my boiler switches it self off after approx 2 hrs running.
The controller is on but the boiler switches off although the fan continues to run.
If I switch the controller to off them back to on once the boiler will reignite.
We have replaced the boiler thermostat, room stat and 3 port valve but still the same problem.

William, February 2011

when boiler switches off check for voltage at the boiler if there isn't any go through external controls if there is then check fan pressure switch and venturi tube

brian, February 2011