R-422D
Ternary HFC blend with small hydrocarbon component (R-125/R-134a/R-600a 65.1/31.5/3.4 mass) marketed as Honeywell Genetron MO99 — A1 safety, GWP 2729. R-22 retrofit refrigerant designed for mineral-oil compatibility without oil change.
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 R422D.mix. Operating pressure on a running system differs — see the operating-pressure references for in-use values.
R-422D PT chart PDF — printable saturation table
Looking for the R-422D 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-422D 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 | 2.5 | -1.1 | 3.6 |
| -39°F | 3.0 | -0.8 | 3.7 |
| -38°F | 3.4 | -0.4 | 3.8 |
| -37°F | 3.9 | 0.0 | 3.9 |
| -36°F | 4.3 | 0.4 | 3.9 |
| -35°F | 4.8 | 0.8 | 4.0 |
| -34°F | 5.3 | 1.3 | 4.0 |
| -33°F | 5.8 | 1.7 | 4.1 |
| -32°F | 6.3 | 2.1 | 4.2 |
| -31°F | 6.8 | 2.6 | 4.2 |
| -30°F | 7.3 | 3.0 | 4.3 |
| -29°F | 7.9 | 3.5 | 4.4 |
| -28°F | 8.4 | 4.0 | 4.4 |
| -27°F | 9.0 | 4.4 | 4.5 |
| -26°F | 9.5 | 4.9 | 4.6 |
| -25°F | 10.1 | 5.4 | 4.7 |
| -24°F | 10.7 | 6.0 | 4.7 |
| -23°F | 11.3 | 6.5 | 4.8 |
| -22°F | 11.9 | 7.0 | 4.9 |
| -21°F | 12.5 | 7.6 | 4.9 |
| -20°F | 13.1 | 8.1 | 5.0 |
| -19°F | 13.8 | 8.7 | 5.1 |
| -18°F | 14.4 | 9.3 | 5.2 |
| -17°F | 15.1 | 9.8 | 5.2 |
| -16°F | 15.8 | 10.4 | 5.3 |
| -15°F | 16.4 | 11.1 | 5.4 |
| -14°F | 17.1 | 11.7 | 5.5 |
| -13°F | 17.9 | 12.3 | 5.5 |
| -12°F | 18.6 | 13.0 | 5.6 |
| -11°F | 19.3 | 13.6 | 5.7 |
| -10°F | 20.1 | 14.3 | 5.8 |
| -9°F | 20.8 | 15.0 | 5.8 |
| -8°F | 21.6 | 15.7 | 5.9 |
| -7°F | 22.4 | 16.4 | 6.0 |
| -6°F | 23.2 | 17.1 | 6.1 |
| -5°F | 24.0 | 17.8 | 6.2 |
| -4°F | 24.8 | 18.6 | 6.2 |
| -3°F | 25.6 | 19.3 | 6.3 |
| -2°F | 26.5 | 20.1 | 6.4 |
| -1°F | 27.4 | 20.9 | 6.5 |
| 0°F | 28.2 | 21.7 | 6.5 |
| 1°F | 29.1 | 22.5 | 6.6 |
| 2°F | 30.0 | 23.3 | 6.7 |
| 3°F | 31.0 | 24.2 | 6.8 |
| 4°F | 31.9 | 25.0 | 6.9 |
| 5°F | 32.9 | 25.9 | 7.0 |
| 6°F | 33.8 | 26.8 | 7.0 |
| 7°F | 34.8 | 27.7 | 7.1 |
| 8°F | 35.8 | 28.6 | 7.2 |
| 9°F | 36.8 | 29.5 | 7.3 |
| 10°F | 37.8 | 30.4 | 7.4 |
| 11°F | 38.9 | 31.4 | 7.5 |
| 12°F | 39.9 | 32.4 | 7.5 |
| 13°F | 41.0 | 33.4 | 7.6 |
| 14°F | 42.1 | 34.4 | 7.7 |
| 15°F | 43.2 | 35.4 | 7.8 |
| 16°F | 44.3 | 36.4 | 7.9 |
| 17°F | 45.4 | 37.5 | 8.0 |
| 18°F | 46.6 | 38.5 | 8.1 |
| 19°F | 47.8 | 39.6 | 8.1 |
