event of loss of the mains supply, as required by G83 or BS EN 50438.
In designing a connection for a microgenerator, the electrical installer has to consider all the issues that would need to be covered for a conventional final circuit, including:
• the maximum demand (and the generator output) • the type of earthing arrangement
• the nature of the supply
• external influences
• compatibility, maintainability and accessibility
• protection against electric shock
• protection against thermal effects
• protection against overcurrent
• isolation and switching
• equipment selection and installation issues.
The electrical installer will recognise that some of these issues can be changed by the connection of a microgenerator to an existing installation.
It is unlikely with the size of microgenerators covered by this Guide that the prospective fault current would change sufficiently to exceed the fault rating of existing protective devices, but this should be confirmed.
From the specific perspective of a microgenerator, except for a PV system (see below), there are two connection options:
• connection into a separate dedicated circuit
• connection into an existing final circuit. For a solar photovoltaic (PV) power supply system (including a PV microgeneration installation), the second option – connection into an existing final circuit – is not permitted by Regulation 712.4220.127.116.11.1 of BS 7671 or by clause 4.2 of Microgeneration Installation Standard: MIS 3002, and the generator must therefore be connected into a separate dedicated circuit.
Examples of the two options are shown diagrammatically in Fig 1.
Given the perceived constraint of financial viability on the development of the market for microgenerators, the second of these options has been considered by some product developers to offer a simple solution with minimal disruption to the consumer’s property.
From the perspective of the electrical safety of the installation, however, this option can create design limitations for the installer of the microgenerator, and limitations for the user of the installation.
Connection into a dedicated circuit is preferred.
This option is technically simpler and creates least impact on existing use and hence on the user of the installation. The cost implication may not be significant when compared to the cost of the generator itself, and in some cases it may be less expensive in view of the need to meet the technical requirements detailed below for connecting into an existing final circuit.
Whichever of the two options is chosen, it is imperative that the safety of the electrical installation is not impaired by the installation of the microgenerator.
The essential criteria that must be met are given below for both options. In either case the following requirements must be met:
(i) The winding of an a.c. microgenerator must not be earthed (clause 6.4 of G83/1-1† and clause 4.1.3 of BS EN 50438: 2007 refer). The reason for this precaution is to avoid damage to the generator during faults on the distribution network and to ensure correct operation of protective devices. Note.A d.c. source or d.c. microgenerator could be earthed provided the inverter separates the a.c. and d.c. sides by at least the equivalent of a transformer providing simple separation. Such earthing, which may be necessary for functional purposes in some cases, requires special consideration and is beyond the scope of this Guide. † G83/1-1 is expected to be superseded by a revised version (G83/2), containing material changes, during late 2011 or early 2012.
(ii) Means must be provided to automatically disconnect the microgenerator from the mains supply in the event of loss of that supply or deviation of the voltage or frequency at the supply terminals from the declared values. If the microgeneration installation includes a static inverter, the means must be on the load side of the inverter. (Regulation 551.7.4 of BS 7671 refers.) Note.The required protection settings are given in G83 and in Annex A of BS EN 50438.
(iii) Means must also be provided to prevent the connection of the microgenerator to the mains supply in the event of loss of that supply or deviation of the voltage or frequency at the supply terminals from the declared values (Regulation 551.7.5 of BS 7671 refers). Note. The requirements are given in G83 and in BS EN 50438. Amongst other things, it is required that feeding power to the distribution network will only commence after the voltage and frequency on the distribution network have been within the limits of the interface protection settings for a minimum of 3 minutes for mechanical a.c. generation or 20 s for inverter based systems.
(iv) Where a microgenerator having a d.c. source does not incorporate the equivalent of a transformer providing at least simple separation between the d.c. and a.c. sides, an RCD installed for fault protection by automatic disconnection of supply or for additional protection (I∆n <_30 mA) must be of a type that will operate as intended in the presence of d.c. components in the residual current. (This does not apply where it has been established – such as from a specific written statement given by the inverter manufacturer – that the inverter provides galvanic isolation between the d.c. and a.c. sides that prevents it from feeding d.c. current into the electrical installation.)
Note: A Type AC RCD will not fulfil the above requirement. Depending on the level and form of d.c. components, an RCD (where required) will need to be of Type A to BS EN 61008 or BS EN 61009, Type B to IEC 62423, or Type F to IEC 62423. However, in the case of a PV power supply installation, Regulation 712.418.104.22.168.2 of BS 7671 stipulates that the RCD (where required) shall be of Type B.
(v) Where a microgenerator is installed in a special installation or location covered by a specific section of Part 7 of BS 7671, the requirements applicable to that special installation or location must also be applied as relevant to the microgenerator. For example, this might place limitations on the positioning of the microgenerator, involve additional protection with an RCD or supplementary bonding, or the selection of a microgenerator with a specified IP rating.
The specific additional requirements for each of the two connection options are given below. Connection of a microgenerator to a dedicated circuit (Fig 1(a) refers)
(vi) The basic design parameters for the circuit are: • Ib >_Ig, where Ib is the design current and Ig is the rated output current of the microgenerator (Regulation 523.1 of BS 7671 refers) • In >_Ib, where In is the rated current of the overload protective device (Regulation 433.1.1(i) of BS 7671 refers) • disconnection of the circuit in the event of an earth fault on the circuit within 5 s for TN systems and 1 s for TT systems (Regulations 422.214.171.124 and 4126.96.36.199 respectively of BS 7671 refer).
(vii) The circuit must connect to the supply side of the overcurrent protective device of each final circuit of the installation (Regulation 551.7.2, second line, refers). This can be achieved by connecting the circuit to a dedicated outgoing overcurrent protective device in the consumer unit.
(viii)Where a microgenerator is connected on the same side of an RCD as final circuits protected by that RCD, the RCD must disconnect the line and neutral conductors (Regulation 551.4.2 refers). For example, this applies to an RCD controlling a section of a consumer unit to which the dedicated circuit is connected via an outgoing way. Note.The reason for the above requirement is that if the RCD does not disconnect the neutral, protection no longer depends solely on the operation of the RCD, but also on the shut down characteristics of the microgenerator, due to the existence of a current path similar to that shown in Fig 2.
(It might be thought that the RCD need not disconnect the neutral if the dedicated circuit is connected to the consumer unit via an RCD, such as is mentioned in (ix). However, that is not the case, as that RCD would be unable to operate in response to current flowing to earth on its mains supply side, because (as mentioned in (i)) the winding of the microgenerator is not earthed.)
(ix) Where the circuit requires RCD protection, such as may be the case where the circuit cable is concealed in a wall or partition (Regulations 522.6.102 and 522.6.103 refer), the RCD must be located at the consumer unit end of the cable (generally by using an RCBO as the dedicated protective device for the circuit). Note.There is no need to locate an RCD at the microgenerator end of the circuit too, provided the winding of the microgenerator is not earthed (as should be the case – see (i)), as that RCD would be unable to detect a current flowing to earth supplied by the microgenerator.
(x)The microgenerator must be provided with means of isolation and of switching off for mechanical maintenance. (Regulation Groups 537.2 and 537.3, respectively, of BS 7671 refer. For PV systems, see also Regulation Group 712.522.8.3.) Note.See also ‘Labelling and isolation’, later in this Guide.
Connection of a microgenerator to an existing final circuit (Fig 1 refers). (Not permitted for a PV power supply system – see 712.4188.8.131.52.1)
(xi) The basic design parameters for the circuit are as follows.
a)Iz >_In + Ig, where Iz is the current-carrying capacity of the conductors of the final circuit, In is the rated current of the overload protective device and Ig is the rated output current of the microgenerator (Regulation 551.7.2(i) of BS 7671 refers). This may require the protective device to be replaced with one having a lower rated current.
b) The microgenerator must not be connected to the final circuit by means of a plug and socket (Regulation 551.7.2(ii) refers).
c) An RCD providing additional protection for the final circuit (where required) must disconnect all line and neutral conductors (Regulation 551.7.2(iii) refers).
d) The line and neutral conductors of the final circuit or of the microgenerator must not be connected to Earth (Regulation 551.7.2(iv) refers). For example, as already stated in (i), the winding of the microgenerator must not be earthed.
e) The protective device providing fault protection for the final circuit must disconnect the line and neutral conductors. The only exception to this requirement is where it has been verified that in the event of an earth fault on the circuit, the operation of the protective device and the reduction of the voltage of the microgenerator to 50 V or less will both occur within the disconnection time required by Regulation 411.3.2 for the final circuit. (Regulation 551.7.2(v) refers.)
f) The microgenerator must be provided with means of switching off for mechanical maintenance and of isolation from the remainder of the final circuit (Regulation Groups 537.2 and 537.3, respectively, refer).
Note: See also ‘Labelling and isolation’, later in this Guide. The reason for the requirement in (xi)e) is that, if the protective device does not disconnect the neutral, the effectiveness of the protection no longer depends solely on the operation of the protective device, but also on the shut down characteristics of the microgenerator.
Fig 2 shows, as an example, an earth fault downstream of an RCBO with unswitched neutral.
The earth fault causes operation of the RCBO, but the microgenerator can still supply current through the earth fault via the path shown in the diagram for a period until its own internal protection against loss of mains causes the microgenerator to shut down.
It should be noted that if the RCD element in the RCBO has been provided for additional protection, this arrangement is not permitted and the RCBO would need to switch both the line and neutral conductors; see (xi)c).
Isolation and labelling
A microgenerator is a source of supply to the electrical installation. A main linked switch or linked circuit-breaker for this source must therefore be provided in a readily accessible position as near as practicable to the origin of the installation, such as adjacent to the consumer unit, as a means of switching off the supply on load and as a means of isolation (Regulations 132.15.1, 537.1.4 and 551.2.4 refer). The switch or circuit-breaker must disconnect the line and neutral conductors (Regulation 5184.108.40.206 refers).
Means must also be provided to isolate the microgenerator from the public mains supply, as required by Regulation 551.7.6. This must be located at an accessible position within the installation, as required by clause 5.3 of G83/1-1†. Clause 220.127.116.11 of BS EN 50438: 2007 states that ‘Where this means of isolation is not accessible for the DNO at all times it is acceptable to provide two means of automatic disconnection, with a single control. At least one of the means of disconnection must be afforded by the separation of mechanical contacts.’
The same means of isolation could be used for the purposes of both the previous two paragraphs, if it meets all the requirements referred to in those paragraphs.
If the microgenerator is not in the same room as the main linked switch or linked circuit-breaker (as may be the case with the inverter of a PV system), a local isolator should also be installed adjacent to the microgenerator (Regulation 518.104.22.168 refers).
In all instances, the means of isolation, which must be manual, must be capable of being secured in the ‘off’ isolating position (Regulation 522.214.171.124 refers).
Where a static inverter forms part of the microgenerator installation, a means of isolation must be installed on both sides of the inverter. However, this requirement does not apply on the power source side of an inverter that is integrated in
the same enclosure as the power source. (Regulation 5126.96.36.199.3 refers).
Isolation and switching devices in any d.c. circuits, such as on the d.c. side of a PV installation, must be of types suitable for d.c use. Switchgear intended for a.c. circuits is often not suitable for d.c. or may need to be derated for such use. The manufacturer’s specific advice in this respect should be obtained and followed.
To comply with the labelling requirements of Regulation 514.15.1 relating to alternative or additional sources of supply, and those of clause 6.2 of G83/1-1† and clause 6.4 of BS EN 50438: 2007, warning labels must be provided as a minimum at: • the DNO’s fused cutout • the DNO’s meter position • the consumer unit(s) • the output terminals of the microgenerator • the points of isolation for the mains supply and the microgenerator supply. In the case of a renewable source, such as PV cells or a wind turbine, a notice must be placed at the microgenerator isolator to warn that the conductors on the microgenerator side may remain live when the isolator is open.
The Health and Safety (Safety Signs and Signals) Regulations 1996 stipulate that the labels should display the prescribed triangular shape and font size using black on yellow colouring. A typical label is shown below.
The above label is reproduced from Figure 1 of G83/1-1 In addition, G83 requires up-to-date information to be displayed at the point of connection with a DNO’s network as follows:
A circuit diagram showing the relationship between the microgenerator and the DNO’s fused cut-out. This diagram is also required to show by whom the generator is owned and maintained.
A summary of the separate settings of the protection incorporated within the equipment. The figure below is an example of the type of circuit diagram that needs to be displayed. This diagram is for illustrative purposes and not intended to be fully descriptive.
The installer is required to advise the customer that it is the customer’s responsibility to ensure that this safety information is kept up to date.
The installation operating instructions must contain the manufacturer’s contact details, such as name, telephone number and web address.
Combined heat and power (CHP)
Process that generates heat some of which provides the motive power to a microgenerator that is part of the heat generating device
Distribution network operator (DNO)
Owner or operator of low voltage electrical lines and equipment that are used to distribute electricity to consumers
A person who supplies electricity to a consumer from a DNO’s network
A meter, complying with the appropriate meter legislation, which measures the amount of electricity being exported to the electricity network
A meter which the energy user is responsible for, complying with the appropriate meter legislation, and which measures the quantity of electricity generated by the energy user’s generation unit
A device rated at up to 16 A per phase designed for the small-scale production of heat and/or electricity from a low carbon source (based on the definition in section 82 of the Energy Act 2004) Network Low voltage electrical lines and equipment owned or operated by a DNO that are used to distribute electricity to consumers RCBO An electromechanical protective device intended to provide overcurrent protection and residual current protection
SSEG (Small Scale Embedded Generation/Generator) microgenerator
Type AC RCD
An RCD intended to operate for residual sinusoidal alternating currents, whether suddenly applied or slowly rising.
Type A RCD
An RCD intended to operate for the following forms of residual current, whether suddenly applied or slowly rising:
Residual sinusoidal alternating currents - residual pulsating direct currents - residual pulsating direct currents superimposed on a smooth direct current of 6 mA.
Type B RCD
An RCD intended to operate for the following forms of residual current, whether suddenly applied or slowly rising: - residual sinusoidal alternating currents up to 1000 Hz - residual alternating currents superimposed on a smooth direct current of 0.4 times the rated residual operating current - residual pulsating direct currents superimposed on a smooth direct current of 0.4 times the rated residual operating current - residual direct currents which may result from rectifying circuits.
Type F RCD
An RCD intended for installations where frequency inverters are supplied between line and neutral or line and earthed middle conductor, and able to provide protection in the event of alternating residual sinusoidal at the rated frequency, pulsating direct residual currents and composite residual currents that may occur.
