Riser Cable Through Utility Tunnel, with Short Plenum Section 1

[Telephonist]

We have a situation we need a solution for. We're running copper distribution cable from our switchroom to a series of new buildings (one being built now, with others to follow). The cables will run in cable tray in our campus utility tunnel, so we're going to use riser cable. The tunnel system is not a plenum space, but there is a short stretch (~120 feet) of the cable path in the switchroom building that is plenum space.

For a variety of reasons, we used cable tray (basket type) through the plenum space. Now, in order to keep the cabling cost down, we're trying to avoid running the entire distance using plenum rated cable.

One option would be to use non-plenum cable in the tunnel, and splice onto plenum cable where the path enters the plenum space. But my boss is asking if anyone makes a product we can use to wrap the cable tray in the plenum space, that will allow us to run the non-plenum riser cable the whole distance.

Any ideas from this distinguished group? Thanks.

 

[Dexman]

I've read posts where techs revealed how they ran non-plenum cable through conduit inside the air space.

If that is a legit solution, and the cost isn't excessive, it might be something worth considering.

 

[Telephonist]

Conduit isn't really an option, given some of the constraints of the cable path, which is why the basket tray was used.

 

[lopes1211]

must be terminated with lightning protection at each building entry. change the cable type there.

-CL

 

[Telephonist]

Actually, that brings up another question I have, relative to building or electric codes. Since we're running the cable through the tunnel, which connects to the basement of each building, we're never actually leaving a building. We go from a concrete basement room, through a door, into another long narrow concrete basement room (the tunnel), then down a ways to another door, through which is another concrete basement room (the second building). So the question is, do the codes actually require lightning protection if the cable never leaves a structure.

In any event, we are going to install lightning protection, but as pertains to the original situation, the lightning protection on the near end is inside the switchroom, so we're not installing protectors at the tunnel entrance, which is where we would need to transition to plenum cable.

 

[SYQUEST]

You should contact the Authority Having Jurisdiction (AHJ) as to what the NEC and the fire codes dictate your requirements would be, and whether that space is really a plenum space.

Hope this helps!

....JIM....

 

[strmwalker]

Telephonist...lightning protection is not a code it is cya
cover your ass .if you think going thru a tunnel you never
leave the structure you are very much mistaking what you
are actualy doing.have you ever seen what lightning has done hitting the ground which i think is where you have your tunnel underground.i can and will eat your system
up trust me on that you need protection on both side where cable leaves the building and where it enters the building.
the cost on protection will be worth it in the the long run.


strmwalker

 

[dibthree]

I agree on both points. Being cheap will often cost your dearly in the long run. Yes use lightening protection. And bond and ground everything. It shocks me how many data centers I walk into where there is thousands and thousands of dollars of electronics in data racks and cabinets with absolutly no bonding and grounding. Even if you do not care about losing all the gear, the possible loss of human life should be enough to bond and ground. Especially when a ground strap costs about $2.

And yes change from plenum to OSP at the surge protectors. That is the easiest part.

If you do not pay to have it done the right way now it will cost you much more down the road.