| 20°F | 49.0 | 40.7 | 8.2 |
| 21°F | 50.1 | 41.8 | 8.3 |
| 22°F | 51.4 | 43.0 | 8.4 |
| 23°F | 52.6 | 44.1 | 8.5 |
| 24°F | 53.9 | 45.3 | 8.6 |
| 25°F | 55.1 | 46.5 | 8.6 |
| 26°F | 56.4 | 47.7 | 8.7 |
| 27°F | 57.7 | 48.9 | 8.8 |
| 28°F | 59.1 | 50.2 | 8.9 |
| 29°F | 60.4 | 51.4 | 9.0 |
| 30°F | 61.8 | 52.7 | 9.1 |
| 31°F | 63.1 | 54.0 | 9.2 |
| 32°FH₂O freeze | 64.5 | 55.3 | 9.3 |
| 33°F | 66.0 | 56.6 | 9.3 |
| 34°F | 67.4 | 58.0 | 9.4 |
| 35°F | 68.9 | 59.4 | 9.5 |
| 36°F | 70.3 | 60.8 | 9.6 |
| 37°F | 71.8 | 62.2 | 9.7 |
| 38°F | 73.4 | 63.6 | 9.8 |
| 39°F | 74.9 | 65.0 | 9.9 |
| 40°FAC evap target | 76.5 | 66.5 | 9.9 |
| 41°F | 78.0 | 68.0 | 10.0 |
| 42°F | 79.6 | 69.5 | 10.1 |
| 43°F | 81.2 | 71.0 | 10.2 |
| 44°F | 82.9 | 72.6 | 10.3 |
| 45°F | 84.5 | 74.2 | 10.4 |
| 46°F | 86.2 | 75.8 | 10.5 |
| 47°F | 87.9 | 77.4 | 10.5 |
| 48°F | 89.6 | 79.0 | 10.6 |
| 49°F | 91.4 | 80.7 | 10.7 |
| 50°F | 93.2 | 82.4 | 10.8 |
| 51°F | 94.9 | 84.1 | 10.9 |
| 52°F | 96.8 | 85.8 | 11.0 |
| 53°F | 98.6 | 87.5 | 11.0 |
| 54°F | 100.4 | 89.3 | 11.1 |
| 55°F | 102.3 | 91.1 | 11.2 |
| 56°F | 104.2 | 92.9 | 11.3 |
| 57°F | 106.1 | 94.8 | 11.4 |
| 58°F | 108.1 | 96.6 | 11.5 |
| 59°F | 110.0 | 98.5 | 11.5 |
| 60°F | 112.0 | 100.4 | 11.6 |
| 61°F | 114.1 | 102.4 | 11.7 |
| 62°F | 116.1 | 104.3 | 11.8 |
| 63°F | 118.2 | 106.3 | 11.9 |
| 64°F | 120.3 | 108.3 | 11.9 |
| 65°F | 122.4 | 110.3 | 12.0 |
| 66°F | 124.5 | 112.4 | 12.1 |
| 67°F | 126.7 | 114.5 | 12.2 |
| 68°F | 128.8 | 116.6 | 12.3 |
| 69°F | 131.1 | 118.7 | 12.3 |
| 70°FRoom T | 133.3 | 120.9 | 12.4 |
| 71°F | 135.6 | 123.1 | 12.5 |
| 72°F | 137.9 | 125.3 | 12.6 |
| 73°F | 140.2 | 127.5 | 12.6 |
| 74°F | 142.5 | 129.8 | 12.7 |
| 75°F | 144.9 | 132.1 | 12.8 |
| 76°F | 147.3 | 134.4 | 12.9 |
| 77°F | 149.7 | 136.8 | 12.9 |
| 78°F | 152.1 | 139.1 | 13.0 |
| 79°F | 154.6 | 141.5 | 13.1 |
| 80°F | 157.1 | 144.0 | 13.1 |
| 81°F | 159.6 | 146.4 | 13.2 |
| 82°F | 162.2 | 148.9 | 13.3 |
| 83°F | 164.8 | 151.4 | 13.3 |
| 84°F | 167.4 | 154.0 | 13.4 |
| 85°F | 170.0 | 156.6 | 13.5 |
| 86°F | 172.7 | 159.2 | 13.6 |
| 87°F | 175.4 | 161.8 | 13.6 |
| 88°F | 178.1 | 164.4 | 13.7 |
| 89°F | 180.9 | 167.1 | 13.8 |
| 90°F | 183.7 | 169.9 | 13.8 |
| 91°F | 186.5 | 172.6 | 13.9 |
| 92°F | 189.3 | 175.4 | 13.9 |
| 93°F | 192.2 | 178.2 | 14.0 |
| 94°F | 195.1 | 181.1 | 14.0 |
