If you can avoid using one, do so, but if you can’t, how do you know what size extension cord for an air compressor is the right size? After all, there are few things aside perhaps from not putting oil in an oil lubed compressor pump, that can damage the compressor than using a too long or too light extension cord.

The same can be said of an electric power bar. It might be convenient if the pressure switch does not have an ON/OFF switch to use the ON/OFF on the power bar to cut power to the compressor. That convenience comes at a cost, however.

My advice has always been, if you need the compressor at the work site, instead of adding way too small 100′ extension cord to try and feed power to the compressor, leave the compressor plugged into the wall socket, and run a longer air line out to the work place where air is needed. A longer air line will quite likely cost less than buying the appropriate length of heavy duty extension cord and could save your compressor motor from unnecessary maintenance.

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I recommend that you do not use a consumer-type power bar ever. They typically aren’t capable of channeling the power demands of all but the smallest fractional HP air compressor motors need to run properly, without damage due to undercurrent.

If you decide that you absolutely must have an extension cord, make sure it’s big enough for the compressor. What follows are only guidelines to help you from disastrously underpowering your compressor motor. You must exercise due diligence to ensure that the extension cord you use will actually adequately power and not damage your compressor motor.

What size extension cord for an air compressor then? Consider the following:

  • On start up the compressor motor draws much more current than when the motor is up and running
  • The distance from the electrical panel to the outlet where the compressor is plugged in must be added to the overall wire length
  • The circuit breaker must be of sufficient amperage for the HP of the motor
  • Copper wire has considerably greater power carrying capacity than does aluminum
  • A too light gauge and lengthy extension cord can overheat and catch fire if the load exceeds it’s capability
  • The temperature where the extension cord is in use can reduce the capability of the extension cord to carry power
  • If in doubt, oversize the extension cord wire
  • Wires are bigger in diameter the smaller the gauge number
  • I would not recommend 14 gauge wire, and would never use #16 gauge, for use as an extension cord to a compressor motor

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For exact figures, or for voltages and HP’s not shown in my graphic, visit any of the following for more information. I am grateful to these companies for the information used on this page…

  • https://www.icmag.com
  • https://www.aceindustries.com
  • http://groverelectric.com
  • http://www.paigewire.com
  • http://wiresizecalculator.net/

…among the many other sources accessed.

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