R438A (MO99) PT Chart
R-438A · MO99
Quinary HFC blend with two small hydrocarbon components (R-32/R-125/R-134a/R-600/R-601a 8.5/45/44.2/1.7/0.6 mass) — A1 safety, GWP 2265. R-22 retrofit refrigerant designed for mineral oil compatibility.
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 — datasheet table
Reproduced at datasheet resolution from the published Chemours Freon MO99 table (datasheet). Native pressure-indexed rows with irregular steps preserved — no interpolation to 1°F intervals in storage.
| Pressure (psig) | Bubble °F (saturated liquid) | Dew °F (saturated vapor) | Glide °F |
|---|---|---|---|
| -6.0 | -63.0 | -51.5 | 11.5 |
| -5.0 | -59.3 | -47.8 | 11.5 |
| -4.0 | -55.8 | -44.5 | 11.3 |
| -3.0 | -52.6 | -41.3 | 11.3 |
| -2.0 | -49.6 | -38.4 | 11.2 |
| -1.0 | -46.8 | -35.6 | 11.2 |
| 0.0 | -44.2 | -33.0 | 11.2 |
| 1.0 | -41.7 | -30.6 | 11.1 |
| 2.0 | -39.3 | -28.2 | 11.1 |
| 3.0 | -37.0 | -26.0 | 11.0 |
| 4.0 | -34.8 | -23.9 | 10.9 |
| 5.0 | -32.7 | -21.8 | 10.9 |
| 6.0 | -30.7 | -19.8 | 10.9 |
| 7.0 | -28.8 | -18.0 | 10.8 |
| 8.0 | -26.9 | -16.1 | 10.8 |
| 9.0 | -25.1 | -14.4 | 10.7 |
| 10.0 | -23.4 | -12.6 | 10.8 |
| 12.0 | -20.1 | -9.4 | 10.7 |
| 14.0 | -16.9 | -6.3 | 10.6 |
| 16.0 | -13.9 | -3.4 | 10.5 |
| 18.0 | -11.1 | -0.6 | 10.5 |
| 20.0 | -8.4 | 2.0 | 10.4 |
| 22.0 | -5.8 | 4.6 | 10.4 |
| 24.0 | -3.4 | 7.0 | 10.4 |
| 26.0 | -1.0 | 9.3 | 10.3 |
| 28.0 | 1.3 | 11.6 | 10.3 |
| 30.0 | 3.5 | 13.7 | 10.2 |
| 32.0 | 5.7 | 15.8 | 10.1 |
| 34.0 | 7.7 | 17.8 | 10.1 |
| 36.0 | 9.7 | 19.8 | 10.1 |
| 38.0 | 11.7 | 21.7 | 10.0 |
| 40.0 | 13.6 | 23.5 | 9.9 |
| 42.0 | 15.4 | 25.3 | 9.9 |
| 44.0 | 17.2 | 27.1 | 9.9 |
| 46.0 | 18.9 | 28.8 | 9.9 |
| 48.0 | 20.6 | 30.4 | 9.8 |
| 50.0 | 22.3 | 32.1 | 9.8 |
| 52.0 | 23.9 | 33.7 | 9.8 |
| 54.0 | 25.5 | 35.2 | 9.7 |
| 56.0 | 27.0 | 36.7 | 9.7 |
| 58.0 | 28.6 | 38.2 | 9.6 |
| 60.0 | 30.1 | 39.6 | 9.5 |
| 62.0 | 31.5 | 41.1 | 9.6 |
| 64.0 | 32.9 | 42.5 | 9.6 |
| 66.0 | 34.3 | 43.8 | 9.5 |
| 68.0 | 35.7 | 45.2 | 9.5 |
| 70.0 | 37.1 | 46.5 | 9.4 |
| 75.0 | 40.3 | 49.7 | 9.4 |
| 80.0 | 43.5 | 52.7 | 9.2 |
| 85.0 | 46.5 | 55.7 | 9.2 |
| 90.0 | 49.4 | 58.5 | 9.1 |
| 95.0 | 52.2 | 61.2 | 9.0 |
| 100.0 | 54.9 | 63.9 | 9.0 |
| 105.0 | 57.5 | 66.4 | 8.9 |
| 110.0 | 60.1 | 68.9 | 8.8 |
