R-421A
Binary HFC blend (58% R-125 / 42% R-134a). Branded as Choice R-421A by ICOR International. ASHRAE A1, GWP 2630. An R-22 retrofit option emphasizing simplicity (binary blend, mineral-oil compatible) over the lower-GWP alternatives.
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
Saturation values from CoolProp 7.2.0 R421A.mix. Operating pressure on a running system differs — see the operating-pressure references for in-use values.
R-421A PT chart PDF — printable saturation table
Looking for the R-421A PT chart PDF for shop reference? The complete pressure-temperature saturation table is below — every 1° increment from −40°F to 150°F (or to the refrigerant's critical temperature). Use the Print / Save as PDF button in the table header to download a clean, table-only PDF (the rest of the page is hidden from the print output). Important service temperatures (normal boiling point, freezing point of water, residential AC evap and condenser targets) are tinted and tagged in the table for at-a-glance shop reference.
R-421A PT Chart — Pressure-Temperature Saturation Table
1° increments · Source: CoolProp 7.2.0 / manufacturer datasheet · hvacptcharts.com
| Temp (°F) | Bubble (PSIG) | Dew (PSIG) | Glide (PSI) |
|---|---|---|---|
| -40°F | 0.5 | -3.0 | 3.5 |
| -39°F | 0.9 | -2.7 | 3.6 |
| -38°F | 1.3 | -2.3 | 3.6 |
| -37°F | 1.7 | -2.0 | 3.7 |
| -36°F | 2.1 | -1.6 | 3.8 |
| -35°F | 2.5 | -1.3 | 3.8 |
| -34°F | 3.0 | -0.9 | 3.9 |
| -33°F | 3.4 | -0.5 | 4.0 |
| -32°F | 3.9 | -0.1 | 4.0 |
| -31°F | 4.4 | 0.3 | 4.1 |
| -30°F | 4.8 | 0.7 | 4.2 |
| -29°F | 5.3 | 1.1 | 4.3 |
| -28°F | 5.8 | 1.5 | 4.3 |
| -27°F | 6.3 | 1.9 | 4.4 |
| -26°F | 6.8 | 2.4 | 4.5 |
| -25°F | 7.4 | 2.8 | 4.6 |
| -24°F | 7.9 | 3.3 | 4.6 |
| -23°F | 8.4 | 3.7 | 4.7 |
| -22°F | 9.0 | 4.2 | 4.8 |
| -21°F | 9.6 | 4.7 | 4.9 |
| -20°F | 10.1 | 5.2 | 4.9 |
| -19°F | 10.7 | 5.7 | 5.0 |
| -18°F | 11.3 | 6.2 | 5.1 |
| -17°F | 11.9 | 6.7 | 5.2 |
| -16°F | 12.5 | 7.3 | 5.3 |
| -15°F | 13.2 | 7.8 | 5.3 |
| -14°F | 13.8 | 8.4 | 5.4 |
| -13°F | 14.4 | 8.9 | 5.5 |
| -12°F | 15.1 | 9.5 | 5.6 |
| -11°F | 15.8 | 10.1 | 5.7 |
| -10°F | 16.5 | 10.7 | 5.8 |
| -9°F | 17.2 | 11.3 | 5.8 |
| -8°F | 17.9 | 11.9 | 5.9 |
| -7°F | 18.6 | 12.6 | 6.0 |
| -6°F | 19.3 | 13.2 | 6.1 |
| -5°F | 20.1 | 13.9 | 6.2 |
