RCD circuit tripping.

Phil4432

Hello all,

Just had the circuit for the upstairs light trip, can't see any obvious signs of a problem such as burning etc.  All appliances were off at the time; washing machine, TV etc.

Seems to working fine now, just wondering if there are any safety considerations?

New RCD and inspection done in 2015.  No other issues.

Thank you.

grumbler

Phil4432 said:

Just had the circuit for the upstairs light trip, can't see any obvious signs of a problem such as burning etc.  All appliances were off at the time; washing machine, TV etc.

Seems to working fine now, just wondering if there are any safety considerations?

So, it's the sockets, not 'light'? And a washing machine upstairs?

Safety considerations - you can only guess. Some houses don't even have RCDs. RCDs detect tiny leaks to earth from either line ('live') or neutral wires. And some are over-sensitive. Mine was tripped many times by a laptop PSU. Another, in the university, was tripped by a device that was tested many times by the electric workshop and declared safe. Ultimately, that device was  reconnected to another circuit and everything was fine.

You can try unplugging appliances one by one - the fault can be before the power switch. E.g. with an interference suppression capacitor that is normally where the cable is connected.

Veteransaver

It can be really difficult to detect especially if it's a neutral to earth fault.
Often dampness or water can be prime culprit, so either condensation or water getting in somewhere.
I'd firstly check any outside sockets for water. And check above the light fittings upstairs in the loft.
We had nuisance tripping caused by condensation above a bathroom making the ceiling above damp, and the cables to the lights were sitting above the damp ceiling.
If it's a neutral earth fault which ours was then even completely unrelated items can cause a trip, Eg turning a kettle on could cause the rcd to trip, but it was nothing to do with the kettle, it was because the small neutral leakage reached the trip threshold when the high current kettle was turned on for example.

Was it actually the RCD that tripped though? You said it was the lighting circuit upstairs, which would be on its own MCB, The RCD would cover the whole house (or half the house if you have a dual RCD).
So an RCD trip would take out at least half the house.
The mCBs are the "little switches" in the consumer unit, and only cover 1 circuit. The RCDs are the bigger (double width ones).
A blown bulb can trip an MCB, but an MCB should only trip if there is a short circuit basically (overload of current)
Alternatively you may have an rcbo consumer unit (though that's quite unlikely unless it's been changed fairly recently)
If you put a photo up of your consumer unit we would be able to tell.

Phil4432

grumbler said:

Phil4432 said:

Just had the circuit for the upstairs light trip, can't see any obvious signs of a problem such as burning etc.  All appliances were off at the time; washing machine, TV etc.

Seems to working fine now, just wondering if there are any safety considerations?

So, it's the sockets, not 'light'? And a washing machine upstairs?

Safety considerations - you can only guess. Some houses don't even have RCDs. RCDs detect tiny leaks to earth from either line ('live') or neutral wires. And some are over-sensitive. Mine was tripped many times by a laptop PSU. Another, in the university, was tripped by a device that was tested many times by the electric workshop and declared safe. Ultimately, that device was  reconnected to another circuit and everything was fine.

You can try unplugging appliances one by one - the fault can be before the power switch. E.g. with an interference suppression capacitor that is normally where the cable is connected.

I was actually out at the time, a family member told me it was just the upstairs lights that went out.  The washing machine (downstairs) had been used during the day, but was off at the time.  The oven was not on, until later.

I put the washing machine and oven on, plus all the lights for about an hour.  Checked all sockets and light switches for any signs of burning, smell.  Checked ouside socket, that's sealed.  Haven't been in loft, but will do that tomorrow.  The trip happened before rain, I did check the tiles second to last storm we had and they were fine.  Haven't checked tiles since string winds last week, but no signs of fallen tiles around house.

Due a 10 year inspection next year, might as well get it done soon.

Phil4432

Veteransaver said:

It can be really difficult to detect especially if it's a neutral to earth fault.
Often dampness or water can be prime culprit, so either condensation or water getting in somewhere.
I'd firstly check any outside sockets for water. And check above the light fittings upstairs in the loft.
We had nuisance tripping caused by condensation above a bathroom making the ceiling above damp, and the cables to the lights were sitting above the damp ceiling.
If it's a neutral earth fault which ours was then even completely unrelated items can cause a trip, Eg turning a kettle on could cause the rcd to trip, but it was nothing to do with the kettle, it was because the small neutral leakage reached the trip threshold when the high current kettle was turned on for example.

Was it actually the RCD that tripped though? You said it was the lighting circuit upstairs, which would be on its own MCB, The RCD would cover the whole house (or half the house if you have a dual RCD).
So an RCD trip would take out at least half the house.
The mCBs are the "little switches" in the consumer unit, and only cover 1 circuit. The RCDs are the bigger (double width ones).
A blown bulb can trip an MCB, but an MCB should only trip if there is a short circuit basically (overload of current)
Alternatively you may have an rcbo consumer unit (though that's quite unlikely unless it's been changed fairly recently)
If you put a photo up of your consumer unit we would be able to tell.

