Open vented System:Glowworm ultimate boiler balanced flue.
Drained radiators. system would not refill from header tank. Backflushed and bled radiators .
Switched system on . Pump then began to run rough and boiler cuts out within a minute. Both flow and return pipes hot straight away. Checked flow pipe had water through the emptying valve.
No water seems to be leaving header tank via cold feed pipe
At moment no central heating or water.
Advice and help needed