R-515B
Binary HFO/HFC azeotropic blend — 91.1% R-1234ze(E) and 8.9% R-227ea. Honeywell Solstice N15. ASHRAE A1 (non-flammable). GWP 287 — lower than R-515A (392) due to reduced R-227ea content. R-134a replacement for chillers and commercial refrigeration where A1 is required.
Lower toxicity (Occupational Exposure Limit ≥ 400 ppm). No flame propagation in air at standard atmospheric pressure and 60°C. R-134a, R-22, R-410A, R-404A, R-744 (CO2) are A1.
- Flammability
- None (no flame propagation)
- Toxicity
- Lower (OEL ≥ 400 ppm)
Classification per ANSI/ASHRAE Standard 34-2022. See full reference.
Saturation pressure-temperature curve
No PT chart in this build — see manufacturer datasheet. R-515Bhas a published PT chart in its manufacturer's technical datasheet (linked below). The chart has not been transcribed into this site's dataset. For service work, use the manufacturer's published PT chart directly — link below.
- manufacturer-datasheetHoneywell International Inc., Solstice N15 (R-515B) Technical Information.PT chart for R-515B (R-1234ze(E)/R-227ea 91.1/8.9 mass% azeotrope, A1 chiller refrigerant).https://www.honeywell-refrigerants.com/americas/
At a glance
Chemistry
Lubricant compatibility
Azeotrope. A1 classification (non-flammable). Lower GWP than R-515A. R-227ea content stays just above the minimum needed to maintain A1 classification.
Blend composition
- R-1234ze(E)91.1%
- R-227ea8.9%
Trade names
- Solstice N15Honeywell
Common applications
- Centrifugal chillers
- Medium-temperature commercial refrigeration
Properties
- Boiling point (1 atm)-18.9°C / -2.0°F
- Critical point227.5°F at 499 PSIG
- Molar mass117.50 g/mol
- Temperature glideNegligible (0.00°F)
- ODP0
- GWP (AR5, 100-yr)293
- GWP (AR6, 100-yr)311
What is R-515B?
R-515B is the more aggressive GWP-reduction sibling of R-515A. Both are R-1234ze(E)/R-227ea azeotropic blends; R-515B reduces the R-227ea content to 8.9% (vs R-515A's 12%), trimming GWP from 392 to 287 — a 27% reduction. The R-227ea content stays just above the threshold needed to maintain A1 (non-flammable) classification — pushing it lower would tip the blend into A2L territory.
The pressure envelope is essentially identical to R-515A (both are dominated by R-1234ze(E)) — both can be used in the same equipment with minimal redesign. The choice between R-515A and R-515B comes down to GWP-vs-margin preference: R-515A gives modest flammability margin headroom at the cost of higher GWP; R-515B optimizes for GWP reduction while staying just within A1.
The blend is azeotropic (effectively zero temperature glide) — handled in service like a pure refrigerant with no bubble/dew distinction required.
Where R-515B is used
- Centrifugal chillers (R-134a replacement, modern installations)
- Medium-temperature commercial refrigeration (R-134a replacement where A1 is required)
- Heat pumps (some commercial applications)
- Replacement for R-515A in installations seeking maximum GWP reduction within A1 classification
Regulatory & phase-down status
R-515B's GWP of 287 is below the EU F-Gas 750-GWP threshold for chillers and below the EPA AIM Act 700-GWP threshold for chiller equipment in the US — R-515B remains permitted for new chiller installations. For EU F-Gas 150-GWP applications (small split AC, some commercial refrigeration), R-515B is not compliant and pure R-1234ze(E) (A2L, GWP 7) is the alternative path.
Long-term trajectory: As EU F-Gas thresholds tighten further (the 2024 revision targets even lower thresholds for some applications by 2030), R-515B may face restrictions in some segments. For chillers specifically, the 750-GWP threshold provides substantial headroom for R-515B through current regulatory schedules.
Service notes
POE and PVE oils are compatible. Mineral oil is not used. A1 safety classification — no A2L procedures required.
Azeotropic behavior (zero glide) means R-515B is handled in service like a pure refrigerant. Single saturation temperature at any given pressure; no bubble/dew distinction needed for superheat or subcooling measurement. Charge by weight; do not partial-charge from a saturated vapor side of the cylinder (the standard rule for azeotropes and near-azeotropes).
Phase-down timeline
No phase-down milestones documented for R-515B in this build. This may mean: (a) no regulatory phase-down currently published; (b) the refrigerant has local regulatory schedules not yet transcribed into the site dataset; or (c) it is a specialty refrigerant outside the main regulatory frameworks. For authoritative current status, consult the EPA AIM Act allocations (40 CFR Part 84), EU F-Gas Regulation 517/2014 + 2024/573, and the relevant national implementations of the Kigali Amendment.
Global warming potential, in context
Medium-pressure centrifugal & screw chillers
Retrofit and replacement paths
R-515B replaces
Frequently asked
›Why choose R-515B over R-515A?
Lower GWP (287 vs 392) with essentially identical performance and the same A1 safety class. R-515B replaced R-515A in many new installations as Honeywell positioned it as the further-optimized version of the same blend concept. For new equipment specifications and most retrofit work, R-515B is the preferred current choice. R-515A remains available for installations where minor differences in flammability margin (R-515A has slightly more headroom on the A2L line) are preferred.
›Can R-515B be used in equipment originally designed for R-134a?
Generally yes, with retrofit procedure. The pressure envelope is within 5-7% of R-134a; capacity is typically within 5%. Procedure: recover R-134a; replace filter-drier; pull vacuum to 500 microns; charge R-515B by weight at 90-95% of original R-134a nameplate. Verify POE oil compatibility (most R-134a chillers run POE; verify per OEM if older equipment used alkylbenzene). Capacity and efficiency typically within R-515A's ranges.
›What's the temperature glide of R-515B?
Essentially zero (azeotropic). The 91.1/8.9 R-1234ze(E)/R-227ea composition is specifically chosen for azeotropic behavior — bubble and dew points coincide at typical operating pressures. This is a service advantage: no need to choose between bubble or dew curve for saturation measurements; treat R-515B like a pure refrigerant.
›What is the GWP of R-515B?
287 per IPCC AR5, mass-weighted from R-1234ze(E) (7) at 91.1% and R-227ea (3220) at 8.9%. The R-227ea component still dominates the GWP — it's 8.9% of mass but contributes ~99% of the GWP. Further GWP reduction below R-515B requires either pushing R-227ea content lower (and crossing into A2L flammability) or moving to a different chemistry entirely (pure R-1234ze(E), R-454C, etc.).
›Why does R-515B have R-227ea at all? Doesn't that defeat the low-GWP goal?
The R-227ea is necessary to suppress the flammability of pure R-1234ze(E) — without it, the refrigerant is A2L. Adding R-227ea is a deliberate tradeoff: small amounts of high-GWP fluid (R-227ea, GWP 3220) to achieve A1 classification of the overall blend. R-515B uses the minimum R-227ea needed to stay A1; pushing lower (R-515C at 4-5% R-227ea, hypothetically) would tip into A2L territory and lose the A1 service advantage.
›Is R-515B chemically stable?
Yes for chiller service envelopes. The blend is thermally stable to chiller condensing temperatures (≤160°F) and shows good long-term stability in sealed systems with proper POE oil and dry conditions. The azeotrope is composition-stable — fractionation in service is minimal because the two components have similar vapor pressures (the basis of the azeotropic behavior).