Unable to determine wiring of a 220 fan motor

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  #1  
Old 04-19-12, 03:42 PM
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Unable to determine wiring of a 220 fan motor

I bought a shop fan years ago that came with a nonworking motor. I took the motor to have it checked. The shop added a missing capacitor start and lubed it. They also ran the motor while I was there. Once I got home with it I put it aside and never got around to installing the motor until now, 15 years later. The motor never had an electrical cord so I am attempting to wire one in but I am seeing only 2 wires on the motor, a black and white. I would think there should be 3 wires, 2 120v legs and 1 ground. Am I missing something here? The only numbering on the motor is 30961.
 
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Old 04-19-12, 04:53 PM
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I would think there should be 3 wires, 2 120v legs and 1 ground.
This is a common misunderstanding of how electric is provided to your house. It is not two 120v lines. It is 240v. The 120v commonly used is derived from the 240v to your house. The fan simply needs the two sides of the 240v that comes into your house if it is 240v, not 120v. That is why it only has two wires. You would run a line to your fan from a 2 pole 240v breaker. Almost certainly a 15a breaker and #14 wire will be adequate but tell us the full load amps so we can be sure that is correct. You would need a NEMA 6-15 plug and receptacle.
 

Last edited by ray2047; 04-20-12 at 07:52 AM.
  #3  
Old 04-19-12, 05:09 PM
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Wouldn't the ground normally be connected to a screw somewhere on the motor or frame?
I know it only NEEDS 2 hots.....but everything I've seen at least has a ground connection.
 
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Old 04-19-12, 05:13 PM
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Yes, ground to a ground screw on the motor.
 
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Old 04-19-12, 10:59 PM
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Not sure what the load amps are for this motor since there are no labels. The motor looks pretty old encased in a large cast iron housing. Going by your answer, I would need to run a pair of 120v wire to the black & white wires of the motor then connect ground wire to chassis.
 
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Old 04-19-12, 11:27 PM
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You donít have any information (electrically) about the motor??
 
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Old 04-20-12, 07:24 AM
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I am seeing only 2 wires on the motor, a black and white.
One black and one white wire is the standard coding for 120V. How do you know that this motor uses single-phase 240?
 
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Old 04-20-12, 07:50 AM
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I would need to run a pair of 120v wire to the black & white wires of the motor then connect ground wire to chassis.
No. Please re-read my first answer. You either need a 120v circuit or a 240v circuit. If you are sure it is 240v you need 240v. If you are not absolutely sure test it on 120 volts and see if it runs. Initially test for only a few seconds. If it seems to run try it for a bit longer. First though open up the motor connection box if there is one and look on the back of the plate for a wiring diagram.
 
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Old 04-20-12, 04:55 PM
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Sorry for the misunderstading, I meant wiring the motor with both wire leads from the 240 ckt breaker. I looked for wiring diagrams but found none. The connection box has a homemade cover which I assume the original was lost. I went with the motor being 240v since that is what the shop had stated. At this point, I will do what you suggested and test it first with 120v. I'll post the results once I complete the test.
 
  #10  
Old 04-20-12, 05:16 PM
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Not sure what type of motor you have, but guessing can lead to damaging the motor and other equipment.
 
  #11  
Old 04-23-12, 04:44 AM
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Success! The motor ran fine with 120v and did not even try 240v. I know there are motors that can run either on 120v and 240v but would any one know what the wiring layout would be? I also had some concerns on the fan speed since it did not have a speed control but as luck would have it, the low speed setting was just right for a fan this size. Thanks for the great suggestions I am now ready for any heat wave summer can dish out.
 
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Old 04-23-12, 08:25 AM
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If it runs fine on 120v I would not advise you to test it on 240v. You could easily damage the motor before you could disconnect it. I think you misunderstood the motor shop or they gave you wrong info.
 
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