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

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.

Summary
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.