Static caravan electrical question

[Jason1790]

Hi all, hypothetical question really, I'm just curious to know the answer.

I was working on my friends static caravan at the weekend and he started telling me about how his 'fuse' trips, leaving him with no power and having to go outside, usually, or probably more noticeable to him, in the middle of the night when it's pouring down with rain . I had a quick look and it turns out that it's the 16a MCB located in a plastic enclosure outside the caravan that's tripping due to cumulative overload from the circuits inside, none of which are overloaded separately.
So that made me wonder if there was a compliant way of 'bringing this 16a supply indoors' and avoiding this outdoor MCB from tripping, allowing my friend to reset without braving the elements?
Thanks for reading
Jason

 

[PrenticeBoyofDerry]

Is this a MCB or an RCCB,RCBO,RCD that is tripping.
It may not be an overload issue but an earth leakage one.

 

[JohnW2]

So that made me wonder if there was a compliant way of 'bringing this 16a supply indoors' and avoiding this outdoor MCB from tripping, allowing my friend to reset without braving the elements?

Assuming that your explanation of the reason for the MCB trips is correct, to try to think of ways of making it easier for him to reset the MCB due to continuing overloading of it (and maybe also of cable) is not really a very satisfactory approach - that really is 'papering over cracks'!! He really ought to reduce his power usage and/or (if this is possible/permissible, and the extra current is available from the source) increase the rating of the 16A MCB (and upgrade cables if necessary), so that overloading/trips do not occur. I suspect the latter may well not be possible, so he may well be stuck with the former.

Kind Regards, John

 

[Jason1790]

Thanks for the reply John, I can almost guarantee it's an overloading issue having calculated his approximate power usage prior to the MCB operating. I can confirm it is a 16a MCB, not RCD in a small CU inside a plastic pole mounted outdoor box with a meter inside, this is connected via 4mm T+E to the RCD protected 6 way CU inside.
This problem only occurs in winter when he's trying to heat the caravan, I mentioned using less power but he insists it's necessary to keep the chill off. I don't think the site owner would allow an increase to the 16a MCB, and as the meter box is his property I suppose it's out of the question anyway.

 

[JohnW2]

Thanks for the reply John, I can almost guarantee it's an overloading issue having calculated his approximate power usage prior to the MCB operating.

Fair enough.

I can confirm it is a 16a MCB, not RCD in a small CU inside a plastic pole mounted outdoor box with a meter inside, ... I don't think the site owner would allow an increase to the 16a MCB, and as the meter box is his property I suppose it's out of the question anyway.

As I suspected, it's the site owner's MCB, in which case what you suggested (moving that MCB into the caravan) surely wouldn't be possible?

This problem only occurs in winter when he's trying to heat the caravan, I mentioned using less power but he insists it's necessary to keep the chill off.

I sympathise with him - but I can't really see what can be done, electrically, to help him. I suppose the most obvious solution would be to use something (presumably LPG) other than electricity for 'keeping the chill off' in winter!

Kind Regards, John

 

[PrenticeBoyofDerry]

The power point will belong to the site owner, you will be restricted to 16A demand and should be RCD protected!
So the only option is to decrease the demand being taken.

 

[Jason1790]

Fair enough, as I said it was a hypothetical question and the obvious answer is to use less power, it just made me ponder alternative solutions and the possibility of having some sort of 'reset' indoors. My proposal was not to physically move the site owners equipment indoors, only the 'fault', whilst maintaining something close to a 16a supply.
The CU in the meter box is a 4 way and definitely has no RCD, although the CU indoors does.

 

[JohnW2]

Fair enough, as I said it was a hypothetical question and the obvious answer is to use less power, it just made me ponder alternative solutions and the possibility of having some sort of 'reset' indoors. My proposal was not to physically move the site owners equipment indoors, only the 'fault', whilst maintaining something close to a 16a supply.

If you didn't move the site owner's MCB, I can't see how you could prevent it tripping under 'overload' other than to 'bypass' it, which would be even more naughty that moving it!

My understanding is that 16A, if not 10A, supplies are pretty universal in that sort of situation - so your friend certainly isn't alone, and I presume the usual solution is to heat during winter with some fuel other than electricity!