| 115.0 | 62.6 | 71.3 | 8.7 |
| 120.0 | 65.0 | 73.6 | 8.6 |
| 125.0 | 67.3 | 75.9 | 8.6 |
| 130.0 | 69.6 | 78.1 | 8.5 |
| 135.0 | 71.8 | 80.3 | 8.5 |
| 140.0 | 73.9 | 82.4 | 8.5 |
| 145.0 | 76.0 | 84.4 | 8.4 |
| 150.0 | 78.1 | 86.4 | 8.3 |
| 155.0 | 80.1 | 88.4 | 8.3 |
| 160.0 | 82.1 | 90.3 | 8.2 |
| 165.0 | 84.0 | 92.1 | 8.1 |
| 170.0 | 85.9 | 94.0 | 8.1 |
| 175.0 | 87.8 | 95.8 | 8.0 |
| 180.0 | 89.6 | 97.5 | 7.9 |
| 185.0 | 91.4 | 99.2 | 7.8 |
| 190.0 | 93.1 | 100.9 | 7.8 |
| 195.0 | 94.8 | 102.6 | 7.8 |
| 200.0 | 96.5 | 104.2 | 7.7 |
| 205.0 | 98.2 | 105.8 | 7.6 |
| 210.0 | 99.8 | 107.4 | 7.6 |
| 215.0 | 101.4 | 108.9 | 7.5 |
| 220.0 | 103.0 | 110.5 | 7.5 |
| 225.0 | 104.6 | 112.0 | 7.4 |
| 230.0 | 106.1 | 113.4 | 7.3 |
| 235.0 | 107.6 | 114.9 | 7.3 |
| 240.0 | 109.1 | 116.3 | 7.2 |
| 245.0 | 110.5 | 117.7 | 7.2 |
| 250.0 | 112.0 | 119.1 | 7.1 |
| 255.0 | 113.4 | 120.5 | 7.1 |
| 260.0 | 114.8 | 121.8 | 7.0 |
| 265.0 | 116.2 | 123.1 | 6.9 |
| 270.0 | 117.6 | 124.4 | 6.8 |
| 275.0 | 118.9 | 125.7 | 6.8 |
| 280.0 | 120.3 | 127.0 | 6.7 |
| 285.0 | 121.6 | 128.3 | 6.7 |
| 290.0 | 122.9 | 129.5 | 6.6 |
| 295.0 | 124.2 | 130.7 | 6.5 |
| 300.0 | 125.4 | 131.9 | 6.5 |
| 310.0 | 127.9 | 134.3 | 6.4 |
| 320.0 | 130.4 | 136.6 | 6.2 |
| 330.0 | 132.7 | 138.9 | 6.2 |
| 340.0 | 135.1 | 141.1 | 6.0 |
| 350.0 | 137.4 | 143.3 | 5.9 |
| 360.0 | 139.6 | 145.4 | 5.8 |
| 370.0 | 141.8 | 147.5 | 5.7 |
| 380.0 | 143.9 | 149.5 | 5.6 |
| 390.0 | 146.1 | 151.5 | 5.4 |
| 400.0 | 148.1 | 153.4 | 5.3 |
R-438A — 103 rows, -6 to 400 psig. Bubble = saturated liquid (use for subcooling); dew = saturated vapor (use for superheat on zeotropic blends). Runtime lookups for values between rows use linear interpolation and are marked as interpolated in the calculators.
At a glance
Chemistry
Lubricant compatibility
Hydrocarbon components aid miscibility with mineral oil. Marketed by Chemours (Freon MO99, originally DuPont ISCEON MO99) as an R-22 retrofit compatible with existing mineral oil or alkylbenzene in most systems — no oil change required for the majority of retrofits per the Chemours Freon MO99 Retrofit Guidelines. Some complex systems (liquid receivers, screw compressors, Trane 3-D or Danfoss SM scroll compressors) require ~20% POE addition.
