How can I tell if my attic fan can use a 1/5 hp fan motor?


Old 06-30-16, 05:21 PM
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How can I tell if my attic fan can use a 1/5 hp fan motor?

Years ago my attic fan stopped working, so I went to home depot and bought a fan motor they had on the shelf. The fan motor I bought was 1/10 hp. I do not know what the original motor hp was.

I noticed on the home depot web site there are 2 fan motors they sell. One is a 1/10 hp motor for the PR1 fan and the other is a 1/5 hp motor for their PR3 fan.

How can I tell if the fan was originally a PR1 or PR3 fan? Or can I use either safely? I did notice after I replaced the original motor it seemed to blow less air. As far as I can tell both motors are the same size.

Master Flow Replacement Power Vent Motor for PR-1, PR-2, PG1 and PG2 Series-PVM105 - The Home Depot

Master Flow Replacement Power Vent Motor for PR3 and PG3 Series Vents-PVM115 - The Home Depot
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Old 06-30-16, 05:32 PM
Join Date: May 2015
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The HP needed for a fan depends on the blade size, number of blades, their curve, and their pitch. Not really any way to figure it out from looking at the fan.

If you put a 1/10 in place of a 1/5 it may overheat and stop working. If you put a 1/5 in place of a 1/10 it will work fine, everything else being equal (size and speed mostly). So the safe thing to do would be to go with the 1/5.

If there is a plate on the old motor with the current rating, an estimate of HP could be made.
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