EXPANSION VESSEL CH BOILER

[bmcewan]

I am looking for some expert advice on my worcester bosch floor standing boiler.when heating is up and running the pressure is steady at 1.5 bar,but when i switch off it drops to 0.I have been told this may be a
problem with the expansion vessel.no water is present in vessel.is it safe for me to pump vessel up to 1.5 bar with bicycle pump as has been advised by a non expert.many thanks for any advice.

 

[baxpoti]

Yes!

 

[chrishutt]

No!

 

[bengasman]

depends!

 

[chrishutt]

1.5 bar is much too high a precharge pressure unless the system pressure needs to be unusually high.

At 1.5 bar precharge and system pressure of 1.5 bar, the EV would still be full of air since the water would push in only when the system pressure exceeds the precharge. Then if the system pressure dropped due to a very minor leak it would fall abruptly to ... er, 0.1 bar or thereabouts.

The EV precharge should be around 0.8 bar - the lower end of the range of acceptable system pressures. The EV will then stabilise system pressure from 0.8 bar upwards.