British Standards and other standards referred to:
British Standards BS 7671 Requirements for electrical installations. IET Wiring Regulations. Seventeenth edition
BS EN 50438 Requirements for the connection of micro-generators in parallel with public low-voltage distribution networks
BS EN 61008 Residual current operated circuit-breakers without integral overcurrent protection for household and similar uses (RCCBs). General rules
BS EN 61009 Residual current operated circuit-breakers with integral overcurrent protection for household and similar uses (RCBOs). General rules
Other standards IEC 62423 Type F and type B residual current operated circuitbreakers with and without integral overcurrent protection for household and similar uses
Electrical installation condition reporting: Classification Codes for domestic and similar electrical installations
The aim of this Guide is to provide practical guidance for competent persons on the use of the Classification Codes that need to be attributed to each observation recorded during the periodic inspection and testing of an electrical installation for the benefit of the person ordering the report.
The guidance is limited to the range of observations that are likely to be associated with domestic and similar electrical installations. It takes into account the publication of Amendment 1 to BS 7671: 2008.
Every electrical installation deteriorates with use and time. Therefore, if the safety of the users is not to be put at risk, it is important that every installation is periodically inspected and tested by a competent person. Indeed, it is recommended in BS 7671: 2008 as amended (Regulation 135.1) that every electrical installation is subjected to periodic inspection and testing.
The inspection and testing should be carried out at appropriate intervals in order to determine what, if anything, needs to be done to maintain the installation in a safe and serviceable condition.
The results of the inspection and testing need to be clearly detailed in a report. Any observed damage, deterioration, defects, dangerous conditions and non-compliances with the requirements of the current edition of BS 7671 that may give rise to danger should be recorded and appropriately classified for remedial action.
It should be borne in mind that, as stated in the introduction to BS 7671, existing installations that have been constructed in accordance with earlier editions of the Standard may not comply with the current edition in every respect, but this does not necessarily mean that they are unsafe for continued use or require upgrading.
An electrical installation condition report is, as its title indicates, a report and not a certificate. It provides an assessment of the in-service condition of an electrical installation against the requirements of the edition of BS 7671 current at the time of the inspection, irrespective of the age of the installation.
The report is primarily for the benefit of the person ordering the work and of persons subsequently involved in additional or remedial work, or further inspections. The report may be required for one or more of a variety of reasons, each of which may impose particular requirements or limitations on the inspection and testing.
The report is required to include details of the extent of the installation and of any limitations of the inspection and testing, including the reasons for any such limitations and the name of the person with whom those limitations were agreed. It should be noted that the greater the limitations applying, the lesser is the scope of the inspection and testing carried out, and hence the value of the report is correspondingly diminished. The report is also required to include a record of the inspection and the results of testing.
The report provides a formal declaration that, within the agreed and stated limitations, the details recorded, including the observations and recommendations, and the completed schedules of inspection and test results, give an accurate assessment of the condition of the electrical installation at the time it was inspected.
Purpose of periodic inspection, testing and reporting
The main purpose of periodic inspection and testing is to detect so far as is reasonably practicable, and to report on, any factors impairing or likely to impair the safety of an electrical installation.
The aspects to be covered include all of the following:
• Safety of persons against the effects of electric shock and burns
• Protection against damage to property by fire and heat arising from an installation defect
• Confirmation that the installation is not damaged or deteriorated so as to impair safety
• Identification of non-compliances with the current edition of BS 7671, or installation defects, which may give rise to danger.
All persons carrying out the inspection and testing of electrical installations must be competent to do so.
To be competent to undertake the periodic inspection and testing of an existing electrical installation, persons must as a minimum:
• Have sufficient knowledge and experience of electrical installation matters to avoid injury to themselves and others
• Be familiar with, and understand, the requirements of the current edition of BS 7671 including those relating to inspection, testing and reporting • Be skilled in the safe application of the appropriate test instruments and procedures
• Have a sound knowledge of the particular type of installation to be inspected and tested
• Have sufficient information about the function and construction of the installation to allow them to proceed in safety.
If the inspector is competent and takes all the necessary safety precautions including following the correct procedures, the process of inspecting and testing should not create danger to persons, or cause damage to property.
Past events indicate that persons undertaking electrical installation condition reporting need to have extensive knowledge and experience of electrical installation matters to enable them to safely and accurately assess the condition of an existing electrical installation. This is especially so when they do not have access to the design or maintenance information relating to that installation.
Guidance on safe isolation procedures is available in another Best Practice Guide (No 2 in the series) published by Electrical Safety First, which can be downloaded free of charge from www.electricalsafetyfirst.org.uk and other contributing bodies.
Periodic inspection and testing procedures
The procedures for periodic inspection and testing differ in some respects from those for the initial verification of new installation work.
This is because the subject of an electrical installation condition report is usually an installation which has been energised and in use for some time. Particular attention therefore needs to be given during the inspection process to assessing the condition of the installation in respect of:
• Wear and tear
• Damage and deterioration
• Excessive loading
• External influences
• Suitability (taking account of any changes in use or building extensions etc).
Also, for reasons beyond the inspector’s control, the inspector may be unable to gain access to parts of the existing installation. For example, it is usually impracticable to inspect cables that have been concealed within the fabric of the building.
Such restrictions are likely to result in the inspection and testing of those parts of the installation being limited, or being omitted entirely from the process.
Where, during the course of inspection or testing, a real and immediate danger is found to be present in an installation (from an accessible exposed live part, for example), immediate action will be necessary to make it safe before continuing. However, the discovery of the dangerous condition should still be recorded in the report and classified accordingly.
Inspectors should note that, even in domestic premises, Section 3 of the Health and Safety at Work etc Act 1974 and the Electricity at Work Regulations 1989 effectively require them to endeavour to make safe, before leaving site and with the agreement of the user or owner, any dangerous conditions found in an installation. For example, where there are accessible live parts due to blanks missing from a consumer unit, suitable temporary barriers should be provided to protect persons from direct contact with those live parts.
As persons using the installation are at risk, it is not sufficient simply to draw attention to the danger when submitting the electrical installation condition report. At the very least, the inspector must ensure that the client is made aware, at the time of discovery, of the danger that exists. An agreement should be made with the client as to the appropriate action to be taken to remove the source of danger (for example, by switching off and isolating the affected part of the installation until remedied), before continuing with the inspection or testing.
Some certification, registration and membership bodies make available ‘dangerous condition notification’ forms. These assist inspectors to record, and then to communicate immediately to the person responsible for the safety of the installation, any dangerous condition discovered.
The periodic inspection and testing procedures should identify any damage, deterioration, defects and conditions within the installation that give rise, or potentially give rise, to danger. The procedures should also identify any deficiencies for which remedial action would contribute to a significant improvement in the safety of the electrical installation.
After due consideration, each such observed safety issue should be recorded at the appropriate point in the inspection or test results schedule, and further detailed in the ‘observations’ section of the report.
The observations should be based on the requirements of the edition of BS 7671 current at the time of the inspection, not on the requirements of an earlier edition current at the time the installation was constructed.
Each observation should be written in a clear, accurate and concise manner that is likely to be understood by the person ordering the work. Technical terms should be avoided or explained unless it is known that the recipient is an electrical engineer or electrician, for example.
An electrical installation condition report is intended to be a factual report on the condition of an installation, not a proposal for remedial work. Therefore, each recorded observation should describe a specific defect, omission or item for which improvement is recommended.
The observation should detail what the situation is, and not what is considered necessary to put it right. For example, ‘excessive damage to the consumer unit enclosure’ would be appropriate, whereas ‘consumer unit to be replaced’ would not.
Only observations that can be supported by one or more regulations in the edition of BS 7671 current at the time of the periodic inspection should be recorded. The particular regulation number(s) need not be entered in the report (unless specifically required by the client), but should serve to remind the inspector that it is only compliance with BS 7671 that is to be considered. Observations based solely on personal preference or ‘custom and practice’ should not be included.
Each observation relating to a concern about the safety of the installation should be attributed an appropriate Classification Code selected from the standard codes C1, C2 and C3. Each code has a particular meaning:
Code C1 ‘Danger present’.
Risk of injury. Immediate remedial action required.
Code C2 ‘Potentially dangerous’.
Urgent remedial action required
Code C3 ‘Improvement recommended’.
Only one of the standard Classification Codes should be attributed to each observation. If more than one Classification Code could be attributed to an observation, only the most serious one should be used (Code C1 being the most serious).
Where the inspection and testing procedures identify an item which is dangerous or potentially dangerous, it should be identified in the inspection or test results schedule of the report by attributing to it a Classification Code C1 or C2, as appropriate, in the ‘outcome’ column of the inspection schedule or, where provided, the ‘remarks’ column of the test schedule.
Where during inspection and testing a real and immediate danger is observed that puts the safety of those using the installation at risk, Classification Code C1 (danger present) must be given. Where a Classification Code C1 is considered appropriate, the client is to be advised immediately, and also in writing, that immediate remedial action is required (or has been taken) to remove the danger.
As previously indicated, this action is necessary to satisfy the duties imposed on the inspector and other duty holders by the Health and Safety at Work etc Act 1974 and the Electricity at Work Regulations 1989.
Wherever an item in the inspection or test results schedule has been attributed a Classification Code C1, C2 or C3, there should be a corresponding observation in the ‘observations’ section of the report.
In general terms, the Classification Codes should be used as follows:
Code C1 (Danger present)
This code should be used to indicate that danger exists, requiring immediate remedial action.
The persons using the installation are at immediate risk. The person ordering the report should be advised to take action without delay to remedy the observed deficiency in the installation, or to take other appropriate action (such as switching off and isolating the affected parts of the installation) to remove the danger. The inspector should not wait for the full report to be issued before giving this advice.
As previously indicated, some certification, registration and membership bodies make available ‘dangerous condition notification’ forms to enable inspectors to record, and then to communicate immediately to the person ordering the report, any dangerous condition discovered.
Code C2 (Potentially dangerous)
This code should be used to indicate that, whilst an observed deficiency is not considered to be dangerous at the time of the periodic inspection, it would become a real and immediate danger if a fault or other foreseeable event was to occur in
the installation or connected equipment.
The person ordering the report should be advised that, whilst the safety of those using the installation may not be at immediate risk, remedial action should be taken as a matter of urgency to remove the source of potential danger.
Code C3 (Improvement recommended)
This code should be used to indicate that, whilst an observed deficiency is not considered to be a source of immediate or potential danger, improvement would contribute to a significant enhancement of the safety of the electrical installation.
Further investigation The model forms in BS 7671: 2008 incorporating Amendment 1 provide for a need for further investigation to be indicated against each inspection and test outcome, and against each observation. Usually, however, it should be possible to attribute a Classification Code to each observation without the need for further investigation.
The purpose of periodic inspection, as previously stated, is not to carry out a fault-finding exercise, but to assess and report on the condition of an installation within the agreed extent and limitations of the inspection. Therefore, where an observation can be attributed a Classification Code, further investigation would not be required for the purposes of completing the condition report.
Further investigation should not be called for in respect of any observation unless that investigation could reasonably be expected to reveal danger or potential danger. Further investigation should not be called for simply because it would be ‘nice to know’ – for example, why a socket-outlet is unearthed.
If an observation cannot be attributed a Classification Code due to reasonable doubt as to whether danger or potential danger exists, the outcome of the assessment must be reported to be unsatisfactory.
The person ordering the report should be advised that the inspection and/or testing has revealed a potential safety issue which could not, due to the agreed extent or limitations of the inspection, be fully determined, and that the issue should be investigated as soon as possible.
An example of an observation that might possibly justify further investigation is given on page 17.
Departures from the requirements of the current edition of BS 7671 that do not give rise to danger or need improvement
Amendment 1 to BS 7671: 2008 no longer requires departures from the requirements of the current edition of BS 7671 that do not give rise to danger or need improvement to be recorded in condition reports. (Examples of such departures are given on page 17.)
Summary of the condition of the installation
The summary should adequately describe the general condition of the installation in terms of electrical safety, taking into account the specific observations made. It is essential to provide a clear summary of the condition of the installation having considered, for example:
• The adequacy of the earthing and bonding arrangements
• The suitability of the consumer unit and other control equipment
• The type(s) of wiring system, and its condition
• The serviceability of equipment, including accessories
• The presence of adequate identification and notices
• The extent of any wear and tear, damage or other deterioration
• Changes in use of the premises that have led to, or might lead to, deficiencies in the installation.
Minimal descriptions such as ‘poor’, and superficial statements such as ‘recommend a rewire’, are considered unacceptable as they do not indicate the true condition of an installation. It will often be necessary or appropriate to explain the implications of an electrical installation condition report in a covering letter, for the benefit of recipients who require additional advice and guidance about their installation. For example, where an installation has deteriorated or been damaged to such an extent that its safe serviceable life can reasonably be considered to be at an end, a recommendation for renewal should be made in a covering letter, giving adequate supporting reasons. Reference to the covering letter should be made in the report.
On the model electrical installation condition report given in BS 7671, a box is provided for the overall assessment of the condition of the installation to be given. After due consideration, the overall condition of the installation should be given as either ‘satisfactory’ or ‘unsatisfactory’.
If any observation in the report has been given a Code C1 or Code C2 classification as categorised in this Guide, or if any observations require further investigation to determine whether danger or potential danger exists, the overall assessment of the condition of the installation must be reported to be ‘unsatisfactory’.
If there are no observations in the report classified as C1 or C2, or that require further investigation, it would not be reasonable to report the overall condition of the installation as unsatisfactory.
The recommended interval until the next inspection should be made conditional upon all observations that have been given a Classification Code C1 (danger present) being remedied immediately and all observations that have been given a Code C2 (potentially dangerous) or that require further investigation being remedied or investigated respectively as a matter of urgency.
Where the space provided for the description of the general condition of the installation is inadequate for the purpose and it is necessary to continue the description on an additional page(s), the page number(s) of the additional page(s) should be recorded.
Examples of the use of Classification Codes
It is entirely a matter for the competent person conducting the inspection to decide on the Classification Code to be attributed to an observation. The inspector’s own judgement as a competent person should not be unduly influenced by the person ordering the work. The person(s) signing the report are fully responsible for its content and accuracy.
The following examples are not exhaustive. All references to RCD protection mean additional protection by an RCD having a rated operating (tripping) current (I∆n) not greater than 30 mA and an operating time not exceeding 40 ms at a residual current of 5 I∆n.
Code C1 (Danger present) Observations that would almost certainly warrant a Code C1 classification include:
• Exposed live parts that are accessible to touch, such as where: ❍ a fuse carrier or circuit-breaker is missing from a consumer unit and a blanking piece is not fitted in its place
❍ terminations or connections have no (or damaged) barriers or enclosures
❍ live conductors have no (or damaged) insulation
❍ an accessory is badly damaged.
