If you have any queries, please contact enquiries@electricalsafetyfirst.org.uk with "Wiring Regulations" as the subject line of your message.
Enter a search term in the textbox below to search the FAQ.
clearFor new installations and rewires, all socket-outlets with a rated current not exceeding 20 A need to have additional protection by RCD, except where:
It is the view of the forum that any decision to omit RCD protection should not be taken lightly.
Regulation number(s)
Yes, as long as the division of final circuits between the RCDs is carefully considered so as to minimize the consequences of unwanted tripping. Separate RCD protection is not necessarily required for each circuit of an installation but, in order to minimize the likelihood and consequences of tripping, a single (‘front end’) RCD should not be used to protect all the circuits.
Regulation number(s)
Socket-outlets other than a SELV socket-outlet or a shaver supply unit are not permitted within 3 m horizontally from the boundary of zone 1. In all other cases, only the general rules apply, in that equipment shall be of a design appropriate to the situation in which it is to be used or its mode of installation shall take account of the conditions likely to be encountered.
Manufacturer’s installation instructions shall be taken into account when selecting equipment.
Regulation number(s)
Yes. Meter tails concealed in a wall or partition at a depth of less than 50 mm from a surface must be protected in accordance with Regulation 522.6.202. Also, irrespective of the depth from a surface, meter tails concealed in a wall or partition having internal metallic parts (except nails and screws, etc.) are subject to the requirements of Regulation 522.6.203.
Regulation number(s)
Yes. Where the generic term ‘RCD’ is used, it refers to most types of residual current device including RCBOs (Residual current-operated circuit-breakers with integral overcurrent protection), RCCBs (Residual current-operated circuit-breakers without integral overcurrent protection) and SRCDs (Socket-outlets incorporating a residual current device). For the purposes of the Regulations, it does not include PRCDs (Portable residual current devices).
Regulation number(s)
There is no specific requirement in the Regulations for boiler pipework to be supplementary bonded. However, such bonding may be called for in the boiler manufacturer’s instructions, in which case BS 7671 requires those instructions to be taken into account (Regulation 510.3 refers). Any stated instruction for additional bonding that is considered to be unnecessary should be queried with the manufacturer concerned, and amended installation instructions requested.
Regulation number(s)
Yes
Regulation number(s)
Yes. The risk of penetration by a nail or screw is the same as for other concealed cable. Also, if the wall or partition has internal metallic parts (except nails and screws, etc.), RCD protection in accordance with Regulation 522.6.203 is required irrespective of the depth of the cable from the surfaces.
Regulation number(s)
Yes, if the effective current carrying capacity of the cable is at least 12.5 A (20 A × 20/32), so as to effectively have the same ‘deemed to comply status’ as Regulation 433.1.204 gives to 30 A and 32 A ring final circuits.
Regulation number(s)
There is no specific requirement in BS 7671 but, if there is considered to be a significant risk of a lightning strike, the advice of a lightning protection specialist should be sought.
In the absence of a relevant product standard, e.g. British Standard, the designer should obtain suitable evidence from the manufacturer that any product selected for the purpose is suitable to prevent penetration by nails, screws and the like.
As an example, steel of 3 mm minimum thickness is generally considered to provide sufficient mechanical protection, except where shot-fired nails or similar fixing methods are likely to be used.
Regulation number(s)
Whilst main protective bonding is required at the main intake position, it is good practice also to provide main protective bonding in each flat even though, in this case, the origin of each installation could be considered to be at the main intake position.
Regulation number(s)
No.
No, but the device does need to be so placed and marked as to be readily identifiable and convenient for the intended use
Regulation number(s)
Yes, provided that they are securely fixed to rigid parts of the units that are not demountable or otherwise liable to be disturbed in normal service. However, care must be taken to comply with all the relevant requirements of BS 7671, including accessibility for inspection, testing and maintenance, and provision of adequate protection against damage (by impact or water for example) for the accessories, equipment and associated wiring.
Regulation number(s)
There are no particular requirements or limitations in BS 5839-6 concerning the use of RCDs with Grade D fire detection and alarm systems.
For Grade D systems, which comprise one or more mains-powered smoke alarms each with an integral standby power (such as typical domestic smoke alarm with battery), BS 5839-6 simply recommends that the mains supply to the smoke and/or heat alarms should take the form of either:
i) an independent circuit at the dwelling’s main distribution board, in which case no other electrical equipment should be connected to the circuit (other than a dedicated monitoring device installed to indicate failure of the mains supply to the smoke and/or heat alarms), or
ii) a separately electrically protected, regularly used local lighting circuit.
