What is a Furnace Gas Draft Inducer and How Does it Work?

By | January 15, 2024

How Does a Furnace Gas Draft Inducer Work
A draft inducer is a necessary furnace component that helps to vent toxic gases out of a home.

Venting toxic gases out of the space being heated is needed to keep the inside air breathable.

What is a Furnace Gas Draft Inducer?

The combustion chamber in a furnace burns gas and contains harmful carbon dioxide as a byproduct.

The furnace draft inducer vents the toxic gasses that come from the burner.

An inducer motor ensures there is a constant flow of air outside through a vent, so no toxic gasses enter a home.

A draft inducer pulls toxic gasses from a furnace by creating a small vacuum and pushes them out of a vent pipe.

An inducer should start before the furnace turns on to make sure the gasses are vented.

When an inducer motor doesn’t work, the lines may be clogged, or the motor has gone bad and needs to be replaced.

The motor and the fan blade are balanced and aligned at the factory, so if you have to buy an inducer, you will have to buy the whole assembly.

A bad Pressure Switch will also cause the inducer not to work. The pressure switch is there to sense when the inducer motor creates a vacuum.

If the sensor doesn’t sense a vacuum, it will not start the furnace.

Basic Furnace and Inducer Start Cycle

  1. The thermostat sends a signal for heat.
  2. The Inducer motor begins to spin and pull gasses from the unit.
  3. The pressure switch senses a vacuum or negative pressure.
  4. The flame sensor detects heat from either the HSI or pilot light and lets in gas.
  5. The gas is ignited by heat source.

The furnace draft inducer is a small motor that creates a vacuum and vents toxic gasses from the combustion chamber.

It is necessary to ensure no toxic gasses enter a home but vent outside.

An inducer also has a switch that senses the vacuum before a furnace starts.

If the switch does not detect a vacuum, it will not allow the unit to turn on.

The switch is a safety feature that makes sure the inducer is working correctly and venting the toxic gases.

Also, keep in mind the electronic control module controls all the components.

Have you had an issue with the draft inducer? Let us know your thoughts below.

Category: Furnace repair

About Aaron H. Benetti

Aaron H. Benetti an HVAC technician who has worked in the field since 1991. He began his career as an HVAC installer and later began doing troubleshooting and repairs. Around 2010, he began to write books on HVAC topics, mainly tutorials and how-to information. Currently, Aaron works as an HVAC tech and also writes many articles and posts for websites as well as books and videos on HVAC topics.

One thought on “What is a Furnace Gas Draft Inducer and How Does it Work?

  1. Gray Reed

    The G26 Lennox inducer motor does not stay on as it should to clear out the exhaust from the heat chamber, then it turns off until the call for heat starts a new cycle. This of course over heats the motor. Also the big Bower Fan stays on continuously, it does not shut off until I turn off the main switch. Every thing else is working as it should. Please help me if you can. I have three other furnaces to pull any parts I would need.


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