• Conductive parts have become live as the result of a fault
• Incorrect polarity Code C2 (Potentially dangerous) Observations that would usually warrant a Code C2 classification include:
• Absence of a reliable and effective means of earthing for the installation
• A public utility water pipe being used as the means of earthing for the installation
• A gas or oil pipe being used as the means of earthing for the installation
• Cross-sectional area of the earthing conductor does not satisfy adiabatic requirements (that is, does not comply with Regulation 543.1.1)
• Absence of a circuit protective conductor for a lighting circuit supplying one or more items of Class I equipment, or connected to switches having metallic face plates2
• Absence of a notice warning that lighting circuits have no circuit protective conductor2
• Absence of a circuit protective conductor for a circuit, other than a lighting circuit, supplying one or more items of Class I equipment
• Absence of earthing at a socket-outlet
• Absence of main protective bonding
• Inadequate cross-sectional area of a main protective bonding conductor where the conductor is less than 6 mm2 or where there is evidence of thermal damage
• Absence of supplementary bonding where required3 , such as in a location containing a bath or shower, where anyof the following three conditions are not satisfied:
❍ All final circuits of the location comply with the requirements of Regulation 411.3.2 for automatic disconnection, and
❍ All final circuits of the location have additional protection by means of a 30 mA RCD, and
❍ All extraneous-conductive-parts of the location are effectively connected to the protective equipotential bonding (main earthing terminal).
• The main RCD or voltage-operated earthleakage circuit-breaker on a TT system fails to operate when tested with an instrument or integral test button
• Absence of RCD protection for portable or mobile equipment that may reasonably be expected to be used outdoors
• Absence of RCD protection for socket-outlets in a location containing a bath or shower, other than for SELV or shaver socket-outlets
• Socket-outlets other than SELV or shaver socketoutlets located less than 3 m horizontally from the boundary of zone 1 in a location containing a bath or shower
• Absence of fault protection (protection against indirect contact) by RCD where required, such as for a socket-outlet circuit in an installation forming part of a TT system
• Circuits with ineffective overcurrent protection (due, for example, to oversized fuse wire in rewireable fuses)
• A protective device installed in a neutral conductor only • Separate protective devices in line and neutral conductors (for example, double-pole fusing)
• Earth fault loop impedance value greater than that required for operation of the protective device within the time prescribed in the version of BS 7671/IET Wiring Regulations current at the time of installation
• A ring final circuit having a discontinuous conductor
• A ring final circuit cross-connected with another circuit
• Inconsistent resistance values for the conductors of ring final circuits
• Unsatisfactory electrical connection (such as a loose connection or type, number and/or size of conductors unsuitable for the means of connection)
• A ‘borrowed neutral’, for example where a single final circuit neutral is shared by two final circuits (such as an upstairs lighting circuit and a separately-protected downstairs lighting circuit)
• Insulation resistance of less than 1 MΩ between live conductors connected together and Earth, when measured at the consumer unit with all final circuits connected
• Insulation of live conductors deteriorated to such an extent that the insulating material readily breaks away from the conductors
• Sheath of an insulated and sheathed nonarmoured cable not taken inside the enclosure of an accessory, such as at a socket-outlet or lighting switch, where the unsheathed cores are accessible to touch and/or likely to come into contact with metalwork. (Note: Code C3 would apply if the unsheathed cores are not accessible to touch nor likely to come into contact with metalwork)
• Unenclosed electrical connections, such as at luminaires. (Such a defect can contribute to a fire, particularly where extra-low voltage filament lamps are used) • Fire risk from incorrectly installed electrical equipment, including incorrectly selected or installed downlighters
• Fire risk from lamps exceeding the maximum rated wattage for the luminaires, or placed too close to combustible materials
• Evidence of excessive heat (such as charring) from electrical equipment causing damage to the installation or its surroundings
• Unsatisfactory functional operation of equipment where this might result in danger
• Immersion heater does not comply with BS EN 60335-2-73 (that is, it does not have a built-in cut-out that will operate if the stored water temperature reaches 98 OC if the thermostat fails), and the cold water storage tank is plastic
• Electrical equipment having an inadequate degree of ingress protection (IP rating) for the external influences likely to occur in the location, if this results in potential danger
• Absence of warning notices indicating the presence of an alternative or secondary source of electricity, such as a standby generator or microgenerator
• Fixed equipment does not have a means of switching off for mechanical maintenance, where such maintenance involves a risk of burns, or injury from mechanical movement.
Code C3 (Improvement recommended)
Observations that would usually warrant a Code C3 classification include:
• Absence of RCD protection for a socket-outlet that is unlikely to supply portable or mobile equipment for use outdoors, does not serve a location containing a bath or shower, and the use of which is otherwise not considered by the inspector to result in potential danger.
(Note: Code C2 would apply if the circuit supplied a socket-outlet in a location containing a bath or shower in accordance with Regulation 701.512.3)
• Absence of RCD protection for cables installed at a depth of less than 50 mm from a surface of a wall or partition where the cables do not incorporate an earthed metallic covering, are not enclosed in earthed metalwork, or are not mechanically protected against penetration by nails and the like
• Absence of RCD protection for circuits of a location containing a bath or shower where satisfactory supplementary bonding is present
• Reliance on a voltage-operated earth-leakage circuit-breaker for fault protection (protection against indirect contact), subject to the device being proved to operate correctly. (If the circuit-breaker relies on a water pipe not permitted by Regulation 542.2.6 as the means of earthing, this would attract a Code C2 classification.)
• Absence of a quarterly test notice for any RCD or voltage-operated earth-leakage circuitbreaker
• Absence of circuit protective conductors in circuits having only Class II (or all-insulated) luminaires and switches4
• Absence of ‘Safety Electrical Connection — Do Not Remove’ notice
• Sheath of an insulated and sheathed nonarmoured cable not taken inside the enclosure of an accessory, such as at a socket-outlet or lighting switch. (Note: Code C2 would apply if unsheathed cores are accessible to touch and/or likely to come into contact with metalwork)
•Bare protective conductor of an insulated and sheathed cable not sleeved with insulation, colour coded to indicate its function
• Electrical equipment having an inadequate degree of ingress protection (IP rating) for the external influences likely to occur in the location, if this does not result in potential danger
• Socket-outlet mounted in such a position as to result in potential damage to socket, plug and/or flex
• Absence of a notice indicating that the installation has wiring colours to two versions of BS 7671 (if appropriate)
• Absence of circuit identification details
Further investigation required
Observations that would usually require further investigation include:
• Characteristics of electricity supply (such as voltage or external earth fault loop impedance) do not conform to supply industry norms. Departures from the requirements of the current edition of BS 7671 that do not give rise to danger or need improvement
Amendment 1 to BS 7671: 2008 no longer requires departures from the requirements of the current edition of BS 7671 that do not give rise to danger or require improvement to be included in condition reports. Such departures include:
• Absence of a reliable earth connection to a recessed metallic back box of an insulated accessory, such as where there is no ‘earthing tail’ connecting the earthing terminal of the accessory to the box, and the box does not have a fixed lug that comes into contact with an earthed eyelet on the accessory
• Inadequate cross-sectional area of a main protective bonding conductor provided that the conductor is at least 6 mm2 and that there is no evidence of thermal damage
• Absence of supplementary bonding for installed Class II equipment where required (such as in a location containing a bath or shower), in case the equipment is replaced with Class I equipment in the future
• Main protective bonding to gas, water or other service pipe is inaccessible for inspection, testing and maintenance, or connection not made before any branch pipework. (Note: The connection should preferably be within 600 mm of the meter outlet union or at the point of entry to the building if the meter is external.)
• Protective conductor of a lighting circuit not (or incorrectly) terminated at the final circuit connection point to a Class II (or insulated) item of equipment, such as at a switch mounting box or luminaire
• Switch lines not identified as line conductors at terminations (for example, a conductor having blue insulation is not sleeved brown in switches or lighting points)
• Circuit protective conductors or final circuit conductors in a consumer unit not arranged or marked so that they can be identified for inspection, testing or alteration of the installation
• Installation not divided into an adequate number of circuits to minimise inconvenience for safe operation, fault clearance, inspection and testing
• Inadequate number of socket-outlets. (Code C3 or, where appropriate C2, if extension leads run through doorways, walls or windows, or under carpets, or are otherwise being used in an unsafe manner)
• Use of unsheathed flex for lighting pendants
• Cable core colours complying with a previous edition of BS 7671.
Items that are NOT departures from the current edition of BS 7671
The following items are commonly included in electrical installation condition reports as requiring remedial action, but are not departures from the current edition of BS 7671, and should therefore not be recorded:
• Absence of earthing and/or bonding to metallic sinks and baths (unless they are extraneousconductive-parts in their own right)
• The use of rewireable fuses (where they provide adequate circuit protection)
• The use of circuit-breakers to BS 3871
•Absence of barriers inside a consumer unit (provided the cover is removable only with the use of a key or tool)
• Absence of bonding connections to boiler pipework (where the pipework is not an extraneous-conductive-part in its own right)
• Shaver supply units installed in zone 2 of a location containing a bath or shower and located where direct spray from a shower is unlikely
• Absence of switches on socket-outlets and fused connection units
• Any other observation not directly related to electrical safety and hence to the suitability of the installation for continued service.
The following items are worthy of an appropriate note in the electrical installation condition report, but should not be given a Classification Code:
• The absence of a fire detection and alarm system (smoke/heat/carbon monoxide detectors etc)
• The absence of an emergency lighting system in a location normally requiring such a system (for example in a communal area of a block of flats)
• Combustible materials stored in close proximity to the electrical intake equipment (consumer unit/meter/service head)
Label warning against storing combustible materials near to
Electrical Installations and their impact on the fire performance of buildings:
Part 1- Domestic premises:
Single family units (houses, flats, maisonettes, bungalows)
1.1 The aim of this Guide is to promote best practice by providing practical advice and guidance for designers, installers, verifiers and inspectors of domestic electrical installations where, as is often the case, the electrical work requires, or has required, the penetration of linings forming ceilings and walls.
The guidance, which is intended to apply to electrical installations designed after July 2008, may also be of benefit to specifiers, builders, building control bodies and other interested parties.
By following the guidance, it is considered that electrical installation work will not compromise the fire performance provisions that are mandatorily required to be incorporated into domestic premises under the relevant building regulations.
This Guide has been produced by Electrical Safety First in association with the bodies indicated on page 2.
It addresses the impact that electrical installations in domestic premises have on the fire performance of loadbearing and non-loadbearing walls and floors (and sometimes ceiling membranes) that have a fire containment function, or are required to carry a load for a prescribed period.
Fire safety in buildings generally requires that in the event of a fire:
• certain walls, floors and ceilings provide fire separation for the purposes of constructing fire compartments and/or protected escape routes, and
• the structure resists collapse.
The advice given in this Guide is aimed largely at preserving the structural stability of the premises as much as the fire separation between areas. For example, in most domestic premises, it is the loadbearing capacity of the floors that is threatened by early failure of ceiling linings, not the fire separating function.
Many modern forms of engineered construction have an inherently lower level of fire resistance when compared to more traditional forms of construction, and are heavily reliant on the plasterboard or similar linings for achieving the requisite level of fire separation.
Much of the guidance is related to the effect that the installation of electrical equipment will have on the performance of the protective linings that are used to provide fire protection to lightweight joisted or studded constructions. In the case of the associated wiring, the need to prevent fire from passing through holes in all elements, whether solid or lightweight, is also addressed.
Amongst these forms of construction are narrow section solid, stress graded timber joists, plywood/Orientated Strand Board (OSB) webbed I joists (‘timber I beams’), tooth or nail-plated trusses and joists, composite timber studs and lightweight metal studs. Illustrations of these vulnerable forms of construction are to be found in Annex A.
The fire resistance of these elements can easily be compromised by inadequate fire sealing and 'making good' after any penetration to accommodate electrical equipment and associated wiring.
Electrical equipment that has been identified as having a direct and significant influence on the fire performance of buildings includes:
• flush-mounted consumer units
• concealed and recessed luminaires, including downlighters
• flush-mounted electrical socket-outlets, flex outlet plates and data points
• flush-mounted switches, detection and control devices
• recessed wall luminaires
• concealed speakers.
The above items all require the removal of a part of the ceiling or wall lining, and replacement with glass, thin metal or plastic that does not provide the same level of fire protection to the structural members, causing a reduction in the fire performance of the element. These are known as partial penetrations.
In addition to the influence that these partial penetrations have on the fire performance, some installations can penetrate both linings, such as:
• associated wiring and conduits
• ventilation fans and related ductwork.
These installations have a potential to compromise the fire containment capability, and guidance is included for these situations. These are known as full penetrations.
In addition to the above items that all have a direct influence on the fire performance of floors or walls, the following items can also have an indirect influence if the lining provides some or all of their support:
• heavy ceiling-hung luminaires, lighting tracks and overhead projectors
• wall-mounted brackets for televisions, heavy speakers and flat screen installations.
If the room is involved in fire, the weight of such items may lead to the premature failure of the lining material.
In addition to the risk of the electrical installation reducing the fire separation capabilities of those elements that need to resist fire spread or to remain structurally sound in a fire, a poorly constructed installation can potentially be the cause of a fire, for example due to heat generated by loose connections.
This Guide addresses all of these issues.
The fire separating capability of an element of construction is generally measured by the duration for which the element will satisfy the criteria of a fire resistance test. Historically, these criteria have been determined by exposure to the BS 476: Part 20: 1987 heating and pressure conditions, but more recently by the new European testing regime as embodied in BS EN 1363-1. More information on the relevant test methods and criteria can be found in Annex B.
This Guide gives practical advice and guidance for the installation, and the making good following the installation, of electrical equipment and wiring in self-contained domestic premises (including bungalows, multi-storey houses, individual flats and maisonettes) that are designed to accommodate a single family unit. The advice and guidance applies to both new and existing premises.
The Guide does not apply directly to Houses in Multiple Occupation, hostels, caravans or boats, or to the communal parts of blocks of flats or the communal parts of maisonettes, nor does it apply to any premises used for purposes other than a dwelling (such as small shops, factories or similar premises used solely as places of work). Guidance for these building types may be found in other Parts of this Best Practice Guide (in preparation).
The Guide gives advice on what needs to be done to maintain the fire resistance of walls and ceilings in domestic premises that have been penetrated or partially penetrated in the process of installing electrical equipment and wiring.
It does not consider in detail the impact that the installation of electrical equipment and wiring may also have on the structural, acoustic or energy targets prescribed in building regulations.
The Guide gives recommendations as to what is considered to be best practice, taking into account that electrical installers may not have adequate knowledge of the construction of the elements that are potentially being compromised by their work.
Where an installer wishes to differentiate between new and traditional forms of construction, the guidance given in Annex C may assist. Some investigations may require the services of another professional, such as a surveyor or fire specialist.
