R-404A is a near-azeotropic HFC blend used mainly in commercial refrigeration, walk-in coolers and freezers, and transport refrigeration, sold under trade names including Genetron 404A and Freon 404A. It’s ASHRAE-classified A1, non-toxic and non-flammable, though it’s subject to the EPA’s ongoing HFC phase-down under the AIM Act, which is pushing new equipment toward lower-GWP alternatives. The chart below shows saturation pressure at every temperature, the number a technician cross-references against a gauge reading to check charge and diagnose a system.
To use it: measure the actual line temperature with a clamp thermometer, find that temperature in the chart, and compare the corresponding pressure to what your gauges read. A significant mismatch between the two points to a charge or airflow problem worth investigating further.
404a Operating Pressure Chart (404a pt chart)
| Temp(°F) | Liquid Pressure (psi) | Vapor Pressure (psi) | Temp (°C) |
| -49 | 0.9 | 0.3 | -45 |
| -48 | 1.3 | 0.7 | -44.4 |
| -47 | 1.7 | 1.2 | -43.9 |
| -46 | 2.1 | 1.6 | -43.3 |
| -45 | 2.6 | 2 | -42.8 |
| -44 | 3 | 2.4 | -42.2 |
| -43 | 3.5 | 2.9 | -41.7 |
| -42 | 4 | 3.4 | -41.1 |
| -41 | 4.4 | 3.8 | -40.6 |
| -40 | 4.9 | 4.3 | -40 |
| -39 | 5.4 | 4.8 | -39.4 |
| -38 | 5.9 | 5.3 | -38.9 |
| -37 | 6.4 | 5.8 | -38.3 |
| -36 | 7 | 6.3 | -37.8 |
| -35 | 7.5 | 6.8 | -37.2 |
| -34 | 8 | 7.4 | -36.7 |
| -33 | 8.6 | 7.9 | -36.1 |
| -32 | 9.2 | 8.5 | -35.6 |
| -31 | 9.7 | 9 | -35 |
| -30 | 10.3 | 9.6 | -34.4 |
| -29 | 10.9 | 10.2 | -33.9 |
| -28 | 11.5 | 10.8 | -33.3 |
| -27 | 12.2 | 11.4 | -32.8 |
| -26 | 12.8 | 12 | -32.2 |
| -25 | 13.4 | 12.7 | -31.7 |
| -24 | 14.1 | 13.3 | -31.1 |
| -23 | 14.8 | 14 | -30.6 |
| -22 | 15.4 | 14.6 | -30 |
| -21 | 16.1 | 15.3 | -29.4 |
| -20 | 16.8 | 16 | -28.9 |
| -19 | 17.5 | 16.7 | -28.3 |
| -18 | 18.3 | 17.4 | -27.8 |
| -17 | 19 | 18.2 | -27.2 |
| -16 | 19.8 | 18.9 | -26.7 |
| -15 | 20.5 | 19.7 | -26.1 |
| -14 | 21.3 | 20.4 | -25.6 |
| -13 | 22.1 | 21.2 | -25 |
| -12 | 22.9 | 22 | -24.4 |
| -11 | 23.7 | 22.8 | -23.9 |
| 10 | 24.6 | 24.6 | -23.3 |
| -9 | 25.4 | 24.5 | -22.8 |
| -8 | 26.3 | 25.3 | -22.2 |
| -7 | 27.1 | 26.2 | -21.7 |
| -6 | 28 | 27 | -21.1 |
| -5 | 28.9 | 27.9 | -20.6 |
| -4 | 29.8 | 28.8 | -20 |
| -3 | 30.8 | 29.8 | – 19.4 |
| -2 | 31.7 | 30.7 | – 18.9 |
| -1 | 32.7 | 31.6 | -18.3 |
| 0 | 33.7 | 32.6 | -17.8 |
| 1 | 34.7 | 33.6 | -17.2 |
| 2 | 35.7 | 34.6 | – 16.7 |
| 3 | 36.7 | 35.6 | – 25.6 |
| 4 | 37.7 | 36.6 | -15.6 |
| 5 | 38.8 | 37.7 | -15 |
| 6 | 39.8 | 38.7 | -14.4 |
| 7 | 40.9 | 39.8 | -13.9 |
| 8 | 42 | 40.9 | -13.3 |
| 9 | 43.1 | 42 | -12.8 |
