Neutral-Earth fault?

[Wolstej]

Can anyone help us with a problem? Since the summer one of our RCDs has been tripping every night at the same time (22:52 before the clocks went back, 21:52 ever since). There are two RCDs in the switch board: the one that trips has an outside workshop, upstairs sockets, downstairs lighting and the door bell. The house was completely rewired in 2012 so everything is (or was) bang up to date. At first we suspected the RCD so both were duly changed but to no effect. We also suspected the boiler which was quite old; today we had a brand new one fitted but still the RCD tripped. A 'neutral-Earth' fault has been mentioned a couple of times but what seems really strange is the regularity of the problem, the same time every single night. We cannot think of a single thing that comes on or goes off but surely it has to be something with timing circuitry, a standard fault wouldn't be so predictable. Could something on the other RCD be causing it? But if so, why doesn't that side trip as well?

If anyone has any ideas we'd love to hear from you because we really are at ours wits' end now and do not know where to turn

 

[Pat H]

I'd be tempted to turn off all but one of the circuits a few minutes before the trip happens. By a process of elimination you should be able to isolate the circuit that is causing the trip.

 

[Wilko]

Hi - sorry to hear you've a problem. It is intriguing that it trips at the same time ea night. A few qs ... the RCD having tripped and been reset, works ok for 24hrs? And everything in the house works as you think it should (i.e. no known faults) ? Also, do you / did you have storage heaters?

 

[Leesparkykent]

There must be something that's timed to turn on or off at that time. your new boiler is it a combi or do you have a hot water cylinder?

 

[Wolstej]

Can anyone help us with a problem? Since the summer one of our RCDs has been tripping every night at the same time (22:52 before the clocks went back, 21:52 ever since). There are two RCDs in the switch board: the one that trips has an outside workshop, upstairs sockets, downstairs lighting and the door bell. The house was completely rewired in 2012 so everything is (or was) bang up to date. At first we suspected the RCD so both were duly changed but to no effect. We also suspected the boiler which was quite old; today we had a brand new one fitted but still the RCD tripped. A 'neutral-Earth' fault has been mentioned a couple of times but what seems really strange is the regularity of the problem, the same time every single night. We cannot think of a single thing that comes on or goes off but surely it has to be something with timing circuitry, a standard fault wouldn't be so predictable. Could something on the other RCD be causing it? But if so, why doesn't that side trip as well?

If anyone has any ideas we'd love to hear from you because we really are at ours wits' end now and do not know where to turn

I'd be tempted to turn off all but one of the circuits a few minutes before the trip happens. By a process of elimination you should be able to isolate the circuit that is causing the trip.

We haven't actually tried doing this at the circuit board, definitely worth a shot. Many thanks

 

[Wolstej]

Hi - sorry to hear you've a problem. It is intriguing that it trips at the same time ea night. A few qs ... the RCD having tripped and been reset, works ok for 24hrs? And everything in the house works as you think it should (i.e. no known faults) ? Also, do you / did you have storage heaters?

That's right, we reset the RCD and it's absolutely fine until the next night. There are no other faults that we know of; we have a combi boiler and radiators

 

[Wolstej]

There must be something that's timed to turn on or off at that time. your new boiler is it a combi or do you have a hot water cylinder?

Hi. It's a Worcester Bosch combi boiler. We have nothing else on a timer. Thanks

 

[Wilko]

Can you quickly check the on off time on the heating programmer ?

 

[buzzlightyear]

you will need a lot a detective work for this one, if you have not got any test gear the only way is start dropping the mcbs , before that time of fault to see which mcb has the fault .
before the rcd trips why did you have the both rcd changed .

 

[Wolstej]

Can you quickly check the on off time on the heating programmer ?

The new boiler and wireless thermostat were fitted literally today! At the moment it's on manual so we're just going to turn it on and off when we need to. We've had the log burner going tonight so the boiler's been off since 17:30. J

 

[Wilko]

Perhaps leave it off till after the witching hour and one thing eliminated
Has that time already passed?

 

[Wolstej]

you will need a lot a detective work for this one, if you have not got any test gear the only way is start dropping the mcbs , before that time of fault to see which mcb has the fault .
before the rcd trips why did you have the both rcd changed .

Thanks, we'll definitely try this but it'll take a few nights before we get a result! I agree, why DID we have the RCDs changed! It seemed worth a try at th time but you have to trust what someone suggests, at least to start with!

 

[Wolstej]

Perhaps leave it off till after the witching hour and one thing eliminated

Will do. But would you agree it must have something to do with a timer? It's just too regular to be a random fault!

 

[westward10]

They normally trip with good reason and are generally replaced when they don't.

 

[Wolstej]

They normally trip with good reason and are generally replaced when they don't.

I know, I should be grateful that they're keeping us safe but we can't go on like this forever!