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Why do electric water heaters have pilot lights?

Why do electric water heaters have pilot lights?
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1 Answer

  1. This is confusing question with overlapping answers.

    A “pilot light” has several meanings:

    • On a gas water heater, stove, furnace, or fireplace without an external power source, a small flame burns continuously in/under the device, known as the pilot light. It produces a tiny amount of heat which heats a thermocouple.
    • The pilot light flame and thermocouple together produce a tiny amount of electric power, which is then used to power the main gas valve on the device.
    • If the device needs to turn on, the electric power from the thermocouple opens the main burner valve and then the pilot also ignites the flame in the main burner.
    • If the pilot light flame goes out, the thermocouple cools, stops producing electricity, and the gas supply to the pilot flame also turns off, so that the building can not fill with an explosive cloud of gas vapors.
  2. On small home electric appliances it is common to include a power indicator light which is also known as a pilot light.
    • It was traditionally orange neon in the past, but now also can be many colors due to the use of light emitting diode technology.
    • The indicator light is used to show that the device is plugged in and receiving power.
    • It also tells people that a heating appliance may be hot and may burn them if they touch the potentially hot surfaces.
  3. Modern gas-burning appliances also commonly have an electric power connection and do not have a pilot flame.
    • They ignite the main gas burner with a high voltage spark igniter similar to in a vehicle engine.
    • They commonly use forced air fans to bring in fresh supply air from outside and push out the exhaust air, so the exhaust is not extremely hot and can be directed out of the building using simple plastic PVC pipe.
    • However, the lack of a pilot flame makes these newer gas heaters dependent on the electric power grid to work. An old gas appliance with a pilot light still works properly if there is a power outage due to a storm, etc.
    • Modern gas appliances without a pilot light will commonly include a power indicator light to show that the appliance is powered and should be working normally, so the light is also useful as a diagnostic tool.
  4. At times in the past, purely electric hot water heaters, stoves, furnaces, etc may not have had any power indicator lights, but many now do.
    • This is really a question of cost and safety. There was a time that user safety was not as much of a concern so heating appliances did not include power indicators, and it was an added manufacturing cost to include them.
    • As with kitchen appliances, including a power indicator on a water heater is useful to assist a homeowner in knowing if the device is getting power and should be working correctly.
    • Additional diagnostic indicators may be included to show if the one or more heating elements are also working correctly.

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