Furnace Blower Sizes

Sizes

• Most blowers for residential furnaces range from 7 inches to 9 1/2 inches in height, according to blowers listed at a large industrial supply company. Depth and width both range from around 8 inches to 11 1/4 inches. Much larger than that and you may be dealing with a blower for an industrial-sized furnace. Smaller than 7 inches and the furnace may be for a small apartment.

Power

• Residential furnace blowers all operate on 115 volts to allow them to run on the standard household electrical grid. The current varies from 0.9 amps to 2.0, the latter suiting larger units in bigger homes and buildings. Horse power, a measure of the power output of an electric motor, varies depending on the furnace. Home furnace blower horse power tends to run from around 1/4 to 1/2 HP, according to Shawn Shouse at the Iowa State University Extension.

Sizing

• It's important to get the right size blower for your furnace. If you're unsure of the model and make, unscrew the furnace control panel. This should give you access to the internal parts, including the blower below the burners. The blower is usually held in place by one or two screws. Always make sure the furnace is off before opening the panel.

Considerations

• If you're replacing your furnace blower, consider buying a more energy efficient alternative. This can save power costs and even help you qualify for energy usage tax credits, depending on current government policy. Many older furnace blowers of any size have efficiencies as low as 10 or 15 percent, according to a report from Ernest Orlando Lawrence Berkeley National Laboratory. This particularly applies to blowers from pre-2000. New variable and PSC furnace blowers can deliver much higher efficiencies.