every time it fires up it runs for 10 secs then stops it continues to do this for 20 mins or so then cuts out and have to push reset button

steve willis, March 2010

Some boilers cut out for safety reasons.
If the pump fails then the water in the boiler becomes steam and a thermal cutout may trigger, you will usually hear the water boiling in this case.
possibly a faulty thermocouple, this device confirms that the pilot light is lit, if it thinks that the pilot light is out it will cut off the fuel supply.
May have a cut out if the flue is blocked.

gruff, March 2010