boiler tripping out rcd

[huwy123]

hi there,

I have this problem where my worcester boiler (42cdi) when plugged in to a circuit causes the rcd to trip. I have tested it on a couple of sockets on the same circuit that are in different rooms (i.e. so its not just a problem with 1 socket). There are plenty of other devices on this circuit that work just fine.

However if you connect the boiler to a socket on a different circuit - its fine.

The problem just seems to be just the boiler on this circuit.

A proper spark was looking at this earlier but was stumped. He's coming back tomorrow but I thought I'd see if I can get some pointers for him.

Can anyone help?

-Huw

 

[PrenticeBoyofDerry]

What other equipment is on this circuit, it maybe a build up of earth leakage from other appliance as well as boiler that is tipping it over the 30mA (generally around 26mA) parameter.
If the boiler is working on other RCD protected sockets on a different split.

 

[huwy123]

thanks for coming back.

There's loads of stuff on the other circuit - router, clock, phone chargers - nothing major really.

I think I'll go around the house and switch all of the other equipment off to see if that makes a difference.

 

[PrenticeBoyofDerry]

All electrical appliance have an amount of earth leakage, they are not large amounts but have an uneven load split across RCCBs could accumulate enough to trip the device. Especially if the boiler works okay on a least demanding split.

That does not rule of a fault with the boiler though!
Age of boiler? May suggest the pump is causing excessive leakage !

It is good idea, doing as you suggest, taking everything off load, that means unplug everything, not just switching off at plug!

 

[huwy123]

Thanks again for your help

ok went around the house and unplugged everything on that circuit. I was quite hopeful but sadly it still tripped as soon as I plugged in the boiler.


If the boiler was faulty shouldn't it trip on the other circuit? This doesn't make sense! The boiler is about 3 years old

 

[SteveP86]

Thanks again for your help

ok went around the house and unplugged everything on that circuit. I was quite hopeful but sadly it still tripped as soon as I plugged in the boiler.


If the boiler was faulty shouldn't it trip on the other circuit? This doesn't make sense! The boiler is about 3 years old

Even though you may have two 30ma RCD's, one may trip lower than the other eg one could trip at say mid 20ma and the other may be lower say 15ma even though it's labelled as 30ma hence why it works on one but not the other

 

[PrenticeBoyofDerry]

When you say other circuit are we talking about a different socket circuit on the same RCD or a socket circuit on a different RCD?
Or possible a socket circuit not protected by RCD?

 

[huwy123]

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 - I'll have to ask the sparky tomorrow. If its not it goes someway to explaining it.

Do you think the next step is to test the boiler somehow?

 

[PrenticeBoyofDerry]

It sound like a boiler issue, if you can have power without boiler connected.
If boiler trips straight away, thing to look for first would be water ingress, then components. Circulating pump and motorised valves would head the first look at list.
But would not harm having quick look at plug connections!

 

[huwy123]

ok thanks for the advice.

I've think I've hit the limit of troubleshooting tonight. I'll chat to the sparky tomorrow and may post back

Ta again.

 

[PrenticeBoyofDerry]

If your sparks, manages to suss it out, it would be appreciated if you could post back with diagnostics.

 

[huwy123]

Still not sorted.

Sparky found leakage between neutral and earth when doing a resistance test.

The next thing he suggested was to remove all wall sockets to trace the circuit around the house.

Once he finds the leakage he suggested splitting the circuit into two.

He's not coming back until tuesday. Will update then.

Ta,
H

 

[PrenticeBoyofDerry]

So your sparks found earth leakage, with appliance plugged in.
Well I expect they would, as all appliances will leak to earth!
You have already said you have unplugged all appliances and the circuit only trips when boiler is connected, you did try only having the boiler connected and still trips?
The issue is 99% related to the boiler!
Ask the Sparks to do a ramp test on the RCDs to find what they are tripping at just in case they are more sensitive expected and one is more sensitive than the other (that is if you have dual RCDS, splitting socket circuits).

Did the sparks investigate the boiler at all?

 

[huwy123]

nothing was connected when he found the leakage.

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.

very strange

 

[EFLImpudence]

Have you tried plugging something else into the boiler socket?