Bank installs rooftop variable-refrigerant system
In need of HVAC upgrades, a San Angelo, Texas, bank chose mechanical contractor Air Dynamics to retrofit a landmark HVAC system design.
The 37-year-old facility’s original HVAC concept was one of the nation’s first commercial heat pump applications that recovered heat from lighting and converted it into energy for the chilled water loop system, officials said. However, officials say the aging system’s rising expenditures for cooling tower chemicals, repairs and general system maintenance surpassed $10,000 annually. Replacement parts also became problematic, said Air Dynamics of San Angelo President Cecil Sain.
Air Dynamics became one of the first U.S. contractors to select the RD-Series, a line of variant refrigerant flow-specific line-set protection duct products that was recently introduced to the North American market by RectorSeal. The RD-Series comes with a full line of fittings, adaptors and couplings, such as the 45- and 90-degree elbows that Air Dynamics used in connections to building line-set chases.
The building’s original three air handlers were replaced with 32 Mitsubishi variable refrigerant flow-based fan coil units in zones fed by two branch circuit controllers per floor. Eighty percent of the building’s original supply ductwork was reused for air distribution. The VRF equipment’s sizing was determined by the building’s peak north side heating load.
“The building owners are very pleased with how the roof looks neatly laid out and professional in appearance, which also reflects on our overall design and Air Dynamics’ installation,” said Paul Wilkerson, owner of Power Systems Inc., consulting engineer for the project.
With the new system, operating expenses are expected to be approximately 30 percent lower than those of the previous system, while also providing zoned temperature control for occupants.
Sain also wanted to find the highest quality mounting system for the rooftop condensers and discovered Big Foot Systems rooftop equipment mounts, also available through RectorSeal.
The mounting system features adjustable legs and 12-by-12-inch-square anti-vibration nylon feet. When the building is re-roofed, roofing can be replaced underneath one leg at a time while the units and piping stay connected and functional.
“The mounting system is costlier in materials than I-beams, but it’s really an even trade-off because installation labor is cut by more than half and it looks so much better,” Sain said.
Another energy savings built into the design was a 10-ton outdoor air system from Desert Aire and supplied by Direct Expansion Systems. It provides outdoor air dehumidification and conditioning, but also recovers 95 percent exhaust air energy. The unit also includes an integral back-up gas-fired heater for additional heating capacity.