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Draft Inducer Blowers

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A draft inducer blower is used in a furnace setup to move air and gases through a heat exchanger. The part is a motor-driven small blower wheel assembly. Despite the relative simplicity of the part, there are many different styles and variations. In a given setup, the inducer blower has desired carbon monoxide and carbon dioxide levels preselected and associated with a chosen temperature, cultivated from a mixed flow of exhaust fumes and ambient air. While the temperature of the mixed flow is measured, the flow of the ambient air is concurrently controlled, so as to maintain the mixed flow at the desired temperature.

The blower portion of the draft inducer will blow at different speeds to move the mixed air and maintain the desired temperature. These blowers were not necessary on old furnaces. However, once the government mandated furnace efficiency standards beyond what natural convection could handle, the draft inducer was created. This enabled specific control of how much air moved through the heat exchange unit. That, in turn, made it possible to determine BTUs and the AFUE and, thus, the unit's efficiency.

Types Of Draft Inducer Blowers

There are many variables to observe when checking for a replacement blower. These include the vent pipe diameter, voltage, amperage, wattage, horsepower and size of the cutout required for the apparatus. For example, Grainger's 4C731 blower requires a vent pipe between 5 and 8 inches, using 115 volts, .96 amps and 74 watts, while providing 1/20 horsepower. The device fits in a 3 1/8-by-8 5/8-inch cutout. A top-line Grainger model, 4KA74, uses a vent pipe of 6 to 8 inches and the same 115 volts. However, amperage is 1.51, wattage is 224 and 1/4 horsepower. Looking to a different brand, a Fasco Goodman model A289--comparable to the above 4C731 from Grainger--uses 208/230 volts, .75 amps and 1/30 horsepower. So the differences between brands are, while subtle at a given level, clear nonetheless. Outside of the power parameters, features may include a UC1 Interlock Control, fan proving switch, adjustable damper and vibration isolators.

Replacing A Draft Inducer Blower

The first and most important step to any replacement of a furnace part is to turn off all power to the unit. From there, it should be noted that blowers are normally not replaced in parts--meaning, it's not recommended to try and get only the motor out of a blower but rather to replace the entire blower assembly. As such, the replacement process is easy. The blower is mounted directly to the furnace housing. Simply unscrew the unit, remove it and replace.

Who Makes Draft Inducer Blowers?

Companies that make draft inducer blowers include but are not limited to:

  • A.O. Smith
  • Fasco Goodman
  • Grainger
  • Nordyne
  • Tjernlund Products Inc.
  • York

Question and Answer

Question: I have an inducer motor that is making noise and the Carrier Weathermaker 9200 furnace won't start.

Answer:

On 2016-02-08 Gary wrote:

If the furnace has stopped working the inducer motor may have seized up. These are not designed to be repaired and a whole new assembly will need to be installed.

Question: My inducer motor is starting to squeal - does it need to be replaced?

Answer:

On 2013-02-21 JB wrote:

Probably. If it seizes up then you will have to wait for a repair before you can get heat going again and while it shouldn't be too big of a job, you may not want to wait in the cold.

A good HVAC tech will also tell you if he thinks there is a fix for the current one, but a squealing noise indicates there is friction between moving parts and that is not good. Also, if it is getting very warm it very likely is about to seize.

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