Using 120v wire for 240v????

R

rbertalotto

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I been thinking.....

I have a dual voltage (120/240) compressor that is some 50' from the electrical panel in my shop.

It is currently wired to 120V / 20a breaker using three 10g THHN wires in metal conduit. I used 10g simply because I have rolls of it given to me years ago.

Question....Can I use these three wires and a dual pole 20a breaker to wire it as a 240 motor?

Although it has been running for years as a 120v motor, is there an advantage to switching it to a 240v wired motor?

Thanks again...Extremely helpful forum!
 
No. 6 wire. The motor will run cooler and more efficiently. What is the H.P.? as for the breaker.
 
6 gauge wire would be overkill. Your 10 gauge wire is rated for 30 amps. It will do fine. Do black to one pole and white to another. Tape or color the wire black at the motor to let the next person know. Then use ground as ground.

The higher the voltage the more efficient a motor runs.

Say for example, 120v it draws 10 amps. At 240 it might be 4 amps.
 
THHN is rated at 600V, 10AWG can be used for up to a 30A circuit depending on the fill capacity of the conduit. If using a white (neutral wire) for the other leg of the 240VAC you should wrap the white wire with black or red electrical tape at each end to indicate it is not neutral.
 
Of course you can use it for 240 v
Wire isn't picky :)
There will be less voltage drop in the wires on 240 so more voltage to the motor, better performance. Less current and less arcing in the switches so they will last longer- all good reasons to change over to 240 volts, especially with long runs of wire.
-M
 
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Thank you!....When I saw 6g I was like....Even I know that was wrong. Cripes! 40amps is only 8 Ga......
 
Yes, with 240V it will be half the current, so half the voltage drop compared to 120V. And as a percentage of the total voltage, the voltage drop will be 25% of what it was with 120V. It is a win-win.
 
Now, won’t the total wattage draw be the same for both voltages? Is there actually money saved if he switches to 240V?

I know the wiring is cheaper because of the reduction in current draw allows smaller gauge/cheaper wire… but will his electric bill be changed? He’s already got it wired so THHN cost difference doesn’t matter
 
OK, that answeres it. Strangely, I've never bothered to do the math on motor nameplates. Seems an obvious way to determine wattage draw differences.
 
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