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Thread: 18/16AWG for VFD with 1/2HP Motor

  1. #1
    Join Date
    May 2018
    Location
    Franklinville, NJ
    Posts
    5

    18/16AWG for VFD with 1/2HP Motor

    I've got a 1/2HP motor connected to a VFD rated for 2.3A output current with built in overload protection features. According to NEC 430.124(A) I shouldn't need any secondary overload protection.

    Being a 1/2HP motor I'd like to follow 430.22(G)(2) to use 18AWG wire between the motor and VFD but in this section it mentions using all sorts of different short-circuit/ground fault protection devices, class 20 overload protection, ect... I feel that that it's safe to use 18AWG but is this up to code? Do I need to verify something with the VFD to make sure this acceptable?

    Thanks

    -Dylan

  2. #2
    Join Date
    Dec 2007
    Location
    NE Nebraska
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    38,252
    Quote Originally Posted by SD Dylan View Post
    I've got a 1/2HP motor connected to a VFD rated for 2.3A output current with built in overload protection features. According to NEC 430.124(A) I shouldn't need any secondary overload protection.

    Being a 1/2HP motor I'd like to follow 430.22(G)(2) to use 18AWG wire between the motor and VFD but in this section it mentions using all sorts of different short-circuit/ground fault protection devices, class 20 overload protection, ect... I feel that that it's safe to use 18AWG but is this up to code? Do I need to verify something with the VFD to make sure this acceptable?

    Thanks

    -Dylan
    430.124(A) doesn't omit overload protection, it allows it to be incorporated into the drive.

    430.22(G) (1) and (2) both start out with "Where installed in a cabinet or enclosure," when you leave that cabinet or enclosure to go to your motor I think you still must have minimum of 14 AWG conductor. This basically allows you to use 16 or 18 AWG for portions of the circuit located within a control cabinet.
    I live for today, I'm just a day behind.

  3. #3
    Join Date
    Jul 2006
    Location
    San Francisco Bay Area, CA, USA
    Posts
    8,124
    Why is it important enough to use 18ga that you would work this hard at justifying it? If it's in steel conduit, just use 14ga and be done. My concern here is that you are trying to justify using some sort of portable cord, and that is in advisable on several fronts other than just these NEC issues. The output conductors from a VFD must be either in steel conduit or run with shielded VFD cable, with the shields grounded at both ends.
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