N/C Thermal Switch

1) By N/C you mean 'normally closed' ?? If yes, then say so. Not all know what N/C is. 2) Consult Thomas Directory.

In the same way that a piece of sisal string is tied across the back of the boiler so as to shut the gas supply valve if it burns through due to a blow-back, perhaps a piece of wire of appropriate melting point with an electrical current passing through it? If the wire melts, then the circuit is cut off, a bit like the thermal equivalent of the electrical fuse?

Aren't there soldering iron controls that operate in this temp range? A search of bi-metal controls should come up with some candidates. Kilns have hi-temp controls.

If there are no simple thermostats for this temperature range, you could go to a thermocouple inputting to a simple process controller, with whatever relay logic you might need.

I would also check if "Klixon" has a basicswitchin this range.

there is a type of thermal switch, made in any heat range. they are known, i believe as ptc switches. They are made from ceramic material, impregnated with metal. As the ceramic heats and expands, the electrical flow is disrupted. As they cool off, the electric flow is restored. some ceramic heaters and 12 volt car defogers/heaters use them to create heat. Running 12 vdc through the element heats it up. when it reaches its operating temp, it expands enough to stop the power flow, maintaining a set temp output.