When the 28cdi starts up, you should hear the flue fan start followed by ignition spark (viewed through little window with front cover lifted off). Then the gas valve opens and the burner should light. There is a flame detector which will cut system off if no flame. There is no temp stat that needs resetting on my 28cdi (but there is an electronic high temp cut out indicated by flashing red light).
You had best be advised to contact Worcester as you may have faulty PCB or gas valve (around £100 cost each).
xyzbird, October 2008
