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#83055 - 01/06/03 11:13 PM Suspended Ceiling  
Boomer  Offline
Junior Member
Joined: Feb 2002
Posts: 5
Is it a good wiring practice in a commercial building to come thru a hole in the dry-wall ceiling with romex wire and drop 8" to a lay-in fluorescent fixture or recessed fixture in a suspended ceiling? Should there be a box at the hole in the dry-wall ceiling? Can the romex be unspported? Can the romex run into the fluorescent fixture with out a box? Thanks for any advice, I use a box with a whip. Boomer


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#83056 - 01/07/03 12:41 AM Re: Suspended Ceiling  
Nick  Offline
Member
Joined: Aug 2001
Posts: 599
Riverside, CA
I don't have a code book with me today but isn't it a violation to run romex above a suspended ceiling in a comercial ocupancy now?


#83057 - 01/07/03 07:57 AM Re: Suspended Ceiling  
spyder  Offline
Member
Joined: Oct 2002
Posts: 210
Massachusetts
I think if the occupancy rate is under 100 people you are permitted to use romex as a wiring method. Using it in the suspended ceiling could be a different story. Many times the area above the suspended ceiling is considered a plenum. Romex is not permitted for use in a plenum.


#83058 - 01/07/03 08:27 AM Re: Suspended Ceiling  
Redsy  Offline
Member
Joined: Mar 2001
Posts: 2,056
Bucks County PA
Boomer, Nick,

334.12 prohibits open runs of NM cable in suspended ceilings in other than one & two-family dwellings.
(open runs are considered those which do not have additional physical protection)


#83059 - 01/07/03 09:43 PM Re: Suspended Ceiling  
HotLine1  Offline


Member
Joined: Apr 2002
Posts: 6,853
Brick, NJ USA
If the drop ceiling is "plenum", NMC is not allowed. If you are penetrating sheetrock in a fire rated ceiling you cannot "punch thru"; the "hole" must be sealed to maintain fire rating.

Wiring (two cables) into a troffer fixture is acceptable. Boxes and whips are acceptable.

Any cabling within a drop ceiling has to be supported independently of the drop ceiling grid. There is a max. length that can be unsupported between fixtures, I believe it is 5', but I'm not positive. (Please read the articles in the NEC)

Also, all low voltage wiring in a plenum ceiling must be "plenum rated", and recently, another AHJ found an article requiring "Plenum Rated" tie wraps.

John


John

#83060 - 01/08/03 09:47 PM Re: Suspended Ceiling  
Nick  Offline
Member
Joined: Aug 2001
Posts: 599
Riverside, CA
Hmm, Plenum rated tie wraps. I had to use a bunch of them recently. 1/8" X about 10" are a mear $1.00 each! [Linked Image]


#83061 - 01/09/03 06:02 PM Re: Suspended Ceiling  
iwire  Offline
Moderator
Joined: Jan 2003
Posts: 4,391
North Attleboro, MA USA
Nick,
We use bailing wire instead of tie wraps in most ceilings, much cheaper I can usually get it from the guys tying rebar.

But for NMC I guess that would not be so good.

I usually run MC and the inspectors seem to like the metal ties.


Bob Badger
Construction & Maintenance Electrician
Massachusetts

#83062 - 01/09/03 07:55 PM Re: Suspended Ceiling  
HotLine1  Offline


Member
Joined: Apr 2002
Posts: 6,853
Brick, NJ USA
Iwire:
Not to be a pain in the butt...is the tie wire that you use listed for use as a support for MC cable???

THe plenum tie wraps are mostly used for LV cables (yes, plenum rated LV cable). The MC is usually supported with Caddy clips to seperate drop wires that are "secured" to the ceiling grid with more Caddy clips. All of the above items are listed for the usage.
I don't have the Caddy book on hand right now.
John


John

#83063 - 01/09/03 08:09 PM Re: Suspended Ceiling  
iwire  Offline
Moderator
Joined: Jan 2003
Posts: 4,391
North Attleboro, MA USA
HotLine1, not a pain in the butt.
Damn good question I would have to say no.

That said, I had inspector in Mass. tell me that plastic tie wraps are not listed for support of MC and that soon I may not be able to use them at all, (I do not know the truth of this) his reasoning seemed to be they melt early in a fire and drop stuff down onto firefighters.

This being Mass, where we must tie lights independently from ceiling I can certainly believe this.

I have never been shot down for it.

As far as the caddy clips we use those too but the tie wire is faster, cheaper most times, you carry a roll of tie wire instead of a variety of caddy products.

We try hard to follow the building structure
so we do not have horizontal runs down near the grid when we do its Caddy clips

Down the metal studs we end up using Caddy

Bob




[This message has been edited by iwire (edited 01-09-2003).]


Bob Badger
Construction & Maintenance Electrician
Massachusetts


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