Unvented central heating losing pressure only in winter

[Selvara]

thank you. what kind of expert do i need to get to look into? is this normal gas engineer? or unvented engineer?
Because i have kept posting my update that i got gas engineer to look into. He checked expansion vessel and put sealant in the system .but still the issue that pressure goes to zero when system is ideal and automatically goes up to 1 bar when i run central heating/hot water.

 

[JohnD]

He checked expansion vessel and put sealant in the system .but still the issue that pressure goes to zero when system is ideal and automatically goes up to 1 bar when i run central heating/hot water.

thank you. what kind of expert do i need to get to look into?

Try to find a competent one next time.

 

[Harry Bloomfield]

Try to find a competent one next time.

Offer a 'no fix, no fee' job.

 

[Selvara]

looking for someone 'no fix, no fee' job. let me know. RG6 area.

 

[Selvara]

I got second opinion from other gas engineer before i book an appointment with leak detection company.
the gas engineer says that the pressure gauge is in wrong place hence pressure goes to 1 bar from 0 bar low pressure with out topping up.
the gauge is now connected between temp and pressure on cylinder, pump and PRV.
can someone help look at picture and confirm whether the gauge is in wrong place.