How Does a Furnace Gas Draft Inducer Work?

By | January 25, 2019

How Does a Furnace Gas Draft Inducer Work
A Draft Inducer on a furnace vents toxic gasses that come from the burner.

The Inducer motor insures there is constant flow of air outside through a vent so no toxic gasses enter a home.

A Draft Inducer pulls toxic gasses from a furnace and pushes them out a vent pipe.

An Inducer should start up before the furnace turns on and pull any gasses that may have been left when last run.
 
When an Inducer doesn’t work often 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.
 
Example Furnace Draft Inducer Motor on Amazon.
Rheem Ruud Weather King, RGP Mid Efficiency, Conquest 800 Furnace Draft Inducer Blower FB-RFB241

 
A bad Pressure Switch will also make an Inducer not work. The pressure switch is there to sense when there is a vacuum created by the inducer motor.

If the sensor doesn’t sense a vacuum it will not start the furnace.
 
Here is a common cycle for a furnace to start.

  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.

 
Remember all these functions are controlled by the electronic control module.
 
For more watch these videos.
 

 

 


 




 

One thought on “How Does a Furnace Gas Draft Inducer 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.

    Reply

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