We recommend option ii) on the grounds that disconnection of the supply to the fire detection and alarm system will be more readily noticed. In our opinion ‘separately electrically protected’ does not preclude sharing an RCD with several other circuits where this is permitted by BS 7671.
Yes. The particular requirements of BS 5839-6 take precedence over the general requirements of BS 7671.
Regulation number(s)
Appendix 15 is intended to give guidance only. Such connection is not prohibited, provided that no part of the ring final circuit will be overloaded as a result.
Regulation number(s)
If the metallic structure falls within the definition of an extraneous-conductive-part given in Part 2 of BS 7671, it is required to be main bonded.
Regulation number(s)
Verification of voltage drop is not normally required unless there is considered to be a voltage drop problem.
Regulation number(s)
Regulations 134.1.1 and 510.3 state that manufacturers’ instructions are to be taken into account during installation work. It is necessary to check that all connections are tight, and the use of a torque screwdriver is one way of confirming this.
The limit of zone 1 horizontally is 1.2 m from the centre point of the fixed water outlet (the end of the rigid pipe of the fixed water installation) on the wall or ceiling, irrespective of whether the shower head is fixed or on the end of a flexible hose. Beyond zone 1, the general rules of BS 7671 apply, including Regulation 512.2 concerning external influences. In particular, the IP rating of any electrical equipment must be adequate.
Note: There is no zone 2 for showers without a basin
Regulation number(s)
Soft-skinned cables to BS 7629-1: 2008 would be exempted from the separation requirements as they have a metallic screen and their survival in a fire has been tested in accordance with BS EN 50200. However, cables to BS 8436: 2004 would not be exempted as the product standard does not require their fire resistance to be tested. Irrespective of the above, BS 5839-1 recommends that, for a fire detection and alarm system complying with that standard, the circuits of fire alarm systems should be segregated from the cables of other circuits to minimize the potential for those other circuits to cause malfunction of the fire alarm system.
Regulation number(s)
Yes.
Yes, so long as all the other applicable requirements of the 17th Edition (as amended) are met, including those for protection against overload and short circuit.
Regulation number(s)
The provision of access to consumer units is not specifically covered by BS 7671. However, consumer units need to be so located as to permit reasonable access by users, including for the purpose of testing the RCDs at regular intervals, and in case of emergency.
For properties in England, Section 1.18 b) of Approved Document M1, - Access to and use of buildings. Volume 1: Dwellings 2015 edition, states that ‘Consumer units should be mounted so that the switches are 1350 – 1450 mm above floor level’.
The British Electrotechnical and Allied Manufacturers’ Association (BEAMA) recommend that for a multi-row consumer unit where compliance with mounting heights of ADM1 above cannot be achieved for all switches thereof, the consumer unit should be mounted such that the bottom row of switches are located between 1350 mm and 1450 mm so that they are out of reach of young children to avoid interference and inappropriate operation.
Regulation number(s)
No, unless the cupboard door does not effectively limit the extent of the location. However, where an airing cupboard opens into zone 1 or zone 2, we recommend that circuits supplying equipment in the airing cupboard are provided with additional protection in accordance with Regulation 415.1.1.
Regulation number(s)
Yes, provided the switch is located so as to be readily accessible and convenient for use.
Generally, cooker switches and cooker control units are provided as a local means of isolation and switching off for mechanical maintenance.
In most cases, the controls incorporated in a cooker can be used to remove the source of heat if danger arises.
However, a cooker switch or cooker control unit may also be provided as a means of emergency switching if the designer of the electrical installation decides that it is necessary, in which case it must be located so as to be readily accessible and convenient for use.
Yes.
Regulation number(s)
Yes, although it is recognised that the requirement may be difficult to comply with in some situations. The Forum intends to raise this issue with the BS 7671 Committee.
Not necessarily. Not all types or designs of push fit (screwless-type) clamping units comply with the requirements of Regulation 526.3 (vi).
If the connector will be inaccessible when the installation is complete, it must comply with BS 5733 for a maintenance-free accessory, be marked with the ‘MF’ symbol indicated in Regulation 526.3 (vi), and be installed in accordance with the manufacturer's instructions.
BS 5733 requires, for example, tests for resistance to ageing, cyclic loading, overload, fault current and vibration.
