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#25128 - 04/26/03 06:45 AM Support M/C
Obsaleet Offline
Member
Registered: 04/05/03
Posts: 362
Loc: Pa
How do you feel about using tie wraps to hold M/C cable above a drop ceiling? How about in a Plemun?


Ob
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#25129 - 04/26/03 08:21 PM Re: Support M/C
golf junkie Offline
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Registered: 04/22/01
Posts: 507
Loc: York, NE
It's fine with me as long as the AHJ will allow it. Some will some won't.

GJ
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#25130 - 04/27/03 07:40 AM Re: Support M/C
NJwirenut Offline
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Registered: 09/15/01
Posts: 806
Loc: Bergen County, NJ
In a plenum, the AHJ will (should) require plenum rated cable ties.
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#25131 - 04/27/03 07:52 AM Re: Support M/C
Obsaleet Offline
Member
Registered: 04/05/03
Posts: 362
Loc: Pa
Yes Nj I thought about that. I have yet see them plenum rated. I have been using the batt ears. I am trying to get a opinion about this. My other thought is that the perpose of these things is to keep the cable off the firepeople. Tiewraps aren't going to cut it.
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#25132 - 04/27/03 09:22 AM Re: Support M/C
resqcapt19 Offline
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Registered: 11/10/00
Posts: 2148
Loc: IL
Obsaleet,
Even if the wire ties fail in the heat of a fire, the cable will not fall on the firefighters unless the grid itself has also failed.
don
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#25133 - 04/27/03 09:55 AM Re: Support M/C
Cindy Offline
Member
Registered: 06/23/01
Posts: 196
Loc: PDX, OR, US
all of 300.11 talks about support 'wires' and 300.11a1, fire-rated, says to tag the slack wires...

so i thot the idea of independent supports was to allow the electrical equipment to stay up there if the tiles and grid are dropped. limited energy guys use ties up there all the time, plenum rated if plenums, but we use the 12gage aircraft cable for our line voltage to support everything. and even though the MC section says you dont need support for the whips, we use them based on 300.11A, last sentence.

do fireguys cut the grid loose to drop it? is that the reason for tagging them?
anyway, my vote is to use the slack wires vs tie wraps
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#25134 - 04/27/03 11:52 AM Re: Support M/C
Obsaleet Offline
Member
Registered: 04/05/03
Posts: 362
Loc: Pa
Cindy,
I was told this in 2 code classes. "when the fire people comeinto the building they use there poles to pull down the ceiling".
I have been told by firemen that they don't do this in practice. At least not in our local.
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#25135 - 04/27/03 01:26 PM Re: Support M/C
NJwirenut Offline
Member
Registered: 09/15/01
Posts: 806
Loc: Bergen County, NJ
Plenum rated cable ties are widely available from the usual suppliers (Thomas and Betts, Panduit, Tyton, etc.). A good deal more expensive than the usual nylon ones, though.

One source:
http://www.connectworld.net/bulkcable/bundle_secure11.html
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#25136 - 04/28/03 11:24 AM Re: Support M/C
kale Offline
Member
Registered: 11/08/02
Posts: 174
You can usually find Stainless Steel cable ties for less money than the plenum rated plastic versions.

The stainless ones would satisfy the requirements listed here.

BTW, Panduit's plenum ones are purple in color to help you recognize them.
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#25137 - 04/28/03 12:39 PM Re: Support M/C
resqcapt19 Offline
Member
Registered: 11/10/00
Posts: 2148
Loc: IL
Firefighters will often "open" ceiling to check for fire spread or to apply water. With a grid ceiling they will not attempt to pull the grid down, but only pull down the tiles. The grid falling around them creates the very real possibility of entanglement and is not something that would be done intentionally.
The reason for the "identified" supports in a fire rated ceiling has to do with the rating of the ceiling. There are very specific construction rules for fire rated ceiling assemblies. The only reason for the identification of the electrical support wires is to make it easier for the building/ fire inspector to verify the fire rated ceiling assembly has been correctly constructed. The fire rated ceiling assembly design does not include the support of anything other than the ceiling itself. The support of electrical conduits or cables using the fire rated ceiling support wires would void the fire rating of the ceiling.
Don
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