Erratic pressure

[Varley]

Hi guys,

Am asking this question for a mate on the tiling forum.

He has just moved in to a new build and says the pressure in his combi rises and falls quite erratically, any ideas what the problem might be?

 

[uug197h]

Question is this in the heating or domestic water ? if its the heating it could be air lock or problem with the pump. if its domestic is the cold water pressure erratic if so its a supply problem.

 

[mcmoby69]

let the appliance go cold.check the pressure. fill it to 1 bar. switch it on . does the temp rise quickly?does water come out of the blow off pipe? does the appliance stop working because of lack of pressure at low temp? if it does sounds like the expansion vessel needs either repressurising (bike pump!)or replacing(ball ache)