Yes, but certain restrictions apply if the space under the bath or shower is accessible without using a tool because the space is then classed as zone 1.
In zone 1, any low voltage current-using equipment (such as a booster pump for a shower) must be fixed and permanently connected, and the manufacturer’s instructions must confirm that is suitable for installation in that zone.
As with any other item of equipment installed in zone 1, the accessory used to connect it to the supply would need to provide a degree of protection of at least IPX4.
Regulation number(s)
Yes. As the space under the bath or shower is accessible only by means of a tool, the space is classed as being outside the zones (Regulation 701.32.3 refers).
Consequently, low voltage current-using equipment (such as a shower booster pump) installed in the space need not be permanently connected, and it may therefore be connected by means of a plug and socket-outlet installed in the space.
Regulation number(s):
Electrical Safety First's Best Practice Guide No 1 (Replacing a consumer unit in domestic and similar premises) sets out a procedure to help avoid such foreseeable circumstances.
In any event, the shared neutral situation must be corrected to remove the electric shock hazard.
Preferably each circuit should be provided with its own neutral to satisfy Section 314.
However, where this is not practicable, the two lighting circuits sharing the neutral may be connected to a single protective device (creating a single circuit), provided that the circuit is suitable for the connected load.
Regulation number(s)
Yes, where documentation is obtained from the consumer unit manufacturer confirming that the specific mounting orientation is suitable and complies with BS EN 60439-3. Where catalogue products cannot fulfil the installation requirements, manufacturers can be contacted to discuss tailored solutions.
It is essential that any label, RCD test instructions etc remain legible.
Regulation number(s)
The switch requires clear labelling or indication for the ON and OFF positions, regardless of orientation.
Regulation number(s)
Yes, in certain circumstances. Distributors generally accept a maximum of 2m or 3m from the service head. Where the tails need to be longer, the distributor may require a means of isolation and/or a protective device to be provided within 2m or 3m of the service head. Any particular requirements should be ascertained in advance from the distributor.
Yes. The close proximity of the cold water pipe to the wiring system is unlikely to be detrimental to the cable, for example due to heat or condensation.
Regulation number(s)
Usually not. Manufacturers’ instructions for consumer units and distribution boards generally advise against this for technical reasons (such as potential overheating). Equipment from different manufacturers should not be mixed unless documentation is obtained from the consumer unit or distribution board manufacturer which confirms that the specific mixed arrangement is suitable for use in an assembly conforming to BS EN 60439-3. Further guidance can be found at www.beama.org.uk
Regulation number(s)
BS 7671 does not define a dimension to qualify “simultaneously accessible” with respect to supplementary bonding.
However, with respect to prevention of unintentional contact with live parts, the note to 417.3.1 states that two parts are deemed to be simultaneously accessible if they are not more than 2.50 m apart.
Therefore, it is reasonable that with respect to supplementary bonding, parts greater than 2.50 m apart may be considered not to be simultaneously accessible.
Although there is no specific requirement for this in BS7671, account should be taken of the manufacturer's installation instructions, which may or may not require such protection.
Regulation numbers: 134.1.1, 510.3
Regulation number(s)
Any installation instructions considered to be technically unsound should be queried with the manufacturer and/or referred to the electrical contractor’s registration body for information.
Main protective bonding is required between each metallic branch as it enters an apartment and the Main Earthing Terminal in that apartment, unless it has been proven that the metallic pipework is not an extraneous-conductive-part.
Regulation number(s)
If the distribution board or consumer unit is fitted with blanks that can be removed without the use of a tool or key resulting in live parts being made accessible to touch, at least one of the following requirements must be complied with (in addition to the manufacturer’s instructions):
If the distribution board or consumer unit is located in a generally accessible area and has a flap-type lid with no securing device, the blanks fitted must be of a type that can be removed only by opening the front cover, using a tool or key.
Regulation number(s)
No attempt should be made to make a bonding connection directly to semi-rigid pipework.
(a) Where the gas meter is installed inside the premises, the semi-rigid pipework will normally end at the meter and so the bonding connection should be made as normal to the consumer’s hard metal pipework after the meter and before any branch pipework. Where practicable the bonding connection should be within 600 mm of the meter outlet union.
(b) Where the meter is external to the premises in a wall-mounted or semi-concealed meter box, the bonding connection should be made to the consumer’s hard metal pipework and before any branch pipework. Where practicable this connection should be made at the point of entry to the building.
