National Electrical Installation Standards

Standards as High as Your Own

The National Electrical Code is the bedrock of the electrical construction business.

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  • ?
    Tuesday, June 25, 2019

    Question:

    Type SE cable with an un-insulated neutral conductor is not permitted for hooking up an electric range in a new branch circuit, it is used as a neutral conductor or an equipment grounding conductor. False What's the article?

    Theodore Raposas
  • ?
    Monday, June 24, 2019

    Question:

    We have an industrial occupancy where single conductors are used in cable tray compliant with NEC 492. Conduit nipples are used at each equipment termination and we have two challenges that we cannot come to agreement on:

    1. NEC 250 requires that each raceway carry a fully rated grounding conductor sized per Table 250.122. These are large ampacity feeders with multiple sets of 500kcmil conductors per phase. The installation includes a single ground conductor its entire length through one of several nipples at each termination and in the cable tray. Question: Is a conduit nipple a raceway? I say yes, and therefor NEC 250.122(F)(1) requires that the ground conductor must pass through each conduit nipple (short raceway). This would also be required to comply with NEC

    2. These same feeders have unsupported conductors between the cable tray and termination points (gear and busway taps). NEC 392.30(B)(3) allows a max. distance of 6’0” between the tray and the equipment, this is not viewed as a restriction on conductor length. The conductor length between the cable tray and conduit nipple at each busway tap is 6’3”. The conductors are formed into a drip loop arrangement to ensure no water migration into the equipment. All the weight of the conductors rests on the termination lugs of the busway. Question: While this appears to meet all applicable NEC 392 code sections, we feel this is poor installation practice: a) the exposed conductors must be supported; b) bend radius minimums must be maintained over time (sag minimized); c) and the stress on the lug terminations must be eliminated. Thoughts?   

    Gil Martin, PE, LEED AP
    A

    Answer:

    Hey Gil thanks for your question. 1) Yes, in your example each conduit "nipple" is a raceway and an equipment grounding conductor is required in each one as stated in 250.122(F)(1)(b). If the conduit nipples are one of the types included in 250.118 they can be used as the equipment grounding conductor if they are continuous from the cable tray to the equipment. It doesn't seem like that is the case in your example. The definition of Raceway in Article 100 and the definition of the specific conduit used, in the respective Article do not have a length limitation for being a raceway.

    2) You are correct a distance of 6 ft is allowed between cable trays and equipment without providing a maximum conductor length as stated in 392.30(B)(3). The conductors must be secured to the cable tray but nothing addresses the termination end such as 400.14 does for flexible cords. Usually this is not a problem as cable and raceway installations inherently provide support for the contained conductors with usually short lengths at the terminations. I agree with your concern and this might be an opportunity for a Public Input for the 2023 NEC.

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ABOUT CHARLIE: Charles M. Trout, better known as Charlie, was a nationally known NEC® expert and author. He served on several NEC® technical committees and is past chairman of CMP-12. In 2006 Charlie was awarded the prestigious Coggeshall Award for outstanding contributions to the electrical contracting industry, codes and standards development, and technical training. Charlie was also a member of NECA’s Academy of Electrical Contracting. Charlie’s experienced team of industry experts keep the CQD dialogue and discussions active and informative in the spirit of the man himself, as he wanted.

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