Tripping RCD since testing?

[HappyHippyDad]

I have literally just had a phone call from the customer I saw today after doing an EICR and he says one of the RCD's is now tripping every half hour or so.

There were 3 CU's in total so I am back tomorrow to finish off. I didn't have time to test each circuit on the third CU but I did find poor global IR readings (L/N - E) of 0.008MΩ.

Trip time for the RCD was 43mS.

Its a TT with a Ra of 43.4.

He is currently having the property replastered (ongoing) this could be the reason for the poor IR, but I cant understand why it is tripping now when it wasn't before. He seems like an honest chap so I believe him.

I always spend the last part of the day making sure connections are tight so I'm pretty sure thats not the problem.

I'll break the circuits down tomorrow and find the culprit, but it was more the fact thats its tripping now and (most likely) wasn't before that I can understand and could do with a few opinions?

 

[Tiny Spark]

One of them could be anything things I would think.

Few ideas could be a weak mech that now wont hold after you tested it?
If the house is currently being plastered wet plaster shorting out something?

Sure some of the others will give you some other/better ideas

 

[Desrebel]

Sounds like a neutral to earth , if it's holding when you flick the rcd back on then I imagine it's tripping when a load is connected and the heat builds up . I've had it before when all is reading clear and holding and then as soon as anything is connected it trips nightmare

 

[telectrix]

afraid that without being there it's just guesswork. sod's law says it's tripping since you were there. only thing is for you to go back and trace the fault. let us know what you find.

 

[telectrix]

and never, ever, believe a customer when he says that it was all right before you touched it.lol.

 

[Octopus]

I'd retest the IR on the "suspected" circuit, repeating the test quickly to see if the IR increases - if it does it would suggest damp. All you can do then is wait for it to dry.

Plastering does mean that A LOT of moisture is "tracking" across the surfaces so good luck finding it!

 

[HappyHippyDad]

I feel a bit of a --- adding this next bit and wasn't going to but you need all the information!

I was tired and tested at 500V by accident and got about 0.04MΩ, then tested at 250V and it went lower (0.008MΩ) which didn't make sense, unless it's the putting 500V through that did it?

I'm sure it was ok after that for an hour or so though (before leaving)! The very last thing I did was test the RCD, can actually testing the RCD produce problems?

 

[Octopus]

I feel a bit of a --- adding this next bit and wasn't going to but you need all the information!

I was tired and tested at 500V by accident and got about 0.04MΩ, then tested at 250V and it went lower (0.008MΩ) which didn't make sense, unless it's the putting 500V through that did it?

I'm sure it was ok after that for an hour or so though (before leaving)! The very last thing I did was test the RCD, can actually testing the RCD produce problems?

I would doubt it unless you shoved 500V up it.

I'd ramp test the RCD again.

Sometimes, when its late you go round and round in circles, so walking away and going back tomorrow, with a clear mind, is probably the best plan

 

[HappyHippyDad]

I'd retest the IR on the "suspected" circuit, repeating the test quickly to see if the IR increases - if it does it would suggest damp. All you can do then is wait for it to dry.

Plastering does mean that A LOT of moisture is "tracking" across the surfaces so good luck finding it!

Thanks Murdoch..

Could you explain this a little please?

 

[Tiny Spark]

Testing at 500v isnot a problem as long as all electronic equipment is shorted or removed. Otherwise it will just damage the item that is not. (Blown a neon or 2 on spurs doing this )

Not sure about RCD's but like I said before it could be a weak mech, We worked on a circuit once and when we put the MCB back on it just wouldnt hold despite everything being tested ok. Changed it for a new one and it held fine.

 

[Octopus]

Thanks Murdoch..

Could you explain this a little please?

If the 500V test is repeated and the IR value increases, it suggests that the 500V is actually "drying" the moisture - hope this makes sense

 

[Paul.M]

I'd take a new RCD with me in the morning as said above.

 

[HappyHippyDad]

I would doubt it unless you shoved 500V up it.

I'd ramp test the RCD again.

Sometimes, when its late you go round and round in circles, so walking away and going back tomorrow, with a clear mind, is probably the best plan

Very true Murdoch! I realise 9 hours probably isn't very long for some sparks.. but I was a bit on the tired side.. even after a quick fix of chocolate and coffee!

Testing at 500v isnot a problem as long as all electronic equipment is shorted or removed. Otherwise it will just damage the item that is not. (Blown a neon or 2 on spurs doing this )

Not sure about RCD's but like I said before it could be a weak mech, We worked on a circuit once and when we put the MCB back on it just wouldnt hold despite everything being tested ok. Changed it for a new one and it held fine.

Thanks Tiny.. If all else fails I'll change it, but I'll get to the bottom of the low IR readings first.

 

[GMES]

Agree with Murdoch I have done the same thing many times, think of it as an expensive hair dryer

 

[Tiny Spark]

Very true Murdoch! I realise 9 hours probably isn't very long for some sparks.. but I was a bit on the tired side.. even after a quick fix of chocolate and coffee!



