Quote Originally Posted by swisha
anyone here currently using a squirrel cage fan as a exhaust fan? yea i know a inline fan is much better, but in my case the fan is free.

i recently installed a new furnace and looking at the old unit i noted a fairly new squirrel cage fan in there so i ripped it out for use another day. not sure the cfm's but i do know it was a 125,000btu furnace, and a nice sized fan about 18in tall and atleast 12in wide. fan also has a hi/lo feature.

fired that sucker up and it does move some air. should work fine for exhausting a single room.

probably install a solid state switch to vary the speed.

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Furnace blowers are high velocity with the associated pressure... for a 125MBTU furnace, the blower is probably rated for 1600 - 2000 CFM... thats a massive amount of air. Probably a 3/4 hp motor.

Assuming that the blower is direct drive, it should have 4 speeds. If I can get the make/model of the old furnace, I can probably get the blower curve for it.

There is a solid state device that is available to run that blower as a variable speed, but they are not cheap($300) and available only to legitmate HVAC companies.

Best bet is to build a box to put the blower in so you have something to attach the ductwork to. That particular blower will need the box to be 24 X 24 X however long you want to make it.


And, yes, I am an HVAC tech
Mississippi Steve Reviewed by Mississippi Steve on . squirrel cage fans anyone here currently using a squirrel cage fan as a exhaust fan? yea i know a inline fan is much better, but in my case the fan is free. i recently installed a new furnace and looking at the old unit i noted a fairly new squirrel cage fan in there so i ripped it out for use another day. not sure the cfm's but i do know it was a 125,000btu furnace, and a nice sized fan about 18in tall and atleast 12in wide. fan also has a hi/lo feature. fired that sucker up and it does move some air. Rating: 5