Hospital’s New Children Cardio Surgery ORs Incorporate State-of-the-Art HVAC System Design

Open heart surgery for children demands some of the healthcare industry’s most stringent indoor environmental quality (IEQ) requirements; however Nemours Children’s Hospital’s new cardiovascular operating room (CVOR) far surpasses all current standards with a state-of-the-art HVAC design.
Supplying robust 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 HVAC was designed by consulting engineering firm TLC Engineering Solutions, Orlando. 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, St. Louis, and specified by TLC’s Ricardo Walker, associate/mechanical project leader.

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, which is nearly 10 degrees colder than typical ORs. 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 OR area parallels the facility’s Leadership in Energy and Environmental Design (LEED) Gold certification it achieved after opening in 2012 as the nation’s first green-field children’s hospital in 40 years. 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 LAT down further to 34°F. “This design assures we can always provide a room temperature of 55°F and a 50-percent 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. “Only a custom air handler can reach our 34°F temperature without freezing out the coil.”

Heating the OR to 75°F within 20-minutes is accomplished with a 48kW-in-duct heater, which reaches set point temperature faster than hot water coil heaters TLC normally prefers in hospital settings.
TLC specified controllers for each OR at the sixth floor nurse station and trained the surgeons and hospital personnel to program their desired set points.

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, which TLC specified originally for other OR booster coils and with a capacity allowing the hospital to build future ORs.

TLC also specified the air handlers with a total energy wheel, manufactured by InnergyTech, Drummondville, Quebec, which removes 40-grains/lb. of moisture. The wheel has the capacity to lower outdoor air temperatures by 10 degrees before the primary cooling coil, which results in more than 12 tons of cooling energy performance. It also has a capacity to supply dew points below 45°F.

Both air handlers are also outfitted with ultraviolet germicidal irradiation (UVGI) lamps that prevent coil mold growth and also disinfect the airstream of biological contaminants. Since nearly 75-percent of the OR air is energy-efficiently recirculated, the UVGI lamps are critical for preventing hospital acquired infections (HAI).

The mechanical room space’s air handlers, which were installed by the project mechanical contractor, Harper-Limbach LLC, St. Mary, Fla., are configured in a “U” shape because of the sixth floor’s low ceiling heights, which prevented a “C” shape configured air handler preferred by engineers for its verticalness and smaller footprint.

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. A 99.99-percent HEPA filter provides final filtration.

Variable frequency drives, manufactured by Yaskawa America, Waukegan, Ill., help maintain a 1.2-w.g. static pressure throughout the ORs, regardless of variables such as pressure losses from filter or coil build-ups. The facility’s building management system (BMS) oversees static pressure and adjusts automatically.

The last component in the air handler’s airstream is a humidifier grid supplied by outboard steam humidifiers. Typically, most southern climate hospitals don’t use steam central plants, therefore TLC specified electric generated humidity.

TLC’s stick-built ventilation distribution design features 30 air changes/hr. Laminar flow diffusers, manufactured by Price Industries, Suwanee, Ga., seal the surgery table area in the CVOR. Air is then drawn into two 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 surgical technique as well as IEQ. TLC took all of these considerations into account, but continues monitoring the design, as it does with all building owner clients. TLC continues to monitor the set points based on BMS performance statistics, ongoing site visits