410.16 - Means of Support

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Re: 410.16 - Means of Support

Originally posted by j_erickson:
I agree with Pierre. In order to double "when luminaires are supported independent of a suspended ceiling, 410.16(C) does not apply".
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That is interesting that you think that coming from MA. :D

That would mean our amendment to 410.16(C) that says in "lieu of" is a waste of ink.
 
Re: 410.16 - Means of Support

If one is to support fixtures from wires, chains or rod, and the ceiling grid is removed... will the fixtures fall or will the wires, chains or rod still support them? The grid at that point is not there to support the fixtures, it is there to support the ceiling tiles and whatever else is supported by the grid - maybe speakers, etc...

Again, I ask where the prohibition of using other than the ceiling grid is stated in the NEC????

The first sentence of (C) is not directed at the fixtures (luminaires), it is directed at the framing members of the grid. The second sentence is in support of the first sentence, again directing the support of the fixtures to the framing members, if the framing members are used as the fixture support.

Take a look at Caddie's fixture support methods, you will see that some of them are not framing member reliant at all. I know, most of Caddie's material is not listed, but not all NEC material is required to be listed.


Bob
I would not say that the wording of Mass. amendment is wasted, it is a clarification of the unwritten permission to use other than the framing members of the ceiling grid.

I am glad you wrote "respectfully", even if you didn't, I know we have developed mutual respect for each other's thoughts and ideas. ;)
 
Re: 410.16 - Means of Support

Originally posted by iwire:
Originally posted by j_erickson:
I agree with Pierre. In order to double "when luminaires are supported independent of a suspended ceiling, 410.16(C) does not apply".
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That is interesting that you think that coming from MA. :)
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Re: 410.16 - Means of Support

I think this is a case where the intent is not the same as the wording. I think the intent was to allow independent support from the ceiling without requiring the fixture to be attached to the grid. But as Charlie B pointed out, that is not the wording.

I propose a new paragraph for the NEC:

110.01 - If its good enough for MA or NY or Chicago, its good enough for the NEC.
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:D

By the way, after talking to the inspector, he is going to allow independent support as long as the wires are snug. Apparently, his biggest concern is that sometimes the electricians leave a lot of slack in the support wires.

Steve
 
Re: 410.16 - Means of Support

I thank those who have agreed with me. But I am changing my mind. :eek:

It wasn't your argument that convinced me, Pierre. In fact, I was going to throw "Charlie's Rule" on the table, and suggest you read the rule more carefully. But before I did that, I went back and read the rule more carefully myself.

In the quote below, I have inserted the "understood" verb phrase "that are," and highlighted key words in bold capital letters.
IV. Luminaire (Fixture) Supports

410.16 Means of Support.

(C) Suspended Ceilings. Framing members of suspended ceiling systems (THAT ARE) USED TO support luminaires (fixtures) shall be securely fastened . . . .
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Consider the following, and then go back and read the rule again.
There are two kinds of suspended ceiling systems. </font>
  • <font size="2" face="Verdana, Helvetica, sans-serif">Those that ARE USED to support luminaires, and</font>
  • <font size="2" face="Verdana, Helvetica, sans-serif">Those that ARE NOT USED to support luminaires.</font>
<font size="2" face="Verdana, Helvetica, sans-serif">
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The rule is not mandating that we use the suspended ceiling's framing members to support the luminaire. Rather, it is saying that IF we choose to support the luminaire from the suspended ceiling, THEN here are the rules.
 
Re: 410.16 - Means of Support

I still assert that two ceiling wires, on on each of two aposing corners, is not supporting the fixtures. These are redundant or secondary saftey supports used for fire protection.

If one does support the fixture independantly, say four wires, one in each corner. jack chain, thread rod. or some other method. then I see no need for screwing the fixture to the grid.
 
Re: 410.16 - Means of Support

Besides the NEC requirements, there are also building code requirements that may apply. IBC Section 1621 references Minimum Design Loads for Buildings and Other Structures from the American Society of Civil Engineers (ASCE 7). ASCE 7 Section 9.6.2.6.2 references Guidlines for Seismic Restraint Direct Hung Suspended Ceiling Assemblies from the Ceilings & Interior Systems Construction Association (CISCA). Which of those guidelins apply will depend on your seismic design category. I am not familar with the requirments in lesser seismic design categories, but here is an excerpt from page 2 of the guidlines used for seismic design categories D, E, and F.
All lighting fixtures shall be positively attached to the suspended ceiling system. The attachment device shall have a capacity of 100 percent of the lighting fixture weight acting in any direction. When intermediate-duty systems are used, No. 12 gauge hanger wires shall be attached to the grid members within 3 inches of each corner of each fixture. Tandem fixtures may utilize common wires.
[skip a paragraph]
Lighting fixtures weighing less than 56 pounds shall have in addition to the requirements outlined above, two No. 12 gauge hangers connected from the fixture housing to the structure above. These wires may be slack.
Lighting fixtures weighing 56 pounds or more shall be supported directly from the structure above by approved hangers.
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Under the IBC, in seismic design categories D, E, or F (and possibly others), the fixtures are required to be supported by hanger wires as well as being attached to the grid.

