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Motor wiring

W

Wayne Spence

Joined
Jun 13, 2009
Messages
217
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Location
Denver, Colorado
The air compressor at the sculpture center went out the other day. It is 5hp, 230 volts and 15 amps clearly stamped on the plate. In disconnecting the motor we found only 3 wires, a black hot , a white neutral and a green ground. My very limited electrical knowledge tells me this is a 110 wiring and probably running at 30 amps. Can a 220 volt motor be wired to run on 110? We are uncertain as to buying a whole new unit or replacing the motor only. The shaft seems to be binding up. It is a Craftsman and at least 12 years old.
Any thoughts from the knowledgable electrical people?
 
It seems as you have a 230 volt motor. 2 hot and a ground or neutral. Usually if you switch the black and white it will reverse direction. Definitely not a 110 volt motor. The 15 amp would be in each of the two (black and white wires) for a total of 30 amps. Good Luck,

Dave
 
The motor went out on my 10 year old Powermatic. It was just a little bit more expensive to buy a whole new unit so I purchase a Jet. I couldn't believe how much quieter and more powerful it was. They have definitely made some advances in the last 10 years.
 
Is the world perfect? NO!

Your cord should be two colored and one green. To save on inventory most companies. would use 120 volt wire and put colored tape on white to show that it is hot and not neutral. No neutral needed. A true 5 HP motor will not run on 120 vac. Thirty amp load will trip your breaker. Most power companies will not allow 30 amp/120vac...that will dim your NEIGHBOR's lights.
 
I might have guessed that it is a Craftsman. Sears seems to regularly puff up their specs outrageously. For the record, a 15 amp draw at 230 volts could only deliver 4.6 hp even with a perfect motor and probably less than 4 hp with a real motor. 😕
 
Some suggestions

Wayne, not that it makes much difference, but the motor is not five horsepower. Based on the age of the compressor and the info you gave, I would say that it may be 2.5 to 3 horsepower, but no more. What is it that made you conclude that the motor is bad? The motor can't be wired for 120 VAC nor can it be directly connected to 120 VAC. Dedicated compressor motors from that time frame typically avoided stating motor HP. Instead, a fictitous compressor power was often used -- that was before a class action settlement. They are slightly more honest now.

In a 240 VAC motor there is no neutral, just the two hot phases and a safety case ground. Don't worry about the color of the motor leads. If the nameplate says 230 (240) VAC and the plug is for 240 AC, then that is what it is.

My first inclination would be to suspect the start capacitor, especially if the motor won't turn, but it hums.

I would seriously consider replacing the entire machine since the pump is 12 years old.
 
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