condenser boiler losing pressure when central heating is turned off

[iceman2307]

Hey, I cant get a plumber till next year so thought id try this.
I have a alpha condensing boiler and it works fine...... But when the central heating goes off at night the pressure is at zero by the morning, we have to turn the little valve to fill it back up again. there doesn't seem to be any visible leaks or water dripping outside!
Please help.......

 

[bm1289]

Could be small weep at a fitting whiuch you will never find. Best bet would be Fernox Leak Sealer into filling loop (heating side) and leave overnight. Could also be faulty expansion vessel!

 

[iceman2307]

Would a small weep be the amount of water needed to loose that much pressure?

 

[bm1289]

Yes experienced it myself iceman. A weeping fitting will drop to zero overnight.

 

[Blake]

Have you noticed any water outside from the discharge pipe, the PRV may be passing. Also, how much pressure are you putting in?

 

[iceman2307]

There is no water outside (maybe a drip or two) and we're putting about 1.5 bar twice a day when the heating goes off.

 

[Blake]

When the heating is on, what pressure is the boiler going up to? You should not get any water out of the discharge pipe unless it is faulty or you are putting in too much pressure.

 

[bm1289]

When heating goes off the pipework will contract hence it will probably be leaking from a fitting. If you check fittings/pipework which is visable first if no joy bottle of leak sealer. Less hassle....great results! Fernox injection cannister is easiest method using heating filling loop or radiatior.

 

[Blackcatgas]

As Bronzino has just said, is the copper pipe outside from the prv dripping or not dripping, it should be bone dry.

 

[iceman2307]

Thanks for the replys it sounds like bm1289 has answered it.... The copper pipe has dripped, i can see it on the wall. i also have a plastic pipe which looks dry! could it be the expansion vessel????