Vaillaint ecotec 615 dumping water

[tally100]

My boiler system has been going cold wuth the boiler a Vaillaint ecotec 615
giving a f.22 code and i have had to top up with water to get it going.
I have checked for a leak on my rads and put a cup under the expansion pipe outside to check for water coming out of it.It has been ok for a week running at 1.5 bar when cold and i have just finished a night shift to find the cup half full of water and the boiler off giving f.22 again so its not a leak but the boiler dumping water, just my luck its out of warranty at 2.5 years old and was serviced in June. Any body any ideas whats wrong please.

 

[petit_pablo]

What does the pressure get to when its hot? The expansion vessel prbably requires recharging

 

[tally100]

Hi

Its been running at 1.5bar when cold but its just been heating the water in the tank i forgot to say the central heating on last night for the first time in ages so thats maybe why it happened last night