NEC question: low-voltage wiring crossing 120v wiring.

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I am running network cables -- shielded, if that makes a difference -- above suspended ceiling where there is already 120V Romex wiring in places. This 120V wiring is stapled to the joists at intervals.
Is it OK for the network cables to lie on the ceiling support members, and thus beneath the Romex? Or should the network cables be above the Romex? Or should one or both be in conduit? -- more precisely, should what is now Romex be redone with individual conductors in conduit?
Perce
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On Thu, 29 Sep 2011 15:19:42 -0400, "Percival P. Cassidy"

no issue even with cat5 or cat5e non sheilded - as long as your space above the ceiling is not an air plenum - and then you just need plenum rated cat5
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On Sep 29, 5:30 pm, snipped-for-privacy@snyder.on.ca wrote:

What's the reasoning behind plenum rating a computer cable? Is there some fire-reasoning behind it or what? What's the difference between rated and non-rated cable?
R
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On Thu, 29 Sep 2011 17:07:32 -0700 (PDT), RicodJour

Fire rating. Plenum cable will not support combustion when flame is removed - will not flame on it's own - and different smoke. Non-plenum rated is not allowed in an air return.
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On Sep 29, 10:43 pm, snipped-for-privacy@snyder.on.ca wrote:

Yes, but my question was whether the OP's above-ceiling space is actually a plenum. I had assumed the question was residential, a basement and the space was not used for airflow. Granted, that's reading a lot into it, but perhaps they were bad assumptions.
Here are some interesting (but boring!) videos of the different cable ratings burning. http://www.l-com.com/multimedia/video_clips/video.aspx?ID=13100 Quite a difference between plain vanilla PVC and rated cable.
R
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On 09/30/11 11:23 am, RicodJour wrote:

You are correct: this is a residential setting, with a suspended ceiling installed in the basement.
Perce
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On Fri, 30 Sep 2011 11:36:06 -0400, "Percival P. Cassidy"

But we still don't know how the cold air returns work. If the cold air return just dumps into the ceiling, and the ceiling is open to the furnace room - and the furnace drawr return air from the furnace room - it's a plenum. Ditto if the cold air return had an opening into the basement, which is now semi-blocked by the dropped ceiling, so it is drawing return air from above the ceiling. Neither is a proper approch - but I've seen stranger!!!
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If it's a plenum that means something is pumping air through it to the rest of the building. Can you think of a better way to speed combustion and spread smoke he asked rhetorically?
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On Sep 29, 5:30 pm, snipped-for-privacy@snyder.on.ca wrote:

If there is romex there already, then let's hope it isn't plenum space.
Only in commercial buildings would I expect space above suspended ceilings to be used as air plenum (return air is drawn through it on its way back to the hvac system), and commercial building code anywhere in N.America requires power conductors to be in conduit or armored cable, and data cabling to be in either conduit (in which case, it might not need to be plenum rated) or a cable tray, the better to prevent it from collapsing into the space during a fire, blocking egress and creating a hazard for firefighters. At least that's how it was explained to me.
Single-family residential code doesn't say anything about low-voltage cabling except that you can't put it in the same boxes as 120V.
Having said that, I think laying it onto the suspended ceiling, as I understand the OP is proposing, is going to be a pain whenever someone wants to lift a panel. I'd find some clips to tack it to the joists.
I wouldn't expect simple romex runs to be an interference problem for data communications. Fluorescent ballasts, light dimmers, fan speed controls and any kind of motor or switching power supply, maybe.
Chip C Toronto
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On 9/29/2011 2:19 PM, Percival P. Cassidy wrote:

the only thing they taught us to avoid is running parallel to high current cables. But if you're using shielded cable, even that shouldn't matter. And i don't imagine any cable in a house to be high current except the range line and the line to the a/c unit. Lay away!
--
Steve Barker
remove the "not" from my address to email
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responding to http://www.homeownershub.com/maintenance/NEC-question-low-voltage-wiring-crossing-120v-wiring-664640-.htm DA wrote:

