Welcome Login
Electrical

Frequently Asked Questions

General

When is the cut-off date for using 17th Edition?

BS7671:2018 was issued on 1 July 2018 and it replaced the previous version which is BS 7671:2008+A3:2015, it is applicable to any electrical design work completed after 31 December 2019. Installations which were designed before this date may be installed to the previous Edition of the Regulations. If a concept design was completed before 31 December 2019 and the detailed design was not completed until after this date, the installation would need to be designed to BS 7671:2018.

Back to top

What qualifications do I need to carry out electrical work?

BS 7671:2018 does not set out requirements for specific qualifications for electricians and the IET cannot advise the exact qualifications which are required but the Electrical Contractors Association (ECA) may be able to provide guidance.

The Electricity at Work Regulations requires all persons carrying out electrical work to be competent. The person requires sufficient skill, knowledge and experience to carry out the work and relevant inspection and testing.

BS 7671:2018 Regulation 134.1.1 states that persons carrying out electrical works shall be skilled. A skilled person as defined in BS 7671 is a person who possesses, as appropriate to the nature of the electrical work to be undertaken, adequate education, training and practical skills, and who is able to perceive risks and avoid hazards which electricity can create.

Link to SD article

Back to top

Do I need to do the 18th Edition course?

Whilst 18th edition training is not mandatory but as of 1 January 2019, all installations shall be designed and installed to the current edition of BS 7671. Whilst obtaining the qualification is not mandatory, it would likely be the best way to demonstrate competence and be up to date with all of the recent changes.

However, it should be noted that trade associations may have more onerous requirements and should be contacted to verify their requirements for members.

Back to top

Can I get someone to certify my electrical work under Part P?

Certification by a registered third-party installer is acceptable under part P of the building regulations providing a third-party certifier is appointed and they are required to inspect and test the work as necessary throughout the installation. This will ensure it has been installed in compliance with part P of the building regulations.

an electrical installation certificate can only be issued by the person responsible for carrying out the electrical installation work. You will receive an electrical installation condition report which will verify the safety of the installation providing the inspection and testing has been completed adequately at the relevant stages.

Back to top

What is the recommended frequency between inspection and testing for a dwelling?

The initial frequencies for inspection and testing will be recommended by the electrical designer and subsequent intervals will be recommended by the competent person carrying out the inspection and test, this interval will be based on the findings of the inspection.

IET Guidance Note 3, Section 3.7, provides some useful information regarding recommended frequencies of inspection of electrical installations. Table 3.2 provides recommended initial frequencies of inspection of electrical installations, but these are not legal requirements. It should be considered as a starting point for the electrical designer or duty holder.

Back to top

What is the minimum distance to install electrical equipment from kitchen sinks or wash basins?

BS 7671:2018 does not provide specific measurements for distances for electrical equipment from sinks, Regulation 133.3 states that electrical equipment shall be selected to withstand environmental conditions.

NHBC provides guidance on minimum distances and can be found on the link below.

http://www.nhbc.co.uk/Builders/ProductsandServices/TechZone/NHBCStandards/TechnicalGuidanceDocuments/81/filedownload,65380,en.pdf

Back to top

What do I do if a project has started and the electrical contractor is unable to complete?

An electrical installation certificate can only be issued by the person(s) carrying out the work. It covers all stages of the installation work including elements which may be covered by the building fabric.

If an electrical contractor fails to complete the installation for any reason, it will be necessary to appoint a new contractor to complete the works. If works have been covered by the fabric of the building at this stage, the contractor may have to issue an electrical installation condition report to cover this element of the works as it will not be possible to fully inspect the installation.

Back to top

What colour does control panel wiring need to be?

Control panel wiring does not fall within the scope of BS 7671, the best source of information is BS EN 60204-1 2018, safety of machinery - electrical equipment of machines which makes recommendations for identification by colour.

Consumer units and protective devices

Back to top of page

Can I install a consumer unit several metres from the supply point?

If it is required to install a consumer unit in a different location to the supplier's cut-out, it may be necessary to install a sub-main and a switch fuse disconnector. It’s recommended that the distribution network operator (DNO) is contacted to verify their requirements as it is their cut-out fuse which is protecting the meter tails. BS 7671 Regulation 433.2.2 states that unless the meter tails are installed in such a manner as to reduce any fault to a minimum, they should be no longer than three metres.

Back to top

Can I install 4 x 32 A circuit breakers in a consumer unit via a 63A RCD?

