Safety Protection
In natural gas furnaces, water heaters, and room heating systems, a safety cut-off switch is usually included so that the gas supply to the pilot and heating system is shut off by an electrically operated valve if the pilot light goes out. This cut-off switch usually detects the pilot light in one of three ways:
- A sensor filled with mercury is used to detect the heat of the pilot light. Contraction of the mercury results in sufficient pressure to operate an electrical switch that interrupts the flow of electricity and shuts off the gas valve when the pilot light goes out.
- A photoresistor is used to detect the light from the pilot lamp. When the pilot light goes out, electrical circuitry connected to the photoresistor shuts off the gas valve.
- Use of a pilot generator or a thermocouple in the flame provides heating appliance safety as it generates enough electrical current from the burning flame to hold the gas valve open. If the pilot light goes out, the pilot generator cools off and the current stops, closing the gas valve.
The above methods are examples of the use of "fail-safe" safety protection.
Read more about this topic: Pilot Light
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