Creative Cooling Crowns Commercial Complex

The Christian Street Court, a commercial/retail building complex in downtown Lancaster, Pa., recently received an HVAC overhaul. Built in 1900, the five recently-renovated buildings encompass 58,000 sq. ft. of space and house, among other things, Godfrey Advertising, Inc., central Pennsylvania's largest advertising agency.

"The fact that these five buildings were constructed separately, at different times and on different levels, without the idea of ever being hooked together or interconnected, presented the biggest challenge," said Stephen P. Mitrani, president of Devcon Services, Inc., the contractor and one of the complex's owners.

These factors made it especially challenging to choose the right type of HVAC system. Flexibility was of the utmost importance, and the owners decided on rooftop units. This type of system provided efficiency in zoning the project, and in effect, provided tenants with individual HVAC systems.

HVAC contractor Brubaker installed 19 rooftop package heating and cooling units, ranging in capacity from four to 10 tons. The efficiency of the units was one of their biggest selling points. The standard efficiency air-conditioning units achieve a minimum energy efficiency rating (EER) of 9.0, and the high-efficiency units can reach 11.5 EER. The heating units are capable of steady-state efficiencies of 80%.

Balanced heating and cooling is also at the heart of the system. The air-conditioning units have two compressors with independent refrigeration circuits that are charged with HCFC-22. Under mild temperature conditions the air-conditioning load is light, and just one compressor turns on, providing 60% of the unit's cooling capacity. When temperatures warm up, the second compressor kicks in to provide an additional 40% of cooling capacity.

In addition to heightened efficiency and well balanced temperature control, ease of installation was another positive aspect of the HVAC equipment. The air-conditioning units were all self-contained in a cabinet sized to a common footprint, installed on a common-sized roof curb and assembled on a rigid full-perimeter base rail, allowing for three-way forklift access and overhead rigging.

Godfrey is served by 10 of the air conditioning units via more than 1,000 ft. of ductwork. Installing the ductwork was a challenging feat, according to Brubaker's HVAC sales representative, Randy Zendt. Initially, he explained, the firm planned to use larger units. However, the roof wouldn't have been able to support them without major redesign work. So, a structural engineer was employed to identify the strong points of the roof that could support smaller units. These areas were reinforced for additional support.

"We were very diligent about how we laid out and designed the ductwork, making sure we got plenty of supplies and returns," Zendt said.

In some cases, ductwork had to be offset around historical items. "Where it couldn't be concealed, we created designs that were both functional and easy to look at," said Dave Rupp, Brubaker's HVAC installation mechanic.

Efficient, balanced, flexible and aesthetic, Christian Street Court's HVAC system should keep Godfrey and its neighbors comfortable for years to come.