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Boiler issues not firing after refill

View the thread, titled "Boiler issues not firing after refill" which is posted in Boiler Advice Forum on UK Plumbers Forums.

N

Notagainpike

Hi all...got some issues....drained my working ok system yesterday to upgrade some 15 to 22 on the flow and return rad circuit.
Refilled and bled up.
Fired boiler up, had hot water and rads for 3-4 hours...
Turned off to cool.
Boiler would not fire on timer later, demand wouldnt work either....
Noticed that the pump when working did sound like it was passing bubbles...if that makes sense...?
Also, boiler temp was very high, and heat exchanger was boiling hot to touch.
This morning no hot water or heating on timer fired boiler, so i switched both to demand, i think the boiler woke up, but temp went from 30s to 102 in a couple of minutes.....

Last night i cracked the bleed nipple at the bottom of the heat exchanger and there was water present.

Im assuming i have air locked boiler?

I never had any problems like this with the gravity fed system....
 
99% sure it will be air

Check to ensure heat exchanger is vented, system filter too (I've had systems where nearly all air is caught in the filter and it takes ages to keep bleeding it waiting and then repeat). Once everything is vented properly then you need to start getting some flow moving and the pump will soon clear the air. Start with your hot water only.

If your boiler isn't firing still and it sounds like the pump is cavitating then unplug the connector for a second or 2 or hold the switch between 2 different speeds to stall it, this will let the air escape and allow the pump to keep trying to clear the air.

If you have no luck with the hot water (I had one this week) then run the heating only and shut down every radiator but one, if you have a Y plan make sure you turn your cyl stat down to ensure the valve shuts the hot water. Then go round once and turn a new rad on and the old one off each time they get hot, then finally introduce the hot water.

A photo of your pump and pipe work in the airing cupboard may help too
 
fowlerboi said:
99% sure it will be air

Check to ensure heat exchanger is vented, system filter too (I've had systems where nearly all air is caught in the filter and it takes ages to keep bleeding it waiting and then repeat). Once everything is vented properly then you need to start getting some flow moving and the pump will soon clear the air. Start with your hot water only.

If your boiler isn't firing still and it sounds like the pump is cavitating then unplug the connector for a second or 2 or hold the switch between 2 different speeds to stall it, this will let the air escape and allow the pump to keep trying to clear the air.

If you have no luck with the hot water (I had one this week) then run the heating only and shut down every radiator but one, if you have a Y plan make sure you turn your cyl stat down to ensure the valve shuts the hot water. Then go round once and turn a new rad on and the old one off each time they get hot, then finally introduce the hot water.

A photo of your pump and pipe work in the airing cupboard may help too
Click to expand...
OK...heat exchanger vented as in....?
 
fowlerboi said:
99% sure it will be air

Check to ensure heat exchanger is vented, system filter too (I've had systems where nearly all air is caught in the filter and it takes ages to keep bleeding it waiting and then repeat). Once everything is vented properly then you need to start getting some flow moving and the pump will soon clear the air. Start with your hot water only.

If your boiler isn't firing still and it sounds like the pump is cavitating then unplug the connector for a second or 2 or hold the switch between 2 different speeds to stall it, this will let the air escape and allow the pump to keep trying to clear the air.

If you have no luck with the hot water (I had one this week) then run the heating only and shut down every radiator but one, if you have a Y plan make sure you turn your cyl stat down to ensure the valve shuts the hot water. Then go round once and turn a new rad on and the old one off each time they get hot, then finally introduce the hot water.

A photo of your pump and pipe work in the airing cupboard may help too
Click to expand...
Il put a pic up
 
Valve and pump arrangement
 

Attachments

  • 20230316_172407.jpg
Right so its not open vented.

Typically sealed systems are incredibly easy to get air locks out of.

Just to be sure, that's an old photo right? As your pump and valves aren't wired in.

Need a photo above the boiler of pipework arrangement too and one inside to tell you where to vent the heat exchanger, surprised though with a sealed system the pump won't clear that.

Check what speed your pump is set too and then turn it down to 1 which is the slowest, this may help prevent cavitation until the air clears
 
fowlerboi said:
Right so its not open vented.

Typically sealed systems are incredibly easy to get air locks out of.

Just to be sure, that's an old photo right? As your pump and valves aren't wired in.

Need a photo above the boiler of pipework arrangement too and one inside to tell you where to vent the heat exchanger, surprised though with a sealed system the pump won't clear that.

Check what speed your pump is set too and then turn it down to 1 which is the slowest, this may help prevent cavitation until the air clears
Click to expand...
 

Attachments

Try this. No guarantee that it will work but you have few options. Completely lose the bottom pump valve. Slowly loosen the top pump valve's compression nut, water / air will bleed out and may be enough to release the air lock.
 
Close all but one rad closest to the boiler upstairs turn ch on and ramp the pump upto 3 if it’s not already on it and let it run
 

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