| -4°F | 20.8 | 14.5 | 6.3 |
| -3°F | 21.6 | 15.2 | 6.4 |
| -2°F | 22.4 | 15.9 | 6.5 |
| -1°F | 23.2 | 16.6 | 6.6 |
| 0°F | 24.0 | 17.3 | 6.6 |
| 1°F | 24.8 | 18.1 | 6.7 |
| 2°F | 25.6 | 18.8 | 6.8 |
| 3°F | 26.5 | 19.6 | 6.9 |
| 4°F | 27.4 | 20.3 | 7.0 |
| 5°F | 28.2 | 21.1 | 7.1 |
| 6°F | 29.1 | 21.9 | 7.2 |
| 7°F | 30.0 | 22.7 | 7.3 |
| 8°F | 30.9 | 23.6 | 7.4 |
| 9°F | 31.9 | 24.4 | 7.5 |
| 10°F | 32.8 | 25.3 | 7.6 |
| 11°F | 33.8 | 26.1 | 7.7 |
| 12°F | 34.8 | 27.0 | 7.8 |
| 13°F | 35.8 | 27.9 | 7.9 |
| 14°F | 36.8 | 28.8 | 8.0 |
| 15°F | 37.8 | 29.7 | 8.1 |
| 16°F | 38.8 | 30.7 | 8.2 |
| 17°F | 39.9 | 31.6 | 8.3 |
| 18°F | 40.9 | 32.6 | 8.4 |
| 19°F | 42.0 | 33.6 | 8.5 |
| 20°F | 43.1 | 34.6 | 8.6 |
| 21°F | 44.2 | 35.6 | 8.6 |
| 22°F | 45.4 | 36.6 | 8.8 |
| 23°F | 46.5 | 37.7 | 8.9 |
| 24°F | 47.7 | 38.7 | 9.0 |
| 25°F | 48.9 | 39.8 | 9.1 |
| 26°F | 50.1 | 40.9 | 9.2 |
| 27°F | 51.3 | 42.0 | 9.3 |
| 28°F | 52.5 | 43.2 | 9.4 |
| 29°F | 53.8 | 44.3 | 9.5 |
| 30°F | 55.0 | 45.5 | 9.6 |
| 31°F | 56.3 | 46.7 | 9.7 |
| 32°FH₂O freeze | 57.6 | 47.9 | 9.8 |
| 33°F | 59.0 | 49.1 | 9.9 |
| 34°F | 60.3 | 50.3 | 10.0 |
| 35°F | 61.6 | 51.6 | 10.1 |
| 36°F | 63.0 | 52.8 | 10.2 |
| 37°F | 64.4 | 54.1 | 10.3 |
| 38°F | 65.8 | 55.5 | 10.4 |
| 39°F | 67.3 | 56.8 | 10.5 |
| 40°FAC evap target | 68.7 | 58.1 | 10.6 |
| 41°F | 70.2 | 59.5 | 10.7 |
| 42°F | 71.7 | 60.9 | 10.8 |
| 43°F | 73.2 | 62.3 | 10.9 |
| 44°F | 74.7 | 63.7 | 11.0 |
| 45°F | 76.3 | 65.2 | 11.1 |
| 46°F | 77.8 | 66.6 | 11.2 |
| 47°F | 79.4 | 68.1 | 11.3 |
| 48°F | 81.0 | 69.6 | 11.4 |
| 49°F | 82.7 | 71.1 | 11.5 |
| 50°F | 84.3 | 72.7 | 11.7 |
| 51°F | 86.0 | 74.3 | 11.8 |
| 52°F | 87.7 | 75.8 | 11.9 |
| 53°F | 89.4 | 77.5 | 12.0 |
| 54°F | 91.2 | 79.1 | 12.1 |
| 55°F | 92.9 | 80.8 | 12.2 |
| 56°F | 94.7 | 82.4 | 12.3 |
| 57°F | 96.5 | 84.1 | 12.4 |
| 58°F | 98.3 | 85.8 | 12.5 |
| 59°F | 100.2 | 87.6 | 12.6 |
| 60°F | 102.0 | 89.4 | 12.7 |
| 61°F | 103.9 | 91.2 | 12.8 |
| 62°F | 105.8 | 93.0 | 12.9 |
| 63°F | 107.8 | 94.8 | 13.0 |
| 64°F | 109.8 | 96.7 | 13.1 |
| 65°F | 111.7 | 98.5 | 13.2 |
| 66°F | 113.7 | 100.5 | 13.3 |
| 67°F | 115.8 | 102.4 | 13.4 |
| 68°F | 117.8 | 104.3 | 13.5 |
| 69°F | 119.9 | 106.3 | 13.6 |
| 70°FRoom T | 122.0 | 108.3 | 13.7 |
| 71°F | 124.1 | 110.3 | 13.8 |
| 72°F | 126.3 | 112.4 | 13.9 |