Thanks Tiny.. If all else fails I'll change it, but I'll get to the bottom of the low IR readings first.

Good plan bat man

 

[HappyHippyDad]

I'd take a new RCD with me in the morning as said above.

I think I will do that Paul.. I was going to change the enclosure any way (standalone) as it was in poor shape!

Christ I'm done in!!

Cheers for all the information guys, feel a bit gutted at leaving an installation with a tripping RCD!

 

[Tiny Spark]

Sure they will cope till the morning mate.
Dont take it so hard these things happen!

 

[PEG]

...And don't worry about your 500 V damaging the RCD,it will not. We know it should not be part of any 500 V test in normal procedure,but now and again,an apprentice tortures one,and it matters not...:stooge_curly:

 

[Lucien Nunes]

I did find poor global IR readings (L/N - E) of 0.008MΩ.

8kΩ is right on the cusp of 30mA if it's L-E, and bad enough to get warm with leakage current. For that reason I'm tempted to think it's a bogus reading or N-E, but either way it's low enough to dwarf any other concerns about the RCD etc until it's found.

I work on delicate precision electronics daily and often test all over the place at 500V. I have yet to damage anything at all. As I mentioned in a related thread recently, I even test things with stickers that say 'Do not use high-voltage insulation testers'. Of course the trick is knowing the circuitry inside and the specs of components used, to be sure the test won't cause damage. But I can't remember the last time I thought to myself 'Better not test that at 500' except for surge absorbers that will clamp below 500V and spoil the test.

 

[1stfix2ndfix]

Takes a seat

 

[HappyHippyDad]

Morning all..

Just an update, albeit a pretty boring one!

I didn't end up returning to the chaps house to fault find as he rang saying the tripping was getting better. Spoke to him today and he said it has stopped.

So now I will simply get the EICR written up and let him choose if he would like to get any work done.

I hope he does as I would really like to look at those IR readings again!

 

[Octopus]

Morning all..

Just an update, albeit a pretty boring one!

I didn't end up returning to the chaps house to fault find as he rang saying the tripping was getting better. Spoke to him today and he said it has stopped.

So now I will simply get the EICR written up and let him choose if he would like to get any work done.

I hope he does as I would really like to look at those IR readings again!

Which points at water/damp!

 

[telectrix]

has he got a cat or dog, pee'd up a socket?

 

[HappyHippyDad]

Which points at water/damp!

Yes.. But it was strange that it only started happening after I had been testing!

Also he said that the plasterer had hit a cable with their bolster (perhaps 2 days prior to my arrival) and this had tripped the RCD, that cable has now been plastered over, so that may be the culprit. When I return to do the other work needed I shall let you know! :smiley2:

 

[telectrix]

that sounds a probable. damaged cable, wet plaster, now dried out and the plaster acting as an insulator. i'd want to start digging. it may be a potential hazard. "live" walls

 

[HappyHippyDad]

that sounds a probable. damaged cable, wet plaster, now dried out and the plaster acting as an insulator. i'd want to start digging. it may be a potential hazard. "live" walls

The chap says he knows exactly where the plasterer went through.. I have asked him to mark it as well, just in case he forgets!

I've warned them that I may have to take off some of the plaster if the results are not satisfactory, but only after all tests have been done and all else ruled out.

 

[HappyHippyDad]

In fact I'm supposed to be writing up the report now.. I have my cup of tea to hand and the certs right in front of me... but I'm on here! :smiley2:

 

[HappyHippyDad]

Just giving an update..

RCD started tripping again so I returned to do some tests.

Broke down the circuits.. found the fault on one of the rings. Found the faulty point and it turned out to be one of the screws holding the face plate on a FCU was touching the neutral (where conductor was showing ever so slightly through the broken insulation). Whether or not it was me that did this I dont know, but I had certainly removed that point so when I replaced it I either nipped the neutral or at least repositioned it so that the faulty part was touching the screw!

Either way I couldn't justify any cost and had to own up to the possible error on my part, but the chap is getting me back for remedials so a good outcome in the end! :smiley2:

 

[Geordie Spark]

Just giving an update..

RCD started tripping again so I returned to do some tests.

Broke down the circuits.. found the fault on one of the rings. Found the faulty point and it turned out to be one of the screws holding the face plate on a FCU was touching the neutral (where conductor was showing ever so slightly through the broken insulation). Whether or not it was me that did this I dont know, but I had certainly removed that point so when I replaced it I either nipped the neutral or at least repositioned it so that the faulty part was touching the screw!

Either way I couldn't justify any cost and had to own up to the possible error on my part, but the chap is getting me back for remedials so a good outcome in the end! :smiley2:

It WAS you wot did it ... I saw you did it!!!

 

[ipf]

It WAS you wot did it ... I saw you did it!!!

And the moral is...don't put your hands up unless you're sure your kex won't fall down.