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.

 

[windle poones]

I agree of course it couldn't fill if the check valve was stuck . That's why I started out by replacing it. That's when I realised the Motorised valves literally take all radiators out of the circuit. Opening the motorised valves allow the system to be re-pressurised.

 

[Riley]

That would be the first thing I’d check, did the builder in fact use a gas safe engineer or just a builder mate of his that does a bit of pipework. You should have an auto bypass in place which will link flow and return to allow heat dissipation once both valves are shut. If the pressure won’t backfill round the return then it sounds like a poor system design. Ultimately without actual sight of the install it’s tricky to diagnose but fundamentally as I’ve said unless there is a non return valve some where on the system then that’s really the only reason that you can’t top up the pressure with the valves closed

 

[Riley]

What do the valves control one for hot water one for heating??

 

[windle poones]

Originally before the addition of the motorised valves the only thermostats controlling the on off of the boiler, rads and whole central heating system was 1. the boilers own internal thermostat monitoring the water temperature in the system and 2. Each radiator barring two are fitted with TRV's. When the builders plumber modified the system he installed the two motorised valves. He said they are to create two independent heated zones, but they both only work on the radiators. 1. Disconnects the radiators in the extension the other motorised valve 2. Effectively disconnects the main house radiators for heating. Turning both the motorised valves off is now the same as capping off every radiator in the house and the extension. Can a central heating boiler run correctly if it is only heating the hot water supplied to the hot water taps?

 

[Riley]

Yes because the heat will dissipate correctly. You don’t have the heating on in summer do you but you will still have hot water

 

[Riley]

In fairness he should’ve zoned the water as well as you should have temp control over that too

 

[windle poones]

If I accept what you are saying and I bow to your superior knowledge. I don't need to call the builder back. I just need a competent Gas Safe plumber to investigate and fix the problem? Know any good and qualified trustworthy central heating engineers in the North West London area?

 

[Sharp Point]

I’m not 100%, but doesn’t the divertor on those house a check valve? If so having the zone valves installed and shut, would lock it up

 

[Riley]

But not if the hot water is unzoned it would go round the coil and back to the primary return then it could back fill

 

[Riley]

Ugh it’s a combi isn’t it. Sorry you didn’t make that clear