hi it your over heat stat mate your heating system does not have a good bye pass causing the the water to heat up in your boiler tripping it out try turning the stat to about 1/4 and run it . if it does not trip out after 30 min you know your problem
rob
January 2008
I have the same blasted boiler and it it a running joke in my house.
The only info i can give you is that the manuals are now located here:
howtomendit.com for free repair help, information and advice.
Try fixfault.com to fix home heating systems.