Wiring a Fan Motor

Advice on figuring out whether a motor, purchased second hand, is correctly wired. August 16, 2012

This motor is for a tube axle fan. I bought the fan used and fella I purchased it from said he ran it on 110v with two 20amp breakers which I find weird. I want to run it 220 with a 20amp breaker. I downloaded a PDF schematic and a friend looked at it and said it is wired 220 right now. Can anybody clarify that it is in fact wired at 220? If itís not can somebody post a pic or color coordinate the wires so I can get this running? Any help is appreciated.

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Forum Responses
(Cabinetmaking Forum)
From contributor K:
Look for the schematic which is on the back side of the motor cover you removed for the photo and follow the diagram. The motor leads are numbered and if they are right then you're ok.

From the original questioner:
I was hoping for the diagram on the back of the cover but no such luck. The back of the cover is bare steel.

From contributor K:

I canít tell from your photo but if the diagram is correct then you should follow it. If the guy had it connected with a double pole breaker in a 230v breaker box then it must be wired 230v.

From contributor B:
Does it have four wires from the supply cable leading into the motor electric box and are they all connected to other wires? If so this motor should be ready to go. You just have to try it and see. This motor will run with only one hot leg (110) but it uses fewer amps with two. If the motor runs in the wrong direction, you can reverse the two hot leads (black and red).

Don't switch the connected wires around inside the junction box without a wiring diagram. If you need a longer supply cable, connect it up as it is now by following the same color code connections. If any of this is unsettling to you, call an electrician. Don't forget that the biggest cause of electrocution accidents, is failing to unplug the equipment prior to service.

From contributor L:
This is a single phase motor so it may not be reversible. The wiring diagram will show if it can. If the prior owner ran it on two 20A breakers that were on separate legs of the panel he was running it on 220 not 110V. A real bad practice by the way. Both legs need to open when a fault occurs on one. That's why there is a link on 220 breakers.

From contributor W:
Don't rely on previous connections as there could be some things in there that should not be connected unless you know what's going on. If "T" (thermistor) leads or "R" (RTD) leads are connected to voltage you would be frying internal parts, which could not lead to a happy motor, "H" leads are probably O.K. at 110 applied volts, but probably would be unhappy at 220. All the leads coming out of the motor should be marked with numbers. If you have to rely on color coding check in the manual.

It sounds like the prior owner was running two 110 circuits, one to each half of the windings. Poor practice at best. I'd get the wiring diagram and keep it where it could be found (probably a label that fits inside the connection head cover).