Editing Residual-current device (section)

=== United Kingdom ===
{{main|Electrical wiring in the United Kingdom}}
The current (18th) edition of the [[BS 7671|IET Electrical Wiring Regulations]] requires that all socket outlets in most  installations have RCD protection, though there are exemptions. Non armoured cables buried in walls must also be RCD protected (again with some specific exemptions). Provision of RCD protection for circuits present in bathrooms and shower rooms reduces the requirement for supplementary bonding in those locations. Two RCDs may be used to cover the installation, with upstairs and downstairs lighting and power circuits spread across both RCDs. When one RCD trips, power is maintained to at least one lighting and power circuit. Other arrangements, such as the use of RCBOs, may be employed to meet the regulations. The new requirements for RCDs do not affect most existing installations unless they are rewired, the distribution board is changed, a new circuit is installed, or alterations are made such as additional socket outlets or new cables buried in walls.

RCDs used for shock protection must be of the 'immediate' operation type (not time-delayed) and must have a residual current sensitivity of no greater than 30{{nbsp}}mA.

If spurious tripping would cause a greater problem than the risk of the electrical accident the RCD is supposed to prevent (examples might be a supply to a critical factory process, or to life support equipment), RCDs may be omitted, providing affected circuits are clearly labelled and the balance of risks considered; this may include the provision of alternative safety measures.

The previous edition of the regulations required use of RCDs for socket outlets that were liable to be used by outdoor appliances. Normal practice in domestic installations was to use a single RCD to cover all the circuits requiring RCD protection (typically sockets and showers) but to have some circuits (typically lighting) not RCD protected.<ref>{{cite web | url=https://www.consumerunitworld.co.uk/what-is-an-rcd-and-how-does-it-work-337-c.asp | title=What is an RCD and How Does it Work? - The RCD and the UK Electrical Wiring Regulations | accessdate=2017-12-23 | publisher=Consumer Unit World }}</ref> This was to avoid a potentially dangerous loss of lighting should the RCD trip. Protection arrangements for other circuits varied. To implement this arrangement it was common to install a [[consumer unit]] incorporating an RCD in what is known as a split load configuration, where one group of circuit breakers is supplied direct from the main switch (or time delay RCD in the case of a [[Earthing_system#TT_system|TT earth]]) and a second group of circuits is supplied via the RCD. This arrangement had the recognised problems that cumulative earth leakage currents from the normal operation of many items of equipment could cause spurious tripping of the RCD, and that tripping of the RCD would disconnect power from all the protected circuits.