Regulation number(s)
If, by design, fault protection is provided by a fuse, circuit-breaker or the overcurrent characteristic of an RCBO, the maximum Zs permitted by BS 7671 for U0 of 230 V can be taken from Table 41.2, 41.3 or 41.4, as applicable.
Where, by design, fault protection is provided by an RCD or the RCD element of an RCBO, the maximum Zs permitted by BS 7671 for U0 of 230 V can be taken from Table 41.5.
Regulation number(s)
Yes.
Any low voltage circuits passing through, but not serving, zone 1 or Zone 2 of the location must be provided with additional protection by RCD.
Regulation number(s)
Generally, no.
However, where a risk assessment is carried out and this indicates that unacceptable consequences exist, such as to human life (as a result of damage to essential medical equipment, for example), SPDs must be installed. In addition, where the consequences of equipment failure due to an overvoltage are deemed to be unacceptable after discussion with the customer, SPD protection should be provided.
Regulation number(s)
No (with one specific exception). Single-core cables having green-and-yellow insulation must not be overmarked or otherwise identified, and must not be used for any purpose other than a protective conductor. The only exception is where such a cable is used as a PEN (combined protective and neutral) conductor, when blue markings must be provided at the terminations.
Regulation number(s)
No. An excessively high external earth loop impedance value would need to be brought to the attention of the Distribution Network Operator (DNO).
BS 7671 does not specify a minimum distance between an accessory and a heat source, such as a hob. However, indent (ii) of Regulation 522.2.1 recognises placing sufficiently far from the source of heat as one method that may be used to protect a wiring system.
When considering what constitutes a suitable distance, it is worth remembering that the sources of heat on a cooker top are usually somewhat inboard from the edge of the appliance. Another point to remember is that the integral control dials on a cooker are in some cases significantly closer to the source of heat than any accessory affixed to the building fabric, and they do not suffer significant heat damage.
An accessory installed at least 100mm horizontally from the edge of the hob is likely to meet the requirements of BS 7671. If an accessory is encountered closer to a hob than this during a periodic inspection, engineering judgement will need to be applied to determine whether this is safe. An accessory so located for a considerable time that had not suffered any perceptible heat damage would not warrant a classification code or comment on the Electrical Installation Condition Report.
Any manufacturer’s recommendations should be taken into account.
An accessory should not be located immediately above an electric oven or hob due to the possibility of people reaching over suffering burns or the flexible cable of connected equipment being damaged.
Regulation number(s)
BS 7671 does not specify a minimum height or horizontal distance. However, Regulation 512.2.1, relating to external influences, requires that equipment shall be of a design appropriate to the situation in which it is to be used or its mode of installation shall take account of the conditions likely to be encountered.
Regulation 522.3.1 requires a wiring system to be selected and erected in such a way that no damage is caused by condensation or by ingress of water whilst being installed, used or maintained.
For domestic premises, to minimise the effects of splashing, an ordinary accessory installed at least 300 mm horizontally from the extremity of the sink or basin opening is likely to meet the requirements of BS 7671.
For commercial premises, the same principle applies. However, the designer may consider it appropriate, due to the increased risk of splashing or the use of water jets, to install equipment that has a degree of protection of at least IPX4 or IPX5 respectively, as appropriate.
If an accessory is encountered closer to a sink than this during a periodic inspection, engineering judgement will need to be applied to determine whether this is safe. An accessory so located for a considerable time that had not suffered any perceptible water ingress or damage would not warrant a classification code or comment on the Electrical Installation Condition Report.
General guidance is to avoid positioning a consumer unit immediately above or alongside a sink.
Regulation number(s)
It is indeterminate which of the above regulations should be applied where the sloping surface might reasonably be considered to be either a wall or a ceiling. Nevertheless, it is still necessary to comply with the fundamental requirements of BS 7671 for protection of a wiring system against impact, which are given in Regulations 522.6.1 and 522.6.2.
One way of meeting these fundamental requirements in the case of a sloping surface that could be either a ceiling or a wall is to design the part of the installation concerned to meet the requirements of Regulation 522.6.201 and 522.6.204 and the requirements of Regulations 522.6.202 to 522.6.204.
Regulation number(s)
If an existing circuit of a location containing a bath or shower is extended, at least the extended part of the existing circuit must be provided with RCD protection. Supplementary bonding in a bathroom or shower room must be provided unless all the requirements in the 17th Edition for the omission of supplementary bonding are met.