| 73°F | 128.5 | 114.5 | 14.0 |
| 74°F | 130.7 | 116.6 | 14.1 |
| 75°F | 132.9 | 118.7 | 14.2 |
| 76°F | 135.2 | 120.9 | 14.3 |
| 77°F | 137.4 | 123.1 | 14.4 |
| 78°F | 139.8 | 125.3 | 14.5 |
| 79°F | 142.1 | 127.5 | 14.6 |
| 80°F | 144.4 | 129.8 | 14.7 |
| 81°F | 146.8 | 132.1 | 14.8 |
| 82°F | 149.2 | 134.4 | 14.8 |
| 83°F | 151.7 | 136.7 | 14.9 |
| 84°F | 154.1 | 139.1 | 15.0 |
| 85°F | 156.6 | 141.5 | 15.1 |
| 86°F | 159.1 | 143.9 | 15.2 |
| 87°F | 161.7 | 146.4 | 15.3 |
| 88°F | 164.3 | 148.9 | 15.4 |
| 89°F | 166.9 | 151.4 | 15.5 |
| 90°F | 169.5 | 153.9 | 15.6 |
| 91°F | 172.2 | 156.5 | 15.7 |
| 92°F | 174.8 | 159.1 | 15.7 |
| 93°F | 177.6 | 161.7 | 15.8 |
| 94°F | 180.3 | 164.4 | 15.9 |
| 95°FAHRI design ambient | 183.1 | 167.1 | 16.0 |
| 96°F | 185.9 | 169.8 | 16.1 |
| 97°F | 188.7 | 172.6 | 16.1 |
| 98°F | 191.6 | 175.3 | 16.2 |
| 99°F | 194.4 | 178.1 | 16.3 |
| 100°F | 197.4 | 181.0 | 16.4 |
| 101°F | 200.3 | 183.9 | 16.4 |
| 102°F | 203.3 | 186.8 | 16.5 |
| 103°F | 206.3 | 189.7 | 16.6 |
| 104°F | 209.4 | 192.7 | 16.7 |
| 105°F | 212.4 | 195.7 | 16.7 |
| 106°F | 215.5 | 198.7 | 16.8 |
| 107°F | 218.7 | 201.8 | 16.9 |
| 108°F | 221.8 | 204.9 | 16.9 |
| 109°F | 225.0 | 208.0 | 17.0 |
| 110°FTypical cond saturation | 228.3 | 211.2 | 17.1 |
| 111°F | 231.5 | 214.4 | 17.1 |
| 112°F | 234.8 | 217.7 | 17.2 |
| 113°F | 238.2 | 220.9 | 17.2 |
| 114°F | 241.5 | 224.3 | 17.3 |
| 115°F | 244.9 | 227.6 | 17.3 |
| 116°F | 248.4 | 231.0 | 17.4 |
| 117°F | 251.8 | 234.4 | 17.4 |
| 118°F | 255.3 | 237.8 | 17.5 |
| 119°F | 258.9 | 241.3 | 17.5 |
| 120°F | 262.4 | 244.9 | 17.6 |
| 121°F | 266.0 | 248.4 | 17.6 |
| 122°F | 269.7 | 252.0 | 17.7 |
| 123°F | 273.4 | 255.7 | 17.7 |
| 124°F | 277.1 | 259.3 | 17.7 |
| 125°F | 280.8 | 263.1 | 17.8 |
| 126°F | 284.6 | 266.8 | 17.8 |
| 127°F | 288.4 | 270.6 | 17.8 |
| 128°F | 292.3 | 274.4 | 17.8 |
| 129°F | 296.1 | 278.3 | 17.8 |
| 130°F | 300.1 | 282.2 | 17.9 |
| 131°F | 304.0 | 286.2 | 17.9 |
| 132°F | 308.1 | 290.2 | 17.9 |
| 133°F | 312.1 | 294.2 | 17.9 |
| 134°F | 316.2 | 298.3 | 17.9 |
| 135°F | 320.3 | 302.4 | 17.9 |
| 136°F | 324.4 | 306.6 | 17.9 |
| 137°F | 328.6 | 310.8 | 17.9 |
| 138°F | 332.9 | 315.0 | 17.9 |
| 139°F | 337.1 | 319.3 | 17.8 |
| 140°F | 341.4 | 323.6 | 17.8 |
| 141°F | 345.8 | 328.0 | 17.8 |
