I'm adding some more circuits to a finished garage. Most of the wiring is going in the joist cavities (or in EMT otherwise). Perpendicular to the joists, in the middle of the garage, is a steel I-beam. I can't (don't want to) drill through that. To get across the I-beam, I span it with a fluorescent fixture (non-hanging with built-in J-box). The lighting circuit goes in one side of the fixture and out the other.
Is it OK to also run another circuit through the fluorescent fixture in this manner? I'm basically using the fixture as conduit between two locations.
Best Answer
This is fine as long as they can be joined end-to-end, are identified for through-wiring, or are listed and marked as a raceway, as per NEC 410.64. Just keep in mind that end-to-end joinable luminaires are limited to one branch circuit (that must feed one or more luminaire(s) in the set) in addition to the circuit that is feeding the remaining luminaire(s).
Also, in your case, as per 410.21, the luminaire must be identified for through-wiring in its integral junction box: