Put quality into Cat-5 installation

Use the right tools and inspect the process at every step for fast, clean data transfer.

Today’s computer systems require fast, efficient data sharing and high-speed Internet access. To meet these burgeoning communications needs, offices must upgrade their data communication systems.

The Electronics Industry Alliance (EIA) and its subgroup Telecommunications Industry Association (TIA) have developed the ANSI-approved network standard, EIA/TIA 568A. This standard defines basic cable and outlet performance for Category (Cat)-3, -4 and -5 and fiber-optic systems.

The EIA/TIA 568A standard is very specific about how cabling should be installed to minimize outside interference from affecting data quality. It starts at specification and ends with testing and certifying the network.

“The key to successful datacom installation is attention to detail,” says Tom Luebke, senior project engineer at Gardner Bender. He shares these datacom installation best practices.

Proper cable installation
The first opportunity for network problems comes with cable pulling. “Look at the quality of your trays and make sure they are assembled properly,” he says. Poorly designed trays or ones assembled incorrectly can nick cable as it is pulled. “Look at the pulling force rating listed on the cable box. Don’t go over that amount, or you could damage the cable,” he says.

Install cable with gradual bends at corners. Kinks or sharp bends can create line interference.

Use staples or fasteners that conform to the cable’s shape. “Don’t nail the cable down so tightly that it crimps the wires inside,” he says.

Mark cables before you begin pulling. Use a tone tracer to identify cables that lost their marker during installation.

Although the twisted pair design in Cat-5 cabling helps shield itself from outside electromagnetic forces, it’s best to keep datacom cable away from electrical runs.

Luebke recommends testing network drops after installation, then again after drywallers or ceiling installers have finished their work.

Cable termination tips
“Installing terminators at cable ends is an exacting process. Any short cuts or sloppy work can result in poor connections that can cause network problems,” he says. Luebke shares best-practice methods for cable termination:

1. Cut cable squarely
Don’t make the cut with your pocket knife. You will likely end up with various twisted-pair wire lengths. “This can cause line noise and slow network speed,” he says.

Quality cutters make nice, clean cuts without nicking the twisted pair wires.

2. Remove 1/2" of sheathing
Insert the cable 1/2" into the sheathing tool, then rotate the tool one turn to cut the outside insulation. On Cat-5 cabling, this will reveal four twisted pairs of wire as well as some strands of thread that help strengthen the cable. Cut the threads back to the sheathing. Inspect for cut or nicked wires. If any are damaged, cut the wires off squarely and start over.

The 1/2" length is critical. It allows the installer to separate the twisted pairs enough so they can be inserted into the RJ-45 connector without affecting the cable’s ability to transmit data.

3. Match twisted pairs to network wiring scheme
The system designer should identify whether the network uses the 568A or 568B wiring scheme, which dictates pin assignment in the connectors.

The only difference between 568A and 568B schemes is the order in which leads are inserted into the termination plugs.

“It’s important to identify the wiring scheme used in the facility and continue with it,” says Luebke. Make sure new patch panels and cords match the facility’s scheme.

4. Crimp correctly
Once you seat the pairs correctly, use a high-quality crimper designed for use with RJ-45 male connectors. “This is where having the wires cut squarely helps the pins seat correctly. Before you crimp, check once again to assure the wires are inserted in the proper order. Then use the crimper to uniformly seat the brass spikes of the connector into the wires,” he says.

The process is similar with female RJ-45 connectors. Make sure the wires are inserted uniformly and in the correct order, then use a punch-down tool to fasten each wire into place. “Set the punch-down force to make sure you get a good connection and a good cut of excess wire,” he says.

5. Test the connection
A tone tracer can identify lines, but it’s not the tool to test network cable quality. You need to use a test set that can detect over-voltage, open pair, shorted pair, crossed pair, split pair, reversed pair, transposed pair and Near-End Cross-Talk (NeXT) problems.

“These tools can be used to test cables before the technician comes in to certify the system,” says Luebke.

Published in the September/October 2001 issue of Contractor Tools and Supplies magazine.

 back to top