Combi Losing Pressure?

[OnOff]

Vailent combi boiler problem in an empty property being refurbed - if I leave the wireless stat up i.e. so that the place is excessively warm all's good. However set the stat low just to "keep the frost off" then after a couple of days I get an F22 pressure fault  come up. I have to refill via the two valves on the bottom of the boiler. Pressure gauge climbs into the red after a while and I have to lower it by draining off from a rad. It settles down and all works until I again lower the stat setting. Any suggestions? 

As I say leave the temperature up high and no problems. Just wondering if there's maybe a leaky joint under the suspended ground floor - joint cools and leaks but is fine when hot.

I know NOTHING really about combis.

Cheers

 

[matt.leung]

pressure drops when there is a leak or after bleeding the radiators etc....

 

[SLIPSHOD & SLAPDASH]

Pressure vessel needs recharging. Schneider valve, like a car tyre & pump it up with one of those car 12v ciggie lighter thingies (or take the boiler off the wall and down to the local petrol station)  It only needs a very low pressure (check the manufacturers instructions)

On the Valiants they are normally red, the pressure should be about 1 bar

 

[Andy™]

+1 on expansion chamber. you need to fill it whilst system is un-pressureised

usually at the back somewhere, but you should be able to get at the valve without taking too much apart

 

[ProDave]

+2

Pressure vessel needs recharging, or REPLACING

It's working with no expansion vessel at the moment, so when it cools down the pressure drops. You re charge it. then when it heats up, the pressure is too high as there's nowhere for it to go.

Try pumping up the air bladder, but if that doesn't work it needs replacing. They are not that expensive.

 

[OnOff]

Cheers for that I might as well get BG in as it's under a service contract. Bit miffed as it's not long had it's landlord cert done.

 

[SLIPSHOD & SLAPDASH]

A landlords cert is a bit like ours, its not maintenance but checking the safety of things. I dont mention blown lamps etc.

 

[binky]

To overcome expense of worcester expansion chamber, my plumber added an independent unit to pipework outside of boiler - bigger, cheaper and definetly works.