Regulation number(s)
The preferred option is to provide RCD protection for the circuit at the origin as this gives an improvement in safety for the whole circuit.
Alternatively, an RCD protected, switched, fused 13 A connection unit could be added directly adjacent to the existing outlet from which the extension is being taken.
Regulation number(s)
No. Any alteration or addition to an existing installation must comply with the current edition of BS 7671 (including any amendments). This requires any earthing and bonding arrangements upon which the alteration or addition relies for safety to be adequate.
Regulation number(s)
Additional protection by RCD is a requirement for low voltage cables concealed in a wall at a depth less than 50 mm from the surface of a wall or partition, or concealed at any depth in a partition the internal construction of which contains metallic parts.
RCD protection for low voltage cables so installed in a wall or partition may only be omitted where the cables:
Regulation/s:
The designer (who may be the contractor or a consultant) is responsible following discussions with the client/duty holder as appropriate to the circumstances.
An inadequate risk assessment justifying the omission of additional protection by RCD may leave a contractor open to liability at a later date in the event of an incident.
Because of this, the person responsible for the risk assessment must be suitably competent in terms of their knowledge, training and experience with respect to electrical safety.
The model Electrical Installation Certificate in Appendix 6 of BS 7671 has fields to allow details of two designers to be recorded. Where a person other than the designer of the rest of the installation is responsible for the decision to not provide additional protection they should sign as the designer of this aspect of the electrical installation and include details of the extent of their design responsibility.
Regulation number/s:
Details of this permitted exception should be recorded on the Electrical Installation Certificate or Minor Electrical Installation Works Certificate. The risk assessment should be attached to the certificate.
Regulation:
Yes. There should be more than one RCD, and the circuits should be divided between them in order to minimize the likelihood and consequences of tripping.
Regulation number(s)
No. Such maintenance or repair work would not be classified as an alteration or addition.
Regulation number(s)
No. Such repair work would not be classified as an alteration or addition.
Regulation number(s)
No, unless RCD protection is recommended by the manufacturer’s installation instructions or a new circuit is required (to provide for increased load, for example).
In cases where the existing consumer unit is of a type that will permit the replacement of an existing circuit-breaker by an RCBO of appropriate type and rating for the circuit in question, the installer may wish to explain the benefits of improved safety provided by carrying out such a, relatively speaking, simple upgrade.
Regulation number(s)
Supplementary bonding would be required for any new extraneous-conductive-part installed in a bathroom or shower room unless all the other requirements of Regulation 701.415.2 have been met.
Regulation number(s)
Not necessarily. If the existing 6 mm² bonding connects all the extraneous-conductive-parts to the main earthing terminal, has been in place for a significant time and shows no signs of thermal damage, then it may not require to be upgraded.
Regulation number(s)
Regulation 537.1.4 requires a main linked switch or linked circuit-breaker to be provided as near as practicable to the origin of every installation as a means of switching the supply on load and as a means of isolation.
However, it is permitted for a dwelling to have more than one electrical installation. Therefore a further ‘main switch’ is not required to isolate both consumer units.
Regulation 537.2.2.6 requires each device used for isolation to be clearly identified by position or durable marking to indicate the installation it isolates.
Regulation number(s)
No. As the new work must comply with BS 7671, fault protection must be provided by an overcurrent device or RCD, and additional protection, where required (such as for socket-outlets or cables concealed in walls), must be provided by a 30 mA RCD.
No.
Yes, because the work would be more than a like-for-like replacement.
Regulation number(s)
No, not without additional mechanical protection.
You should make your customer aware of the issues relating to accessibility, including the need to test RCDs at quarterly intervals, to enable the customer to make an informed decision about the position of the replacement consumer unit.
Regulation number(s)
All accessible exposed-conductive-parts and extraneous-conductive-parts are required to be connected to the same earthing system individually, in groups or collectively. This means that the main earthing terminals must be connected together.
Yes, but only where the manufacturer's instructions confirm that the switch has been designed for this purpose.
Yes.
Regulation number(s): 132.16
Regulation number(s): 132.16
Yes.
Regulation number(s): 132.16
Regulation number(s): 132.16
No, as this may result in unearthed parts of the existing installation and earthed parts of the new circuit being simultaneously accessible. This is not permitted by Regulation 411.3.1.1.
In any event, whenever an alteration or addition is carried out to an existing installation, it shall be verified that the alteration or addition complies with the Regulations and does not impair the safety of the existing installation.
