I checked the air pressure in my Britony 80 combi boiler's expansion
vessel the other day; that's after I lowered the water pressure to
about 0.8 bar. There was no air pressure at all - as I suspected.

I now need to know how many psi of air to pump into it when the water
presure is, say, about 0.8 bar. I'm asking for a psi figure because my
air pressure guage only has psi reading no bar reading.

The expension vessel was originally pre-charged to 0.7 bar according
to the manual.

Thank you

Dave L