APSG VFD Air-Cooled Variable-Speed Screw Chiller

The APSG VFD is Petra Engineering's flagship air-cooled chiller, combining a semi-hermetic twin-screw compressor with an integrated variable frequency drive to deliver cooling capacity that tracks actual building load rather than running flat-out against a fixed setpoint. The VFD continuously trims compressor speed, producing part-load efficiency (IPLV) of up to 5.85 kW/kW in the high-efficiency variant — a 20–25% improvement over fixed-speed screw equivalents running the same annual duty profile.

This chiller suits large commercial and institutional plants: convention centres, hospital complexes, large terminal buildings, and district-cooling satellite plants where chillers spend the majority of their hours at 40–70% load. The microchannel condenser coil (MCHE) design reduces refrigerant charge and condenser footprint while maintaining heat-rejection capacity at elevated ambient temperatures, a critical trait for GCC rooftop installations where design dry-bulb can exceed 46 °C. Refrigerant R-1234ze carries a GWP of just 7, meeting current and anticipated low-GWP regulatory thresholds without compromising capacity.

Soft-start is standard, eliminating the high-inrush current demand penalty on generator-backed or constrained utility feeds — relevant for sites where standby power is sized to a strict kVA budget. Optional cooler tape heaters rated to −29 °C extend deployability to cold-climate satellite facilities. The unit is AHRI 550/590 and Eurovent certified, giving specifying engineers third-party verified capacity and efficiency data rather than manufacturer-declared figures. Electrical panels meet NEMA 3X / IP54 as standard, with NEMA 4X stainless steel available for coastal or corrosive-atmosphere sites.