how do I increase system pressure BG532i?

Tony I think that one has a small white key that sits on the panel at the bottom of the boiler(pulls out like a draw). Just right of centre on the underside of the boiler you will find a hole next to a white or grey tap, push it in here making sure it's as far as it can go and then turn the tap to let pressure in 1.0/1.5 bar. then reverse process, there will be a bit of water when you take the key out - make sure the filling knob is off fully.
hope this helps.

Dave Coleman
December 2010