Is an external type-A 30mA RCD still needed, when there is built-in type-A 30mA and DC 6 mA protection at an EV charger?
Over the past years, we have seen a clear trend of using RCD Type A and RDC-DD for home charging applications. Some EV charger manufacturers declare built-in type-A 30 mA and DC 6 mA residual current protection at their EV chargers. It is nice to have built-in type-A 30mA protection at EV chargers as back-up protective measures of the external type-A 30mA RCDs, but the external type-A 30mA RCDs shall not be removed.
IEC/EN 61851-1:2017 standard specifies two optional residual current protection measures for mode-3 EVSE (Electric Vehicle Supply Equipment) as followings
  • Option 1 : RCD Type B  (IEC 60947-2 type-B mRCD/CBR or IEC 62423 type-B RCCB)
  • Option 2: RCD Type A (IEC 61008-1 type-A RCCB, IEC 61009-1 type-A RCBO or IEC 60947-2 type-A mRCD / CBR ) and RDC-DD (IEC62955 RDC-PD or RDC-MD)

Over the past years, we have seen a clear trend of using the aboving option 2 of RCD Type A and RDC-DD for home charging applications.  More specifically, the main-stream implementation approaches are illustrated in diagram 1 (left) and diagram 2 (middle) of the following pictures. E.g. our BRCS01-ADC-H2 and BRCS01-DC6-H2 residual current sensor have been widely used by mode-3 EVSE manufacturers. Some mode-3 EVSE manufacturers tell their users and installers that an external type-A 30 mA RCD is not necessary with built-in type-A 30 mA and DC 6 mA residual current protection at their EV chargers – as illustrated in diagram 3 (right).
Type A RCD and IEC 62955 RDC-DD
Diagrams: Integration of AC/DC residual current sensors for mode-3 EVSE 

Our experts believe it is not a good idea to solely rely on built-in type-A 30 mA protection that consists relays/contactors, charging controller and AC/DC residual current sensors. In the testing report of EV chargers with built-in type-A 30 mA protection, it is often stated “Partial Testing Items in IEC 61008-1". In other words, the EV chargers declaring IEC 61008-1 type-A 30 mA protection is unlikely to as robust as a traditional DIN-rail type-A 30mA RCD fully tested. 


For example, a traditional Din-rail type-A 30 mA RCD is designed and tested to withstand harsh climatic tests defined in IEC 61008-1 or IEC 61009-1 - such as in acid and humid environment. Some professional manufacturers of traditional Din-rail type-A 30 mA RCDs even consider severe conditions with SO2. Another example is a traditional type-A 30 mA RCDs can trips within 40ms in the occur of residual current at switch-on stage, but this feature might not be guaranteed by built-in type-A 30 mA protection at EV chargers. It might cause electrical accidents for the electrician, if someone switch on the MCB upstream the EV chargers unintentionally (the above diagram 3). 

The type-A 30mA protection is vital for electrical safety. It costs only 20~30 EUR/GBP/USD to buy a traditional Din-rail type-A 30 mA RCD, which is affordable for EV users. The manufacturers had spent years in improving the design and manufacturing of Din-rail type-A RCDs until they became safe and reliable.  Therefore, it is nice to have built-in type-30mA protection at EV chargers as back-up for the external type-A 30mA RCDs, but the external type-A 30mA RCDs is not suggested to be removed.
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