Are you concerned with EMI (electromagnetic interference) or fire safety?
For fire safety NEC wants you to stay 6+ inches away from the power cables and that should also be far enough for EMI to be negligible. That shield on the network cables is absolutely unnecessary in a residential home, but since you already go it, do not ground it on either end. I presume you won't be able to ground it correctly at the outlet end anyhow, so just let it float. It'll be useless as an EMI shield (which you don't need anyway) but might prevent some kinking and cinching.
However, if you can return the cable, I would strongly advise to do so and get a smaller diameter UTP - you'll be able to pull more cables through the same size hole and that will come handy during the install. In a home made of essentially wooden sticks (often times "engineered wooden sticks") you don't want to make holes bigger than absolutely necessary.
It may be a moot point in a wooden home, but I would always locate low voltage cables below high voltage power. If cables are the cause of the fire, it would always be the power ones, not low-voltage, and the fire would want to go up. The less burning material above it the better. But again, would probably make little difference if everything around is wood.
Good luck!
------------------------------------- /\_/\ ((@v@)) NIGHT ():::() OWL VV-VV
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On 09/30/11 12:58 pm, DA wrote:

My question was about the NEC, which is concerned with fire safety.

The shield is to eliminate interference to my amateur radio station. This was a problem with unshielded cables.

No holes have to be drilled: the network cables pass over the tops of the partition walls.
Perce
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You have a cite for that? In addition to not believing it, it's hard to see what difference 6 inches is going to make. I regularly see low voltage cables of all kinds stapled near Romex.


but
Says who? A Farraday cage is a Farraday cage whether it's grounded or not.
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On Sat, 1 Oct 2011 07:42:27 -0700 (PDT), " snipped-for-privacy@optonline.net"

I stay out of these low voltage things because reality seldom trumps urban legend but you are right. The NEC says cable jackets are "separation" and you can tywrap your CAT 5 right to the Romex as long as they are independently supported.
Being twisted pair, the CAT-5 will not be affected by the 60hz at all anyway. LAN cards reject 60 hz too.

If you are running STP, you are only supposed to ground one end of the braid but not both
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On Sat, 1 Oct 2011 07:42:27 -0700 (PDT), " snipped-for-privacy@optonline.net"

My experience has been an ungrounded sheild just becomes an antennaa

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On Sat, 01 Oct 2011 11:56:49 -0400, snipped-for-privacy@snyder.on.ca wrote:

It can, if the equipment is junk. It can also be a rather nasty current path if the "local grounds" aren't.
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On Sat, 01 Oct 2011 12:00:27 -0500, " snipped-for-privacy@att.bizzzzzzzzzzzz"

That is why you only ground one end. You are not providing a current path, just a drain for whatever transients the shield would catch.
In the case of data cabling, STP is really pretty rare and they do very well running gigabit ethernet over UTP. Most of it is just that they are a lot better at noise rejection in the adapter itself. The idea that anything generated in a 20a Romex running next to a CAT-5 is going to spike an ethernet adapter is ludicrous.
When I was in the cabling biz at IBM I set un an experiment with CAT-3 trying to break an Ethermet or a Token Ring LAN doing every urban legend bad thing anyone could think of (loops of cable over fluorescent ballasts, running next to 480v 1600a feeders, taped to the raceway, telephone in the same cable, exceeding the 300' rule, etc) Basically I couldn't break it.
What did have an effect, kinks in the cable, sloppy terminations and driving a staple through the cable. Those were handy for the second phase of the experiment, finding bugs doing TDR with a scope.
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On Sat, 01 Oct 2011 15:54:57 -0400, snipped-for-privacy@aol.com wrote:

Prezactly.
STP is used if the hardware is dirty. Over the last few decades, LAN hardware has been cleaned up to where it's not needed. STP helps the "antenna problem", above, but it shouldn't be needed anywhere.

10-baseT, 4/16MB T/R only?

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On Sat, 01 Oct 2011 17:21:18 -0500, " snipped-for-privacy@att.bizzzzzzzzzzzz"

The original installation was 16mb TR but we also tried 10/100 Ethernet and it ran clean at 100 mb doing big file transfers and looking at the logs. For the "over length" test I hooked the kludge we had up to a new 300' spool so we had that plus the other hundred foot baseband cable we were playing with and whatever was in the rack, cables etc.
The whole thing got started when someone said we were having problems because the router (in a rack) was backed up to the equipment room wall where they had that 1600a service.
The router was bad.
I hooked up the spool, just for playing with TDR to get a little more time down the wire but I had to try it. ;-)
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On Sat, 01 Oct 2011 19:59:33 -0400, snipped-for-privacy@aol.com wrote:

I'm somewhat surprised 100BaseT worked over CAT-3.

Hate it when that happens.

TDRs are great tools. Too bad they're so rare (I suppose the people who know how to use one are even more rare).
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