Why won't my federal heat system fill? I have drained by system, and fitted a current radiator on the...

I have drained by system, and fitted a current radiator on the end of the 22mm pipes. the rad is a bathroom towel guardrail with non-thermostatic valve (on all the time).When I go to refill the heat system, it just would not flood, until I made one of the other rads on.
How unyielding it is to build furniture lacking...
Answers:    It sounds like your airbound system problem is adjectives solved now.

When you speak "normally it refill after you drain it" I hope you are not draining it all the time. That should be a exceptionally infrequent event since every time you drain it and add unsullied water the alien water have entrapped air that contributes to rusting inside the pipes.
Can anyone explain why this works?
It most imagined is airlocked, go to the matchless radiator in the house and bleed out the upper air as you are trying to fill the system.