boiler pressure problems

[Harrowslayer]

I have a potterton puma 80 boiler and recently it has started to lose pressure. I can top it up from the inlet but obviously there is something wrong!! I have chacked all the rads and valves + pipework under the floor for leeks in the system and found nothing!! The boiler is currently lossing about 1bar in 24 hours. The low pressure light does not come on.

If anyone could suggest what's happening and more importantly if it can be fixed by myself that would be great.

 

[jackthom]

Does the system pressure rise much when the water starts getting hot?

I'm wondering about the expansion vessel and whether the pressure is occasionally so high that the pressure relief valve is operating to allow some of the water to escape.

 

[Harrowslayer]

the pressure does rise when the hot water is on but not significantly. I've just been outside and looked at the pressure release pipe and there is some water there??

 

[jackthom]

If it's rising from 1 bar to say 1.5 bar, that would be reasonable.

It's possible the pressure release valve has stuck so I'd repressurise the boiler, tie a polythene bag on the pressure release pipe, fire up the boiler and check later to see how much you catch.

 

[Harrowslayer]

thanks for that I'll give it a go.

how do i repressurise the boiler??

 

[jackthom]

thanks for that I'll give it a go.

how do i repressurise the boiler??

Sorry, I just meant refill it as you have been doing to get the pressure up to normal (1 bar?).




Edit: There's a bit about these valves (PRVs) in the FAQ http://www.diynot.com/forums/viewtopic.php?p=308252#308252