Every month Technical Services receive numerous calls from SELECT members on a number of different subjects. Some commom questions and answers can be found here.
What is the current standard for electrical installations in Britain?
The current standard for electrical installations in Britain is BS 7671: 2008 incorporating Amendment No.1:2011 Requirements for Electrical Installations (IET Wiring Regulations 17th Edition).
These regulations came into effect on 1 January 2012. Installations designed after 31 December 2011 are to comply with BS 7671: 2008(2011). Installations designed to BS 7671:2008 prior to 1st January 2012 can be constructed in accordance with BS 7671:2008.
Is BS 7671 (IET Wiring Regulations) a mandatory requirement?
No, BS 7671 is not mandatory. British Standards are in effect codes of practice which can be followed to comply with mandatory requirements such as the Electricity at Work Regulations 1989 and the Building (Scotland) Regulations 2004.
My house has a consumer unit with rewireable fuses and I have been told by an electrician that I need to have the house rewired and the consumer unit replaced to ensure compliance with current regulations, is this true?
Existing installations installed to an earlier edition of the wiring regulations (BS 7671) may not comply with the current requirement. This, however, does not necessary mean that they are unsafe for continued use or require upgrading. The condition of the installation would determine whether or not a rewire and/or change of consumer unit is necessary.
Note 1: There may be several reasons why a full or partial rewire of a house may be recommended by a reputable electrician, such as the following (this list is not exhaustive):
- Deteriorated cable insulation, particularly pre-PVC types (e.g. rubber or lead-sheathed cables) which were typically installed prior to the 1960s.
- Lack of provision of earthing facilities, e.g. at light fittings which require to be earthed.
- Deterioration of cables, connections or accessories due, for example, to fire, overheating or water ingress.
- Overloading due to an insufficient number of circuits.
- Major structural alterations to the house affecting a large proportion of the existing wiring (which may suffer damage in the process).
- Sub-standard additions or alterations to the wiring having been carried out (particularly where unsafe ‘DIY’ work has been involved).
- Test results indicate faulty wiring.
Note 2: There may be several reasons why the replacement of a consumer unit in a house may be recommended by a reputable electrician, such as the following (this list is not exhaustive):
- The house is being fully or partially rewired, due for example to any of the reasons listed in Note 1 above.
- The consumer unit cover is missing or the consumer unit is damaged, exposing live parts.
- The consumer unit or protective devices have been damaged due to fire or overheating.
- There are insufficient ways in the consumer unit for the number of existing circuits and/or circuits being added.
- Suitable Residual Current Device (RCD) protection is not provided for –
- all circuits where the means of earthing is an earth electrode.
- existing socket-outlets which may reasonably be expected to supply portable equipment for use outdoors.
- any circuits being added, where such protection is required by BS 7671: 2008(as amended).
- any existing circuits being altered, where such protection is required by BS 7671: 2008(as amended).
Can you briefly explain the new scheme for certification of electrical installations where a building warrant has been issued, such as for a loft conversion?
Where can I find an electrical contractor who is registered in the Scottish Building Standards Scheme for electrical installations?
The Building (Scotland) Act 2003 introduced the concept of self-certification. This system allows qualified and experienced building professionals and tradespersons to be responsible for ensuring compliance with Building Regulations without the detailed scrutiny of Local Authorities. Persons wishing to become certifiers must have the appropriate qualifications and experience to become Approved Certifiers and be employed by reputable organisations known as Approved Bodies who are registered in a relevant Certification Scheme.
With regard to electrical installations, SELECT is a Certification Scheme Provider and electrical contractors meeting the criteria can join the SELECT Scheme and become Approved Bodies, which enables them to employ Approved Certifiers who provide the appropriate Electrical Certification. More information on this Scheme can be found at www.scotland.gov.uk/bsd
The list of Approved Bodies, i.e. companies who are registered in the scheme and employ Approved Certifiers, are listed under the Local Authority areas where they are willing to carry out work. The lists can be found at www.scotland.gov.uk/bsd
under Certification/Certification Register.
How close are electrical accessories such as socket-outlets allowed near a sink?
This question is addressed in the recently updated IET Guidance Note 1 (GN 1) Selection and Erection, which gives guidance on Part 5 of BS 7671:2008(as amended). A summary of the guidance is given below:
In Appendix C of GN 1, Sub-Section C.6.2 explains that there is no specific minimum distance given in BS 7671 for accessories near a sink. The accessory installed, however, must be of a design appropriate to the external influences (such as water splashing) likely to be encountered. A general recommendation given is that BS 1363 (domestic type) accessories mounted above sink (worktop) height should be at a horizontal distance of not less than 300mm from the edge of the sink top.
