A white paper authored by Victor Avelar of APC by Schneider Electric takes the position that placing cabling in overhead cable trays in data centers is an energy-saver compared to placing cabling underneath raised floors. The paper says the choice to run cables overhead "can result in an energy savings of 24 percent."
The paper cites the following drawbacks of underfloor cabling.
- Raised floors filled with cabling and other obstructions make it difficult to supply cold air to racks.
- The cutouts in raised floors that are necessary to provide cable access result in cold-air leakage of 35 percent.
- Cable-blockage and air-leakage problems lead to the need for more cooling equipment.
The paper includes tables that quantify the energy-use impact of overhead versus underfloor cable placement. In addition to recommending overhead placement, the paper also advises to employ multi-level overhead trays. Doing so "allows data center personnel to sort and plan cable location, integration and removal on an ongoing basis," the paper says.