It depends on the supply arrangement and where the socket-outlet is installed.

If it's a single-phase supply with a Neutral and a Line conductor

Regulation 411.3.3 applies and a 30 mA RCD is required for socket-outlets rated upto and including 32 A. RCDs may also be required because of the cable route to the socket-outlet (e.g. Regulation 522.6.202) or because of a requirement of a Part 7 special location.

If it's Reduced Low Voltage (55-0-55 V from a safety isolating transformer)
Regulation 411.3.3 applies for socket-outlets rated up to 32 A. It depends where the socket-outlet is, and other factors including whether RCDs are used for ADS. RCDs may be required if Regulation 522.6.202 applies to the circuit, or if RCDs are used for protection against fire, or as a result of Part 7 requirement (e.g. Regulation 705.422.7 or as above)

(Just in case anyone asks - if a Part 7 requirement for RCDs is numbered 7ab.411.x.y, then that modifies Regulation 411.x.y which is a requirement for ADS, not the reduced low voltage system, which would be numbered 7ab.418.x.y. Therefore Regulation 701.411.3.3 would not apply for a reduced low voltage system in a location containing a bath or shower, provided all the requirements for RLVS are met)


Edited as p[er later post, deletions in strikethrough, additions underlined

(Just in case anyone asks - if a Part 7 requirement for RCDs is numbered 7ab.411.x.y, then that modifies Regulation 411.x.y which is a requirement for ADS, not the reduced low voltage system, which would be numbered 7ab.418.x.y. Therefore Regulation 701.411.3.3 would not apply for a reduced low voltage system in a location containing a bath or shower, provided all the requirements for RLVS are met)

OK, I'll ask! ?


It seems to me that RLV is part of 411 rather than 418 - 411.8 to be precise. So if the requirements of 411.3.3 apply to 411.4 (LV TN systems), and 411.5 (LV TT systems) and presumably 441.6 (IT systems), where's the logic in saying it doesn't likewise apply to 411.7 (FELV) or 411.8 (RLV)?


(Although I can agree there should be such logic - after all the while point of RLV was that it should be safe for shocks due to L-PE faults without relying on disconnection at all, and I can see all sorts of practical problems finding RCDs that'll operate at FELV voltages).


   - Andy.

Apolgies Andy - yes you are correct, I must have had a mental flip, the requirements of 411.8 are in addition to 411.3, I did mis-number the requirements.for RLV in my head ... so I''ve edited my previous post accordingly.

To be clear, RCD protection is not required by 7671 for socket outlets on reduced low voltage systems such as are commonly found on construction sites in the U.K.

To be clear, RCD protection is not required by 7671 for socket outlets on reduced low voltage systems such as are commonly found on construction sites in the U.K.

Agreed - now I look carefully it's spelled out clearly in the last paragraph of 411.3.3 itself (promoted from just a NOTE in the 17th) - "The requirements of Regulation 411.3.3 do not apply to FELV systems according to Regulation 411.7 or reduced low voltage systems according to Regulation 411.8".

    - Andy.