Refrigerant Pressure Temperature Chart

This refrigerant pressure temperature chart lists saturation pressures for 9 refrigerants from −40°F to 150°F, referenced to standard atmospheric pressure. For blends, use the vapor (dew) column for superheat and the liquid (bubble) column for subcooling.

Jump to: R-410A · R-454B · R-32 · R-22 · R-134a · R-404A · R-407C · R-448A · R-1234yf

psig is gauge pressure; in. Hg vac marks vacuum. These are refrigerant saturation temperatures, not outdoor temperatures or charging targets.

R-410A pressure temperature chart

Near-azeotropic HFC blend. Its liquid and vapor columns are within about 1 psi of each other (glide about 0.2°F).

Source: iGas USA R-410A PT chart.

R-454B pressure temperature chart

A2L blend (68.9% R-32 / 31.1% R-1234yf by weight) with about 2°F of glide, so pick the right column.

Source: Arkema Forane Pressure Temperature Chart, PPC/SDC 05-2025, R-454B liquid/vapor columns (page 1). Composition: Chemours R-454B technical bulletin, page 3.

R-32 pressure temperature chart

Single-component A2L refrigerant. One column.

Source: iGas USA R-32 PT chart.

R-22 pressure temperature chart

Single-component HCFC. One column.

Source: iGas USA R-22 PT chart.

R-134a pressure temperature chart

Single-component HFC. At about −15°F and colder it sits below atmospheric pressure, shown in inches of mercury.

Source: iGas USA R-134a PT chart.

R-404A pressure temperature chart

HFC blend with a small glide.

Source: iGas USA R-404A PT chart.

R-407C pressure temperature chart

HFC blend with a large glide (about 11°F at 63.2 psig). The wrong column causes big errors.

Source: Arkema Forane Pressure Temperature Chart, PPC/SDC 05-2025.

R-448A pressure temperature chart

Blend with a large glide (about 10°F at 63.2 psig). Use the correct column.

Source: Arkema Forane Pressure Temperature Chart, PPC/SDC 05-2025.

R-1234yf pressure temperature chart

Single-component HFO. One column.

Sources: Hudson Technologies, page 1, supplies −40°F through 110°F; National Refrigerants, page 2, supplies 115°F through 150°F. The last eight pressures are published in whole psi; the extra precision shown in the other rows is not available for those eight values.

How to read a PT chart

1. Confirm the refrigerant. Check the equipment nameplate or the cylinder label. A chart is only correct for the refrigerant it lists.
2. Read your gauge in psig. On a compound gauge, a reading below zero is shown on its vacuum scale, in inches of mercury.
3. Find the pressure in the right column and read across. On a blend, that's the vapor column for superheat and the liquid column for subcooling. On a single-component refrigerant there's only one column.
4. Compare that saturation temperature with a line temperature you measured at the same spot. The difference is your superheat (suction line) or subcooling (liquid line).

If your pressure falls between two rows, the saturation temperature falls between those two temperatures. For example, 120 psig on the R-410A vapor column sits between the 40°F and 45°F rows, at about 40.7°F.

The chart shows refrigerant temperature, not outdoor temperature. The 95°F row doesn't tell you what pressure to expect when it's 95°F outside. It tells you the pressure at which the refrigerant itself boils or condenses at 95°F.

It also doesn't give "normal" operating pressures. Real suction and head pressures depend on the equipment, its load, airflow and outdoor conditions. For targets, use the manufacturer's charging chart or service instructions. The PT chart's job is to turn a measured pressure into a saturation temperature you can compare against. National Refrigerants explains the paired pressure/temperature measurements and phase endpoints.

Similar pressures don't make refrigerants interchangeable, either. R-454B and R-32 are A2L (lower-flammability) refrigerants. Chemours' own PT guide states that no A2L refrigerant is to be used as a retrofit refrigerant; they belong in equipment designed for them.

Which column: liquid (bubble) or vapor (dew)?

Use vapor (dew) for superheat and liquid (bubble) for subcooling. That's the rule printed on the Sporlan PT card and in the Chemours A/C PT guide. R-32, R-22, R-134a and R-1234yf have one column because they boil at a single temperature for a given pressure.

Here's why gliding (zeotropic) blends need two. Their ingredients don't boil at exactly the same temperature. At a fixed pressure, the blend starts to boil at the bubble point and finishes at the dew point. The spread between the two is called temperature glide (Honeywell technical bulletin).

• Superheat means vapor warmer than the point where the last liquid boiled off, so it's measured from the dew point.
• Subcooling means liquid cooler than the point where the last vapor condensed, so it's measured from the bubble point.

The mistake can be large. At 63.2 psig, R-407C's dew point is 40°F and its bubble point is about 29°F. Use the wrong one and your superheat is off by about 11°F. At that same pressure, the mistake costs a bit over 2°F on R-454B and about 0.1°F on R-410A. These between-row temperatures are interpolated estimates, not fixed glide values at every pressure.