BS 7671:2018 Regulation 536.4.202 states that overload protection shall not solely be based on the use of diversity factors of the downstream circuits. To achieve overload protection of RCCB’s or switches, the rated current of the overcurrent protective device shall be selected according to the manufacturer’s instructions.

In order to achieve overload protection of the RCCB circuits, the rating shall be selected to coordinate with the upstream fuse, which is likely to be the distributors fuse.

Download the BEAMA Technical Bulletin Ed 2 Mar 2019 - Overload Protection of an RCCB or Switch BS EN 61439-3

Back to top

Do RCDs provide overcurrent protection?

RCCBs do not provide overcurrent protection, there will be two ratings on an RCCB. One will indicate the tripping current in milliamps and the other rating marked on the device refers to the current-carrying capacity but its important to remember that the device is not designed to trip at this value and additional protection against overload is required.

Back to top

Is a Type AC RCD suitable for all installations?

Requirements for different Types of RCD RCCBs are identified in BS 7671:2018 Regulation 531.3.3. Type AC RCDs are only suitable for sinusoidal residual current, if any element of residual direct current is present such as produced from electronic devices and devices containing speed controllers, this can ‘blind’ the RCD and prevent it from operating. It is important to select the appropriate device for the type of equipment which is likely to be used in the installation.

View the 'Which RCD Type?' article

Back to top

Do I need to put an RCD on a lighting circuit?

BS 7671 Regulation 411.3.4 requires that all luminaires within domestic (household) premises are to have additional protection by a 30 mA RCD when installed in an AC final circuit.
This new Regulation means that electrical installers have to provide RCD protection on all new lighting circuits as well as those that are significantly altered.

Back to top

Do I have to install SPDs?

It’s a good idea to install Surge Protective Devices (SPDs) to protect sensitive, valuable electrical equipment or safety services.

Lightning strokes are the most common source of extreme transient overvoltage’s where total outage of an unprotected system can occur with significant damage to equipment and cable insulation through flashover potentially resulting in loss of life or injury due to fire or electric shock.

Switching transients may also occur, for example due to interruption of short circuit currents, such as a fuse blowing. Whilst this may be of a lower magnitude than a lightning strike, it is likely to happen more frequently.

Single dwelling units should be assessed against the value of the electrical installation and equipment therein. i.e. Does cost of surge protective device justify installation.

Back to top

Cables/Fire protection

Back to top of page

Can I use SY, YY and CY cables in an electrical installation?

YY, SY and CY cables are made to various manufacturers specifications but not governed by any national, European or international standard, hence these are not currently recognized in BS 7671:2018. Regulation 133.1.1 requires every item of equipment to comply with the appropriate British or Harmonised Standard.

Regulation 134.1.1 permits the use of new materials and inventions, providing that the resulting degree of safety of the installation shall be not less than that obtained by compliance with the Regulations. But it’s difficult to see how a designer could provide that assurance in the absence of the appropriate standards.

Back to top

Do I have to install AFDDs?

BS 7671:2018 Regulation 421.1.7 makes recommendations for Arc Fault Detection Devices (AFDD) as opposed to requirements. It's a good idea for the electrical designer to have thorough communication with the client to understand the benefits and decide if AFDD’s are required.

Examples of where such devices can be used include:

  • premises with sleeping accommodation
  • locations with a risk of fire due to the nature of processed or stored materials, i.e. BE2 locations (e.g. barns woodworking shops, stores of combustible materials)
  • locations with combustible constructional materials, i.e. CA2 locations (e.g. wooden buildings)
  • fire propagating structures, i.e. CB2 locations
  • locations with endangering of irreplaceable goods.

Back to top

Do I need to install a metal consumer unit in domestic premises?

Requirements were introduced in BS 7671:2008+A3:2015 for consumer units and similar switchgear assemblies in domestic premises to be manufactured from non-combustible materials or be enclosed in a cabinet constructed from non-combustible materials. The requirements are identified in BS 7671:2018 Regulation 421.1.201.

Back to top

How do I fire seal a consumer unit?

There is no requirement in Regulation 421.1.201 for fire-rated glands or internal and/or external intumescent seal, pad, strip or similar to be used to seal a consumer unit. Manufacturers instructions should be followed.

Back to top

Do cable supports above plasterboard ceiling need to be metal?

BS 7671:2018 Chapter 52, Regulation 521.10.202 states that wiring systems shall be supported such that they will not be liable to premature collapse in the event of a fire. This is to prevent wiring systems from hanging which may hinder evacuation or obstructing firefighting activities.

