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Thread: Ground in each conduit?

  1. #1
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    Ground in each conduit?

    I have two conduits running between the same components. One conduit contains three power conductors and the other contains multiple signal conductors. Does each conduit require a ground conductor? Does the parallel conductor requirement of 250.122F apply to this situation?

  2. #2
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    What kind of conduit? Are they metallic and qualify as an EGC?

    Welcome to the Forum.
    Rob

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    All responses based on the 2014 NEC unless otherwise noted

  3. #3
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    Quote Originally Posted by Waka View Post
    I have two conduits running between the same components. One conduit contains three power conductors and the other contains multiple signal conductors. Does each conduit require a ground conductor? Does the parallel conductor requirement of 250.122F apply to this situation?
    As you described it, you don't have any conductors in parallel so no.

    If a EGC must be pulled each raceway only needs one sized per highest overcurrent device protecting conductors in that raceway, but also doesn't need to be larger then the largest ungrounded conductor - you can run into that situation with motor circuits pretty easily.

  4. #4
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    So to be clear, I can run one ground conductor in one conduit and the other conduit does not require a separate ground?

    Also does that mean that multiple conduits running together is considered a single raceway.

  5. #5
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    Quote Originally Posted by Waka View Post
    So to be clear, I can run one ground conductor in one conduit and the other conduit does not require a separate ground?

    Also does that mean that multiple conduits running together is considered a single raceway.
    What he is saying is that the signal conductors are not considered as having any relation to the EGC of the power circuits. The signal handling components will typically be bonded to ground/earth/EGC as part of the circuit supplying power to them. That means that there is usually no need for an EGC in the conduit containing the signal conductors.
    All of the power circuits are in one conduit, so that conduit must act as (raceway EGC) or contain (wire EGC) an EGC functionality suitable for the size of the largest of those circuits.

    If you had two conduits, each containing power conductors, then you would need to consider how the EGC is provided for each independently.
    In the special case that the conduits contain parallel conductors of the same circuit you will need to calculate the wire EGC size based on the total equivalent sized single wire circuit and then put a correspondingly sized EGC in both conduits.

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    Quote Originally Posted by GoldDigger View Post
    What he is saying is that the signal conductors are not considered as having any relation to the EGC of the power circuits. The signal handling components will typically be bonded to ground/earth/EGC as part of the circuit supplying power to them. That means that there is usually no need for an EGC in the conduit containing the signal conductors.
    All of the power circuits are in one conduit, so that conduit must act as (raceway EGC) or contain (wire EGC) an EGC functionality suitable for the size of the largest of those circuits.

    If you had two conduits, each containing power conductors, then you would need to consider how the EGC is provided for each independently.
    In the special case that the conduits contain parallel conductors of the same circuit you will need to calculate the wire EGC size based on the total equivalent sized single wire circuit and then put a correspondingly sized EGC in both conduits.
    Does't even need to be power conductors in each conduit.

    Bottom line is he has two conduits, if both are metallic conduits NEC recognizes both as suitable to use as the EGC (with some exceptions, like more then 6 feet of flexible metal conduit). If you pulled a wire type EGC then it must be sized in accordance with 250.122 and the conductors/overcurrent protection contained in each raceway. The raceway containing control circuit only may end up only being 14 AWG EGC but the raceway containing power conductors may have much larger EGC.

    Reality is if both raceways land in same enclosures at each end - you may essentially have a 14 AWG EGC in parallel with say a 2AWG EGC, but is not a code violation.

    from 310.10(H)(1) - "Aluminum, copper-clad aluminum, or copper conductors, for each phase, polarity, neutral, or grounded circuit shall be permitted to be connected in parallel..."This section does not apply to equipment grounding conductors.

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    Ok so what if both conduits are non-metallic and cannot be used as EGC. Does each conduit require ground conductor?

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    Only the one with the power conductors.

    -Hal

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    Quote Originally Posted by hbiss View Post
    Only the one with the power conductors.

    -Hal
    The components attached to the control circuits likely either are grounded by the power circuits associated with what they are part of or are grounded by mounting on grounded metal.
    If the unlikely event comes about that they are not independently grounded and are still considered likely to be come energized at hazardous voltage then you might need to run an EGC to them as a way of grounding.

    For example, an enclosed low voltage thermostat on a Class 2 circuit does NOT require an EGC.

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    Okay got it. Thanks for all the replies.

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