Standards published by the International Organization for Standardization (ISO) and the International Electrotechnical Commission (IEC) also provide guidelines for maintaining a high level of cable performance. In
addition, there are federal, state and local guidelines that regulate cabling. As a whole, these standards provide guidelines that reduce long-term building operation costs, lead to better infrastructure and are adaptable to changes.

Taking Stock of Potential Concerns Outside the Rack

Today’s electronic systems wiring includes various types of cable such as voice, data, video, audio, security and control. Cables can be unshielded twisted pair (UTP), shielded twisted pair (STP or screened cable), coax or fiber. Additionally, more devices are being controlled and monitored via Ethernet nodes. Along with the types of various cables, consideration must be taken into account for the cable structure and purpose. These might include backbone cabling or horizontal cabling for structure and their purpose might be for telecommunications rooms, equipment rooms or equipment racks.

While cable performance is dependent on the physical properties of the cable, managing these cables outside the rack can create interesting challenges for the designer and installer. Issues such as cable twists, small bend radii, pull force, cable ties that are too tight or staples can all have an effect on the cable performance.

Bringing cable to the rack can be accomplished in a variety of ways, some of which are dependent on the design of the rack itself. Racks that are designed with cable management in mind will present many more options to help maintain cable health and data flow.

Premise cables typically enter the rack from an overhead cable runway (ladder rack) or cable tray. Top openings also allow for the use of a cable drop on the cable ladder to maintain proper cable bend radius. Cable bundles may also enter the rack from below and enclosure bases should feature an open design to allow this.

Additionally, riser bases provide enclosures with extra clearance off the floor and can be used for cabling below each enclosure or cabling from one to another through knockouts when ganged. For raised floor designs, the riser bases are used with feet and angles to ensure they are firmly attached to the subfloor.

Maximizing Performance, Organization Inside the Rack

Dressing cables inside the rack is an important factor in achieving top operational performance. Again, it is important to look at the design and construction of the rack to ensure; it will not only permit but promote long life and optimum performance for cabling.

First and foremost, AC power cables need to be segregated from other cables to avoid cross-talk and other types of interference. Speaker wires can act as AC cables in high power situations so the same care should be taken in keeping signal wires away from close parallel runs.

Vertical lacer strips are used to route the maximum amount of cable into the enclosure while keeping power and signal cables separate. Cable can be laced from the top to the bottom of a rack or vice versa. Horizontal lacer strips, installed on the rear rack rail, address the common installation problems of cable strain relief and running cables from one side of the rack to the other. A telescoping lacer bar system allows for complete customization by the installer.

Other practices for managing cables inside the rack include bundling cables to prevent deformation of the cable jackets. Bundling also makes it easier to add or remove cables from the bundle. Patch leads help keep the rack tidy; keep in mind that a longer patch lead is heavier and can cause more shear stress on the cable.

Also, bend radius requirements apply to patch cords as well as premise cable. Tie saddles are the easiest way to manage cable ties and hook-and-loop cable fasteners should be used when installing cable that is sensitive to strain or when the wrap is so tight that a cable tie would affect the performance of the cable.

The best enclosures will include or offer as options lacer bars, cable trays, fiber spools and a wide variety of other cable management accessories that help the installer with every aspect of cable management. Not only does this make the installation easier, it also helps ensure optimal maintenance and service along with future system growth.

Jay Franetovich is an Application Engineer with Middle Atlantic Products. He can be contacted at [email protected].

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