Figure 1 – Operating principle of the residual current device The regulations recommend, therefore, that the preferred method of earth fault protection for installations in TT systems be achieved by RCDs, such that the product of its residual operating current and the loop impedance will not exceed a … The idea that you will need to have a dual RCD consumer unit for all circuit and that every circuit needs to be RCD protected is not also correct and no regulation says that. The harmonised regulations will not state that lights are not protected by RCDs, they will recommend that circuits are divided to prevent hazards/danger through lose of power.So that on most occasions will require circuits to be split across RCD devices or constructed in a manner that excludes the need for RCD protection. I can run a radial circuit to an immersion heater point wired via a fused spur & it does not require additional protection by means of an RCD … A new, revised version of Regulation 411.3.3, relating to RCD protection of socket-outlets, forms part of BS 7671:2008+A3:2015 (IET Wiring Regulations Seventeenth Edition), which was published in January 2015 and comes into effect on 1 July. We have an old type of the fuseboard so I would need to allow for separate enclosure fitted with RCDs. You would not, in my opinion, be required to provide RCD protection for other circuits within the bathroom, although this could be commented on in any certification provided. As per the reg section 522.6, I am supposed to use additional RCD protection for the cables where they are concealed in walls and have a … This time its the design of an office building and I am concerned for the use of RCD protection specifically for the Lighting circuits. 411.3.4: Again 30 mA RCD additional protection for all lighting circuits. The current and new versions of the regulation are shown side by side below. With the 18th Edition of BS 7671 just around the corner, we take a look back at the last amendment to the 17th Edition of BS 7671 and the requirements for using RCDs in non-domestic environments. However all outside sockets needs to be RCD protected. Take for example all lighting circuits regardless of the method require additional protection by means of an RCD in household or similar. Regulation 531.3.5.3.2.201 requires that, where Class I enclosures are used (that is, earthed metalwork) on TT systems with RCD protection on outgoing circuits, all live conductors on the supply side of the RCD – that is, the internal cable links – must have double or reinforced insulation. Good day all, I have a client who wishes to replace lighting within the building and the simple question I have is do I have to allow for RCD protection for altered circuits as per 18th edition or can I omit the RCD as we can treat it as retrofit? Shower unit looking at manufactures instruction will also need RCD protection. For example, an outdoor socket without RCD protection would fall into this category due to the use with portable outdoor tools, particularly in the case of electric lawnmowers. Where circuits are used to supply “mobile outdoor equipment”. Answer: If the only work you are carrying out is the replacement of the light fitting, I would recommend that you provide RCD protection for the lighting circuit. By comparing the two versions, it can be seen that the new version: The latest amendment to the IET’s Wiring Regulations reinforces the requirement for using residual current devices (RCDs) in non-domestic