Regulation stating a type AC RCD can not be upstream from a type A RCD

Question

Hi 
 
 I found an EV charger today with built in type A RCD + RDC-DD connected to a type AC RCD in the consumer unit, the AC RCD is also protecting 3 other circuits including sockets. I know this is incorrect because the type AC RCD could be blinded by DC currents, but I am struggling to find a regulation to reference when providing information to the customer? 
 
 Thanks 
 
 Alan

Yassir Khalil · Answer

Hi Guys, Im new to the Forum but I hope this information can help Which I found earlier. 
 Selectivity of RCD types - Wiring and the Regulations BS 7671 - IET EngX - IET EngX (theiet.org) 
 Also Look at regulation 722.531.3.101 
 Also Regulation 314.1 is all about selectivity and Poor discrimination this is the only regulation I think that applies to your question. 
 If the downstream device and upstream are both rated at 30ma then in my opinion can cause an issue. 
 If there is AC leakage in the type A or AC then one or the other or both can trip. Either by Fault of Nuisance tripping. 
 if the Unit is supplied by SWA and the Zs is within permitted Values for an MCB device then RCD protection is not needed on that circuit but the Devices inside the Charger will have to be a Type A RCD and a RDC-DD and will have to disconnect all live conductors and disconnect power from the outlet. 
 All of the above is just my opinion and interpretation 
 What does everyone else think ? 
 Yassir

Yassir Khalil · Answer

If it a high integrity DB then insert a MCB next to the main switch if possible, The customer could request that I guess

Regulation stating a type AC RCD can not be upstream from a type A RCD

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