X
The site navigation utilizes arrow, enter, escape, and space bar key commands. Left and right arrows move across top level links and expand / close menus in sub levels. Up and Down arrows will open main level menus and toggle through sub tier links. Enter and space open menus and escape closes them as well. Tab will move on to the next part of the site rather than go through menu items.
The Code Question of the Day (CQD) is NECA and ELECTRICAL CONTRACTOR Magazine’s flagship National Electrical Code (NEC®) public forum for the industry. The daily distribution of Q&A generates a lively dialogue and shares relative Code-based practical responses.
September 11, 2026
Good morning, can Type NM cable be used for the branch circuits in a small commercial strip building? It is wood frame construction with a drop ceiling in the tenant spaces. The GC says commercial means MC only, but I do not see that anywhere in the NEC. Thanks, Carol B.
September 10, 2026
Hi CQD, is it true the NEC does not allow branch circuits from an autotransformer? Trying to get a 240V-only piece of equipment running off a 208V panel with a small buck-boost, and someone told me that is not permitted. Thanks, Dwight R.
Hello Dwight, and thank you for the question. Section 210.9 only allows a branch circuit to be derived from an autotransformer if the circuit supplied has a grounded conductor that is electrically connected to a grounded conductor of the system supplying the autotransformer. For your use case, for 208/240 volt conversions, you are allowed to derive a branch circuit off the load side of the transformer without the connection to the grounded conductor.
The boosted leg cannot be used to supply 120V loads, as the line-to-neutral voltage would be higher than 120V.