R-32 PT Chart: How to Actually Read the Pressures

At 40 °F saturation, R-32 reads about 121 psig; at 100 °F saturation, about 326 psig. R-32 is a single compound, not a blend, so it has no temperature glide and its PT chart needs only one column. Use suction pressure for superheat and liquid-line pressure for subcooling, both read from that same column.

R-32 is showing up on more service calls as the A2L transition moves through residential equipment, and most technicians meet it expecting it to behave like R-454B, because both are A2Ls replacing R-410A. On the gauges it behaves much more like R-410A. That is the useful part of this article: the pressures you already know are close, but close is not identical, and a manifold still set to the wrong refrigerant will throw your superheat off without making it obvious.

What are the actual R-32 pressures?

These values come from the Chemours Pressure-Temperature Guide for A/C, document OPTXLPTAC-2, which prints R-32 on the same sheet as R-410A and R-454B. The comparison columns are the point: they show how much of your R-410A instinct carries over.

Temperature	R-32	R-410A	R-454B
−20 °F	26.8 psig	26.2 psig	22.6 psig
−10 °F	37.1 psig	36.3 psig	31.8 psig
0 °F	49.3 psig	48.2 psig	42.7 psig
10 °F	63.5 psig	62.2 psig	55.4 psig
20 °F	80.0 psig	78.4 psig	70.3 psig
30 °F	99.1 psig	97.0 psig	87.4 psig
40 °F	121.0 psig	118.4 psig	107.0 psig
50 °F	145.8 psig	142.6 psig	129.3 psig
60 °F	174.0 psig	170.7 psig	161.1 psig
70 °F	205.8 psig	201.8 psig	190.5 psig
80 °F	241.5 psig	236.5 psig	223.4 psig
90 °F	281.3 psig	275.4 psig	260.0 psig
100 °F	325.7 psig	318.5 psig	300.8 psig
110 °F	374.9 psig	366.4 psig	345.9 psig
120 °F	429.3 psig	419.4 psig	395.7 psig

Two things stand out. R-32 reads only about 2 percent above R-410A at the same saturation temperature, a few psig at a typical coil temperature. And it reads well above R-454B: about 14 psig higher at 40 °F and about 25 psig higher at 100 °F.

On the Chemours sheet, the R-454B figures switch from saturated vapor to saturated liquid at 52 °F, because R-454B is a blend with glide. The R-32 column needs no such switch. Always work from the current chart for the refrigerant actually in the system, and set your digital manifold or app to R-32 before you connect it.

Why does an R-32 chart only need one column?

Because R-32 is a pure substance: difluoromethane. A single compound boils and condenses at one temperature for a given pressure, so the bubble point and dew point are the same number. There is no glide to correct for.

That is different from the other refrigerants you will meet alongside it. R-410A is a near-azeotropic blend whose glide is small enough to ignore, so it also gets one column, but for a different reason. R-454B is roughly 69 percent R-32 by weight with R-1234yf making up the rest, and that second component is what gives it glide. An R-454B chart prints two values per temperature and expects you to choose the right one.

The practical upside of R-32 being a single compound: if it leaks, the composition cannot shift. What is left in the system is still R-32, which is why a small charge adjustment after a leak repair is chemically sound on R-32 and not on a zeotropic blend.

What are normal R-32 operating pressures?

No chart can give you one number, and a source that does is making an assumption for you.

Suction pressure follows the evaporator coil temperature, and coil temperature moves with indoor load, airflow and humidity. Head pressure follows condensing temperature, which moves with outdoor ambient and condenser airflow. A correctly charged R-32 system will read very differently at 7 a.m. and at 4 p.m. on the same day.

What the chart does give you: a suction reading of about 121 psig corresponds to a 40 °F coil, and a liquid-line reading of about 326 psig corresponds to 100 °F condensing. Whether those are right for the unit in front of you depends on the manufacturer's charging data, not on the chart.

Which reading do you use for superheat and subcooling?

With no glide, the lookup column is the same for both. The pressure and temperature you take are not.

Calculation	Pressure you read	Temperature you measure	Formula
Superheat	Suction line	Suction line, near the service port	Line temp − saturation temp
Subcooling	Liquid line	Liquid line, at the condenser outlet	Saturation temp − line temp

Which one you charge by depends on the metering device. Fixed-orifice systems are charged by superheat; TXV and EEV systems are charged by subcooling. The target value comes from the installation instructions or the data plate. Superheat and subcooling, and what each reading actually tells you walks through the combinations.

What does R-32 standing pressure tell you?

With the system off and equalized, liquid and vapor share one pressure. As long as some liquid remains, that pressure is the saturation pressure at the temperature of the refrigerant, which after a long rest is close to the surrounding air temperature. On an 80 °F day, expect about 241 psig; at 70 °F, about 206 psig.