| 95°FAHRI design ambient | 198.0 | 183.9 | 14.1 |
| 96°F | 201.0 | 186.8 | 14.2 |
| 97°F | 204.0 | 189.8 | 14.2 |
| 98°F | 207.0 | 192.8 | 14.3 |
| 99°F | 210.1 | 195.8 | 14.3 |
| 100°F | 213.2 | 198.8 | 14.4 |
| 101°F | 216.3 | 201.9 | 14.4 |
| 102°F | 219.4 | 205.0 | 14.5 |
| 103°F | 222.6 | 208.1 | 14.5 |
| 104°F | 225.8 | 211.3 | 14.6 |
| 105°F | 229.1 | 214.5 | 14.6 |
| 106°F | 232.4 | 217.7 | 14.6 |
| 107°F | 235.7 | 221.0 | 14.7 |
| 108°F | 239.0 | 224.3 | 14.7 |
| 109°F | 242.4 | 227.7 | 14.7 |
| 110°FTypical cond saturation | 245.8 | 231.1 | 14.8 |
| 111°F | 249.3 | 234.5 | 14.8 |
| 112°F | 252.8 | 237.9 | 14.8 |
| 113°F | 256.3 | 241.4 | 14.9 |
| 114°F | 259.8 | 244.9 | 14.9 |
| 115°F | 263.4 | 248.5 | 14.9 |
| 116°F | 267.0 | 252.1 | 14.9 |
| 117°F | 270.7 | 255.7 | 15.0 |
| 118°F | 274.4 | 259.4 | 15.0 |
| 119°F | 278.1 | 263.1 | 15.0 |
| 120°F | 281.9 | 266.9 | 15.0 |
| 121°F | 285.7 | 270.6 | 15.0 |
| 122°F | 289.5 | 274.5 | 15.0 |
| 123°F | 293.4 | 278.3 | 15.0 |
| 124°F | 297.3 | 282.3 | 15.0 |
| 125°F | 301.2 | 286.2 | 15.1 |
| 126°F | 305.2 | 290.2 | 15.0 |
| 127°F | 309.3 | 294.2 | 15.0 |
| 128°F | 313.3 | 298.3 | 15.0 |
| 129°F | 317.4 | 302.4 | 15.0 |
| 130°F | 321.6 | 306.5 | 15.0 |
| 131°F | 325.7 | 310.7 | 15.0 |
| 132°F | 329.9 | 315.0 | 15.0 |
| 133°F | 334.2 | 319.3 | 14.9 |
| 134°F | 338.5 | 323.6 | 14.9 |
| 135°F | 342.8 | 328.0 | 14.9 |
| 136°F | 347.2 | 332.4 | 14.9 |
| 137°F | 351.6 | 336.8 | 14.8 |
| 138°F | 356.1 | 341.3 | 14.8 |
| 139°F | 360.6 | 345.9 | 14.7 |
| 140°F | 365.1 | 350.5 | 14.6 |
| 141°F | 369.7 | 355.1 | 14.6 |
| 142°F | 374.4 | 359.8 | 14.5 |
| 143°F | 379.0 | 364.6 | 14.4 |
| 144°F | 383.8 | 369.4 | 14.4 |
| 145°F | 388.5 | 374.2 | 14.3 |
| 146°F | 393.3 | 379.1 | 14.2 |
| 147°F | 398.2 | 384.1 | 14.1 |
| 148°F | 403.1 | 389.0 | 14.0 |
| 149°F | 408.0 | 394.1 | 13.9 |
| 150°F | 413.0 | 399.2 | 13.8 |
| Temp (°C) | Bubble (kPa) | Dew (kPa) | Glide (kPa) |
|---|---|---|---|
| -40°C | 17 | -8 | 25 |
| -39°C | 23 | -3 | 26 |
| -38°C | 29 | 2 | 27 |
| -37°C | 34 | 7 | 28 |
| -36°C | 41 | 12 | 28 |
| -35°C | 47 | 18 | 29 |
| -34°C | 53 | 23 | 30 |
| -33°C | 60 | 29 | 31 |
| -32°C | 67 | 35 | 32 |
| -31°C | 75 | 42 | 33 |
| -30°C | 82 | 48 | 34 |
| -29°C | 90 | 55 | 34 |
| -28°C | 98 | 62 | 35 |
| -27°C | 106 | 70 | 36 |
