...ok, with system at rest, completely removed the chrome slotted plug from the pump and neither water or air expelled! (for what it's worth, the system has not been drained down and refilled, these airlocks only became obvious after replacing the actuator head of one of the 2 port valves).
Ok. You should have got a tiny trickle at least. Try spinning it counter clockwise with a small flat bladed screwdriver. Probably coincidence that it’s failed. That or you’ve run it dry.
Thats a pretty powerful pump and will circulate say 0.8m3/hr, 13.3LPM , at a head of 5.8M on speed3, which quite likely will cause pump over on even a clean OV system especially in a bungalow, suggest changing to speed1, this pump will still circulate 0.8m3/hr at a 3.0M head which should satisfy your requirements. On this speed, once you have vented all the air, see if you are getting pump over through the vent, also, get someone to start/stop the pump and watch for any pump over while the pump is starting or/and stopping, if not, and the rads are a bit slow in heating try speed2, 0.8LPM at 4.3M and repeat the tests.
...repeating pump bleed when running, opened the centre slotted plug several times over the course of 10 mins - stacks of loud gurgling and rushing noises from the pump, and from the nearest rad. Anyway, repeated bleeding of the pump seems to have done the trick, as boiler has been firing for 10 mins continuously now and rads are warming.
Will do.
You’re most welcome.
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