The electrical designer may deem it to be appropriate to rely on the plasterboard ceiling to provide the fire protection to the wiring system to prevent premature collapse but many influences should be considered such as building size, complexity and evacuation times.

Back to top

What are the requirements for cables to minimise the spread of fire?

To prevent the spread of fire between fire segregated compartments, cables shall be installed in accordance with, BS 7671:2018 Section 527. Cables are required to be flame retardant in accordance with BS EN 60332-1-2, or installed within containment having the necessary resistance to flame propagation, to the relevant standards identified in Regulation 527.1.5. Wiring systems which do not meet these requirements shall be completely enclosed in suitable non-combustible building materials.

It’s also important to note that containment systems which pass through fire between fire segregated compartments shall be externally sealed as required by Regulation 527.2.1 and internally sealed as required by Regulation 527.2.2 to the degree of fire resistance of the respective element before penetration.

View our 'Fire stopping' article

Back to top

Where do I have to install LS0H cables?

BS 7671:2018 Regulation 422.2.1 states that cables shall not encroach on escape routes unless they meet the requirements of the relevant part of BS EN 60332BS EN 61034-2, this standard requires cables to be tested to verify low smoke emissions.

Building Regulations for England 2010, 2019 edition, Volume 2: Buildings other than dwellings, Requirement B1 states that where necessary, escape routes are sufficiently protected from the effects of fire and smoke.

There are lots of acronyms for these types of cable and many are registered trademarks, examples below:

  • Low Smoke Zero Halogen (LS0H/LSZH)
  • Low Smoke Halogen Free (LSHF)
  • Halogen Free (HF)
  • Zero Halogen (ZH)
  • Low Smoke and Fume (LSF)
  • Zero Halogen Low Smoke (OHLS), and
  • Halogen Free Flame Retardant (HFFR).

LSF and LSZH cables are often confused to be the same, which is not the case. PVC compounds are used during the manufacture of LSF cables and whilst additional additives reduce the smoke emissions, they are not eliminated, there are no standards governing LSF cables, unlike LSZH which are manufactured and tested to BS EN 61034 and BS EN 60754 series.

The type of cable required for an installation is subject to risk assessment and the client’s specification.

Back to top

Is fire stopping a requirement in BS 7671:2018?

Sealing of wiring system penetrations is covered in Section 527.2 of BS 7671:2018. Where containment for wiring systems passes through a fire-resisting element of the building, it shall be internally sealed as required by Regulation 527.2.2 to the equivalent degree of fire resistance (if any) of the element which has been penetrated.

However, it should be noted that fire stopping is a specialist job and the installer must be competent to carry out the works.

View our 'Fire stopping' article

Back to top

Earthing and bonding

Back to top of page

Do I have to bond a water or gas pipe if the incoming service pipe is plastic?

The requirements for protective equipotential bonding are set out in Regulation 44.3.1.2, it requires protective bonding conductors to be installed to connect extraneous conductive parts to the main earthing terminal. Examples are provided such as:

  • Water installation pipes
  • Gas installation pipes
  • Other installation pipework and ducting
  • Central heating and air conditioning systems
  • Exposed metallic structural parts of the building.

However, it should be noted that these are merely examples and it must be verified that the conductive part is actually an extraneous-conductive-part before deciding to connect to to the main earthing terminal.

An extraneous-conductive-part is defined in BS 7671:2018 as a conductive part liable to introduce a potential, generally Earth potential, and not forming part of the electrical installation.

A plastic pipe is not conductive, therefore it cannot introduce Earth potential into the installation but it must be verified that there are not any fortuitous connections with Earth throughout the installation.

View our 'Protective bonding habits' article

Back to top

Can I use PME earthing system for electric vehicle charging equipment?

Whilst BS 7671:2018 does not preclude the use of PME earthing arrangements, it’s not easy to meet the requirements of Regulation 722.411.4.1.

The first method is that the charging point is connected to a balanced three-phase installation, this is to ensure that in the event of an open circuit PEN conductor that the touch voltage does not exceed 70 V. This is difficult to achieve as most three-phase installations have single-phase loads connected which will cycle in and out, changing the balance of the load; or

the main earthing terminal of the installation is connected to an additional earth electrode, the resistance is determined according to the load for the installation and is likely to require a resistance in single digits which will be difficult to achieve and be cost-effective; or

the charging point incorporates a device which disconnects the live and earth conductors of the supply in the event of a voltage exceeding 70 V between the protective conductor and Earth. Devices of this nature are not available on the market at this time.

