Supporting Category 6 cable

Q: I am supporting Category 6 cables between spans with a cross-member made of metal. How far apart should I put the members to get the correct droop in the cables?

May 1st, 1999

Q: I am supporting Category 6 cables between spans with a cross-member made of metal. How far apart should I put the members to get the correct droop in the cables?

Tim Brooks

Sentry Equipment & Erectors Inc.

Forest, VA

A: The TIA/EIA-569a Commercial Building Standard for Telecommunications Pathways and Spaces standardizes specific design and construction practices in support of telecommunications media and equipment within and between primarily commercial buildings. Section 4.6.5 of the standard states: "Where zone conduit or cable tray is not available in a suspended ceiling space, and where telecommunications cables are allowed to be placed in the ceiling, adequate open-top supports, located on 48- to 60-inch centers, shall be provided."

But spacing is not the only issue: Make sure that the method of attachment that you specify will carry the weight of the maximum quantity of cables (not just what you plan to install initially) that can be installed in the hanger. I usually specify not to exceed 48-inch centers, with an attachment method that is rated to carry at least the weight, and preferably two times the weight, of the maximum fill of the hanger. It may sound like overkill, but when you lose a support in the middle of a run, the cable weight will be transferred to the two neighboring supports, and if they don`t hold, your problems increase exponentially.

Also consider that installing cables on the edge of the metal cross-member may change the cable geometry and affect the performance of the cabling. Installing the cross-member with a flat side up to support the cables can minimize this change.

Donna Ballast is a communications analyst at the University of Texas at Austin and a BICSI registered communications distribution designer (RCDD). Questions can be sent to her at Cabling Installation & Maintenance or at PO Drawer 7580, the University of Texas, Austin, TX 78713; tel: (512) 471-0112, fax: (512) 471-8883, e-mail: ballast@utexas.edu.

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