Legislation & Code of Practice Guidelines in the UK
Here in the UK, there is a growing body of legislation, regulations, codes of practice and recommendations which is accelerating the rate of adoption of RCDs and widening considerably their areas of application. The 17th Wiring Regulations dictates a trend which is clear and cannot be ignored.
Health and Safety at Work Act 1974
The Health and Safety at Work Act 1974 and the Electricity at Work Regulations 1989 are statutory documents and non-compliance constitutes a criminal offence.
Electricity at Work Regulations 1989
Because of the wide range of work covered by the regulations, the requirements are framed in general terms. However, the Memorandum of Guidance on the above regulations, a clear case is made for using RCDs as an additional safeguard for earthing (Reg 8). Also under clause 12 (isolation), it advises that the use of RCDs will meet the provision of isolation.
IET Wiring Regulations 2008 - Amendment 3 = 2015
Although BS 7671 (2008) (Other wise known as the 17th Edition IET Wiring Regulations) is a guidance document in the event of an accident, failure to comply could result in prosecution by the HSE. The HSE also accepts that compliance with BS 7671 also gives compliance with The Electricity at Work Act.
a) Fault Protection
Chapter 411.1 (ii) States that Fault protection is provided by protective earthing, protective equipotential bonding and automatic disconnection in case of a fault, in accordance with Regulations 411.3 to 411.6.
Chapter 411.4.7 confirms that if an RCD is used to provide fault protection, it is not necessary to undertake the disconnection calculations required for overcurrent devices. The values specified in Table 41.1 may be used. An RCD will always trip within 0.2 seconds.
b) Basic Protection
Chapter 411.1 (i) States that basic protection is provided by basic insulation of live parts or by barriers or enclosures, in accordance with section 416 or where appropriate, section 417 (Obstacles; placing out of reach)
c) Construction Site Installations
704.410.3.10 states that a circuit supplying a socket-outlet with a rated current up to and including 32A and any other circuit supplying handheld electrical equipment with rated current up to and including 32A shall be protected by:
i) Reduced low voltage (Regulation 411.8), or
ii)Automatic disconnection of supply (Section 411) with additional protection provided by an RCD having the characteristics specified in Regulation 415.1.1, or
iii) Electrical separation of circuits (Section 413), each socket- outlet and item of handheld electrical equipment being supplied by an individual transformer or by a separate winding of a transformer, or
iv) SELV or PELV (Section 414) d) Caravans
Chapter 721.411.1 - States where protection by automatic disconnection of supply is used, an RCD or RCBO complying with BS EN 61008-1 or BS EN 61009 interrupting all live conductors shall be provided having the characteristics specified in Regulation 415.1.1, and the wiring system shall include a circuit protective conductor which shall be connected to: i) The protective contact of the inlet, and
ii) The exposed conductive parts of the electrical equipment, and
iii) The protective contacts of the socket outlets +44 (0) 1279 772 772 18 +44 (0) 1279 422 007 e) Swimming Pools
Chapter 702.55.1 states that in zones 0 and 1, it is only permitted to install fixed current using equipment specifically designed for use in a swimming pool, in accordance with the requirements of Regulations 702.55.2 and 702.55.4.
Equipment which is intended to be in operation only when people are outside zone 0 may be used in all zones provided that it is supplied by a circuit protected according to Regulation 702.410.3.4.
It is permitted to install an electric heating unit embedded in the floor, provided that it:
i) Is protected by SELV (Section 414), the source of SELV being installed outside zones 0, 1 and 2. However, it is permitted to install the source of SELV in zone 2 if its supply circuit is protected by an RCD having the characteristics specified in Regulation 415.1.1.
f) Agriculture and Horticultural Premises
Chapter 705.411.1 States that circuits supplying socket outlets shall be RCD protected.
g) Functional Testing of RCDs
‘Regulation 612.13.1’ - states that where protection and/or additional protection is to be provided by an RCD, the effectiveness of any test facility incorporated in the device shall be verified. Frequency of testing can vary between RCD types. Any Residual Current Devices (RCDs) should be operated by means of the test button at least monthly to ensure that they remain effective. The table below gives the required trip times to comply with BS 7071 for portable RCDs and BS 7288 for RCD Socket outlets.
Fault Current Trip Time
0.5 x In No trip permissible
1 x In <200mS
5 x In <40mS Where ‘In’ is the rated trip current of the RCD in milliamps.
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