R515B Refrigerant91.1/8.9 R1234ze(E)/R227ea · Solstice N15 · Nonflammable chiller & heat-pump blend
R515B is an azeotropic A1 blend of 91.1% R1234ze(E) and 8.9% R227ea. It was designed to provide R1234ze(E)-like thermodynamic behavior without the A2L classification of pure R1234ze(E). Its zero glide, A1 classification and current EPA GWP of 287 make it particularly relevant to chillers, heat pumps, high-ambient air conditioning and selected commercial refrigeration where nonflammability is a strong design requirement.
What is R515B refrigerant?
R515B takes an HFO-dominant refrigerant platform and adds a small R227ea fraction to create a nonflammable A1 azeotrope. It can replace R134a- or R1234ze(E)-class duty in purpose-designed systems, but its pressure and volumetric capacity are closer to R1234ze(E) than to R134a. It should not be assumed to deliver identical R134a capacity simply because both are A1.
R515B 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 | R515B | ASHRAE designation / Honeywell Solstice N15 |
| Nominal composition | R1234ze(E)/R227ea = 91.1/8.9 mass % | Honeywell |
| Refrigerant type | Azeotropic HFO/HFC blend | Zero glide |
| Molecular weight | ≈117.5 g/mol | Honeywell |
| Normal boiling point | ≈ −18.9°C | Honeywell |
| Critical temperature | ≈108.7°C | Honeywell |
| Critical pressure | ≈35.8 bar | Honeywell |
| ODP | 0 | Honeywell / EPA |
| 100-year GWP | 287 | EPA Technology Transitions |
| Safety classification | A1 | Nonflammable under ASHRAE classification |
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 R515B 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 chillers
EPA lists R515B as acceptable in new centrifugal chillers.
Positive-displacement chillers
EPA lists R515B for new equipment.
Heat pumps
Honeywell positions R515B for comfort heating/cooling and high-ambient heat-pump applications.
Industrial process air conditioning
EPA lists R515B as acceptable in new equipment.
Supermarket / remote condensing
EPA Notice 38 added R515B for new equipment in multiple commercial-refrigeration categories.
Data-center cooling
Honeywell lists data-center liquid cooling and room/precision AC among R515B application families.
Continue through the Refrigerant Replacements and Low-GWP Refrigerants hubs for broader selection context.
How 8.9% R227ea changes R1234ze(E) from A2L to A1
Pure R1234ze(E) is classified A2L. R515B contains 91.1% R1234ze(E) but adds 8.9% R227ea, producing a finished azeotropic blend classified A1.
The design tradeoff is higher GWP: R1234ze(E) itself has extremely low GWP, while R227ea is high-GWP. The weighted R515B value rises to EPA GWP 287.
This formulation is useful where designers want R1234ze(E)-like performance but cannot accept A2L refrigerant.
Zero glide simplifies phase-change behavior
R515B is azeotropic and Honeywell specifies zero temperature glide. That simplifies PT interpretation, evaporator/condenser temperature profiles and charging compared with strongly zeotropic blends.
Zero glide does not make R515B a pure compound; it remains a defined blend and should be identified/recovered as R515B.
This property also helps it behave as a practical 'business-as-usual' A1 refrigerant in chiller applications.
R515B is closer to R1234ze(E) than to R134a in pressure/capacity
Honeywell markets R515B as replacing R134a/R227ea/R124 in certain applications, but its normal boiling point and pressure characteristics closely resemble R1234ze(E).
Experimental heat-pump research finds R515B thermodynamic behavior closely follows R1234ze(E), which can mean lower volumetric capacity than R134a in the same compressor footprint.
A new or converted system should therefore verify compressor displacement, load margin and heat-exchanger performance rather than assuming equal R134a capacity.
R515B’s U.S. regulatory niche: A1 and below 300
EPA Technology Transitions uses GWP 287. That is below a 300 threshold but above 150.
EPA SNAP lists R515B in new chillers and industrial-process AC, and Notice 38 expanded new-equipment use into cold storage, commercial ice machines, food processing/dispensing, remote condensing and supermarket systems.
For retail-food categories that ultimately tighten to 150, R515B may still be transitional despite its relatively low GWP.
R515B vs R471A
The table highlights engineering differences rather than implying direct interchangeability.
| Characteristic | R515B | R471A |
|---|---|---|
| EPA GWP | 287 | 144 |
| Safety class | A1 | A1 |
| Phase behavior | Azeotropic, zero glide | Zeotropic |
| Primary platform | R1234ze(E)/R134a-class chillers & heat pumps | Medium-temp commercial refrigeration |
| Sub-150 | No | Yes |
| R227ea fraction | 8.9% | 4.3% |
| Typical pressure level | R1234ze(E)-like | Low vs R404A in published MT comparison |
R515B safety: A1 enables nonflammable system strategies, but concentration risks remain
R515B is A1, which can simplify chiller and heat-pump equipment design compared with A2L R1234ze(E). Large refrigerant inventories can still displace oxygen, liquid release can cause cold injury and hot-work decomposition remains a concern.
A1 benefit
Useful where lower-flammability refrigerants face code or siting constraints.
Large system charge
Chillers and heat pumps still need ventilation/pressure-relief planning.
Refrigerant identity
R515B should not be confused with R1234ze(E) even though most of the blend is that HFO.
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.
R515B refrigerant leak detection
Validate detector response to the finished blend
R515B does not currently have a dedicated public GasNose profile. Use fixed or portable refrigerant detection validated for the finished blend. For machinery-room monitoring, NDIR is commonly suitable for fluorinated refrigerant concentration monitoring; service detection needs higher leak-localization sensitivity.
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 R515B in 2026
United States
EPA lists R515B as acceptable for new centrifugal and positive-displacement chillers and new industrial-process air conditioning. Notice 38 expanded it to new cold-storage warehouses, commercial ice machines, refrigerated food processing/dispensing, remote condensing and supermarket systems. EPA Technology Transitions uses GWP 287, so eligibility still depends on whether the exact subsector limit is 700, 300 or 150.
European Union
R515B offers an A1 option below GWP 300, but it remains a fluorinated blend. It can fit some near-term EU thresholds while later equipment bans and the trend toward non-fluorinated refrigerants may limit long-term use in selected categories.
Is R515B being phased out?
R515B is not a high-GWP legacy refrigerant, but neither is it universally future-proof. It is strongest where nonflammability is essential and a 300-class GWP remains acceptable.
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 R515B?
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 R515B
“R515B is just R1234ze(E).”
It is a 91.1/8.9 azeotropic blend with different safety class and GWP.
“R515B GWP is always 293.”
Supplier literature uses older assessment values; current EPA Technology Transitions uses 287.
“A1 means it will match R134a capacity.”
Safety class does not determine capacity; R515B behaves more like R1234ze(E) in pressure/capacity.
“GWP below 300 fits every future refrigeration rule.”
Some categories move to 150 or lower/non-fluorinated requirements.
R515B refrigerant FAQ
Concise answers to common composition, retrofit, glide, safety and regulation questions.
What is R515B?
What is the EPA GWP of R515B?
Why do some sources show 293 or 299?
Is R515B flammable?
Does R515B have temperature glide?
Is R515B the same as R1234ze(E)?
Can R515B replace R134a?
Where is R515B used?
Does R515B meet a 150-GWP limit?
How should R515B leaks be detected?
R515B 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 R515B 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.