cat5e OK in shielded conduit near electric?

[rrick]

I am re-doing a room and I would like to run several cat5e cables horizontally along the base of the walls. Unfortunately, this would bring them parallel to (and just a couple inches away from) the 120V electrical wiring for about 50 feet. My plan is to put the cat5e cables inside a grounded shielded conduit. Does anyone know whether this would adequately prevent interference from the electrical wiring? Is there any other reason why I shouldn't do it this way?

[FYI: The reason FOR doing this is to make it easy to install new communication outlets in the future; just make as small hole at any point in the room and the conduit will be right there. (Of course I could have the same effect if I ran the cat5e farther from the electric, like a few feet up the wall, but I want the communication outlets to be at the same height on the wall as the electrical outlets. Plus, I figure installing the conduit will allow easy future installation of additional coax, cat8, fiber optic or whatever else might develop in the future.)]

[johnwill]

You can either do that or use shielded CAT5e/CAT6 cable. It should work fine. I have a cable running right next to a 110VAC line for about 20 feet, never been an issue.

[Cellus]

For a segment length of 50 feet, I would consider shielding the cabling. Twisted Pair wiring and other Layer 1 aspects, such as signal algorithms, help defend dagainst EMI in UTP, but it only goes so far. Using STP or having a grounded shielded cable conduit might be a good idea, especially in the future if you intend to push the cabling into the gigabit+ range. If you intend to be having several runs of cabling with that segment length that close to EMI, you probably do not want to use one of those fat UTP bundles as the interference coupled with crosstalk would be pretty high - use individual cables instead.

[rrick]

Thanks johnwill, and thanks Cellus. Cellus- I am planning to use 8-wire cat5e cable. However, I might try to get two ethernet connections out of one cable; do you think this is pushing my luck?

On a related topic, one thing I hadn't realized during my previous post is that the hole diameter that I can safely drill into the studs without weakening them is pretty small- only 7/8 inch. Obviously I can't fit very many cables into a shielded conduit whose outside diameter is smaller than 7/8 inch! My current plan therefore is to use grounded steel tubing instead of flexible conduit (because the walls of the tubing are thinner than the shielded flexible conduit). This should allow a 5/8 inch minimum interior diameter. I figure I can probably fit three 8-wire cables into such a conduit; what do you think?

[johnwill]

I'd just run two cables, the cost is the labor for installation, and it's as easy to pull two as it is to pull one. Any conduit, even tinfoil, will do the trick, so that should work fine. As always, check any building codes to see what they say about the planned technique.

[Cellus]

Originally Posted by rrick

...However, I might try to get two ethernet connections out of one cable; do you think this is pushing my luck?...

While it is very much possible to run two 10/100mbit connections over a single CAT5e cable, you won't be able to run two gigabit connections, which can limit the expansion potential of the cables you will be installing. It is also not a good idea to do so if EMI may be an issue, as the potential for interference and crosstalk increases.

Oh and as John said, check your building codes. Things have changed over the years.

You can find a few handy Do's and Don'ts in CAT5e installation here (scroll down about 1/4 of the page to see the table).

[rrick]

Thanks for the info and for the helpful link! At this point it looks like I'll bring the cables into the room via 1" EMT in the stud bay, then around the room in 1/2" EMT(s) hidden behind the baseboard (NOT drilled into the studs as posted earlier). I'll cut across corners by ducking into the joist bay with a U-shaped piece of 1" EMT spanning diagonally between bottom plates of adjacent walls. The cables will leave the conduits in order to more easily transfer between stud bay and baseboard, but I'll connect the different conduits electrically using grounding wire and I'll cover the cables with aluminum foil in the places where they go between conduits. Could change before it happens, but that's my plan for now!

[johnwill]

I think that's more than sufficient. Like I said, I just pull them through the ceiling, no shielding involved. I've see large offices wired the same way, and there was never an issue. There's nothing wrong with being conservative, I'm sure you'll have no issues.

[Cellus]

Originally Posted by johnwill

...Like I said, I just pull them through the ceiling, no shielding involved. I've see large offices wired the same way, and there was never an issue...

That's usually the "standard" and is fairly harmless unless you are running it past something particularly nasty EMI-wise, like a generator, elevator, or heavy machinery of some sort. Certainly makes it easier to get your hands on.