We've recently started using the central heating in our new house, and found that the radiators in the loft bedroom were mostly full of air - no heat apart from the bottom of them, and lots of gurgling noises as the water sloshes around. Bleeding the radiators has helped a little, but the pressure now seems to be so low that no more air comes out of them.
At the moment, the pressure gauge on the boiler is around 0.7 bar when not in use, and just under 1 bar when it's on. From what I understand, this is a little low, so might it help to top the system up?
Unfortunately, the people who installed the boiler took off the front panel, so I don't know what model it is. There's what appears to be a filling loop underneath, although this looks different to what I've seen elsewhere: it's a piece of solid pipe, with a red dial (secured by a screw) that's currently pointing to the number 2.
If anyone had any tips on whether the system needs refilling (and how to do it), that'd be really appreciated. I've attached a couple of pics of the boiler and the filling loop.