boiler tripping out rcd

[huwy123]

Yeah tried a kettle on it - it was fine

 

[EFLImpudence]

I agree with PBoD, then - boiler.

 

[huwy123]

I could contact worcester to investigate as its under warranty.

Whats confusing is the boiler works fine when plugged into another socket on a different circuit (also protected by RCD).

I'll post back after further tests on tuesday.

 

[EFLImpudence]

You could get the electrician to measure the boiler for earth leakage while working on the 'other' circuit.

 

[huwy123]

Thanks I'll suggest that to him[/quote]

 

[JohnW2]

I agree with PBoD, then - boiler.

Sounds like it but, as the OP himself has said, the confusing thing is:

what doesn't make sense is I plug the boiler into another socket (on a separate rcd connected circuit) and it doesn't trip. ... he's swapped the rcds between the 2 circuits - no change.

About the only way I could rationalise that is if the boiler is, indeed, causing a leak to earth, but not enough in itself to trip the RCD (either of the RCDs, since they've been swapped without changing anything) but that there is enough 'other leakage' in other circuits protected by the same RCD as the boiler to bring the total leak up to the RCD's (either of the RCDs') trip threshold.

Can you think of any other possible explanations?

Kind Regards, John

 

[EFLImpudence]

I agree with PBoD, then - boiler.

Sounds like it but, as the OP himself has said, the confusing thing is:

what doesn't make sense is I plug the boiler into another socket (on a separate rcd connected circuit) and it doesn't trip. ... he's swapped the rcds between the 2 circuits - no change.

About the only way I could rationalise that is if the boiler is, indeed, causing a leak to earth, but not enough in itself to trip the RCD (either of the RCDs, since they've been swapped without changing anything) but that there is enough 'other leakage' in other circuits protected by the same RCD as the boiler to bring the total leak up to the RCD's (either of the RCDs') trip threshold.

Can you think of any other possible explanations?

I've read it all again but may be confused.

Have we resolved between:

The other circuit is not on the same RCD. To be honest I don't know if the other circuit is protected by another RCD -

and

he's swapped the rcds between the 2 circuits - no change.

Plus, hasn't it been said that the boiler still trips both RCDs with nothing else connected to the original circuit?

 

[JohnW2]

I've read it all again but may be confused.

So may I be!

Have we resolved between:

The other circuit is not on the same RCD. To be honest I don't know if the other circuit is protected by another RCD -

and

he's swapped the rcds between the 2 circuits - no change.

I was initially confused/uncertain, on the basis of what the OP had told us, but the fact that we're now told that the electrician "swapped the RCDs between the two circuits" seems to suggest that the two circuits were, indeed, served by different RCDs, doesn't it?

Plus, hasn't it been said that the boiler still trips both RCDs with nothing else connected to the original circuit?

That's what I thought, but maybe the OP could confirm/clarify. I suppose that it's theoretically possible that there is a small leak (not in itself enough to trip an RCD) in the wiring of the circuit, even when no loads are connected, but enough leak from that plus (a leak in) the boiler (alone) to cause a trip?

Kind Regards, John

 

[huwy123]

hi both,

To clarify both circuits are protected by different RCDs (I just didn't know that earlier on in the thread).Suspecting a faulty RCD the sparky swapped them around. The problem remained.

The boiler will only trip out when connected to a socket on 1 of the circuits. I have tried different sockets on the same circuit - it trips. When plugged in to the other circuit its fine. I have also tried unplugging all devices on the "faulty" circuit - it still trips.

So in summary the problem only occurs with the boiler on this particular circuit. I hope this clarifies!

I personally think Johns threory about there being slight faults with the boiler and the circuit sounds correct. The electrician did say he found a leak between neutral and earth on the circuit hence he's returning to try and locate it.

Thanks again for your advice on this.

 

[EFLImpudence]

The electrician did say he found a leak between neutral and earth on the circuit hence he's returning to try and locate it.

I would think that if it were a circuit fault it would definitely result in a tripped RCD with a kettle plugged in.

 

[JohnW2]

To clarify both circuits are protected by different RCDs (I just didn't know that earlier on in the thread).Suspecting a faulty RCD the sparky swapped them around. The problem remained. ... The boiler will only trip out when connected to a socket on 1 of the circuits. I have tried different sockets on the same circuit - it trips. When plugged in to the other circuit its fine. I have also tried unplugging all devices on the "faulty" circuit - it still trips.

Thanks for clarifying - that's what I thought.

One point. You say that you have "tried unplugging all devices on the 'faulty' circuit. What you actually need to do is to unplug (or otherwise disconnect) all loads on any of the circuits protected by the same RCD. ... and don't forget that some loads may not be 'plugged in'.

I personally think Johns threory about there being slight faults with the boiler and the circuit sounds correct. The electrician did say he found a leak between neutral and earth on the circuit hence he's returning to try and locate it.

It's certainly the only credible theory that I can currently think of. The N-E leak which the electrician found - was that in the wiring of the circuit (with all loads disconnected)? If so, that is very probably the underlying problem. In that scenario, although a small leak in the boiler might be enough to be the 'last straw' which causes an RCD to trip, it might not mean that there is anything wrong with the boiler - many devices/ appliances (particularly those involving electronics and associated power supplies) result in small leaks to earth even when they are 'working normally' and not faulty.

Kind Regards, John

 

[JohnW2]

The electrician did say he found a leak between neutral and earth on the circuit hence he's returning to try and locate it.

I would think that if it were a circuit fault it would definitely result in a tripped RCD with a kettle plugged in.

It depends upon the extent (impedance) of the fault, doesn't it? You seem to be thinking of a low (maybe even negligible) impedance N-E fault - in which case, as you imply, connecting almost any significant load (not just the boiler) ought to result in a trip. However, if it were a very high impedance N-E fault (only detectable by IR testing), it might never, in itself, be enough to result in an RCD trip, even if large (but 'non-leaky') loads were connected - but the RCD could trip if another load with a small leak ('the last straw') was connected.

Does that make sense?

Kind Regards, John

 

[EFLImpudence]

The electrician did say he found a leak between neutral and earth on the circuit hence he's returning to try and locate it.

I would think that if it were a circuit fault it would definitely result in a tripped RCD with a kettle plugged in.

It depends upon the extent (impedance) of the fault, doesn't it?

Not if it is a circuit N-E fault and a non-faulty boiler trips it then, surely, a kettle would.

You seem to be thinking of a low (maybe even negligible) impedance N-E fault - in which case, as you imply, connecting almost any significant load (not just the boiler) ought to result in a trip. However, if it were a very high impedance N-E fault (only detectable by IR testing), it might never, in itself, be enough to result in an RCD trip, even if large (but 'non-leaky') loads were connected - but the RCD could trip if another load with a small leak ('the last straw') was connected.

Yes, that makes sense and may, indeed, be the solution - but that would also be the case with just accumulated leakage without a circuit fault.

Surely "a very high impedance N-E fault" that resulted in a boiler tripping the RCD could not sustain a kettle.



Have we definitely determined that the boiler trips this one circuit with nothing else plugged in to it?

 

[huwy123]

The N-E leak which the electrician found - was that in the wiring of the circuit (with all loads disconnected)?

Yes it was.

I'll post back on tuesday - hopefully with the resolution

 

[huwy123]

Have we definitely determined that the boiler trips this one circuit with nothing else plugged in to it?

Yes I have tested the boiler with everything unplugged on this circuit. It trips.