Regulation number(s)
Where additional protection by RCD is necessary, unwanted tripping can be avoided by appropriate sub-division of circuits.
Regulation number(s)
Reference should be to the applicable Building Regulations, BS 5839-1 and BS 5266 which give specific recommendations.
No. An RCD is a valid way of complying with automatic disconnection requirements.
Regulation number(s)
No. The 17th Edition requires all extraneous- and exposed-conductive-parts that can be touched by livestock to be supplementary bonded, whether or not the parts are simultaneously accessible.
Regulation number(s)
No. Section 717 applies to transportable units that are intended to be moved relatively frequently from place to place and which therefore need to be supplied through flexible cables.
Regulation number(s)
At the location of the equipment which cannot be disconnected in the prescribed time. Consideration must be given to disconnection required for reasons other than electric shock, for example, overcurrent protection.
Regulation number(s)
Yes.
No. The above cable does not meet indent (ii). To comply with indent (iii), duplicate protective conductors would be required. Alternatively, the solutions offered by indent (iv) or (v) could be adopted.
Regulation number(s)
a) Yes, except where the cable management system is not an exposed-conductive-part. (The steel wire armour of a cable is considered to be an exposed-conductive-part.)
b) No. There is no requirement to calculate or select the cross-sectional area of an exposed-conductive-part unless it intended to be used as a circuit protective conductor.
Regulation number(s)
The information should be recorded somewhere in the installation details, but not necessarily in the distribution board schedule and schedule of test results.
Regulation number(s)
Yes. The armour provides suitable protection against mechanical damage.
Regulation number(s)
Primarily the chassis. Any conductive parts connected electrically to the chassis would be effectively bonded. Any conductive parts not connected electrically to the chassis would be isolated, and would therefore not need to be bonded for reasons of safety.
Regulation number(s)
No. If the tables are not liable to introduce a potential, generally Earth potential, they will not require main bonding.
A dry assembly area would not be considered to be a location of increased shock risk, so there is no requirement for supplementary bonding.
The tables are not items of electrical equipment, so there is no requirement for them to be earthed.
Regulation number(s)
No.
If the installer decides to use conductors smaller than those permitted by Table 52.3 and Regulation 559.11.5.2, this would need to be noted as a departure in the Electrical Installation Certificate (Regulation 120.3 refers).
Where a departure is noted in an Electrical Installation Certificate, the designer and/or installer is declaring that the resulting degree of safety of the installation will be not less than that obtained by compliance with the relevant requirements of BS 7671.
ELV cables fitted with plugs and sockets supplied as part of a prefabricated CE-marked LED lighting system (comprising driver, LED lights and interconnecting cables) are assemblies of electrical equipment and are therefore not subject to the minimum cross-sectional area requirements of BS 7671.
Regulation number(s)
Guidance can be found in the Health and Safety Executive’s publication HSG 47 Avoiding danger from underground services, which can be downloaded free of charge from the HSE website.
Regulation 512.1.5 requires that equipment shall not be connected to conductors intended to operate at a temperature exceeding 70? C at the equipment in normal service unless:
Regulation number(s)
Yes. Protective neutral bonding (PNB) like protective multiple bonding (PME) is a variant of TN-C-S system, but unlike PME the combined neutral and earth (CNE) conductor is connected to Earth at one point only.
Clause 4.11 of Engineering Recommendation G12 Issue 4 (2013) Requirements for the Application of Protective Multiple Earthing to Low Voltage Networks published by Energy Network Association (ENA) states that an earth terminal provided using PNB shall be treated in all respects as a PME earth terminal.
As advised by the Note above Table 54.8 of BS 7671, designers should confirm any particular requirements of the relevant local Distribution Network Operator (DNO) as a DNO may require a larger size of protective bonding conductor may be needed to take account of local network conditions.
Guidance on this can be found in Clause 6.2.5 of Engineering Recommendation G12 Issue 4 (2013) Requirements for the Application of Protective Multiple Earthing to Low Voltage Networks published by Energy Network Association (ENA).
Where it has been decided to use a PME supply, and where the distributor agrees to such use, all the appropriate requirements withinSection 702 of BS 7671 must be met.
There is no specific requirement in 421.1.201 for fire-rated cable glands or intumescent sealant to be used for cable entries.
Good workmanship must be applied in particular to limit openings around cables to a minimum. In any case, the requirements of regulation group 416.2 for barriers or enclosures must be met.
Manufacturers’ instructions, if any, should be taken into account.
