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Thread: 480v. and 120v. in same conduit

  1. #1
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    Mar 2005
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    480v. and 120v. in same conduit

    Is it Ok to run 480 volt conductors and 120 volt conductors in the same conduit and pull boxes.

  2. #2
    Join Date
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    Re: 480v. and 120v. in same conduit

    Yes

  3. #3
    Join Date
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    Fort Collins, CO NEC: 2014
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    Re: 480v. and 120v. in same conduit

    See 300.3(C)(1).

  4. #4
    Join Date
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    Re: 480v. and 120v. in same conduit

    I would add that if your jurisdiction is using the 2002 NEC and your installation had neutrals for both systems than you would need to identify one of the neutrals with a white color and continuous stripe. See 200.6(D) in the 2002 NEC.
    Rob

    Chief Moderator

    All responses based on the 2011 NEC unless otherwise noted

  5. #5

    Re: 480v. and 120v. in same conduit

    Also keep inmind Art.210.4(D) - Where accessible(eg.pull boxes/J-boxes) you need to identifythe ungrounded conductors by phase & system.

  6. #6
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    Re: 480v. and 120v. in same conduit

    Originally posted by johndeereman:
    Also keep inmind Art.210.4(D) - Where accessible(eg.pull boxes/J-boxes) you need to identifythe ungrounded conductors by phase & system.
    John that only applied to conductors of a multiwire branch circuit.

    There is no 210.4(D) in the 2005 NEC.

    Now for 2005 we have 210.5(C) which requires all ungrounded conductors in a building with more than one voltage system where accessible to be identified only by system not by phase and system as it had been in 210.4(D)

    In other words all 3 phases of 208 can be black and all 3 phases of 480 could be blue.

  7. #7
    Join Date
    Mar 2005
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    594

    Re: 480v. and 120v. in same conduit

    Standard color code in Ohio for 277Y480 volts is brown, orange, yellow, and slate a.k.a. gray. In fact, some inspectors will not allow those colors on 120Y208 volts even if there is no 480 volts in the building.

    However, I would NOT install 480 ungrounded in the same pipe as 120 volts. 480 volts ungrounded systems have been shown to have an AC overvoltage of up to 2,000 volts from capacitance effects.

    I have installed both 120 volts 2-wire and 480 volts 3-wire off of a 277Y480 volts system with 200 amp class J fuses in the feeder. Actually, class J fuses were mandantory so that the busway plug would meet 1987 NEC wire bending space increase.

    A forklift truck did shear off 1 such feed that had #12 for the 120 volts and #6 for the 480 volts. Tripped both breakers and blew the class J feeder fuses. I can tell you that putting 12 volts and 277Y480 in the same conduit has been TESTED as safe!

  8. #8
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    Re: 480v. and 120v. in same conduit

    Originally posted by mc5w:
    Standard color code in Ohio for 277Y480 volts is brown, orange, yellow, and slate a.k.a. gray. In fact, some inspectors will not allow those colors on 120Y208 volts even if there is no 480 volts in the building.
    Is there a local ordnance that they can cite or do they just make up rules as they inspect?

  9. #9

    Re: 480v. and 120v. in same conduit

    In responce to "iwire". is this not going to be a multiwire branch circuits if you have two diffrent voltages???? Also the industry norm is the way "mc5w" stated that 277/480 is Brown, Orange,Yellow, Gray for the grounded conductor & 120/208 is Black,Red,Blue & White for the grounded conductor & no it is not writen any where how ever this is a good safe practice.

  10. #10
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    Re: 480v. and 120v. in same conduit

    Johndeereman,
    is this not going to be a multiwire branch circuits if you have two diffrent voltages????
    different voltages or systems has no bearing in the definition of a multi wire branch circuit. See the definition of Branch Circuit, Multiwire.

    Roger
    Moderator

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