R-600a (Isobutane) PT Chart
A3 GWP 3Isobutane (C₄H₁₀). Natural / HC.
Boiling Point
10.9°F
-11.7°C
Critical Temp
274.4°F
134.7°C
Critical Pressure
526.3 psia
36.29 bar
About R-600a (Isobutane)
R-600a (isobutane) is the standard refrigerant in household refrigerators in Europe and much of the world, and is now common in US refrigerators as well. It runs at low pressure, and on the low side it can be below atmospheric pressure at freezer temperatures, which is normal for this refrigerant. Charges are small (usually under 150 g) because it is A3 flammable.
Saturation pressures at typical operating points, taken from the table below:
- Evaporator (40°F): 11.9 PSIG
- Condensing (100°F): 57.9 PSIG
The table covers -30°F to 265°F in 5°F steps. Below about 11°F the saturation pressure is below atmospheric, so gauges read in vacuum (shown in blue in the table).
R-600a (Isobutane) Pressure-Temperature Graph
R-600a (Isobutane) Saturation Pressure Table
Blue values indicate vacuum (below atmospheric pressure).
| °F | °C | PSIG | PSIA | kPa | bar |
|---|---|---|---|---|---|
| -30 | -34.4 | -9.2 | 5.48 | 37.8 | 0.378 |
| -25 | -31.7 | -8.4 | 6.26 | 43.1 | 0.431 |
| -20 | -28.9 | -7.6 | 7.12 | 49.1 | 0.491 |
| -15 | -26.1 | -6.6 | 8.07 | 55.6 | 0.556 |
| -10 | -23.3 | -5.6 | 9.12 | 62.8 | 0.628 |
| -5 | -20.6 | -4.4 | 10.27 | 70.8 | 0.708 |
| 0 | -17.8 | -3.2 | 11.53 | 79.5 | 0.795 |
| 5 | -15.0 | -1.8 | 12.92 | 89.1 | 0.891 |
| 10 | -12.2 | -0.3 | 14.43 | 99.5 | 0.995 |
| 15 | -9.4 | 1.4 | 16.07 | 110.8 | 1.108 |
| 20 | -6.7 | 3.2 | 17.85 | 123.1 | 1.231 |
| 25 | -3.9 | 5.1 | 19.79 | 136.4 | 1.364 |
| 30 | -1.1 | 7.2 | 21.88 | 150.9 | 1.509 |
| 35 | 1.7 | 9.4 | 24.14 | 166.4 | 1.664 |
| 40 | 4.4 | 11.9 | 26.57 | 183.2 | 1.832 |
| 45 | 7.2 | 14.5 | 29.19 | 201.3 | 2.013 |
| 50 | 10.0 | 17.3 | 32.0 | 220.6 | 2.206 |
| 55 | 12.8 | 20.3 | 35.01 | 241.4 | 2.414 |
| 60 | 15.6 | 23.5 | 38.22 | 263.5 | 2.635 |
| 65 | 18.3 | 27.0 | 41.66 | 287.2 | 2.872 |
| 70 | 21.1 | 30.6 | 45.33 | 312.5 | 3.125 |
| 75 | 23.9 | 34.5 | 49.23 | 339.4 | 3.394 |
| 80 | 26.7 | 38.7 | 53.38 | 368.0 | 3.68 |
| 85 | 29.4 | 43.1 | 57.79 | 398.4 | 3.984 |
| 90 | 32.2 | 47.8 | 62.46 | 430.6 | 4.306 |
| 95 | 35.0 | 52.7 | 67.41 | 464.8 | 4.648 |
| 100 | 37.8 | 57.9 | 72.64 | 500.9 | 5.009 |
| 105 | 40.6 | 63.5 | 78.18 | 539.0 | 5.39 |
| 110 | 43.3 | 69.3 | 84.01 | 579.3 | 5.793 |
| 115 | 46.1 | 75.5 | 90.17 | 621.7 | 6.217 |
| 120 | 48.9 | 82.0 | 96.65 | 666.4 | 6.664 |
| 125 | 51.7 | 88.8 | 103.47 | 713.4 | 7.134 |
| 130 | 54.4 | 95.9 | 110.64 | 762.8 | 7.628 |
| 135 | 57.2 | 103.5 | 118.16 | 814.7 | 8.147 |
| 140 | 60.0 | 111.4 | 126.06 | 869.2 | 8.692 |
| 145 | 62.8 | 119.6 | 134.34 | 926.2 | 9.262 |
| 150 | 65.6 | 128.3 | 143.01 | 986.0 | 9.86 |
| 155 | 68.3 | 137.4 | 152.09 | 1048.6 | 10.486 |
| 160 | 71.1 | 146.9 | 161.58 | 1114.1 | 11.141 |
| 165 | 73.9 | 156.8 | 171.5 | 1182.5 | 11.825 |
| 170 | 76.7 | 167.2 | 181.87 | 1253.9 | 12.539 |
| 175 | 79.4 | 178.0 | 192.68 | 1328.5 | 13.285 |
| 180 | 82.2 | 189.3 | 203.96 | 1406.3 | 14.063 |
| 185 | 85.0 | 201.0 | 215.72 | 1487.4 | 14.874 |
| 190 | 87.8 | 213.3 | 227.98 | 1571.9 | 15.719 |
| 195 | 90.6 | 226.0 | 240.74 | 1659.8 | 16.598 |
| 200 | 93.3 | 239.3 | 254.02 | 1751.4 | 17.514 |
| 205 | 96.1 | 253.1 | 267.84 | 1846.7 | 18.467 |
| 210 | 98.9 | 267.5 | 282.21 | 1945.8 | 19.458 |
| 215 | 101.7 | 282.5 | 297.15 | 2048.8 | 20.488 |
| 220 | 104.4 | 298.0 | 312.68 | 2155.9 | 21.559 |
| 225 | 107.2 | 314.1 | 328.81 | 2267.1 | 22.671 |
| 230 | 110.0 | 330.9 | 345.57 | 2382.6 | 23.826 |
| 235 | 112.8 | 348.3 | 362.97 | 2502.6 | 25.026 |
| 240 | 115.6 | 366.3 | 381.04 | 2627.2 | 26.272 |
| 245 | 118.3 | 385.1 | 399.81 | 2756.6 | 27.566 |
| 250 | 121.1 | 404.6 | 419.31 | 2891.0 | 28.91 |
| 255 | 123.9 | 424.9 | 439.56 | 3030.6 | 30.306 |
| 260 | 126.7 | 445.9 | 460.61 | 3175.8 | 31.758 |
| 265 | 129.4 | 467.8 | 482.52 | 3326.9 | 33.269 |
Properties
| ASHRAE Designation | 600a |
| Safety Classification | A3 |
| GWP (AR4, 100-yr) | 3 |
| ODP | 0 |
| Molecular Weight | 58.12 g/mol |
| Boiling Point (1 atm) | 10.9°F / -11.7°C |
| Critical Temperature | 274.4°F / 134.7°C |
| Critical Pressure | 526.3 psia / 36.29 bar |
| Category | Natural / HC |
Common Applications
- Domestic refrigerators
- Small commercial units