Superheat and subcooling: two worked examples

These use pressure and line temperature measured at the same point. Pressures are expressed on the chart's standard-atmosphere reference. The answers are calculations, not recommended targets. Whether a number is right for a given unit depends on its manufacturer's charging procedure.

Superheat on R-407C: use the vapor (dew) column

• Given: Suction pressure is 63.2 psig. Suction line temperature at the same spot is 52°F.
• Look up: In the R-407C vapor (dew) column, 63.2 psig is 40°F.
• Calculate: Superheat = line temperature − dew temperature = 52 − 40 = 12°F.
• Check yourself: If you'd grabbed the liquid column (about 29°F), you'd get about 23°F, nearly double the real answer.

Subcooling on R-454B: use the liquid (bubble) column

• Given: Liquid line pressure is 300.8 psig. Liquid line temperature at the same spot is 90°F.
• Look up: In the R-454B liquid (bubble) column, 300.8 psig is 100°F.
• Calculate: Subcooling = bubble temperature − line temperature = 100 − 90 = 10°F.
• Check yourself: The vapor column puts 300.8 psig at about 102.3°F, which would overstate subcooling by 2.3°F. Reversing the subtraction gives −10°F, a sign that you've swapped the order.

To convert a superheat or subcooling difference to Celsius, multiply by 5/9 and don't subtract 32. So 10°F of subcooling is a 5.6°C temperature difference (5.6 K). The examples use the Arkema chart and the Sporlan phase-selection formulas.

When a reading doesn't match the chart

A recovery cylinder reads higher than the chart

Let the cylinder and its contents reach a stable, measured temperature before comparing pressure with the chart. For a known single-component refrigerant with both liquid and vapor present, a pressure well above the saturation value can indicate noncondensables such as air. Confirm the refrigerant identity, temperature, gauge reading and atmospheric-pressure correction first; room temperature alone does not establish the contents' temperature. This is a check for a possible cause, not proof from pressure alone. Appion's recovery manual describes comparing cylinder temperature and pressure for this check (page 13).

The reading is in inches of mercury

That's vacuum, meaning pressure below the atmosphere around you. Some refrigerants go into vacuum at low saturation temperatures. R-134a, for example, is at 14.8 in. Hg vac at −40°F. The tables above show those values in inches of mercury, the same way a compound gauge shows them.

psig vs psia

A gauge's psig reading is relative to its surrounding atmosphere; these tables use a standard-atmosphere reference. psia is absolute pressure, measured from a perfect vacuum. The general conversion is psia = psig + local atmospheric pressure in psia. At standard sea-level pressure, use about 14.7 psia (14.696 more precisely). EPA's Type II topics include pressure–temperature relationships and the 14.7 conversion; that topic statement is not approval to bring this page into an exam.

The vacuum cells preserve the source's inches-of-mercury readings rather than labelling them as positive psig. To convert a vacuum magnitude to signed gauge pressure, use psig = −in. Hg vac × 3386.389 ÷ 6894.757. For example, 0.1 in. Hg vac is about −0.049 psig, not +0.1 psig. The factors come from NIST's unit-conversion tables.

You're working at altitude

Gauges read relative to local air pressure, and air pressure drops as you climb. At altitude, a gauge reads higher than a sea-level chart expects for the same refrigerant temperature. For a standard-day estimate, subtract the offset below from your gauge reading, then look it up. For an actual local-pressure correction, use chart psig = local gauge psig + local atmospheric psia − 14.696; elevation alone does not supply the actual atmospheric pressure.

For example, using the rounded 2.5 psi offset at 5,000 ft, an R-22 reading of 71.1 psig corresponds to about 40°F, not the 41.7°F you'd get from the raw number. These offsets are standard-atmosphere estimates derived from the National Weather Service formula; actual local air pressure varies with weather. Use local station pressure, not a weather report's sea-level-adjusted pressure. If your digital gauge already adjusts for altitude, don't subtract twice.

The pressure fits more than one refrigerant

With a stable measured temperature, both liquid and vapor present, and no contamination, pressure can help rule a refrigerant out, but it can't prove what's in a cylinder. At 70°F, R-410A reads about 201 psig and R-32 reads 205.8 psig. Go by the label, or use a refrigerant identifier when there's doubt.

PT chart practice questions

These 10 original, unofficial practice questions are not actual EPA exam questions. Answer them with the charts above. Pressure-temperature relationships appear across the EPA Section 608 test topics. Unless a question states otherwise, treat its pressures as standard-reference chart pressures.

Question 1

EPA 608 Type II: pressure-temperature relationships

An R-22 system is at a saturation temperature of 40°F. At sea level, what should an accurate gauge read?

• A. 83.3 psig
• B. 68.6 psig
• C. 53.9 psig
• D. 121.4 psig

Question 2

EPA 608 Type II: psig vs psia

A gauge reads 68.6 psig. Using the standard sea-level approximation of 14.7 psia for atmospheric pressure, what is the absolute pressure?

• A. 53.9 psia
• B. 68.6 psia
• C. 14.7 psia
• D. 83.3 psia

Question 3

Superheat, single-component refrigerant

An R-22 system reads 68.6 psig at the suction service valve. The suction line at that same spot measures 52°F. What is the superheat?

