What Is a Furnace Draft Inducer Blower?

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A furnace draft inducer blower is a relatively new component of modern furnaces that became part of heating units after government-mandated efficiency standards were enacted. The draft inducer blower's purpose is to move combustion gases out of the furnace and out through the flue vent or chimney. This component determines how much and how fast air will move through the heat exchange unit.

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A furnace draft inducer blower is an electric fan that blows combustion gases out of the furnace and up the flue vent before the burners light. It also provides oxygen to the furnace burners for efficient operation and heating.

Draft Inducer Blower Housing

Although variations occur, a typical draft inducer blower is located in the gas burner compartment of a furnace and consists of a motor-driven wheel assembly or fan, an electrical box for power connections and a metal sleeve surrounding the assembly. Variables include the vent pipe diameter, voltage, amperage, wattage, horsepower and size of the cutout needed for the unit. Always match the blower to the furnace to ensure safety and efficient operation of the unit.

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Components of the Unit

Draft inducer blower components are made of durable plastics and metals, or a combination of both. Polypropylene is used to manufacture industrial draft inducer blowers used in corrosive environments because this plastic resists corrosion better than other materials and will never delaminate. Fiberglass is also used when the component must withstand temperatures above 220 degrees Fahrenheit. Blower size is determined by the size of the unit in which it is located.

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Purpose of the Draft Inducer Blower

As the furnace enters start-up mode, the draft inducer blower turns on 30 to 60 seconds before the furnace burners ignite and purges the heat exchanger of combustion gases that may have remained in that area during the furnace's previous heating cycle. This makes the air in the area cleaner at the time of combustion and also prevents furnace burners from becoming clogged with soot.

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The draft inducer blower stays on while the furnace is in operation, providing a consistent flow of oxygen to the furnace. By improving the quality of air moving through the furnace, it helps improve efficiency of the system.

Operation of the Blower Fan

When a furnace begins a new cycle, the draft inducer blower fan begins whirring 30 to 60 seconds before the furnace burners actually ignite. The fan motor must also run properly and usually has a safety pressure switch connected to the fan housing. Pressure switches ensure the motor is running according to the manufacturers' specifications.

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If the inducer fan motor cannot turn on, the furnace will generally shut off and lock out. Other reasons why the draft inducer blower may ultimately shut down a furnace include a faulty pressure switch, a bad rubber tube component, or there may be a blockage in the furnace flue vent, or even that the blower itself may not be working properly.

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Replacement of the Unit

When the draft inducer blower begins making loud noises, it is still working but it's only a matter of time before replacement is necessary. If the unit has completely ceased working and all other elements have been investigated, it must be repaired or replaced before the furnace can be used. Because many draft inducer blower models are nearly impossible to rebuild, an entirely new unit must be purchased in most cases when one wears out. The exceptions to this rule are units manufactured by Carrier and Bryant.

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