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How to pressurise expansion vessel?

Vaillant Combi boiler VCW 282 central heating expansion vessel needs to be re pressurised as it is causing high pressure in operation causing pressure relief valve to operate giving rise to re- filling twice daily. How to check expansion vessel pressure and how to repressurise it What kind of air pump is required
and what kind of cheap pressure guage is required to check expansion vessel pressure

Donald Finlayson
December 2009

Vaillant Heating, Home Heating Systems Vaillant Boiler Central Heating

Many thanks for the information To both Dave M and a ''heating engineer''
Could Dave M please clarify first words ''Locate Sharadar Valve'' I am not familiar with the term Sharadar Valve Many thanks Donald Finlayson

Donald Finlayson
December 2009

locate sharadar valve [air side] usinng a car tyre foot pump preferabley with system no pressur on it [test for no water in air side apply a small screw driver into same mutch lick letting a car tyre down.pump up vessel to 1 bar or 14.2 lb/ sq ins. once re pressurised top up system and vent rads.

dave m
December 2009

all you need is a tyre press gauge & a bicycle pump, when press is zero pump vessel to 1/2bar(7-8 psi) then pressurise system from cold feed to 1bar. job done. but if you have water coming out of the air valve when you depress it, your expansion vessel is kaput & needs to be replaced. you MUST also put some more corrosion inhibitor in the system. No dont ask me, its too complicated for the layman.

a heating engineer
December 2009