Kind Regards, John

 

[PrenticeBoyofDerry]

Normally you would expect cooking appliances to be gas, even the fridge could be gas powered and I would expect a combi-boiler.

So although there is a 16A restriction, it would deal with most instances for limited period of time.

 

[JohnW2]

Normally you would expect cooking appliances to be gas, even the fridge could be gas powered and I would expect a combi-boiler. So although there is a 16A restriction, it would deal with most instances for limited period of time.

Indeed. With only 16A (or 10A) available, it really makes no sense to try to cook, heat or even heat water (other than kettles, perhaps) with electricity. Indeed, my (extremely old) experience of static caravans was of ones which had no electricity at all - even the lighting was LPG!

Kind Regards, John

 

[westie101]

A static should normally be supplied from a 32A circuit anyway. The 16A is generally for touring caravans which are much smaller

 

[ericmark]

I seem to remember back in 1994 when stopping in a touring caravan being told with a residential static there was a requirement for a 32 A minimum supply.

I have not been able to find the regulation but since it was the site owner complained that he had to provide the official residential static with so much power he had problems providing the tourers with 6A each I would think it was correct.

I think something to do with being habitable there are minimum requirements although we all were living on the same site the couple of official residential statics had to be provided with water on tap, sewage connections and more power. However to be considered as residential static it also had to satisfy insulation requirements and what seemed to be the same caravan non winter insulated designed for summer use only was half the price to the fully insulated model.

I got a 10A supply and did all sorts to try and keep within the 10A. The under sink water heater supplied the thermostat for the fan heater so when the water heater wanted power the fan heater stopped.

The site owner would have happily given us extra power if he could of but site supply was split phase with 100A fuse on each phase. I installed an 80A moulded breaker so that the DNO fuse would not blow so the 80A trip would open and by the time the owner had been called out it had cooled enough to be reset.

The intention was that caravans would use gas for heating and cooking so electric power only worked lights and TV etc. But it was not metered so everyone tried to heat using the mains supply.

Caravans are not the only things to have problems with getting enough power. Narrow boats also are often supplied with 4, 6, 10, or 16 amp MCB's and running a washing machine on 4A is near impossible so they use all sorts of methods to get the extra power including special grid tie inverters which can supplement the mains.

It may be worth joining a narrow boat forum and asking about them as all I know is they exist.

 

[SimonH2]

Presumably it's a case of certain combinations of demand going over the limit - so if the kettle goes on while the heaters are on, that sort of thing.
You can get relays (forget what they're called) which will shed loads - so (eg) when you pop the kettle on, it'll temporarily turn off the heaters and then put them back on when the kettle's finished boiling.

Obviously this won't help if the total load really is too much, but assuming it's not on the limit all the time, it might help.

 

[Jason1790]

Interesting replies guys, thanks. It's definitely a 16a supply, as are all of the caravans in the vicinity (I only checked the immediate neighbours but they had 16a too and I'm led to believe it's the same throughout the site). Perhaps the reason for this is the site owners desire to get as many vans on the site as he can without upgrading the electrics? There have been instances of the main breaker operating when all of the vans are occupied and getting up to temperature.
The problem does arise from heating. Hot water and the cooker are both LPG and as I said it mainly occurs in winter which, interestingly, when I calculated his 'winter loading', albeit approximately, even with a small amount of diversity thrown in indicated that the MCB was almost constantly drawing in excess of 16a( which I know they are capable of),which would explain the overload occurring even when relatively small additional loads are applied. When I was told about the 'fuse tripping' even in these circumstances my initial thought was earth leakage but it would appear not.
As I said before I was curious to whether a solution other than the one I offered ("use less power then,dummy!") existed, even if it was a prohibitively expensive, bespoke piece of equipment that I was unaware of. My conscience is clear, having given the best advice possible, albeit whilst laughing at the thought of my friend shivering and cursing whilst resetting in the dark.

 

[bernardgreen]

One way to "solve" the problem could be to use a small storage heater ( 1 or 2 kW which would be heated when no other large loads are active.

Simon's suggestion to use automatic load shedding could be used to turn OFF the heater when the load is close to or exceeds the 16 amp limit.