Hm! 32 A is enough for a house!

If the motor home has a 32 A plug, how will they hook up at the average camp site?

The motor home could, of course, be an EV.

Sorry, I am not answering your question, but I think treat as an EV.

That's basically my thoughts as well.

I have more or less made my mind up that I am going to just say I believe it is likely to be used to charge an EV at some point and therefore it needs open pen detection. 

Of you could believe that it is for a container or a caravan, and should be TT..

32A is quite a lot for a caravan, but not unknown to have the option on a big one.

Its why leads like this exist.

https://motorcables.co.uk/32-Amp-Hookup-Cable

https://motorcables.co.uk/32A-Plug-to-16A-Coupler

regs wise, I'm not sure where you stand for using an O-PEN detector for a load that is not an EV - its only actually  recommended for vehicles at the moment.

Mike

do I need to address open pen risks.

Perhaps not have to, at least as far as BS 7671 demands, at least for a single caravan at home. The section 708 requirement for TT'd supplies for caravans only applied to caravan parks, camping parks and similar locations - and the definition of a caravan/camping park is land that contains two or more pitches. The ESQCR prohibits the connection of a caravan to PME (9(4)), but the requirement only applies to a distributor, not a consumer. All of which probably explains why the usual way of connecting up a caravan at home is via one of these...
https://www.aandlleisure.co.uk/uk-mains-adaptor-cable-13a-to-16a-fly-lead-hook-up-caravan-generator----016118a-2987-p.asp

That's not to say that as the designer you can't decide that it might be better to take some precautions though. It's not always simple though - TT in a domestic curtilage can sometimes be challenging - finding somewhere to bang in a rod that's guaranteed to avoid underground services, be far enough away from PME'd cables (esp PILC ones) and bonded underground metalwork not to be unduely influenced, and then keeping the entire TT'd installation out of reach of PME'd ones.

Another option might be an open-PEN device .. but BS 7671 doesn't particularly recognise them for use outside of section 722 (EVSE).

   - Andy.

Alan B said:

Assuming it is for a motor home and the customer has a TNCS or TNS supply that I have to assume is or could be TNCS, do I need to address open pen risks.

Ideally, you should consider not connecting to PME. Legislation - ESQCR - prohibits connection of a caravan or boat to a distributor's PME earthing terminal. A motor home is traditionally considered a caravan. If a simultaneous contact assessment is satisfactory, it would be more appropriate to provide a TT solution if this is at all possible.

OPDDs are only recognized in BS 7671 for protecting EV charging equipment installations. It was proposed, in the Draft for Public Comment for what became BS 7671:2018+A2:2022, to consider the use of OPDDs for mobile and transportable units (Section 717) connected to PME ... this did not make it into BS 7671, so some experts may hold the view that you shouldn't consider using them for caravans and motor homes, and in any case, ESQCR applies.

BS 7671 requires socket-outlets for domestic and similar use to be shuttered ... if you take the view that you are using a switched-interlocked outlet to cover this requirement off, you should perhaps adopt the switched-disconnector option (that has the isolation symbol clearly marked on the accessory ... one example, I believe, is the Gewiss GW66015 - there are others and this is not a product recommendation).

Perhaps also nick a couple of important requirements from Section 708 (which we know are similar in Section 722 and therefore a good idea):

1. Any RCDs in the feed to the outlet should disconnect all live conductors (708.415.1)
2. The outlet has to have its own OCPD (708.533)

32 A is a huge load, and perhaps similar consideration should be given to maximum demand etc. as when installing an EV charging point ?