Note: This Guide does not necessarily apply to all innovative or unusual forms of construction or electrical equipment. If in doubt, specialist advice should be sought.
General electrical installation requirements
This Guide takes into account the publication of BS 7671: 2008 (Requirements for Electrical Installations, IEE Wiring Regulations 17th Edition), which is the latest version of the national standard for the safety of electrical installations, first published in 1882.
BS 7671 requires, in Section 421 (Protection against fire caused by electrical equipment),that equipment must not present a fire hazard to adjacent materials, and that manufacturers’ instructions must be complied with. Section 421 also requires that fixed equipment causing a concentration and focusing of heat (such as spotlamps) shall be at a sufficient distance from any fixed object or building element so that the object or element is not subjected to a dangerous temperature in normal conditions.
Also, in Section 527 (Selection and erection of wiring systems to minimise the spread of fire)of that standard, it is required that wiring systems are selected and erected to minimise the spread of fire, including:
• Within a fire-segregated compartment, the risk of the spread of fire must be minimised by the selection of appropriate materials, and by the appropriate construction of the installation (Regulation 527.1.1), and
• A wiring system must be installed so that the general building structural performance and fire safety performance are not reduced (Regulation 527.1.2), and
• Where a wiring system passes through elements of building construction such as floors, walls, roofs, ceilings, partitions or cavity barriers, the openings remaining after the passage of the wiring system must be sealed according to the degree of fire resistance (if any) prescribed for the respective element of building construction before penetration (Regulation 527.2.1).
Regulation 510.2 requires manufacturers’ instructions to be taken into account. It is important to do this in order, for example, to prevent luminaires becoming a source of ignition. (Any installation instructions that are considered to be inappropriate should be queried with the manufacturer concerned, and amended installation instructions requested.)
All terminations and joints, whether for low voltage (LV) or extra-low voltage (ELV) circuits, should be enclosed in accordance with Regulation 526.5 to prevent fire spread should a loose connection occur.
As part of the initial verification process, the electrical installer has a duty to ensure that all the necessary fire precautions have been taken, irrespective of which party was responsible for that element of the electrical work (Regulation 611.3(vii)).
Building regulations for each part of the UK define fire performance objectives for the various elements that make up domestic premises, and give recommended performance levels in guidance supporting those regulations. The objectives are taken into account in this Guide. For further information, see Annex D.
It is vital that the fire performance of critical walls and floors is maintained to at least the level recommended in the guidance supporting the regulations, after the installation of electrical equipment and associated wiring.
For properties in England and Wales, attention is drawn to the Party Wall Act. Under this Act, any work undertaken on the party wall between properties which could affect its performance (or indirectly affect the structure of an attached neighbouring property) is a notifiable activity. In Scotland, a building warrant is required for any work that adversely affects a separating wall or a separating floor.
The fitting of electrical equipment in a masonry party wall has never been considered as being notifiable, but cutting holes in the linings and installing 'plastic' accessories may be deemed to be covered by statutory requirements. Electrical Safety First therefore recommends that the neighbour be advised of the intended work in order to give them the opportunity to object to, comment upon, or prevent the work taking place.
Electrical installation work will often be undertaken on behalf of owners or tenants after the occupation of the premises and, as such, it is not subject to any form of third party audit or final approval. The electrical installer is therefore subject to a duty of care to ensure that the fire performance of the premises is not compromised. In Scotland, certain works require building warrant approval depending on the work proposed and the building type.
Note: In England & Wales, Part P of the Building Regulations and, in Scotland, Building Standard 4.5, make this a requirement, putting the responsibility on the installer if selfcertifying the work as compliant with building regulations. Currently, electrical safety in Northern Ireland is not controlled under building regulations.
Flush-mounted consumer units
Flush-mounted consumer units should not be installed in a fire separating wall. In exceptional circumstances, where this cannot be avoided, and subject to the agreement of the Local Authority, the enclosure of the consumer unit or a separate builder’s work enclosure around the consumer unit must provide a proven level of fire resistance commensurate with the fire separating element.
Downlighters (recessed luminaires)
When exposed to a fire from below, downlighters may provide far less protection to a cavity and the structural elements within it than the plasterboard they are replacing, unless suitable precautions are taken.
Electrical Safety First recommends that, wherever possible, downlighters having integral fire protection are selected for use in allceilings where the lining that is to be penetrated is the sole means of keeping fire and heat out of the cavity.
There are a number of types of downlighter available, and it is important that the type selected for a particular application has test evidence to support its fire performance when incorporated in a ceiling of the type into which it is to be installed.
Generally, the tests should have been carried out in accordance with BS 476: Part 21: 1987 or BS EN 1365-2. The nature of the test evidence can be critical, and is discussed in detail in Annex B.
Not all designs and styles of downlighter may be available with integral fire protection, especially where higher lighting levels and/or larger coverage is required. In these situations, additional fire protection may be fitted at the time of installation in the form of a 'fire hood', an insulated fireprotective box, or similar.
Such separate forms of protection must be fit for purpose and not be easily dislodged or compromised after installation by subsequent work. Any such protection must conform to the guidance given in Annex E.
Electrical Safety First recommends that downlighters installed in a ceiling beneath a roof space have integral fire protection, or are provided with some other suitable form of fire protection, in order to safeguard escape from the premises, restrict the spread of fire, and reduce the risk of premature failure of the roof structure.
In order to avoid the risk of fire (as well as reduced lamp and service life) caused by overheating, downlighters and any associated transformers must not be covered by thermal insulation. Building Regulations do not prohibit the leaving of a small area around downlighters free from thermal insulation where this is necessary to permit the dissipation of the heat they generate. However, due allowance for this should be made in the overall thermal performance of the premises.
In all cases, manufacturers’ installation instructions must be followed to avoid downlighters becoming a source of fire.
Guidance on the selection of suitable types of downlighter for particular applications is given in Table 1, below.
Flush-mounted accessories (including switches, sockets, flex outlet plates, data and telephone points etc)
Numerous flush-mounted accessories are common in modern homes. These generally comprise two components:
• a recessed housing, or back box
• a face plate with integral socket, switch mechanism, flex outlet etc, and associated wiring terminals.
Back boxes may be either moulded plastic or steel construction, but all designs incorporate large knockout sections, many times greater in diameter than the cables passing through them, which make them very permeable in a fire after the face plate has been destroyed by the heat. This permeability will allow hot gases into the cavity of the wall much more rapidly than the plasterboard. For fire separating applications, and for applications relied upon to resist collapse, this should be guarded against by providing additional localised fire protection.
The risks associated with fire penetrating through flush-mounted accessories are significant when they penetrate a 30 minute fire-resisting loadbearing stud wall, 'back-to-back' with other accessories in the same cavity (or interlinked cavities).
Therefore, where flush-mounted accessories penetrate each face of a 30 minute fire separating or loadbearing plasterboard lined wall within the same cavity space (that is, the gap between two studs), each accessory should be fitted with a back box that incorporates integral fire protection, or be fitted with a proprietary fire protection pad, unless evidence of the fire resistance performance of the accessories is available.
Such back boxes or protective pads must have evidence of performance to demonstrate that they have the ability to maintain the fire separation capability of a wall for 30 minutes, were they to be tested to BS 476: Part 21: 1987 (loadbearing) or BS 476: Part 22 (non-loadbearing), or the EN equivalent as appropriate (see Annex B), with plastic accessories fitted in both linings.
Recommendations for the protection of flushmounted accessories in timber or metal stud walls in particular situations are given in Table 2 (below).
Flush-mounted wall luminaires and concealed speakers in walls or ceilings
This type of equipment varies significantly in size, design and construction. It is therefore not possible to give specific advice in this Guide in respect of the best method of maintaining the fire performance of the lining(s) penetrated by such equipment.
In principle, however, speakers concealed in ceiling linings should be treated by analogy with downlighters, and both luminaires and speakers flush-mounted in walls should conform to the guidance given for flush-mounted accessories.
Where a luminaire or speaker has integral fire protection, then this must be to the appropriate test standard (see Annex B).
If the equipment does not have integral fire protection then, when it is being installed in a ceiling or wall that is required to provide fire separation, the equipment has to be provided with an ad hoc form of fire protection and, where appropriate, acoustic insulation. It may be difficult for the installer to establish what form of protection is likely to maintain the required fire resistance, and therefore any proposed method of providing protection should be tested, or more reasonably assessed in lieu of test evidence, by those authorities recognised in guidance in support of regulations*.
Proprietary protection is likely to become available in due course, and should be used when it does.
* Approved Document B for the Building Regulations for England & Wales (A1 of Annex A), or the Scottish Building Standards Technical Handbook, as appropriate
Cables, conduit and trunking penetrating internal fire separating walls and floors
This section provides guidance as to what should be done to preserve the fire resistance of elements that are required to provide fire resistance, when cables have to pass through them. The guidance is applicable to situations where insulated and sheathed cables, or cables in plastic conduit or plastic trunking, pass through floors and walls.
The fire risk associated with non-fire performance cables and plastic conduits and trunking passing through building elements is twofold. Initially there is a risk of a loss of integrity due to the heat and/or flames passing through any unsealed holes that have been made to allow the cable to pass through, resulting in flaming on the unexposed side. Secondly, the hole in a plasterboard lining will allow fire to get into the ceiling or wall void prematurely, cause ignition of the structure which can lead to a loss of loadbearing capacity.
With respect to the first of these, it is important that fire is not allowed to exploit either the initial penetration of the first lining (which could permit fire to get into the cavity), or subsequently to penetrate the second lining (which would allow the fire to effectively bypass the protective barrier).
Sealing the cable ingress point has to take into account that the insulation of non-fire performance cables will probably melt or char away, leaving an unfilled gap between the conductors and the lining. Depending upon the nature of the cable insulation, this may even have the potential to carry the flames on its surface into the void. On a single cable this is unlikely to be a serious risk, but the ability to make an adequate fire seal becomes increasingly difficult as the number of cables increase.
It is common and accepted practice to make good any hole around a cable by using inert filler such as plaster or grout, but this does not compensate for melting/flaming insulation, and will also be ineffective in voids between cables.
It is recommended, therefore, that the sealant used to make good holes through which cables pass has intumescent properties: that is, it has the ability to expand and fill any voids that are developing due to movement and/or melting of cables, in order to maintain the fire resistance of the element.
The risk of fire gaining premature access to any void is increased if the cables are run through a plastic conduit or trunking system, or are bunched. Any cosmetic sealing of the gap between the lining and the plastic conduit or trunking will certainly not be able to seal any voids between the cables and the outer plastic casing following the melting of the conduit or trunking.
In elements that require high levels of fire resistance, especially where there is a sleeping risk (such as 60 minute compartment walls and floors), it is recommended that a proprietary cable transit or a fire resisting conduit be installed in the construction element being penetrated, if services have to pass through one or both linings that form the wall.
NOTE: In Scotland, the guidance clause 2.2.7 (Domestic Handbook) recommends that combustible separating walls do not contain pipes, wires or other services. In buildings with a storey height over 18 m, separating walls and floors must be constructed of non-combustible materials.
Ventilation fans and related ductwork
Ventilation fans are normally fitted on an external wall rather than on an internal wall and, as a consequence, there is generally not a fire safety issue regarding the influence on the integrity and insulation rating of the wall due to such systems when installed in a cavity blockwork or masonry wall.
However, if fire were to enter the cavity of a stud wall or the cavity between the inner wall and any outer 'sheathing', the building can suffer both undue structural damage if modern engineered construction is used, and/or disproportionate fire spread in the cavity in more conventional properties. This cavity spread can result in an indirect loss of fire integrity between adjacent internal enclosures, and therefore fire should be prevented from gaining access to any of the cavities.
When installing a ventilation fan directly into a loadbearing external stud construction wall, the hole cut into the inner and outer lining should be lined out across the thickness of the wall with a continuous non-combustible material, preferably with some insulating properties, through which the extract duct passes**. This liner should be fixed in place so that it does not fall away over time.
When the vent from for example, a shower cubicle, is connected to an extended duct which runs within the floor void to an outside wall possibly via an in-line fan, then this length of low melting point ductwork (plastic or aluminium) will have no measurable fire resistance and fire entering into this duct, via the vent, will soon have access to the joists. Indeed, should the fan be in extract mode at the time of the fire, fire will be drawn into this void quite quickly.
Any void between two joists that contain such a duct which is running parallel with the joists should be lined on the face of both joists with fire protection board that duplicates the fire protection provided by the ceiling lining. The void beyond the duct should be separated by a transverse barrier of the same rating. Similarly, the flooring above may need to be underdrawn with fire protection board if it is buttjointed. The method of fire sealing the wall/duct interface will vary depending upon whether it is a studded construction or a conventional masonry cavity wall (see Figures 11a and 11b).
11.6 Where the duct runs transverse to the joists, the amount of joist to be cut away is likely to be structurally significant and expert guidance should be sought, in respect of both the effect on the structure and the fire separation measures.
Wall or ceiling-mounted electrical equipment
It has become increasingly common to mount heavy equipment such as TVs, speakers, flat screen installations etc on wall brackets, and to hang heavy luminaires, lighting track and projectors etc from the ceiling.
Plasterboard linings are not designed to carry such weights under fire conditions and, unless these items are fixed back onlyto the structural members in the wall or floor, they will pull down the linings once the board is weakened by the fire.
Weakening of normal and 'sound' grade plasterboard will occur rapidly after fire has consumed the room face paper lining and, whilst fibreglass-reinforced board will not fail quite as quickly or as dramatically, fixings will pull through it at a fairly early stage in the fire attack.
Obviously, early failure of these protective linings will allow fire attack on the studs and joists which again, if of engineered construction (see Annex A) will lead to premature structural failure.
All heavy equipment mounted on the face of walls or hung from the ceiling must be supported completelyindependently from the fire protective plasterboard linings. Whilst it may be permitted to fix directly to the joists, false ceiling members or studs, none of the fixings should rely solely on plasterboard.
If any additional fixings are needed beyond those that the structure is able to provide, then a section of the lining should be completely removed and the edges of the 'hole' fitted with supports to which 'both' edges of the plaster board can be fixed.
Additional structural members should then be fitted between joists and studs at the required fixing locations and the new plasterboard should be scribed, cut to size/shape and fixed in accordance with plasterboard manufacturers’ instructions, before fitting the suspended equipment. Joints between existing and new plasterboard linings should be filled and skimmed with plaster.
