no heating after central heating refill

30 Sep 2007
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United Kingdom
Hi all, I hope you can help. I've just drained down an open-vented central heating system to fit a new radiator.

I've refilled the system, bled all the rads, and bled the pump. I've tried to re-boot the system but can't get any heating. The pump is running, the 3-port valve open (even done it manually to make sure), and the thermostat turned up and the controller set to 'heating on'. The boiler however isn't firing up, so it's just cold water getting pumped round.

Is this a boiler issue, somehow caused by an airlock or something, or what?!

Please help
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You need to check for 240V at the boiler switched live first of all.
I'm inclined to agree that you may have 'air lock'.
Did you have 3 port mid positon valve held at mid point on its latch while re filling.
Removing air lock is not always easy. I had to remove a top radiator and run off a couple of buckets of water from each valve to solve my problem.
I'm not too sure I understand what you mean?

I also might not have made myself clear. The boiler is on, the pilot light lit, and it all kicks in when i run hot water, just not heating.
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hi mandate.

The valve only had 'automatic' and 'manual open' options. Is there a second switch on it that I didn't see that lets you select which bits you're opening?
The pump can't circulate the water because it compresses the air, this is because there is too much resistance and no easy escape for the air.
Bleeding radiators to get rid of large pockets of air would take ages,hence the reason for removing radiator and allowing it escape from valves.
On 3 port mid position valve you dont want one of the ports blocked off while re filling cause it causes air locks. The solution is the lever on the side of the valve, you pull the lever which turns the valve to mid point and put the lever on a latch to hold it there till re filling is completed.
The air lock is created by the method of filling ie from the top. If the system could be filled from the bottom all air would be pushed up and escape through empty pipes. From the top the air gets trapped in some cases. :rolleyes:
The boiler should still FIRE for heating - it doesn't know where its call for heat has come from.

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