RCD trips and will not reset on Boiler circuit

[JamesET]

Hi all

My problem is the CU RCD trips and will not reset on Boiler circuit.
The trip happens when the electrical plug is plugged into 240volt socket which powers the Worcester Greenstar 12ri condensing gas boiler, circulating pump and two motorised zone valves for central heating. The RCD immediately trips if sockets circuit MCB is switched on. Trip occurred first time for no apparent reason one afternoon and would not reset.

I have switched boiler itself off and both CH & HW sliders turned off on programmer.

I have checked for loose or damaged wires in connection box behind programmer, and the circulating pump and cable. The cable connections to the boiler look ok. Nothing obvious on motorised zone valves regards leaks or shorts. I have not touched the boiler itself as it is beyond my level of competence! Boiler is 20 months old so still within warranty and pump is similar age.

I have checked sockets with socket tester and all looked ok.

Not sure if this a red herring but boiler would not switch off previous night but reset after switching off and back on manually. It was ok next day until tripping occurred!

Waiting for installation engineer to ring me back but in the mean time has anyone experienced similar problem?

Sorry if my explanation is not clear enough!

Thanks
James

 

[PrenticeBoyofDerry]

Have you tried to plug anything else in to this circuit at this outlet?
Do you have another circuit that is protected by a a second RCD?
If so try using an extension lead to the boiler from the second RCD protected circuit and see what happens.
If you plug in to existing boiler circuit with a toaster or kettle on load and it does not trip, it's likely the bolier.
So try boiler on second RCD circuit if that then trips, you know it's the boiler, if still under warranty get the service engineer out!

 

[JamesET]

Have you tried to plug anything else in to this circuit at this outlet?
Do you have another circuit that is protected by a a second RCD?
If so try using an extension lead to the boiler from the second RCD protected circuit and see what happens.
If you plug in to existing boiler circuit with a toaster or kettle on load and it does not trip, it's likely the bolier.
So try boiler on second RCD circuit if that then trips, you know it's the boiler, if still under warranty get the service engineer out!

Phone and broadband router work on same outlet with no tripping if boiler system not plugged in.
Tried plugging in via extension cable to upstairs outlet but same rccd tripped. Was hoping upstairs sockets were on second rccd but it was not. Not sure what right hand rccd runs but should be able to find out by switching it off.
Cannot get boiler circuit powered up as rccd trips too quickly.
I do not want to call out Bosch service engineer for warranty claim just yet in case fault is not the boiler itself. I would incurr costs if something other than boiler causing fault! Catch twenty two isn't it? Guy who originally installed boiler and pump not called back yet.

 

[PrenticeBoyofDerry]

Well it's not the circuit, so the problem lies somewhere from the plug of the boiler.
You need to eliminate things, can you disconnect the program control, circulating pump and the two motorised zone valves, separately?

Have you inspected the plug, cable, has there been any leaks?

 

[JamesET]

Well it's not the circuit, so the problem lies somewhere from the plug of the boiler.
So you need to eliminate things, can you disconnect the program control, circulating pump and the two motorised zone valves, separately?

That thought had occurred to me but ran out of time and enthusiasm today. I was going to disconnect wires in connector block behind program control for boiler then pump then valves. They all take their power from the same 240 volt plug. My head was starting to spin on my shoulders due to the number of potential scenarios!

 

[JamesET]

Well it's not the circuit, so the problem lies somewhere from the plug of the boiler.
You need to eliminate things, can you disconnect the program control, circulating pump and the two motorised zone valves, separately?

Have you inspected the plug, cable, has there been any leaks?

Yes, Yes, and No

 

[PrenticeBoyofDerry]

If you can disconnect and reconnect theses parts of the heating system/boiler/controls. Do that and see if the trips stop when something is off the circuit.

 

[JamesET]

If you can disconnect and reconnect theses parts of the heating system/boiler/controls. Do that and see if the trips stop when something is off the circuit.

Thanks for support! I will have another go tomorrow!

 

[PrenticeBoyofDerry]

No problems!
Does look like you have an earth leakage fault with either the boiler or components of the heating system.

 

[Agile]

The 12Ri is a heat only boiler.

The pump is seperate but powered from the boiler.

You may be able to disconnect the pump and then try the system.

The odd reaction the day before the problem does rather make me wonder it if might be the boiler.

Tony

 

[JamesET]

The 12Ri is a heat only boiler.

The pump is seperate but powered from the boiler.

You may be able to disconnect the pump and then try the system.

The odd reaction the day before the problem does rather make me wonder it if might be the boiler.

Tony

I am going to try this today but I agree with you about the odd behaviour of the boiler Tony
I will keep this thread updated with progress and the final solution.

James

 

[Agile]

If it turns out to be the boiler PCB causing the fault I wonder if you could retain the old one and post it to me so that I can identify exactly what component has failed?

Tony

 

[JamesET]

If it turns out to be the boiler PCB causing the fault I wonder if you could retain the old one and post it to me so that I can identify exactly what component has failed?

Tony

Good news Tony I fixed the fault!

I found the older motorized zone valve of the two WAS leaking today!! The electrics were now lying in a puddle of water where it had started to leak badly! It was not apparent it was leaking on Saturday! I guess me operating it manually a few times when fitting a new motor in case it was faulty made it leak worse ( Sods law )


For info in case it could help others roll back to this morning before above fault was found!!

I plugged extension lead into socket protected by second RCD to prove the other was not too sensitive and it still tripped.
So not faulty RCD
I isolated the pump next (still tripped)
Next I isolated the boiler (still tripped)
Thought I would do the older zone valve next (Bingo!)
With leaking zone valve isolated (Not Tripping)

I am now in the process of fitting a new zone valve ... I changed the other one a couple of years ago. Not bad they both lasted about 30 years!!!! The valve is so old the pipe unions could not be undone as they were solid so I had to cut copper pipe above and below valve to remove it!

Tomorrows job:
Reconnect all wiring
Tighten new pipe work on zone valve
Refill system, bleed radiators and pump
Fire up and enjoy a warm house again!

Thanks to all that contributed on the forum ... really glad I joined!!

James

 

[PrenticeBoyofDerry]

has there been any leaks?

 

[JamesET]

has there been any leaks?

None apart from the latest puddle!