Project Challenge: Replace two existing mechanical HVAC systems from the 1960s that served critical areas of the hospital. Any downtime risk had to be carefully scheduled and managed. The existing equipment was buried in the second-floor mechanical space, and a structural column located in the space had to be incorporated into the new replacement air handing unit design.

Solution: The engineer coordinated closely with the owner to design around built-in place, field erected HVAC equipment. Two 65,000 CFM side-by-side air handling units were designed to replace the existing systems. Units are 100% outside air makeup air units. The units were carefully located to allow for proper service access, future component replacement, and redundant airflow to the building spaces. A vertical building column was built into one of the units.

Points of Interest: Air handling unit construction materials and major components were constructed of all aluminum or stainless steel materials. The all aluminum construction included the 2-1/2” panels system, the structural support base, and the AHU walking surfaces. Internal components consisted of three levels of filtration (HEPAs, carbon, and pre-filtration), heat recovery, hot-water heating, chilled water cooling, steam humidification, and an 8-fan array. A temporary rental system was supplied to mitigate downtime concerns during mechanical room demolition and the field building of each new AHU. Each unit was erected in place in less than three weeks. Both units were field performance tested to assure quantified performances were met. Units were air-leakage tested at 8” static pressure allowing less than 1/2% air leakage. One of the units was designed around an existing building column, carefully located within the AHU design to allow proper airflow and unit serviceability. Each air system measured 28’L x18’W x 10’H. The designed unit height was within fractional inches of the existing building structural ceiling.

One of the main challenges to overcome in the design of this project was the column in the middle of the equipment room. The teams built one of the air handling units around this structural column.

Another challenge was installing the new systems without disrupting hospital operations. The solution included bringing in a 100,000 CFM temporary system to provide air to operating suites and care areas while the new AHUs were erected on site.

Air handling units were broken down into individual pieces and placed in shipping crates. Egress constraints to the space dictated the pieces from the roof area were brought through a mandoor to the interior mechanical space and AHUs were then built in place.

The completed 3-1 Air Handling Unit within fractional inches between the top of the unit and existing building utilities and ceiling.

Project Contributors:

• Owner – Catholic Health/Mercy Hospital (Abbott Road)
• Design Consultant – M/E Engineering
• Installing Mechanical Contractor – Quackenbush Company
• ATC Provider – U&S Services
• Equipment Provider – Air Enterprises SiteBilt AHUs/ R.L. Kistler