| 142°F | 350.2 | 332.4 | 17.8 |
| 143°F | 354.6 | 336.9 | 17.8 |
| 144°F | 359.1 | 341.4 | 17.7 |
| 145°F | 363.6 | 346.0 | 17.7 |
| 146°F | 368.2 | 350.6 | 17.6 |
| 147°F | 372.8 | 355.2 | 17.6 |
| 148°F | 377.4 | 359.9 | 17.5 |
| 149°F | 382.1 | 364.7 | 17.4 |
| 150°F | 386.9 | 369.5 | 17.4 |
| Temp (°C) | Bubble (kPa) | Dew (kPa) | Glide (kPa) |
|---|---|---|---|
| -40°C | 3 | -21 | 24 |
| -39°C | 8 | -17 | 25 |
| -38°C | 13 | -12 | 26 |
| -37°C | 19 | -8 | 27 |
| -36°C | 24 | -3 | 27 |
| -35°C | 30 | 2 | 28 |
| -34°C | 36 | 7 | 29 |
| -33°C | 42 | 12 | 30 |
| -32°C | 49 | 18 | 31 |
| -31°C | 55 | 23 | 32 |
| -30°C | 62 | 29 | 33 |
| -29°C | 69 | 35 | 34 |
| -28°C | 76 | 41 | 35 |
| -27°C | 84 | 48 | 36 |
| -26°C | 92 | 55 | 37 |
| -25°C | 100 | 62 | 38 |
| -24°C | 108 | 69 | 39 |
| -23°C | 116 | 76 | 40 |
| -22°C | 125 | 84 | 41 |
| -21°C | 134 | 92 | 42 |
| -20°C | 144 | 100 | 43 |
| -19°C | 153 | 109 | 44 |
| -18°C | 163 | 118 | 46 |
| -17°C | 173 | 127 | 47 |
| -16°C | 184 | 136 | 48 |
| -15°C | 195 | 146 | 49 |
| -14°C | 206 | 156 | 50 |
| -13°C | 217 | 166 | 51 |
| -12°C | 229 | 176 | 52 |
| -11°C | 241 | 187 | 54 |
| -10°C | 254 | 199 | 55 |
| -9°C | 266 | 210 | 56 |
| -8°C | 279 | 222 | 57 |
| -7°C | 293 | 234 | 59 |
| -6°C | 307 | 247 | 60 |
| -5°C | 321 | 260 | 61 |
| -4°C | 335 | 273 | 62 |
| -3°C | 350 | 287 | 64 |
| -2°C | 366 | 301 | 65 |
| -1°C | 381 | 315 | 66 |
| 0°CH₂O freeze | 397 | 330 | 67 |
| 1°C | 414 | 345 | 69 |
| 2°C | 431 | 361 | 70 |
| 3°C | 448 | 377 | 71 |
| 4°CAC evap target | 466 | 393 | 73 |
| 5°C | 484 | 410 | 74 |
| 6°C | 503 | 427 | 75 |
| 7°C | 522 | 445 | 76 |
| 8°C | 541 | 463 | 78 |
| 9°C | 561 | 482 | 79 |
| 10°C | 582 | 501 | 80 |
| 11°C | 602 | 521 | 82 |
| 12°C | 624 | 541 | 83 |
| 13°C | 646 | 561 | 84 |
| 14°C | 668 | 582 | 85 |
| 15°C | 691 | 604 | 87 |
| 16°C | 714 | 626 | 88 |
| 17°C | 738 | 649 | 89 |
| 18°C | 762 | 672 | 91 |
| 19°C | 787 | 695 | 92 |
| 20°C | 812 | 719 | 93 |
| 21°CRoom T | 838 | 744 | 94 |
| 22°C | 865 | 769 | 95 |
| 23°C | 892 | 795 | 97 |
| 24°C | 920 | 822 | 98 |
| 25°C | 948 | 849 | 99 |
| 26°C | 976 | 876 | 100 |
| 27°C | 1,006 | 904 | 101 |
| 28°C | 1,036 | 933 | 103 |
| 29°C | 1,066 | 962 | 104 |
| 30°C | 1,097 | 992 | 105 |
| 31°C | 1,129 | 1,023 | 106 |
| 32°C | 1,161 | 1,054 | 107 |
