It appears that the pump is on the return line. I have yet to establish the position of the vent and supply from the header tank in relation to the pump.
The air from the rads is not ignitable.
There is water in the feeder tank.
I am constantly having to bleed my radiators due to ingress of air. How can this happen when I have 3m head of water that should keep the air out? Any suggestion as to where to look for the problem?