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Tin Tent RCD electrical crackling - help?

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trailhound

Member Since: 27 Aug 2015
Location: Colchester
Posts: 697

2006 Discovery 3 TDV6 HSE Auto Bonatti Grey

Tin Tent RCD electrical crackling - help?

Caravan is plugged into domestic supply via 13a fused plug via hook-up lead. Spent 15 minutes hoovering out van then 240v van power goes inside the van. Supply from house is good and no RCD trips either in van or house.

RCD test switch in van does nothing. Flip the RCD switch in van to reset and power resumes. Use the hoover and in less than a second, off again, no RCD trips. Repeat over and over, same result. Tried with other appliances - same result.

I notice that when I turn the master RCD switch on from off I hear a sizzling noise from the RCD (battery 6ft away), lasts about a second.

RCD toast?

17th Nov 2017 10:02 pm

Hot Tub

Member Since: 15 Aug 2017
Location: Milton Keynes
Posts: 1071

2009 Discovery 3 TDV6 HSE Auto Zermatt Silver

It sounds like it shame that you are not closer have an RCD tester. As this is a safety issue probably worth getting it changed also going away then having it fail completely no power. You could check for any lose connections with the power off. The cost of a new one against what getting it tested would be not worth it.

Saying that probably worth doing my tintent whilst I think about. Anyone going to Ice Feast I can do yours as plan to take tester with me.

19th Nov 2017 8:07 am

UNG

Member Since: 20 Jun 2008
Location: Lancs
Posts: 773

Re: Tin Tent RCD electrical crackling - help?

trailhound wrote:
Caravan is plugged into domestic supply via 13a fused plug via hook-up lead. Spent 15 minutes hoovering out van then 240v van power goes inside the van. Supply from house is good and no RCD trips either in van or house.

RCD test switch in van does nothing. Flip the RCD switch in van to reset and power resumes. Use the hoover and in less than a second, off again, no RCD trips. Repeat over and over, same result. Tried with other appliances - same result.

I notice that when I turn the master RCD switch on from off I hear a sizzling noise from the RCD (battery 6ft away), lasts about a second.

RCD toast?

Struggling to follow your post are you confusing MCB's with RCD's most caravans have an RCD as the main isolator and then have a double pole miniature circuit breaker (MCB) for each 230v circuit.

From my understanding of your description of what is happening it is an MCB that is tripping. What is worrying is that the RCD test button does not trip the RCD which suggests the RCD is faulty or there is a wiring fault. A sizzling noise would suggest a loose connection that is arcing and or burning and I would recommend you get an electrician to check it out "Never keep up with the Joneses. Drag'em down to your level. It's cheaper".

19th Nov 2017 8:47 am

UNG

Member Since: 20 Jun 2008
Location: Lancs
Posts: 773

Hot Tub wrote:
It sounds like it shame that you are not closer have an RCD tester. As this is a safety issue probably worth getting it changed also going away then having it fail completely no power. You could check for any lose connections with the power off. The cost of a new one against what getting it tested would be not worth it.

Saying that probably worth doing my tintent whilst I think about. Anyone going to Ice Feast I can do yours as plan to take tester with me.

What RCD tester are you using? as all the RCD testers I've come across will usually trip all the RCD's in the circuit be it house supply and caravan or site supply pillar and caravan and not provide the test results that the RCD will trip in the required 40ms disconnection time. For testing a caravan RCD I use an isolating transformer in the caravan hook up lead so only the caravan RCD is tested "Never keep up with the Joneses. Drag'em down to your level. It's cheaper".

19th Nov 2017 9:02 am

Hot Tub

Member Since: 15 Aug 2017
Location: Milton Keynes
Posts: 1071

A Fluke MFTM gives the disconnection time. Interested to know how you'd fit isolation transformer into house wiring circuit if testing them? Used similar test meters in work testing about 100 RCD's every three months! So long circuit have descrimination design into them not had any problems. I have relevant C&G electrical qualifications for both Installation & Test Inspection

Trailhound if not confident get someone who is to check out problem in Tintent.

19th Nov 2017 10:22 am

UNG

Member Since: 20 Jun 2008
Location: Lancs
Posts: 773

When connecting a caravan to an electrical supply using the hook up lead the supply normally has an RCD at the source of circuit which when testing the caravan RCD will not give any discrimination when applying a test current and both RCD's will normally trip but the indicated trip time is only valid for one of the tripped RCD's but which one!
The NCC Approved Workshop Scheme some years ago decided all it's approved workshops had to be trained to carry out Periodic Inspection Reports (now EICR) on caravans, the problem was that the training failed to take account of any RCD within the installation the caravan was connected to. At the time I was doing some NCC AWS assessments and when RCD trip times were demonstrated / checked both the caravan and workshop RCD's tripped and it was quite clear from the stereo effect as they tripped that on some occasions the trip times were very different.
A friend of mine who has an NCC approved mobile workshop had also noted this problem and asked me how could he do the required test and cover himself without any come back hence the isolation transformer. This is in the same yellow case that you would find on a 110v site transformer except it is 1:1 230v in 230v out transformer this is plugged into the the hook up lead and the outlet lead is connected to the caravan power inlet any tests carried out then are limited to the caravan installation as they would be if you were testing the domestic installation
As you are well aware RCD trip times can vary quite a lot and following an issue I had with an RCD a few years ago I now also ramp test them to make sure they operate within the 30ma limit as they can meet the required trip times while tripping in excess of 30ma on a ramp test

Like you I also have the C&G I&T qualification as well as the installation quals and find these days the testing has to be watertight and beyond doubt to avoid an appearance in court if something unfortunate happens "Never keep up with the Joneses. Drag'em down to your level. It's cheaper".

19th Nov 2017 11:33 am

trailhound

Member Since: 27 Aug 2015
Location: Colchester
Posts: 697

SOLVED

Thanks gents I bought a 3 pin socket tester which showed all kinds of problems in different sockets. Strangest being the sockets were live when switched off

A spare hookup cable fixed it. I rewired the terminals on the old hookup cable and the problem has now gone.

Beer o'clock

19th Nov 2017 4:01 pm

UNG

Member Since: 20 Jun 2008
Location: Lancs
Posts: 773

I would have expected a caravan to have double pole switched sockets fitted as standard as it is quite common to get reverse polarity on european sites and can also happen in the UK with incorrectly wired hook up leads so DP switches mean you don't unexpected find a live appliance even though the switch is off
Even though you have cleared the faults as it is a safety device I would suggest getting the RCD tested to make sure it hasn't been damaged by the incorrect wiring "Never keep up with the Joneses. Drag'em down to your level. It's cheaper".

19th Nov 2017 5:46 pm

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