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Equipment Safety Considerations with A2L Refrigerants

Sept. 28, 2023
A2Ls—with their lower flammability classification—introduces new considerations for equipment safety, system design strategies and servicing best practices.

The stage is set for the adoption of A2L refrigerants in the commercial refrigeration sector. With lower-global warming potential (GWP) ratings below 300 and safety standards enabling higher refrigerant charges, A2Ls unlock a wide range of new application and equipment possibilities. For original equipment manufacturers (OEMs), system designers and service technicians, the use of A2Ls — with their lower flammability classification — introduces new considerations for equipment safety, system design strategies and servicing best practices    

Required Safety Measures for A2L Equipment & System Design

The Underwriters Laboratories (UL) 60335-2-89, 2nd edition product safety standard provides guidelines for the safe use of A2L and A3 refrigerants in commercial refrigeration by specifying requirements for equipment design, construction and installation. Per the UL 2-89 standard, these requirements are defined for two equipment types: self-contained units and remote systems.

Self-contained Units

Self-contained is defined as equipment consisting of a completely factory-assembled, factory-charged and factorytested refrigeration system, in which all refrigerant-containing parts are permanently connected at the factory. Essentially, the evaporator, condenser and compressor are all part of a packaged unit, which is a common design strategy for reachin display cases. Per the UL 2-89 standard, any self-contained system charged with more than 150 grams of refrigerant (the current charge limit for R-290) must follow its safe construction guidelines, which starts with its charge limit requirements. The UL 2-89 standard defines self-contained A2L charge limits based on whether the unit has a closed- or open-door (or drawer) design. Per its Annex CC construction and testing requirements, self-contained equipment charge limits are calculated as follows: • m1 = 8 m3 × LFL for closed-door (or drawer) designs • m1 = 13 m3 × LFL for open-door (or drawer) designs For example, since R-454C has an LFL of 0.291 kg/m3 , the refrigerant charges in closed and open cases are as follows: • 5.1 lbs. of R-454C in a closed case • 8.3 lbs. of R-454C in an open case These higher charge limits would greatly expand the cooling capacities found in current self-contained systems charged with R-290. Per the UL 2-89 standard, self-contained equipment that stays below the m1 charge and passes Annex CC testing, leak detection or additional risk mitigation is not required. Annex CC also requires OEMs to verify that their equipment will not exceed 50 percent of the refrigerant’s LFL in the event of a leak.

Remote Systems

The potential for using A2L refrigerants in remote, distributed systems — such as condensing units or mini scroll packs — would enable a new generation of lower-GWP, higher-capacity solutions for commercial refrigeration stakeholders. Because remote systems are largely assembled, charged and installed in the field, they will require adherence to additional safety requirements and considerations.

Allowable charge limits are proportionate to the application size and/or cooling requirements. UL 2-89 also provides guidance on how to calculate A2L charge limits in remote and/or fielderected systems:

 • m2 = 52 m3 × LFL
 • m3 = 260 m3 × LFL

Again, using R-454C as an example, the maximum allowable charge size would be 76.2 kilograms (166 pounds) and deliver up to 50–60 HP of cooling capacity. However, utilizing larger charges of A2L refrigerants in remote systems may require additional safety mitigation measures. Specific charge calculations and mitigation strategies will be based on the LFL of the A2L refrigerant, the area of the installation space and other relevant application conditions.

Remote condensing unit OEMs should follow the guidance found in UL 2-89 (2nd edition), under its Annex 101.DVU and Annex 101. DVG requirements. Systems should be designed to detect, isolate and disperse A2L refrigerant leaks via a combination of tools and controls:
 • Sensors within cases to detect leaks
 • Isolation and/or safety shut-off valves (SSOVs) in the refrigeration system to limit releasable charge
 • Electronic controls with A2L logic to perform required actions in the event of a leak — such as shutting off the compressor and/or other components
 • Ventilation and/or circulation fans within cases or walk-in units.

A2L Servicing Best Practices

When serving systems with A2L (or A3) refrigerants, technicians should be aware of some new safety considerations and remember to follow refrigerant management best practices. The first step is to identify which specific refrigerant is being used by looking for refrigerant labels on the system. Look for red markings on all service fittings and be sure to clearly mark them for the next technician who may service the system.

Next, it’s important to use specific tools that are designed for A2L use, such as gauges, vacuum pumps, and leak detection and refrigerant recovery machines. Compared to the process of repairing A1 refrigerant-based systems, A2Ls require three mandatory steps that are already considered industry-accepted best practices:
 1. Purge with nitrogen. 2. Evacuate the refrigerant. 3. Perform leak and pressure tests.

With A2Ls, it’s important to work in a well-ventilated area and deploy a continuous leak monitoring and detection system while servicing.

Finally, service technicians need to understand that legacy A1 refrigeration systems cannot be retrofitted for use with A2L refrigerants. Componentry, material compatibility and a variety of other construction factors must be taken into consideration. As such, make sure that all new A2L installations or remodels use A2L-qualified equipment. For more information about the safe application of A2L refrigerants, please visit the E360 content hub.

To learn more about the latest regulations impacting A2L adoption in U.S. commercial refrigeration, please visit the regulations page on our website,

Joe Summers is senior product manager for Copeland.  

Reprinted by permission. This information originally appeared in RSES Journal.