Ravenheat RSF 820/20T?

Hi Pete,
you should have a filling loop as this is a closed system, so you should be looking for a flexi hose which attaches to one of your C/H pipes (this should be a one way valve ie it will let water in but not out). at the other end of the flexi should be a valve which you open to let water in, fetch it up to the right pressure and bleed off your rads and then top up as your pressure will drop in the system.
hope this helps

Darron
August 2008