Summary of Commonly Used Refrigerants in HVAC Air Conditioning Systems

HVAC air conditioning system refrigerants can be divided into four categories based on their environmental attributes, usage scenarios, and upgrades : obsolete refrigerants, mainstream general-purpose refrigerants, new low-carbon alternatives, and natural and environmentally friendly refrigerants . Different refrigerants have significant differences in ODP (ozone depletion potential), GWP (global warming potential), safety, and operating parameters, and are suitable for different equipment scenarios such as residential and commercial central air conditioning and chiller units. The following is a detailed introduction to commonly used core models in the industry.

I. Eliminating existing refrigerants (used in older equipment and already discontinued or prohibited from production).

1. R22 (HCFC-22, difluorochloromethane)

It was once the most widely used traditional refrigerant in the HVAC field, belonging to the hydrochlorofluorocarbon (HCFC) class of refrigerants. It features high refrigeration efficiency, strong stability, low cost, and wide applicability, and has long been used in most HVAC systems, including residential split air conditioners, commercial central air conditioners , heat pump units , and industrial refrigeration equipment.

Environmental characteristics: ODP≠0, high GWP , which will damage the ozone layer and exacerbate the greenhouse effect. Currently, global production capacity has been phased out, and domestically, the installation of new units and the production of new materials are completely prohibited. Only the repair, recycling and reuse of old equipment are allowed. It is currently the most common refrigerant type for old air conditioners.

II. Current mainstream general-purpose refrigerants (standard configuration for new machines, with the highest market share)

1. R410A (mixed HFC refrigerant)

A non-azeotropic refrigerant mixture of R32 and R125 in a specific ratio is the first-generation core replacement for R22 and has been the mainstream standard for residential and small commercial air conditioners for the past decade. It boasts advantages such as zero ozone depletion, stable cooling efficiency, non-flammability, low toxicity, and stable operating conditions . Its system pressure is approximately 1.6 times higher than that of R22, resulting in superior heat exchange performance.

Applicable scenarios: Residential wall-mounted/floor-standing air conditioners, residential central air conditioning systems , and small commercial air-cooled units . The disadvantage is a relatively high GWP (Global Warming Potential) value and a significant greenhouse effect; it is currently being gradually replaced by low-carbon models.

2. R134a (HFC-134a, tetrafluoroethane)

Classic hydrofluorocarbon refrigerants, with an ODP of 0, are chemically stable, highly safe, and operate under moderate pressure, posing no risk of combustion or explosion. They are primarily suitable for low- to medium-pressure refrigeration systems and are not suitable for high-pressure, high-temperature conditions.

Applicable scenarios: Large commercial chillers , industrial HVAC refrigeration systems, vehicle air conditioners, and low-temperature commercial refrigeration equipment. It is a commonly used refrigerant in large central air conditioning water-cooled units .

3. R32 (difluoromethane)

Single-component HFC low-carbon refrigerant is currently the mainstream upgrade model for household air conditioners. Compared with R410A, it has a significantly lower GWP, higher cooling efficiency, requires less refrigerant charge, lower cost , excellent heat exchange efficiency, and outstanding energy-saving effect.

Precautions: It has slight flammability (A2L grade low flammability). Installation and maintenance must be carried out in accordance with regulations and open flames must be avoided. It is now widely used in new household air conditioners and small heat pump units .

III. New Low-Carbon Alternative Refrigerants (Industry-Related New Products, Low-Carbon Compliance)

1. R454B

This new low-GWP refrigerant blend is an A2L low-flammability, low-greenhouse-effect refrigerant with a GWP far lower than R410A, perfectly aligning with global refrigerant decarbonization policies. Its refrigeration performance is close to that of R410A, requiring no significant modifications to equipment structure, and can directly replace traditional high-GWP refrigerants.

Applicable scenarios: New commercial central air conditioning units , air-cooled heat pump units , and large-scale building HVAC systems. These are mainstream iterative models of high-end HVAC equipment in Europe, America, and China.

2. R407C

R22 is a transitional replacement refrigerant mixture with ODP=0, moderate GWP, and minimal temperature glide. It is suitable for retrofitting existing R22 systems without requiring large-scale replacement of equipment and piping. It is primarily used for refrigerant replacement retrofitting of older commercial central air conditioning and air-cooled units .

IV. Natural and environmentally friendly refrigerant (zero pollution, ultra-low GWP, preferred for green HVAC)

1. R290 (propane)

Natural hydrocarbon refrigerant, a purely natural working fluid, with a GWP of only 3 and ODP=0 , has virtually no environmental impact, making it one of the most environmentally friendly refrigerants currently available. It boasts extremely high refrigeration efficiency, excellent heat exchange performance, low cost, and is biodegradable.

Precautions: It is flammable (A3 grade), and has strict requirements for equipment sealing and installation and maintenance processes. It is mainly used in small split air conditioners and small commercial refrigeration equipment, and is the core green refrigerant for future civilian air conditioning.

2. R717 (ammonia)

It is a traditional natural working fluid with ODP=0 and GWP≈0, making it extremely environmentally friendly, highly efficient in refrigeration, cost-effective, and completely biodegradable.

Applicable scenarios: Large-scale industrial HVAC systems, cold storage, large-scale commercial chillers , and industrial heat pump systems. Disadvantages include some toxicity and corrosiveness; it cannot be used with copper piping equipment and is primarily used in industrial-grade professional HVAC applications.

3. R744 (Carbon Dioxide, CO₂)

It is a pure natural, fluorine-free refrigerant with zero ozone depletion, extremely low greenhouse effect, safety, non-toxicity, flame retardancy, and explosion-proof properties. It operates at extremely high pressures, requiring equipment with high pressure resistance. It is primarily used in ultra-low temperature heat pumps and commercial special HVAC systems ; it is rarely used in regular household air conditioners.

V. Comparison and Summary of Core Parameters of Mainstream Refrigerants

1. Existing stock: R22 (high ODP, high GWP, for maintenance only);

2. Mainstream for home use: R32, R410A (safe and stable, compatible with residential air conditioners);

3. Commercial large-scale: R134a, R454B (compatible with water chillers and building central air conditioning );

4. Green Future: R290, R717 (natural working fluids, low-carbon and environmentally friendly, and promoted by policies).