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.

McLeod said:

722.411.4.1 (iii) requires a device to provide isolation of all live conductors

and, most importantly, the protective conductor ...

Thanks for the response Andy.

I am looking at existing installations and most manufacturers have opted for a contactor in the EV charger to provide isolation for all live conductors and the PE. Only matt:E have gone though the process with IMO to get their contactor certified (but it is not for general sale).

I am looking at existing installations and most manufacturers have opted for a contactor in the EV charger to provide isolation for all live conductors and the PE. Only matt:E have gone though the process with IMO to get their contactor certified (but it is not for general sale).

In which case I'd suggest asking the manufacturer (I think they should maintain a suitable file of data in order to claim a CE/UKCA/UKNI mark) - and given the recent sales ban on some EVSE products from a Scandinavian manufacturer on a very similar consideration, I'd reckon that wouldn't be an unreasonable request at all.

   - Andy.

AJJewsbury said:

data in order to claim a CE/UKCA/UKNI mark) - and given the recent sales ban on some EVSE products from a Scandinavian manufacturer on a very similar consideration, I'd reckon that wouldn't be an unreasonable request at all.

Can you elaborate on that ban AJ?

Is the required device listed in Table 537.4 as a "Control and protective switching device for equipment (CPS)" and has to be suitable for on-load isolation and comply with part 6 of BS EN 60947 rather than part 4?

probably the same as we discussed here

engx.theiet.org/.../charging-box-sales-ban-in-sweden-for-non-compliance-to-eu-standards

As far as I know it is only a problem in Sweden at the moment, but it raises an interesting point -

Usually an appliance test is a test of  functional performance, not prescriptive imagine 'shall disconnect itself and fail to safe' rather than 'shall have a fuse' - you may have  a fuse or reach the same end but design it to blow up  under fault conditions, but contain all the bits - so long as it is still safe, that's OK - and indeed a lot of small cheaper electronic bits seem to work on that exact principle....

Things like circuit breaker standards are  very prescriptive ' shall have a contact gap not less than...' The two worlds seem to have collided.

Mike

Can you elaborate on that ban AJ?

Mike's hit the nail on the head!

   - Andy.