• A. 12°F
• B. 16.6°F
• C. 52°F
• D. 92°F

Question 4

Choosing the column on a blend

An R-407C system reads 63.2 psig on the suction side. Which saturation temperature do you use to calculate superheat?

• A. About 29°F (liquid/bubble)
• B. About 34.5°F (average of the two)
• C. 40°F (vapor/dew)
• D. 63°F

Question 5

Subcooling on an A2L blend

An R-454B system reads 300.8 psig at the liquid line. The liquid line at that spot measures 90°F. What is the subcooling?

• A. 12.3°F
• B. 10°F
• C. 2.3°F
• D. 0°F

Question 6

Temperature glide

At 63.2 psig, use a rounded bubble point of 29°F and a dew point of 40°F for R-407C. What is the approximate temperature glide at this pressure?

• A. 0°F
• B. 34.5°F
• C. 69°F
• D. 11°F

Question 7

EPA 608 Type I: detecting noncondensables

R-134a is the only refrigerant in a recovery cylinder, with both liquid and vapor present. The cylinder and its contents have stabilized at a measured 80°F, and a checked gauge reads 115 psig at standard atmospheric pressure. Which explanation best fits these facts?

• A. 115 psig is normal for R-134a at 80°F
• B. The cylinder holds only vapor, no liquid
• C. Noncondensables, such as air, are in the cylinder
• D. A PT chart does not apply above 70°F

Question 8

EPA 608 Type I: identifying refrigerants by pressure and temperature

A cylinder contains one refrigerant, with both liquid and vapor present. It has stabilized at a measured 70°F and reads about 201 psig at standard atmospheric pressure. Which of these refrigerants fits that reading?

• A. R-410A
• B. R-22
• C. R-134a
• D. R-404A

Question 9

EPA 608 Types II and III: recovery

After a system reaches the required recovery vacuum, you isolate it from the recovery equipment and wait a few minutes. With no external heating or pressure input, the pressure climbs to 5 psig. What does this most likely mean?

• A. Recovery is complete
• B. Air is leaking into the system
• C. The recovery machine is overheating
• D. Refrigerant is still in the system, as liquid or dissolved in the oil

Question 10

Gauge pressure and altitude

At 5,000 feet, an R-22 suction gauge reads 71.1 psig. For this calculation, assume local atmospheric pressure is 12.2 psia and use a 2.5 psi correction to the standard sea-level chart. What is the saturation temperature closest to?

• A. 41.7°F
• B. 40°F
• C. 43.4°F
• D. 71°F

Studying for the full exam? Continue with the free EPA 608 study hub, or check EPA's official test topics.

Where these numbers come from

Each chart reproduces published saturation data from the source named under its table, with Celsius calculated from Fahrenheit. The tables cover every 5°F from −40°F to 150°F. Vacuum readings retain their printed unit; pressures are not equipment operating targets.

• R-410A, R-32, R-22, R-134a, R-404A: iGas USA PT charts (R-410A, R-32, R-22, R-134a, R-404A).
• R-454B, R-407C and R-448A: Arkema Forane Pressure Temperature Chart (PPC/SDC 05-2025), which states its data come from NIST's REFPROP database. R-454B is on page 1; R-407C and R-448A are on page 2.
• R-1234yf: Hudson Technologies for −40°F through 110°F; National Refrigerants (06/2019) for 115°F through 150°F. The National Refrigerants values are whole psi; those rows do not carry tenth-psi precision.

How we checked them: The 351 temperature rows and 546 pressure values were compared with the cited supplier PDF tables, including their page images, phase labels and vacuum-unit markings. Celsius conversions, vacuum conversions, the altitude examples and the practice calculations were checked separately. These checks establish agreement with the named published tables, not independent thermodynamic accuracy or a professional review.

Published tables can differ. For example, the Chemours R-454B table prints vapor pressures of 37.1 psig at −5°F and 312.4 psig at 105°F; the selected Arkema table prints 37.0 and 312.5. This page keeps the Arkema values together rather than silently mixing those editions. For precise work on a specific product, use its manufacturer's chart.

Values between rows in the examples are estimates interpolated from the neighboring rows, using the logarithm of absolute pressure against reciprocal absolute temperature. Interpolation does not restore precision absent from the source or establish an error bound. The altitude table uses the National Weather Service pressure-altitude relationship inverted for standard-atmosphere example pressures. It is not a measurement of local weather.

Last verified: September 28, 2026. The published chart values, units, liquid/vapor labels, derived calculations and cited EPA test-topic wording were checked against the linked sources. Research and checking used AI assistance.

By the Castleport Test Prep Editorial Team

Castleport Test Prep is an independent exam prep publisher. We are not affiliated with, endorsed by, or approved by the U.S. Environmental Protection Agency or any Section 608 certifying organization. These charts and practice questions are not official exam materials. Refrigerant, product and organization names are used to identify their subjects, and trademarks belong to their respective owners. This chart is a reference aid. Always follow the equipment manufacturer's instructions and applicable codes.