Conduit
Conduit
(OP)
Sirs, I have some long tubular flourscent light fixtures which I need to hang in a difficult area. I have an idea which through a prototype works fine. I have ran 3/4" conduit which is supported by I beams every six feet. I suspended a 100" tubular light fixture from the conduit. This fixture is not powered through the conduit. The structural integrity of the conduit is not affected in any way. If I lengthen the conduit and run a string of lights off the conduit and power the lights from FX boxes every eight or sixteen feet and run the power through the supporting conduit, is this legal? I have my doubts but we already support hanging HID lights from conduit with the power running through it from the ceiling all over the plant. Thanks for any help on this NEC issue.






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If your conduit is EMT, you cannot support any light fixtures from it anywhere ever.
If it's rigid galvanized conduit, then you probably could do what you want to, SO LONG AS:
1) the conduit was listed for that use, and
2) you avoided contact between dissimilar metals, etc.
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I did find a related but slightly off topic thread at http://www.mikeholt.com/codeforum/ultimatebb.php?ubb=get_topic;f=14;t=000075 -- this is about using empty (unwired) lengths of EMT to support lighting fixtures.
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I'm sure you looked in these three articles, but;
358.12(5)states EMT can't support luminaires (fixtures).
I don't see anything prohibiting IMC or RMC in 342 or 344.
I chased 310.11(B)(3) to 314.23(F)exceptions and thought I had it until I got to exception(d), 12" maximum dimension in any direction from the conduit entry? That eliminates a lot of HID's.
Some UL listed HID's have a threaded hub for primary support. If you hung them from the safety hook they'd hang crooked, it's obviously not for primary support.
I'm not saying it's right, but I've done this before and not had problems with AHJ's. I'm sure other inspectors could find an issue though.
Another example where the code is less than clear.
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Yes you can hang HID fixtures from rigid conduit. The key is to find an "approved" method.
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Think about the possibility of damage to a support. If the pipe starts to fall you may get a "landslide" and have the entire row crash to the floor. I've actually seen it happen with my own eyes, and the installation conformed to the NEC. "Seismic bracing" and supports have become a big deal in recent years, precisely because of this.
Remember the NEC is a MINIMUM standard. It defines the legal limit of just how poor an installation can be. Inside the front cover of my codebook is an "IMPORTANT NOTICE ABOUT THIS DOCUMENT". Actually the NEC isn't intended to be a legal document, but most AHJs use it as one. If you've been in the industry and studied the code very long you'll realize that it is a declining standard. Each edition allows lower standards of engineering and installations by defining the apparent limits and acceptable applications of new methods of doing things a little cheaper. Like alot of things and "legal issues" it has a lot of background and has been heavily influenced by the Insurance industry.