Back to top

Do circuits supplying electric vehicle charging equipment require RCD protection?

The requirements for RCD protection refer to the point itself as opposed to the final circuit supplying the equipment. However, there may be other requirements for the final circuit to be RCD protected such as for fault protection, if it were connected to a TT earthing arrangement. If this is the case, it is important to select the correct Type of RCD and ensure selectivity upstream from the charging equipment.

BS 7671:2018 Regulation 722.531.2.101 requires the charging point to be RCD protected by its own RCD of at least a Type A, having a residual operating current not exceeding 30 mA. It is likely that the RCD will be installed within the charging equipment but this must be verified.

Back to top

As a plumber can I change an electric shower?

The Electricity at Work Regulations requires all persons carrying out electrical work to be competent. The person requires sufficient skill, knowledge and experience to carry out the work and relevant inspection and testing.

BS 7671:2018 Regulation 134.1.1 states that persons carrying out electrical works shall be skilled. A skilled person as defined in BS 7671 is a person who possesses, as appropriate to the nature of the electrical work to be undertaken, adequate education, training and practical skills, and who is able to perceive risks and avoid hazards which electricity can create.

An assessment on the existing installation will be required in accordance with BS 7671:2018 Regulation 132.16, this is to determine if the existing installation including the distributors equipment and earthing and bonding arrangements are adequate for the altered circumstances.

A location containing a bathtub or shower basin is considered a special location, installing a shower unit would be considered notifiable works under part P of the Building Regulations as it would be deemed a special location.

Back to top

As a gas engineer can I install protective bonding to the gas pipework?

The Electricity at Work Regulations requires all persons carrying out electrical work to be competent. The person requires sufficient skill, knowledge and experience to carry out the work and relevant inspection and testing.

BS 7671:2018 Regulation 134.1.1 states that persons carrying out electrical works shall be skilled. A skilled person as defined in BS 7671 is a person who possesses, as appropriate to the nature of the electrical work to be undertaken, adequate education, training and practical skills, and who is able to perceive risks and avoid hazards which electricity can create.

An assessment on the existing installation will be required in accordance with BS 7671:2018 Regulation 132.16, this is to determine if the existing installation including the distributors equipment and earthing and bonding arrangements are adequate for the altered circumstances.

This would be considered an alteration to an existing installation, therefore, a minor works certificate would need to be issued to certify the works. However, it would not require notification under part P of the Building Regulations.

Back to top

What is the difference between earthing and bonding?

Earthing is not bonding, and bonding is not earthing, they are different concepts.

Earthing is provided to connect exposed-conductive-parts to the main earthing terminal to provide a path for fault current in the event of a fault. Whereas protective bonding is provided to connect extraneous-conductive-parts to the main earthing terminal to prevent a potential difference occurring and creating a hazardous touch voltage.

Back to top

Does a metal oil tank need protective bonding?

The oil tank does not require protective bonding, but the service pipe will require protective bonding to be installed within 600mm of the point of entry to the installation if it is an extraneous conductive part.

An extraneous-conductive-part is defined in BS 7671:2018 as, a conductive part liable to introduce a potential, generally Earth potential, and not forming part of the electrical installation.

Some fuel storage tanks may require lightning protection in accordance with BS EN 62305, specialist advice should be sought to determine the requirements.

View our 'Protective bonding habits' article in Wiring Matters magazine

Back to top

Does the metal furniture in commercial catering kitchens need bonding?

Whilst it is commonly seen, there is no requirement in BS 7671:2018 to install protective bonding to metallic kitchen furniture, it is not an exposed conductive part and is unlikely to be an extraneous-conductive-part, therefore it does not require earthing or bonding.

View our 'Protective bonding habits' article in Wiring Matters magazine

Back to top

How do I carry out a calculation to check if armouring of SWA is suitable as a circuit protective conductor (CPC)?

As the armouring of a steel wired armoured cable is manufactured from steel, the copper equivalent cross-sectional area must be calculated, taking the thermal constraints of the material into account. BS 7671 Table 54.7 provides guidance on calculating the cross-sectional area of the armouring of a steel wired armoured cable and Table 54.4 provides values of k for the sheath or armour of a cable being used as a protective conductor.

IET Guidance Note 1, Tables D6 – D10b provides examples of cable sizes which are suitable to use the armouring as the CPC.

Back to top