Rcd Tripped, Then After A While Stayed On

[Ash]

I had a call from a regular client who has one of the dodgiest electrical installs I've ever dealt with.

She had the RCD controlling two socket circuits and the cooker trip during the night while they were asleep, the RCD wouldn't reset in the morning, she left it a while then tried again and it stayed on.

I went over about 24 hours later, and everything appeared normal.

The RCD wasn't too sensitive, IR readings were pretty bad as normal, but not bad enough. There was 9.73 mA of leakage on the one of two CCUs.

I PAT tested the only appliances that would probably trip it over the night, all fine.

It's thrown me.

The house is a disaster anyway, but how can the earth fault just disappear?

Has anyone had any experiences with something like this?

 

[SLIPSHOD & SLAPDASH]

I doubt you will find out, never trust what the customer says about what they have or may not have plugged in & when they did or didn't. Its impossible to find  a 'fault'   that was actually a piece of equipment now back on the shelf.

 

[NozSpark]

Ash... 9.73mA is a hek of a lot if leakage and really should have been investigated a lot further.... they definately have a, or multiple, IR faults which need rectifying or isolating

 

[batty]

Rain may be involved? 

 

[Andy™]

or a lot of computers

 

[OnOff]

You often see when  "meggering" that it can actually "dry" something out and burn off dampness thus raising the IR. Showed a lad with me not long ago - a damp motor that hadn't been used for ages. I held the IR tester on it and we watched the IR creep up. It was on the back of showing him some simple motor checks.

 

[Evans Electric]

Also dampness somewhere,  heating comes on and fault disappears . 

Also , I've mentioned this fault a few times on here , but worth reiterating .       We did rewire + new  Starbreaker board , constant callbacks , RCD tripped , went back , tested the device for 1/2 trip etc, OK , checked everything  and we were  becoming  obsessed with the heating boiler wiring but getting nowhere.   It never did it while we were there .   

So my mate is meggering the bejeebers out of everything again , I'm at the board glaring at the offending RCD , I call it some unprintable names and tap the board with the handle of a screwdriver............RCD trips !  ....reset ..tap it . trip ...  reset ........ the lady comes in the front door , slams it shut... RCD trips !!!  

New RCD  never been back .  Cost ....2 Sparks @ 5 hours ea . Incd Travel . 

 

[Andy™]

could be a faulty RCD. had an unusual one a while back. IR all good. RCD passed 1/2, 1x, 5x & ramp, but still tripping when something switched on, even class II appliances. tried to do an earth loop and it tripped. disconect out L&N from RCD and test from there, but tripped on earth loop again. swapped RCD, all working fine after that.

im guessing a shorted coil inside, so when it had any load it picked up imbalance and tripped

 

[batty]

Always more difficult to find faults on dual RCD boards. Did a rewire a while back two circuits in airing cupboard Immersion central heating towel rails underfloor heating. Split between two circuits. Now this was on RCBO board. But was randomly tripping. Insulation fine but a time we had not rewired central heating. Ended up rewireing as wiring was in a state earth wires used as lives ETC. But occasionally it was still tripping out. Ended up changing head of valve worked fine again for a while. Called back again after a few months seemed to be something to do with boiler. Anyway as customer had service contract with BG told them to get them in to sort it. Turns out it was something on boiler been fine now but as said insulation was fine but certainly something wrong to trip RCBO out.

 

[ProDave]

Or everything is fine until someone walks on a particular floor board that pinches a trapped cable etc etc.

With 9.73mA of leakage I would say everything is NOT fine. There's clearly an insulation problem and the leakage from that will vary perhaps with temperature, movement, moisture etc.  So I'm not in the least but surprised it trips from time to time. 

 

[Marvo]

I'd also say 9.73mA is high enough to warrant investigation with a view to remedial action especially if it was measured on the cpc or supply earth, parallel paths could account for more leakage.

 

[batty]

Cooker also could be problem have had them randomly tripping RCD's in past get her to leave switch off and see if it still trips.

 

[ProDave]

I had a cooker tripping and opening the back I found a dead mouse slumped over the terminals.

 

[Marvo]

In winter we get a similar problem with snakes but the IR value improves usually as the carcass dries out.

Ash, how exactly did you measure your 9.73 mA of leakage? 

 

[kerching]

I had a cooker tripping and opening the back I found a dead mouse slumped over the terminals.

We have a similar problem when the wife is cooking......

 

[NozSpark]

Slugs also leave a nice mess in JBs O)

 

[batty]

I had a cooker tripping and opening the back I found a dead mouse slumped over the terminals.

Possibly had a nip of the cooking wine hence slumped.

 

[OnOff]

Didn't we have a slug on a washing machine pcb thread on here a while back c/w pictures?

 

[pewter]

http://www.youtube.com/watch?v=8KZu0ECeMNk

 

[binky]

used with Badgers xmas lights as bait, could be great way of getting rid of carol singers... :innocent