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Wiring Matters

Wiring Matters 54 - Special Edition, 2015

RCDs: protection of cables concealed in walls or partitions

A change to the requirements of Regulation Group 522.6, relating to RCD protection of cables concealed in walls or partitions, forms part of BS 7671:2008+A3:2015 (Seventeenth Edition of the IET Wiring Regulations), which was published on 1 January 2015 and comes into effect on 1 July.  

Reference to ‘under the supervision of a skilled or instructed person’ has been removed from the regulations concerned.  

Consequently, the requirement to provide RCD protection to cables concealed in a wall or partition will apply to all installations, except where one of the other permitted methods of protection is employed (such as the use of cables having an earthed metallic covering or cables enclosed in an earthed metal conduit). The RCD must have a rated residual operating current (IΔn) not exceeding 30 mA and an operating time not exceeding 40 ms at 5 IΔn.

As at present, the revised requirements apply to cables at a concealed depth of less than 50 mm from the surface of a wall or partition and, irrespective of depth, if the cable is in a partition constructed of metallic parts other than fixings (such as nails or screws).

There is still an exception for cables forming part of a SELV or PELV circuit.

Cables must still be installed within the ‘safe’ zones illustrated in Figure 1, except where they have one of the other permitted methods of protection mentioned above, or they form part of a SELV or PELV circuit.

Figure 1 – Zone prescribed in Regulation Group 522.6

Image of zones prescribed in Regulation Group 522.6