Vaillant Ecotec pro 28

[Cobra123]

Here is my situation: I have a Vaillant Ecotec pro 28 boiler that is about 1.5 years old.
When the heating switches off, the pressure drops and I get an F22 fault code and the heating doesn't come on again until I manually restart the bolier. To get it started again I need to add pressure and then the heating works again. This only happens when the temperature to be reached is lower than the actual one .
For example - The thermostat is set to be on 21 degrees from 7AM-9AM, then it is programmed to drop to 18 degrees. And that's when the boiler gets blocked. The boiler stops working , shows F22 and doesn't not switch on when the temperature is programmed to raise again.
Same when I set the timer on HOLIDAY MODE, the boiler goes into block and doesn't switch on when needed - showing F22 fault
However the pressure doesn't seem to be the REAL problem because we do have enough pressure (not much as we are in an upper miasonette but around 1 bar). Things that we have already done: 1) pumped water into the system 2) changed the sensor and the electric component. WHAT ELSE could it be . HELP PLEASE
Could it be a problem with the thermostat?

 

[Johntheo5]

Does the F22 message flash on and off with the actual pressure displayed in between, if so what is the pressure when F22 is displayed or if the pressure is permanently displayed what does it show?, in either case how much do you have to increase the pressure by/to?.

 

[Cobra123]

Does the F22 message flash on and off with the actual pressure displayed in between, if so what is the pressure when F22 is displayed or if the pressure is permanently displayed what does it show?, in either case how much do you have to increase the pressure by/to?.

Thanks John, the F22 flashes on and off with pressure displayed in between. Sometimes it is 0.7, sometimes 0.4 sometimes 0.0. Other times instead of F.22 I get the image of a flashing spanner. The boiler had these issues from day one but were not as frequent as they are now. I need to restart the boiler 4-5 time a day. I am desperate . And my plumber doesn't know what else he could try.

 

[Johntheo5]

Its very unlikely IMO that its a actual pressure drop, it wouldn't just bounce around like that, possibly a bocked pipe to the pressure transmitter or a electrical issue with the transmitter or wiring, your plumber could check the pressure at the expansion vessel air end (at the schrader valve where its normally tested & the precharge pressure restored, if necessary), that will/should give the true pressure which should be ~ 1.0/1.5bar with a cold system, you can take it from there then, if the boiler is still under warranty you could contact them then informing them of your findings, reminding them of this fault from the start?.