| 10 | 44.3 | 43.1 | -12.2 |
| 11 | 45.4 | 44.3 | -11.7 |
| 12 | 46.6 | 45.4 | -11.1 |
| 13 | 47.8 | 46.6 | -10.6 |
| 14 | 49 | 47.8 | -10 |
| 15 | 50.2 | 49 | -9.4 |
| 16 | 51.5 | 50.2 | -8.9 |
| 17 | 52.7 | 51.5 | -8.3 |
| 18 | 54 | 52.7 | -7.8 |
| 19 | 55.3 | 54 | -7.2 |
| 20 | 56.6 | 55.3 | -6.7 |
| 21 | 57.9 | 56.6 | -6.1 |
| 22 | 59.3 | 58 | -5.6 |
| 23 | 60.6 | 59.3 | -5 |
| 24 | 62 | 60.7 | -4.4 |
| 25 | 63.4 | 62.1 | -3.9 |
| 26 | 64.8 | 63.5 | -3.3 |
| 27 | 66.3 | 64.9 | -2.8 |
| 28 | 67.8 | 66.4 | -2.2 |
| 29 | 69.2 | 67.8 | -1.7 |
| 30 | 70.7 | 69.3 | -1,1 |
| 31 | 72.3 | 70.8 | -0.6 |
| 32 | 73.8 | 72.4 | 0 |
| 33 | 75.4 | 73.9 | 0.6 |
| 34 | 77 | 75.5 | 1.1 |
| 35 | 78.6 | 77.1 | 1.7 |
| 36 | 80.2 | 78.7 | 2.2 |
| 37 | 81,8 | 80.3 | 2.8 |
| 38 | 83.5 | 82 | 3.3 |
| 39 | 85.2 | 83.7 | 3.9 |
| 40 | 86.9 | 85.4 | 4.4 |
| 41 | 88.6 | 87.1 | 5 |
| 42 | 90.4 | 88.8 | 5.6 |
| 43 | 92.2 | 90.6 | 6.1 |
| 44 | 94 | 92.4 | 6.7 |
| 45 | 95.8 | 94.2 | 7.2 |
| 46 | 97.6 | 96 | 7.8 |
| 47 | 99.5 | 97.9 | 8,3 |
| 48 | 101.4 | 99.8 | 8.9 |
| 49 | 103.3 | 101.7 | 9.4 |
| 50 | 105.3 | 103.6 | 10 |
| 51 | 107.2 | 105.6 | 10.6 |
| 52 | 109.2 | 107.6 | 11.1 |
| 53 | 11.2 | 109.6 | 11.7 |
| 54 | 113.3 | 111.6 | 12.2 |
| 55 | 115.3 | 113.6 | 12.8 |
| 56 | 117.4 | 115.7 | 13.3 |
| 57 | 119.5 | 117.8 | 13.9 |
| 58 | 121.7 | 119.9 | 14.4 |
| 59 | 123.8 | 122.1 | 15 |
| 60 | 126 | 124.2 | 15.6 |
| 61 | 128.2 | 126.4 | 16.1 |
| 62 | 130.5 | 128.7 | 16.7 |
| 63 | 132.7 | 130.9 | 17.2 |
| 64 | 135 | 133.2 | 17.8 |
| 65 | 137.3 | 135.5 | 18.3 |
| 66 | 139.7 | 137.8 | 18,9 |
| 67 | 142 | 140.2 | 19.4 |
| 68 | 144.4 | 142.6 | 20 |
| 69 | 146.9 | 145 | 20.6 |
| 70 | 149.3 | 147.4 | 21.1 |
| 71 | 151.8 | 149.9 | 21.7 |
| 72 | 154.3 | 152.4 | 22.2 |
| 73 | 156.8 | 154.9 | 22.8 |
| 74 | 159.4 | 157.5 | 23.3 |
| 75 | 162 | 160.1 | 23.9 |
| 76 | 164.6 | 162.7 | 24.4 |
| 77 | 167.3 | 165.3 | 25 |
| 78 | 170 | 168 | 25.6 |
| 79 | 172.7 | 170.7 | 26.1 |
| 80 | 175.4 | 173.4 | 26.7 |
| 81 | 178.2 | 176.2 | 27.2 |
| 82 | 181 | 179 | 27.8 |
| 83 | 183.8 | 181.8 | 28.3 |
| 84 | 186.7 | 184.7 | 28.9 |
| 85 | 189.5 | 187.5 | 29.4 |
| 86 | 192.5 | 190.4 | 30 |
| 87 | 195.4 | 193.4 | 30.6 |
| 88 | 198.4 | 196.4 | 31.1 |
| 89 | 201.4 | 199.4 | 31.7 |
| 90 | 204.5 | 202.4 | 32.2 |
| 91 | 207.6 | 205.5 | 32.8 |
| 92 | 210.7 | 208.6 | 33.3 |
| 93 | 213.8 | 211.7 | 33.9 |
| 94 | 217 | 214.9 | 34.4 |
| 95 | 220.2 | 218.1 | 35 |
| 96 | 223.4 | 221.4 | 35.6 |
| 97 | 226.7 | 224.6 | 36.1 |
| 98 | 230 | 227.9 | 36.7 |
| 99 | 233.4 | 231 | 37.2 |
| 100 | 236.8 | 234.6 | 37.8 |
| 101 | 240.2 | 238.1 | 38.3 |
| 102 | 243.6 | 241.5 | 38.9 |
