Aqua-Air Manufacturing of Hialeah, Florida selected Bitzer compact screw compressors for two 100-ton, two-stage screw compressor chiller units for a chiller retrofit conversion project on a 230' Benetti Yacht built in 2000. DeWayne Nall, president of Aqua-Air, said Bitzer screws were selected for their quiet operation and high-reliability in marine applications.
The chiller units’ main components are two 50-Ton Bitzer screw compressors, 75 HP variable frequency drives (VFDs), 60-Ton shell and tube condensers, 100-Ton two-circuit brazed plate evaporators and 50-ton electronic expansion valves (EEVs). The capacity of each compressor is modulated through the use of four capacity unloaders. Each compressor can have its capacity reduced to a minimum of 12.5-Tons, which is 25 percent of its maximum output. As the chillwater loop further decreases in temperature the VFDs reduce compressor speed by 33%, reducing capacity to about 8.3-Tons.
The VFDs also provide for surge-less starting, and the current draw of the unit never exceeds its rated running amp draw. The unit is controlled by Aqua-Air’s PLC/Touchscreen System that was specifically designed for this project. Unlike a stationary application, the Bitzer screw compressors are mounted at an angle to assure oil return under all sea conditions.
Aqua Air’s major challenge was designing a chiller that could be disassembled at the plant, loaded into the Yacht through its engine room, and reassembled where the original open-drive chiller had been installed. Bitzer’s compact screw compressor geometry enabled the installing technicians to negotiate the tight quarters. When assembled, the OM100P2VGEK chiller unit is 116” long x 49” wide x 76” high and weighs approximately 5,500 lbs.
