central heating/boiler pressure issues /potterton performa24

[thefastone]

Hi
I have Potterton Performa 24 boiler which is about 3 years old (serviced about 12 months ago). Last weekend I flushed and filled the central heating system and adjusted the pressure to the recommended pressure for the boiler e.g. between 0.5 and 1 bar.
the system/boiler does not loose pressure but when the central heating switches on (thermostat kicks in) the pressure drops by approximately 0.2 bar. According the boiler instructions the pressure should rise not fall and the operating pressure should be between 1 and 2 bar as it is the case with the hot water e.g. when the hot water is on the pressure rises and goes to the 1.5 bar which is normal as described in the boiler manual but when the central heating is on the pressure drops? any ideas why and how to fix?

 

[baxpoti]

Not really a problem.

All to do with how easily the pump is moving the water.

Check the expansion vessel pre-charge is 1 bar.

If you have a large system, a second expansion vessel may be required.