by allon on Mon Jul 25, 2011 7:39 pm
That thing, btw, is an overtemp safety shut off. If the boiler runs dry, the heater temperature will climb. The safety shut off prevents a meltdown by interrupting the circuit to the element.
Note it is rated at 120C, which equates to roughly 2 bar, so it can also be a secondary overpressure safety.
LMWDP #331