Compressor for air conditioning and heat pumps
The compressor moves refrigerant between the low-pressure and high-pressure sides. Understanding its place in the complete system is the first step toward choosing a type or finding a replacement.
Guide
ContentsRefrigerant and room air
Refrigerant flows through a sealed circuit. Room air passes across the indoor heat exchanger, transferring heat through its walls. The compressor handles refrigerant vapour, while the fan moves air. A water chiller transfers the cooling effect through a separate water or other secondary-fluid circuit.
Cooling and heating modes
Cooling uses heat absorption at the evaporator; heating uses heat rejection on the hot side. Reversing systems redirect refrigerant so the heat exchangers exchange roles. Heating performance must be checked at its actual outdoor and delivery temperatures, including the equipment’s defrost behaviour where applicable. A cooling rating does not establish heating output.
Mechanisms and modulation
Rotary and scroll machines appear in packaged air-conditioning equipment; reciprocating, screw and centrifugal designs also serve refrigeration and chiller duties. Their use overlaps. Variable speed is a control option across mechanisms, not a guarantee of a particular seasonal saving. Compare the complete equipment over its expected load range.
Replacement in an existing system
Record the equipment model, compressor code, refrigerant, supply and control-board or drive identity. Verify compatibility with the original circuit and protection logic. Installation follows the specific equipment documentation; matching capacity alone does not make an aftermarket compressor an approved substitute.
Prepare a compressor request
Pressure conversion and pressure-ratio calculation · model selection unavailable
The pressure tool converts the supplied values and calculates the absolute discharge-to-suction pressure ratio. The request form records other requirements. Neither function selects a compressor, calculates capacity or confirms a refrigerant cycle, diagnosis or interchangeability.
For a technical review, identify the exact model and refrigerant, duty and rating conditions, electrical supply and control, oil, dimensions/connections, and the reason for replacement or service. Missing information remains unknown.
Selection / replacement · Service
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Absolute pressures and pressure ratio
Use suction and discharge pressures for the same stated operating condition and compatible measurement definitions. This is a pressure calculation; it does not check whether a compressor can operate at those pressures.
Method: 1 bar = 100 kPa; 1 MPa = 1000 kPa. Convert each input to kPa. For gauge pressure, p(abs) = p(gauge) + p(atm). For absolute pressure, use the entered value directly. r = p(discharge, abs) / p(suction, abs); r has no unit.
Both absolute pressures must be positive. Enter a positive absolute atmospheric pressure whenever either input is gauge. A negative gauge reading is allowed if its absolute pressure remains positive. Atmosphere is never assumed.
Example: suction 2 bar absolute and discharge 8 bar absolute give 200 kPa, 800 kPa and r = 4. The same result follows from 1 bar gauge and 7 bar gauge with an explicitly supplied atmosphere of 1 bar absolute.
The calculation does not provide cooling capacity, power, discharge temperature, an operating envelope, refrigerant/oil compatibility, diagnosis or a replacement model. Pressure sources, measurement uncertainty, operating stability and model limits remain unverified. Displayed results are rounded; extreme values outside finite numeric precision are rejected.