Leaking System?

[srestrick]

I have a Ariston euroCombi system which for some unknown reason depressurises to below 0.5 bar when the system is switched off. The boiler will run fine all day, I have even had it running constantly for 3 days with no cutting out. But as soon as the system switches off, the pressure drops and the system will not start.

Water is leaking from the pressure release valve (about half pint to a pint). In order to get the system to come on again you need to fill from the loop, but it only requires a very short burst from the mains to get it going again probably around a half pint. Once the system gets started again, the pressure goes up to around 2.5 to 3 bar and stays there until the system goes off again. Then it is back to having to fill it again!

I have replaced the pressure relief valve thinking the membrane could have been compromised. But either I have bum luck with the PRVs or the probelm is something else. Any ideas?

 

[topcat]

i have a glow worm swift flow and have had the same trouble and i had to have it re- pressureized. it works fine now.

 

[Ant]

I had similar problem with my Saunier Duval combi. It turned out to be the pressure vessel that was shot. They contain some kind of "balloon" that is pressurised - on mine it could be checked with a car tyre valve - I tried to repressurise mine but it needed the whole thing replacing £100+ but fitting was really simple. Like you, I could get the system to work but it kept venting through the overflow/vent pipe and needed to be repressurised.

 

[ogoshi]

Ant is right.if the expansion vessel needs topping up it can be checked with a tyre pressure gauge,then topped up with a car foot pump.if its leaking it will need to be replaced.good luck.