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Heating Guide Furnace Control Boards

One way to be a truly responsible homeowner is to familiarize yourself with the major systems and appliances in your home. By having at least some understanding of how, say, your refrigerator or toilet work, you gain understanding of how to use them efficiently and detect when something goes wrong.

The same is true of your Tacoma home’s furnace, which can appear to be a complicated piece of machinery. In order to help you get acquainted with your furnace, we will discuss one of its main control components, the furnace control board.

As the name suggests, furnace control boards are responsible for governing the operation of the furnace. At a minimum, a simple furnace control will control the furnace ignitor (e.g., a spark generator or glow coil), the gas valve and the furnace thermocouple, also called a flame sensor.

More complex furnace control boards will also have control over the blowers and/or the built-in diagnostic system.

To simplify things, you can think of the furnace control board as being a driver and the furnace as its car. Just as the driver oversees all the functions and operation of the car from ignition to shutting off the engine, likewise does the control board for the furnace.

A typical operation sequence for a furnace control board goes something like this:

  1. The control board receives a signal from the thermostat that the temperature is too low.
  2. It starts the ignition system, whether that be a spark generator, glow coil or pilot light.
  3. Once the ignitor is hot, the furnace control board initiates the flow of gas through the burners, where it is ignited.
  4. The control board keeps the furnace running until it is signaled by the thermostat that the temperature is now high enough, or until it detects something is wrong.

(An example of a malfunction where the control board would get involved is a thermocouple that is not detecting enough heat. In this case, the control board would shut off the gas flow to prevent a leak into the home.)