Centrifugal chiller ties to hospital's ‘better, sooner' philosophy

Oakwood Hospital, in Dearborn, MI, replaced an aging and inefficient chiller with a 650-ton electric centrifugal chiller that offered partial-load flexibility and energy/cost savings. The chiller sections had to pass through the front entrance of the hospital (foreground).

A highly successful health care operation cannot only have an outstanding bottom line, but it must make long-term investments in quality and innovative HVAC upgrades at the same time. Oakwood Healthcare System in Dearborn, MI, offers an example of this statement. In 2000, the health care system turned heads in Michigan, and even nationwide, by promising to see emergency room patients in 30 minutes or less and to apologize and compensate patients with movie passes if they waited longer.

That was only part of the new thinking and aggressive turnaround for Oakwood under president and CEO Gerald Fitzgerald, which led to record financial results in 2003. Gross operating income has increased six-fold in just two years.

Elderly Absorbption Chiller ‘Toe Tagged'

Oakwood's emphasis on service and efficiency was evident when it replaced an aging and inefficient absorption chiller at Oakwood Hospital & Medical Center in Dearborn. The 50-year-old building encompasses nearly 1 million sq ft of comprehensive hospital services.

In bidding the new chiller system, Lipten Power of Wixom, MI, went above and beyond the bid specs, adding features, and recommending installation of a 650-ton electric centrifugal chiller by York International. It offered partial-load flexibility, ideal for efficiency and energy/cost saving in an institutional setting.

"On every bid, we try to apply everything we've learned in 36 years designing and installing powerhouse systems and suggest better ways to accomplish the client's purposes," said Jim Spencer, president/general manager of Lipten Power.

Under the system designed by Spencer and Jim Marshall, his central region operations manager, the new York chiller (rated at .21 to .338 kW) could go online first, with trimming of the unit in lower load situations for greater efficiency. The hospital's two older Trane chillers, rated at about .65 kW (depending on load) per ton, would operate to handle the higher loads.

"The York centrifugal system was chosen for efficiency at 0.544 full load kW/ton, 0.338 kW/ton NPLV," said Marshall.

"It's able to operate well at turn down ratio to 50 tons or less and maintain 43°F water. Chiller efficiency is a notable 0.338 kW/ton (ARI) based on the ARI (NPLV) method of averaging the chiller energy at full load, 75% load, 50% load, and 25% load.

The chiller uses refrigerant R134-a because of its great heat transfer properties, ozone friendliness, and common use in lieu of its predecessor, R-12, according to Marshall.

George Davis, director of plant operation and maintenance for Oakwood Hospital & Medical Center said, "Because of its low kW per ton ratings, we use the York as first on at the beginning of the cooling season and last off at the end of the season."

"It runs at much lower condensing water temps, 55° to 60°; a lot more efficient during spring and fall runs."

"Our Trane units are 17 years old and have a minimum condensing temperature of 75°, Trane prefers 80°, and so we can keep the wear and tear off of them by running the York in low load situations," he added.

Lipten also specified the latest VSD and instrumentation on both the chiller and cooling tower and integrated them for optimum efficiency and controllability. The VSDs allow for efficient operation from low to high demand while the instrumentation measures all pertinent parameters to allow for computation of throughput and optimal control.

Critical 60° OR Temp

Hospital HVAC requirements are among the most demanding. At Oakwood, operating room cooling, set at 60° is critical, and other areas almost as critical. Chillers go on when outside temperature rises above 45°. Dependability is paramount.

"After a year of operation with the new system, we are on target to achieve an annual energy and maintenance savings of about $100,000," said Davis.

The installation included a 1,950 gpm, Marley Cooling Technologies rooftop cooling tower. Existing piping had to be used, requiring National Industrial Maintenance of Dearborn, MI, to hydroblast the 16-in. lines and inspect them through existing openings.

Logistics were accomplished under the direction of Lipten Power by Pipe Systems, Inc. of Troy, MI. Lake Erie Electric of Farmington Hills, MI, handled electric work for Lipten.

"It's good to see an institution listen to new ideas and add to their bid specs and original investment in favor of an innovative and quality system that will pay dividends in superior service and lower operating cost over the long haul," said Spencer.ES

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