Note: The Scottish Building Standards Technical Handbooks recommend that a socket-outlet mounted above a worktop is to be at a height of at least 150mm.
Does a flush metal accessory box require to be connected to a circuit protective conductor (CPC) when the wiring including the CPC is terminated in the accessory?
As above this question is addressed in the recently updated IET Guidance Note 1 (GN 1) Selection and Erection, which gives guidance on Part 5 of BS 7671:2008 (as amended). A summary of the guidance is given below:
In Chapter 3 of GN 1, Sub-Section 3.8.4 explains in detail the question of the need for ‘earthing tails’. Flush metal accessory boxes should be considered to be exposed-conductive-parts and require to be earthed. Where, however, the CPC terminates in the accessory, the view of the IET policy committee is that provided the metal box has at least one fixed lug, and an accessory such as a socket-outlet has an earth strap connecting its earthing terminal to one or both fixing holes, the box can be considered to be earthed via the metal-to-metal contact of the fixing screw and the lug. An ‘earthing tail’ is not therefore required in these situations.
Where, however, the CPC is formed by metal conduit, metal sheath or armour of a cable etc. which terminates in the metal box, an ‘earthing tail’ is necessary between the box and the earth terminal on the accessory if provided (see Regulation 543.2.7).
Are you allowed to add cables with the new harmonised cable colours to an existing installation which has the old colours?
Yes you can use the new cable colours in an older installation. Regulation 514.14 of BS 7671: 2008 (as amended), however, requires a warning notice to be fixed at or near the distribution board with wording as follows:
This installation has wiring colours to two versions of BS 7671. Great care should be taken before undertaking extension, alteration or repair that all conductors are correctly identified.
I am upgrading an existing shower in a bathroom from 7 kW to 9.5 kW. Can I use the existing 6mm2 PVC sheathed cable?
The current-carrying capacities of cables are given in Appendix 4 of BS 7671: 2008 (as amended) and the cable size used depends on the load, the installation method and corresponding reference method. For example cables installed in a building void are Reference Method B. From Table 4D2A Reference Method B (Column 4) 6mm2 sheathed cables can carry up to 38 amps. The current rating of a 9.5 kW load is 41 amps. The cable is therefore not suitable for the installation method described. It is therefore unlikely that the 6mm2 cable would be suitable for a 9.5 kW shower.
Note: For cables installed in thermal insulation Table 4D5 should be used. This is an even more onerous installation method than cables installed in building voids without thermal insulation.
Can I install a consumer unit in a bathroom cupboard?
The inside of a bathroom cupboard is effectively outside the bathroom zones and in this respect the consumer unit could be fitted in the cupboard. Regulation 512.2.1 of BS 7671: 2008 (as amended) however requires equipment to be of a design appropriate to the situation in which it is to be used and the conditions likely to be encountered. Care should therefore be taken to ensure that any such cupboard is sealed as much as possible to prevent the ingress of moisture which could cause premature deterioration of the consumer unit, protective devices or connections.
What is the procedure for ensuring that an existing electrical installation is in a safe condition for continued use?
The procedure for ensuring that an installation is safe is for a competent person to carry out an inspection and test of the installation and provide a report on its condition. This is known as Periodic Inspection and Testing and the procedure is given in Part 6 of BS 7671: 2008 (as amended).
From 1 January 2012, following the Periodic Inspection and Testing of an existing installation, an Electrical Installation Condition Report (EICR) will be issued, as a Periodic Inspection Report no longer meets the requirements of BS 7671 from that date.
The EICR will list under Section K ‘Observations’ any parts of the installation which require attention. These are Coded C1, C2, C3 or Further Investigation Required, depending on the urgency of any deviations found. The report also gives a general summary of the condition of the installation.
Note: Following a Periodic Inspection and Test of an installation an Electrical Installation Certificate should not be issued as such certificates should only be used for new installations including additions and alterations to existing installations.
How does SELECT deal with complaints against members?
The complainer should first try to resolve the problem directly with the contractor.
Where this fails, or is not possible, SELECT will request that the complaint is submitted in writing on a Complaint Form available from SELECT. Subject to certain conditions, described in the Complaints Procedure which accompanies the form, the complaint is then passed to the member for a written comment including any action that can be taken to resolve the problem.
Where appropriate one of the SELECT Technical Advisers will carry out an inspection of the installation and prepare a report listing any deviations from the appropriate standard(s) identified. This report is then passed to the contractor to carry out rectification of the work. In most instances a further inspection is carried out by SELECT to satisfy the client that rectification has resulted in the installation complying with the standard(s).