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Wednesday, April 15, 2009
Question:
Subject: 410.67
Hello Charlie,
When wiring a room full of troffers (2x4 drop-ins), can the wiring method be run from fixture to fixture or does each luminaire need to be terminated in a box?
The basis of my question is: 410.67B seems to allow a wiring method to be used to connect luminaire to luminaire without an outlet box as branch circuit conductors as long as temperature limitations are not exceeded.
410.67C is the only place that I am aware of where tap conductors are referred to besides the tap rule in 240. I feel the intent of this section is to limit the length of conductors smaller than the branch circuit conductors to 6 feet. I also surmise these tap conductors shall be run to an outlet box so they are not inadvertently used as branch circuit conductors, which would carry more load than just the individual luminaire being connected with them.
Thanks,
Mitch Feininger
South Heart, ND
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Answer:
Hello Mitch,
Thanks for contributing. Branch circuit wiring is permitted from luminaire to luminaire provided the fixture conforms to box requirements or is suitable as a raceway for conductors that may feed through the luminaire, such as for end-to-end fluorescent strip lighting installations. NEC 410.67 has been moved to 410.117 in the 2008 NEC. NEC 410.117(C) permits tap conductors to an outlet box for recessed luminaires. The tap conductors must be of a type suitable for the temperature encountered and be at least 18 inches but not more than 6 feet in length. Tap conductors are also addressed in 210.19(A))(4) Exception No. 1(b) and in 402.10 relating to fixture wires.
However your question "When wiring a room full of troffers (2x4 drop-ins), can the wiring method be run from fixture to fixture or does each luminaire need to be terminated in a box?" is I believe covered in 410.65 where luminaires connected together by recognized wiring methods are permitted to contain the conductors of a 2-wire branch circuit or one multiwire branch circuit. 410.117(B) requires branch circuit conductors to have an insulation suitable for the temperature encountered where permitted to terminate in the luminaire.
A more commonly used method is to feed the individual troffers with fixture whips from a junction box containing the branch circuit conductors. The fixture whips are permitted by 402.10(2) and are usually 6 feet in length containing two 16 or 18 AWG copper fixture conductors.
