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RCD protection for socket-outlets in the 18th Edition (BS 7671:2018)

(c) IET anbd BSI

Image from IET web-site

The publication of the 18th Edition of the IET WIring Regulations (forthcoming BS 7671:2018) is imminent, and BSI and the IET have publicised some of the key changes, which can be viewed on the IET web-site.

When Amendment No. 3 to BS 7671:2008 was published in 2015, we reported on changes to RCD protection for socket-outlets in Regulation 411.3.3, with socket-outlets in AC systems rated up to and including 20 A requiring RCD protection unless a risk assessment stated otherwise.

With the 18th Edition, Regulation 411.3.3 requires all socket-outlets in AC systems rated up to and including 32 A to be protected by a 30 mA RCD, the only exception being for installations other than in dwellings, where a documented risk assessment determines RCD protection is not necessary.

The salient facts here for Regulation 411.3.3 that designers will be obliged to consider are:

  1. The upper rating for socket-outets requiring RCD protection in accordance with Regulation 411.3.3 has increased from 20 A to 32 A.
  2. There is no longer an exception to Regulation 411.3.3 for dwellings, regardless of whether a risk assessment was in place, and regardless of the appliance(s) to be served. An AC appliance that is not compatible with 30 mA RCDs in dwellings must therefore be permanently connected to the electrical installation, unless it is rated for use with a socket-outlet exceeding 32 A.
  3. If an exception is made in installations other than dwellings, to omit RCD protection for socket-outlets rated at 32 A or less, there must be a documented risk assessment that determines RCD protection is not neccessary.
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