Pressure guage rises to 3 bar when the heating on, is this normal?

macaroon, January 2009

Macaroon, the expansion vessel is almost certainly knackered, done ok for 15 years, my advice would be to get a replacement expansion vessel fitted or, if space permits, an additional expansion vessel alongside boiler ( although it may be time to replace boiler, 15 years is about time for a Vaillant combi)

Peter, January 2009

The boiler is Vaillant VCWGB221H Combi.and is 15years old.
The pressure when cold do stay at set 1bar, but only rise to about 3bar when the heating is on.

macaroon, January 2009

if it works ok and it has been running for several hours and the radiators are all very hot then 3 bar isn't over the top on an average house install.if the pressure was too high a safety release valve would operate and boiling water would come out the overflow pipe.dont worry is my advise.when the system is cold check the bar pressure then.most units seem to be at 1-1.5 bar when at cold/20 deg c

a1, January 2009

Check pressure in expantion vessel this is normaly the big red ball looking thing in the boiler if it is an instantaniouse system or near the pressure guage if it is stored hot water.
The pressure in the expantion vessel should be around 1bar or 14psi and is topped up using a foot pump it will have the same valve as a car tyre.

Andy, January 2009