Thanks, please see above answer to grumbler.

It was actually an MCB that would have tripped, causing just the upstairs light to stop working.  Unfortunately, I wasn't in at the time and cannot confirm exactly.

Its basically the same unit as this...


https://www.youtube.com/watch?v=gIu7G8Wv5Zo

Rodders53

Go round and check that all upstairs lights are working still (and things like extractor fans or heated mirrors in bathrooms that will be on the lighting circuit).

It was quite common for a lamp (light bulb) to fail on switch on and take out the lights MCB, with tungsten lighting... some LEDs could also fail with an abnormal current surge that the MCB detects and does what it's meant to.

If you find one or two 'out' you may have the culprit?

Veteransaver

Phil4432 said:

Veteransaver said:

It can be really difficult to detect especially if it's a neutral to earth fault.
Often dampness or water can be prime culprit, so either condensation or water getting in somewhere.
I'd firstly check any outside sockets for water. And check above the light fittings upstairs in the loft.
We had nuisance tripping caused by condensation above a bathroom making the ceiling above damp, and the cables to the lights were sitting above the damp ceiling.
If it's a neutral earth fault which ours was then even completely unrelated items can cause a trip, Eg turning a kettle on could cause the rcd to trip, but it was nothing to do with the kettle, it was because the small neutral leakage reached the trip threshold when the high current kettle was turned on for example.

Was it actually the RCD that tripped though? You said it was the lighting circuit upstairs, which would be on its own MCB, The RCD would cover the whole house (or half the house if you have a dual RCD).
So an RCD trip would take out at least half the house.
The mCBs are the "little switches" in the consumer unit, and only cover 1 circuit. The RCDs are the bigger (double width ones).
A blown bulb can trip an MCB, but an MCB should only trip if there is a short circuit basically (overload of current)
Alternatively you may have an rcbo consumer unit (though that's quite unlikely unless it's been changed fairly recently)
If you put a photo up of your consumer unit we would be able to tell.

Thanks, please see above answer to grumbler.

It was actually an MCB that would have tripped, causing just the upstairs light to stop working.  Unfortunately, I wasn't in at the time and cannot confirm exactly.

Its basically the same unit as this...


https://www.youtube.com/watch?v=gIu7G8Wv5Zo

So I'd say most likely a blown bulb or burnt out extractor fan (though fan would be unlikely imo).
If you have low voltage bulbs could be a 12v transformer on the circuit caused it and the bulb or bulbs that run off that would likely not be working now.
An MCB trip would need a significant short circuit and if everything else is working ok I doubt there is anything serious wrong, it's possible there is a breakdown of the insulation somewhere (or a rodent chewing through a cable though if the cabling is static and not subject to movement if that was the case it would generally trip the instant you reset the mcb again.

Phil4432

It turns out that it may have actually been the RCD that tripped, and this occured when the oven was switched on, which is the same circuit as the lights.

Possibly the element needs replacing?  Will see if it trips again, if so will replace the element. 

Veteransaver

Phil4432 said:

It turns out that it may have actually been the RCD that tripped, and this occured when the oven was switched on, which is the same circuit as the lights.

Possibly the element needs replacing?  Will see if it trips again, if so will replace the element. 

I doubt the lights are on the same circuit as the oven, however they may be on the same RCD.
But yes the oven element blowing or the bulb blowing will likely trip an RCD.
Check oven light works and oven element is working. 

grumbler

Veteransaver said:

Phil4432 said:

It turns out that it may have actually been the RCD that tripped, and this occured when the oven was switched on, which is the same circuit as the lights.

Possibly the element needs replacing?  Will see if it trips again, if so will replace the element. 

I doubt the lights are on the same circuit as the oven, however they may be on the same RCD.
But yes the oven element blowing or the bulb blowing will likely trip an RCD.
Check oven light works and oven element is working. 

Incandescent lamps blowing trip MCBs, not RCD.

Phil4432

Veteransaver said:

Phil4432 said:

It turns out that it may have actually been the RCD that tripped, and this occured when the oven was switched on, which is the same circuit as the lights.

Possibly the element needs replacing?  Will see if it trips again, if so will replace the element. 

I doubt the lights are on the same circuit as the oven, however they may be on the same RCD.
But yes the oven element blowing or the bulb blowing will likely trip an RCD.
Check oven light works and oven element is working. 

Oven currently working normally, all I can do is wait and see if it happens again.  If it does, I'll post a picture of the consumer unit.

All electrics in house currently working as normal.