Grant 90 Oil fired Combi Boiler

[badger9913]

Hello

Is there anyone out there that can solve the problem we have. The bolier for some reason loses pressure when its been going for about an hour or so, we have had a new expansion vessel fitted a new pump and a new three way valve. If its left off for a long period it holds the pressure for about 2 or 3 hours then decides to drop to zero. Once this has happened i re fill to 1.5 bar and then whole process starts again.

Has anyone got any ideas as to whats wrong even the plumber is at a loss to what to do next apart from start blanking some of the rads off to eliminate if there is a leak in the area. I also put a bag on the discharge pipe outside but this was empty.

Any advice greatly appreciated.

Cheers John

 

[Boilerman2]

Check the Auto Air Vents - these are notorious for leaking (as the boiler is always at high temperature, the water escapes in the form of steam look for a build up of scale on the AAV bodies (there are 2 on your boiler))
it may be worth checking that the flex connecting the expansion vessel to the boiler is not blocked, otherwise I suspect you have a leak on your system somewhere if no water can be found it must be on below ground floor pipe work

 

[dcawkwell]

Look for a leak somewhere.

My guess would be it's not the boiler if you don't see a leak anywhere near the boiler inside or out.

 

[GasSafeTony]

Check the Auto Air Vents - these are notorious for leaking (as the boiler is always at high temperature, the water escapes in the form of steam look for a build up of scale on the AAV bodies (there are 2 on your boiler))
it may be worth checking that the flex connecting the expansion vessel to the boiler is not blocked, otherwise I suspect you have a leak on your system somewhere if no water can be found it must be on below ground floor pipe work

Same with the Worcesters, had to take the pressure off the system many a time and take out the automatic vent and turn it upside down and reset it.

 

[badger9913]

Hello Guys

OK wil check the Auto Air valves and the connecting valve on the expansion vessel too.
Will report back later on the findings, i forgot to mention that the boiler is 12 years old would this make any difference?

Thanks again for the replies.

J