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OT---Attic vent fans

J

Jiles

Well-known Member
I have three roof mounted vent fans. All three fans are run from the same circuit. Today, two of them stopped working after app. 4 years.
I thought it was strange that two stopped at the same time because they were running earlier.
I did all the usual power checks and they were receiving power. I took one of them down--it was a tad stiffer then the other--- and tore it apart.
I saw nothing that would give indication of burnt out! No smell and clean.
Now, both have what I think is a thermal devise. It has two spay connections going into the motor.
It is about the size of a matchbox with this information--
CBB1
300VACC
MAX TEMP 70*C
E158584
This is what I suspect the problem is, so how can I check it?
 
take the leads off the motor and test with voltmeter on ohms , should read close to 0 ,if it reads open and your temp is below the max listed on it it is no good .
but u could put it in the freezer and test it again if it reads near 0 it closed but i would not trust it!!
 
(quoted from post at 03:12:40 06/11/15) take the leads off the motor and test with voltmeter on ohms , should read close to 0 ,if it reads open and your temp is below the max listed on it it is no good .
but u could put it in the freezer and test it again if it reads near 0 it closed but i would not trust it!!
Click to expand...
What does the Max Temp 70*C mean, all attics are much hotter then that in summer? Is this a start capacitor?
 
Since it was a bit stiff. I would oil the bearings and see if it works if it does that was your problem. I would be getting a couple of new motors though.
 
(quoted from post at 03:24:08 06/11/15) Well, 70 C = approx. 160 F, seems like a REAL hot attic.
Click to expand...

OOPS-- Thanks Bob I wouldn't have asked that DUMB question if I had just realized it was Celsius and not Fahrenheit!
Guess I need to pay more attention.
 
You have power to the motors and they don't look bad. Did you try to jump around the thermo devise to see if the motors would run ? If they run than the thermo devise is bad.
 
Many times the vent fan's bushings(bearings) get full of dirt and lock up, then the
thermal overload burns out. Check to see of he fan spins freely, if not take fan
apart, clean bushings, oil, and good chance overload is fried. Use ohmmeter to see if
overload is bad. The overloads on my fans are one shot deals, like a fuse.

I've wired in an external 3a fuse for my vent fans. The idea is for the fuse to burn
out before the thermal fuse, when motor locks up due to dirt.

I also have a short cord on my vent fans, so I can get on roof in the morning, while
cooler, remove the vent cover on roof, unplug cord, and pull motor out without getting
in the attic and getting in the insulation.

4-5 years is about all I get on a vent motor without cleaning and oiling. I used to
get my thermal fuses at Radio Shack which moved out of town.
 
(quoted from post at 21:18:46 06/11/15) Thermo fuses are always crimped on. You can't solder them on.
Click to expand...
pinion: those electric attic vent fans are not worth the effort it take to throw them in the trash! Sorry, terribly inefficient shaded pole motors with crap for bearings. Burn more electricity than any possible savings by heat removal. Mine are all now trashed & replaced by turbines.
 
(quoted from post at 03:14:14 06/12/15)
(quoted from post at 21:18:46 06/11/15) Thermo fuses are always crimped on. You can't solder them on.
Click to expand...
pinion: those electric attic vent fans are not worth the effort it take to throw them in the trash! Sorry, terribly inefficient shaded pole motors with crap for bearings. Burn more electricity than any possible savings by heat removal. Mine are all now trashed & replaced by turbines.
Click to expand...

I share your opinion. However, I have to work with what was installed by previous owner.
 
Jessie,
I agree the motors don't last long before they need taken apart and bushings cleaned.
I install a 1/2 rubber washer over the end of shaft to keep dirt out of bushings and
use synthetic oil in bushings.

However, I think they are cost effective. Proof, my home is total electric. My 2 1/2
ton Rudd 12 SEER AC doesn’t run much and my fixed electric bill went down a few bucks
to $132/mo plus tax. I have a remote switch on vent fan, so during heating season in
late fall until early spring, my fan is off. Use attic heat to warm house a little. I
installed mine 20 years ago, same motor, cleaned a few times, and installed an
external fuse.

I even have a 1500 CFM in pole barn. Only turn it on if I'm working inside. It helps.
 
amen ,,. power ventilaters have caused fires here when they fail ,.. simple turbines are hard to beat
 
I have since removed the other fan and found the same situation. There is no sign of either fan motor being burnt. Fan continues to turn a little after spinning by hand. I have a third identical fan that is still operating, so I removed the capacitor and tried on both the fans.
Both made no attempt to run?
 
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