That tells you refrigerant is present, and that is about all. Standing pressure cannot tell you whether the charge is correct, because a system with 60 percent of its charge still holds saturated liquid at exactly the same pressure. A standing reading well below saturation for the ambient does mean something: little or no liquid is left, and you are most likely looking at a large leak.

Do the pressures change what Section 608 requires?

No. PT readings, pressure testing and charging targets are service practice. None of them appear in 40 CFR Part 82. What Part 82 does govern on an R-32 system is the same as on any other high-pressure appliance, so this is Type II work:

Requirement	Where it comes from
Do not knowingly vent the refrigerant	Section 608, 40 CFR 82.154(a)
R-32 sold only to certified technicians and the other listed buyers	Section 608, 40 CFR 82.154(c)
Recover to the required level before opening the appliance	Section 608, 40 CFR 82.156
Recovery equipment certified for flammable refrigerants	Section 608, 40 CFR 82.158, Appendix B4
Target superheat, subcooling and nitrogen test pressure	Manufacturer, the unit's installation instructions
Pulling to 500 microns before charging	Best practice, not a Section 608 evacuation level

Two details from that table catch people out. For a high-pressure appliance with under 200 pounds of charge, Table 1 of 82.156 requires recovery to 0 inches of mercury before opening it. The deep dehydration vacuum afterwards is good practice, not the recovery rule. And where Table 1 splits on November 15, 1993, that date refers to the manufacture date of the recovery equipment, never the age of the appliance.

A related question, how do you pressure test an R-32 system, has the same answer. Use dry nitrogen, to the test pressure in the manufacturer's installation instructions, and never use refrigerant as a test gas. The test pressure is the manufacturer's call, not a federal figure.

What this means on the job

Treat R-32 as a single-column refrigerant that runs a few psig above R-410A, and do not let that closeness make you careless.

Read the nameplate first. Set the manifold to R-32 rather than R-410A, because reading an R-32 system against the R-410A column shifts your saturation temperature by roughly a degree. That is small enough to pass unnoticed and large enough to matter when you charge to a tight subcooling target. Reading it against an R-454B chart is worse: at 40 °F the gap is 14 psig, which reads as a coil several degrees warmer than it is and can make a correct charge look overcharged.

Bring recovery equipment and a cylinder rated for flammable refrigerants, and keep ignition sources away from the work. None of that changes your certification, which is set by appliance class rather than refrigerant and does not expire. If Type II is the section you are still working toward, the practice questions on recovery, evacuation and high-pressure appliances cover what these systems lean on hardest.

Frequently asked questions

What should R-32 pressure be at 40 degrees?

About 121 psig. That is the saturation pressure of R-32 at 40 °F on the Chemours pressure-temperature guide. It is the reading you would expect on the suction side if the evaporator coil is at 40 °F, but whether 40 °F is the right coil temperature depends on load, airflow and the manufacturer's charging data.

What should subcooling be for R-32?

Whatever the equipment manufacturer specifies on the data plate or in the installation instructions. There is no universal R-32 subcooling value. Calculate it by converting liquid-line pressure to saturation temperature on the R-32 chart, then subtracting the measured liquid-line temperature, and compare the result against that manufacturer target.

What is the normal standing pressure for R-32?

Roughly the saturation pressure at the ambient temperature, as long as liquid remains in the system: about 206 psig at 70 °F and about 241 psig at 80 °F. A standing pressure confirms refrigerant is present but cannot confirm the charge is correct. A reading well below saturation suggests the liquid is gone.

Is R-32 higher pressure than R-410A?

Slightly. R-32 runs about 2 percent above R-410A at the same saturation temperature, which is 121.0 against 118.4 psig at 40 °F and 325.7 against 318.5 psig at 100 °F. The equipment is still designed and listed for one refrigerant, so R-32 is never a substitute in an R-410A system.

Does R-32 have temperature glide?

No. R-32 is a single compound, difluoromethane, so it boils and condenses at one temperature for each pressure. That is why its PT chart prints one saturation column, and why a small leak cannot change its composition. R-454B, which is mostly R-32 blended with R-1234yf, does have glide.

Do I need a special certification to work on R-32?

Not from EPA. Section 608 sections follow appliance class, so a residential R-32 system is Type II work. There is no EPA A2L certification. Manufacturers, employers and local codes may require separate flammable-refrigerant training, and Section 608 requires recovery equipment certified for flammable refrigerants.

Sources

• Chemours, Pressure-Temperature Guide for A/C (OPTXLPTAC-2)
• 40 CFR 82.154, Prohibitions
• 40 CFR 82.156, Required practices
• 40 CFR 82.158, Standards for recovery and/or recycling equipment
• EPA, Technology Transitions GWP Reference Table
• EPA, Section 608 Technician Certification Requirements