Cable Pathways: A Data Center Design Guide and Best Practices

A ladder rack is made of tubular steel and comes in sizes from 6” to 36” wide. The installation of a ladder rack is simple and requires little trade experience. Ladder rack come with many accessories such as 90-degree bends, waterfalls and cable retaining posts. These accessories allow the routing of cable without damage.

A cable tray is a ladder rack with sides and may be steel, aluminum or fiberglass. These sides allow for a greater amount of cable to be supported. The maximum loading depth recognized by the NEC is 6”. The cable tray is designed to support both electrical and data cables and is typically more robust than a ladder rack. It requires a pre-design effort because it is not flexible to work with in the field.

A basket tray is a cable tray designed for light duty applications. The basket tray is lightweight and easy to install; however a certain level of experience is needed to properly install. Many of the accessories that accompany ladder racks also accompany basket trays, to ensure proper bend radiuses are maintained a proper transition to the equipment rack.

An underfloor cable tray is a product used primarily in data centers. The concept is the same as the overhead support apparatus. However, when using under floor cable tray systems, the air space may be a plenum air space, so all cable and patch cables would need to be plenum for proper air flow.

Horizontal wire managers allow the neat and proper routing of patch and equipment cords from the switch/server to a patch panel. Density is very important in data center cabinets and racks so keep in mind how many rack spaces are being utilized with horizontal wire managers. Horizontal wire managers are available in many sizes from 1U to 4U. 1U and 2U heights are the most prevalent. They also come in depths from 1.75” to 6” deep. Cable management can be accomplished in both the front and rear of the rack with double-sided organizers. Depending on how much you want to hide the cables, horizontal wire managers can also come with or without doors/covers. They come in metal and plastic.

A vertical wire manager provides a vertical pathway for cable within the rack or cabinet. It allows multiple horizontal wire managers to feed into a larger vertical pathway for the entire height of the rack. There can be as many as 20 horizontal wire managers feeding into one large vertical manager. Therefore, these vertical managers need to be large, with depth sizes from 4 to 10 inches deep and up to 10 inches wide. These managers can come with waterfalls and spools to help manage multiple cables and to help with maintaining proper bend radius on copper and fiber cables.

It’s important to make sure there is enough space to accommodate all the patch cords to avoid overfilling the wire managers. Overfilling wire managers will cause kinking in the patch cords make it very difficult for moves, adds or changes. You should allow a minimum 30 percent space in the wire manager for growth.

Copper cables are more difficult due to their weight and large OD compared to fiber optic cables. Copper cables are typically used for inter and intra rack communications.

Fiber optic cables offer options to reduce cable fill and can provide much greater bandwidth than copper.

There are many types of fiber optic cables designed for data centers that will dramatically reduce cable fill in cable trays.

Pre-Terminated fiber optic cables are also prevalent in data centers. They are used for many reasons including quality, dependability, and reduced installation time. Cable slack is hard to accommodate in data centers no matter where it is located—cable trays, vertical or horizontal cable managers. Every effort should be made to get the lengths right before they are installed.