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Thread: NMC and class 2

  1. #1
    Jeff Remas's Avatar
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    Default NMC and class 2

    Is there a code that specifies how far away class 2 wiring must be from NMC?

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    Default Re: NMC and class 2

    Quote Originally Posted by Jeff Remas View Post
    Is there a code that specifies how far away class 2 wiring must be from NMC?

    Depends on where they are being run.

    Jerry Peck, Construction / Litigation Consultant
    Construction Litigation Consultants, LLC ( www.ConstructionLitigationConsultants.com )
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  3. #3
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    Default Re: NMC and class 2

    No clearance or separation required--as long as you meet the requirements of 725.136 (I). The 2 inch separation is from conductors that are not in that list, basically single conductors as you may find in a cable tray..

    Last edited by Roland Miller; 01-18-2009 at 11:47 PM.
    "Get correct views of life, and learn to see the world in its true light. It will enable you to live pleasantly, to do good, and, when summoned away, to leave without regret. " Robert E. Lee

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    Default Re: NMC and class 2

    Fred with love this--how do you know it is a class 2 circuit by looking at it??

    "Get correct views of life, and learn to see the world in its true light. It will enable you to live pleasantly, to do good, and, when summoned away, to leave without regret. " Robert E. Lee

  5. #5
    A.D. Miller's Avatar
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    Default Re: NMC and class 2

    Quote Originally Posted by Jeff Remas View Post
    Is there a code that specifies how far away class 2 wiring must be from NMC?
    I think this says no restriction unless the Class 2 is for solar photovoltaic:

    (1) 600 Volts, Nominal, or Less. Conductors of ac and dc circuits, rated 600 volts, nominal, or less, shall be permitted to occupy the same equipment wiring enclosure, cable, or raceway. All conductors shall have an insulation rating equal to at least the maximum circuit voltage applied to any conductor within the enclosure, cable, or raceway.
    Exception: For solar photovoltaic systems in accordance with 690.4(B).
    FPN: See 725.136(A) for Class 2 and Class 3 circuit conductors.
    Section 300.3(C)(1) makes it clear that the maximum circuit voltage in the raceway, not the maximum insulation voltage rating of the conductors in the raceway, is what determines the minimum voltage rating required for the insulation of conductors for systems of 600 volts or less.
    The conductors of a 3-phase, 4-wire, 208Y/120-volt ac circuit; a 3-phase, 4-wire, 480Y/277-volt ac circuit; and a 3-wire, 120/240-volt dc circuit may occupy the same equipment wiring enclosure, cable, or raceway if all the conductors are insulated for the maximum circuit voltage of any conductor. In that case, the maximum circuit voltage would be 480 volts, and 600-volt insulation would be suitable for all the conductors.
    If a 2-wire, 120-volt circuit is included in the same raceway with a 3-wire, 120/240-volt circuit having 600-volt conductors, the 2-wire, 120-volt circuit conductors could use 300-volt insulation because the maximum circuit voltage is only 240 volts.
    As noted in 90.8(B), it is elsewhere provided in this Code that the number of wires and circuits confined to a single enclosure be varyingly restricted. For example, 690.4(B) prohibits the location of solar photovoltaic circuits within the same enclosure as conductors of other systems unless the conductors are separated by a partition or are connected together. Additionally, 700.9 requires circuit wiring for emergency systems to be kept entirely independent of all other wiring and equipment according to 700.9(B).


  6. #6
    Jeff Remas's Avatar
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    Default Re: NMC and class 2

    Quote Originally Posted by Roland Miller View Post
    Fred with love this--how do you know it is a class 2 circuit by looking at it??
    Yeah, good question. My answer would be "you don't". I like to check voltage anyway, but still in a residential application as a HI, not code enforcement, we can only ass-u-me that wiring such as thermostats and doorbells are low voltage class 2.

    Now if you were to ask me if I ever found class 2 wiring hooked up to 120 then my answer would be "yes". Sad but true.


  7. #7
    Fred Warner's Avatar
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    Default Re: NMC and class 2

    Roland, I agree with you and Jeff. Hard to tell by casual observance. Fully understanding the function of the circuit would be necessary to make an informed determination.
    A.D., very informative.


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    Default Re: NMC and class 2

    The class 2 power supply has to be listed and labeled, so "class 2" will be stamped or labeled on the power supply somewhere, although not always visible without dismounting it.

    "Get correct views of life, and learn to see the world in its true light. It will enable you to live pleasantly, to do good, and, when summoned away, to leave without regret. " Robert E. Lee

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