Has my builder ruined my boiler?

[windle poones]

My boiler is a Potterton Puma 80. Its old but very well maintained and was working perfectly before my builder modified my central heating system.

I contracted a builder to build a small extension to my home. During the extension work the builder’s plumbing guy fitted two motorised valves. His logic was to enable independent control of the central heating temperatures in the main house independently from the extension.

The work was done in the winter and seemed to work fine apart from a few occasions when the pilot light went out for no obvious reason known to me, however pushing the piezo igniter re-lit the pilot flame and then the boiler would continue as normal. Keeping in mind, because of the cold weather either zoned heating circuit or both would be on and DHW.

Now Easter is here and with it the warm weather there is no demand for heat from either heated zone. So the motorised valves are both turned off. I noticed a boiling sound, (Kettling sound) coming from my boiler. Then the boiler shut down with the pilot light extinguished and the pump now running all the time.

On checking the boiler the pressure in the system was very nearly down to zero. I tried to re-pressure the system via the filler loop, but this was not possible, because of the motorised valves being both off had effectively isolated all the radiators in the house and extension from the boiler.

I found by turning the motorised valves on, effectively demanding hot water. I could now re-pressurise the boiler to 1.25 bar via the filler loop. Everything then worked as normally. However when I turned off both the motorised valves, the boiler kettled and shut down again with a loss of system pressure.

Any suggestions/advice would be very much appreciated.

 

[Scott_D]

Any pictures?

 

[windle poones]

Any pictures?

Hi Scott,
Thanks for your interest, what would you like pictures of?

 

[Chuck]

You seem to be saying that the boiler is operating when both zone valves are closed. If so, how is water circulating through the boiler, which is necessary to prevent it overheating?

 

[Millsy 82]

Get them back to double check the wiring maybe also chuck an automatic bypass valve in as well.

 

[windle poones]

Hi Chuck,
That's what I was worried about. However I think the boiler allows the central heating to be switched off, but in the switch settings shown in the photo's it should still be able to supply hot water.

 

[Riley]

I may be being thick but the valves won’t stop pressurisation as the water will just back fill round the return. If it was working fine then I’d question that the builder/plumber have done anything wrong. Things do break down you know and I’d say your boiler is not the newest

 

[windle poones]

Hi Riley,
Keeping in mind I am not a plumber, just a very experienced DIY'er. The boiler was completely rebuilt instead of being replaced about 2 years ago, complete with a full system, rads and pipe flush/power clean. I agree with you in part, but it still doesn't explain why the system cannot be pressurised unless the zone valves are on.

 

[Riley]

Where is the filling loop attached. There’s no logic to what you’re saying unless there is a non return valve on the system somewhere system doesn’t just fill in the flow direction

 

[Riley]

And it doesn’t matter if it’s been rebuilt things still breakdown. If the system was working and now it’s not it is unlikely to be anyone’s fault

 

[Riley]

Sorry to sound blunt but your title is immediately accusatory. If in fact it was a builder or a plumber that worked on the boiler and not a gas safe engineer then I’m afraid the fault lies with you

 

[windle poones]

My first thought yesterday was the check valve on the filler loop could be blocked. So I replace the filler loop. On removal I examined the non return valve and it was working fine. The attached photo shows the filler loop. The 15mm pipe is a spur from the mains water feed. The 22mm pipe feeds directly into the boiler's flow and return circuit.

 

[Riley]

So I maintain there is literally no reason why it shouldn’t go up as well as down to the two motorised valves

 

[Riley]

If the checkvalve was blocked on the filling loop then it wouldn’t fill full stop

 

[windle poones]

Riley I accept I may have hired a competent building contractor who may have used a non certified plumber. I don't know. Yup hands up my fault for not asking to see his credentials, but that is not clarifying the problem. I think the crux of the problem is all radiators are effectively locked out of the system, (Flow and Return) when both motorised valves are either off or not DHW.