The requirements for charging of electric vehicles was the subject of amendment 1 to BS 7671 issued in February 2020 and came into effect in July 2020.
Paul Collins, Technical and Training Manager at Hager, covers key topics relating to the supply of electrical charging equipment and the appropriate method for connecting a car charging circuit.
Are RCDs required to supply a car charger?
Yes, regulation 722.531.3 requires that an RCD (Max 30mA) supplies a car charger and the RCD shall disconnect all live conductors. This includes the Neutral, therefore, the single pole RCBOs should not be used for this application.
Some car charger manufacturers quote a RDC-DD, what is this?
An RDC-DD is a Residual Direct Current – Disconnecting Device. This is often built within the car charger equipment to monitor and, if necessary, disconnect should any DC problems appear on the AC side of the installation, which could affect the operation of RCDs.
If a car charger does not have any RDC-DD then what type of RCD is required?
If the car charger does not have any RDC-DD then you will need a Type B RCD supplying the car charger. This is because the Type B can detect this DC, still work and disconnect if required.
What type of RCD should be used if the car charger has an RDC-DD that will detect and disconnect any DC issues above 6mA?
In this case, a Type A RCD can be used. This is because the Type A can still work correctly up to a level of 6mA DC. Over 6mA, however, this Type A device could be affected and possibly blinded and potentially stop working. This is the preferred option as Type A are now very common and usually the lowest price. Therefore, most car charger manufacturers have a 6mA RDC-DD built in.
RCD in a series:
In some scenarios, someone may supply a car charger from an existing installation where they may consider installing from a spare way in the consumer unit. If there is no space for the new Type A RCD, they may consider installing this closer to the car charger.
The type A RCD will not be affected by DC up to 6mA. However, it’s important to consider the time frame of when the RCD was installed in the consumer unit. If it was installed some time ago, it could be a Type AC. This RCD may be also supplying other circuits within the house which could then be affected or in some cases blinded by any DC that may be coming from the car. These other circuits then may not have any residual current protection, the consequences of which could be severe.
For further info, download your copy of Hager’s ‘Bitesize Guide on EV Charging’ by visiting: https://hager.com/uk/p/catalogues-brochures.