| -26°C | 114 | 77 | 37 |
| -25°C | 123 | 85 | 38 |
| -24°C | 132 | 93 | 39 |
| -23°C | 141 | 101 | 40 |
| -22°C | 151 | 110 | 41 |
| -21°C | 161 | 119 | 42 |
| -20°C | 171 | 128 | 43 |
| -19°C | 182 | 138 | 44 |
| -18°C | 192 | 147 | 45 |
| -17°C | 203 | 157 | 46 |
| -16°C | 215 | 168 | 47 |
| -15°C | 227 | 179 | 48 |
| -14°C | 239 | 190 | 49 |
| -13°C | 251 | 201 | 50 |
| -12°C | 264 | 213 | 51 |
| -11°C | 277 | 225 | 52 |
| -10°C | 290 | 237 | 53 |
| -9°C | 304 | 250 | 54 |
| -8°C | 318 | 263 | 55 |
| -7°C | 333 | 276 | 56 |
| -6°C | 347 | 290 | 57 |
| -5°C | 363 | 304 | 58 |
| -4°C | 378 | 319 | 60 |
| -3°C | 395 | 334 | 61 |
| -2°C | 411 | 349 | 62 |
| -1°C | 428 | 365 | 63 |
| 0°CH₂O freeze | 445 | 381 | 64 |
| 1°C | 463 | 398 | 65 |
| 2°C | 481 | 415 | 66 |
| 3°C | 500 | 433 | 67 |
| 4°CAC evap target | 519 | 450 | 68 |
| 5°C | 538 | 469 | 69 |
| 6°C | 558 | 488 | 70 |
| 7°C | 578 | 507 | 71 |
| 8°C | 599 | 527 | 72 |
| 9°C | 621 | 547 | 73 |
| 10°C | 642 | 568 | 75 |
| 11°C | 665 | 589 | 75 |
| 12°C | 687 | 611 | 77 |
| 13°C | 711 | 633 | 78 |
| 14°C | 734 | 656 | 79 |
| 15°C | 759 | 679 | 80 |
| 16°C | 784 | 703 | 81 |
| 17°C | 809 | 727 | 82 |
| 18°C | 835 | 752 | 83 |
| 19°C | 861 | 778 | 84 |
| 20°C | 888 | 804 | 85 |
| 21°CRoom T | 916 | 831 | 86 |
| 22°C | 944 | 858 | 86 |
| 23°C | 973 | 886 | 87 |
| 24°C | 1,002 | 914 | 88 |
| 25°C | 1,032 | 943 | 89 |
| 26°C | 1,063 | 972 | 90 |
| 27°C | 1,094 | 1,003 | 91 |
| 28°C | 1,125 | 1,034 | 92 |
| 29°C | 1,158 | 1,065 | 93 |
| 30°C | 1,191 | 1,097 | 94 |
| 31°C | 1,224 | 1,130 | 94 |
| 32°C | 1,259 | 1,164 | 95 |
| 33°C | 1,294 | 1,198 | 96 |
| 34°C | 1,329 | 1,233 | 96 |
| 35°CAHRI design ambient | 1,365 | 1,268 | 97 |
| 36°C | 1,402 | 1,305 | 98 |
| 37°C | 1,440 | 1,342 | 99 |
| 38°C | 1,478 | 1,379 | 99 |
| 39°C | 1,517 | 1,418 | 100 |
| 40°C | 1,557 | 1,457 | 100 |
| 41°C | 1,598 | 1,497 | 101 |
| 42°C | 1,639 | 1,538 | 101 |
| 43°CTypical cond saturation | 1,681 | 1,579 | 102 |
| 44°C | 1,724 | 1,621 | 102 |
| 45°C | 1,767 | 1,664 | 103 |
| 46°C | 1,811 | 1,708 | 103 |
| 47°C | 1,856 | 1,753 | 103 |
| 48°C | 1,902 | 1,799 | 103 |
| 49°C | 1,949 | 1,845 | 104 |
| 50°C | 1,996 | 1,892 | 104 |
| 51°C | 2,044 | 1,941 | 104 |
| 52°C | 2,093 | 1,990 | 104 |
| 53°C | 2,143 | 2,040 | 104 |
| 54°C | 2,194 | 2,091 | 104 |
| 55°C | 2,246 | 2,143 | 103 |
