Electricians? Weird problem!!!!!

[Fuddy1952]

You're correct...and I did think if that and quadruple checked it. I even used things like a beeper (black is hot), ground to ground is zero volts, ground to white neutral zero volts.
Hot to neutral 123.6 volts.
Then I tried extension cord off of another breaker/outlet circuit...same thing.
This time I'll wire in a single outlet box up there...check it with an outlet tester. Then put a plug on fan. I'll plug fan in before mounting it up into cupola, make sure it runs OK.
Even with scaffolding I don't like heights. This time I'll wear my body harness attached to a beam!
It was just my luck...fan is new but purchased a couple years ago.

 

[civilian]

You're correct...and I did think if that and quadruple checked it. I even used things like a beeper (black is hot), ground to ground is zero volts, ground to white neutral zero volts.
Hot to neutral 123.6 volts.
Then I tried extension cord off of another breaker/outlet circuit...same thing.
This time I'll wire in a single outlet box up there...check it with an outlet tester. Then put a plug on fan. I'll plug fan in before mounting it up into cupola, make sure it runs OK.
Even with scaffolding I don't like heights. This time I'll wear my body harness attached to a beam!
It was just my luck...fan is new but purchased a couple years ago.

If you hook your harness to a beam, make sure you have a way to lower yourself back down to the ground. Or you maybe swinging a long ways up. Don't want that. Jon

 

[etpm]

I have read your original post a few times and it is not clear to me how long the fan motor was connected to power before a little smoke came out. So I have some questions. How long was the fan motor connected to power before it started to smoke?

I don't know what to make of the 108 volt reading because I was not there making the test, but it seems like a huge voltage drop. Like there would need to be a really big load on small wires to go from 124 volts to 108 volts.

Because of the amperage rating of the fan motor it is not going to be a shaded pole motor. It is either a split phase start motor, a capacitor start motor, or a permanent capacitor split phase motor. The split phase and capacitor start motors are used when high starting torque is desired. The permanent capacitor split phase motor is used when high starting torque is not necessary. The first two types of motor mentioned will have a switch of some sort that disconnects the starting winding once the motor is at about 85% or rated RPM. Usually this switch is a centrifugal switch. So it is mechanical and you can usually hear it work when the motor is shut off as it slows down. There are also solid state switches and switches that use relays. The permanent capacitor split phase motor will not start if the capacitor is not in circuit. It will just hum.

When power is first supplied to the switched type of motor the motor will hum, as you heard, if it is not allowed to spin. If the starting winding is not energized the run winding will take at least 20 seconds before it gets hot enough to start smoking. If the starting winding is energized but the motor is not spinning the starting winding can start to smoke in about 7 seconds. How long did you keep power to the motor before it started smoking? Did you try to spin the blades?

If the starting winding isn't working and not drawing current the motor will hum and if spun fast enough will start spinning and keep spinning until power is removed.

If it was my fan I would try powering it again as you did at first and see if it works. If it does then your subsequent wiring is suspect. If it doesn't then I would check for what might have gone wrong. Only apply power for a second or two, that is long enough for you to see if the motor is going to star spinning. It sounds like, because the motor is humming, that something is wrong in the starting winding circuit. Maybe a wire got loose somehow. But check the starting winding. I would not be surprised if a visual check is all that is needed.

Because the motor worked and then suddenly stopped it seems to me that either a connection in the motor starting circuit was disconnected somehow or, if a capacitor start motor or a permanent capacitor motor, the cap just happened to fail or was disconnected at this particular time. Maybe from rough handling.
Eric

 

[Fuddy1952]

I was thinking #1,8 &17 posts would answer, however...
1) I ran fan in garage a few times just to be sure it was OK...just 2 wires, hot & neutral.
2) we installed fan in cupola.
3) we ran extension cord up to it...just poked the 2 wires in cord socket...it ran perfectly.
GE motor, I'm guessing 3/4 hp since lable says 120vac 5.5 amps. External start capacitor, didn't seem drawing much current (like arcing when plug into outlet).
4) we ran it at least an hour, even unplug & plug in a few times. It started immediately, spun fast.
5) ran 120v over to it. Black hot, white neutral, bare ground.
6) A box below...120 v (12-2) wire in, 12-3 wire out. In cupola the 12-3 light & fan white neutral together...other end box below this white to input white.
7) cupola light hot to red, black to black fan hot. Grounds together.
8) box below I touched red to incoming hot...light came on. Touched black to black hot...it arced, fan never turned, hum + tiny bit of smoke. Wires touched 2 seconds at most.
9) up in cupola, fan spun freely....went below, touch wires again a second...hummed no turn.
10) unhook everything in cupola to fan, fan leads poked into extension cord exactly as before...plug in exact same outlet...arc, hum, no turn.
Bottom line, my luck, motor start winding smoked apparently. Fan was barely used, like brand new but couple years old.

 

[kenmac]

Bottom line, my luck, motor start winding smoked apparently. Fan was barely used, like brand new but couple years old.

It happens. I have gotten bad parts that were new in the box.
Hard to find quality these days

 

[Buppies]

Sounds like my luck Fuddy

 

[Dftodd]

If you hook your harness to a beam, make sure you have a way to lower yourself back down to the ground. Or you maybe swinging a long ways up. Don't want that. Jon

Keep the phone somewhere in easy reach in case you gotta call for help. Don't put it in a pocket that will be pinched by the harness.