| 33°C | 1,194 | 1,086 | 108 |
| 34°C | 1,228 | 1,119 | 109 |
| 35°CAHRI design ambient | 1,262 | 1,152 | 110 |
| 36°C | 1,297 | 1,186 | 111 |
| 37°C | 1,333 | 1,221 | 112 |
| 38°C | 1,369 | 1,256 | 113 |
| 39°C | 1,406 | 1,292 | 114 |
| 40°C | 1,444 | 1,329 | 115 |
| 41°C | 1,482 | 1,366 | 116 |
| 42°C | 1,521 | 1,404 | 117 |
| 43°CTypical cond saturation | 1,561 | 1,443 | 117 |
| 44°C | 1,601 | 1,483 | 118 |
| 45°C | 1,642 | 1,523 | 119 |
| 46°C | 1,684 | 1,565 | 120 |
| 47°C | 1,727 | 1,607 | 120 |
| 48°C | 1,770 | 1,650 | 121 |
| 49°C | 1,814 | 1,693 | 121 |
| 50°C | 1,859 | 1,738 | 122 |
| 51°C | 1,905 | 1,783 | 122 |
| 52°C | 1,952 | 1,829 | 123 |
| 53°C | 1,999 | 1,876 | 123 |
| 54°C | 2,047 | 1,924 | 123 |
| 55°C | 2,096 | 1,973 | 123 |
| 56°C | 2,146 | 2,023 | 123 |
| 57°C | 2,197 | 2,074 | 123 |
| 58°C | 2,248 | 2,125 | 123 |
| 59°C | 2,301 | 2,178 | 123 |
| 60°C | 2,354 | 2,231 | 123 |
| 61°C | 2,409 | 2,286 | 123 |
| 62°C | 2,464 | 2,341 | 122 |
| 63°C | 2,520 | 2,398 | 122 |
| 64°C | 2,577 | 2,456 | 121 |
| 65°C | 2,635 | 2,514 | 120 |
Full saturation values at 1° increments — toggle between °F / PSIG and °C / kPa. Use Print / Save as PDF for laminated shop reference, or download the CSV / JSON below for use in other tools. R-421A PT chart data: CoolProp 7.2.0 (REFPROP-compatible Helmholtz EOS) or manufacturer datasheet, validated against AHRI Standard 700-2019.
At a glance
Chemistry
Lubricant compatibility
R-22 retrofit option. Mineral oil compatibility makes it a low-effort retrofit choice.
Blend composition
- R-12558.0%
- R-134a42.0%
Trade names
- Choice R-421AICOR International
Common applications
- R-22 retrofit (commercial AC, heat pumps)
- Medium-temperature refrigeration
Properties
- Boiling point (1 atm)-40.7°C / -41.2°F
- Critical point181.0°F at 554 PSIG
- Molar mass111.75 g/mol
- Temperature glide7.6°F
- ODP0
- GWP (AR5, 100-yr)2630
- GWP (AR6, 100-yr)2820
What is R-421A?
R-421A is a binary blend of 58% R-125 and 42% R-134a by mass, developed by ICOR International as an R-22 retrofit refrigerant. The binary composition (only two components) simplifies manufacturing compared to the 3- and 5-component R-22 retrofit blends, and the absence of a high-volatility R-32 component keeps the operating pressures close to R-22 across the envelope.
