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Power feed externally to Static Caravan we use for storage.

Postby » Sun Oct 03, 2010 5:47 pm


I was wondering if some one could help.
We are not planning on doing this work our selves, however I am keen to understand what is needed for informational purposes and also so I can actually run the cable ready for the work to be done but ensuring the work being done is suitable.

We have a caravan we would like to supply power to, it has from what I can see a 16Amp male commando socket which goes into a consumer unit.

From our main house consumer unit to the van is between 30-50 metres. The cable will be run along a fencing panel horizontal support, so will be in ambiant temperatures.

What should I expect recommendations wise?
A seperate fused connection from our main CU?
1.5mm/2.5mm conductive area?
seperate earth van side?

Many thanks

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Simply Build It

Postby ericmark » Mon Oct 04, 2010 11:48 pm

Since you don't state what your house supply is can't really answer the question. The problem is all to do with earths and I am not in total agreement with the rules.

So forgetting about rules for moment lets look at the problem. The outer skin of a caravan is metal and this can be touched by a person standing on the ground so if the imported earth is not at earth voltage then current can run through that person. So using a supply were the earth and neutral use the same conductor can under fault conditions cause a problem.

However a problem also arises with any exterior earthed metal on a house and when parked close to the house one could touch a metal drain pipe and caravan skin at same time so having the two earths different can cause a problem.

With a caravan site there are fire rules ensuring there is a distance between caravan and buildings but at home this is not always the case.

So although with a caravan site you need a TT or TN-S supply with a house you really need a risk assessment and some common sense.

The ideal is of course same as with a boat using an isolation transformer but since there is no electrolysis problem that is going OTT.

Fitting an earth rod needs some test equipment not normally owned by DIY and so this is not a DIY job.

Caravans are about the only time where the RCD is doubled up and a 30ma at 40ms device is fitted both in supply and in caravan so even if the supply is not quite right unlikely to be a real problem. But remember a RCD does not stop you getting a shock it just reduces the chance of a shock causing irreversible damage.

With SWA cable I always try to use a core as an earth. In theory it is not required as the steel outer will carry it. But any damage to cable can result in the steel rusting away with time and unless the cable is tested then this can be missed. Although domestic premises should be tested every 10 years often they are not. In fact not even tested on change of occupier which really there is no excuse one is fully aware there are new occupiers.
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