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.