How should safety interlocks be specified for commercial heating elements?

Specify commercial heating-element interlocks from the actual duty: list every trip source—low liquid level, over-temperature, fan failure, emergency stop, door position—and verify each one cuts the heating circuit directly, not merely alarms. Confirm reset mode (manual or automatic) plus delay and reset conditions, so the element cannot restart by itself after a fault. Match power, sheath diameter, material, surface load, IP rating, mounting and thermostat/sensor response to the real machine, then trip-test each interlock and record cut-off time, reset state and measured temperature as acceptance evidence.