EV installations: RCCB or CBR?

In EV charging applications, if you need to install RCD protection upstream what do you use?

BS 7671 722.531 recognises the use of RCBOs, RCCBs and CBRs as RCDs suitable for fault protection in EV charging circuits. What are the key points to consider when selecting an RCD to provide fault protection for the cables feeding one or more EV charge points downstream?

Final customer/user

RCBOs (BSEN61009) and RCCBs (BSEN61008) are designed for use by ‘ordinary persons’. Consequently, the standards do not allow RCBOs or RCCBs to have adjustable characteristics. Don’t waste your time looking for unicorns – use a horse.

CBRs (BSEN60947-2) can have adjustable settings for residual currents >30mA. These products are designed for use by ‘instructed persons’ – see CBR definition in BS7671 Part 2.

RCBO

Effective as a final distribution product, readily available in 30mA, 6 <40A ratings. They are not manufactured with a selective time delay characteristic, making 100 and 300mA versions unsuitable for full selectivity with 30mA devices downstream.

RCCB

Available in a wide range of characteristics and types – note BSEN61008 maximum rating <125A. Using a 300mA selective time delay version installed upstream of 30mA RCDs will achieve full selectivity. The fixed characteristics suit domestic, schools and similar installations, which are not under the permanent control of an instructed person (electrically).

CBR

Generally applied in EV charging applications where the number of chargers or the mod of charging exceeds the 125A current limit for RCCBs. Note BSEN60947-2 Annex B Versions ≤30mA must have fixed residual current and time settings. Versions >30mA can have adjustable residual current and time settings, giving added flexibility on site – see BS7671 411.4.4 Note 2 relating to the time delay setting.

Doepke, doepke.co.uk