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Fixable attic fan?

Tom in Madison's picture

Fixable attic fan? (post #206971)

Tom in Madison on Tue, 10/23/2012 - 15:09
in

I have a thermostat-controlled attic ventilation fan that is locking up.  The thermostat clicks, the fan hums but does not turn.  A flick with my finger gets it started and then it cooks right along.  

Is this something that's easily fixed or are we talking replacement?  Fan photo included

Thanks,

Tom

-A +A

These things eventually go (post #206971, reply #1 of 8)

by DanH in reply to Tom in Madison [original] on Tue, 10/23/2012 - 16:54

These things eventually go south (after 5-10 years) because the bearing lube gums up.  You can sometimes take down the fan and work some more lube into the bearings (trickier than it sounds), but it's a lot of work for only a 1-2 year fix.

Generally you're better off replacing the fan or converting to passive ventilation.


Of all the preposterous assumptions of humanity over humanity, nothing exceeds most of the criticisms made on the habits of the poor by the well-housed, well-warmed, and well-fed.  --Herman Melville

Once they get to that point (post #206971, reply #2 of 8)

by florida in reply to Tom in Madison [original] on Tue, 10/23/2012 - 18:37

Once they get to that point you may as well give up. You can clean and oil the motor but I've never had one that ran long once it had seized. Take the motor to Grainger and they'll fix you right up.

Florida Licensed Building Contractor, 40 years experience in commercial remodeling, new homes, home remodeling and repairs and all types building maintenance.

Thanks guys (post #206971, reply #3 of 8)

by Tom in Madison in reply to florida [original] on Wed, 10/24/2012 - 03:47

Thanks for the feedback.  Just a side note, the fan does spin quite easily, and it doesn't seem to have any bearing grind or rumble.  The problem is the motor has trouble initiating the spin.  Perhaps what you're saying is that the worn bearings are the cause of that problem.  Here's a little video of what it looks like.

Bottom line though, probably replace this puppy?  It may not be worth the cost of having the motor looked at.

Tom

It can be a problem with (post #206971, reply #4 of 8)

by DanH in reply to Tom in Madison [original] on Wed, 10/24/2012 - 04:28

It can be a problem with starting, due to a bad start mechanism.  But small motors like that are usually "shaded pole", with no separate start winding, no capacitor, no start switch.  (You don't see a capacitor hiding in or behind the temp switch do you?  I'm assuming that black thing I see at about 5 oclock is a thermal fuse.)  So there's not much to go wrong (and nothing you can replace).  Occasionally, however, the shaded pole windings on the stator short out and cause poor starting.

You can figure out whether it's bearings or starter mechanism fairly simply (though it's more an intellectual exercise than a diagnostic):  Start and run the motor for maybe 3 minutes, then stop it for a minute or so.  Then turn on again and see if it starts on its own.  If it starts it's likely gummed bearings, if not probably a shorted shaded pole (or other start mechanism).

(Anyway, I gave up on roof-mounted fans about ten years ago -- they're just too much of a PITA.  The heat gets to them and destroys them in about 5 years, and they're very difficult to replace.)


Of all the preposterous assumptions of humanity over humanity, nothing exceeds most of the criticisms made on the habits of the poor by the well-housed, well-warmed, and well-fed.  --Herman Melville

Passive option? (post #206971, reply #5 of 8)

by Tom in Madison in reply to DanH [original] on Wed, 10/24/2012 - 12:30

Thanks again for the thoughtful response.  The passive option is simply to disable the fan?  

Tom

"Passive" would be to install (post #206971, reply #6 of 8)

by DanH in reply to Tom in Madison [original] on Wed, 10/24/2012 - 18:38

"Passive" would be to install vents along the ridge, either a ridge vent strip or several mushroom vents.


Of all the preposterous assumptions of humanity over humanity, nothing exceeds most of the criticisms made on the habits of the poor by the well-housed, well-warmed, and well-fed.  --Herman Melville

Passive it is! (post #206971, reply #7 of 8)

by Tom in Madison in reply to DanH [original] on Thu, 10/25/2012 - 17:19

Good deal.  I've already got ridge vents, so I imagine that the fan was just a backup for super hot days.  Thanks everyone for taking the time to answer my questions.

Tom

If you've got (unblocked) (post #206971, reply #8 of 8)

by DanH in reply to Tom in Madison [original] on Thu, 10/25/2012 - 19:26

If you've got (unblocked) ridge vents the fan wasn't doing much good anyway.


Of all the preposterous assumptions of humanity over humanity, nothing exceeds most of the criticisms made on the habits of the poor by the well-housed, well-warmed, and well-fed.  --Herman Melville