Unvented Cylinder Range Tribune HE long term headache!

[oldbutnotdead]

£1500 to not fix the problem? Thats a bit poor.....

 

[Colin Gordon]

Yep this has been a journey. One of the problems has been a turn over of operatives due to the failure to get someone to correctly diagnose and fix the issue. Hoping the latest ones will manage but I feel it is worthwhile to ask around, so have found your advice exceptionally helpful. One of the issues is that when folks appear to a call out I get a sense that they are under time pressure and I recognise this is difficult.

 

[oldbutnotdead]

There are a few things you can try to deal with this ',boiler firing when off' sketch.
1 Is there an external frost stat fitted? Is it set to a sensible temperature? Does it 'click' when you adjust it to read above and then below ambient temp,? Does the boiler fire up when frost stat is active? (System needs to be cold for this to be valid). Does boiler stop firing when you adjust frost stat to inactive (ie move setpoint to below ambient)?
Same set of experiments with cylinder stat.

 

[Colin Gordon]

Many thanks OBND. I will run through these tests tomorrow and post an update here. Colin

 

[Colin Gordon]

Update - so I think I may have some key information. Our ensuite shower pressure has now dropped to the point we can't use it but the pressure in the main bathroom shower is excellent. Is it possible that the valve in the shower is causing a back pressure issue which is causing the PRV to pass / fail over time?

 

[Madrab]

All depends, are your shower etc taken from the balanced cold water supply? There is a balanced cold water feed from the back of the combination valve that would usually be used to feed bar showers etc, especially if the non reduced cold water pressure is significantly higher.

You need an experienced engineer in to sort this out for you. First thing is to identify which valve is passing, then understanding why that valve is passing, this issue shouldn't be that difficult to fault find TBH, you just need an engineer that knows what they are doing and step through the issue correctly.

I think the problem is that you haven't been lucky to have someone that can properly fault find.

 

[fezster]

However, having switched off the boiler at the mains, the water is still running to the tundish even without heat, suggesting it is a valve failure.

Does your cylinder have an immersion heater? Is that switched on?

If the expansion vessel has failed (or needs recharging), as the HW heats up it won't have anywhere to expand to and will activate the PRV.

 

[Colin Gordon]

You are dead right Rab. The fault finding process has been a bit poor. What tends to happen is folk arrive, look at the valve that is passing / replace and the process just starts over again. I am not sure on the answer to your question regarding cold water feed but will ask the plumber. I am hoping the new company will work it out. Failing that any good contacts / recommendations for the East Lothian area would be welcome.

 

[Colin Gordon]

Does your cylinder have an immersion heater? Is that switched on?

If the expansion vessel has failed (or needs recharging), as the HW heats up it won't have anywhere to expand to and will activate the PRV.

Hello fezster, many thanks for your comment - yes it does have an immersion heater but it is switched off. The expansion vessel has been replaced twice now in connection with this issue so the cause of the failure has not been addressed so far.

 

[Madrab]

There's the first issue ... a valve shouldn't just get replaced, it needs investigation into whether there is a problem somewhere that is causing that valve to open.

Depending on what valve it is that will be down to either over pressure or temperature. The CH PRV, if there is one, opens under over pressure in the CH system so the CH system needs looked at. The other 2 are for the unvented and need that area investigated.

This is all moot of course unless it's being investigated by someone that is qualified and really knows what they are doing with both systems.

 

[Colin Gordon]

Hi Rab, yes this is true and fairly self evident but appears not to be the norm! I am hoping we can resolve with the latest team this coming week and will update on the remedial measures as I think this is an interesting issue. if it doesn't work out I don't suppose you would be interested in taking a look at the system? We are in East Lothian and I see you are in East Renfrewshire but that might be too far away?