Glow Worm 30ci losing pressure when cold

[brewster2]

Hi everyone.

I have a Glow Worm 30ci that is going from 1 bar to 0.3 over night.

I have changed the PRV and the problem is still there. No water coming out of the PRV.

I fill the system to 1 Bar, central heating and hot water work fine. All turned off and go to bed. In the morning the pressure is back down to 0.3.

There are no CH system leaks and confirmed by shuting off the CH valves at the boiler and pressure still dropping although there are definitely no leaks from the boiler either.

My plumber says that it is the heat exchanger that needs changing but I cannot see why this is and have held off.

Could it be a failure of the expansion tank? If so and to save money, can I fit a separate expansion tank on the side of the boiler rather than take the boiler off the wall to replace the existing one?

Please help

 

[Simon F]

if the expansion vessel was bust it would be causing the pressure to rise when the heating was on, and be relieved through the prv.
the expansion vessel is not the problem unless the water was leaking from it.
if the leak happened with the boiler isolated, how would an external pressure vessel change that?

 

[rudeboytee]

sounds to me like expansion vessel needs replacing

 

[Simon F]

could be the schrader valve on the vessel not holding, easy to test with a bit of leak detection fluid.
but if so the pressure would be lost in the daytime whilst heating on an push pressure through prv

 

[Rickster123]

Has he checked the auto air vent? An obvious place to look but easily missed. Can't imagine it being the heat exchanger personally.

 

[brewster2]

turns out it was the 'reduced pressure zone valve' as part of the filler loop set.

thanks for the help though guys