Regulation number(s):
Regulation group:
The term ‘escape route’ is defined in Part 2 of BS 7671 as the ‘path to follow for access to a safe area in the event of an emergency’.
Communal corridors and stairways located in industrial and commercial buildings and blocks of flats are examples of escape routes.
In domestic premises examples include passageways and staircases that are the sole means of exiting in an emergency other than escaping from an emergency escape window.
Regulation: Part 2
Yes, BS 7671 includes requirements for the fixed wiring for information and communication technology, signalling, control and the like (see indent (v) of Regulation 110.1.2).
Regulation number(s):
Yes, so long as within the consumer unit:
Regulation number(s):
On the schedule of inspections for new installation work only, item 7.4 should be marked as not applicable (N/A) because it is not a newly installed item of equipment.
Within the ‘Comments on existing installation’ section on the Electrical Installation Certificate a statement should be made that:
‘N/A’ has been recorded against item 7.4 of the schedule of inspections because the addition has been made to a consumer unit that was installed to the requirements of an earlier edition of BS 7671 and has been verified to be adequate for continued use.
Regulation number(s):
For basic, non-specialist installations, the installation will meet EMC requirements so long as all installed equipment has CE marking and has been installed in accordance with manufacturers’ instructions, with the instructions being available for reference.
Regulation number(s):
Wiring systems, whether cables clipped direct, conduit, trunking or similar should be supported in accordance with the recommendations of the manufacturer.
Regulation number(s):
Yes, subject to such construction being suitable for ambient environmental conditions such as:
•likelihood of mechanical damage,
•use of outbuilding for storage of flammable materials such as paint and thinners, or
•presence of a corrosive atmosphere, such as that found in a swimming pool pump room.
Consideration should also be given to the relative proximity of the outbuilding to the dwelling with respect to the possibility of fire-spread from one structure to the other.
| Yes, subject to such construction being suitable for ambient environmental conditions such as:· likelihood of mechanical damage, · use of outbuilding for storage of flammable materials such as paint and thinners, or · presence of a corrosive atmosphere, such as that found in a swimming pool pump room. |
Consideration should also be given to the relative proximity of the outbuilding to the dwelling with respect to the possibility of fire-spread from one structure to the other.
Not necessarily. Suitable fire-resistant means of support or retention should be provided to prevent wiring systems impeding escape routes in the event of a fire.
The easiest way of achieving this is for all supports in the escape route to be of a type unaffected by fire.
Where it is decided to not use only fire resistant cable supports, this will require careful assessment of the individual circumstances.
Regulation number:
No.
No. Manufacturers’ instructions, if any, should be taken into account
Not necessarily. Manufacturers of trunking systems will be able to advise on making their trunking compliant with Regulation 521.10.1.
In general, a system assembled properly from compatible parts such as trunking, lids, tees, bends and other accessories will comply, as could a system containing well-made site-fabricated bends although it should be noted that some contracts or specifications will not permit the use of site manufactured bends.
Regulation numbers:
No.
A sheathed cable can be passed through a suitably sized hole drilled through an external wall without sleeving. Reasonable steps should be taken to ensure that the cable is not damaged during installation.
It is recommended that any such hole is angled downwards so outside hole is lower than that on inside and the space between hole and cable is suitably stopped to prevent moisture penetration.
Regulation numbers:
It is necessary to confirm that the rating and condition of any existing electrical equipment, including that of the distributor / supplier will be adequate for the altered circumstances, such as any increase in electrical loading that the addition/alteration introduces.
It is also necessary to confirm the adequacy, in relation to protection against electric shock, of the earthing and bonding arrangements.
Regulation numbers:
BS 7671 does not specifically require the provision of a local means of disconnection to be provided for appliances.
However, many manufacturers of built-in appliances recommend that a means of disconnecting the appliance should be accessible when the product is installed; therefore it is advisable to request any special installation instructions pertinent to their equipment from those supplying such equipment.
Yes. Engineering Recommendation G12-3 published by the Energy Networks Association permitted Distribution Network Operators (DNOs) to install BS 951 clamps on the sheath of a cable. G12-4, published in 2013, now permits DNOs to use clamps which comply with EREC C93. So, both BS 951 and other clamps may be encountered on the sheaths of service cables.
On no account should an electrical contractor fit a clamp to the sheath of a service cable.
Before starting any electrical installation work or when carrying out a periodic inspection of an installation, the electrician must confirm that the earthing facility is sufficient in terms of the requirements of BS 7671.
