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

 

[windle poones]

Yup it is a combi boiler. No water tank heating coil.

 

[Riley]

They should really have a) piped in a bypass and b) piped the filling loop to the return side as this would alleviate the filling issue slightly. To be fair when properly filling you should manually lock open the zone valves anyway using the levers on them. The filling loop isn’t really a problem as you can do the levers. The bypass is. I’m calling builder or non qualified/educated install

 

[windle poones]

I am not 100% sure on what you are suggesting, but I think you are advising that the Potterton Puma 80 boiler (Combination boiler) as installed in my system. Was probably OK before the central heating side, (Pipe and radiator side) was modified. I therefore need to call the builder back to address the issue which appears to be caused by no effective by pass fitted when the pipe work was modified?

 

[Riley]

Don’t call a builder. Builders build plumbers plumb. They have the right idea in so much as the house sounds like it should be zoned but a bypass will deal with heat once the heating requirement is satisfied

 

[Riley]

As per MIs

 

[Millsy 82]

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

The filling loop is on the flow. On that boiler the diverter valve opens when the diverter valve gets up to a certain temperature causing it to open.

I will remain with what I said before get them back as if its firing when both valves are shut it will be a simple wiring fault. Also ask them to put a bypass on it as I said in my last post.

 

[windle poones]

Thanks Riley, the only problem I now have is, the extension build is new and I have not signed off on the builder's snagging list. So a small final payment is due. I don't know whether I should trust him to put it right or to call in a known good plumber to rectify his work. 😵

 

[Riley]

Were it me I would insist on a proper plumber and tell him you’ll be knocking the difference off his bill. He may, fairly, insist on being given the chance to put it right. What has been done is 90% right in terms of building regs but it’s Your call really.
Two questions:
Who rebuilt such an old boiler?
Do you have a thermostat in each zone?

 

[Burger]

Any of the flow and return isolation valves closed under the boiler?

 

[Riley]

No I think it’s as Bogrodder said there’s a non return on the diverter

 

[windle poones]

In answer to your two questions:
1. It was rebuilt by a tech specialist from the company that now owns Potterton. I had an expensive maintenance contract with British gas. During one of their service visits their engineer bodged and damaged the boiler. I refused to accept a new Worcester Boch as a replacement. The rebuild was paid for by British gas after a long running dispute where they finally admitted liability.

2. Each zone is controlled by separately wired "Floureon heating thermostats". They are highly accurate I have tested them with an infra red sensing meter.

 

[Riley]

I’m gobsmacked they rebuilt the boiler but fine and glad you have stats

 

[Millsy 82]

I’m gobsmacked they rebuilt the boiler but fine and glad you have stats

I'm gobsmacked he refused a new boiler.

 

[windle poones]

Hi Millsy,

My reasoning was. The existing boiler was the most reliable I have ever owned. It had given me 25 years’ service at the point when it was bodged. It had always been maintained to a good standard. I have always been fan of the old saying “If it aint broke don’t fix or replace it”.

In another home I had a boiler new in 1964, by Valliant. It was still working fine when I sold the home in 2003. Both boilers were always properly maintained.

I had considered the Worcester Boch, but had heard they were only slightly more efficient and could be troublesome unless I was replacing the entire system, pipes and rads. My own research led me to believe I would be lucky to get seven years from one - WB.

 

[Riley]

I’d imagine efficiency wise you are far worse off but I do agree with your adage re if it ain’t broke. Plus I’d imagine parts will be scarce for the puma in the next few years. Did you not also say you’d had new pipework etc?

 

[windle poones]

No not new pipe work. I had the whole system cleaned by a guy specialising in power flushing, that's all he did. He forward and reverse power flushed to remove the debris that had collected in the radiators and the pipe work. All rads where individually disconnected and power flushed. This was after the whole system had been flushed through. The process took five hours from start to finish.

 

[Riley]

That really would have been the time for a new boiler and then maintained it

 

[windle poones]

In retrospect I probably should have gone for a new boiler, maybe a Valliant. I had checked spares availability for the Puma range before making my decision and was told the heat exchanger for the Puma 100 had been discontinued, but all parts were still available for the 80. However that was 2 years ago.

