System a heats lave 15/19 and is located upstairs. It was installed with twin line and a tiger loop. Oil pump is Danfoss BFP 41 l3. We ran out of oil last week and delivery has only just been made. It tries to fire when you press the lock out button but then goes back to lock out. Trying to bleed it and getting a lot of bubbles is this normal? Am I doing the right thing? Anything else that this may be? Thanks