Random RCD tripping

[a]

I changed our old fuse box for a split load CU a few months back. We were having a problem with the RCD tripping which I put down to a faulty iron - replacing the iron seemed to cure the problem. However in the last week or so we have had 3 trips at random times, both while the house was occupied and unoccupied. Anyone have any tips on tracking down the problem?

The RCD currently covers 3 ring mains - upstairs/downstairs/kitchen - I guess one option is to transfer a couple of rings to the unprotected side and see if the trips carry on, and if so keep swapping them until they stop, which would isolate the problem circuit but still not the precise problem.

cheers

Dave.

[BigWallop]

Remove all appliances from each circuit in turn and leave them to see if they still cause a trip off. If the circuits still cause a random trip off with nothing connected to them, then kill each circuit in turn and remove the connections from the CU. Test them individually with a meger to see if any show a slight short somewhere. Test from red to black, red to green/yellow and black to green/yellow to make sure they are all intact.

If the circuits are, or have been, attacked by rodents, then any damage on the chewed or scratched insulation may only be noticeable if one particular part of a circuit is used or heats up slightly. So you may have a cable somewhere with a small hole through the outer and inner insulation which arcs over to earth at random. A spark through with a meger should show this up for you.

Don't have anything plugged in or on any spur units when you meger the circuits. Make sure they are totally disconnected from the CU, including the earth bonding, before you meger them as well.

[The Natural Philosopher]

I had this recently as well. I unpolugged tow mains extesnions that were on teh outside sockets i teh rain and it stopped..

An earth neutral short, or bad earth neutral leak can cause unpredictable tripping as loads come on and off.

If you have teh patience, switch everything off n te CU, and disconnecrt reahs one by ne and se if any show continuity to tehneutral busbar.

[Andy Burns]

Plesea slwo dwon yuor tpying, ro yuo'll wera yuore fignres uot ;-)

[BigWallop]

U cood also dinelod easy spell or simethung too cheek the pist bee4 signeding it. It shood wurk on mist noos reedors.

[BigWallop]

I always think of the English under cover cop in Allo' Allo' when I read TNP's posts.

[Ian White]

Let's add up all the neuroelectricity he's making us burn to decode this stuff, and send him the bill.

[N. Thornton]

In message 41c76c16$0$19154$ [e-mail] From: a ( [e-mail]) Subject: Random RCD tripping

occupied

This is the price tag for installing one RCD on all your rings. Next time you'll know better. The best approach is to put RCBOs on the rings, and change the RCD isolator switch for a switch only. Whichever ring trips, ensure the freezer isnt on it.

Now with 3 trips it is relatively easy to locate the dud appliance(s) with no further cost, simply by moving them between rings. Divide and conquer, move half at a time to narrow things down quickest.

Alternatively, insulation test or pat test all appliances, including the fixed ones. Of course it'll cost you.

NT

[The Natural Philosopher]

duntahvethetime neck biggeredfrom chaisaw. Eye buggered from dogwlkintodarktree.

Takeit or leeveit.

[Owain]

"The Natural Philosopher" wrote | neck biggeredfrom chaisaw.

| Eye buggered from dogwlkintodarktree.

Dogwlking can be hazardous ...

Owain

[Ian Middleton]

Friend had a similar funny like this, eventually traced to fridge, being the only appliance left on ring after unplugging everything else. RCD tripping was caused by defrosted water that normally collects in a container above the compresser (for the heat to evaporate) leaking through a crack in the container (damage during removal probably) running along a pipe and dripping on the electrics. Cured by liberal application of bathroom silicone around the crack and many many years later getting a new fridge.

I also had a kettle that would do this as well, trip the kitchen ring in the night. Then one day kettle went bang, blew mains lead out in a shower of sparks tripping the circuit for the last time in its life.

[a]

There had to be a good reason for spending the extra on RCBOs - doh! The fridge/freezer is not on the RCD side fortunately ;o)

The problem being the trips are random, and might not happen for several days. It isnt easy to move stuff around and leave them there for days on end! At the time of tripping these are the likely things plugged in (but not necessarily in use, probably on standby if available)...

Upstairs

-------- hi-fi Phone Charger tv multi skt extension -> video/dvd/pc/lcd monitor/printer/camera charger alarm clock lamp

Down

[N. Thornton]

In message 41c81902$0$19159$ [e-mail] From: a ( [e-mail]) Subject: Re: Random RCD tripping

insulated apps

well, the earthed ones are far more likely culprits, thought its not quite a 100% thing. Nearly though. Prime suspects are always things with water heating elemtns in: washing machine, dishwasher, kettle, oven as well, and the biggest cause of all is immersion heater.

including

Why not test everything with a multimeter first? No guarantee it'll pick out the duff appliance(s), but it usually will, and its cheap and easy. Check resistance on max R range between earth and (L&N connected together). Suspect the item(s) with the lowest insulation resistance reading.

Note: make sure the switch on the appliance is on, and item set to boil, otherwise you'll only be testing a part of the appliance. Obviously I dont maen it should be plugged in during test :)

NT

[a]

Well the immersion heater was removed a few months ago so thats not the problem (very scary when I looked at the connections on the element btw - how it had never burst into flames I'll never know!)

Worth a try I guess - wasnt sure how well a multimeter would work on this without sending high voltages around, but I'll get the Fluke out and see if anything turns up.

cheers.

[The Natural Philosopher]

If you have a E/N short a meter will show it up allright.

What it doesn;t show is insulatin faults that ac=rc only when HV applied.

Try it.

[Rick Hughes]

All agreed with ... remember to disconnect Neutral as well as live otherwise you may waste hours & hours. A fault took me hours of fun ... only tracked it down when I disconnected Neutrals as well .... It was some months before the fault first started and several weeks before it was frequent enough track down ... got to the point that as soon as I loaded any circuit with a high load it would trip ... eventually if I put toaster & kettle on at same time it would happen ... which for some hours had me trying to trace a non-existent problem in kitchen ring. Fault was on upstairs ring ..eventually traced to a 1gang socket ... when SWMBO had undone the screws pulled it away form the wall when painting one the fixing screw had crushed the neutral when she replaced it. The Neutral cable had a burn mark where the core was stripped by screw and was arcing. Interestingly if I had not had a trip on this cct .... it would not have detected the fault.

Rick