Backbone Pathways | TIA-569-B

Backbone pathways provide paths for backbone cabling between the equipment room, telecommunications rooms, main-terminal space, and entrance facility. The TIA suggests in TIA-569-B that the telecommunications rooms be stacked on top of one another from floor to floor so that cables can be routed straight up through a riser. They also recommend pathway diversity and redundancy. ANSI/TIA-568-C defines a few types of backbone pathways:

Ceiling pathways These pathways allow the cable to be run loosely through the ceiling space.

Conduit pathways Conduit pathways have the cable installed in a metallic or plastic conduit.

Tray pathways These are the same types of trays used for horizontal cabling.

KEY TERM: sleeves, slots, and cores

Sleeves are circular openings that are cut in walls, ceilings, and floors; a slot is the same but rectangular in shape. A coreis a circular hole that is cut in a floor or ceiling and is used to access the floor above or below. Cores, slots, and sleeves cut through a floor, ceiling, or wall designed as a firestopping wall must have firestopping material inserted in the hole after the cable is installed through it.

Some points to consider when designing backbone pathways include the following:

• Intercloset conduit must be 78(3) trade size (3″ or 78 mm sleeve).
• Backbone conduit must be 103(4) trade size (4″ or 103 mm sleeve).
• Firestopping material must be installed where a backbone cable penetrates a firewall (a wall designed to stop or hinder fire).
• Trays, conduits, sleeves, and slots need to penetrate at least 1″ (25 mm) into telecommunication rooms and equipment rooms.
• Backbone cables should be grounded per local code, the NEC, and ANSI/TIA-607-B.
• Backbone pathways should be dry and not susceptible to water penetration.

Warning

Devices such as cable trays, conduit, and hangers must meet requirements of the NEC with regard to their placement. For example, flexible-metal conduit is not allowed in plenum spaces except under restricted circumstances.