| 56°C | 2,298 | 2,195 | 103 |
| 57°C | 2,352 | 2,249 | 103 |
| 58°C | 2,406 | 2,304 | 102 |
| 59°C | 2,461 | 2,360 | 102 |
| 60°C | 2,518 | 2,417 | 101 |
| 61°C | 2,575 | 2,475 | 100 |
| 62°C | 2,633 | 2,533 | 99 |
| 63°C | 2,692 | 2,594 | 98 |
| 64°C | 2,752 | 2,655 | 97 |
| 65°C | 2,813 | 2,717 | 96 |
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-422D 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
Mineral-oil-compatible R-22 retrofit. Popular medium-temperature drop-in option for commercial AC where oil change is impractical.
Blend composition
- R-12565.1%
- R-134a31.5%
- R-600a3.4%
Trade names
- ISCEON MO29Chemours
Common applications
- R-22 retrofit (medium-temperature commercial AC)
- Heat pumps (legacy retrofit)
Properties
- Boiling point (1 atm)-43.4°C / -46.1°F
- Critical pointNo single point — blend critical locus
- Molar mass109.94 g/mol
- Temperature glide6.7°F
- ODP0
- GWP (AR5, 100-yr)2729
- GWP (AR6, 100-yr)2930
What is R-422D?
R-422D is a ternary HFC blend with a small hydrocarbon (R-600a isobutane) component: R-125 (65.1%) + R-134a (31.5%) + R-600a (3.4%) by mass [ashrae34]. The R-600a addition serves a specific functional purpose: improving miscibility with mineral oil, enabling R-22 retrofit without oil change.
Honeywell markets R-422D as Genetron MO99 — the "MO" referring to "mineral oil" compatibility. The 3.4% R-600a isn't enough to change the A1 safety classification (R-600a is A3 individually but the blend's non-flammable HFC majority dominates), but it's enough to enable R-22 mineral oil retention through retrofit [honeywellgenetron].
Where R-422D is used
- R-22 retrofit in residential and light commercial AC where oil change is undesirable
- R-22 retrofit in commercial refrigeration applications
- Service refrigerant for existing R-22 equipment
- Heat pump retrofit from R-22
Regulatory & phase-down status
R-422D faces EPA AIM Act phase-down pressure due to its high GWP (2729) [aimact]. The blend is acceptable for R-22 retrofit but not specified for new equipment installations.
For service of existing R-22 retrofits (R-22 systems converted to R-422D in the 2005-2020 era), R-422D supply will continue indefinitely under EPA Section 608 rules. Pricing trends parallel other high-GWP HFC blends through the AIM Act production schedule.
