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?
On Sep 29, 10:43 pm, firstname.lastname@example.org 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
Quite a difference between plain vanilla PVC and rated cable.
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!!!
On Sep 29, 5:30 pm, email@example.com wrote:
If there is romex there already, then let's hope it isn't plenum
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.
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!
remove the "not" from my address to email
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.
On Sat, 1 Oct 2011 07:42:27 -0700 (PDT), " firstname.lastname@example.org"
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
On Sat, 01 Oct 2011 12:00:27 -0500, " email@example.com"
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.
On Sat, 01 Oct 2011 15:54:57 -0400, firstname.lastname@example.org wrote:
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.
On Sat, 01 Oct 2011 17:21:18 -0500, " email@example.com"
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,
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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