Nemours Children’s Hospital

Supplying outdoor air while maintaining surgery-mandated low dew point temperatures in the inherently humid environment of Orlando, Fla., was an IEQ and outdoor air energy-efficiency challenge solved by innovative HVAC engineering and custom manufactured equipment.

The Lake Nona Medical City campus-based hospital’s new sixth-floor, 12,300-square-foot surgical OR’s HVAC was designed by consulting engineering firm TLC Engineering Solutions, Orlando, FL. The CVOR and an adjacent Hybrid OR/Catheterization Lab are the featured spaces surrounded by supplementary pre and post-operation rooms, a waiting area and patient rooms. The retrofitted area also includes a 1,090-square-foot mechanical room housing each ORs’ independent custom commercial air handler manufactured by Temtrol—division of Nortek Air Solutions, and specified by TLC Mechanical Engineer Ricardo Walker.

Both ORs were designed under Class C recommendations, the most stringent class outlined in the Facility Guidelines Institute’s (FGI) Guidelines for Design and Construction of Hospitals and Outpatient Care, which encompasses many standards, including ASHRAE Standard 170 Ventilation of Health Care Facilities recommendations. Furthermore, combining FGI guidelines with cardiology surgeon requests resulted in an unconventional CVOR room temperature of 55°F. Equally challenging was surgeons’ requests for a post-operation 20-minute CVOR temperature rise of 20-degrees to 75°F to quickly warm patients.

Consequently, custom equipment is needed to provide those set points and other surgeon IEQ requests while also delivering optimum energy savings. The CVOR’s low temperature challenge is solved with a 7,000-CFM air handler featuring dual cooling coils. The primary coil, supplied by the central plant’s chilled water loop, has a 43°F leaving air temperature (LAT). A secondary glycol circuit booster coil efficiently brings the Leaving Air Temperature (LAT) down further to 34°F. “This design assures we can always provide a room temperature of 55°F and a 50-percent Relative Humidity (RH) to the CVOR and still have enough latitude if surgeons change the parameters,” said Walker, who was assisted on the specification by Temtrol’s local manufacturer’s representative, Tom Barrow Co., Orlando, FL.

• Heating the OR to 75°F within 20-minutes is accomplished with a 48kW-in-duct heater.
• The primary coil is supplied by the facility’s original 3,200-tons of water-cooled centrifugal chillers. However, the booster coil is supplied by an existing OR 135-ton glycol/water chiller.
• TLC also specified the air handlers with a total energy recovery wheel, which is manufactured by InnergyTech, which removes roughly 40-grams/lb. of moisture on a peak design day.
• Both OR air handlers are also outfitted with ultraviolet germicidal irradiation (UVGI) lamps that prevent coil mold growth and disinfect the airstream of biological contaminants.
• Fan redundancy is handled by FANWALL TECHNOLOGY^®, manufactured by Nortek Air Solutions, which consists of four-fan (2 x 2), N + 1 fan wall array. Each unit also include a 99.99-percent HEPA filter which provides final filtration.
• Variable frequency drives, manufactured by Yaskawa America, help maintain the proper airflow and static pressure throughout the ORs.
• The last component in the air handler’s airstream is a humidifier grid supplied by outboard steam humidifiers.
• TLC’s OR air distribution design features 30 air changes/hr. Laminar flow diffusers, manufactured by Price Industries, surround the surgery table area in the CVOR providing laminar air flow over the patient bed, assuring contaminants are kept away from the surgeons and the patient, and drawn into low position return air grills.

ORs might be perceived as having routine requirements; however, every OR is vastly different, and every doctor has different parameters, according to Walker. Compounding these variables at Nemours is its children surgery specialty, which differs significantly from adult surgery in technique as well as IEQ. TLC took all these considerations into account, but continues monitoring their design, as it does with all building owner clients.