R-134a PT Chart
A1 GWP 1430Pure refrigerant (1,1,1,2-Tetrafluoroethane). HFC.
Phase-down in automotive (replaced by R-1234yf)
About R-134a
R-134a replaced R-12 in automotive AC in the 1990s and is also used in domestic refrigerators, medium-temperature commercial refrigeration and centrifugal/screw chillers. New US light-duty vehicles now use R-1234yf, and chillers are moving to R-513A and R-1234ze(E), but R-134a remains widely serviced.
Saturation pressures at typical operating points, taken from the table below:
- Evaporator (35°F): 30.4 PSIG
- Condensing (130°F): 198.7 PSIG
The table covers -55°F to 205°F in 5°F steps. Below about -15°F the saturation pressure is below atmospheric, so gauges read in vacuum (shown in blue in the table).
R-134a Pressure-Temperature Graph
R-134a Saturation Pressure Table
Blue values indicate vacuum (below atmospheric pressure).
| °F | °C | PSIG | PSIA | kPa | bar |
|---|---|---|---|---|---|
| -55 | -48.3 | -10.0 | 4.7 | 32.4 | 0.324 |
| -50 | -45.6 | -9.2 | 5.5 | 37.9 | 0.379 |
| -45 | -42.8 | -8.3 | 6.41 | 44.2 | 0.442 |
| -40 | -40.0 | -7.3 | 7.43 | 51.2 | 0.512 |
| -35 | -37.2 | -6.1 | 8.58 | 59.1 | 0.591 |
| -30 | -34.4 | -4.8 | 9.86 | 68.0 | 0.68 |
| -25 | -31.7 | -3.4 | 11.3 | 77.9 | 0.779 |
| -20 | -28.9 | -1.8 | 12.9 | 88.9 | 0.889 |
| -15 | -26.1 | -0.0 | 14.67 | 101.2 | 1.012 |
| -10 | -23.3 | 1.9 | 16.63 | 114.7 | 1.147 |
| -5 | -20.6 | 4.1 | 18.79 | 129.6 | 1.296 |
| 0 | -17.8 | 6.5 | 21.17 | 146.0 | 1.46 |
| 5 | -15.0 | 9.1 | 23.78 | 163.9 | 1.639 |
| 10 | -12.2 | 11.9 | 26.63 | 183.6 | 1.836 |
| 15 | -9.4 | 15.0 | 29.74 | 205.0 | 2.05 |
| 20 | -6.7 | 18.4 | 33.12 | 228.4 | 2.284 |
| 25 | -3.9 | 22.1 | 36.8 | 253.7 | 2.537 |
| 30 | -1.1 | 26.1 | 40.78 | 281.2 | 2.812 |
| 35 | 1.7 | 30.4 | 45.09 | 310.9 | 3.109 |
| 40 | 4.4 | 35.0 | 49.74 | 343.0 | 3.43 |
| 45 | 7.2 | 40.1 | 54.75 | 377.5 | 3.775 |
| 50 | 10.0 | 45.4 | 60.13 | 414.6 | 4.146 |
| 55 | 12.8 | 51.2 | 65.91 | 454.5 | 4.545 |
| 60 | 15.6 | 57.4 | 72.11 | 497.1 | 4.971 |
| 65 | 18.3 | 64.0 | 78.73 | 542.8 | 5.428 |
| 70 | 21.1 | 71.1 | 85.8 | 591.6 | 5.916 |
| 75 | 23.9 | 78.7 | 93.35 | 643.6 | 6.436 |
| 80 | 26.7 | 86.7 | 101.39 | 699.0 | 6.99 |
| 85 | 29.4 | 95.2 | 109.93 | 758.0 | 7.58 |
| 90 | 32.2 | 104.3 | 119.01 | 820.6 | 8.206 |
| 95 | 35.0 | 113.9 | 128.65 | 887.0 | 8.87 |
| 100 | 37.8 | 124.2 | 138.85 | 957.3 | 9.573 |
| 105 | 40.6 | 135.0 | 149.65 | 1031.8 | 10.318 |
| 110 | 43.3 | 146.4 | 161.07 | 1110.6 | 11.106 |
| 115 | 46.1 | 158.4 | 173.14 | 1193.7 | 11.937 |
| 120 | 48.9 | 171.2 | 185.86 | 1281.5 | 12.815 |
| 125 | 51.7 | 184.6 | 199.28 | 1374.0 | 13.74 |
| 130 | 54.4 | 198.7 | 213.41 | 1471.4 | 14.714 |
| 135 | 57.2 | 213.6 | 228.28 | 1574.0 | 15.74 |
| 140 | 60.0 | 229.2 | 243.92 | 1681.8 | 16.818 |
| 145 | 62.8 | 245.7 | 260.36 | 1795.1 | 17.951 |
| 150 | 65.6 | 262.9 | 277.61 | 1914.1 | 19.141 |
| 155 | 68.3 | 281.0 | 295.73 | 2039.0 | 20.39 |
| 160 | 71.1 | 300.0 | 314.73 | 2170.0 | 21.7 |
| 165 | 73.9 | 320.0 | 334.65 | 2307.3 | 23.073 |
| 170 | 76.7 | 340.8 | 355.53 | 2451.3 | 24.513 |
| 175 | 79.4 | 362.7 | 377.41 | 2602.2 | 26.022 |
| 180 | 82.2 | 385.6 | 400.34 | 2760.2 | 27.602 |
| 185 | 85.0 | 409.7 | 424.36 | 2925.8 | 29.258 |
| 190 | 87.8 | 434.8 | 449.52 | 3099.4 | 30.994 |
| 195 | 90.6 | 461.2 | 475.91 | 3281.3 | 32.813 |
| 200 | 93.3 | 488.9 | 503.59 | 3472.1 | 34.721 |
| 205 | 96.1 | 518.0 | 532.68 | 3672.7 | 36.727 |
Properties
| ASHRAE Designation | 134a |
| Safety Classification | A1 (non-flammable, low toxicity) |
| GWP (AR4, 100-yr) | 1430 |
| ODP | 0 |
| Molecular Weight | 102.03 g/mol |
| Boiling Point (1 atm) | -14.9°F / -26.1°C |
| Critical Temperature | 213.9°F / 101.1°C |
| Critical Pressure | 588.7 psia / 40.59 bar |
| Category | HFC |
Common Applications
- Automotive AC
- Medium-temp refrigeration
- Chillers
- Aerosol propellant
Frequently Asked Questions
What pressure should R-134a be at 70°F?
At 70°F, R-134a has a saturation pressure of 71.1 PSIG (85.8 PSIA). For automotive AC, normal low-side pressure typically runs 25–45 PSIG and high-side 200–250 PSIG during operation.
What refrigerant replaced R-134a in new cars?
R-1234yf (HFO-1234yf) replaced R-134a in new US vehicles. R-1234yf has a nearly identical pressure at 70°F (73.9 vs 71.1 PSIG) but a GWP of only 4 vs 1430. The refrigerants are not interchangeable without system modifications.
Is R-134a used in home refrigerators?
Yes, R-134a is used in domestic refrigerators and freezers, and commercial display cases. New appliances are shifting to R-600a (isobutane) and R-290 (propane) due to lower GWP, especially in Europe.