static caravan tripping out


Postby birmy » Thu Jun 10, 2010 11:51 am

i have a holiday home which is a static caravan which has an intermitten fault. the outside rcd trips it could be 10 times a day or it could be once a week. 4 different electrians have had a go at the problem and cannot find the fault. it is very rare the inside rcb trips.
this has been going on for 18 months and even the makers electrian cannot find the fault.
hope somebody can hmyelp
bir
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Postby ericmark » Fri Jun 11, 2010 6:07 am

With touring caravans used when working away we have had problems with the plugs and sockets but I would have hoped if electricians have attended they would have been checked.

However the 30ma RCD has to trip between 15ma (half rated value) and 30ma and it is very possible the outside trip is more sensitive then inside trip and I would ignore the fact only one trips. This is a problem with caravans and unless the electrician has a independent true sine wave supply it is near impossible to test a caravan RCD.

So you are looking at items in the caravan and there are three scenarios.
1) Single item faulty
2) A few items all leak a little and the combination causes the trip
3) An item has a neutral earth fault which will only cause a trip when the total demand exceeds a limit.
If I was the electrician I would put each item on the PAT tester or use installation tester on them all and would be looking for any item with more than 3.5ma leakage which is the limit permitted for items plugged in using 13A plug.

Likely items are those with heating elements so any item used in kitchen to cook with.
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Postby birmy » Sat Jun 12, 2010 1:39 pm

all the appliances have been tested.nothing found. a clamp was put round the cable outside and the reading was within what ever it should be. we did a routine of unpugging everthing until there was only the fridge pugged in and it tripped. we had the fridge engineer out and he tested the fridge and said there was nothing but changed the therostat anyhow.could it have anything to do with the lighting circuits or even the electric meter on the outside of the van.
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Postby ericmark » Sat Jun 12, 2010 9:56 pm

If you Google for INLINERCD there are a number at under £20 but in general 10ma RCD's are not easy to get and only by using a 10ma unit can you isolate which item is causing the trip.

However also bad connections can cause spikes and can also cause an RCD to trip. Although now the regulations stipulate flexible cable for caravan wiring many have been wired in twin and earth and this cable is not designed to flex and it can break inside the cable if flexed.

Since caravans do flex and vibrate screws can become lose and wires can break and I would expect to find a lose connection somewhere. If it is a lose connection you can test as much as you want and never find the problem it is a case of physically testing every screw and studying the van and if there is anywhere prone to movement where cables cross then renew the cable.

It could be something as simple as one item not plugged fully in.

It is not permitted to install any item with screw connections where there is no access because screws do work lose where there is vibration and that's what I would be looking for.

Please let us know what you find.
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Postby birmy » Fri Jun 18, 2010 8:19 am

i have checked all the sockets for loose wires and found none. i even bought a 13 amp socket tester and everything tested ok.
if all the plugs in the van were unplugged and it still triped out what would cause this? on the wiring diagram it showa the van wiring bonded to the pipes does this mean the van should be earthed at the van or in the sub station. i have another electrian coming on monday morning to check out the van who says if he cannot find the foult he will not charge me.

thanks birmy
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Postby ericmark » Fri Jun 18, 2010 11:43 pm

It is a caravan which flexes and poor wiring can cause a fault like you relate either due to a trapped wire or due to a intermittent break in the cable.

Now the 17th Edition wiring regulations stipulate the use of flex to wire caravans but years ago many electricians and even some manufactures used house hold cable to wire caravans.

Some makes of RCD seem better than others at tripping due to spikes. I have tested a RCD and it has passed but changing it has removed the problem. Since you have had electricians call I would hope they checked the RCD with a RCD meter but before ripping out any wiring I would replace the RCD anyway it seems from experience even when meters say they are OK one can still have problems.

Caravans are an exception to rule "531.2.9 Where, for compliance with the requirements of the regulations for fault protection or otherwise to prevent danger, two or more RCDs are in series, and where discrimination in their operation is necessary to prevent danger. the characteristics of the devices shall be such that the intended discrimination is achieved."
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Postby sparx » Wed Jun 23, 2010 5:19 pm

Hi, I do lots of work on caravan parks, many different ways of supplying vans in use.
You mention outside & inside RCD's. where is the outside one?
Some are in distribution cupboards a distance from the van rather than at a local hook-up box.
If so the internal RCD will only see leakage from inside the van but the remote one will see the same plus any leekage from the cable between them and will therefore usually trip first.
The lack of discrimination Ericmark refers to.
Most supplies are underground and could have had minor damage from an awning peg say.
One site I deal with has RCBO's in boxes giving both Earthleakage and overcurrent protection to each supply so if they trip it is impossible to tell which caused the trip, most vans only have RCD as main switch with a couple of MCB,s for each circuit protection.
The supply device is rated 16A/30mA but the vans have 6A plus 32A circuits.
Something for your leckie to look into...
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Postby birmy » Thu Jul 08, 2010 7:26 pm

hi an independant electrician was organised by the site owners after i sent them a soliciters letter. he has hardwired the van cable in the box on the outside of the van done away with the outside rcd as their is one in the distrubution cupboard and put a new box inside the van witch has seperate rcds for each circuit. he tells me he has done this in other static vans and it has cured this problem. and after a week i have had no problems with the electic tripping out. hopefully this has now cured my problem. thank you for all your suggestions.
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Postby ericmark » Sat Jul 10, 2010 6:08 am

I am glad it is cured. The new rules for caravans state they do not apply to the electrical installations of mobile homes, residential park homes and transportable units.

I guess your caravan comes under that as being static and I had not considered that route.
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