Guidance on what constitutes robust construction which identifies where unprotected downlighters may be fitted
When the installer wishes to fit unprotected** downlighters, it is necessary to establish the construction in detail and ensure that the floor is of one of the following constructions;
a) First floor of two-storey house:
• the joists are solid timber not less than 43 mm thick and at no more than 450 mm centres, and
• the floorboards above are either tongue and grooved softwood greater than 18 mm thick or are tight fitting butt jointed softwood boards free from dead knots, or is 'timber' based jointed flooring not less than 18 mm thick, and
• the ceiling consists of 12.5 mm plasterboard or 'sound' lath and plaster with the ‘hooks' in good condition.
If downlighters are installed in a compartment floor (or separating floor in Scotland – see Annex F), they must be protected** regardless of the construction.
b) All other floors in a single family unit:
• As for the first floor above, except butt jointed floor boards are not permitted without an overlay of medium density fibreboard (MDF), hardboard or plywood not less than 4 mm thick.
c) One hour fire resisting floors between flats:
• the joists are solid timber not less than 43 mm thick and at no more than 450 mm centres, and
• the floorboards above are either tongue and grooved softwood boards greater than 18 mm thick and free from dead knots, or is ‘timber’ based jointed flooring of a similar minimum thickness
• the ceiling consists of two layers of plasterboard, not less than 30 mm1 thick for non-fire rated board or not less than 25 mm thick of fire rated 1 & 2 board.
**Protected means downlighters that incorporate integral fire protection or which are fitted with fire hoods that comply with the guidance given in Annex E of this Guide. 1 Excluding any textured surface which should be removed locally prior to fitting the luminaire 2 Type 5 to BS 1230 or Type F to BS EN 520
Summary of the recommendations given in national regulatory fire safety guidance:
The requirements given in Table 1 and 2 of this Guide are the 'recommendations' made in the Guidance Document published in support of the relevant regional regulations. These Guidance Documents offer a prescriptive solution to the 'functionally' expressed regulations in the relevant region of the UK. At the time of publication, the relevant regional regulations that deal with the fire safety issues are:
England & Wales
The Building Regulations 2000
• Approved Document B
- Fire Safety (Volume 1) - Dwellinghouses (2006 Edition)
The Building (Scotland) Regulations 2004
• The Scottish Building Standards Technical Handbook Domestic (2007)
The Building Regulations (Northern Ireland) 2000, as amended
• Technical Booklet E, 2005
The above regulations apply only to new build, or to major refurbishments (material alterations) that are notified after the dates given. Buildings already constructed and/or occupied will have complied with the regulations and associated guidance in force at the time of application.
Test procedure to evaluate the robustness of downlighter fire hoods
This Annex provides requirements1 that need to be satisfied by a downlighter fire hood that is considered to be 'robust' in both its construction and fitting, and thereby meets the recommendations given in this Guide.
During installation, in order not to compromise the performance of the downlighter, it is essential that the area immediately above the downlighter and the fire hood remains free from thermal insulation (see 7.9). Subsequent to its installation, however, the fire hood needs to demonstrate its ability to remain in place and resist crushing, that is to be 'robust' in the event of any application of thermal insulation or other material by others.
The purpose of this test procedure is to assess the ability of a downlighter fire hood which has satisfied the fire test requirements of BS 476: Part 21: 1987 to retain its mechanical stability over its working life whilst providing the requisite level of fire protection to the structure of the buiding from a downlighter located beneath.
3. TEST PROTOCOL
The test protocol is a two part test.The first part deals with the ability of the specimen fire hood to resist compression after the application of the insulation within the test frame. The second part deals with the ability of the fire hood to resist dislodgement subsequent to installation.
4. TEST EQUIPMENT
The test assembly is designed to simulate a domestic ceiling. It consists of two softwood floor joists 225 mm x 47 mm x 1500 mm long held 450 mm apart, being screwed to similar sectioned timbers at either end.
The base of the test construction consists of a single sheet of 12.5 mm type plasterboard nailed to the underside of the timber framework. Two further sheets of 12.5 mm plasterboard 1500 mm x 300 mm are screwed to the inner face of the two major timber sections in a vertical position.
Midway down the length of the frame, a hole is cut in the centre of the plasterboard on the underside of the test frame. The size of the hole so cut should be equal to that formed in the ceiling to accommodate the downlighter that the fire hood is designed to protect.
A 1400 mm length of 400 mm wide mineral wool (24 kg/m3) is cut sufficient to provide an overall insulation depth of 270 mm within the test frame. The test assembly is held in position 2 m above ground level by the use of appropriate scaffolding.
5. TEST PROCEDURE
The specimen fire hood is located above the hole in the manner prescribed by the manufacturer. Unless the device is identified as being suitable only for installation from above, this will be positioned from below.
Once the specimen has been located in position, the distance between the top innermost part of the fire hood and the lower surface of the plasterboard of the main structure shall be measured in at least 3 places, averaged and noted (a).
Once this has been ascertained, the insulation described above is laid down the length of the test rig so as to be resting on the upper surface of the plasterboard and specimen.
At this point, the distance referred to above will be measured again (b). The insulation shall remain in place for 25 days. After this period, the distance referred to above will be measured once more (c).
Once the above distances have been ascertained, the insulation should be removed and the ‘dislodgement test’ should be undertaken on the same test specimen
5.2. Dislodgement test
One end of the test assembly will remain supported via a 'hinge', whilst the opposing end is progressively raised or lowered at a rate of 100 mm/sec until either:
a) the specimen fire hood becomes dislodged, in excess of the permitted amount or
b) the test assembly reaches an angle of 45 degrees.
In the case of the second measurement (b), a reduction in the average distance of less than 5%, or 5 mm (whichever is the smaller) is acceptable. For any reduction in excess of this figure, the specimen is deemed to have failed. In the case of the third measurement (c), there should be no further reduction in distance measured.
If the specimen moves laterally by more than 10 mm or a gap of 3 mm appears between the specimen and the top surface of the plasterboard prior to, or on completion of, the movement test, then the specimen will be deemed to have failed.
Glossary of terms
Equipment which distributes, filters or transforms the light transmitted by one or more lamps, and which includes all the parts necessary for supporting, fixing and protecting the lamps, but not the lamps themselves and, where necessary, circuit auxiliaries together with the means for connecting them to the supply.
An application where the consequences of a failure to provide the fire resistance requirements for an element will have a direct impact on the life safety of the occupants, e.g. between adjacent dwellings.
Known in Scotland as separating wall/floor.
‘Modified’ fire resistance–
In domestic applications the fire resistance of the first floor has a loadbearing capacity of 30 minutes, but the integrity and insulation criteria are reduced (modified) to only 15 minutes.
House in Multiple Occupation-
For England and Wales, the legal definition of a House in Multiple Occupation is to be found in Sections 254-260 and Schedule 14 of the Housing Act 2004 or, in the case of Scotland, the Civic Government (Scotland) Act 1982 (Licensing of Houses in Multiple Occupation) Order 2000 as amended.
‘Separating floor and wall’means in Scotland a floor or wall constructed to prevent the spread of fire between buildings or parts of buildings of separate habitation, such as flats and maisonettes.
Three-storey house: A house in single occupation with two floors above ground floor levels, often referred to as a town house.
House of four storeys, or more: A house that has three or more floors above ground floor where the height of the uppermost floor does not exceed 18 m.
Consumer unit replacement in domestic and similar premises
The aim of this Guide is to promote best practice by providing practical advice and guidance for designers, installers, verifiers and inspectors where the consumer unit or other main switchgear is being replaced in a domestic or similar premises wired in accordance with the Seventeenth Edition or earlier versions of the IET Wiring Regulations. The guidance is intended to protect customers and installers against dangerous situations that could arise from the existing installation.
The guidance recognises that the existing circuits being connected to a replacement consumer unit may not comply with the current edition of BS 7671 (as amended). In following the guidance, the installer accepts this and must be satisfied that all new work on a particular installation addresses the risks.
A consumer unit need not necessarily be replaced simply because it has rewireable fuses, cartridge fuses or older-type circuit-breakers, as these devices can provide satisfactory overcurrent protection. Similarly, a consumer unit need not be replaced because it does not incorporate Residual Current Device (RCD) protection, as there may be ways to provide this protection (where required) other than replacing the consumer unit. 2. Introduction
This Guide has been produced by Electrical Safety First in association with the bodies indicated on page 2. 3. Limitation
This guidance applies only to the replacement of a consumer unit, the reconnection of existing circuits and the connection of any new circuits installed during the work.
4. Legal requirements
There is no legal requirement that calls for an existing electrical installation to be upgraded to current standards.
However, there is a requirement under the Building Regulations for England and Wales to leave the installation and the building no worse in terms of the level of compliance with other applicable parts of Schedule 1 to the Building Regulations than before the work was undertaken. (Schedule1 gives the requirements with which building work must comply.)
Similarly, the Scottish Building Standards Technical Handbooks, which provide guidance on achieving the standards set in the Building (Scotland) Regulations 2004 (as amended), require that any work associated with the replacement of a service, fitting or equipment by another of the same general type is to a standard no worse than at present.
Replacing a consumer unit in domestic premises in England or Wales is notifiable work under the Building Regulations. Unless the work is undertaken by a person registered with an electrical selfcertification scheme prescribed in the regulations, notification of the proposals to carry out the work must be given to a building control body before the work begins, or, where the work is necessary because of an emergency, the building control body should be notified as soon as possible.
Installers are reminded of the need to comply with the relevant parts of the Electricity at Work Regulations 1989when replacing a consumer unit. In particular, attention is drawn to:
• regulation 12, Means for cutting off the supply and for isolation,
• regulation 13, Precautions for work on equipment made dead, and
• regulation 14, Work on or near live conductors.
These regulations mean that it will be necessary to make arrangements with the electricity supplier for the cut-out fuse to be withdrawn in order to disconnect the incoming supply for the purpose of isolation, unless a suitable isolating switch has been provided on the supply side of the consumer unit for this purpose. Guidance on safe isolation procedures is given in Best Practice Guide No 2.
5. Requirements of BS 7671
Replacing a consumer unit in an existing installation is an addition or alteration to that installation. The work must therefore be designed, erected and verified in accordance with the requirements of the current edition of BS 7671 (as amended), and must not impair the safety of the existing installation. (Regulations 110.1.2(vi) and 610.4 refer.)
BS 7671 does not require existing circuits to be upgraded to current standards in order for them to be connected to the outgoing ways of the replacement consumer unit.
However, circuits that are defective or non-compliant with the requirements of BS 7671 in a way that would result in immediate or potential danger must not be connected to the consumer unit.
Where a consumer unit is being replaced, additional protection by means of RCDs in accordance with Regulation 415.1 should be provided to the extent required by the current edition of BS 7671 (as amended), such as for:
• socket-outlets (Regulation 411.3.3 refers),
• mobile equipment for use outdoors (Regulation 411.3.3 refers),
• cables concealed in walls or partitions, where required by Regulations 522.6.101 to 522.6.103, and
• circuits of locations containing a bath or shower (Regulation 701.411.3.3 refers).
Circuits that are to be provided with RCD protection must be divided between a sufficient number of RCDs or otherwise designed as necessary to avoid hazards and minimise inconvenience in the event of a fault (Regulations 314.1 and 314.2 refer).
5.6The consumer unit must not be replaced until it has been established that:
• the rating and condition of any existing equipment, including that of the distributor, will be adequate for the altered circumstances, and
• the earthing and bonding arrangements necessary for the safety of the alteration or addition are also adequate. (Regulation 132.16 refers.)
Any defects found in the reconnected circuits must be recorded on the Electrical Installation Certificate covering the replacement of the consumer unit, as required by Regulation 633.2
6. Main earthing and bonding and meter tails
The installer must verify, as a minimum, that:
a) the main earthing terminal of the installation is connected to an adequate means of earthing via a suitably sized earthing conductor, (see notes 1, 2 and 5),
b) the main protective bonding is adequate, (see notes 3 and 5), and
c) the meter tails and the distributor’s equipment have adequate current-carrying capacity (see notes 4 and 5).
A measurement of the external earth fault loop impedance, Ze, should be carried out at this stage if practicable.
A 6 mm2 or 10 mm2 earthing conductor used with an associated line conductor of 25 mm2 could be considered adequate if the requirements of Regulation 543.1.3 are met.
A 6 mm2 main protective bonding conductor size could be deemed adequate where the minimum size required by Regulation 544.1.1 of BS 7671 is 10 mm2, if the bonding conductors have been in place for a significant time and show no signs of thermal damage.
16mm2 meter tails with a 100A cut-out fuse could be adequate if the maximum demand of the installation (taking into account diversity and load profile) does not exceed the current-carrying capacity of the tails, and also provided that the requirements of Regulation 434.5.2 for protection of the tails against fault current are met.
Some electricity distributors have requirements regarding the earthing conductor, main bonding conductors and meter tails that exceed the requirements of BS 7671.
If any of conditions 6.1 (a), (b) or (c) is not met, the customer should be informed that upgrading is required. If the customer refuses, the installer should not proceed with the replacement of the consumer unit.
7. Reason for change
The replacement of a consumer unit could be a planned change, as referred to in Section 7.2, or a distress change, as referred to in Section 7.3.
7.2. Planned change
The initial approach of the contractor planning the replacement of a consumer unit should be to encourage the customer to have an Electrical Installation Condition Report prepared on the installation in advance of the consumer unit being replaced.
If the customer refuses, a pre-work survey should be carried out to ascertain if there are any immediate or potential dangers, or any condition that would cause unwanted tripping of an RCD, in the existing installation affected by the change. As a minimum, the survey should include:
• making enquiries with the user as to whether there are any known defects, faults or damage,
• an internal visual inspection of the existing consumer unit to determine, amongst other things, the type and condition of the wiring system used for the installation,
• an external visual inspection of other readily accessible parts of the installation,
• a measurement of the external earth fault loop impedance, Ze,
• a test of circuit protective conductor continuity at the end of each final circuit, and
• an insulation resistance measurement of the whole installation at the consumer unit, between the live conductors connected together and the protective conductor connected to the earthing arrangement.
If any immediate danger, potential danger or condition that would cause unwanted tripping of an RCD is found, the customer should be informed that remedial work is necessary to improve safety.
Note. Immediate danger corresponds to one or more observations that would warrant a code C1 classification according to Best Practice Guide Number 4 in an Electrical Installation Condition Report. Potential danger corresponds to one or more observations that would warrant a code C2 classification.
Depending on the extent, the remedial work could involve considerable additional cost, not only in installing new cables or accessories, but also in the renewal of decorations, unless the customer is willing to accept surface wiring.
If the customer is unable, or not prepared, to accept either the cost or the disruption of the remedial works, but still requires a new consumer unit to be installed, the installer needs to carry out a risk assessment as described in Section 8 before agreeing to replace only the consumer unit.
Where cables are lead or rubber sheathed then deterioration of the cables is likely to necessitate rewiring.
