Inspection Training

Exhaust Fan Mid and High Efficiency Furnaces

The Exhaust Fan or Draft Inducer Motor on a mid and high efficiency furnace The inducer assembly is a small fan that pulls air through the furnace heat exchanger and sends it to the outside through a vent pipe. In furnaces with an efficiency of 80-90% they are usually made of metal. In furnaces with an efficiency of 90% or more, they are usually made of plastic. The inducer establishes a draft through the furnace and is sometimes referred to as a draft inducer. The motor is powered with 120vac from the furnace control board. During a normal call for heat, the control board will supply power to the inducer. This fan should remain on at all times when the burners are active. If you hear the fan turn on and off, then the furnace is short cycling and you should recommend that the furnace be cleaned and serviced by a qualified contractor. The fan motor can also be very noisy from the bearings failing. Make sure to listen to the start up and shut down of the fan motor and listen for any sounds that could indicate that the fan motor is nearing its life cycle. Look for cracks, corrosion, condensation leaks in the draft inducer and recommend further evaluation if any defect is observed or heard.