My boiler seems to be working fine (Potterton Suprima) the zone valve is open and the pump ( Grundfos 15-50) 'feels' like it's doing it's job. The radiators inlet pipes are heating up but the outlets remains cool. On occasion the furthest radiators lose heat completely.I have bled the radiators and have had a reasonable jet of water coming out. My gut feeling is the flow on the return side of the system has an air block or the pump is not working hard enough. Can someone give me guidance?
