VARIOUS TYPES OF REFRIGERANTS USED IN AIR CONDITIONERS

 

VARIOUS TYPES OF REFRIGERANTS USED IN AIR CONDITIONERS

Why They Are Used | Engineering Principles | Environmental Impact | Safety

1. Introduction

Air conditioners do not normally use ordinary gases such as oxygen or nitrogen to produce cooling. They use special substances called refrigerants, which circulate through the refrigeration system to absorb heat from indoor air and release it outdoors. Although commonly called “AC gas,” refrigerants are often stored as liquids under pressure and change between liquid and vapour during operation.

The selection of a refrigerant depends on:

·         Cooling performance and electricity consumption.

·         Operating pressure and temperature.

·         Environmental impact, including ozone-depletion potential (ODP) and global warming potential (GWP).

·         Safety, including flammability and toxicity.

·         Compatibility with the compressor, lubricating oil, seals, piping and other components.

·         Cost, availability, equipment design and applicable regulations.

2. How Does Refrigerant Produce Cooling?

An air conditioner generally operates through a vapour-compression refrigeration cycle involving four main components:

1. Evaporator — absorbs heat: Low-pressure refrigerant evaporates in the indoor coil and absorbs heat from room air.

2. Compressor — raises pressure: The compressor draws in refrigerant vapour and raises its pressure and temperature.

3. Condenser — releases heat: The hot refrigerant rejects heat to outdoor air and condenses into a liquid.

4. Expansion device — reduces pressure: The refrigerant pressure falls, allowing it to enter the evaporator at a temperature suitable for absorbing heat again.

Key principle: Refrigerant does not create cold by itself. It transfers heat from inside the room to the outside environment.

3. Major Types of Refrigerants Used in Air Conditioners

R-22 (HCFC-22)

Chemical type/name: Chlorodifluoromethane

Typical applications: Older split, window and commercial AC systems.

Why it is used / key limitations: It offered good cooling performance and established technology. However, it depletes the ozone layer and has a high GWP of approximately 1,810 under commonly cited 100-year values. Its production and consumption have been phased out under the Montreal Protocol according to country-specific schedules.

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R-410A

Chemical type/name: Blend of R-32 and R-125

Typical applications: Many earlier modern residential split ACs, inverter systems and commercial units.

Why it is used / key limitations: It does not deplete the ozone layer and offers good cooling capacity, but operates at relatively high pressure and has a high GWP of approximately 2,088. Equipment must be designed specifically for it.

R-32

Chemical type/name: Difluoromethane

Typical applications: Many newer residential split and inverter AC models.

Why it is used / key limitations: It has good heat-transfer characteristics and a lower GWP—approximately 675—than R-410A. It is classified as mildly flammable (A2L), so equipment and servicing procedures must be appropriate for it.

R-290 (Propane)

Chemical type/name: Propane

Typical applications: Selected purpose-designed room AC and refrigeration equipment.

Why it is used / key limitations: It has excellent thermodynamic properties in suitable designs and a very low GWP of approximately 3. It is highly flammable (A3), making charge limits, equipment design, ventilation and applicable safety standards critical.

R-407C

Chemical type/name: Blend of HFC refrigerants

Typical applications: Selected commercial systems, chillers and compatible R-22 replacement applications.

Why it is used / key limitations: It has zero ozone-depletion potential. Its GWP is approximately 1,774. It exhibits temperature glide, so the charging and servicing procedure must suit the blend and equipment.

R-134a

Chemical type/name: 1,1,1,2-Tetrafluoroethane

Typical applications: Automotive AC systems, chillers and compatible refrigeration equipment.

Why it is used / key limitations: It has zero ozone-depletion potential and a GWP of approximately 1,430. It is not the standard refrigerant for most conventional modern domestic split ACs.

4. Comparison of Common AC Refrigerants

The following figures are approximate 100-year global warming potential (GWP) values commonly cited in refrigerant references. Values can vary by assessment basis and regulatory framework.

Refrigerant	Ozone depletion	Approx. GWP	Main consideration
R-22	Yes	1,810	Older refrigerant; ozone damage
R-410A	No	2,088	High GWP; high operating pressure
R-32	No	675	Lower GWP; mildly flammable
R-290	No	3	Very low GWP; highly flammable
R-407C	No	1,774	Blend; charging procedure matters
R-134a	No	1,430	Common in vehicle ACs and chillers

Zero ozone-depletion potential does not mean zero global warming impact. R-410A and R-32 do not deplete the ozone layer, but both are greenhouse gases. R-32 has a substantially lower GWP than R-410A.

5. Why Are Different Refrigerants Used?

Cooling capacity: The refrigerant must absorb sufficient heat in the evaporator and release it in the condenser. Its properties influence required compressor size and system design.

Energy efficiency: Refrigerant properties affect compressor work and heat transfer. Actual electricity consumption also depends on compressor design, heat exchangers, controls, installation and operating conditions.

Environmental protection: R-22 damages the ozone layer. Many newer refrigerants avoid ozone depletion, while lower-GWP options can reduce climate impact.

Safety and compatibility: Pressure, flammability, toxicity, oil compatibility and materials used in seals and pipes must all be considered.

6. Future Trends in AC Refrigerants

The industry is increasingly moving towards refrigerants with lower environmental impact. R-32 is an established lower-GWP option for many residential ACs. R-290 offers very low GWP in specifically designed equipment but requires strict flammability precautions. Certain newer HFO-based blends, including R-454B, are used or considered in selected markets and equipment categories. The appropriate choice depends on the application, regulations and manufacturer design.

7. Precautions During AC Servicing

1.     Check the outdoor unit nameplate to identify the specified refrigerant and factory charge.

2.     Never mix different refrigerants; mixing can cause incorrect operating conditions and servicing difficulties.

3.     Do not replace R-22 or R-410A with R-32 or R-290 unless the equipment is specifically approved and designed for that refrigerant.

4.     Identify and repair leaks rather than repeatedly adding refrigerant.

5.     Use gauges, recovery equipment, charging scales and tools rated for the refrigerant and application.

6.     Apply appropriate flammability precautions for R-32 and especially R-290, and use trained personnel.

8. Conclusion

Air-conditioning refrigerants have evolved from older ozone-depleting substances such as R-22 towards alternatives with improved environmental performance. R-410A became widely used because it does not deplete the ozone layer and offers good cooling performance, while R-32 provides similar application potential with a substantially lower GWP. R-290 offers a much lower GWP but requires special precautions because it is highly flammable.

Engineering takeaway: The correct refrigerant is the one specified for the equipment, balancing cooling performance, efficiency, environmental impact and safety. Correct installation, leak prevention and professional servicing are just as important as the refrigerant itself.

References

·         U.S. Environmental Protection Agency — Managing Refrigerant Emissions: https://www.epa.gov/ozone-layer-protection/managing-refrigerant-emissions

·         European Commission — Climate-friendly alternatives for air conditioning: https://climate.ec.europa.eu/areas-action/fluorinated-greenhouse-gases/climate-friendly-alternatives-f-gases/air-conditioning_en

·         U.S. EPA — Acceptable Refrigerants and Their Impacts: https://www.epa.gov/mvac/acceptable-refrigerants-and-their-impacts

Safety note: This article is for educational purposes. Refrigerant handling, recovery, charging and equipment modification should be performed by qualified personnel following manufacturer instructions and applicable standards.