The Basics

What is a HFO?

HFOs (short for hydrofluoroolefins) are a family of refrigerants that were developed to replace older solutions like HCFCs and HFCs. HFOs have a much lower global warming potential (GWP) than legacy refrigerants and zero ozone depletion potential (ODP).

What are A2L Refrigerants?

A2L is a newly created classification on the ANSI/ASHRAE Standard 34 chart for classifying refrigerants. The chart is broken down between A and B and 1 through 3. "A" means lower toxicity, while 2 represents the flammability level. Previously, A2L was just A2. The "L" was added to the chart because the new refrigerant did not burn at a rate similar to an "A2" classified refrigerant, but there was a minimal flame propagation potential requiring a new classification. Typically, most A2L refrigerants are a blend of HFO and HFC refrigerants.

What is driving the adoption of A2L?

Future regulatory requirements on carbon emission reduction has stimulated the transition to lower GWP refrigerants. A2L refrigerants allow end users to transition to very low global warming potential solutions and are becoming increasingly used in new equipment, while providing favorable performance and operating efficiencies compared to the refrigerants they replace.

A2L Refrigerant Safety and Toxicity

A2L refrigerants have lower flammability and toxicity compared to other classifications — A = non-toxic, 2 = flammable, L = low burning velocity — making it the second-safest refrigerant category.

Which refrigerants are classed as A2L?

R–1234yf (Honeywell), R–1234ze (Daikin), R–454C (Chemours), R–455A (Honeywell), R–454A (Chemours), R–454B (Honeywell), R–447A, R–32, and R–452B (Honeywell). As with A1 refrigerants, some A2L refrigerants are pure, and others are blends. The pressure, temperature, and viscosity of A2L refrigerants vary by each refrigerant type.

Why was R-454 selected as the A2L refrigerant?

After evaluating several low-GWP alternatives on a variety of performance and market metrics, such as safety, capacity, efficiency, reliability, availability and longevity, ICP and Chemours and have determined R-454B to be the best-in-class low-GWP refrigerant. Its compatibility with plastic and elastomer materials and POE oil that will minimize working capital design changes and enable an easier transition from a R-410A platform.

Does R-454B contain propane?

There is no propane present in R-454B. It is a blended refrigerant much like R-410A, but it's made of 68.9% R-32 and 31.1% R-1234yf.

Storage & Transportation

Safe Storage Fire Regulations

The current ruling says that 20,000 lbs. of refrigerant can be stored in a single control area in an unconditioned warehouse without a sprinkler system. To increase storage capability, fire-rated walls can be installed to establish additional control areas, or a sprinkler system can be installed.

Transport For Service & Install Vehicles

The transport of A2L refrigerants will be similar to that of R-410A. There will be a need for a Class B dry powder fire extinguisher. Up to 440 pounds of refrigerant can be transported without need for DOT placards. Refrigerant can be transported in horizontal or vertical orientations. If you haven't yet, we encourage you to stay up-to-date on the latest courses available about R-454B including the Safety, Storage & Transportation course available.

Service, Maintenance & Installation

Tools & Procedures for Service, Mantenance, and Installation

Electronic tools will need to be verified to be spark-proof. Contact your tool manufacturer for this information. Saturation temperature visual aids will need to be updated. An inverted thread adaptor will need to be used on refrigerant cylinders only. Required procedures moving forward will be the best practice procedures that are in place for R-410A equipment.

New Equipment Rollout & Air Handler Compatibility

New equipment from our vendors should be available for orders starting in Q1 of 2024 and product launches will continue throughout the year. Equipment cannot be used for both refrigerants, but conversion kits may become available that will allow for the change from R-410A to R-454B.

Changeover Extension

Vendors are proposing a 1-year sell-through on what the government has defined as systems. We are expecting any changes that may come out of this conversation to occur around Q1 of 2024. The impact will be that there will be some relief on inventory management as we move into 2025.

Equipment: Dry Or Charged

The new equipment will come with charge in it much in the same way that current R-410A equipment comes today.

Phase In, Phase Out

R-410A Phaseout

The EPA has indicated that the transition dates for R-454B equipment will be January 1, 2025. Sell-through dates will vary by product.

Repairs & Replacements

R-410A Repairs & Replacement Parts

All R-410A equipment that is available today will have replacement parts available through replacement components for the intended service life of that product.

Line Set Replacement Requirements

Local building codes will regulate what will be needed for refrigerant runs. For high-rise buildings fire breaks will be required. From a system standpoint, you will not need to replace linesets with R-454B as it uses the same POE oil as R-410A as long as the lineset meets the current building code.

Evaporator Leak Replacement

Individual components will still be available to service R-410A equipment. If the entire coil needs to be changed, then with the current ruling from the EPA a replacement unit can be purchased "For service only".

Potential Residual Gas Danger

R-454B is not explosive, it is mildly flammable. The refrigerant is only capable of igniting when the concentrations in air are between the LFL of 11.3% and upper flammability limit of 23.6%. The refrigerant left absorbed in the oil is not capable of reaching these limits. Proper safety procedures will be to reclaim the refrigerant before service.

Efficiency and Global Warming Potential

High/Low Operating Pressures

The operating pressures of R-454B are slightly lower than those of R-410A.

R-454B SEER Rating

SEER ratings will be similar to those of R-410A.

R-410A and R-454B Both Containing R-32

R-410A was selected for use because it had zero ozone-depleting potential. After its introduction, Global Warming Potential became more readily understood. The driving factor of R-410A's high GWP is the R-125 constituent. R-454B replaces that with R-1234yf, which has a very small GWP.


Fan Coil Leak Detection

Vendors are providing full leak detection systems already installed on the equipment when shipped. Refer to vendors for specific information.

R-454B Coils/TXV's Condensing Unit Compatibility

Full furnace coils are not interchangeable. The refrigerant designed for the indoor coil must match that of the outdoor unit. Replacement Components will offer replacement coils only that can be used to replace either R-410A or R-454B coils.

Thread Patterns

Gauges will not have reverse threads. A thread adaptor will be needed for the cylinder.

R-454B. Not a Drop-In For R-410A

No, R-454B is not a drop-in replacement for R-410A. The pressures and temperatures are close to Puron, but they still require new compressors and expansion devices for ideal operation, therefore R-454B should not be used in R-410A systems.

Required Fittings

Mechanical fittings will be standard on all R-454B equipment.

Gas Furnace Replacement

The dissipation controls will intercept the signal from the thermostat. The furnace will not operate any differently than designed. The dissipation control will change the inputs into the furnace based on any need for dissipation. There will be no extra add on items needed to make changes to the furnace.

Reclaim Tanks

Rulings on reclaim came out from the EPA but were challenged in court and overturned. New rulings are in process. Best practice for reclaim tanks is to use only one type of refrigerant to avoid contamination. Linesets can be reused as long as they continue to meet local building codes. There isn't a need to replace them from a system standpoint as R-454B uses POE oil as well.


1 https://www.iccsafe.org/building-safety-journal/bsj-technical/code-changes-on-a2l-refrigerants
2 https://www.opteon.com/en/products/refrigerants/xl41
3 ICP Introduction to R-454B Launch Kit (pdf)
4 Introducción de ICP al Kit de Lanzamiento del R-454B (pdf)
5 https://www.epa.gov/climate-hfcs-reduction/background-hfcs-and-aim-act