Got a problem with this two boilers. Same problem. The hot water over heats and the burner shuts down after about 20 secs. Went for the obvious and had the D.H.W. sensor changed but it wasn't that. So the guy suggested changing the board. Bit drastic maybe. Could it be limit thermostat? He suggested changing the boiler as the boards are a couple of hundred but there must be an easier solution. Anyone got any suggestions for me. Thanks