My Vokera boiler builds pressure?

My vokera excell heating the dhw when the tap is turned on for a short period then the water runs cold, any idears

mm
October 2006

you should only refill it to 1.5 bar when cold , if thats what your doing the problem is the expansion vessel has lost its charge or has a burst diapragm , try recharging it ull have to let the pressure out of the system then check the charge in the vessel , footpump will fit, and if it needs to be recharged it says on the data badge of the vessel what the charge should be pump it up , if you get water out of the air point your vessel is burst and you need a new 1

andy plumb
October 2006