One way to verify the adequacy, or otherwise, of such a connection is to carry out a measurement of the impedance of that part of the earth fault loop external to the installation (Ze) at:
The two readings obtained should be substantially the same.
Typically, the maximum impedance of that part of the earth fault loop external to the installation (Ze) is 0.8 Ω. However, due to network conditions this value is sometimes exceeded.
Responsibility for ensuring the safety and effectiveness of this connection rests with the DNO (Regulation 24(1) of the Electricity Supply Quality and Continuity Regulations (ESQCR)).
The electrician should advise the customer to contact the relevant Distribution Network Operator (DNO) and request that the ineffective connection on their equipment is rectified. The DNO may be able to provide a TN-C-S earth to the property although there may be a charge to do so.
Alternatively, the electrician can offer to convert the system earthing to TT through installation of earth electrodes and any required RCD protection.
On no account should:
No. Note 1 of 421.1.201 gives ferrous metal as an example of a non-combustible material. The cabinet or enclosure can be made of other non-combustible materials. However, the installer will need to judge whether such material used will provide adequate protection. Account will also need to be taken of Regulation 132.12 in relation to accessibility.
Regulation(s) 421.1.201 (ii)
Buried cables, conduits and ducts shall be at a sufficient depth to avoid being damaged by any reasonably foreseeable disturbance of the ground.
A depth of 0.5m is recommended as sufficient to avoid damage by general gardening.
Where more onerous conditions are present due to vehicle movement or ground cultivation then greater depths should be used.
All buried cables should be identified with a warning tape or cable covers above the cable.
It is strongly recommended that the route of a buried cable should be identified on a drawing attached to the Electrical Installation Certificate.
Regulation(s) 522.8.10; 705.522; 708.521.1.1
Yes.
The circuits and also the conductors of each circuit within the multicore cable would need to be suitably identified to permit inspection, testing, repair or alteration.
Whilst it would be permissible for the multiple circuits to share a common CPC such as the armouring of an SWA cable, it would not be permissible to share a neutral.
Where circuits are at different operating voltages, each conductor must be insulated for the highest voltage present.
When considering current carrying capacity, Table 4B5 of BS 7671 contains rating factors for cables having more than four loaded cores.
Regulation(s) 514 group; 521.7; 528.1; Table 4B5.
Yes.
Where water connection valves serving appliances such as washing machines and dishwashers are present, socket-outlets should be so placed that water from these valves or hoses connected to them is unlikely to affect the socket-outlet or plug during connection or disconnection of the appliances.
Regulation 421.1.201 relates to consumer units and similar switchgear assemblies complying with BS EN 61439-3 Low voltage switchgear and controlgear assemblies. Distribution boards intended to be operated by ordinary persons (DBO).
Switch-disconnectors (both a.c. and d.c.), otherwise known as isolating switches, are designed and manufactured to a different standard - BS EN 60947-3 Switches, disconnectors, switch-disconnectors and fuse-combination units and therefore are not subject to this requirement unless they are incorporated within a consumer unit or similar controlgear assembly.
This does not preclude the specification or use of switch-disconnectors having non-combustible / metal enclosures.
Regs:
A. No, however this does not preclude its use.
A. Protective bonding is only required where the pipework is an extraneous-conductive-part. Such protective bonding should be applied as near as practical to the point of entry of that pipework to the building.
No.
Reg 411.3.1.2
When it is proved to be an extraneous-conductive-part.
Reg 411.3.1.2
Yes, provided all relevant design criteria is verified as suitable.
Reg Sections 311, 312, 313, 314 and Appendix 15
Yes, the requirements in 544.2 apply to all supplementary bonding conductors.
Reg 415.2, 544.2
It is impossible to give an exact generic figure in terms of recommended service life. This is due to a number of factors.
As an indication as to whether the device is in a satisfactory condition for continued service, it must be manually operated and examined to validate that it is of the correct type and ratings and has no signs of thermal / mechanical damage, arcing or overheating.
Regulations CH62, Appendix 6 condition report inspection schedule (4.8, 4.14)
IET Guidance Note 3 and Electrical Safety First Best Practice Guide 4.
Irrespective of the age of the BS 3871 equipment, a code or comment is not required provided there is no deterioration, defect, or non-compliance with the current edition of BS 7671 that may give rise to danger.
CH62, Appendix 6 condition report inspection schedule (4.8, 4.14)
Electrical Safety First Best Practice Guide 4.