Can someone explain pressure gauge on combi-boiler?

[megmack]

I've just moved house and inherited a Worcester Bosch combi boiler, no manual/instructions, don't know model or age. I've never used a combi boiler before. I switched on the heating tonight and the pressure gauge went up from about 1.3, where it's been for the last week, to over 3 (4 is the maximum). Is this good, bad or indifferent? I switched it off. Should I evacuate the flat if it goes on up to 4?
Thanks, Meg

 

[kevplumb]

3 is the max if its going over that you have serious problems i would check that the pressure release valve is working
and the air charge in the expansion vessel (jeez 3 on the same day)

 

[Slugbabydotcom]

Pressure vessel sounds like its cream crackered or at least needs re-pressurising This is the same problem but on a different boiler, you should find it helpful

 

[ChrisR]

If you've never used a combi the above might be double dutch? There should be a small pipe going straight out through the wall. Can you see if it has been dripping? This is the pressure relief pipe, through which water will escape safely if the pressure goes above 3.

 

[megmack]

Thanks - all a bit daunting. Exit (pressure relief) pipe seems to be dry, so no sign of it sorting itself out. Could this be a temporary problem following non-use over the summer? Or should I call in an engineer?

 

[ollski]

Thanks - all a bit daunting. Exit (pressure relief) pipe seems to be dry, so no sign of it sorting itself out. Could this be a temporary problem following non-use over the summer? Or should I call in an engineer?

Depends how confident you are and which model boiler you have. You need to drain all the water from the heating side of the boiler so the pressure guage reads zero. Then on the red expansion vessel there will be a car tyre vale. You need to put a pump on and pump it back up to about 1 bar, Then repressurize the system with water (again how its done depends on the model). If water comes out of the car tyre valve at any point it will need replacing.