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Thermal fuse
A safety device that permanently breaks the circuit if the boiler overheats (e.g., from a failed thermostat or dry-boil condition).
Category: Boilers & Heating
A one-shot safety device that permanently breaks the heating circuit if the boiler exceeds a safety temperature limit. Once it blows, it must be replaced.
Why it matters — Thermal fuses are the last-line defence against runaway heating. If a thermostat fails and the element keeps heating, the fuse prevents fire by cutting power once it senses dangerous temperatures.
Good to know
- A blown thermal fuse usually means something else has failed first — replace the fuse, but also diagnose why it blew (failed pstat, stuck element relay, scale on the temperature probe).
- Fuses come in different temperature ratings — match the replacement to the original specification.