Low Voltage Installations

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MikeM31$

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Location
Duluth, MN
We are a hospital currently working on an above ceiling Permit program for fire stopping penetrations. As part of this program, we want to educate the low voltage wiring folks so they stop hanging wire from every conceivable thing, including the sprinkler pipes. Is there a quick reference sheet somewhere that gives a brief summary of the installation requirements that we can hand them that lists the do's and don'ts short of handing them the entire first 4 chapters of the NEC 2014 codebook? Any thoughts/ideas/checklists would be appreciated. Thanks. Mike
 

JFletcher

Senior Member
Location
Williamsburg, VA
We are a hospital currently working on an above ceiling Permit program for fire stopping penetrations. As part of this program, we want to educate the low voltage wiring folks so they stop hanging wire from every conceivable thing, including the sprinkler pipes. Is there a quick reference sheet somewhere that gives a brief summary of the installation requirements that we can hand them that lists the do's and don'ts short of handing them the entire first 4 chapters of the NEC 2014 codebook? Any thoughts/ideas/checklists would be appreciated. Thanks. Mike

300.4(D) and 300.11 is directly referenced in chapter 8 under 800.24. Cant be supported by the ceiling grid. Sprinkler pipes are off limits via NFPA 13. Strapping it to ENT is a no go as well (you could use the uni/superstrut if there's room, but I find all-thread tears up cable and I'd rather put in my own hangers). Im sure there is a plumbing code re: water/drain lines not being meant to support anything either.

Make sure there is not more than 360* of bend in any conduit you're pulling cable thru.

I never did a hospital but I did do hotels; we installed our own hangers at 5' intervals (EIA/TIA spec). Pull a string down a hall, and put hangers on that string line. Use more/bigger hangers the closer you get to the IDF/MDF. Perfectly straight gravy pulls even with 20+ cables rigged, no one gets bent over comm wire on unassociated equipment. No sliced up cables. The extra time it takes to put up your own hangers is massively offset by how much faster you can pull cable w/o problems.

Dont pull cables like banjo strings - nice sweeps going into conduits, leave a small service loop there (in the halls). iirc, comm cable in larger bundles has some specific firestop requirements - we just used Hilti FS-1 for pretty much everything. Expensive, but digging out improper firestop and redoing it is more expensive. We used EMT sleeves with bushings on both ends when penetrating any wall (most walls in hotels are fire rated).

There isnt really a quick reference you seek; the BICSI Telecom Distribution Methods Manual (as of 2003) is a 2 volume set, each one twice as thick as the 2008 NEC.

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imho learning this is not optional for a low voltage man doing commercial work where life and safety of a lot of people come into effect. Proper firetopping is as much of a trade as any other; doing it correctly requires more than a cheat sheet.

I personally prefer using D-Rings on walls mounted every 3rd 16"OC stud or 2nd 24"OC stud (4' support) and on concrete, Hilti clips that get shot in with a DX351 (every 5'). Here's a link to the Hilti products:

https://www.us.hilti.com/direct-fastening/electrical-&-mechanical-fastenings/r1683

I also found reels or rabbit-pull boxes much easier to work with than reel-in-box, especially when pulling a lot of cables at once. The drag on reel-in box is hideous, and most arent a true spool, so when there is a problem with payout, you have a big mess on your hands.

tl;dr: install your own cable supports, everyone is happy. and welcome to the forum!
 
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JFletcher

Senior Member
Location
Williamsburg, VA
What article in chapter 8 applies to IT cables?

800.24, 820.24, 830.24 all reference 300.4(D) and 300.11 (2008 NEC). Information Technology I believe (I may be wrong) falls under Article 800. IT room falls under Article 645, and 645.7----> 300.21, which is the wonderful world of firestopping.
 
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