Compared to other "MO-compatible" R-22 retrofit options (R-417A, R-422A, R-422D, R-427A, R-438A), R-421A's lack of a hydrocarbon component means it relies on the HFC components themselves for mineral-oil miscibility — this works in practice for most R-22 retrofit applications but with somewhat less margin than the hydrocarbon-aided blends.
Where R-421A is used
- R-22 retrofit (residential AC, heat pumps, light commercial)
- Medium-temperature commercial refrigeration (R-22 retrofit)
- Existing R-22 equipment service where oil change is impractical
Regulatory & phase-down status
R-421A's GWP of 2630 is above the EPA AIM Act 700 threshold for new equipment. For new installations R-421A is not the choice; for R-22 retrofit work it remains commercially available.
The R-22 retrofit market itself is shrinking as the R-22 installed base ages out. New equipment installations use R-454B / R-32 / R-452B (residential AC) or R-448A / R-449A (commercial refrigeration) rather than refrigerant-only R-22 retrofits.
Service notes
Compatible with mineral oil (MO), alkylbenzene (AB), and POE oils. For R-22 retrofits the existing mineral oil typically stays in the system. R-421A has moderate temperature glide (~7-8°F at typical operating pressures); TXV operation may require retuning after retrofit.
Temperature glide
R-421A is a zeotropic blend: at constant pressure it boils across a temperature range rather than at a single point. This affects EXV sizing, charge measurement, and superheat measurement. Use the dew curve for superheat, bubble curve for subcooling.
Operating cycle
Phase-down timeline
No phase-down milestones documented for R-421A 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-421A replaces
Replacements for R-421A
Frequently asked
›How does R-421A compare to R-417A for R-22 retrofit?
Similar function (MO-compatible R-22 retrofit blends) with composition differences. R-421A is binary (R-125/R-134a only); R-417A is ternary (R-125/R-134a/R-600 — the hydrocarbon component aids miscibility). R-421A: GWP 2630, slightly closer to R-22 pressure envelope. R-417A: GWP 2346, hydrocarbon-aided mineral oil miscibility. Both are AIM-Act-affected and not for new equipment; the choice between them is largely distributor availability and contractor preference.
›What is the normal operating pressure of R-421A?
Close to R-22 across the envelope. At 95°F outdoor ambient on a residential AC retrofitted to R-421A, expect roughly 60-75 PSIG suction and 230-275 PSIG discharge — within a few PSI of R-22's operating envelope. The closer pressure match (vs higher-pressure R-22 retrofits) reduces stress on system components originally designed for R-22 pressures.
›What lubricant does R-421A use?
Compatible with mineral oil (MO), alkylbenzene (AB), and POE. For R-22 retrofits the existing mineral oil typically stays in the system. The hydrocarbon-free binary blend has somewhat less miscibility margin than hydrocarbon-aided R-22 retrofit blends (R-417A, R-422 series, R-438A) but works in practice for most retrofits.
›Does R-421A have temperature glide?
Yes — about 7-8°F at typical evaporator pressures. Use the dew curve for superheat measurement. TXV systems may require retuning after retrofit; EXV systems handle the glide automatically.
›Should I use R-421A or replace the R-22 equipment?
Same economic analysis as other R-22 retrofits. For equipment less than ~10 years old in good condition with no other major issues, R-421A retrofit can be cost-effective. For older equipment with multiple service-life concerns, full replacement with modern R-454B / R-32 equipment provides better long-term value through higher efficiency and longer expected service life.
›Is R-421A a near-azeotrope?
No — R-421A has meaningful temperature glide (~7-8°F at typical operating pressures), placing it in the zeotropic category. This is similar to other R-22 retrofit blends in this family (R-417A, R-422 series). For service work treat it as a zeotrope: dew curve for superheat, bubble curve for subcooling, charge by weight not by gauge.
›What is the GWP of R-421A?
2630 (IPCC AR5, mass-weighted from R-125 and R-134a components). This is higher than R-22's GWP of 1810. Like other R-22 retrofit HFC blends, the GWP exchange isn't favorable on a per-pound basis — the retrofit's value is operational continuity (no equipment replacement) rather than climate-impact reduction.