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Fitting Correct RCD’s For New Electrical Apparatus


The majority of homes in the UK have type “AC” rated Residual Current Devices (RCD’s) fitted as standard. These are used for general purpose and can detect and respond to AC sinusoidal wave only. They offer no DC fault protection.

In the 18th Edition BS 7671:2018 – requirements for electrical installations - IET wiring regulations 531.3.3 covers general application areas and futureproofs the regulations recognising the need to verify the selection of the RCD based on the residual current and characteristics of the appliance or loads being connected to the installation. As new electrically powered devices and appliances, ranging from phone/laptop chargers, LED lighting and induction hobs to washing machines, boilers and replacement high-efficiency pumps and circulators, are introduced to the market, it is crucial that the correct RCD protection is identified and fitted so that DC protection is in place where required.

Property owners and installers need to be made aware of these requirements and take action to ensure the safety of the installation. These types of appliances can produce residual currents that are not compatible with AC Residual Current Devices. Consequently, the 18th Edition has been updated to be aligned with existing Electrical Safety Standards adopted in other countries. In Germany and several other western European countries, AC rated RCD’s are no longer allowed due to their restricted protection scope.

Therefore, and given that every installation is unique, the BPMA suggests that responsibility for selecting the correct RCD, squarely rests with the qualified installer or electrician. They should always follow the appliance manufacturers instructions on which type of RCD to use; the information for which can normally be found in the Installation Operating Manual (IOM), or in downloadable form on their website. There are many types of RCD’s available, displaying a range of applicable symbols such as AC, A, F, B and B+ which readily allows for the correct one to be selected and installed.

For further information, please contact Gary Wilde, Technical Services Officer at the BPMA by phone on +44 (0) 121 601 6692 or email at g.wilde@bpma.org.uk.

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