Service notes
Mineral oil, alkylbenzene, or POE all compatible — the primary retrofit advantage [ahri700]. R-422D can be charged into R-22 equipment without oil change when the existing mineral oil is in good condition.
The 8°F glide affects service measurement — use dew curve for superheat, bubble curve for subcooling. A1 classification means no A2L procedures required.
Temperature glide
R-422D 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-422D 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-422D replaces
Replacements for R-422D
Reading the R-422D PT chart
R-422D's PT chart shows two curves (bubble and dew) — the blend is zeotropic with approximately 8°F glide. Use dew curve at suction pressure for superheat measurement; use bubble curve at discharge pressure for subcooling.
The pressure envelope is close to R-22. At 70°F R-422D bubble is approximately 132 PSIG / dew approximately 118 PSIG (CoolProp 7.2.0); compare to R-22 at 70°F (121 PSIG). Standard 500 PSI manifold gauges handle R-422D — same gauge equipment as R-22 service works for R-422D retrofit.
Ternary blend with hydrocarbon for mineral oil miscibility
R-422D's composition includes 3.4% R-600a (isobutane) specifically to enable mineral oil miscibility. Without the hydrocarbon component, the HFC majority (R-125 65.1% + R-134a 31.5% = 96.6%) would not mix with R-22's mineral oil, causing oil-return failures.
The R-600a addition bridges the polarity gap. R-600a is a non-polar hydrocarbon (compatible with mineral oil); the HFC components are polar (not compatible with mineral oil); the small R-600a fraction is enough to enable acceptable oil-return behavior in R-22 equipment retrofitted to R-422D.
The A1 safety classification is preserved because the 3.4% R-600a is well below the threshold that would push the blend toward A2L or A3. R-422D behaves as non-flammable in field service despite containing the small hydrocarbon component.
Pressure envelope close to R-22 — retrofit-compatible
R-422D's pressure envelope tracks R-22 within 10-15% across typical AC operating ranges. At 70°F R-422D bubble (132 PSIG) is 9% above R-22 (121 PSIG); dew (118 PSIG) is 2% below R-22. At 95°F outdoor design, R-422D bubble is approximately 215 PSIG vs R-22's 181 PSIG.
The pressure-envelope match is close enough that R-22 equipment can accept R-422D without compressor or expansion-valve modification. Standard 500 PSI service equipment (R-22 era) handles R-422D operating envelope.
GWP 2729 — higher than R-22, faces own phase-down pressure
R-422D's GWP of 2729 is substantially higher than R-22's 1810 [ipccar5]. The high R-125 content (65.1%, GWP 3500) is the primary GWP contributor. R-422D solved R-22's ozone problem but worsened the climate problem.
Under modern climate policy (EPA AIM Act, EU F-Gas Regulation), R-422D faces phase-down pressure for new equipment specification. The blend remains acceptable for service of existing R-22-retrofit installations but is not the right answer for new R-22 retrofit decisions in 2026.
For new R-22 retrofit decisions, the better path is typically full equipment replacement to R-32 or R-454B (sub-700 GWP) rather than refrigerant-only retrofit to higher-GWP HFC blends like R-422D.
R-22 to R-422D retrofit — operationally simpler than R-407C
The R-22 to R-422D retrofit is operationally simpler than R-22 to R-407C because no oil change is required. Standard procedure:
| Step | Action | | --- | --- | | 1. Recover | Recover R-22 to recovery cylinder. | | 2. Drier | Replace filter-drier (best practice for any major service). | | 3. Oil inspection | Inspect mineral oil; replace if degraded, leave in place if good. | | 4. Evacuate | Pull vacuum to 500 microns and hold ≥30 minutes. | | 5. Recharge | Charge R-422D by weight to 90-95% of R-22 nameplate. | | 6. Verify | Verify cooling capacity. Some efficiency loss vs R-22 is normal. |
Capacity match is within 5-10% of R-22 for typical residential AC retrofit. The retrofit can be completed in standard service time without the labor of oil changes that R-407C retrofit requires.
