Setup Needed for Joining Static Caravan to House Mains


Postby AmberRose » Thu Oct 08, 2015 8:46 am

Hi this is my first post! Hopefully someone can help..
What armoured cable would I need for joining from the house to a static caravan? I think I was told 16mm but I've looked and there's so many to choose from! And no I will not be connecting it, just fed up of workmen ripping us off so my advice would be get knowledge before getting someone out, so not only do you know what they're talking about but also you can join in so they know you know and that might help :)
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Postby ericmark » Fri Oct 09, 2015 12:58 am

With touring it's easy, but with static they can use as much power as the house. I was told years ago there a by-laws requiring at least a 32A feed to a caravan being used all year around.

However I have never found these rules and likely an old wives tale.

Look at a house with a 12 way consumer unit likely 4 at 32A, couple at 16A and add up all and around 250A but incoming fuse still 100A as in the main that's the limit the consumer unit will take.

So for caravan we look at largest item and select power a few amps more. So if fitted with a cooker needing 32A then likely use a 40A MCB to feed it.

But if all gas and power use is low then could run on a 16A supply.

Distance from house is next point. You have a number of considerations. Volt drop, Loop impedance, and Earthing method.

So with a 40A supply looking at around 0.75 ohms for loop impedance but for 16A more like 2.35 ohms to trip the MCB within required time. Volt drop will be for 16A 0.92 ohms and 40A 0.52 ohms to stay within the 6.9 volt for lighting but the lighting may not be that sensitive this all has to be taken into account.

Because the caravan likely has a metal frame which is likely earthed it may be impossible to safely use a TN-C-S supply which means earth rods. The rules do not allow a TN-C-S with a tourer, but static caravans are often classed as mobile homes and it may be allowed.

The electric car has caused a lot of problems with earthing charged inside a garage TN-C-S is allowed, but at a public charging point it is not. When parked outside the users house it needs a risk assessment to would out what is best method.

What changes is distance from house, with a caravan site fire regulations will not allow the caravan within 15 meters of a building so using a TT supply is not a problem. But where my caravan is parked the gas and electric meters are in a box less than arms length from caravan so caravan is on same earth system as house which is TN-C-S not that I could change it if I wanted anyway.

The caravan would normally be fed with SWA cable is it simply will not move in a hurry water and sewage is also plumbed in. However on construction sites where the stay is short maybe only 2 years than flex may be used.

So much more information would be required to give a good answer. Likely 10 mm sq SWA cable three core would be used, but could be both thicker or thinner depending on many items.
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