RCBO tripping.

[Burnerman]

After having some substantial electrical work done on my home, I’m finding that my oil boiler randomly trips it’s designated 10mA rcbo.
Previously the house was guarded by a single 100mA rcd and this never tripped.
The boiler can run for hours before this happens but naturally enough never when I’m there.....the time clock told me it had run for 9 hours previously to tripping.
The electrical parts of the burner (igniter, control box, motor) are newish, there is only a room stat and a circulating pump - no port valves at all.
The boiler earthing is intact and according to the electrician all is well there.
How can I prevent this happening? A know nowt like me leans towards a capacitor across the mains feed but I’d be really interested to hear professional comments!
Thanks in anticipation
John

 

[CBW]

Any water ingress, no matter how small getting into electrics?

 

[EFLImpudence]

Just to be sure; is it a 10A 30mA RCBO?

 

[Burnerman]

Any water ingress, no matter how small getting into electrics?

No, I'm certain all is dry...it's an internal boiler.
Thanks!
John

 

[Burnerman]

Just to be sure; is it a 10A 30mA RCBO?

I'm not there right now as the house isn't habitable, but from memory its a 6A 10mA RCBO. Is there such a thing?
Thanks!
John

 

[EFLImpudence]

There are such things but not common.
A 10mA device could trip at 6mA; just thought it might be a bit low for the equipment.

There is probably a more usual reason for the tripping.

 

[Burnerman]

Ok, thanks again.....I’ll check when I’m next there on Thursday.
The electrician has only done the second fix so he’ll be back shortly.
John

 

[CBW]

No, I'm certain all is dry...it's an internal boiler.
Thanks!
John

Only reason I ask, I had one today (internal boiler), condensate pipe was leaking, customer said it could run for 5 mins, or up to a few hours.

 

[Burnerman]

For sure, it’s the intermittent failure that confuses me......it must turn itself off and on fifty times or more during its running hours, then all of a sudden - pop! Breaker down.
It’s certainly dry inside the boiler casing but maybe the spiders webs have just starting to conduct
Thanks for your interest Chris
John

 

[ericmark]

I see no real point in a 10 mA RBCO to a boiler, to selected sockets maybe, but boiler feed I would swap for a 30 mA.

If it had a 100 mA then seems likely on a TT system, so the earth and neutral could have quite a large voltage differential compared with a TN system, I would be testing neutral to earth for a fault.

Also if a TT system the RCBO likely needs to be two pole switching, so easy to test neutral to earth insulation resistance.

The reason for the time between trips is likely down to voltage differential earth to neutral changing through the day as a TT system.

 

[Burnerman]

Thanks eric, time for me to do some homework!
John

 

[JohnW2]

Thanks eric, time for me to do some homework!

I would say that the only homework you really need to do is to ascertain for sure what your RCBO actually is (specification-wise) - what matters in your present situation is what it IS, regardless of what else it might (maybe even 'should', in some people's eyes!) have been !

Kind Regards, John

 

[ericmark]

Schneider 10 mA RCBO £113.18 you can clearly get them, but does seem unlikely.

However if you say it is a 10 mA I have to believe what you say.

 

[flameport]

As it's an RCBO, the problem may not be earth leakage - it could be tripping on overload or due to the starting current of the motor being too high. Particularly if it's a low rating, or there are other factors such as that RCBO being situated next to others which run at high loads for long periods, or it's in a location with high ambient temperatures.

Need to establish exactly what the RCBO ratings are, and where it's located relative to others, and in what environment.

There is also the possibility of the circuit wiring being damaged somewhere or other problems with the connections.

 

[Burnerman]

I would say that the only homework you really need to do is to ascertain for sure what your RCBO actually is (specification-wise) - what matters in your present situation is what it IS, regardless of what else it might (maybe even 'should', in some people's eyes!) have been !

Kind Regards, John

The homework I'll do is to investigate eric's TT and TN systems......completely unknown to me but I understand them now!
John