 

[Riley]

It’s amazing how quick things change but if your boiler is in good working order then I keep everything crossed for you that you don’t require any further repairs any time soon. Anyway keep us updated as to how you resolve the bypass issue

 

[EvilDrPorkChop]

Don't blame you for keeping it. I'm keeping my Glow Worm Ultimate going for as long as I can.

We've taken condensing boilers out which have been 6/7 years old which were beyond repairing. Admittedly these were probably ones that haven't been well maintained or fitted well.

 

[sammathias]

I'm gobsmacked he refused a new boiler.

They refused a Worcester.....that's a no brainer really.

 

[firemant]

I am surprised "well maintained" and "British Gas" cropped up in the same sentence,TBH.

And, to be pedantic, the filling loop NRV should be on the Cold mains side.

 

[Riley]

Not doubting you but why??? It always made sense to me when there are two taps but in the instance where it’s tap hose nrv it makes sense because you’d never be able to remove the hose correctly

 

[EvilDrPorkChop]

Not doubting you but why??? It always made sense to me when there are two taps but in the instance where it’s tap hose nrv it makes sense because you’d never be able to remove the hose correctly

It was my understanding that you required two taps by regs anyway?

You can see why you have the NRV on the cold, as it's less of a dead leg.

 

[Riley]

But there’s no dead leg because the hose should be removed, alright maybe mm in it but seriously.

 

[Riley]

It was my understanding that you required two taps by regs anyway?

You can see why you have the NRV on the cold, as it's less of a dead leg.

And we have all seen proper filling loops with one tap on

 

[EvilDrPorkChop]

But there’s no dead leg because the hose should be removed

Should be. But how many customers actually remove it though.

Also if you're only fitting a tap on one side and just a NRV on the other I wouldn't be removing the link.

 

[Riley]

No but I’m arguing regs if you say there should be two taps then the hose should also be removed. Sorry I’m not being pedantic I’m genuinely querying. I cannot see what difference it makes what the reasoning is for the nrv on cold

 

[EvilDrPorkChop]

No but I’m arguing regs if you say there should be two taps then the hose should also be removed. Sorry I’m not being pedantic I’m genuinely querying. I cannot see what difference it makes what the reasoning is for the nrv on cold

I wasn't disputing the fact that the hose shouldn't be removed, I was just simply stating that hardly anyone actually removes the link.

I thought there was some reg about the NRV on the filling loop, but I can't find it to hand. Years ago, it was as you say NRV on the heating side. Then about 10 years ago I thought they changed it and required the NRV to be on the cold main. Incase someone left the filling loop open on the cold side and the dead leg within the loop.

Even if it isn't a reg about it, isn't it better practice for it to be on the Cold? You remove the dead leg (If one is created by the customer), plus you can drain the boiler easily when recharging the expansion vessel or maintenance 😛.

Two taps - at least if one is passing you have a fail safe on your second tap.

 

[Riley]

Oh I totally agree with two taps don’t get me wrong but to me it’s logical to stop the heat at the return end so there is no inadvertent heating of the cold side. I cannot see where a dead leg occurs if there is no hose though.

 

[EvilDrPorkChop]

Oh I totally agree with two taps don’t get me wrong but to me it’s logical to stop the heat at the return end so there is no inadvertent heating of the cold side. I cannot see where a dead leg occurs if there is no hose though.

You're right, there isn't one when the hose has been removed. But my point kind of was, no one ever removes the hose.

 

[OffshoreGas]

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

Why do you need to be gas safe to fit a zone valve?

 

[OffshoreGas]

Thanks Riley, the only problem I now have is, the extension build is new and I have not signed off on the builder's snagging list. So a small final payment is due. I don't know whether I should trust him to put it right or to call in a known good plumber to rectify his work. 😵

Legally the original contractor is entitled to be given reasonable opportunity to put the situation right. You’re well within your rights to insist the work is undertaken by a competent person. Sounds very like you have the experience to decide for yourself if the guy is flanneling you.

 

[Riley]

Why do you need to be gas safe to fit a zone valve?

Didn’t say to fit a zone valve did I. OP alluded to the rebuild of the boiler which I was questionning

 

[Riley]

Legally the original contractor is entitled to be given reasonable opportunity to put the situation right. You’re well within your rights to insist the work is undertaken by a competent person. Sounds very like you have the experience to decide for yourself if the guy is flanneling you.

