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I have 100' of 10ga wire from my house service panel to a sub panel in my garage.
I need to run my air compressor for a job an additional 100' from my garage.
The air compressor has a 120V, 15amp motor.
If I use a 100', 12ga extension cord for a total of 200' from my house service panel
(100' 10ga + 100' 12ga), will the voltage drop negatively impact my compressor motor ?
 

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Red Seal Electrician
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You're on the thin end. I might try it once or twice to see how it starts, while checking the voltage at the machine with a multi-meter.

240V would be much better. Less current, and half the v-drop. Your motor may be able to be re-wired - check the nameplate. I use a 30' #12 extension cord with my 3hp machine as needed (nema 6-20 ends).

EDIT: I know it would be a PITA, but if its not a huge job, run the machine back and forth to the shop a few times to charge it up. Or if not a huge-volume tool... run a longer air hose instead.
 

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The actual voltage and motor rating affects it. On my area, actual voltage is 126 which gives you 6 volts drop before you get to motor rating of 120. I would get a 10 guage extension cord.
 

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100’ of #10Cu will have 3.1 volt drop at 15A. At 120V that is 2.62% voltage drop.

100’ of #12Cu will have 5.2 volt drop at 15A. At 120V that is 4.34% voltage drop.

So compare your measured voltage (compressor off) and subtract 8.3 volts of calculated drop. Compare to the compressor nameplate.
 
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