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Thread: Transformer

  1. #1
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    Transformer

    Transformer 75kva 480/277 primary to 120/208V secondary is floor mounted installed next to washer and dryer in dentist office staff room. Is that okay per code?

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  2. #2
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    Yup.
    Rob

    Moderator

    All responses based on the 2014 NEC unless otherwise noted

  3. #3
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    Quote Originally Posted by codequestion View Post
    Transformer 75kva 480/277 primary to 120/208V secondary is floor mounted installed next to washer and dryer in dentist office staff room. Is that okay per code?

    Sent from my SM-G935U using Tapatalk
    As long as working and equipment clearances are met, yes. If associated breakers have electronic trip units, panelboards would need to be lockable.

  4. #4
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    Quote Originally Posted by publicgood View Post
    As long as working and equipment clearances are met, yes. If associated breakers have electronic trip units, panelboards would need to be lockable.
    In Wisconsin the powers that be have determined that the working space requirements in 110.26(A) do not apply to transformers. Right or wrong, the reasoning is that transformers are not likely to require examination or servicing while energized. It may be different where the OP is at.

  5. #5
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    Quote Originally Posted by packersparky View Post
    In Wisconsin the powers that be have determined that the working space requirements in 110.26(A) do not apply to transformers.
    Is this stated somewhere in WI SPS 316?

  6. #6
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    Quote Originally Posted by publicgood View Post
    Is this stated somewhere in WI SPS 316?
    Most of the time you need to review the FAQ, published by the State in order to get the official interpretation of SPS316.
    For the most part you should look at previous years also for a historical perspective

    This is for the Winter of 2017.
    http://165.189.64.111/Programs/Indus...ical-Lighting/

    A typical answer is (from Question #3):
    NEC 110.
    26 Requires access and working space be provided about all electrical equipment to permit ready and safe operation and maintenance of such equipment.
    Our current staff consensus and State historical position is that a removable barrier meets the intent of the requirement in NEC 110.26. We would not approve or accept a removable barrier that requires the use of tools to remove. The barrier would need to be constructed to be removed by hand to permit ready and safe operation. The distance shall be measured from the exposed live parts or from the enclosure or opening if the live parts are enclosed.
    Just because you can, doesn't mean you should.

  7. #7
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    Quote Originally Posted by jim dungar View Post
    Most of the time you need to review the FAQ, published by the State in order to get the official interpretation of SPS316.
    For the most part you should look at previous years also for a historical perspective
    I’ve not seen WI take the position of not needing working space for transformers. NFPA 70B would suggest a maintenance aspect.

  8. #8
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    NFPA 70B is not adopted in Wisconsin. From a code class given by DSPS in the fall of 2015. You can also email them at DSPSSBElectrictech@wi.gov or call them at 608-264-7823.

    1. I have a question in regards to the location of a 112.5 KVA dry type transformer. Thetransformer is proposed to be located within a 8’ x 8’ square room with a 4’ ceilingheight, the access opening into this room is 30” wide x 36” tall. Is this installationacceptable? NEC 110.26 (A)(3) requires the 6’6” height, but I know in the past the Statehas said 110.26(A)(1) does not apply to transformers, so I am assuming (A)(3) doesn’tapply either. NEC 110.26(C)(1) requires sufficient access to and egress from the workingspace, is the 30” wide by 36” tall opening acceptable?

    Answer: Yes, YesCode Reference: NEC 450.21(A); SPS 316.110; AHJFor a dry-type transformer rated not over 112 ½ kVA installed indoors needs aseparation of 12 inches from combustible material unless separated from the combustiblematerial by a fire-resistant, heat-insulated barrier. The exception to this requirementindicates that if this transformer is rated 600 volts or less and completely enclosed withor without ventilating openings, then the 12 inch requirement is not necessary. As for theinstallation described in the question, the transformer would not likely need to be, norshould be energized while servicing. NEC 110.26(A) declares that the requirements inNEC 110.26(A)(1), (A)(2) and (A)(3) apply to equipment likely to be energized forexamination, adjustment, servicing or maintenance.

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