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R-134a Pressure Temperature Chart
Interactive PT chart for R-134a. Used in automotive AC, centrifugal chillers, and medium-temperature refrigeration. R-134a operates at lower pressures than R-410A and goes into vacuum below approximately -15°F.
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R-134a Saturation Data
41 data points| Temperature | Pressure (psig) |
|---|---|
| -40°F | -12 vac |
| -35°F | -10.3 vac |
| -30°F | -8.4 vac |
| -25°F | -6.2 vac |
| -20°F | -3.8 vac |
| -15°F | -1.1 vac |
| -10°F | 1.9 |
| -5°F | 5.1 |
| 0°F | 8.6 |
| 5°F | 12.4 |
| 10°F | 16.6 |
| 15°F | 21.1 |
| 20°F | 26.1 |
| 25°F | 31.5 |
| 30°F | 37.3 |
| 35°F | 43.6 |
| 40°F | 50.5 |
| 45°F | 57.9 |
| 50°F | 65.9 |
| 55°F | 74.5 |
| 60°F | 83.7 |
| 65°F | 93.7 |
| 70°F | 104.3 |
| 75°F | 115.7 |
| 80°F | 127.9 |
| 85°F | 140.9 |
| 90°F | 154.8 |
| 95°F | 169.6 |
| 100°F | 185.4 |
| 105°F | 202.1 |
| 110°F | 219.9 |
| 115°F | 238.8 |
| 120°F | 258.9 |
| 125°F | 280.2 |
| 130°F | 302.7 |
| 135°F | 326.6 |
| 140°F | 352 |
| 145°F | 378.8 |
| 150°F | 407.2 |
| 155°F | 437.4 |
| 160°F | 469.3 |
Source: ASHRAE Fundamentals. Pressures are gauge (psig) at sea level. Negative values indicate vacuum conditions.
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R-134a Pressure Reference Values
R-134a (tetrafluoroethane, HFC-134a) replaced R-12 in automotive air conditioning starting in the early 1990s and became the global standard for vehicle AC through the 2010s. It is still found in hundreds of millions of operating vehicles and HVAC systems worldwide.
| Temperature | R-134a (psig) |
|---|---|
| -20°F / -29°C | 3 vac |
| 0°F / -18°C | 14 |
| 20°F / -7°C | 31 |
| 40°F / 4°C | 51 |
| 70°F / 21°C | 84 |
| 100°F / 38°C | 138 |
| 110°F / 43°C | 163 |
| 130°F / 54°C | 221 |
Approximate values. Negative values indicate vacuum. Use the interactive tool above for precise readings. Source: ASHRAE Fundamentals.
Key Facts About R-134a
R-134a has a Global Warming Potential (GWP) of 1,430 and zero Ozone Depletion Potential (ODP). It is being phased down under HFC reduction schedules in the EU and United States.
At 40°F, R-134a saturates at approximately 51 psig — lower than R-22 (67 psig) and much lower than R-410A (115 psig) at the same temperature.
R-134a enters vacuum conditions below approximately -15°F (-26°C). At -20°F, it sits at roughly -3 in. Hg vacuum. This requires careful leak testing at low temperatures to avoid moisture ingress.
R-134a uses PAG (polyalkylene glycol) oil in automotive applications and POE (polyolester) oil in stationary HVAC and refrigeration equipment. These oils are not interchangeable between the two applications.
R-1234yf is replacing R-134a in new automotive AC systems globally. Most new U.S. vehicle models have used R-1234yf since the 2017–2019 model years.
R-134a PT Chart — Frequently Asked Questions
What is the normal operating pressure for R-134a?
R-134a saturation pressures: at 0°F (-18°C), R-134a saturates at approximately 14 psig. At 40°F, approximately 51 psig. At 70°F, approximately 84 psig. At 100°F (condenser), approximately 138 psig. R-134a operates at significantly lower pressures than R-410A or R-404A, making it common in automotive AC systems and centrifugal chillers where moderate pressures are preferred.
Does R-134a go into vacuum at low temperatures?
Yes. R-134a enters vacuum (below atmospheric pressure) at temperatures below approximately -15°F (-26°C). In the PT chart, these appear as negative psig values. Vacuum conditions during service mean any system leak will draw in air and moisture rather than push out refrigerant. This makes proper evacuation and leak checking critical when working on low-temperature R-134a applications.
What replaces R-134a in automotive air conditioning?
R-1234yf (HFO-1234yf) is the primary replacement for R-134a in automotive air conditioning systems. It has a GWP of only 4 compared to R-134a at 1,430. Most new vehicles in the United States and EU have used R-1234yf since around 2014–2017. The two refrigerants have similar pressure-temperature characteristics, though they are not interchangeable. R-1234yf is mildly flammable (A2L classification).
What is R-134a used for other than automotive AC?
Beyond automotive air conditioning, R-134a is widely used in centrifugal chillers for large commercial buildings, medium-temperature refrigeration equipment, household refrigerators in some markets, transport refrigeration, and industrial cooling applications. Its moderate operating pressures and compatibility with common materials made it a versatile replacement for R-12 when CFCs were phased out.
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