Blend composition
- R-328.5%
- R-12545.0%
- R-134a44.2%
- R-6001.7%
- R-601a0.6%
Trade names
- Freon MO99Chemours
- ISCEON MO99DuPont (historical; brand transferred to Chemours 2015)
Common applications
- R-22 retrofit (commercial AC, refrigeration)
- Compatible with mineral oil systems
Properties
- Boiling point (1 atm)-42.3°C / -44.2°F
- Critical pointNo single point — blend critical locus
- Molar mass99.10 g/mol
- Temperature glide11.2°F
- ODP0
- GWP (AR5, 100-yr)2265
- GWP (AR6, 100-yr)2440
What is R-438A?
R-438A is a quinary HFC blend with two small hydrocarbon components: R-32 (8.5%) + R-125 (45%) + R-134a (44.2%) + R-600 (1.7%) + R-601a (0.6%) by mass [ashrae34]. The hydrocarbon components (R-600 n-butane and R-601a isopentane, totaling 2.3% by mass) serve the same role as R-422D's R-600a — bridging the polarity gap between HFC components and mineral oil to enable R-22 retrofit without oil change.
Honeywell markets R-438A as Genetron Performax LT. It is one of several Honeywell-branded R-22 retrofit alternatives alongside R-422D (Genetron MO99); both target the mineral-oil-compatible R-22 retrofit market with slightly different compositions optimized for different equipment categories.
Where R-438A is used
- R-22 retrofit in residential and light commercial AC
- Commercial refrigeration retrofit
- Heat pump retrofit from R-22
- Honeywell-aligned retrofit market segment
Regulatory & phase-down status
R-438A faces EPA AIM Act phase-down pressure due to its high GWP (2265) [aimact]. The blend is acceptable for R-22 retrofit but not specified for new equipment installations.
For service of existing R-438A retrofits, supply will continue indefinitely. New R-22 retrofit decisions in 2026 increasingly favor full equipment replacement (R-32 or R-454B) rather than refrigerant-only retrofit to R-438A or similar HFC blends.
Service notes
Mineral oil, alkylbenzene, or POE all compatible [ahri700]. R-438A can be charged into R-22 equipment without oil change. The 10°F glide affects service measurement — use dew curve for superheat, bubble curve for subcooling. A1 classification means no A2L procedures required.
Phase-down timeline
No phase-down milestones documented for R-438A 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
R-22 retrofit blends
Retrofit and replacement paths
R-438A replaces
Replacements for R-438A
Reading the R-438A PT chart
R-438A is zeotropic with ~10°F glide — PT chart shows bubble and dew curves. Use dew curve at suction pressure for superheat; bubble curve at discharge for subcooling.
At 70°F R-438A bubble is approximately 130 PSIG / dew approximately 115 PSIG (CoolProp 7.2.0). Pressure envelope close to R-22 — standard 500 PSI manifold gauges adequate.
Quinary blend — five components for optimized retrofit performance
R-438A's five-component composition is unusual — most HFC blends use 2-4 components. The five-component design (R-32 + R-125 + R-134a + R-600 + R-601a) was engineered to balance multiple requirements: A1 safety class, mineral oil compatibility, R-22 pressure-envelope match, capacity preservation, GWP minimization within those constraints.
The R-32 component (8.5%) provides some volumetric capacity. R-125 (45%) is the flammability suppressor. R-134a (44.2%) provides moderate-temperature capacity. R-600 (n-butane, 1.7%) and R-601a (isopentane, 0.6%) bridge the polarity gap for mineral oil miscibility.
GWP 2265 — lower than R-422D but still high
R-438A's GWP of 2265 is between R-22 (1810) and R-422D (2729). The lower R-125 content (45% vs R-422D's 65.1%) reduces the GWP burden compared to R-422D.
