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R-744 pressure-temperature chart and data
Carbon dioxide. Safety class A1, GWP 1. Supermarket refrigeration, heat pumps and water heating. Very high pressure; critical point only 88 °F, so above that it never condenses.
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R-744 data sheet
| Name | Carbon dioxide |
|---|---|
| Type | Natural |
| Safety class | A1 — lower toxicity, does not burn |
| Ozone depletion (ODP) | 0 |
| Global warming (GWP, 100 yr) | 1 |
| Boils at 1 atm | -126.5 °F (-88.1 °C) |
| Critical temperature | 87.8 °F (31.0 °C) |
| Temperature glide | none / very small |
| Low side at 5 °F evaporating | 318 psig (2190 kPa) |
| High side at 86 °F condensing | above the critical point, no condensing |
| Old cylinder colour | none assigned |
| Oil | POE / PAG / PAO |
| Used for | Supermarket refrigeration, heat pumps and water heating. Very high pressure; critical point only 88 °F, so above that it never condenses. |
Pressures are saturation values from reference equations of state. Real pressures change with load and airflow. GWP is the IPCC AR4 100-year value (blends calculated from their ingredients). Cylinder colours were an old AHRI code; since 2020 new cylinders are all one colour with the name on the label, so always read the label, never go by colour.
R-744 pressure / temperature chart
| °F | °C | psig | kPa |
|---|---|---|---|
| -60 | -51.1 | 79.9 | 551 |
| -59 | -50.6 | 82.0 | 566 |
| -58 | -50.0 | 84.3 | 581 |
| -57 | -49.4 | 86.5 | 597 |
| -56 | -48.9 | 88.8 | 612 |
| -55 | -48.3 | 91.1 | 628 |
| -54 | -47.8 | 93.5 | 645 |
| -53 | -47.2 | 95.9 | 661 |
| -52 | -46.7 | 98.4 | 678 |
| -51 | -46.1 | 101 | 695 |
| -50 | -45.6 | 103 | 713 |
| -49 | -45.0 | 106 | 730 |
| -48 | -44.4 | 109 | 748 |
| -47 | -43.9 | 111 | 767 |
| -46 | -43.3 | 114 | 785 |
| -45 | -42.8 | 117 | 804 |
| -44 | -42.2 | 119 | 823 |
| -43 | -41.7 | 122 | 843 |
| -42 | -41.1 | 125 | 863 |
| -41 | -40.6 | 128 | 883 |
| -40 | -40.0 | 131 | 903 |
| -39 | -39.4 | 134 | 924 |
| -38 | -38.9 | 137 | 945 |
| -37 | -38.3 | 140 | 966 |
| -36 | -37.8 | 143 | 988 |
| -35 | -37.2 | 146 | 1010 |
| -34 | -36.7 | 150 | 1032 |
| -33 | -36.1 | 153 | 1055 |
| -32 | -35.6 | 156 | 1078 |
| -31 | -35.0 | 160 | 1101 |
| -30 | -34.4 | 163 | 1125 |
| -29 | -33.9 | 167 | 1149 |
| -28 | -33.3 | 170 | 1173 |
| -27 | -32.8 | 174 | 1198 |
| -26 | -32.2 | 177 | 1223 |
| -25 | -31.7 | 181 | 1248 |
| -24 | -31.1 | 185 | 1274 |
| -23 | -30.6 | 189 | 1300 |
| -22 | -30.0 | 192 | 1326 |
| -21 | -29.4 | 196 | 1353 |
| -20 | -28.9 | 200 | 1380 |
| -19 | -28.3 | 204 | 1408 |
| -18 | -27.8 | 208 | 1436 |
| -17 | -27.2 | 212 | 1464 |
| -16 | -26.7 | 217 | 1493 |
| -15 | -26.1 | 221 | 1522 |
| -14 | -25.6 | 225 | 1552 |
