R450A Refrigerant42/58 R134a/R1234ze(E) · Solstice N13 · A1 R134a-class alternative
R450A is a near-azeotropic A1 blend of 42% R134a and 58% R1234ze(E). It was developed as a lower-GWP alternative to R134a for chillers, medium-temperature refrigeration and selected industrial or heat-pump applications. Its current EPA GWP of 601 fits the 700-GWP limit used for several U.S. chiller categories, but it remains a fluorinated transition blend and can deliver lower volumetric capacity than R134a in retrofit conditions.
What is R450A refrigerant?
R450A is a two-component R134a/R1234ze(E) refrigerant blend with A1 safety classification and small temperature glide. It targets many R134a-class applications while reducing GWP from 1,430 to 601 under the current EPA reference. A retrofit can be technically attractive, but cooling capacity, compressor map, charge, expansion device and OEM approval still require review.
R450A 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 | R450A | ASHRAE designation / Honeywell Solstice N13 |
| Nominal composition | R134a/R1234ze(E) = 42/58 mass % | NIST REFPROP / industry technical data |
| Refrigerant type | Near-azeotropic HFC/HFO blend | Two components |
| ODP | 0 | No ozone depletion |
| 100-year GWP | 601 | EPA Technology Transitions calculated value |
| Safety classification | A1 | Lower toxicity / no flame propagation |
| Normal boiling region | ≈ −23.4 to −22.8°C at 1 atm | Bubble/dew values show small glide |
| Temperature glide | Small, about 0.6 K near 1 atm | Near-azeotropic behavior |
| Critical temperature | ≈ 104.4°C | Published R450A property data |
| Typical lubricant | POE | Equipment/OEM requirements apply |
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 R450A 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.
Centrifugal / positive-displacement chillers
R134a-class chiller applications where an A1 lower-GWP option is preferred.
Medium-temperature commercial refrigeration
Display cabinets, coolers and other systems operating near R134a conditions.
Industrial process refrigeration
EPA SNAP lists R450A as acceptable for new and retrofit industrial-process refrigeration.
Ice rinks
EPA SNAP lists R450A as acceptable for new and retrofit ice-rink applications.
Heat pumps
R450A has been experimentally studied in water-to-water and moderately high-temperature heat-pump systems.
R134a retrofit / replacement studies
Research consistently treats R450A as a practical R134a alternative, though capacity can be lower.
Continue through the Refrigerant Replacements and Low-GWP Refrigerants hubs for broader selection context.
Why R450A remains A1 even though R1234ze(E) is A2L
R450A contains 58% R1234ze(E), which by itself is classified A2L, blended with 42% R134a. The finished R450A mixture is classified A1.
This is a reminder that refrigerant safety class belongs to the finished refrigerant, not to a simple average of component classifications.
Detection, servicing and equipment approval should therefore reference R450A rather than assuming the behavior of pure R1234ze(E).
R450A vs R134a: capacity and efficiency are not identical
Experimental work comparing R450A with R134a has repeatedly found that R450A can deliver somewhat lower cooling capacity in drop-in conditions while maintaining similar or slightly improved COP.
One published R134a/R450A experiment reported an average cooling-capacity reduction around 6%, with COP approximately similar or slightly higher under the tested conditions. This is test-specific evidence, not a universal performance guarantee.
The practical implication is that a retrofit should verify load margin and compressor operating map instead of choosing R450A from GWP alone.
Near-azeotropic behavior: small glide, but still a blend
R450A’s bubble and dew temperatures are close, with roughly 0.6 K separation near atmospheric pressure in published data. That is far smaller than blends such as R448A, R454C or R455A.
Even so, R450A is still a defined mixture. Liquid charging, refrigerant purity and correct PT data remain good service practice.
The low glide helps simplify heat-exchanger and control behavior relative to high-glide zeotropic blends.
Why R450A’s EPA GWP is 601 while older sources show ~547
Many older technical papers quote R450A GWP around 547 using IPCC AR5 component values. EPA Technology Transitions currently uses 601, calculated from the regulatory reference values used by the rule.
Both numbers can be correctly sourced to different assessment methodologies. For U.S. Technology Transitions compliance, the EPA 601 value is the relevant reference.
This difference is important because GWP threshold decisions should never use a value from the wrong assessment basis.
R450A vs R134a
The table highlights engineering differences rather than implying direct interchangeability.
| Characteristic | R450A | R134a |
|---|---|---|
| Type | Near-azeotropic HFC/HFO blend | Pure HFC |
| EPA GWP | 601 | 1,430 |
| Safety class | A1 | A1 |
| Temperature glide | Small (~0.6 K near 1 atm) | None |
| Cooling capacity in retrofit tests | Often somewhat lower | Baseline |
| Typical modern role | Lower-GWP A1 transition | Legacy installed base |
| U.S. 700-GWP chiller threshold | Below | Above |
R450A safety: A1 classification plus normal fluorinated-refrigerant controls
R450A is A1, so flammability is not the primary safety constraint. Large releases can still displace oxygen, liquid refrigerant can cause cold injury, and hot work can produce hazardous decomposition products. Chiller and machinery-room design should address charge, ventilation, pressure relief and monitoring.
Machinery-room leaks
Large chiller charges require concentration and ventilation planning.
Cold liquid
Use appropriate PPE for charging and recovery.
Decomposition
Recover refrigerant before flame or high-temperature work.
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.
R450A refrigerant leak detection
Validate detector response to the finished blend
Use R450A-compatible fixed or portable detection validated for the finished 42/58 blend. For chiller rooms, fixed infrared monitoring is a common approach; service leak detectors need high sensitivity at joints and components. GasNose currently lists R134a and R1234ze(E) individually, so the generic refrigerant-gas library is linked rather than inventing an R450A-specific GasNose URL.
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 R450A in 2026
United States
EPA’s current GWP value for R450A is 601. That is below the 700 limit applied to comfort-cooling chillers from January 1, 2025 and many industrial-process chiller categories from 2026/2028, subject to the exact subsector and compliance date. EPA SNAP also lists R450A as acceptable in industrial process refrigeration, ice rinks and several commercial refrigeration end uses. Other refrigeration subsectors use 150/300 limits and may not permit R450A for new systems.
European Union
R450A is lower-GWP than R134a but still contains a substantial HFC fraction and remains above 150. EU Regulation 2024/573 therefore limits its long-term role in categories moving toward sub-150 or non-fluorinated refrigerants.
Is R450A being phased out?
R450A can be a useful A1 transition refrigerant, particularly in R134a-class chillers and equipment where flammability avoidance is valuable. It is not automatically the final long-term solution in sectors with future GWP limits below 601.
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 R450A?
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 R450A
“R450A GWP is always 547.”
Older AR5-based literature often uses ~547; current EPA Technology Transitions uses 601.
“R450A is just R134a with the same capacity.”
Retrofit studies often show somewhat lower cooling capacity.
“Because it contains R1234ze(E), R450A must be A2L.”
The finished R450A blend is classified A1.
“Small glide means it is a pure refrigerant.”
R450A is still a two-component blend.
R450A refrigerant FAQ
Concise answers to common composition, retrofit, glide, safety and regulation questions.
What is R450A?
What is the EPA GWP of R450A?
Why do some sources say GWP 547?
Is R450A flammable?
Does R450A have temperature glide?
Can R450A replace R134a?
Is R450A used in chillers?
Does R450A fit the U.S. 700-GWP chiller limit?
Should R450A be charged as a blend?
How should R450A leaks be monitored?
R450A 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 R450A 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.