Thank you both for your prompt reply. As chairman of the electrical safety committee at a national lab, I have been asked by some of my colleagues to evaluate a proposed wiring method to be used in new construction of residential units using compact fluorescent downlighting fixtures.
My colleagues have been working closely with the construction and lighting manufacturing industries on a national level as well as UL. The design incorporates some of the features of article 604, Manufactured Wiring Systems. A 'plug and play' lighting system if you will. However one major drawback that I see is the 12 inch limit from last place of attachment, a ceiling joist in their design, for the FMC. Optimally, their design needs about 18 to 24 inches of FMC length from the joist attachment to the fixture. I have ruled out the 3 exceptions under 350-18. I have convinced them that their design should not rely on an exception but should stand alone and pass judgement by an article of the code, not an exception. This would greatly reduce the various interpretations that may arrise by the various AHJ's.
At one time, I'm sure there was justification for the 12 inch limit and that it was not an arbitrary length pulled out of the air. I would be very much interested to know what the justification for the 12 inch length was. Regards, Art
