ACHRNEWS

Dehumidifiers Supplement Cooling For Cable TV Network

March 2, 2003
KNOXVILLE, Tenn. — With the tremendous heat load produced by broadcast operations servers and associated high-tech equipment at the corporate headquarters of Scripps Networks here, mechanical engineer Greg Farmer needed a reliable means to cool and dehumidify the space. Maintaining precise space conditions with backup redundancy was critical for the newest broadcast operations floor of Scripps, which is the home of HGTV, Food Network, DIY Network, and FineLiving Network.

Scripps' new computer and digital broadcast environments are part of its latest 36,000-square-foot addition. Redundancy was achieved by designing a mechanical cooling/dehumidifying system to automatically switch from rejecting heat to the heat pump loop or an outdoor condenser.

Farmer is a vice president of mechanical engineering at the architect-engineering firm of Michael Brady Inc., Knoxville. He used 14 Dry-O-Tron dehumidifiers, manufactured by Dectron International, Roswell, Ga., to control the conditions in the technology area.

The dozens of piping runs were plumbed by mechanical contractor D.F. Shoffner, Knoxville.

Cost Savings

The use of packaged dehumidifiers consumes the same 4,000-square-foot floor space of the corresponding technical room equipment, but since there is no associated central plant and accompanying mechanical space, about 1,000 square feet is saved. With construction costs averaging $125 per square foot, this amounts to savings of $125,000.

Building operating costs are also saved because the technical room requires year-round cooling. A feature of the redundant heat rejection capabilities of Dectron's dehumidifiers allows them to switch from the outdoor condenser to the heat pump loop anytime.

During the heating season, the units automatically reject heat into the heat pump loop. The resulting increased loop temperatures improve the effectiveness of all the other heat pumps connected to it. This feature provides heat for the addition's offices, a tape library, viewing rooms, and cafeteria at an annual energy savings of $5,000.

Farmer worked through Dectron's manufacturer's representative, Myron Carter, Rome Eddleman, Knoxville, to specify only four custom-manufactured condensers with multiple circuits by Dectron's heat transfer division, Ref-Plus.

Backup heating, if needed, will be handled by an existing 500,000-Btu boiler by Raypak Inc., Westlake Village, Calif.

"My calculations reveal that the boiler probably will never be needed," Farmer said.

Farmer figures that maintaining packaged dehumidifiers versus chillers will save an estimated $10,000 to $15,000 in annual maintenance costs. Scripps' in-house staff, which is already trained in direct expansion equipment, can perform most service tasks versus the more costly service people required for chiller repair.

A 265-square-foot mechanical space inside the technology room is walled off from the five 22-foot-long, 8-foot-high racks of computer equipment they cool. The mechanical space has three Dectron DA5-30 dehumidifiers as well as pre-piping for an additional unit in the future. Two units are for current conditions and the third serves as a backup. The space also includes two DA5-10 dehumidifiers that serve the adjacent broadcast control center and its equipment.

Each bank of Dectron units is equipped with an on-board humidifier to eliminate static electricity and maintain 50 percent relative humidity during the winter.

Above the first floor mechanical room is a 592-square-foot secondary mechanical room that houses six more DA5-30s for the main technical room. There's also a hot backup site of corporate IS/IT servers with three more DA5-030 dehumidifiers.

Farmer devised an air distribution system that doesn't create air noise that could affect broadcasts. Above each set of computer racks is a series of two plenums: an upper supply plenum, which is connected to a lower distribution plenum via several short ducts. The supply plenum, which has a continuous slot to drop air along the top of the racks, has an equal pressure and self-balancing design. The plenums are integrated into a soffit and end wall system developed by the architect. A cable access area where air is returned to the ceiling plenum separates the racks and wall system.

Other equipment used on the project included two Taco 7.5 pumps and one Baltimore Aircoil Co. closed circuit cooler. Twenty-seven conventional McQuay International heat pumps condition air to offices within the expansion. Scripps' existing Alterton Technologies building automation system operates the majority of the HVAC equipment and systems.

The project's electrical engineer, Vreeland and Associates, Knoxville, specified an uninterruptible power supply and a backup diesel-powered generator.

Publication date: 03/03/2003