Which is kind of the opposite of what it’s supposed to to. It turns itself off during the heat of the day, but is on in evenings through the morning.
Question is whether this is most likely related to the thermostat or the motor.
Thanks.
My first thought is that there is some sort of thermal protection on the motor.
Do you have to reset a circuit breaker, or does it come back on by itself?
Comes back on by itself.
an attic fan may likely have a thermostat to turn itself on.
a fan will also likely have a thermal fuse to keep it from self destructing and starting a fire. this is a very important safety feature.
A thermostat is supposed to turn it on when it’s hotter, not when it’s colder.
Would the thermal fuse account for it? (I assume it’s part of the motor.)
Question basically is whether I need to replace the motor or the thermostat. (I think I actually have an extra thermostat lying around somewhere, that I once bought by mistake.)
How hot is it getting in your attic? Is it direct drive or belt drive? Is it making any noise (other then normal fan noises)? Can you try to be up there when it shuts down to see if it makes any sounds around that time? Is there any kind of t-stat or timer connected to it? Are you handy? Can you verify that the actual motor is receiving power when it’s not spinning? When it’s not spinning, try hand turning the motor and see if it spins freely. Try cutting power to the motor and then spinning it again? Does it spin freely now? Do you want more questions? I’ll bet I can come up with more, but these will give us a pretty solid starting point.
Oh, be careful sticking your hand in the blades if you don’t know when it’s going to start. Maybe just turn it off and try spinning it. I just want to know if it binds. Trying to spin it with the power on we can worry about later.
A attic fans motor is designed for the hot temps in an attic. If its turning off then I’d check to see if the motor was dirty. Dirt could block the air vents. Look carefully for any oil ports. Older motors should have one on each end of the motor. Newer ones are often just sealed sleeve bearings.
Don’t go into the attic until you’ve switched off the fan. Those blades are very dangerous.
I had to replace my motor a couple years ago. Bearings were shot and making noise.
a fan motor will get hot. it needs the ventilation that it creates to keep cool. if the motor is dusty, lacks lubricant, worn out then it might run hotter than it should.
Pretty darn hot. Can’t be more precise than that, sorry.
There’s certainly no visible belt. I don’t know what’s inside the motor housing.
No.
I’m not sure when it turns off, and plus, it’s pretty darn hot up there, as noted earlier.
There’s a thermostat. Otherwise I wouldn’t be asking.
Compared to who? (My wife thinks I’m very handy, but I’m not going into the handyman business any time soon. :))
Truth of the matter is that it didn’t spin particularly freely even when it was functioning well.
Actually what I was wondering about was whether the fact that it went off in the heat and went back on was itself an indicator as to where the trouble was.
If I was going to do any tests, ISTM that the simplest of them all is to disconnect the wires from the thermostat and touch them to each other. If it goes on, then it’s the thermostat - if not, then it’s the motor. I don’t need to concern myself with any more detail than that. If it’s the motor I’m going to put in a new motor, if it’s the thermostat I’m going to put in a new thermostat. But I thought it might be possible to determine which it was based on the symptoms.
I think this one is sealed.
Actually one reason I’m asking this question here is because I’ve stapled a metal grate in front of the fan, for safety reasons. In order to access the motor I would have to remove that first.
I’ve replaced my motor at least once over the years, and the thermostat at least once too. I don’t remember any special noise, though.
if it doesn’t go on or never shuts off then that might be a bad thermostat.
if it goes on but shuts off while the attic temperature is still high then i would not suspect the thermostat first. i would suspect the thermal fuse is shutting off the motor as it is supposed to. i would check for dust in the motor, lack of lubrication, worn bearings
My money is on the wrong thermostat. I had this issue when I had a vent installed in my laundry room that was supposed to go on when it got too hot based on a thermostat that I could access to set the temperature that would trigger the exhaust fan. Two different electricians couldn’t wrap their minds around this concept and installed a thermostat that shut off the fan when it reached the set temperature. No, guys, I need a air conditioning thermostat, not a heater thermostat.
Some thermostats have a double throw contacts. One closes on temp rise and the other opens. May be wired wrong.
A new motor will probably fix your problem. There’s a reason it’s overheating and shutting off. Either worn bushings, too much dirt etc.
Here’s a thread that I started in 2011. It was requesting help to match up my attic fan motor.
http://boards.straightdope.com/sdmb/showthread.php?t=633251&highlight=Grainger
I got the AO Smith one from Grainger. Exact match for horsepower, RPM, Amps and frame size. Biggest problem I had was getting the old belt pulley off the shaft. I finally took it up to Physical Plant at my job. They had a special puller that levered it off.
Problem with these suggestions is that it worked fine for years. I need something that went wrong.
It would be nice to crawl up there and see if the thermostat stays closed when the motor stops. That would tell you if the thermostat was ok, and point at the motor. Or, connect a light downstairs on the thermostat; the light would go out if the thermostat opened.
when testing the thermostat you need to not put a greater load on it then it is rated for. testing the thermostat can be hard because you (your testing system) and the temperature environment are not always easy to have together at the same time.
it is easier to bypass the thermostat and test the motor. with the fan shut off (by a manual switch not just the thermostat) examine and clean the motor. when you spin the blades with your fingers they should move freely and ideally stay moving after you remove your finger. if not there is a lubrication or bearing problem which would cause overheating and the thermal fuse to shut it off.
if the fan is mechanically OK then bypassing the thermostat should cause the motor to run, unless the attic was super hot then the fan should stay running for a long time.
when bypassing the thermostat you are working with deadly amounts of electricity and should only do so if you know what you should be doing.
Went up today when the motor had shut down in the heat. I turned the thermostat every which way and it made no difference.
But when I turned the switch off and on, it turned on for a second and then died again. (Tried this a couple of times.) What does that say?
[Model is Air Vent Dow-136-0-40-XIN-3/4" (120V 60 GHz 3.1A)]
It’s over heating and turning it off reset the thermal fuse, but it quickly tripped again.
What ever the issue is, bad bearings, blocked vents, no lube…it’s internal. If you can’t just clean out the vents, you probably just need to replace the motor. Didn’t you say upthread that the blades didn’t spin freely by hand with the motor turned off (at the switch)? That’s a sign that it’s getting ready to seize.
Thanks a lot! Would it help if I sprayed in some WD-40 to help lubricate things a bit?
If the bearings are permanently lubricated, then no. If they’re not, then they’ll be a little cap (or few of them or an ‘OIL HERE’ stamp) where you can add, literally, one, maybe two, drops of lube. Zoom-Spout is a good choice. Made for motors and the bottle is designed for getting into those little tiny access holes in hard to reach places at odd angles.
Don’t use WD-40. You’ll probably set your house on fire.