R455A Refrigerant21.5/75.5/3 R32/R1234yf/CO₂ · Solstice L40X · Low-temperature refrigeration
R455A is a three-component A2L refrigerant containing 21.5% R32, 75.5% R1234yf and 3% R744 (CO₂) by mass. The small CO₂ fraction helps shape pressure/capacity behavior while also contributing to a very large temperature glide. With EPA GWP 146, R455A is aimed at new commercial and industrial refrigeration, condensing units, cold rooms, freezers, heat pumps and other equipment engineered for sub-150 A2L refrigerants.
What is R455A refrigerant?
R455A is unusual because it combines an HFC (R32), an HFO (R1234yf) and carbon dioxide. It is not a CO₂ transcritical refrigerant—the CO₂ fraction is only 3% by mass—but that component materially affects blend behavior. R455A’s low GWP and A2L classification make it a new-equipment option rather than a simple A1 retrofit gas.
R455A refrigerant properties
Use these values for research and screening. For equipment design, charging and compliance, use the exact supplier PT data, SDS, OEM documentation and regulation that governs the project.
| Property | Reference | Engineering / source note |
|---|---|---|
| Designation | R455A | ASHRAE designation / Honeywell Solstice L40X |
| Nominal composition | R32/R1234yf/R744 = 21.5/75.5/3 mass % | NIST REFPROP / published blend data |
| Refrigerant type | Zeotropic HFO/HFC/CO₂ blend | Three components |
| ODP | 0 | No ozone depletion |
| 100-year GWP | 146 | EPA Technology Transitions calculated value |
| Safety classification | A2L | Lower toxicity / lower flammability |
| Bubble point near 1 atm | ≈ −51.6°C | Published blend specifications |
| Dew point near 1 atm | ≈ −39.1°C | Published blend specifications |
| Endpoint glide near 1 atm | ≈ 12.5 K | Very high zeotropic glide |
| Critical temperature | Published values approximately low-to-mid 80s °C | Property source/model dependent for blend |
EPA Technology Transitions uses the values shown on this page. Older product literature may use IPCC AR4/AR5 or another assessment, so a different number is not automatically an error.
Where is R455A used?
Applications must be evaluated by system type, charge, compressor, heat exchanger, safety class and current regulation. The examples below describe recognized use contexts, not automatic approval for every installation.
Low-temperature commercial refrigeration
Freezers, cold rooms and plug-in/condensing-unit systems designed for A2L refrigerant.
Medium-temperature refrigeration
Food retail and commercial cooling with approved A2L components.
Cold-storage warehouses
Rule 26 lists R455A for new cold-storage systems subject to use conditions.
Supermarket & remote-condensing systems
R455A is SNAP-listed for new equipment subject to use conditions.
Industrial process refrigeration
EPA Rule 26 includes R455A for new IPR equipment subject to use conditions.
Commercial ice machines, ice rinks & heat pumps
R455A is used or evaluated across these A2L-capable equipment families.
Continue through the Refrigerant Replacements and Low-GWP Refrigerants hubs for broader selection context.
Why R455A contains 3% carbon dioxide
R455A’s 3% R744 fraction distinguishes it from the two-component R454C blend. The CO₂ component helps adjust capacity, pressure behavior and thermodynamic characteristics while the blend remains primarily R1234yf/R32.
This does not make an R455A system a transcritical CO₂ system. Equipment pressure architecture remains that of the specific R455A design rather than a conventional R744 transcritical booster system.
Service tools, PT charts and leak detectors must therefore be selected for R455A rather than pure R744.
R455A has one of the largest glides in this refrigerant group
Published nominal blend specifications show bubble and dew points around −51.6°C and −39.1°C near atmospheric pressure—an endpoint difference of roughly 12.5 K.
That large glide can be important in evaporator/condenser design, especially where counterflow heat exchangers can take advantage of temperature matching. It can also complicate control, defrost and field PT interpretation.
Technicians must use R455A bubble/dew data correctly for superheat, subcooling and commissioning.
Leak/fractionation behavior: what Honeywell’s test does and does not prove
Honeywell published an experimental R455A leak/top-off investigation in which the circulating composition stayed relatively stable through six repeated vapor-leak / liquid-top-off cycles.
That is useful evidence that the formulation can be robust under the tested procedure, but it should not be generalized into a rule that all real-world leaks can always be topped off without evaluation.
Leak location, liquid/vapor phase, system geometry, leakage fraction and service practice still matter. Follow the equipment and refrigerant supplier instructions.
R455A’s sub-150 regulatory position
EPA Technology Transitions assigns R455A GWP 146, and SNAP Rule 26 lists it in multiple new refrigeration end uses subject to A2L use conditions.
That gives R455A a stronger long-term regulatory position than R448A/R449A in sectors moving to 150-GWP limits.
However, sub-150 does not override safety requirements, and later EU restrictions can still favor non-fluorinated refrigerants in selected equipment categories.