Both R-438A and R-422D face AIM Act phase-down pressure for new equipment specification. Modern low-GWP R-22 retrofit doesn't have a great solution — the mineral-oil-compatibility requirement essentially forces use of high-GWP HFC blends. The alternative is POE oil change (enabling R-407C use, GWP 1774) or full equipment replacement.
How to think about R-438A in 2026 and beyond
R-438A occupies the same narrowing niche as R-422D — service of existing R-22 retrofit installations. New R-22 retrofit decisions in 2026 increasingly favor full equipment replacement to R-32 or R-454B rather than refrigerant-only retrofit.
For service technicians, R-438A work is occasional — Honeywell-specified retrofits from the 2010s era. Service supply will continue indefinitely; pricing trends parallel other high-GWP HFC blends through the AIM Act schedule.
Frequently asked
›What is R-438A used for?
R-22 retrofit refrigerant for systems where oil change is undesirable. Honeywell markets R-438A as Genetron Performax LT, positioned alongside R-422D (Genetron MO99) for mineral-oil-compatible R-22 retrofit applications [honeywellgenetron].
The five-component composition is engineered for slightly different operating characteristics than R-422D — R-438A has lower R-125 content (45% vs R-422D's 65.1%) and includes R-32 (8.5%) for capacity contribution.
›What's R-438A's GWP?
2265 per IPCC AR5 — higher than R-22 (1810) but lower than R-422D (2729) [ipccar5]. R-438A faces AIM Act phase-down pressure for new equipment but remains acceptable for R-22 retrofit service.
›What's the difference between R-438A and R-422D?
Both are Honeywell HFC retrofit blends for R-22 with mineral oil compatibility. R-438A is quinary (5 components, including R-32 for capacity); R-422D is ternary (3 components, no R-32). R-438A has lower GWP (2265 vs 2729) and includes the R-32 component; R-422D's simpler composition is older (mid-2000s).
Performance is broadly similar — both target the same R-22 retrofit market with mineral-oil compatibility. The choice between them is typically driven by equipment OEM specification or distributor availability.
›Can I retrofit R-22 to R-438A without oil change?
Yes — the R-600 n-butane and R-601a isopentane hydrocarbon components (2.3% combined) enable mineral oil miscibility, allowing mineral oil retention through retrofit. Standard procedure: recover R-22, replace filter-drier, evacuate to 500 microns, recharge R-438A by weight to OEM nameplate.
›Why does R-438A contain hydrocarbons?
Mineral oil miscibility. HFC refrigerants (R-32, R-125, R-134a) are not miscible with mineral oil — without hydrocarbon addition, R-438A would have oil-return problems in R-22 equipment retaining mineral oil. The 2.3% combined R-600 + R-601a hydrocarbon content bridges the polarity gap, enabling acceptable oil-return behavior.
The hydrocarbon content is too small to change the A1 safety classification — the non-flammable HFC majority dominates.
›Is R-438A safe to handle?
ASHRAE class A1 — non-toxic and non-flammable [ashrae34]. Standard HFC service procedures apply.
›Should I use R-438A or R-422D for R-22 retrofit?
Both serve the same retrofit market. R-438A has lower GWP (2265 vs R-422D's 2729) and includes R-32 for slightly different performance characteristics. The choice is typically driven by Honeywell distributor recommendations and equipment OEM specifications.
In 2026, the better answer is often neither — full equipment replacement to R-32 or R-454B (sub-700 GWP) typically wins the retrofit-vs-replace economic comparison for older R-22 equipment.
Sources & citations
- [1]ASHRAE Standard 34-2022
- [2]IPCC AR5 (2014) Working Group I, Chapter 8, Table 8.A.1
- [3]EPA AIM Act — 40 CFR Part 84 Subpart BFinal Rule Oct 2021https://www.epa.gov/climate-hfcs-reduction
- [4]EPA SNAP — R-438A acceptable for R-22 retrofit
- [5]CoolProp 7.2.0
- [6]AHRI Standard 700-2019
- [7]Honeywell Genetron Performax LT (R-438A) Technical Information