| -13 | -25.0 | 229 | 1581 |
| -12 | -24.4 | 234 | 1612 |
| -11 | -23.9 | 238 | 1642 |
| -10 | -23.3 | 243 | 1673 |
| -9 | -22.8 | 247 | 1705 |
| -8 | -22.2 | 252 | 1737 |
| -7 | -21.7 | 257 | 1769 |
| -6 | -21.1 | 261 | 1802 |
| -5 | -20.6 | 266 | 1835 |
| -4 | -20.0 | 271 | 1868 |
| -3 | -19.4 | 276 | 1902 |
| -2 | -18.9 | 281 | 1937 |
| -1 | -18.3 | 286 | 1971 |
| 0 | -17.8 | 291 | 2007 |
| 1 | -17.2 | 296 | 2042 |
| 2 | -16.7 | 301 | 2078 |
| 3 | -16.1 | 307 | 2115 |
| 4 | -15.6 | 312 | 2152 |
| 5 | -15.0 | 318 | 2189 |
| 6 | -14.4 | 323 | 2227 |
| 7 | -13.9 | 329 | 2266 |
| 8 | -13.3 | 334 | 2305 |
| 9 | -12.8 | 340 | 2344 |
| 10 | -12.2 | 346 | 2384 |
| 11 | -11.7 | 352 | 2424 |
| 12 | -11.1 | 357 | 2465 |
| 13 | -10.6 | 363 | 2506 |
| 14 | -10.0 | 369 | 2547 |
| 15 | -9.4 | 376 | 2589 |
| 16 | -8.9 | 382 | 2632 |
| 17 | -8.3 | 388 | 2675 |
| 18 | -7.8 | 394 | 2719 |
| 19 | -7.2 | 401 | 2763 |
| 20 | -6.7 | 407 | 2808 |
| 21 | -6.1 | 414 | 2853 |
| 22 | -5.6 | 420 | 2898 |
| 23 | -5.0 | 427 | 2945 |
| 24 | -4.4 | 434 | 2991 |
| 25 | -3.9 | 441 | 3038 |
| 26 | -3.3 | 448 | 3086 |
| 27 | -2.8 | 455 | 3134 |
| 28 | -2.2 | 462 | 3183 |
| 29 | -1.7 | 469 | 3233 |
| 30 | -1.1 | 476 | 3282 |
| 31 | -0.6 | 483 | 3333 |
| 32 | 0.0 | 491 | 3384 |
| 33 | 0.6 | 498 | 3435 |
| 34 | 1.1 | 506 | 3487 |
| 35 | 1.7 | 513 | 3540 |
| 36 | 2.2 | 521 | 3593 |
| 37 | 2.8 | 529 | 3647 |
| 38 | 3.3 | 537 | 3702 |
| 39 | 3.9 | 545 | 3756 |
| 40 | 4.4 | 553 | 3812 |
| 41 | 5.0 | 561 | 3868 |
| 42 | 5.6 | 569 | 3925 |
| 43 | 6.1 | 578 | 3982 |
| 44 | 6.7 | 586 | 4040 |
| 45 | 7.2 | 594 | 4099 |
| 46 | 7.8 | 603 | 4158 |
| 47 | 8.3 | 612 | 4218 |
| 48 | 8.9 | 620 | 4278 |
| 49 | 9.4 | 629 | 4339 |
| 50 | 10.0 | 638 | 4401 |
| 51 | 10.6 | 647 | 4463 |
| 52 | 11.1 | 656 | 4526 |
| 53 | 11.7 | 666 | 4590 |
| 54 | 12.2 | 675 | 4654 |
| 55 | 12.8 | 684 | 4719 |
| 56 | 13.3 | 694 | 4785 |
| 57 | 13.9 | 704 | 4851 |
| 58 | 14.4 | 713 | 4918 |
| 59 | 15.0 | 723 | 4986 |
| 60 | 15.6 | 733 | 5054 |
| 61 | 16.1 | 743 | 5123 |
| 62 | 16.7 | 753 | 5193 |
| 63 | 17.2 | 763 | 5264 |
| 64 | 17.8 | 774 | 5335 |
| 65 | 18.3 | 784 | 5407 |
| 66 | 18.9 | 795 | 5480 |
| 67 | 19.4 | 805 | 5553 |
| 68 | 20.0 | 816 | 5628 |
| 69 | 20.6 | 827 | 5703 |
| 70 | 21.1 | 838 | 5779 |
| 71 | 21.7 | 849 | 5855 |
| 72 | 22.2 | 860 | 5933 |
| 73 | 22.8 | 872 | 6011 |
| 74 | 23.3 | 883 | 6090 |
| 75 | 23.9 | 895 | 6170 |
| 76 | 24.4 | 907 | 6251 |
| 77 | 25.0 | 919 | 6333 |
| 78 | 25.6 | 931 | 6416 |
| 79 | 26.1 | 943 | 6499 |
| 80 | 26.7 | 955 | 6584 |
| 81 | 27.2 | 967 | 6669 |
| 82 | 27.8 | 980 | 6756 |
| 83 | 28.3 | 993 | 6843 |
| 84 | 28.9 | 1005 | 6932 |
- Critical temperature is 87.8 °F, so the chart stops just below it. Above that the gas cannot condense.
