The QTC4 line includes 21 models ranging from 150 to 360 tons. The line of air-cooled variable-speed-drive screw chillers includes hybrid falling-filling-type evaporator and microchannel-type condenser to optimize heat transfer and minimize the refrigerant charge.To minimize pump energy consumption, chillers can be utilized in variable primary flow (VPF) systems, which reduce the chiller flow to match the load. Options include variable-speed-drive (VSD) condenser fans to enhance part-load efficiency and reduce part-load sound. Native communications capability supports BACnet (MS/TP), Modbus and N2 with optional support for LON communications.