National Electrical Installation Standards

Standards as High as Your Own

Monday, September 18, 2023


Hello CQD, thank you for providing this service, I enjoy reading it everyday. My question is regarding dry type transformers and their clearances. Manufacturers will often indicate required clearances behind, and to the sides of a transformer in their installation instructions. Do the clearances required in Section 110.26(A) apply to the front of a dry-type transformer? It is very easy to apply this article to panels, switchgear, and such because there are times where servicing, adjusting, testing and maintenance while that equipment is energized is necessary. A dry-type transformer on the other hand, really is not going to need to be serviced, tested, or maintained while the transformer is energized? It seems to me that the front of dry type transformer would be treated like a large junction box, requiring accessibility. Curious as to what your thoughts would be. Regards, Kevin Tice


Hello Kevin, thank you for your kind words, and for participating in the CQD. The charging text in Section 110.26(A) states: “Working space for equipment operating at 1000 volts, nominal, or less to ground and likely to require examination, adjustment, servicing, or maintenance while energized.”

If a dry-type transformer is not going to be examined, adjusted, serviced, or maintained while energized, then working clearance would not be required. Section 110.2(B) of the 2024 NFPA 70E, Standard for Electrical Safety in the Workplace provides guidance on when performing energized work is permitted.

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