Central heating pressure rises to 3 bar (initial pressure = 1 bar) and pressure valve operates. Once cooled, pressure falls below minimum and trips boiler. Is this a fault with the expansion vessel? If it is, can it be repaired or will it need replacing?

Gary, October 2008

it is the expansion vessel.to repair open pressure relief to zero ch pressure.on the vessel is an air valve like a bike or car tyre valve.attatch a foot pump or similar device and pump up th epressure to 1-1.2 bar ON THE FOOT PUMP GAUGE NOT THE CH PRESSURE GAUGE.REMOVE PUMP AND REPLACE DUST CAP ON THE VALVE.PRESSURISE THE CH PRESSURE TO 1 BAR AFTER BLEEDING SYSTEM OF AIR AND TURN ON CH.WATCH PRESSURE GAUGE it should not go .if it anywhere near 3 bar.if it doesnt its fixed if it does youll need new expansion vessel.hope this helps

cp, October 2008