Gas boiler pressure dropping, faster in colder weather

Hi,

I previously posted about my gas boiler losing pressure:
http://www.askaboutmoney.com/showthread.php?t=98115

I had the gas man in, and he said to call in a plumber. It's one of two thing that I don't exactly remember, including the pressure valve.

Thought I'd ask here as I noticed something during the very cold weather. In temperatures below say 4C, my gas boiler water pressure drops to 0 Bar after maybe 90 minutes of usage, if I let the system cool down.

However, in this not-so-cold weather, the pressure is managing to stick around 1 Bar for about 3 days before needing to be retopped when it dips below 0.4 Bar.

I realise that in colder weather I have the heating on for longer, and that when the house is generally warmer in warmer weather that my room thermostat reaches its desired temperature faster, so the boiler doesn't need to work so hard... but there's still definitely a difference in how the pressure drops.

Does this diagnosis definitely point to one culprit?!

Eoin

Do yo have water leaking at the pipe on the outside wall behind your boiler?

If so, the prv valve will need replacing, but that is only part of the story, it must have activated for a reason.....

1) maybe your pressure vessel has failed, needs recharging, or needs the shreader valve changing, or is possibly too small fro the system (but if too small this would be a constant problem)
2) your filling loop maybe passing sending your pressure to high

where are you located?

Thanks for the tips.

I'm in Limerick city.

Yes, I put a tissue in the escape chute outside and it was definitely wet.

You'll have toe replace the overflow valve. Not too big a job.

Easy to replace but as DGOBS has stated, it is a symtom of another problem. You would need to have the system checked over to find possible fault.

If you wish, pm me and I can give u a number of a Limerick based guy I know

I'm also having this problem.
I've had the plumber out and he gave me a second expansion vessel. His reasoning being that it would even out the pressure. If I leave the boiler on constant it will keep the pressure up for longer but I do have to top up every couple of days.
Does anybody have any suggestions, this has cost me a fortune so far and because I was topping up so much the valve went last month and we've had to get that replaced as well.
The boiler is heating 8 wall mounted radiators and the hot water tank.