Gloworm ultracom 38 cxi releasing pressure

[Grant44]

Hi,
First time poster. We have replaced the pressure release valve, the pressure vessel and the heat exchanger and still experiencing drops on pressure overnight which require a top up to fire the boiler up. No leaks in the system as had thermal imaging survey also no drop of pressure throughout the summer months. Replacement of heat exchanger thinking was a cross over between CH and HW. Still getting drips outside from the prv, cannot fathom why the pressure could get above the point to activate release? Only other symptom is a drip from the condensing waste pipe not sure if connected. Any thoughts as the engineers are running out of ideas and gloworm technical assistance has been limited

 

[mickyg]

what about the filling loop??

 

[Grant44]

Pressure didnt budge over the summer when only hot water, would have had same issues if it was the loop I'd have thought?

 

[mickyg]

so the pressure is rising to far just when the heating is on? How big is the system ? How many radiators? I presume they checked the tube to the EV?
Not being funny but if the water is discharging from the prv then this is a very simple fault for somebody competent.

 

[Grant44]

16 radiators.
They seem pretty competent, father and son and came recommended. Oretty sure they checked everything around the EV.

 

[mickyg]

so the only expansion vessel is the one in the boiler? There should be another one fitted for a system of that size.
PRV dripping is a simple fault to diagnose. Only 4 possible causes.

 

[stevw451]

needs another vessel

 

[Grant44]

Another vessel? Already been replaced.

4 solutions? Replaced the prv twice and the prv and the heat exchanger what's left

 

[Grant44]

Sorry meant prv twice and the pressure vessel once

 

[Grant44]

Why two expansion vessels? Is the boiler not fit for purpose?

 

[mickyg]

no the vessel in the boiler is not big enough for the system, the boiler is fine. The installer should have added another vessel and the service engineer should have realised the current vessel is inadequate.

 

[Grant44]

Interesting, I've kept a hold of the previous expansion vessell when it was replaced and found not to be the issue so at least I have the spare part, many thanks for your input I was starting to think I needed a new boiler I'd changed that many parts

 

[naanbread]

isolate the heating flow and return overnight and see if there is still a pressure loss.... if not then the issue is on the system not within the appliance.
there are only limited places you can have pressure loss within the boiler and it looks like you have covered most of them.

Plus, if its only started happening since the heating is being used then its something on the heating circuit in my opinion.

Hope this helps

NB