Our Voltimum Experts answer your questions on a daily basis in our Technical Expertise area. This one, concerning a commercial refurbishment and the need for RCD protection, is answered by the NICEIC:
The distribution board is an old Federal Electric unit and the RCBOs are, despite a lot of searching, proving difficult to source. Am I covered by the 'supervision' rule, or do I have to fit RCD protection to these extended circuits?
The extension to the circuits is via twin and earth cable enclosed in dry lined partition walls connected to the old singles wiring.
Answer: For cables installed <50mm from the surface of a wall or partition, Regulation 522.6.7 states that where the installation is not under the supervision of a skilled or instructed person, additional protection shall be provided by a 30mA RCD. You will, therefore, need to satisfy yourself that any supervision is indeed skilled or instructed.
Skilled or instructed supervision is required to ensure that dangers which electricity may create are avoided. It must be demonstrated to you, the designer of the electrical installation that a suitable risk assessment has been conducted and the outcome used to produce and document a suitable robust system which ensures that the installation is adequately supervised by skilled or instructed person(s) while in use.
Alternatively, you should comply with Regulation 522.6.6 (i), (ii), (iii), or (iv) and the requirements of Regulation 411.3.3 with regard to additional protection of socket outlets by 30mA RCD.
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