ABSORPTION CHILLERS CUT COOLING COSTS 45 PERCENT; PROVIDE CONSISTENT COMFORT, MINIMAL MAINTENANCE

When Silverstein Properties considered overhauling or replacing the 30-year old centrifugal chillers at its 40 story skyscraper at 521 Fifth Ave., company officials, after analyzing various financial, engineering and space considerations, concluded their best choice would be a total retrofit.

Their increasing operating costs and decreasing efficiencies notwithstanding, the two 500-ton steam-driven units used CFC-114 refrigerant, which is slated to be phased out at the end of 1995 because of the Clean Air Act. Working with consulting engineer E.E. Linden Associates, Silverstein Properties studied several replacements and determined the carrier 16JT double-effect, steam absorption chiller as the ideal alternative.

Chi Chu, directory of energy and engineering for Silverstein, explains, "The 16JT absorption chillers deliver efficient cooling, using water as the refrigerant. Not only are the chillers environmentally responsible, their energy efficiency enabled us to get a utility rebate from the Consolidated Edison that paid for 50 percent of the equipment cost.

The new chillers were installed in February, 1994, by the service contractor, Power Cooling. With access tight - the chillers were hoisted into a second story window - each unit's two-piece assembly was an important feature that made rigging and installation in the heart of Fifth Avenue easier.

Based on the unit's performance to date, Harvey Rifkin, building manager for the facility, estimates a minimum of $0.15 per square foot in annual operating cost savings. "That amounts to about 45 percent savings over our old equipment," he says.

Cost-effective cooling is produced in various ways. First, only the controls and refrigerant/solution pumps require electricity. In addition, with its two-stage, double-effect design, the 16JT chiller incorporates both a high- and low-stage generator for two stages of solution reconcentration. The low-stage generator acts as the condenser for the high-stage generator, increasing unit efficiency and achieving a steam rate of 10 pounds per hour per ton.

Silverstein's chief engineer, Martin Reilly, praises the Carrier chiller's steady output. "The machines maintain the water temperature we set, usually between 44 F and 48F, or lower if we desire," he says. "As a result, the building's HVAC system provides tenants with consistent comfort. What's more, the chillers require minimal maintenance."

"Carrier has an exceptionally good track record with its chiller technology," says Chu.

Echoing the views of his associates, Angelo Croce, Silverstein's vice president, operations, says, "We're delighted with the new Carrier chillers. Their performance and savings has exceeded our most optimistic expectations."

Carrier Corporation is the world's largest manufacturer of heating and air-conditioning systems and equipment. It is a subsidiary of United Technologies Corporation, provider of a broad range of high-technology products and support services to the aerospace, building systems and automotive industries.

Reprinted with permission, from Building Operating Management Magazine

Building Operating Management can be reached at http://www.facilitiesnet.com