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hi i have a boiler that fires up and runs for about 70 seconds then cuts out i think it is the over heat sensor, i'm pretty sure it it is due to air in the system i have bled the radiators, i thought if i put a hose pipe on a drain off valve and connect the hose to a mains tap can i try and push the air out through the expantion pipe what do you think.

Hi, I have the same problem with my gas boiler. Three years ago the same thing happened, the potterton system board had to be replaced. Two weeks later it started to cut out again, overheating. This time the pump was gone so I had get that replaced. Now it's cutting out again. I'm not sure if its the pump or the system board this time. The pump isn't making any noise but there is some heat going to the rads.
Any ideas would be helpfull.

Hi brooks

From the info you've given it sounds like your boiler might well be cutting out as it overheats.

Firstly - does the pump run? If the pump does not run then the water will not circulate away from the boiler after it has heated and will cuase a thermal cut out.

Secondly, I would NOT recommed that you connect a mains to the system and try to flush the air out. If the air was 'free' to come out then it would already have moved up and out of the vent pipe. Also, if you have air in your boiler it will BANG and RATTLE like mad as the air expands much more rapidly than the water and causes the boiler to shake rattle and roll!

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