Having worked with the UBC in the past, I am quite certain that these same requirements will be found under the California Building Code in standard 25-2 or its CBC equivalent.

[ December 29, 2005, 01:50 PM: Message edited by: eprice ]
 
Re: 410.16 - Means of Support

There are two independent thoughts or rules in this code section. The first tells us how the grid must be installed where the grid is used to support the fixture. The second requires that the fixture be securely fastened to the grid. There is nothing in the section wording to say that this part of the rule applies only when the grid is supplying the fixture support.
Don

spelling correction

[ December 29, 2005, 02:06 PM: Message edited by: don_resqcapt19 ]
 
Re: 410.16 - Means of Support

Don,
If we read this section the same way as you, if I were to install a 4 inch octagon box suspended from the structural ceiling in the center of a 2 x 4 foot tile and mount a small light fixture from that box, my installation would be illegal, since it is hung by thread rod, and not attached to the ceiling grid.

Is that what you are saying?
 
Re: 410.16 - Means of Support

Originally posted by don_resqcapt19: There is nothing in the section wording to say that this part of the rule applies only when the grid is supplying the fixture support.
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Yes there is. The words that carry this message are the words "used to," as shown in bold capital letters in my earlier post (12:09 pm). The section speaks of grids that are "used to support luminaires (fixtures)."

If the grid does not support the fixture, then the grid has no business being discussed in the context of the NEC. No wires, no NEC.

I can't speak to eprice's discussion of building codes, as I do not have experience in that area.

{Edited to correct a mis-quoted word.}

[ December 29, 2005, 03:56 PM: Message edited by: charlie b ]
 
Re: 410.16 - Means of Support

Originally posted by jbwhite: I still assert that two ceiling wires, on on each of two aposing corners, is not supporting the fixtures. . . . If one does support the fixture independantly . . . , then I see no need for screwing the fixture to the grid.
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I agree. But this is a design consideration, not an NEC issue. If I want to just use two wires at the corners, I am free to call that "support." The NEC does not require us to screw the fixture to the grid, if it is not our intent to support the fixture from the grid.

That section is merely setting the standards for adequacy of support. The NEC thinks that "good enough support" must include connecting the grid to the walls (or other part of the building), connecting the grid pieces to each other, and screwing the fixture to the grid. That makes good sense.
 
Re: 410.16 - Means of Support

Originally posted by jbwhite:. . . if I were to install a 4 inch octagon box suspended from the structural ceiling in the center of a 2 x 4 foot tile and mount a small light fixture from that box. . . .
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I would call that "legal." The grid is not being "used to support luminaires." As soon as I start to read 410.16(C) and get to that part, I can stop reading. I don't have to read about construction of the grid, nor about attaching the fixture to the grid.
 
Re: 410.16 - Means of Support

Charlie,
Yes there is. The words that carry this message are the words "used for," as shown in bold capital letters in my earlier post (12:09 pm). The section speaks of grids that are "used for" supporting fixtures.
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I see nothing to carry that wording on to the second sentence of the rule. There are two parts, the first tells us how the grid must be installed when it is used as the fixture support. The second sentence does not have the qualifying words, "used to support luminaires", and applies to all fixtures in a suspended ceiling system.
Don
 
Re: 410.16 - Means of Support

You can stop reading midway through the first sentence. You don't have to read the rest of the first sentence, and you don't have to read the second.

But if you choose to read the second sentence, ask yourself when it mentions "securely fastened to the framing member," what "framing member" can it possibly be talking about? It has to be talking about the framing member from the first sentence. But that sentence tells you that it is discussing grids that are used to support the lights.

Put it another way. Delete the first sentence. Can we build a safe grid and lighting system, based only on the second sentence? No. Why? Because you would have a light attached firmly to a grid that is going to fall down. Conclusion? The second sentence cannot stand alone. It must be a follow-on of the requirements from the first sentence.
 
Re: 410.16 - Means of Support

I am still with Don on this one.

I do not the how "used to" support carries over.

But I do know the requirements where I work. :D
 
Re: 410.16 - Means of Support

Originally posted by iwire:But I do know the requirements where I work.
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You can always do more than the NEC requires. But I would be concerned if an Inspector tries to enforce his or her own "amendment" to the code. That appears to be the case here.
 
Re: 410.16 - Means of Support

Originally posted by charlie b:
You can always do more than the NEC requires.
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IMO I would not be doing more than the NEC requires. :)

JMO, Bob

[ December 29, 2005, 06:28 PM: Message edited by: iwire ]
 
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