As you say however you are well within your rights also to refuse access if you feel they have acted outside scope or unlawfully

 

[OffshoreGas]

Didn’t say to fit a zone valve did I. OP alluded to the rebuild of the boiler which I was questionning

Sorry, I didn’t read it as the boiler had been rebuilt some time before the builder had worked on the system.

 

[OffshoreGas]

As you say however you are well within your rights also to refuse access if you feel they have acted outside scope or unlawfully

It’s generally not looked on favourably by the small claims court if you’ve refused to give a contractor fair chance to put right what may be an honest mistake.

Neither the pipework nor electrical work is notifiable under building regulations so not sure how you’d prove the guy wasn’t competent.

 

[Riley]

Again I was referring to whether or not the builder had acted unlawfully in terms of working on the boiler. They don’t get a second chance there

 

[OffshoreGas]

A 30s google search turned up the manual for your boiler, in section 1.6 it clearly stares the diverter valve must be open to fill the boiler. See attached image.

Doesn’t sound like your builders sub contractor has done anything wrong here.

 

[Welder]

Don't blame you for keeping it. I'm keeping my Glow Worm Ultimate going for as long as I can.

We've taken condensing boilers out which have been 6/7 years old which were beyond repairing. Admittedly these were probably ones that haven't been well maintained or fitted well.

My Ideal Mexico is of 1997 vintage 😎

On a sep note, efficiency ratings as specified by all manufacturers are ONLY seen by a VERY small number of UK home owners.
Why?
The efficiencies are calculated at a flow temp of 50 degrees C and a return of 30 degs C. However, most UK home owners would claim the system is faulty at such low flow temps so new (efficient boilers) are commissioned to run at a flow of 70 & (at best) a return of 50. This delivers just a few % of potential and rarely (if ever) pays back the investment.

 

[OffshoreGas]

My Ideal Mexico is of 1997 vintage 😎

On a sep note, efficiency ratings as specified by all manufacturers are ONLY seen by a VERY small number of UK home owners.
Why?
The efficiencies are calculated at a flow temp of 50 degrees C and a return of 30 degs C. However, most UK home owners would claim the system is faulty at such low flow temps so new (efficient boilers) are commissioned to run at a flow of 70 & (at best) a return of 50. This delivers just a few % of potential and rarely (if ever) pays back the investment.

How do you achieve that then?

Increase the resonance time/reduce flow rate through radiators?

Surprising in this day and age of smart TRVs there not measuring flow/return temp.

 

[Welder]

How do you achieve that then?

Increase the resonance time/reduce flow rate through radiators?

Surprising in this day and age of smart TRVs there not measuring flow/return temp.

Achieve what?

 

[OffshoreGas]

Achieve what?

The temperature differential across the radiator.

 

[Welder]

The temperature differential across the radiator.

Flow rate. Slower the flow rate higher the temp drop.

 

[Michael1960]

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?

The emphasis being "plumber" or heating engineer !

 

[OffshoreGas]

The emphasis being "plumber" or heating engineer !

If you read the manual it says the diverter valve needs to be be open to fill. There doesn't appear to be anything wrong with the work tats been done.

 

[Chrisjones.7976]

If the cold water feed to the filler loop is boiler side of the new valves you should be able to pressurise the system. It's unclear what's where from the pictures. It needs a sketch of the pipework with valve positions. If you turn a tap into you get hot water? Too much guesswork without a diagram.

 

[OffshoreGas]

If the cold water feed to the filler loop is boiler side of the new valves you should be able to pressurise the system. It's unclear what's where from the pictures. It needs a sketch of the pipework with valve positions. If you turn a tap into you get hot water? Too much guesswork without a diagram.

The manual for the boiler clearly says the the diverter valve needs to be open to fill.

 

[Karl Murray]

Get someone out to check it?

No point any of us guessing as by the sounds of it you shouldn’t be touching it anyway.

Regardless looking at your pictures you don’t have a bypass for when both zones are closed. Who knows if you’ve got a non return anywhere on the system.

You’ve also got a combi so hot water demand isn’t with the zone valve.

You’ll need a professional to diagnose on site it in my opinion.