Description – The Base Exchange at Barksdale Air Force Base was conditioned by (25) DX Rooftop units that were approximately 10-20 years old. The units were becoming inefficient and expensive to maintain. Each year operating costs for the rooftop units were increasing. In 2015 maintenance costs exceeded $ 40,000 for the rooftop units.
Solution – Storer partnered with Fitzgerald’s Mechanical Contractors to install a variable refrigerant system to serve all (25) rooftop units. The rooftop ranged in size from 5 to 25 Tons. Each rooftop was converted to a terminal air handling unit which consisted of removing the compressor and replacing the cooling coil, expansion valves, and retrofitting the unit controls to interface with Multistack control system. Also, many of the gas furnace heat exchangers were replaced. Outside air economizers with CO2 sensors were added for energy savings on fresh air for ventilation that is required for the space. In addition (3) energy recovery wheels were installed for pre-conditioning of outside air. All (25) rooftops refrigerant circuits were piped to (2) 250 Ton Multistack Air Cooled Condensers, for heat rejection. During the project Storer engineers worked with Multistack product engineers to develop the piping schematic for the new rooftop unit cooling coils.
Results – This system was the first Multistack variable refrigerant system installed in the local market and the 2nd installed in the U.S. The new system is expected to reduce the operating cost of the HVAC system by 20%.