Conduit

[QUAVIET]

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.

 

[MakeItSpin]

What type of conduit are you using?

 

[REDDOG]

Run seperate conduit for power. Cannot use a raceway to support anything

 

[QUAVIET]

I did not think that rigid conduit could be used to support anything. How about the HID lights. They are designed to be supported from 3/4" conduit. There is a 3/4" threaded J-box at the top of the ballast where the conduit is to be screwed into and then suspended from the ceiling. The J-box is designed so that the wire passes through the supporting 3/4" conduit and into the J-box for connection to the ballast. It seems to me that if this is legal then what I propose should be legal also.

 

[MakeItSpin]

You can't use EMT to support fixtures. I'm not aware of the same restriction on RMC or IMC, that's why I asked you what you were using.

 

[advidana]

Just use steel channels to support your fixtures forget about using the conduit to support the lights. Somebody before you just use a dumb idea to support existing lights, maybe he was just a handy man. Don't make the same mistake. Alway check and use your National Electric Code Book.

 

[QUAVIET]

Thank you all for you input. As to the last responder, when you order the HID lamp assembly, the way I described, this is the way it comes from the factory and the way I have seen it commonly used. The rigid conduit supports the HID lamp fixture. Of course I will always use the NEC code. I wrote to ask this question because there seemed to be a conflict. I don't see how a manufacuter can do this when it is UL rated. Of course my prototype is only temporary and I will use stainless angle to support the lights and run the conduit separate. It all pays the same.

 

[advidana]

I believe that the rigid conduit connects to the box that is supporting the fixture. the box and conduits need to be supported by something clamps etc.

 

[peebee]

See NEC 310.11(B), 410.16(F), & 358.12(5) for specific answers to your questions. Here's my interpretation:

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.

 

[peebee]

"310.11(B)" was a typo. Should have been "300.11(B)".

 

[advidana]

Catch 22, where is Steel conduit Listed for it?

 

[QUAVIET]

Sirs, Now I am as confused as if I tried to digest the NEC book. The only logical answer I have is that it would be generally prohibited unless UL approved, even though my idea would be structurally and electrically safe.

 

[peebee]

I can't find anything on the net that addresses UL6 which addresses your question. Maybe a conduit vendor could help.

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.

 

[MakeItSpin]

peebee,

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.

 

[skiier]

I have installed HID fixtures that were supported by rigid conduit. It was in an explosion proof area with a high ceiling. I believe we used a 3/4" conduit to support the very heavy (25lb) explosion proof fixture. The conduit simply threaded in to support the fixture. A locknut was tightened to prevent the fixture from working itself loose from the 3/4' conduit. The conduit was actually pretty long if I remember right. The 3/4' conduit was 8' long and supported from a heavy cast metal j-box. All of this was rigid class 1, division 1 stuff and approved for the use. The 3/4" conduit threaded into an approved "cover" for the j-box. The cover was gasketed and bolted to the box by 4x1/4-20 bolts. The whole thing was pretty solid and was in an area where it was never going to get hit. Not that this stuff couldn't take a hit.The j-box on the ceiling was simply used as a pull box and no joints were made in this box.
Yes you can hang HID fixtures from rigid conduit. The key is to find an "approved" method.

 

[advidana]

you were using crouse hinds or aplleton fixtures with are listed for that type of installation. check with the people that make conduit supports maybe they can help. but no just because the lights can be supported by something does not make it ok. ropes can support conduit but common sense will tell you that is not a good method.

 

[HCBFlash]

In the vast majority of applications "strut" is the best way to support fixtures. Yep. I've even seen it used in residential applications!

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.