expanssion tank in boiler needs re inflating. it holds air in the tank so when the water heats up it will expand into the tank keeping the pressure stable. if there is low air or tank is faulty it will not work as it should causing rise in boiler pressure. it can be inflatted using a car air pump. pressure should be around 1.5bar with the water drained from the boiler. u cant inflate it with water in the boiler
kash, February 2013
