Puzzled Over tripping please help

[BMW]

Hi
Wonder if someone can help. I recently called at a job and the owner mentioned the MCB on a ring trips. Now he said another sparky had looked taken sockets off etc and found nothing. Thing is he thinks it's from 1 or 2 sockets in the kitchen and claims to have seen a flash from that area. Now it happens at all times of the day sometimes even midnight. It reset no problem then can be OK for day's or weeks the pops again.

I tested the circuit which seems to feed mostly downstairs but does have some upstairs sockets on the same circuity so it's a bit of a mix and found nothing.

Since then I have changed the consumer unit (separate job) and that circuit is now on a RCBO. Again tested and all clear. All fine for a week then guess what got the call it had happen again? Again reset straightaway and all fine. did it again the next day. Then fine for a week. Customer claims no appliances on at the time.

Spend half a day taking things apart and nothing. Customer wants it sorted but frankly I'm at a loss now. I can't find what I can't see and now customer is asking if I can rewire part of the circuit which could be a nightmare as I don't have fault to find and the house if full and lived in.

Any ideas?? It's getting where I'm testing the same thing again. Need someone to bounce some ideas off

 

[vernam616]

I take you have IR tested that circuit?

 

[timo1]

Was it an MCB tripping (not on RCD) before? If so that is more likely to be a dead short if the circuit is not overloaded. The fact that the sockets have flashed could mean a loose connection so if you havent already I would double check the sockets. I had a fault once where a tiny bit of insulation was nicked which caused the RCD to trip. These type of faults are infuriating but stick with it. Is there heating that comes on which could cause the fault? Any of the sockets subject to moisture (above a kettle, washing machine etc?)

 

[timo1]

Just thought of another one...is the fridge or freezer plugged into that circuit? maybe when the thermostat kicks in sporadically its enough to trip....

 

[GLENNSPARK]

Hi
Wonder if someone can help. I recently called at a job and the owner mentioned the MCB on a ring trips. Now he said another sparky had looked taken sockets off etc and found nothing. Thing is he thinks it's from 1 or 2 sockets in the kitchen and claims to have seen a flash from that area. Now it happens at all times of the day sometimes even midnight. It reset no problem then can be OK for day's or weeks the pops again.

I tested the circuit which seems to feed mostly downstairs but does have some upstairs sockets on the same circuity so it's a bit of a mix and found nothing.

Since then I have changed the consumer unit (separate job) and that circuit is now on a RCBO. Again tested and all clear. All fine for a week then guess what got the call it had happen again? Again reset straightaway and all fine. did it again the next day. Then fine for a week. Customer claims no appliances on at the time.

Spend half a day taking things apart and nothing. Customer wants it sorted but frankly I'm at a loss now. I can't find what I can't see and now customer is asking if I can rewire part of the circuit which could be a nightmare as I don't have fault to find and the house if full and lived in.

Any ideas?? It's getting where I'm testing the same thing again. Need someone to bounce some ideas off

so you just tested it without inspecting it first?

 

[ezzzekiel]

possible overload?

 

[topquark]

If it was originally the MCB (and now an RCBO) and the circuit IR tests out OK (so no signs of a permanent short), then look to the appliances on that circuit. As mentioned anything with a timed nature is a likely culprit. If the fridge/freezer is suspect then either PAT test it or move it onto another circuit and see if the fault moves with it.

 

[oldtimer]

If it was originally the MCB (and now an RCBO) and the circuit IR tests out OK (so no signs of a permanent short), then look to the appliances on that circuit. As mentioned anything with a timed nature is a likely culprit. If the fridge/freezer is suspect then either PAT test it or move it onto another circuit and see if the fault moves with it.

I would have thought a fridge would have tripped its own plugtop fuse ie 13 amps instead of a 32 amp breaker

 

[topquark]

That would rather depend, firstly on what other load is on the circuit and secondly on the "reponse" of the fuse, wouldn't it? An appliance may only be drawing say 12A but still be enough to take the circuit over it's limit. It's not necessarily the sole culprit.

 

[ezzzekiel]

I would have thought a fridge would have tripped its own plugtop fuse ie 13 amps instead of a 32 amp breaker

Depending on what loads are on not enough info given but if testing is showing clear then its either that or faulty appliance

 

[UNG]

I think this fault is the fridge or freezer doing it's auto defrost had this a couple of times. First time had me chasing my tail until one day it happened while I was stood next to the problem freezer when it started it's auto defrost cycle, tracked the fault to an intermittant fault on the defrost heater on the freezer.

 

[gdconns]

Hello!
I would split the ring as evenly as possible into 2 radial circuits on 20a mcbs, see which one trips next and then split the ring again ( uneven) see which trips next time til you narrow down the fault.

 

[BMW]

Thanks everyone yes I did do an inspection before testing just forgot to note it down. There is a fridge near this area however customer claims its new. I suspected an appliance but again customer claims nothing on at the times. The thermostat comments are great and something I did not think of. I do know a new boiler was recently installed which is in the roof (yes I know I'm confused by that one as well) however it's on the same circuit.

Don't currently do PAT testing but think I might get a friend who does to check the fridge and other items.

Thanks again all been great.