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  • 240V Compressor Wiring

    I just bought a new air compressor, it's a Puma Model# PK-6060V & I'm a little confused on wiring it up!

    The compressor has a 3HP (running) 6HP (peak) 3440 RPM Motor, it's a F56H frame (compressor duty) capacitor start. Voltage is 115/208 – 230 Amperage is 29.40/16.20 – 14.70
    The motor is factory wired for 230V from the motor side of the pressure switch with 12 gauge SJT cord & the line side is not wired.


    Here's where my confusion comes in: The “very limited” wiring instructions states to use 10 gauge wires & terminals for the line side of the pressure switch? Also the pressure switch looks like it's only rated for 12A. at 240V / 2HP! The pressure switch is a LEFOO model# LF10-4H 150 psi limit. Would the 10 gauge wire be just for voltage drop? Or could this motor draw more than 20 amps at start-up, If so why the factory 12 gauge SJT cord?


    The compressor is only 20' from a sub-panel in my garage so I originally planed to run a 240V 20A line to a two pole disconnect switch mounted on the wall next to the compressor, then wire the switch & compressor with 12 gauge SOOW cable.

  • #2
    Re: 240V Compressor Wiring

    Well my guess is they tell you to use 10ga wire because if you ever want to switch it over to 120v all you need to do is rewire the motor for 120v and the line cord will already be large enough without having to change the cord wire again. If you ran it on 240v you would not need 10ga wire, but it does not hurt to run it anyway. So I guess it is the default for a future 120v hook up.

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    • #3
      Re: 240V Compressor Wiring

      Looking at the link below, this compressor is designed to run on 230 volt. Yes, the motor is dual voltage, but it is wired for 230 volt.
      Follow the manufacturers instructions. This motor can use up to a 50 amp breaker. That could be the reason for the suggestion of the larger wire? Not sure. I would use #10 since the instructions say so.

      Heres the link. Check "tab" "Specs".

      http://www.aircompressorsdirect.com/...ssor/p591.html
      Licensed Electrician

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      • #4
        Re: 240V Compressor Wiring

        Originally posted by John Valdes View Post
        This motor can use up to a 50 amp breaker.
        I'm not familiar with the electrical requirements of a “Compressor Duty” motor but I thought they may need a higher amp starting load than a normal motor. So running 10ga. wire with a 30 amp breaker should be ok?

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        • #5
          Re: 240V Compressor Wiring

          Originally posted by Dwall174 View Post
          I'm not familiar with the electrical requirements of a “Compressor Duty” motor but I thought they may need a higher amp starting load than a normal motor. So running 10ga. wire with a 30 amp breaker should be ok?

          If thats what the instructions that came with the generator state. Always consult the manufacturer instructions first.
          The wire size they use is of no concern to you as long as it is OEM. If supplied with a cord and PLUG, then you use that cord and plug.
          Since it does not have an input cord and plug, you consult the NEC.
          Size the wire by multiplying the motor FLA by 1.25. Size the maximum breaker by multiplying the FLA x 2.50.

          From the information you gave earlier, #10 wire and a 30 amp breaker sound just fine. Keep in mind you can go up to 50 amp on the breaker, without increasing wire size. This is a specific rule/exception for single motors. This is to accommodate the inrush current when the motor starts.

          I hope I was some help.
          Licensed Electrician

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          • #6
            Re: 240V Compressor Wiring

            Originally posted by John Valdes View Post
            From the information you gave earlier, #10 wire and a 30 amp breaker sound just fine. Keep in mind you can go up to 50 amp on the breaker, without increasing wire size. This is a specific rule/exception for single motors. This is to accommodate the inrush current when the motor starts.

            I hope I was some help.
            Thanks that helped out a lot!

            Comment


            • #7
              Re: 240V Compressor Wiring

              Is it possible that the pressure switch is switching 120v and not 240? The motor might be operated by a contactor with 120v on the control side and 240v load side, with the pressure switch energizing the motor starter and in turn starting/stopping the compressor motor.
              "It's a table saw, do you know where your fingers are?" Bob D. 2006

              https://www.youtube.com/user/PowerToolInstitute

              ----

              Time, cost, or quality; pick any two but you can't have all three.

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              • #8
                Re: 240V Compressor Wiring

                Originally posted by Bob D. View Post
                Is it possible that the pressure switch is switching 120v and not 240? The motor might be operated by a contactor with 120v on the control side and 240v load side, with the pressure switch energizing the motor starter and in turn starting/stopping the compressor motor.
                I checked his compressor model and it does not come with a motor starter. Only a pressure switch which theoretically is switching 120 volts as they only break one conductor of a 230 volt circuit. The compressor is listed as 230 volt.
                Licensed Electrician

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                • #9
                  Re: 240V Compressor Wiring

                  Originally posted by Bob D. View Post
                  Is it possible that the pressure switch is switching 120v and not 240?
                  That's kind of what I was thinking also only switching one leg of the switch! Switch is rated at 20A for 120!
                  Originally posted by John Valdes View Post
                  I checked his compressor model and it does not come with a motor starter. Only a pressure switch which theoretically is switching 120 volts as they only break one conductor of a 230 volt circuit.
                  The motor has two capacitors on it so I'm assuming one is for starting & the other one is for running. One leg of the switch is probably just a feed through to energize the start capacitor?
                  Originally posted by John Valdes View Post
                  If thats what the instructions that came with the compressor state. Always consult the manufacturer instructions first.
                  That makes since to me, Everything from the motor side of the switch to the motor is factory wired!

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