How to think about R-422D in 2026 and beyond
R-422D occupies a narrowing niche in 2026 — service of existing R-22 retrofit installations from the 2005-2020 era. New R-22 retrofit decisions increasingly favor full equipment replacement (R-32 or R-454B) rather than R-422D retrofit, because:
- R-422D's GWP (2729) faces AIM Act phase-down for new equipment
- New R-32 / R-454B equipment is 20-30% more efficient than R-22-era equipment
- R-22 equipment installed pre-2010 is now 15+ years old and at or past typical lifespan
- The retrofit + service-life economics favor replacement over retrofit for older equipment
For existing R-22-to-R-422D retrofits, service supply will continue indefinitely. Pricing trends parallel other high-GWP HFC blends through the AIM Act production schedule.
Frequently asked
›What is R-422D used for?
R-22 retrofit refrigerant for systems where oil change is undesirable. Honeywell markets R-422D as Genetron MO99 specifically targeting residential AC, heat pump, and light commercial cooling applications where the existing R-22 mineral oil can be retained [honeywellgenetron].
The mineral-oil retention is the primary retrofit advantage — R-407C and other HFC R-22 retrofits typically require POE oil change.
›What's R-422D's GWP?
2729 per IPCC AR5 — substantially higher than R-22 (1810) [ipccar5]. The high GWP is the structural disadvantage of R-422D — it eliminates R-22's chlorine ODP problem but creates a worse GWP problem.
R-422D is no longer specified for new equipment under modern climate policy. Service of existing R-422D retrofits continues but new R-22 retrofits in 2026 increasingly favor full equipment replacement to R-32 or R-454B (sub-700 GWP) rather than R-422D (GWP 2729).
›Can I retrofit R-22 to R-422D without oil change?
Yes — that's the primary retrofit advantage. The 3.4% R-600a hydrocarbon component improves miscibility with mineral oil, enabling mineral oil retention through retrofit. Standard procedure: recover R-22, replace filter-drier, evacuate to 500 microns, recharge R-422D by weight to OEM nameplate.
Verify mineral oil condition. If oil is degraded (moisture, acidity), replace as part of retrofit. But the typical R-22 system can transition to R-422D without oil change.
›Why does R-422D contain hydrocarbon (R-600a)?
Mineral oil miscibility. HFC refrigerants (R-125, R-134a) are not miscible with mineral oil — without an additive, R-422D would have oil-return problems in R-22 mineral oil systems. The 3.4% R-600a (isobutane, hydrocarbon) is enough to bridge the polarity gap between the HFC components and mineral oil, enabling acceptable oil return without oil change.
The R-600a fraction is too small (3.4%) to change the blend's A1 safety classification (the non-flammable HFC majority dominates).
›Is R-422D safe to handle?
ASHRAE class A1 — non-toxic and non-flammable [ashrae34]. Standard HFC service procedures apply. The small R-600a hydrocarbon content does not change the safety class.
›Does R-422D have temperature glide?
Yes, approximately 8°F at typical operating pressures (CoolProp 7.2.0). Use dew curve for superheat measurement (suction line) and bubble curve for subcooling (liquid line). Modern PT calculators handle this automatically when R-422D is selected.
›Should I use R-422D or R-407C for R-22 retrofit?
Depends on whether oil change is desired or feasible. R-422D allows mineral oil retention (no oil change needed); R-407C requires POE oil change. R-422D is operationally simpler for retrofit; R-407C has slightly lower GWP (1774 vs 2729) but the oil change is significant service labor.
For older R-22 equipment with substantial remaining life: R-422D for operational simplicity. For newer R-22 equipment where the additional work for POE retrofit is justified by the GWP reduction: R-407C.
In 2026, the better answer is often neither — full replacement with R-32 or R-454B equipment (sub-700 GWP) avoids both retrofit blends.
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-422D acceptable for R-22 retrofit
- [5]CoolProp 7.2.0
- [6]AHRI Standard 700-2019
- [7]Honeywell Genetron MO99 (R-422D) Technical Information