7 Biggest Cable Management Mistakes
Poor rack planning, too much pull force and not segregating cables are among the biggest mistakes made when deploying cables.
Whether the project is a simple mounting of a flat-panel TV or a whole-house integration system with an expansive utility room, here are the seven biggest mistakes integrators make when deploying cables and how to avoid them.
1. Bend Radii Too Tight
All twisted pair cable is manufactured as “loose-fill,” meaning there has to be a slight air space inside the sheathing. This reduces mutual capacitance, which is meant to reduce data packet errors.
Running cable with very tight bend radii will increase errors. There is no universal standard for every type of cable, but a 1.5-inch to 2-inch bend radius is a good guideline to follow, even though some Category cable can take a 1-inch bend radius. Coax cables are more tolerant, but should not be kinked. For fiber optics, the rule of thumb is a bend between 15 to 20 times the fiber diameter, which will result in a bend radius well above 1 inch.
2. Pull Ties Too Tight
The same increase in data packet errors can occur by cinching down pull ties too tightly. Moreover, if cable ties are placed at even increments along the coax run in a high-density installation, it can cause standing waves.
3. Too Much Pull Force
Cables should not have any more than 25 pounds of pull force exerted against them or they will distort or break. Copper cables have a much higher tensile strength (49 pounds) than aluminum-based cables (25 pounds). A 2-plenum fiber strand has 100 pounds of tensile strength, but that level of pull is unadvised.
4. Untwisting Too Far at Connector
Every technician does it: he untwists the cable back an inch or so from the binding post so the connection can be made more easily. Unfortunately, that bad habit creates near-end crosstalk, or NEXT. The twist in a pair should remain right up to the connector. Using optical fiber cable for the final connection is one way to avoid this.
5. Poor Rack Planning
Is the cable descending from above down into the rack or enclosure or ascending from below? It’s an important consideration when determining which enclosure to select. Integrators need to use enclosure with either removable panels or ones that are specifically designed to accept the cable from the top, bottom or both.
Middle Atlantic racks include about 3 inches of space in the bottom of the enclosure to accept large bundles of cable before reaching the rack space area. Riser bases can provide an additional 2.5 inches of clearance off the floor.
6. Not Segregating Cables
AC power cables and speaker wires should never be run in parallel in close proximity (within 2 inches) to low-voltage data cabling, unless the wires are twisted. Also, AC power cables and speaker cables should be separated.
7. Bundling Too Thickly
If the bundle of cables is less than three, there shouldn’t be a concern. But the National Electrical Code has guidelines for adjusting the total current rating, or ampacity, when bundling four or more cables together for runs longer than two feet. For example, if you bundle four to six current-carrying conductors together, ampacity should be limited to 80 percent of total current rating. The scale moves all way to 41 or more cables in a single bundle, which calls for adjusting ampacity to 35 percent of total capacity.
For more cable management tips, check out this free white paper from Middle Atlantic.
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