Halstead Ace High central heating problem

[notplumber]

When I switch the central heating on, it goes on for a while then switches itself off, leaving the power light flashing green,
If I turn the hot water tap on, the system re-sets itself; same if I switch the system off.
However, when I turn the heating back on it switches itself off again, leaving the flashing green light.
Just prior to this all the radiators have been taken out of the system and washed through before reconnecting them and an additional new radiator has been added in the loft.
The system was re-pressurized with an inhibitor present and bled at each radiator.
The water heating works fine.

 

[petit_pablo]

Likely to be airlocked then. Flashin green light is, iirc, signifying that the boiler is on demand but up to temperature.

Does the heating pipe from the boiler get red hot?

 

[Andygasman2010]

I think a flashing green light on these means pump flow switch hasn't made. It's the one on top of the diverter. Seeing as it works OK on hot water I'd say check the boiler for blockages.

 

[ChrisR]

Can't remember the dignostics , but have you checked the Automatic Air Vent, by the pump, has its cap loose . (Small black plastic cap).

Yours may be scaled up, blocked, not working, cap missing, etc etc.

 

[notplumber]

Thanks for all your comments.
It's flashing green before all the rads are fully up to temperature, so there doesn't seem to be a blockage in the system.
Where would I check for a block in the boiler?
How do I check for an airlock?
Don't think the heating pipe gets red hot - I'll check.
The auto air vent seems to be working - certainly you can hear air hissing when bringing the system up to pressure.

 

[petit_pablo]

Thanks for all your comments.
It's flashing green before all the rads are fully up to temperature, so there doesn't seem to be a blockage in the system.

Rads wont get hot if there is no circulation in the system.

If the Hw works fine then the boiler is probably ok.


How long does the heating stay on for before it cuts out?

 

[notplumber]

The heating stays on until the radiators are at what I would consider to be their normal operating temperature, apart from the last one in the system which is still a bit cooler than I would expect.
Once there, it turns itself off and the green light flashes.
Switching the system off or running the hot tap means I can run the heating again, but only for a few seconds before it shuts down again.

 

[notplumber]

In the best PC tradition I emptied and re-filled the system and heh, what do you know? It seems to be working fine again!
I'll stick it on for a couple of hours this evening to make sure.
Thanks you to all who offered advice.

 

[notplumber]

Spoke too soon!
The system ran for a lot longer than before, but the outcome was the same.
Anyone got a better suggestion?