7.3. Distress change
A distress change occurs when the consumer unit has suffered damage, has become unusable through overheating, or is in a dangerous condition with exposed live parts. This situation usually requires immediate replacement of the consumer unit. However, the installation of the consumer unit must still comply with the requirements of the current edition of BS 7671 (as amended). This means, amongst other things, that requirements a), b) and c) referred to in Section 6.1 must be met.
It should be explained to the occupant before the consumer unit is replaced that:
• if an immediately dangerous condition is found in an existing final circuit, it will not be possible to reconnect that circuit until remedial action is carried out, and
• it will be necessary to return to the installation to carry out any further work that would have been required if the replacement of the consumer unit had been planned. This further work, where required, must be carried out without delay.
Result of a DIY home owner having wired an 10.5 kW electric shower circuit with 2.5 mm2 cable and a 45 A circuit-breaker. (Photo courtesy of British Gas)
8. Risk assessment
As stated in Section 7.2.5, where it is proposed to replace a consumer unit but the customer is unable or unwilling to accept either the cost or disruption of the remedial works, a risk assessment should be undertaken. This is for the purpose of advising the customer as to the level of risk that would exist on completion of the proposed work. A disclaimer does not absolve the installer from responsibility.
In all cases, the initial approach should be to persuade the customer that remedial action should be taken to correct or remove any immediate danger, potential danger or condition that would cause unwanted tripping of an RCD.
The risk assessment requires inspection and testing (except to the extent these have already been carried out as part of the Electrical Installation Condition Report or pre-work survey mentioned in Section 7.2)
8.4. The inspection and testing are necessary to establish, for the circuits concerned, at least whether or not there are:
a) any immediate dangers (observations that would warrant a code C1 classification according to Best Practice Guide Number 4 in an Electrical Installation Condition Report),
b) any potential dangers (observations that would warrant a code C2 classification according to Best Practice Guide Number 4 in an Electrical Installation Condition Report), or
c) any lighting circuits that do not have a circuit protective conductor (cpc).
9. Action following risk assessment
If any immediately dangerous conditions are indicated (see paragraph 8.4(a)), the consumer unit should not be replaced unless the departures are corrected or the defective circuits are left disconnected from the replacement consumer unit.
If the risk assessment indicates that there are no immediately dangerous conditions (see paragraph 8.4(a)), the replacement of the consumer unit may proceed.
Any potential danger identified (see paragraph 8.4(b)) should be explained to the customer, and written confirmation given. A strong written recommendation should be made to the customer that remedial action is taken to correct any potentially dangerous conditions without delay.
If there are any lighting circuits that do not have a cpc (paragraph 8.4(c) refers), the recommendations of Best Practice Guide Number 1 (see 12.1) should be followed, as well as those of this guide. In some cases this may mean that the consumer unit should not be replaced unless certain works, recommended in Best Practice Guide Number 1, are carried out. Alternatively the circuits should not be connected to the replacement consumer unit.
10. Inspection, testing and certification
The alteration or addition itself (the installation of the replacement consumer unit and any other new work, such as additional final circuits) should be verified fully in accordance with the requirements of Section 610 of BS 7671 (as amended) and an Electrical Installation Certificate in accordance with BS 7671, detailing the work, should be given by the installer to the customer.
In addition, as a minimum, the following tests should be carried out to the existing circuits connected to the replacement consumer unit.
• A continuity test of the protective conductor of each circuit, to the point or accessory electrically furthest from the consumer unit and to each accessible exposed-conductive-part.
• A continuity test of all ring final circuit conductors.
• A measurement of the combined insulation resistance of all the circuits. The measurement need only be made between the line and neutral conductors connected together and the protective conductor connected to the earthing arrangement, to avoid potential damage to any electronic components.
• A test of the polarity and a test to establish the earth fault loop impedance (Zs), at each accessible socket-outlet and at least one point or accessory in every other circuit, preferably the point or accessory electrically furthest from the consumer unit.
Note: Testing of each RCD using both a test instrument and the integral test facility in the device should have been carried out under Section 10.1 of this Guide.
The Electrical Installation Certificate should identify in the comments section any potential dangers that exist with the reconnected circuits (code C2 items, see paragraph 8.4(b)) and other defects that exist in the reconnected circuits, and that the installation of the consumer unit has been carried out in accordance with the recommendations in this guide.
If a full Electrical Installation Condition Report on the installation has not been provided as part of the work, consideration should be given by the installer to stating this on the certificate with a recommendation this should be done.
The procedure described in this Best Practice Guide is summarised in the flowchart on page 9.
12. References to other Best Practice Guides
This Best Practice Guide makes reference to the following Best Practice Guides, which may be downloaded from the websites of some of the contributing organisations. The version on the Electrical Safety First website (www.electricalsafetyfirst.org.uk) will always be the latest.
• Best Practice Guide No 1– Replacing a consumer unit in domestic premises where lighting circuits have no protective conductor.
• Best Practice Guide No 2– Guidance on management of electrical safety and safe isolation procedures for low voltage installations.
• Best Practice Guide No 4– Electrical installation condition reporting: Classification Codes for domestic and similar electrical installations.
Test instruments for electrical installations: Accuracy and consistency
The aim of this Guide is to promote best practice by providing practical advice and guidance for electrical installers, verifiers, inspectors and other competent persons having responsibility for testing electrical installations.
To comply with Regulation 612.1 of BS 7671, test instruments must be selected according to the relevant parts of BS EN 61557 or, if not, they must provide an equivalent level of performance. BS EN 61557 requires compliance with the safety requirements of BS EN 61010.
Test instruments must be of a category appropriate to the overvoltages likely to be encountered. The categories are shown in the diagram in Annex 1.
BS 7671 does not require regular calibration of test instruments. However, in order to maintain confidence in the accuracy of all test instruments used for initial verification and condition reporting purposes, those responsible for testing should put in place an effective system to confirm and record their continuing accuracy and consistency, so that remedial action can be taken without delay if there is any indication that an instrument is no longer sufficiently accurate.
It is important to be confident that test instruments are accurate and remain consistent. Instruments may become inaccurate for a number of reasons, such as being dropped or having a heavy object fall against them in the back of a van. In some cases, an instrument itself may remain accurate but its test leads can become loose or dirty, thereby affecting the measurements.
This guidance applies to test instruments intended for use on installations operating at a nominal voltage not exceeding 1000 V a.c. or 1500 V d.c.
It is important to establish the accuracy of a new or repaired instrument as this establishes a reference point.
The initial accuracy of a new or repaired instrument is usually confirmed by calibration. However, a new or repaired test instrument may not be supplied with a calibration certificate unless specifically requested.
An instrument may be supplied with a Certificate of Conformity. This indicates that the accuracy of the instrument was verified as part of the manufacturing process. The verification will generally follow the same procedure as calibration, but individual calibration data is not issued.
Following the confirmation of initial accuracy, it is important to check and maintain continuing accuracy.
It is also important to treat test instruments and associated test leads and accessories with care. Many instruments are now provided with a cushioned box that helps protect them against mechanical damage.
SYSTEMS FOR CONFIRMING ONGOING ACCURACY AND CONSISTENCY
Whichever system is used for confirming the ongoing accuracy and consistency of test instruments, it is the responsibility of the user to ensure that the system provides confidence in the test results used to verify or confirm the safety of an electrical installation.
Formal calibration/recalibration by a third party A system for confirming the ongoing accuracy of test instruments could simply consist of maintaining records of the formal calibration/recalibration of the instruments at the intervals recommended by the instrument manufacturers, supported by calibration certificates issued by recognised organisations with measurements traceable to national standards. Calibration certificates issued by laboratories accredited by the United Kingdom Accreditation Service (UKAS) are preferable.
Calibration involves checking whether or not an instrument is still operating within the manufacturer’s specification and, if not, making adjustments to bring the instrument back within specification. The test leads used with the instrument should be submitted with it.
However, given the arduous conditions in which test instruments often have to be used, such a formal calibration system cannot provide any assurance of continuing accuracy over the period (typically one year) between the calibration checks.
Many instruments used for electrical installation testing will be in regular use and be frequently transported from site to site. Should an instrument be found to be inaccurate when sent for say an annual calibration check, numerous inaccurate results may have been recorded on test schedules. This could potentially require extensive retesting to ensure that no dangerous conditions exist in installations tested with that instrument since the previous calibration check.
Therefore, when submitting an instrument for calibration, the user should ask to be advised if it was found to be inaccurate.
In-house systems To avoid the problems that might arise if an instrument becomes inaccurate following initial or subsequent certification of conformity or calibration, ‘in-house’ systems of the type recognised by electrical contractor assessment bodies might be considered desirable.
Such in-house systems, however, can only provide a measure of confidence in the consistency of test measurements over time. The accuracyof each instrument needs to be confirmed before any reliance can be placed in such systems.
The frequency of ongoing accuracy checks will depend upon how often the instruments are used, how they are maintained and experience of the results of previous checks.
Where an instrument is used by one operative, the operative should be able to maintain some control over it. But where instruments are issued to different operatives on a regular basis, there may be less control. In such cases, it would be prudent for a consistency check to be made at the time of handover.
Proprietary checkbox One recognised in-house system for checking ongoing consistency uses a proprietary checkbox. Such checkboxes are available from most instrument manufacturers and provide a checking facility for a range of test instruments: provision for continuity, insulation resistance, earth fault loop impedance and RCD tests being typical.
There are a number of proprietary checkboxes on the market, some providing more comprehensive checks than others.
Where a checkbox does not check the voltage of an insulation resistance test instrument or the open circuit voltage and short circuit current of a continuity test instrument, these checks should be made using other test instruments.
The output voltage of an insulation resistance test instrument should be not less than the range selected, when measured with a voltmeter.
The open circuit voltage of a continuity test instrument should be between 4 V and 24 V when measured with a voltmeter, and the short circuit current should be not less than 200 mA when connected to an ammeter set to an appropriate range.
If the checkbox is unable to check a loop impedance or RCD test instrument, the instruments should be checked using another system.
Consideration should be given to having checkboxes calibrated at appropriate intervals.
Comparative cross-checks Another system is to maintain records over time of comparative cross-checks with other test instruments used by the organisation.
Where an organisation has more than one set of test instruments, comparative cross-checks on one instrument can be made using another test instrument.
In this case, the cross-checking procedure used should be recorded to help ensure that a consistent method is adopted and that all instruments are regularly checked.
It would be also prudent to check that: • the output voltage of an insulation resistance test instrument is not less than the range selected, when measured with a voltmeter, and • the open circuit voltage of a continuity test instrument is between 4 V and 24 V when measured with a voltmeter, and the short circuit current is not less than 200 mA when connected to an ammeter set to an appropriate range.
Larger businesses might decide to reserve a set of regularly calibrated instruments for use as the standard against which other sets of instruments are compared.
Designated reference circuits or devices A third in-house system for checking ongoing consistency is to maintain records over time of measurements of the characteristics of designated reference circuits or devices. This system is the least preferable in terms of confirming the full range of test instrument functions.
For continuity and insulation testing, this system uses good quality resistors for both low-resistance ohmmeters (for continuity testing) and high-resistance ohmmeters (for insulation resistance testing). The choice of resistors should reflect the expected range of the instruments in question.
For example, for a low-resistance ohmmeter consistency checks, there should be at least one resistor below 0.5 Ω and another between 0.5 Ωand 1.0 Ω, as values in this range are common. If the continuity test instrument has more than one range, additional resistors should be selected to test the higher ranges.
Check resistors for high-resistance ohmmeters should at least take account of the requirements of Part 6 (Table 61) of BS 7671 and for this 0.5 MΩand 1.0 MΩ resistors will be required, rated at at least 1000 V. However, as the measured insulation resistance values for new electrical installations are expected to be much higher than the minimum values permitted by BS 7671, additional check resistors should be selected (for example a 10 MΩand 100 MΩresistor) for the higher insulation resistance ranges.
Note: The above check resistor values are indicative only
For checking the ongoing consistency of loop impedance test instruments, a designated socket-outlet on a nonRCD-protected circuit should be used for the check. The value of earth fault loop impedance at the socket-outlet may vary as a result of network conditions (load etc), but regular monitoring will quickly establish whether such variations are significant or not. The expected earth fault loop impedance value should be marked on or adjacent to the socket-outlet designated for the checks, or recorded in the instrument accuracy logbook.'
For ongoing checks of residual current device test instruments, a designated RCD-protected socket-outlet can be used. As with the arrangement for loop impedance checks, the expected tripping times should be marked on or adjacent to the designated socket-outlet, or recorded in the instrument accuracy logbook.
For all low voltage electrical installation verification and condition reporting work, electrical contractors and installers should, as a minimum, have the following range of test instruments:
• Continuity test instrument • Insulation resistance test instrument
• Loop impedance test instrument
• Residual current device test instrument
• Earth electrode resistance test instrument*
• Suitable split test leads for both the loop impedance test instrument and the residual current device test instrument.
• Voltage indicating instrument** *
Alternatively, an earth fault loop impedance test instrument may be used. There is no commonly available alternative for confirming the accuracy of an earth electrode resistance test instrument other than calibration, although it is feasible to construct a test box for this purpose.
** Voltage indicating equipment does not require calibration
Two or more of the functions of the above test instruments may be combined in a single instrument.
MAINTAINING RECORDS OF ON-GOING ACCURACY AND CONSISTENCY
Whichever method of confirming on-going accuracy is adopted, the results should be documented for record and audit purposes.
Each test instrument should be clearly and uniquely identified for record and traceability purposes. Annex 2 shows a typical form for recording monthly accuracy checks.
SELECTION OF TEST INSTRUMENTS FOR GIVEN TESTS
Test instrument manufacturers will state to which standard their instruments conform.
BS EN 61557is entitled Electrical safety in low voltage distribution systems up to 1000 V a.c. and 1500 V d.c. Equipment for testing, measuring or monitoring of protective measures. This standard includes performance requirements and requires compliance with BS EN 61010.
BS EN 61010: Safety requirements for electrical equipment for measurement control and laboratory use is the basic safety standard for electrical test instruments.
Voltage detection instruments should conform to BS EN 61243-3: Live working - Voltage detectors - Twopole low voltage type.
BS EN 61557consists of a number of parts, some of which are indicated below:
SOURCES OF MEASUREMENT ERRORS
Sources of error that can affect the overall accuracy of a test measurement, and even the ability to make a meaningful measurement, vary considerably.
Much depends on:
• the type of measurement being made
• the effectiveness of the connections between the instrument and the circuit to be tested.
