Boiler cuts out but starts up again

[Chris jenk]

We have a glowworm energy saver 40 boiler.
We have a water tank in the roof and a header tank and a hot water cylinder in the bedroom.
Since we moved in, 6 months ago, the boiler starts up, but then between 2 and 5 minutes later it cuts out. If you leave it alone it cuts back in 10-15 minutes later. But this happens when the thermostat is calling for more heat and the house is still cold. The radiators furthest from the boiler only get a chance to get Luke warm.

If when the boiler cuts out, I run upstairs and turn the temperature dial, on the boiler, to zero, the pump begins. If I wait 20 seconds and then move the temperature dial in between 'low and high', the green light comes on indicating that it is heating once again. However, the same thing happens - after 2-15 mins it shuts off. Sometimes when it shuts off there is a fair bit of banging noises - but not always.
I've bled the radiators
I've washed out each rad in the garden
I've balanced the system
I've checked the pumps working
There are no signs of leaks from the base of the boiler
Any ideas?

 

[Chris jenk]

Actually .....
If I get to the boiler as soon as it cuts out it won't do anything. I have to wait 5 mins or so till it will let me fire it up again by turning the temp to zero.

 

[Billy Bob Bob]

call in a gsr engineer could be many things

 

[smillsey]

I concur