Attic Fan Motor, Noise

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jmellc

Senior Member
Location
Durham, NC
Occupation
Facility Maintenance Tech. Licensed Electrician
A neighbor said her attic fan was clanging, sounded like metal on metal. I checked it out & found nothing wrong. I looked for loose mounting brackets, loose fan blades, gap from blades to frame, found none of the usual culprits. I tightened the 4 mounting screws less than 1/4 turn each, so I'm sure it wan't that. Saw no evidence of a bird having flown in & hit the fan.

Like the car acting up til one gets to the mechanic.

Anyone else had this situation? I've had some fans being noisier than others, making more vibrations, etc. I've fixed that kind of thing with rubber spacers on the mounting bolts. That doesn't seem to be the problem here.
 
Did you check for excess play on the motor shaft? Backdraft damper?? I remember in the house I grew up in, we had a whole house fan in the hall, and if you ran the bathroom exhaust at the same time it would cavitate, and scare the bejeesus out of you.
 
I hadn't thought of shaft play. If she complains again, I'll look for that. Can that be intermittent in nature? I had the fan going 2-3 minutes at a time, 10 minutes once, in a 30 minute period.
 
Tell her the next time it happens, to call you and either take the phone to the fan, or leave it on until you get there.

Also, have her repeat her usual routine regarding windows and doors; duplicate all conditions.

Like the car and the mechanic, have here recreate the noise, rather than you trying to.
 
if the bath fan isn't ducted thru the roof, check if it's operation affects the attic fan, as per usmc's post. same with range hood. if all fans are ducted thru the attic, then you can forget about them.

also, how hard is or was the wind blowing when it happens. and from which direction? ask her to make a note of that when it happens again. you can supply her with a wind meter (nail a string in front of her window). if it blows, its' windy. if its wet, its raining, etc.
 
I've usually found that its the shaft setscrew has come loose and the blade worked its way down the shaft or its the bird screen hitting the blades when the wind is blowing a certain direction.
 
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