APX Air-Cooled Chiller
Mid-range air-cooled chiller with semi-hermetic reciprocating compressors, covering 35–460 TR across 50 Hz and 60 Hz markets for commercial cooling in space-constrained rooftop applications.
The APX is Petra Engineering's reciprocating-compressor air-cooled chiller, spanning 35–390 TR on 50 Hz supplies and 40–460 TR on 60 Hz, making it one of the wider capacity ranges in Petra's air-cooled portfolio. Unlike the screw-compressor models, the APX uses high-performance semi-hermetic reciprocating compressors arranged across independent refrigeration circuits — one circuit per compressor — so partial compressor failure does not render the entire unit inoperative, a resilience characteristic valued in facilities that cannot accept full cooling loss.
The welded structural C-channel base with heavy-duty lifting lugs and CNC-formed hard copper piping reflects a build quality oriented toward long service life rather than lowest first cost. Copper tube / aluminium fin condenser coils are standard; copper-copper coil variants with epoxy-painted copper piping are available for coastal GCC sites where salt-laden air accelerates aluminium fin corrosion. Oven-baked polyester electrostatic powder paint on the chassis provides a uniform, durable factory finish.
The APX occupies the mid-market bracket between large-format screw chillers and smaller packaged equipment, typically serving mid-scale commercial buildings, retail centres, and light-industrial facilities where budget and floor space favour a proven reciprocating platform over the higher capital cost of VFD screw alternatives. Optional hot gas bypass extends stable operation down to very low load fractions without compressor cycling, and optional tape heater packages cover cold-start scenarios. The unit's microprocessor controller handles all safety shutdowns with compressor current monitoring and electronic overload protection as standard.
Technical specifications.
| Cooling capacity (50 Hz) | 123–1,372 kW (35–390 TR) |
| Cooling capacity (60 Hz) | 141–1,618 kW (40–460 TR) |
| Compressor type | Semi-hermetic reciprocating, independent circuits |
| Condenser coil (standard) | Copper tube / aluminium fin |
| Condenser coil (optional) | Copper tube / copper fin, epoxy-coated piping |
| Refrigerant-side design pressure | 1,000 kPa |
| Water-side max working pressure | 1,500 kPa |
| Base construction | Welded C-channel, heavy-duty lifting lugs |
| Electrical panel rating | NEMA 3X / IP54 |
| Low-ambient heater options | 0 °C / −18 °C / −29 °C |
Use cases.
- ›Mid-scale commercial buildings, retail centres, and light-industrial facilities on either 50 Hz or 60 Hz supply requiring a single air-cooled chiller in the 35–460 TR range
- ›Rooftop applications where independent refrigerant circuits per compressor provide partial-load resilience against single-compressor failure
- ›GCC coastal sites where copper-copper coil variants and epoxy-treated piping are specified to resist salt-air corrosion
- ›Facilities with variable occupancy schedules benefiting from hot gas bypass to maintain stable operation at very low cooling fractions
- ›Budget-sensitive projects where reciprocating-compressor capital cost is preferred over VFD screw alternatives with a lower IPLV target