V = vacuum in inches of mercury. Saturation pressure in psig at sea level, calculated from reference equations of state. The chart gives the boiling temperature at that pressure, not the pipe temperature. Air in the system adds pressure and throws it off.
R-744 pressure in psig, psia, kPa and bar
| °F | °C | psig | psia | kPa gauge | kPa absolute | bar absolute |
|---|---|---|---|---|---|---|
| -60 | -51.1 | 79.9 | 94.6 | 551 | 652 | 6.52 |
| -55 | -48.3 | 91.1 | 105.8 | 628 | 730 | 7.30 |
| -50 | -45.6 | 103 | 118.1 | 713 | 814 | 8.14 |
| -45 | -42.8 | 117 | 131.3 | 804 | 906 | 9.06 |
| -40 | -40.0 | 131 | 145.7 | 903 | 1004 | 10.04 |
| -35 | -37.2 | 146 | 161.2 | 1010 | 1111 | 11.11 |
| -30 | -34.4 | 163 | 177.8 | 1125 | 1226 | 12.26 |
| -25 | -31.7 | 181 | 195.7 | 1248 | 1349 | 13.49 |
| -20 | -28.9 | 200 | 214.9 | 1380 | 1482 | 14.82 |
| -15 | -26.1 | 221 | 235.5 | 1522 | 1623 | 16.23 |
| -10 | -23.3 | 243 | 257.4 | 1673 | 1775 | 17.75 |
| -5 | -20.6 | 266 | 280.8 | 1835 | 1936 | 19.36 |
| 0 | -17.8 | 291 | 305.7 | 2007 | 2108 | 21.08 |
| 5 | -15.0 | 318 | 332.2 | 2189 | 2291 | 22.91 |
| 10 | -12.2 | 346 | 360.4 | 2384 | 2485 | 24.85 |
| 15 | -9.4 | 376 | 390.3 | 2589 | 2691 | 26.91 |
| 20 | -6.7 | 407 | 421.9 | 2808 | 2909 | 29.09 |
| 25 | -3.9 | 441 | 455.4 | 3038 | 3140 | 31.40 |
| 30 | -1.1 | 476 | 490.8 | 3282 | 3384 | 33.84 |
| 35 | 1.7 | 513 | 528.1 | 3540 | 3641 | 36.41 |
| 40 | 4.4 | 553 | 567.6 | 3812 | 3913 | 39.13 |
| 45 | 7.2 | 594 | 609.2 | 4099 | 4200 | 42.00 |
| 50 | 10.0 | 638 | 653.0 | 4401 | 4502 | 45.02 |
| 55 | 12.8 | 684 | 699.1 | 4719 | 4820 | 48.20 |
| 60 | 15.6 | 733 | 747.8 | 5054 | 5156 | 51.56 |
| 65 | 18.3 | 784 | 798.9 | 5407 | 5508 | 55.08 |
| 70 | 21.1 | 838 | 852.8 | 5779 | 5880 | 58.80 |
| 75 | 23.9 | 895 | 909.6 | 6170 | 6272 | 62.72 |
| 80 | 26.7 | 955 | 969.6 | 6584 | 6685 | 66.85 |
V = vacuum in inches of mercury. Absolute pressure = gauge + 14.7 psi at sea level; use absolute pressure for gas-law work. For blends the dew column is the vapour (suction) side and the bubble column the liquid side.
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Calculation aids and reference figures for licensed technicians. Always follow the manufacturer’s data plate and manual for the exact model, and local codes. Gas, electrical and refrigerant work must be done by a qualified, licensed person. Pressures are typical saturation values and change with load and airflow.