Cooling towers solve hospital's HVAC construction problems
Hospitals contain some of the most diverse and demanding environments that HVAC systems can handle.
Operating rooms, critical care facilities, data centers, imaging centers — plus worker productivity — all are to some extent dependent on the reliable operation of the HVAC system, particularly in warm weather.
When cooling towers are sluggish or shut down for maintenance, added stress is placed on the building’s chillers, and the performance of the HVAC system may be affected.
Such was the case with Davis Memorial Hospital in Elkins, W.Va. A subsidiary of Davis Health System, the 160,000-square-foot hospital was founded in 1904, fully renovated in 1994, and is now undergoing 72,000-square-foot expansion. The modern hospital includes a 90-bed medical facility, nine intensive care units and 36 monitored beds, with services ranging from emergency treatment to acute inpatient care, cancer treatment, diagnostic services, pulmonary rehabilitation, women’s health services and many types of surgery.
To overcome recurring cooling tower-related HVAC performance problems, Davis Memorial recently purchased two new cooling towers to support its two 300-ton Carrier chillers.
High performance, low maintenance
Like the owners of many industrial, business and institutional buildings, the hospital management was looking for a more advanced cooling-tower technology that would optimize performance while minimizing maintenance requirements.
“I researched various cooling-tower technologies on the Internet and found a unique line of cooling towers features a seamless plastic shell,” said Steven Johnson, director of the hospital’s support services. “The one that attracted my attention was a line that was made of high-density polyethylene (HDPE), manufactured by Delta Cooling Towers. Of course, there were a lot of other models available, but most of them seemed to be the metal-clad design.”
For many cooling-tower users, metal-clad models have become outmoded because they are vulnerable to corrosion from salt air, industrial gasses and even the chemicals that are used to treat the re-circulating water.
HDPE cooling-tower shells are virtually impermeable to corrosive elements, including water-treatment chemicals such as chlorine, as well as ultraviolet rays.
Johnson and engineers from Davis Memorial, as well as some from Carrier, decided to visit Delta Cooling Tower’s manufacturing plant for a tour so that they could get a closer look at the design and building of the manufacturer’s product line, which includes models ranging from 10 to 2,000 cooling tons.
“We were all impressed with the plant tour,” Johnson said. “Not only was management helpful in explaining the features and benefits of various product models, but they also helped us confirm our preliminary specs for the cooling towers we had in mind. We were quite surprised to learn that this line of cooling towers were about 20 percent less expensive than many conventional designs.”
He was also pleased with the standard warranty offered on all products. While many metal-clad cooling towers are warranted for only one year, the HDPE-based cooling-tower shells from Delta carry a standard 15-year warranty.
The two towers selected by the Davis Memorial team included a 250-ton TM Series unit and a 180-ton Paragon Series tower.
While the avoidance of downtime and the need for unscheduled cooling-tower maintenance were critical requirements for Davis Memorial Hospital, there were other features of the Delta design that also had significant value.
“The variable-speed, direct-drive motors that run the fans on our new towers also provide unexpected benefits,” Johnson said. “First of all, these drives are far more efficient than we initially realized. The fan motors on our old towers were 30 horsepower each, and consumed considerably more energy than the new ones which are only seven horsepower each, and at least 50 percent more energy efficient.”
Out with the old
Johnson explained that the hospital’s old fan motors were either on or off. With the new variable-speeds drives, they are set up so that it has to be a hot day before they run at 100 percent.
“The new direct-drive fans are usually running at about 40 percent,” he said. “Running at 100 percent they are only pulling four amps, which is much less energy than before.”
Johnson added that the new direct drives are also far less maintenance intensive, which results in even greater savings.
With no belts, shafts, bearings or other external parts to service, the direct-drive motors are virtually maintenance free.
Another important benefit of the new direct-drive cooling towers is that they run quiet.
“Drives using belts often require adjustments, or you will hear them squeal,” Johnson said. “We’re a hospital, so quiet is expected. Also, we’re located right in the middle of a residential community. In the past, we received complaints from people in the neighborhood if the belts were squealing, particularly if it happened at night when they were trying to sleep. That was a serious problem, so our maintenance people often had to fix the belts in the middle of the night. With the direct-drive fan motors, we don’t have that problem.”
The new cooling towers have not only solved chiller and HVAC problems, but have exceeded the hospital’s expectations, Johnson said.
“These new cooling towers have virtually eliminated unscheduled emergency maintenance,” he said. “That not only makes us happy, our chiller-maintenance contractor is also very pleased.”
John Flaherty, president of Delta Cooling Towers, estimated that with the combined savings on energy, water usage, maintenance and chemicals that the hospital is now realizing, payback for the new cooling towers should be within two years.
This article and its images were supplied by Delta Cooling Towers.