To prevent untrained individuals from working with A2Ls, these refrigerants use left-handed threads on the recovery cylinders, a reversal from the thread pattern to which your students are accustomed. Although charging hoses are manufactured specifically for A2Ls, A2L hose adapters are available for use with HFC-rated hoses.

When working with A2Ls, it is also important to understand the components in the refrigerant detection system (RDS). Leaked refrigerant will displace oxygen, and if the system develops a leak, the RDS must warn the user before the A2L concentration reaches the lower flammability level (LFL). In the event of a leak or a power failure, the system disables itself and isolates the leak using a check valve and an electromechanical liquid-lined solenoid valve.

Identification and Recordkeeping

All A2L refrigerant cylinders — whether new or used for recovery — must be rated and identified by a red band. In addition, these tanks have a pressure relief valve rather than a rupture disc. Should the refrigerant get too hot, the pressure relief valve allows for a controlled release of some refrigerant.

In addition, the Environmental Protection Agency (EPA) and Underwriters Laboratories (UL) require a red tag on both indoor and outdoor units to indicate the use of A2Ls. UL requires special labeling to address the use of mildly flammable refrigerants, providing details about the equipment’s installation date and the square footage it can handle. This information is crucial in the event of a leak, as it helps determine appropriate mitigation strategies.

The EPA requires technicians to maintain a log detailing refrigerant purchases and usage. Cylinders should be tagged to indicate the type of refrigerant they contain. Businesses should also establish recovery stations where full recovery cylinders can be stored and then transported to reclamation centers, where the refrigerant can be transferred to another vessel for reuse.

Making a Choice

Instructors will need to explain how refrigerants are classified based on toxicity and flammability. Table 1 details the various refrigerants and the categories under which they fall. In addition, students should understand that the “R” stands for “refrigerant” and that any 400-Series refrigerant is a blend of at least two constituent gases.

Technicians will want to choose A2Ls with reduced glide, which is the temperature difference between the two gases found in the A2L during state changes. Because each of the A2L’s gases has its own chemical makeup, the gases won’t change state at the same time. Choosing a refrigerant with reduced glide helps ensure system reliability by lowering the risk of inconsistent temperatures and fractionation (the separation of a refrigerant mixture into its components). Students should consult the temperature-pressure chart specific to each A2L refrigerant to determine when it will be in its vapor state as opposed to its liquid state.

The refrigerants listed in Table 2 have a low GWP, particularly R-454C and R-455A, which have a GWP below 150. Until at least 2030, these refrigerants are approved by the EPA. For systems with a total charge greater than 200 pounds, these lower-GWP refrigerants are required. Systems with a charge that is less than 200 pounds can use refrigerants with a GWP under 300, so R-454A would be approved.

Other Considerations

Because A2Ls are classified as mildly flammable refrigerants, safety is an important area to emphasize. Fortunately, the personal protective equipment (PPE) and safety practices already familiar to those working with HFCs and HCFCs also apply to A2Ls. Technicians and support staff are responsible for acquiring proper protective gear, including safety shoes, glasses, and gloves to protect against frostbite. PPE has come a long way in recent years, and gear that is both comfortable and effective is readily available — and must always be worn!

Instructors may also want to briefly review the refrigerant cycle to remind their students that although the refrigerant has changed, the basic system design remains the same.

It is also important for students to understand the changing regulations. Beginning January 1, 2025, the EPA prohibited the use of refrigerants with GWP above 150 in new stand-alone refrigeration units for the retail food industry. Although the production of high-GWP refrigerants, such as R-404A, will no longer be allowed after 2025, supply houses may continue to offer these recovered and renewed high-GWP refrigerants, provided they have been placed in fresh containers and reclaimed for maintenance and service purposes.

Because industry mandates vary, it is essential to check the EPA website to find out exactly when changes are coming for a particular refrigeration system. Recognize that these regulations may differ based on refrigerant weight and industry type. In addition, individual states may impose further regulations, which can be explored here.

By covering the points above, students will be prepared to confidently work with A2Ls. This knowledge will help ensure a smooth transition toward refrigerants that will keep us cool without warming our planet.