Understanding CH pressure vessel settings

[Sussexlad]

I have a Valliant regular boiler. Earlier in the year I had several radiators replaced and a pressure vessel fitted in place of the FE tank.
The red pointer is set to 0.75 bar and the black pointer is at about the same point.
My questions are...
Is 0.75 the correct setting?
What should the black pointer be doing both when the system is at rest and running?
Do you have to check the pressure in the vessel and if so what's the process?
It's not that I particularly want to get involved, I have it regularly serviced but I'd like to have a better idea of what's going on.

 

[Harvest Fields]

When cold the black needle will be lower then when the system water is hot. Any pictures? 0.75 is a little low in my opinion. No you don’t charge the vessel yourself.

 

[Sussexlad]

Thanks for the quick reply. The system has been off for 3 hours or so, but hot water tank is full. Photos attached.

 

[Harvest Fields]

I would expect that to be set at about 1.0 bar

 

[Sussexlad]

I'll have a word with CH guy when he comes later in the month. Thanks.

 

[Harvest Fields]

No worries. We are here anytime.