| 103 | 247.1 | 245 | 39.4 |
| 104 | 250.6 | 248.5 | 40 |
| 105 | 254.2 | 252.1 | 40.5 |
| 106 | 257.8 | 255.6 | 41.1 |
| 107 | 261.4 | 259 .3 | 41.7 |
| 108 | 265.1 | 262.9 | 42.2 |
| 109 | 268.8 | 266.6 | 42.8 |
| 110 | 272.5 | 270.4 | 43.3 |
| 111 | 276.3 | 274.1 | 43.9 |
| 112 | 280.1 | 278 | 44.4 |
| 113 | 284 | 281.8 | 45 |
| 114 | 287.9 | 285.7 | 45.6 |
| 115 | 291.8 | 289.6 | 46.1 |
| 116 | 295.8 | 293.6 | 46.7 |
| 117 | 299.8 | 297.6 | 47.2 |
| 118 | 303.8 | 301.7 | 47.8 |
| 119 | 307.9 | 305.8 | 48.3 |
| 120 | 312.1 | 309.9 | 48.9 |
| 121 | 119.1 | 3141 | 494 |
| 122 | 320.4 | 318.3 | 50 |
| 123 | 324.7 | 322.5 | 50.6 |
| 124 | 329 | 326.8 | 51.1 |
| 125 | 333.3 | 331.2 | 51.7 |
| 126 | 337.7 | 335.6 | 52.2 |
| 127 | 342.1 | 340 | 52.8 |
| 128 | 346.6 | 344.4 | 53.3 |
| 129 | 351.1 | 349 | 53.9 |
| 130 | 355.7 | 353.5 | 54.4 |
| 131 | 360.2 | 35.1 | 55 |
| 132 | 364.9 | 362.8 | 55.6 |
| 133 | 369.6 | 367.5 | 56.1 |
| 134 | 374.3 | 372.2 | 56.7 |
| 135 | 379.1 | 377 | 57.2 |
| 136 | 383.9 | 381.9 | 57.8 |
| 137 | 388.8 | 386.8 | 58.3 |
| 138 | 393.7 | 391.7 | 58.9 |
| 139 | 398.7 | 396.7 | 59.4 |
| 140 | 403.7 | 401.7 | 60 |
| 141 | 408.8 | 406.8 | 60.6 |
| 142 | 413.9 | 412 | 61.1 |
| 143 | 419.1 | 417.1 | 61.7 |
| 144 | 424.3 | 422.4 | 62.2 |
| 145 | 429.6 | 427.7 | 62.8 |
| 146 | 434.9 | 433.1 | 63.3 |
| 147 | 440.3 | 438.5 | 63.9 |
| 148 | 445.8 | 443.9 | 64.4 |
| 149 | 451.3 | 449.5 | 65 |
| 150 | 456.8 | 455.1 | 65.6 |
Read also: R410a Pressure Chart High and Low Side
psi: Pound per square inch, unit of pressure
FAQ
What is the normal suction pressure on a 404a walk in the freezer?
The normal suction pressure on a 404 a walk in freezer is around 10-20 psig (10 is ideal) on the suction side if working properly.
And the high side is about 180 or so. High suction pressure could cause the evaporator coils to freeze.
Is R-404A being phased out?
Yes. R-404A has a high global warming potential (GWP around 3,900-4,000 depending on the reference), which puts it squarely in the EPA’s AIM Act phase-down targets. New equipment increasingly ships with lower-GWP alternatives like R-448A or R-449A, though existing R-404A systems can continue to be serviced with R-404A for now.
Why do the liquid and vapor pressure columns differ at the same temperature?
R-404A is a blend, not a pure refrigerant, so it has a small temperature glide: the liquid (bubble point) and vapor (dew point) phases don’t change state at exactly the same pressure for a given temperature. The two columns in the chart reflect that glide, which is why both are listed rather than a single pressure value.
