Alpha 240 Boiler’s overheat stat & casting device

Hi Everybody,

My newly bought and installed Alpha 240 boiler is showing weird behavior now days. The boiler turns itself on when the heating and hot timers are not allowed to do so. Moreover, another black tool, which is directly under a water tank, also look as if it is dead which else produce buzzing sound whenever I turn on the boiler. I have restarted the boiler but it did not make any difference. Someone please guide me in view of that


Hi Braun,

Firstly, you should check the both i.e. overheat stat & casting device of the Alpha boiler. Normally, people replace the PCB but the main culprit is the casting device. The printed circuit board gets the temperature readings of a heating pipe directly from the casting device. A damaged or out of order casting device will result into the heating pipe become extremely hot than it has to be & ultimately be imposing lockout state on your boiler. It is a safekeeping feature to confirm safety that water will not become intolerably hot. At the normal room temperature, about 14 Ohms is an anticipated reading. In case, you did not get the expected reading, replace the overheat stat & casting device by calling a boiler engineer.