Boiler/Heating Problem!

BoilerBoy

Hi folks

We've recently moved house and since using the central heating I've noticed a problem with the boiler/system.

It's a Ferroli combi, not sure how old or what model but there isn't a problem with the hot water supply. Basically everytime I use the heating the pressure reduces to below 1 bar after it has cooled down. I have increased the cold pressure to around 2 bar before switching it on but every time we use it it seems to lose pressure afterwards.

It seems fine when it's in operation and goes up to around 3 bar (you'd expect this as the temperature obviously raises the pressure). However it's the same story every time we shut it down.

All of the radiators have thermostatic valves (which I have opened to maximum in order to fully open out the system) except for 2 older ones, in the upper and lower bathrooms. Neither of these radiators heat up when the system is on. The rest are all warm as toast. I haven't noticed any leaks or signs of water where it shouldn't be, however I fear that there may be a leak somewhere that isn't showing, and naturally I'm worried about it. Also I don't want to knacker the system by running it until it is empty.

With winter coming up I need to get this sorted. I really hope it doesn't mean having pay someone to come in and rip up the floorboards.

Any help or advice would be very gratefully appreciated!

Cheers

BB

Canucklehead

Hi

If you look out side the house where the boiler is fitted see if there is a 15mm copper pipe coming out of the wall. Is it dripping or wet?

If so then it's the pressure relief valve that is letting the system pressure out.

The cause is likely to be the expansion vessel in the boiler which has lost it's pressure.
The symptoms of this are what you describe ie
System pressure rises and lets water out of PRV when cool pressure drops and you refill it and so on.
Once the PRV has dirt on it's seating it will drip until it's repaired.

A normal system will have a pressure rise from cold to hot of about half to one bar.

The TRVs on the rads that don't work need the head removing and the pin checking to see if it's moving It will have a limited travel ,about 5 to 10 mm.max.
HTH.

Corgi Guy.

BoilerBoy

Thanks Canuck. Will try what you suggested and report back.

BoilerBoy

Hi Canucklehead

I checked the 15mm pipe and it was slightly damp after using the CH. It wasn't exactly gushing out but it definitely was damp.

Furthermore, I was away all weekend and left the heating off. The gauge never moved so the system is definitely not leaking when cold/off.

How simple/expensive is it to fix a PRV?

Thanks again

BB