Telephone Cable Specification

[JatTiw]

Dear Members,
For a project I am using 22AWG solid tinned copper, 100-pairs twisted cable for telephone distribution system in a Hazardous plant enviorment using cable trays. What other electrical charactristiccs need to be specified in order write down the specifications of this cable.

 

[peebee]

What is the hazardous classification? Class? Division?

 

[peebee]

Also, are you just running through the space or are you terminating within the space? Is your cable in conduit? Above ground or underground? Is the equipment intrinsically safe, XP, or general purpose?

 

[JatTiw]

Dear Peebee,
I am looking for electrical chractics of the cable (like resistanc, capactance & any other spec. required.
But to your question thois cable is just passing through classified area (Class1 zone-2)
& terminated in unclassified area & routed via cable tray.

 

[peebee]

If NEC applies, then NEC 501.15 would allow type TC tray cable to be used. There are no other particular requirements for the cable product specification. Capacitance and resistance are not a code issue, and would not relate to the suitability of the cable to be installed in the hazardous area, based on the application you describe.

There may be installation considerations you need to address, including sealing at the Zone 2 boundary, splicing, etc.

 

[Lewish]

The capacitance of telephone service cable is 8.2 nF/mile in the U.S., if my memory is correct.

 

[busbar]

There are likely regional variations for communications outside plant, but on the North American continent, untinned conductors are most common; having thermoset insulation (PE) versus thermoplastic (PVC).

 

[hbendillo]

It would be helpful if you could get a copy of the Telephone Distribution Design Manuals that are published by BICSI. These books are used and recognized by the Communications Industry as the standard for cable plant design. The most important parameter to consider it the cable Category. You should specify either Category 3 or Category 5 cable. Category 3 is traditionally used for telephone systems. Category 5 is used for high speed data systems. If there is any doubt about what the cable will be used for in the future, use Category 5. I do not think there is much difference in price. Specifying a Category gives the resultant capacitance, twists per inch and other cable characteristics needed for the given application. The outer jacket insulation is the next thing to consider. The jacket is rated based on the enviroment in which it is installed. Since it is in a hazardous location you may need a special insulation. Also, you probably have other considerations. I would look in the NEC to see if you were required to install the cable in conduit or take some other measure. Not sure if you are allowed to use cable tray in all types of hazardous areas. You also need to consider the length of your cable runs especially if you are using the cables for high speed data. If runs are too long the signal may be degraded to a point where you could not get you cable plan certified or worse you would have errors in data transfer.