Measurement errors can arise from, amongst other things:
• poor probe contact
• poorly nulled test leads
• weak crocodile clips
• faulty (intermittent) leads
• leads other than those supplied with the instrument. Some examples of common errors for different types of measurement are detailed below:
• Condition of test lead connectors– Poorly maintained, old or worn connectors can add significant error and variability to a result. Test leads do wear out
• Resistance of the test leads– The effect of test lead resistance (including any fuses) can be removed by the nulling (zeroing) facility provided by many test instruments
• Probe contact resistance– This will depend on the condition of the probe tips and that of the material to which they are connected, and the pressure applied
• Crocodile clips– One side of a clip may have a lower resistance than the other, the hinge creating the higher resistance path. This can be an issue both when nulling and when attaching the clips for measurement
• In-circuit components- Neons, electronic components etc can significantly affect insulation resistance values.
Loop impedance testing
• Contact resistance – low loop impedance measurements are affected in the same manner as continuity measurements
• Mains noise or disturbance– Non-trip loop tests frequently use low test currents (15 mA) for testing RCD-protected circuits. These tests are susceptible to noise or mains disturbances, which may create variation in the results. If there is any concern about the result, the test should be repeated
• Low loop impedance values and prospective fault current calculations– When measuring close to a transformer or other low impedance source, loop impedance values can be very low, typically less than 0.1 Ω. As prospective fault current values are generally derived from the loop impedance measurements either directly by instruments or by manual calculation, small variations in the measurement of loop impedance values may result in significant differences in prospective fault current indications or calculations. In such cases, it may be necessary to use an alternative method of determining prospective fault current other than by a loop impedance test instrument.
• Instrument accuracy and resolution Where circuits do not incorporate RCD protection, earth fault loop impedance measurements should be made using the higher test current range (up to about 25 A). A displayed test result less than about 0.2 Ωcould be prone to significant errors. Such errors can significantly affect the calculation of prospective fault current. On the low current range (such as 15 mA), displayed test results less than about 1.0 Ωcould be prone to significant errors. Such errors can significantly affect the calculation of prospective fault current.
• Earth leakage currents- can affect the trip times of RCDs, by adding to the RCD test current
Additional information on sources of error
Additional information on sources of error can often be found in the product user guide or should be available from the instrument manufacturer.
Annex 1 Impulse withstand categories
Annex 2 Typical form for recording monthly instrument accuracy checks (Courtesy Certsure)
Selection and use of plug-in socket-outlet test devices
The Health and Safety Executive (HSE) has expressed concerns about instances where simple* socket-outlet test devices have been relied on to demonstrate that socketoutlets are ‘safe’, either as part of the initial verification of newly-installed socket-outlets, or for the periodic testing of existing socket-outlets. This guidance is intended to address those concerns.
No socket-outlet test device (however sophisticated) can be relied on alone to provide full assurance that a socket outlet is safe to use. This guidance therefore covers not only simple socket-outlet test devices but also those of more advanced designs.
The guidance is intended to supplement the information provided with socket-outlet test devices, which must always be read and followed in order to ensure that the device is used safely and correctly. The guidance is intended for skilled persons competent in electrical testing only.
There are a number of proprietary plug-in devices on the market that are designed to give a quick and easy indication of the electrical condition of socket-outlet circuits.
Although all these devices will indicate some of the basic electrical faults that may be found in socket-outlet circuits, the simpler versions cannot be relied on to indicate certain other faults, some of which can be dangerous.
Furthermore, no socket-outlet test device, including an advanced or professional device, can alone provide full assurance that a socket-outlet is safe to use. For example, none can detect an open ring final circuit, a loose electrical connection, a case of unsatisfactory insulation resistance of circuit conductors, or a reversal of the neutral and protective conductors.
Similar advice applies if a socket-outlet test device is used to test an extension lead.
A further fault that most types of socket-outlet test device cannot detect is a reversal of the line and PEN conductors within the incoming electricity supply to the premises, if the installation forms part of a TN-C-S system. The reason why this potentially dangerous fault cannot be detected by the test device is that the voltages ‘seen’ by the device between the various contacts of the socket-outlet are unaffected by a reversal in the polarity of the supply, as shown in Fig 1.
Fig 1. Reversal of polarity in the supply in a TN-C-S system
Types of socket-outlet test device
There are three types of socket-outlet test device: simple, advanced and professional. Examples are depicted below.
Simple devices are designed to detect various faults. However, they cannot indicate or make any measurement of the effectiveness of the protective earthing (the earth fault loop impedance), or identify some other dangerous faults.
Advanced and professional devices are designed to detect a wider range of faults, and can indicate or measure the effectiveness of the protective earthing.
These advanced and professional devices display either the range of numerical values into which the earth fault loop impedance falls or the numerical value of the loop impedance. This information must be interpreted by the user of the socket-outlet test device to determine whether or not the socket-outlet is adequately earthed for safety.
The interpretation process requires knowledge of the maximum value of earth fault loop impedance allowed for the protective device that is relied on to provide automatic disconnection in the event of an earth fault. The maximum value depends on the type and rating of the protective device.
Simple socket-outlet test devices
Simple socket-outlet test devices are usually similar in size and appearance to a 13 A plug and typically cost less than £20 each.
They are useful devices because they will generally indicate whether a socket-outlet is functional and are able to detect certain faults, including, in most cases, reversed live and earth connections or the absence of an earth, which can be very dangerous faults.
However, although simple test devices are able to detect the absence of an earth, they are unable to measure the earth fault loop impedance at the socket-outlet and might therefore imply that it is safe to use even where the earthing is dangerously defective.
This very important fact might not be stated on simple test devices or the associated packaging or instructions, and is also not known by many users of such devices. Simple socket-outlet test devices can therefore very easily mislead the user into believing a socket-outlet is acceptably safe when it is not. If the test device does not display either the numerical value of earth fault loop impedance or the range of numerical values into which the loop impedance falls, then it is a simple socket-outlet test device and must not be relied upon to indicate whether a socket-outlet is safe to use.
This is because the test device cannot verify that certain critical safety requirements of BS 7671 are being met, including the adequacy of the protective earthing.
HSE investigations into simple socket-outlet test devices
The HSE tested a sample of simple socket-outlet test devices after an HSE electrical inspector observed various instances where such devices were being used inappropriately.
In two instances where simple socket-outlet test devices had been used to demonstrate to an inspector that socket-outlets in installations forming part of a TN-C-S system were adequately earthed, the inspector found with a professional socket-outlet test device that the earth fault loop impedances at the socket-outlets were 22 Ωand 218 Ωrespectively.
Such impedances are far in excess of the maximum values providing automatic disconnection of supply by means of the circuit overcurrent protective device in the event of an earth fault.
Tests undertaken by HSE showed that simple socket-outlet test devices would not indicate a problem unless the earth fault loop impedance exceeded very high values, which could be in excess of 20,000 Ω.
Advanced socket-outlet test devices
Advanced socket-outlet test devices typically cost between £50 and £100.
These devices are more complex than simple ones because they use additional components and technology to determine and indicate earth fault loop impedance. The ease of using advanced devices is intended to encourage more frequent checking of this very important parameter.
They have all the normal check functions of simple test devices, including reversed line and earth or reversed line and neutral.
An advanced device displays the range of numerical values into which the earth fault loop impedance falls. However, there can be cases where this information is not sufficiently precise to indicate whether a socket-outlet is adequately earthed for safety. This depends on the particular range of values and the type and rating of the protective device that is relied on to provide automatic disconnection of supply in the event of an earth fault.
Professional socket-outlet test devices
Professional socket-outlet test devices typically cost several hundreds of pounds. These devices meet the requirements of BS EN 61557-3. They usually take the form of an earth fault loop impedance test instrument used in conjunction with a lead equipped with plug to suit the socket-outlet that is to be tested. These devices display the numerical value of the earth fault loop impedance rather than a range of numerical values into which the measurement falls.
Comparison of capabilities of the different socket-outlet test device types Table 1 summarises the capabilities of the three different types of socket-outlet test device covered in this guide.
Training for users of socket-outlet test devices
Users of socket-outlet test devices should be trained to:
• use the socket-outlet test device correctly and safely
• know the capabilities and limitationsof the different types of socket-outlet test device
• understand the types of fault that can be present at a socket-outlet
• identify the means by which the electrical installation is earthed (for example, through an earth terminal provided by the electricity distributor (TN system) or through earth rods (TT system)
• know what earth fault loop impedance means, and what values of earth fault loop impedance are acceptable
• determine whether or not RCD protection is present or should be provided
• know when to take further action.
Initial verification or testing after maintenance
New, repositioned or replaced socket-outlets should not be put into service until the required verification procedures have been completed and it has been established that the requirements of BS 7671 have been met. (Regulation 134.2 refers.)
In particular, for new work, it is unsafe and therefore unacceptable to energise a socket-outlet final circuit and then to plug in a socket-outlet test device to check for basic wiring faults.
Condition Reporting (Periodic Inspection Reporting)
For condition reporting, inspection comprising careful scrutiny and the appropriate tests of Chapter 61 of BS 7671 should be performed.
The appropriate tests on a socket-outlet would normally consist of protective conductor continuity or ring final circuit continuity, insulation resistance, polarity, earth fault loop impedance and functionality, including the correct operation of any RCD protecting the socket-outlet.
Socket-outlet test devices are useful because they will generally indicate whether a socket-outlet is functional. They are able to detect certain faults, including, in most cases, reversed live and earth connections, which can be very dangerous.
There are three types of socket-outlet test device: simple, advanced and professional.
Although all three types will indicate some of the basic electrical faults that may be found in socket-outlet circuits, the simpler versions cannot make any measurement of the effectiveness of the protective earthing or indicate certain other faults, some of which can be dangerous.
Simple socket-outlet test devices can also very easily mislead the user into believing that a socket-outlet is adequately earthed by showing ‘Earth OK’ or similar indication even when the earth fault loop impedance is in excess of 20,000 Ohms.
If a socket-outlet test device cannot display the earth fault loop impedance, it should not be used to check whether a socket-outlet is adequately earthed for safety.
If a socket-outlet test device can display the range of numerical values into which the earth fault loop impedance falls, it may still be necessary in some instances to obtain the numeric value (using a professional socket-outlet test device) to confirm that a socket-outlet is adequately earthed for safety.
No socket-outlet test device (however sophisticated) can be relied on alone to provide full assurance that a socketoutlet is safe to use.
The only means of checking whether a newly installed socket-outlet is safe to put into service, or of determining whether an existing socket-outlet is safe to continue in service as part of a formal electrical installation condition report (periodic inspection report) on the installation, is to follow the inspection and testing procedures set out in Part 6 of BS 7671, using a full set of test instruments complying with the relevant parts of BS EN 61557.
Safe installation of retrofit LED lamps
This Guide has been produced by Electrical Safety First in association with the bodies indicated on Page 2.
Lamps containing light emitting diodes (LEDs) are becoming the increasingly dominant light source of choice for industrial, commercial, amenity and more latterly domestic lighting following the arrival of compact, high luminous efficacy white light types having a very long operating life (if installed correctly).
The continued development of ever more efficient LED light sources, coupled with the relative ease of controlling brightness and even colour output has resulted in further development of the fluorescent lamp to virtually cease. It is inevitable therefore that the use of LED lighting will continue to grow in the years to come.
The introduction of LED lighting brings with it an increasing number of products onto the UK market available for sale not only from more conventional outlets such as wholesalers and DIY stores but also from a range of sources via the internet. Whilst many of the LED lamps available for purchase are of an acceptable quality,there are a number of safety concerns relating to some readily available products. These concerns relate typically to the risk of electric shock occurring during installation, maintenance or inspection and testing work. As with any other lamp type, there is also the possibility of a poor quality LED lamp or luminaire causing a fire.
Ever more innovations and advancements are being made in the field of LED lighting and currently these precede somewhat the development of standards for such products. However, a number of product standards are now available while others are currently still in production, nevertheless specifiers and users of LED lighting need to be aware of the risks that poor quality products and incorrect installation may present. The Lighting Industry Association (LIA) Technical Statement TS01 gives details of National, European and International Standards and guidance covering LED lighting products that have been published or which are under development.
The aims of this guide are to • Highlight potential dangers and risks associated with the • Use of self-ballasted LED lamps designed as a direct replacement for tungsten filament, compact fluorescent and similar lamps • Conversion of fluorescent luminaires to work with self-ballasted LED lamps and their subsequent use and maintenance • Promote best practice by providing practical advice and guidance on how best to deal with the potential hazards and risks listed above.
This guide does not consider issues such as energy efficiency or lighting design performance.
3. Installation of LED lighting
In general LED lamps may be installed:
• In luminaires designed specifically for use with LEDs
• In existing lampholders or light fittings as a replacement of less efficient lamps
• In an existing fluorescent luminaire either as a retrofit lamp replacement or following conversion of the luminaire.
4. Replacement of conventional lamps
A range of LED lamps having integral controlgear, defined in BS EN 62560: 2012 - Self-ballasted LED - lamps for general lighting services by voltage > 50 V — Safety specifications as self-ballasted LED lamps are available as a direct replacement for 230 V lamps1 having a wide range of lamp caps, including bayonet cap, Edison screw cap2, plug-in G-type caps3, GZ10 and GU10 pins.
Electric shock risk Clause 4.1 of BS EN 60968: 2013 - Self-ballasted lamps for general lighting services - Safety requirements states that self-ballasted lamps shall be so designed and constructed that in normal use they function reliably and cause no danger to the user or surroundings.
Whilst the use of high quality LED replacement lamps should not present an electric shock risk, there have been a number of cases where lamps have been found on the market that have exposed live parts on the accessible faceplate of the lamp. This clearly presents a direct contact electric shock risk during lamp replacement or if the face of the lamp is touched for any reason when the supply to the lighting circuit is on.
In research, carried out on behalf of Electrical Safety First, touch voltages were measured for normal and reverse polarity between Earth and the accessible LED leads and solder contacts that might reasonably be touched during insertion or removal of the lamps.
The results are shown in Table 1. The full laboratory test report relating to this research can be downloaded free of charge from the ‘Electrical professionals’ section of the Electrical Safety First website.
Where test results are shown in red in Table 1 this indicates a non-compliance with Clause 7 of BS EN 62560 which requires lamps to be so constructed that, without any additional enclosure in the form of a luminaire, no internal metal parts, basic insulated external metal parts or live metal parts of the lamp cap or of the lamp itself are accessible when the lamp is installed in a lampholder.
1 Unit which cannot be dismantled without being permanently damaged, provided with a lamp cap and incorporating a LED light source and any additional elements necessary for stable operation of the light source
2 Lamps with E11, E12, E17 and E26 caps are excluded from the scope of EN 62560:2012 as they do not comply with European safety requirements
3 G24, G23, 2G7, 2G10, 2G11, etc.
Where the source of supply for the LED lamp does not meet the requirements for the protective measure separated extra-low voltage (SELV), the lamp should be of Class II construction (See BS EN 60598-1: 20084 - Luminaires - General requirements and tests).
