Boiler cutting out - getting rid of air lock?

[Neil]

When I've previously drained and refilled our heating system, I normally seem to get some air circulating in the system. You can hear when this gets to the boiler (gurgling sounds) and shortly afterwards the boiler cuts out. A few minutes later it resets itself and off it goes again. Normally within a few hours the air finds its way into a radiator, I bleed the rad and then all is well.

However, the last time I drained the system was a few weeks ago and the boiler is still cutting out. I've tried:

-checking all rads are bled

-running with pump on full speed

-the above with all rads bar one closed off (CH & DHW active)

-bleeding at the boiler end (no air came out)

-bleeding at the upright pipe next to the hot water tank in the airing cupboard (small amount of air)

When I ran with all bar one rads closed, this seemed to give some short term improvements (no cut outs for the rest of that day that I was aware of) but it returned to its usual tricks the day after.

I'm loathed to drain and refill as I added fresh inhibitor the last time I filled the system. Any other thoughts or suggestions?

Ta, Neil

[Ed Sirett]

Is it a closed or open system?

[Neil]

ide quoted text -

Open.

[Ed Sirett]

May be you have a blockage where the feed pipe joins the circuit.

[The Natural Philosopher]

What do you mean 'cutting out'?

In my case that usually means a completely unrelated fault.

Blowback into the balanced flue blowing the flame out usually, or a sooted up sensor.

My boiler happily runs with quite a lot of air in the rad system.

However, to clear air locks I did find full pump speed. and one section of pipe at a time would blast the air to a radiator where it could be bled.

[Neil]

.- Hide quoted text -

I think it's fairly normal for boilers to cut out when air passes through them. It flashes the light as an error code - it's some kind of protection cut out that auto resets itself after 3 mins or so, by which time the air has moved on and the boiler gets going again. It's definitely related to air as if you are near the boiler, you hear the gurgling noise start, and seconds later the light starts flashing and the boiler shuts down. I'll maybe try pump on full and small bits of the heating system turned on at a time and see if that has an effect... until someone comes up with another suggestion!

Thanks, Neil