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!

 

[Leesparkykent]

It happens every night at the same time without fail?

 

[PEG]

I think the time has arrived,to know more about your installation,as not knowing if the equipment fitted is working correctly or not,could hamper estimating any fault.
Dependant on the origin,it could even be a neighbours fault...

 

[Jacek Buczak]

Hi all yes long time ago I had the same problem ,customer said the electricity out how combi boiler start in nite time.After watching I found fault so combi boiler was installed in garage high on the wall fell out of the outflow plastic pipe and water go after wall straight to socket outlet under boiler,after how I open socket outlet half water was inside .Best Regards

 

[Octopus]

Dare I ask if anyone had actually done any proper tests on your house? Who changed the RCD's? What is the background earth leakage that the house has?

Many questions.....

 

[davesparks]

Hi all yes long time ago I had the same problem ,customer said the electricity out how combi boiler start in nite time.After watching I found fault so combi boiler was installed in garage high on the wall fell out of the outflow plastic pipe and water go after wall straight to socket outlet under boiler,after how I open socket outlet half water was inside .Best Regards

Well that makes absolutely no sense at all, any chance of translating in to English?

 

[davesparks]

I'm curious as to what logical thought process lead to the RCD being replaced?
The fault occurs at exactly the same time every day, so unless your RCD has an in-built real time clock then I can't see how anyone thought it could be causing this issue?

The biggest clue here is that the fault occurs at a specific time,

 

[Jacek Buczak]

Very sorry for writing so incoherently, I see that the others only when reading apparently did not have so much knowledge as some have here I should not have to lend - once again sorry.Bye

 

[buzzlightyear]

had call out to customer on day the boys in blue British gas fitted a brand new Worcester bosh boiler
they fitted 2 new pc boards could not find why the boiler was not working they rang
Worcester bosh the engineer he came, told her their is nothing wrong with the boiler he told the customer, and disconnect from fuse spur.
get you own spark in ,I found the boy is in blue put in a power shower and the boiler on the same s/f spur on 3amp fuse

 

[dmxtothemax]

Could also be a neutral problem with an adjacent property,
causing currents to flow via the common earth into your system.

try what was suggested in post number 2.

 

[Lucien Nunes]

For the RCD to trip there usually has to be a fault on one of the circuits that it controls, however the trigger factor that governs when it trips might be on the other RCD or even outside your installation.. E.g., if you have a neutral-earth fault downstream of the RCD, the higher the neutral-earth voltage at your supply terminal the more likely the RCD is to trip. If there is a heavy load surge or transient from a nearby installation that momentarily pushes up the N-E voltage, it will be your RCD that trips because you've got the N-E fault, not the RCD at the installation generating the surge.

Therefore I would not waste time looking for some mystical timed device that you don't think you own, until you get some electrical testing done to discover whether there are any latent faults and what operating conditions your RCD is working under.