R455A vs R454C
The table highlights engineering differences rather than implying direct interchangeability.
| Characteristic | R455A | R454C |
|---|---|---|
| Composition | R32/R1234yf/R744 = 21.5/75.5/3 | R32/R1234yf = 21.5/78.5 |
| EPA GWP | 146 | 146 |
| Safety class | A2L | A2L |
| CO₂ component | 3% | None |
| Endpoint glide near 1 atm | ≈ 12.5 K | ≈ 8.2 K |
| Primary role | Low/medium-temp commercial refrigeration | Low/medium-temp commercial refrigeration |
| Regulatory class | Sub-150 | Sub-150 |
R455A safety: A2L plus high-glide blend management
R455A is A2L. System safety must address leak concentration, ignition sources, charge, occupied volume, ventilation and service procedures. Its high glide adds a separate engineering/service consideration that is not captured by the A2L label.
Lower flammability
Use equipment, tools and service procedures intended for A2L refrigerants.
Blend-specific monitoring
A detector must be validated for R455A, not just R32 or R1234yf.
Temperature glide
Incorrect PT endpoint selection can create commissioning and diagnostic errors.
Actual risk depends on charge, release rate, pressure, room volume, ventilation, ignition sources, equipment construction, alarm logic and service condition.
See the Refrigerant Safety Guide for classification context.
R455A refrigerant leak detection
Validate detector response to the finished blend
Use fixed or portable detection specifically validated for R455A or an explicitly supported blend response. GasNose lists R455A in its public refrigerant directory and recommends blend-specific infrared or semiconductor detection depending on the monitoring objective. A2L equipment-mitigation sensors have different performance requirements from handheld service sniffers.
Portable service leak detectors, fixed area monitors, A2L mitigation sensors and refrigerant identifiers perform different functions. Define the alarm action and concentration range before selecting the technology.
Regulatory position of R455A in 2026
United States
EPA SNAP Rule 26 lists R455A as acceptable subject to use conditions for new commercial ice machines, industrial process refrigeration, cold storage warehouses, ice rinks, refrigerated food processing/dispensing equipment, stand-alone units, supermarket systems and remote condensing units. EPA Technology Transitions uses GWP 146, placing R455A below the 150 thresholds used in many long-term refrigeration categories.
European Union
R455A’s GWP below 150 improves its fit with many near-term EU F-gas thresholds. It remains a fluorinated blend, however, and Regulation (EU) 2024/573 includes later application-specific restrictions that can favor non-fluorinated solutions.
Is R455A being phased out?
R455A is positioned as a long-term low-GWP A2L refrigeration option in equipment designed for it. Its viability is stronger than high-GWP A1 retrofit blends under future threshold rules, but final refrigerant strategy still depends on equipment type, charge, safety standards and market regulation.
U.S. refrigeration limits differ by cold storage, supermarket, remote condensing, stand-alone product, industrial process and chiller category. A refrigerant may fit one pathway and fail another.
Use the Refrigerant Regulations Hub for regional research.
What should be compared with R455A?
Compare the real equipment pathway: retrofit vs new system, A1 vs A2L capability, GWP threshold, glide, compressor envelope, energy efficiency and service ecosystem.
Practical misconceptions about R455A
“R455A is basically CO₂ refrigerant.”
Only 3% of the blend is R744; the system is not a conventional transcritical CO₂ system.
“Large glide means the refrigerant is unstable.”
Glide is normal zeotropic phase behavior; the system must be engineered to use/manage it.
“Honeywell’s fractionation test means every leak can be topped off.”
The test is application evidence, not universal permission for every leak scenario.
“GWP 146 removes all regulatory and safety constraints.”
A2L use conditions, equipment listing, charge limits and future fluorinated-gas rules still apply.
R455A refrigerant FAQ
Concise answers to common composition, retrofit, glide, safety and regulation questions.
What is R455A?
What is the EPA GWP of R455A?
Is R455A flammable?
Why does R455A contain CO₂?
Is R455A a transcritical CO₂ refrigerant?
Does R455A have temperature glide?
Can R455A replace R404A directly?
Is R455A SNAP-approved in the U.S.?
Does every R455A system need a refrigerant sensor?
How is R455A detected?
R455A sources and further reading
This profile uses current EPA regulatory references plus refrigerant supplier, NIST, scientific and GasNose resources. Re-check the latest edition before design or compliance decisions.
Working with R455A or planning a refrigerant transition?
Compare GWP, safety class, temperature glide, equipment compatibility and regulatory lifetime before selecting a refrigerant.
Technical Notice: This page is for refrigerant research and general technical reference. Refrigerant suitability, permitted charge, equipment approval, leak mitigation, servicing procedures and regulatory compliance depend on the exact equipment, installation and jurisdiction. Always verify current manufacturer documentation, SDS, applicable standards and local regulations before selecting, replacing, charging or servicing a refrigerant.