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Thread: Transformer working clearance

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    Transformer working clearance

    During an inspection the other day i had come across a 75 kva transformer in a room that has 24" of clearance in front of it. I wrote it up because of the requirements outlined in 110.26 (2014 NEC). The electrician came back and stated it did not need the clearance because it is not likely to require examination, servicing, etc. while energized. For a minute i was buying it but i do not see an exemption for transformers in this section of the code it just states "all electrical equipment". Am i in the wrong for requiring the 36" clearance?

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    Quote Originally Posted by Bkeller1121 View Post
    During an inspection the other day i had come across a 75 kva transformer in a room that has 24" of clearance in front of it. I wrote it up because of the requirements outlined in 110.26 (2014 NEC). The electrician came back and stated it did not need the clearance because it is not likely to require examination, servicing, etc. while energized. For a minute i was buying it but i do not see an exemption for transformers in this section of the code it just states "all electrical equipment". Am i in the wrong for requiring the 36" clearance?
    I think you should reread what the code actually says. The "all equipment" reference is in 110.26 but does not provide for any specific requirements.

    The specific requirements start in 110.26 (A) and refer to "equipment operating at 1000 volts, nominal, or less to ground and likely to require examination, adjustment, servicing, or maintenance while energized".

    I guess the key is whether transformers are likely to require examination, adjustment, servicing, or maintenance while energized.

    Personally, I do not thing it is up to an inspector to make that kind of call.
    Bob

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    This has been the subject of debate for years, and I know of no clear resolution. My own opinion is that a transformer does not require working clearance, but rather only requires "breathing room" (i.e., 6" from any wall). The strongest argument I have heard against this opinion is that a transformer is likely to require thermographic "examination" (this is one of the terms used in 110.26), and that that process must be performed while the item is energized. My counter argument is that that process requires removal of a cover, but does not require reaching past the cover to the interior of the transformer. It is a visual inspection only. OK, it uses the "eyes" of the camera, not just human eyes, but the camera is looking into the enclosure from the outside. I don't believe this fits into the work description in 110.26.
    Charles E. Beck, P.E., Seattle
    Comments based on 2017 NEC unless otherwise noted.

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    I agree that the working depth is not required to meet the 36".
    Rob

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    All responses based on the 2014 NEC unless otherwise noted

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    Thanks for the input guys!! Reading it over a few more times and now getting feedback has opened my thinking up a little bit more I feel better about telling the electrician that i will accept the installation.

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    My state agrees with the electrician.

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    Quote Originally Posted by Bkeller1121 View Post
    Thanks for the input guys!! Reading it over a few more times and now getting feedback has opened my thinking up a little bit more I feel better about telling the electrician that i will accept the installation.
    it might be that whomever is the AHJ for your jurisdiction has some kind of ruling on this. You might want to take a look and find out before blessing it on your own.
    Bob

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