EV Charging - Suitable in-charger live conductor isolation during PEN fault

Question

722.411.4.1 (iii) requires a device to provide isolation of all live conductors. An external device should be selected from Table 537.4, which includes contactors if the contactor is marked with the isolation symbol (I have been unable to find a contactor with this marking, so far). 
 An equivalent means of functionallity can be included within the charging equipment. This is usually a contactor. Does this contactor need to compy with Table 537.4, or is it sufficient to select a contactor that: meets the overvoltage category; has at least 3mm of contact separation and has been tested to BS EN 60947-4-1?

gkenyon · Accepted Answer

McLeod said: 722.411.4.1 (iii) requires a device to provide isolation of all live conductors 
 and, most importantly, the protective conductor ...

AJJewsbury · Answer

722.411.4.1 (iii) requires a device to provide isolation of all live conductors 
 
 Not just live conductors, but the PE too! 
 
 An equivalent means of functionallity can be included within the charging equipment. This is usually a contactor. Does this contactor need to compy with Table 537.4, or is it sufficient to select a contactor that: meets the overvoltage category; has at least 3mm of contact separation and has been tested to BS EN 60947-4-1? 
 
 Tricky. In normal circumstances it would be a simple case of the equipment standard overriding BS 7671 and often equipment standards take slightly different approaches, which could allow that sort of thing. At the moment there is no standard for open-PEN devices (although there is one for EVSE in general), so it's a bit up in the air. Current advise seems to be to adhere to general safety legislation plus some 'declaration of conformity' from a suitable 3rd party - so it's all a bit slopey shoulders onto a testing house. I guess the general principle is that if you want to do something differently from what BS 7671 suggests, you need to be able to show that it's no less safe in all reasonable circumstances. 
 
 marked with the isolation symbol (I have been unable to find a contactor with this marking, so far). 
 
 Just thinking aloud (i.e. I've not thought this through properly yet) - does it have to be a contactor? Could you use something else like an 3P MCB (which typically are rated for isolation) and a shunt trip? Obviously you'd want it to fail safe (i.e. be open under an open PEN event even if the L-N voltage was too low to drive the electronics) so maybe you'd want more of a 'shunt close' rather than shunt trip, if such a thing exists. Just wondering... 
 - Andy.

EV Charging - Suitable in-charger live conductor isolation during PEN fault

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