Fig 2 Example of LED lamp having exposed live contacts that are possible to touch on the sides
One way of avoiding such risks is to choose lamps having the component parts on the faceplate encapsulated in an insulating material.
Fig 3. Example of LED lamp having encapsulated live parts on surface that is accessible with lamp installed. Image courtesy of Osram.
Alternatively lamps having an integral lens in front of the component parts may be chosen.
Fig 4. Example of LED lamp having an integral lens. Image courtesy of Megaman UK.
It is highly recommended that the supply to the relevant circuit is switched off or the lamp/luminaire is unplugged before removing or replacing LED lamps, which is good practice for all relamping exercises.
A number of lamps available on the market in the UK are so manufactured that they can be easily disassembled, without the use of tools, such that access to live parts is possible.
Fig 5. Example of LED lamp that can be easily disassembled to allow access to live parts
Clause 9.1 of BS EN 62560 specifies torque levels at which a lamp cap shall remain firmly attached to the bulb or that part of the lamp which is used for screwing the lamp in or out for bayonet cap and Edison screw lamp caps. However, during testing commissioned by Electrical Safety First5, it was found that in some cases, merely applying a turning force which is reasonable to remove a lamp from a lampholder was sufficient to cause the lamp body to separate from the lamp cap, permitting access to internal components. In some cases, this was because the bond between the lamp body and lamp cap broke. In other cases, the lamp body merely unscrewed from the lamp cap.
Currently no torque values are stated for a number of other lamp caps, including GU10 type, but specification of such values is under consideration.
Fig 6. Example of where body of LED lamp has separated from lamp cap when force representative of that required for lamp replacement is applied allowing access to live parts
A number of cases have been recorded of dramatic lamp failure where component parts have fallen from the lamp causing a fire.
In January 2013 an investigation of a fire that resulted in a fatality concluded that the most likely cause of the fire was a faulty self-ballasted LED lamp. This fault resulted in burning debris falling onto a bed immediately below the light fitting in which the LED lamp was housed, setting fire to the bedclothes. It is unclear whether the fault in the lamp was due to the failure of a capacitor or as a result of heat produced by a high resistance soldered connection in a printed circuit board, the resultant heat build-up either igniting the plastic barrel of the lamp or possibly causing the failure of the adjacent capacitor.
Fig 7. Parts of damaged LED lights found within the remnants of a bed deemed to be the source of fire that resulted in a fatality. Note the remains of an aluminium heatsink melted onto one of the mattress springs. Image courtesy of London Fire Brigade.
Clause 11 of BS EN 62560 states that external parts of insulating material providing protection against electric shock, and parts of insulating material retaining live parts in position shall be sufficiently resistant to heat.
In the fatal fire incident mentioned above, the most severely damaged of the three GU10 LED lamps in the luminaire above the bed had, as a result of heat damage, lost the envelope, heat sink and control printed circuit boards (PCBs) all of which had fallen onto the bed. (See Fig 7).
Fig 8. Luminaire after fatal fire. The remains of the plastic body of the lamp can be seen protruding from the body of the luminaire. Image courtesy of London Fire Brigade.
This incident highlights the need to purchase lamps that meet the requirements of relevant product standards such as BS EN 62560.
5. Conversion of fluorescent fittings
There is a Publically Available Specification (PAS 62776 – Double-capped LED lamps for general lighting services – safety specifications) covering the safety of double-capped LED lamps for general lighting services. This can be used whilst a full standard is being developed. This will include the requirements for double-capped ‘retrofit’ LED lamps designed for use with unmodified linear fluorescent luminaires.
Once the standard is published it will provide a presumption of conformity with the Low Voltage Directive, (limited to its scope and the relevant requirements that are covered).
Retrofit is a term that generally covers the replacement of a component with a component of a different type – i.e. changing from a linear fluorescent lamp to a linear LED lamp. Sometimes there is little or no modification required to the original luminaire. Other times there is a considerable modification required to the internal wiring. This can lead to unsafe situations if the work is not carried out by skilled/competent persons.
A summary of compatibility between self-ballasted LED tubes and modified or unmodified fluorescent lamp luminaires is given in Table 2.
IEC document 34/221/INF contains a more complete risk analysis of the various possible combinations of wiring arrangements found in luminaires and the various LED tube lamp types that are available.
Luminaires incorporating wire wound (electromagnetic) control gear
In most cases, switch-start fluorescent luminaires incorporating wire wound (electromagnetic) control gear can be altered relatively simply to permit use with ‘retrofit’ LED lamps. This is achieved by the replacement of the original starter switch followed by the installation of an LED ‘starter’ and double-capped self-ballasted lamp. Some LED lamp manufacturers state that there is no need to modify the luminaire or the controlgear therein in any way. Other manufacturers state that the ballast and power factor correction capacitor of the luminaire should be disconnected to achieve maximum efficiency.
Fig 9. Example of LED tube and replacement for starter switch that may be used to replace a fluorescent tube in a switch-start fluorescent fitting. Images courtesy of Philips.
It is recommended that LED tubes are selected which may be installed, in conjunction with the associated replacement starter, without the need for any further modification of the luminaire.
The draft BS EN 62776 proposes that double-capped LED lamps suitable for use with magnetic ballasts should be marked with the symbol shown in Fig 10.
Fig 10. Double-capped LED lamp suitable for 50 Hz or 60 Hz operation.
The draft BS EN 62776 also proposes that where double-capped LED lamps need to be used in conjunction with components replacing a starter switch, the type reference of the replacement starter shall be marked on the lamp and that the LED replacement starter shall be marked as shown in Fig 11.
Fig 11. LED replacement starter marking.
High frequency luminaires
Fluorescent luminaires having electronic ballasts can also be converted to accept linear LED lamps. However, in most cases the installer must bypass the electronic ballast completely and wire directly to the lamp contacts.
Such conversion presents a number of issues:
• The original manufacturer of the luminaire will no longer be seen as responsible for the safety of the product unless they specifically agree that this is the case.
• The modifications made may adversely affect the safety of the luminaire. For example, in the case of ‘Ex’ certified equipment for use in potentially explosive atmospheres the person who carries out the conversion will need to obtain third party certification of the modified product to the relevant standard.
The manufacturer, importer, distributor and retailer involved in the sale of LED lamps for use in fluorescent luminaires have a responsibility to ensure that when the conversion kit is installed the modified luminaire is safe and complies with the safety requirements of the Low Voltage Directive (LVD).
The person carrying out the conversation will have a responsibility to
• carry out a conformity assessment on the converted luminaire
• produce appropriate technical documentation • provide a declaration of conformity, and
• ensure the application of CE marking to the luminaire.
A more in-depth discussion of the post-production modification of lighting products is given in Technical Statement TS25 published by the Lighting Industry Association.
At least one manufacturer now offers an LED tube that is compatible for use with luminaires having electronic ballasts without the need for any conversion to the luminaire.
Electrical Safety First recommends the use of such lamps in preference to those that require modification of the luminaire.
High frequency luminaires
Fluorescent luminaires having electronic ballasts can also be converted to accept linear LED lamps. However, in most cases the installer must bypass the electronic ballast completely and wire directly to the lamp contacts.
Such conversion presents a number of issues:
• The original manufacturer of the luminaire will no longer be seen as responsible for the safety of the product unless they specifically agree that this is the case.
• The modifications made may adversely affect the safety of the luminaire. For example, in the case of ‘Ex’ certified equipment for use in potentially explosive atmospheres the person who carries out the conversion will need to obtain third party certification of the modified product to the relevant standard.
The manufacturer, importer, distributor and retailer involved in the sale of LED lamps for use in fluorescent luminaires have a responsibility to ensure that when the conversion kit is installed the modified luminaire is safe and complies with the safety requirements of the Low Voltage Directive (LVD). The person carrying out the conversation will have a responsibility to
• carry out a conformity assessment on the converted luminaire
• produce appropriate technical documentation
• provide a declaration of conformity, and
• ensure the application of CE marking to the luminaire.
A more in-depth discussion of the post-production modification of lighting products is given in Technical Statement TS25 published by the Lighting Industry Association. At least one manufacturer now offers an LED tube that is compatible for use with luminaires having electronic ballasts without the need for any conversion to the luminaire. Electrical Safety First recommends the use of such lamps in preference to those that require modification of the luminaire.
The draft BS EN 62776 proposes that double-capped LED lamps suitable for use with electronic ballasts should be marked with the symbol shown in Fig 12.
Fig 12. Double-capped LED lamp suitable for high frequency operation.
Potential hazards associated with conversion of luminaires
In some cases, the pins at one end of a doublecapped linear LED lamp can be hazardous-live when the pins at the other end of the lamp are installed in the lamp cap of a luminaire (See Figs 13, 14 and 15 and Table 2 of this guide). This is unacceptable. Lamps presenting this shock risk should not be used. Indeed, such lamps should not be for sale.
Fig 13. Simplified circuit diagram of one type of double capped LED linear lamp available for purchase.
With this configuration, if the lamp is installed into a luminaire providing both line and neutral to one end of the lamp, the pins at one end of tube will be hazardous-live when the pins at other end of tube are engaged in the lampholder whilst circuit is still energised. See also Figs 14 and 15.
Fig 14. Luminaire wiring typically found after modification of a fluorescent luminaire. In this configuration and this type of LED lamp installed the pins at one end of tube will be hazardouslive if pins at other end of tube are engaged in the lampholder whilst circuit is still energised.
Fig 15. Luminaire wiring typically found after modifying an electronic ballast luminaire with ballast bypassed.
In this configuration and this type of LED lamp installed the pins at one end of tube will be hazardous-live if pins at other end of tube are engaged in the lampholder whilst circuit is still energised.
If a fluorescent lamp is inadvertently installed in an energised luminaire that has been converted for use with LED lamps there is a possibility of violent rupturing of the cathodes at the tube ends at the moment of insertion. Although possibly insufficient to break the glass wall of the lamp, it may invoke a surprise reaction that could result in injury from, say, a fall from access equipment during relamping.
In an effort to avoid such a potentially dangerous situation occurring, it is recommended that a label is affixed in a position visible to persons performing relamping, stating which types of lamp are suitable for use with the luminaire.
The conversion of electronic ballast luminaires is not recommended. However if such luminaires are converted, the work must be carried out by suitably competent persons taking account of the recommendations of the LED lamp manufacturer.
Emergency lighting luminaires
Care must taken when making any modifications to a luminaire containing a lamp on an emergency lighting circuit such as replacing a fluorescent lamp with a linear LED lamp. Because the emergency lighting module would have been designed originally to operate a fluorescent lamp, it is very unlikely that it will operate a linear LED lamp in the emergency mode. LIA Technical Statements TS14 and TS25 give more guidance on this subject.
As mentioned previously in this Guide, there have been numerous incidents of dangerous and potentially dangerous LED lamps being placed on the market. Once safety issues are discovered, they may be subject to a compulsory or voluntary product recall in accordance with the degree of risk. Electrical Safety First has a list of recalled electrical equipment and appliances, including LED lamps, on their website at:
Approval and similar markings on a product do not of themselves make a product safe to use. However, it is assumed in this guide that products and their packaging that are correctly marked in accordance with the requirements of relevant product safety standards will provide important information about the correct use of a product and may act as an indicator of the quality of said product.
Clause 5.1 of BS EN 62560 requires the following markings to be placed on self-ballasted lamps:
• Mark of origin – Trademark, manufacturer’s name, or name of responsible vendor
• Rated voltage or voltage range – ‘V’ or ‘volts’
• Rated power – ‘W’ or ‘watts’
• Rated frequency or frequency range – ‘Hz’ Minimum height of letters or numbers, 2 mm. Minimum height of symbols, 5 mm.
In addition, Clause 5.2 of that standard requires the following information to be provided on the lamp, or its immediate wrapping or packaging:
• Rated current – ‘A’ or ‘ampere’ • Special conditions or restrictions which shall be observed for lamp operation – such as ‘not suitable for dimming’ (see fig 16).
• For lamps of significantly higher weight than that of the lamps that they replace, attention should be drawn to the fact that the increased weight may reduce the mechanical stability of certain luminaires and lampholders, and may impair contact making and lamp retention.
Fig 16. Symbol that lamp is not suitable for use with a dimmer switch.
Self-ballasted LED lamps sold in the UK should carry the CE mark as shown in Fig 17.
Fig 17. CE marking
A CE marking on a product is a declaration by the manufacturer that their product meets all the essential requirements of the relevant European Directives, including those for safety, performance and environmental issues. Do not rely on a CE mark alone as a guarantee of safety. Like all markings, it can be easily misused.
A number of statutory documents, including the Waste Electrical and Electronic Equipment Regulations 2006 (as amended), make the holder responsible for the disposal of waste products such as lamps and luminaires. The holder remains responsible for the waste even after it has been removed from their premises.
9. Recommendations summary
Always use good quality products obtained from a reputable source.
A good quality product will not:
• have accessible parts that could become live in operation or under fault conditions.
• be readily dismantled, either deliberately or unintentionally.
Always take manufacturers’ instructions into account when installing, using and removing LED lamps.
Ensure that the supply to the relevant circuit is switched off or the lamp/luminaire is unplugged before removing or replacing LED lamps.
Where LED tubes are to be installed in a fluorescent luminaire, the use of an LED tube type that does not require any further modification beyond the use of a replacement of the starter of a switch-start luminaire is recommended.
If any conversion work is required this must only be carried out by a suitably competent electrically skilled person. Guidance on competence is given in HSE publication HSR25.
Where a luminaire designed for use with fluorescent lamps is converted for use with LED lamps, a label should be placed on the luminaire in a position visible to persons performing relamping, stating which types of lamp are suitable for use with the luminaire.
Look for the required markings on the lamp and/or packaging and instructions discussed in section 7 of this guide.
10. Standards and other publications referenced in this guide
BS EN 60598-1: 2008 - Luminaires - General requirements and tests.
BS EN 60968: 2013 - Self-ballasted lamps for general lighting services - Safety requirements.
BS EN 62560: 2012 - Self-ballasted LED lamps for general lighting services by voltage > 50V — Safety specifications.
IEC 34/221/INF - Risk analysis on new G5/G13 luminaire for LED lamp.
IEC PAS 62776: 2013 - Double-capped LED lamps for general lighting services – safety specifications.
HSR 25 – Memorandum of guidance on the Electricity at Work Regulations 1989
LIA TS01 - LED Standards & Guidance.
LIA TS14 - T5 and T8 Fluorescent Lamp and LED Lamp/Module Adaptors “Retro-fit Conversion Units” for T8, T10 & T12 Luminaires.
LIA TS25 - Post Production Modification of Lighting Products