sundance-communications.com/forum Forums Wiring - Telecom Carriers - Trunks & Services Cabling Telephones Systems Wiring underground telephone cabling between 2 buildings

I have a customer whom I will be installing a new telephone system for in the near future. The KSU will be located in one building and we are looking at running a 25 pair cable between the buildings to push telephone service from the KSU. We are most likely going to lay conduit in a trench and pull through that. My question is since it is going to be totally enclosed within the pipe can one use regular 25pair cable or should outdoor or direct burial cable still be used?

I'll let the experts pipe in, but the short answer is that underground pipe will eventually get wet and that regular indoor cable is not sufficient.

We never use indoor cable for any outdoor work....with that said, we recently did work at a site that had a 25 pair indoor cable ran as an outdoor aerial cable....and it has been working more or less OK for 20 years (or so they say).

But if we were quoting the job it would be outdoor/direct burial cable in the pipe (we do not run pipe or trench).

Steve

Steve's client might have got away with using interior cable in an exterior AERIAL environment, but it will definitely never last very long in an underground conduit.

Whether aerial or buried, use protection!

Do it right or pay the price later, your choice.

I just completed a similar job. I put in two, 3" schedule 40 PVC tubes. One for service, one spare. The distance is about 225 feet, with a total of 180 degrees of turns. They are 3 feet down, and 2 feet below them are two electrical conduits, one for 200 amp service, and one spare.

(I'm a big fan of over-engineering and redundancy, having been taught those things by Mother Bell.)

I pulled (2) 12-pair, 24 gauge filled telephone cables, (3) filled Cat5e data cables, (1) filled RG 11 coax and an optical fiber cable provided by the cable company for a town government TV uplink.

It all fit in one pipe, and I have one empty one with a pull rope ready to go if we need it in the future. I used all filled cables, even though they were in a pipe, because condensation happens and even the best glued joints will leak after a while.

I installed primary and secondary protection on all the pairs. Like the man said, do it right the first time, and you'll never worry.

Indoor cable will work but won't last long, every conduit I have worked on fills with water every time. It would be prudent to use outside rated cable and if I was doing it I would run a 50 Pair Cable terminated on 1A bix on both ends.
Tie Line
A good example I ran indoor cat5 to one of my out door payphones about a year later the phone booth got run down (backed over) by a City of Calgary truck on vidio servalance at a gas station. LOL, he reported it. I had to replace the cable, it was one year old. It was starting to rot and when I skinned it! water was on the inside of the cable, I now use only outside rated cable for out side use. Also if their is no power at the phone booth I run low voltage power 26volts I believe (but will double check)
This is used to charge the battery in the phone and run the Digital Display it will work up to 400 feet... The power uses the brown pair and the phone uses the blue pair. The other two pairs are spares

like everyone else said..there is no such thing as water tight....

now..how many phones and what is the distance? you might want to thing 50 pair and fiber for network?

Just to be clear - we did not do that aerial install, that was long before the client was ours! Not sure who got away with putting indoor cable in that environment (and how it lasted so long without major lightning hits).

Steve

Because it will be in conduit, you can use standard air-core (ALPETH) cable rather than icky-pic if you prefer. The jacket on this cable is air- and watertight as long as it isn't damaged during installation. Remember that if you elect to use icky-pic, you can't just punch it down on blocks. It must be transitioned over to air-core cable in a UL listed splice closure or BET.

Doesn't that vary by location, Ed?
Last I heard, we could run it into a building interior up to 50 feet.

The plant cable can come 50 feet into a building, but you still have to transition to air core cable to punch it down.

Exactly, Bill. Many filling compounds in cable are flammable. Most manufacturers have abandoned petroleum-based waterproofing compounds, but since we never know where cable is manufactured anymore, we have to assume that the filling truly is 'grease'. A filled cable punched down in an exposed environment is the equivalent of a leaking oil line.

Zane, please don't think that I'm belittling you or any other viewers of this thread. I think that you've raised a valid question that warrants a detailed answer. In the United States, the National Electrical code mandates most installation standards with regard to wiring standards of just about any type. On that note, we also have to keep in mind that most enforcement of NEC standards is performed by the local authorities. In most cases, these agencies' resources are limited, so they can't afford to hire inspectors who really know what they are doing. It is up to us as contractors to do what is right. Just like the plenum vs: non-plenum cabling requirements. Most inspectors in these parts focus more upon things like firewall penetrations, etc. I know for a fact that most don't even look to see if the correct cable has been used.

Back on topic: Who in the heck would want to punch down a filled cable on a block? Wipe the icky-pick from the pairs all that you want, but it will keep coming back. That is the purpose of it's design. It will ooze out of the cable core for decades. Every time that you so much as punch down a jumper, you'll be wiping your fingers on your pants.

Cable designed to be directly-buried should be just that: Buried directly. It doesn't belong indoors under any circumstances, it isn't necessary in underground conduits or in the air unless the installer just doesn't understand the difference between outside plant and inside wiring standards.

OSP cable is limited to 50 feet within a building for a good reason: The jacket is made from Polyethylene. So is the insulation on the individual pairs. This material is high-density and therefore allows 'thinner' tolerances, resulting in 'thinner' cables. When pulling massive cables in ducts, reduced sizes make a huge difference.

Those of us in the interconnect business consider a few hundred pairs to be a big deal. There is a huge difference when a telco is trying to squeeze a 2,700 pair cable into a 90-year old duct between manholes. These are two truly different and unique industries, comparable to the IT/interconnect impasse.

One of the independent telcos (GTE) in my area often allowed filled cable to be installed in an aerial environment. While they don't do it now since they became Verizon, they still have plenty of buried filled cables directly entering aerial splice closures. When it is hot outside, you should see the goo dripping out of them. It is nasty.

It is really quite simple. Just terminate the OSP filled cable using a listed BET that has a legal splice compartment where the flammability issue has been addressed.

Zane, I'm sorry that you made the mistake of asking me for the time and I told you how to build a watch, but I just felt that you had asked a legitimate question that warranted a detailed answer.

Ed,

I never complain when someone teaches me something new. I don't have much background in outdoor plant. I have to tell you that I have seen more direct buried cables punched down to 66 block (most lightning) than I have transistioned. Telco is always that way, but now that I know what to look for, I bet there is a lot of it.

You can install any type of cable and it won't matter...until the Inspector RED TAGS your work.

Do it right the first time.