Motorhome or Caravan on EHU at Home

I can understand your dilemma regarding there being no regulations extant on connecting caravans or motorhomes to UK Domestic TN-CS /PME supply. This video describes earthing systems and may be of interest to those not familiar with the subject. Interestingly the potential problem with caravans plugged into house supplies is described!

Earthing Systems

Meanwhile why not zoom down to screwfix or other supplier and buy an earthing rod. Clamp the rod to any exposed chassis point using a thick cable eg starter lead. it's what we do on continental sites when our tester says 'no earth'.

chasncath - Thanks for posting link to video.

Can you get these bayonet connectors now - I still have two in my 'odds-and-sods' box? 

I think that I have one where you can refit the bulb into the connector and also a extension on the side of it. 

Excellent video which is a very good introduction to the subject. It also tells you how to find out if your house is PME (TN-CS).

You could earth your van using an earthing rod whilst it is connected to your home supply. Apart from the practicality, this may not achieve the desired result as it is difficult to get a low enough resistance to earth to produce a voltage of less than 70 volts under fault conditions. It probably helps though.

If you had a separate building, say, a shed with a metal structure there are specific regulations.  This in fact is exactly the same as connecting a caravan/motorhome and sometimes the van could actually be used as a dwelling (people live in their vans when having house renovation projects done). In this case you convert your shed/van etc. into an isolated installation with its own earth rod and the earth is NOT connected to the house. This in fact is what installers are doing for EV chargers located outside and it is sometimes referred to a TT island.

I am about to write to the Club and will publish the results.

Any information  from the club would be useful.

The risk is as, as I understand it,, in a TNC-S system should the Neutral fail in a certain way then the Earth conductors could become live. It would need the Neutral to fail between the service head and the main supply transformer - ie further back up the chain.

It has been identified that this potentially poses a small risk with Car charging points and hence the new regs. 

Is the Mains hookup earth actually connected to the van body I wonder?

I have a good friend taking his 18th edition exams this week and will ask him for an opinion. 

Mike

The van metalwork is all bonded to the van earth terminal which in turn is connected to the earth conductor in the EHU cable then to the house earth and bonding system. With the caravan or motorhome outside of the house “zone” a potential can therefore exist between the van metalwork and the general mass of earth.

Thanks hitchglitch - I assumed the chassis was bonded to the earth terminal, but the metal skin must prove a challenge to bond as its all glued together.

But it seems  we have exactly the same situation as a car charging point, but the regs insist on TT earthing for that and have ignored other "vehicles".

I have a reply along the lines of "interesting - I will ask the instructors if I can". If I get anything useful I will add it here.

As you say DIY earth rods are pretty hit and miss, and I am not sure I would trust that as being better than the potential problem with PME.

Have you posed the question to JW (who made the video) he appears very knowledgeable in this area.

Mike

I do believe that the Regulations are quite clear and the risks well known so I don't think that there is any need to seek advice on that. The fact that the Regulations don't cover plugging vans into your house doesn't really alter the potential risk.

The question that I have for the Club is whether they consider that these risks are sufficient to consider advising people by way of a technical note or other guidance.

I have had a reply indicating that the Technical Manager of the Club will respond in due course.  They should be in possession of far more information on the subject than I am able to access so it will be helpful to get a response.

I should stress, again, that the risk is quite low but I am concerned enough to exercise caution when I am plugged in at home.  I will not be washing the motorhome with the EHU connected!

Most house built in the last 20 - 30 years are on a PME system as there are technical reasons for doing this and also cost considerations. Those houses fed from overhead lines are not, nor are some older properties.

Try reading this

https://www.google.co.uk/search?source=hp&ei=SuY9XPPUN6nikgWuvpLYBQ&q=pme+system&oq=pme+&gs_l=psy-ab.1.1.0l10.13765.16451..23801...0.0..0.91.302.4......0....1..gws-wiz.....0..0i131j0i10.PcKbx2ybe08

The electrician fitting our car charger tells me that there is now a lot of extra work as he has to fit earth rods to most installations due to a minor and recent change in the Regulations. Looking at the motorhome on our driveway he agreed that  could be a far bigger problem!