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I realize this is a Fine Homebuilding discussion, but I figure there are some of you out there who would know commercial code about whether low-voltage wiring can be run in stud/rafter/joist bays without conduit. I understand that the new codes have finally included low-voltage, where before they ignored it. This isn’t open-plenum work, so it’s not that issue, but I don’t know why they have decided to start hocking contractors about their l.v. wiring….unless, I suppose, it’s another permit you have to pull (and pay for).
Thanks,
-Ben
Replies
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You probably still can run low voltage without conduit, but with the changes being made almost daily in technology, a conduit system will be much more flexible. The trend today is to use ENT (electrical nonmetalic tubing) and plastic boxes for low voltage. ENT is corrigated blue plastic that is somewhat flexible.
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Ben:
I'm not aware of any code that prevents the installation of straight telcomm/datacomm wiring in joist/stud bays. The real meat of the issue is the attainment of specific performance thresholds (e.g. 100 Mbits/sec). Category 5 is the bare minimum for today's computer geeks. Cat 7 and more are on the launching pad. There are very specific guidelines for proximity of the cables to potential noise sources such as fluorescent lighting, motors, and raw AC power. There are also guidelines for the radius of the cable bends and the like. Conduit sometimes helps in noise reduction... and it sometimes CAUSES noise!
As you can tell, there's lots of variables that can effect the performance of in-house datacomm wiring. Now, let's get practical! It makes good sense to keep such wiring a reasonable distance from the AC (18-24inches). Don't do sharp corners -- radius all turns. Pull home runs to a single punch down/interconnect point. Use good materials -- wire, jacks, interface panels. I'd use PVC conduit before metal -- noise introduction is minimized. EMT and rigid conduit can easily introduce noise to datacomm sets if they're improperly located and/or grounded.
Finally -- don't get too anal! The technology is changing so rapidly that all will be different in a matter of a few years. Prudence and quality materials will ensure that you're not left behind.
Good luck,
TPB
*In our commercial construction and tenant improvement projects, it's pretty well accepted that the rule to follow is to run phone and comm wire at 6" away from AC, when running parallel. And when crossing, run at 90 deg. perpendicular. With this method we've run miles of each in office buildings, utilizing hundreds of new and old generation equip., digital and analog,....no problems, Also no comments from inspectors.
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Leviton training manual says for CAT5 and RG6 run at least 2" away from romex AC wires running parallel, and cross at 90 degrees.
Steve
*I hope that's a typo...I've always tried for 36".In commercial I've run it in conduit even though not required. The main reason is that if I do the initial installation I'm usually the first call when it's time to upgrade. With the conduit in, rewiring is a breeze. Fast job, high margin.
*Hi Mongo,Here's the chart. The class I took on doing this stuff just said don't run it in the same holes as the romex, drill another one at least a couple inches away.Steve
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I realize this is a Fine Homebuilding discussion, but I figure there are some of you out there who would know commercial code about whether low-voltage wiring can be run in stud/rafter/joist bays without conduit. I understand that the new codes have finally included low-voltage, where before they ignored it. This isn't open-plenum work, so it's not that issue, but I don't know why they have decided to start hocking contractors about their l.v. wiring....unless, I suppose, it's another permit you have to pull (and pay for).
Thanks,
-Ben