R-22 PT Chart: How to Actually Read the Pressures

At 40 °F saturation, R-22 reads about 69 psig; at 100 °F saturation, about 196 psig. R-22 is a single-component refrigerant with no temperature glide, so one saturation value per temperature is exact. Use suction pressure for superheat and liquid-line pressure for subcooling. First, confirm that the system still contains R-22.

That last point is why this chart deserves more than a scanned PDF. R-22 has not been produced or imported since January 1, 2020, so a lot of the old R-22 equipment still running has been topped up or converted to something else along the way. The chart is only as good as your knowledge of what is actually in the system. An R-22 chart read against R-407C gives you a confident, wrong answer.

What are the actual R-22 pressures?

These come from the Chemours Pressure-Temperature Guide for A/C, document OPTXLPTAC-2, which prints Freon 22 on the same sheet as R-410A and the common R-22 service blends. R-410A is shown here for comparison.

Temperature	R-22	R-410A
−20 °F	10.2 psig	26.2 psig
−10 °F	16.5 psig	36.3 psig
0 °F	24.0 psig	48.2 psig
10 °F	32.8 psig	62.2 psig
20 °F	43.1 psig	78.4 psig
30 °F	55.0 psig	97.0 psig
35 °F	61.6 psig (approx.)	107.3 psig (approx.)
40 °F	68.6 psig	118.4 psig
45 °F	76.1 psig (approx.)	130.2 psig (approx.)
50 °F	84.1 psig	142.6 psig
60 °F	101.6 psig	170.7 psig
70 °F	121.4 psig	201.8 psig
80 °F	143.6 psig	236.5 psig
90 °F	168.4 psig	275.4 psig
100 °F	195.9 psig	318.5 psig
110 °F	226.4 psig	366.4 psig
120 °F	260.0 psig	419.4 psig

The 35 °F and 45 °F rows fall between the sheet's printed 2-degree steps and are averaged from the rows on either side. Every other value is printed on the sheet.

R-22 boils at roughly −41 °F at atmospheric pressure, and the Chemours sheet shows it at just 0.6 psig at −40 °F. Any R-22 system running below that goes into a vacuum on the low side, which is one reason low-temperature R-22 refrigeration was always a different animal from comfort cooling.

Why does an R-22 chart only need one column?

Because R-22 is a single compound, chlorodifluoromethane (HCFC-22), not a blend.

A pure substance boils and condenses at one fixed temperature for any given pressure. There is nothing to separate, no component that boils off first and no glide. The single column on an R-22 chart is therefore exactly right, not a close-enough simplification.

That is different from R-410A. R-410A also prints one column, but only because it is a near-azeotropic blend whose glide is small enough to ignore. It is different again from true zeotropic blends such as R-407C, where the bubble point and dew point sit several degrees apart and the chart has to tell you which one it is printing. The R-410A PT chart walks through that difference.

What if the R-22 system has been retrofitted?

This is the trap. Most of the drop-in-style R-22 replacements are blends, and their pressures are not R-22's. The same Chemours sheet prints three common ones side by side:

Temperature	R-22	R-407C	R-422B (NU-22B)	R-438A (MO99)
20 °F	43.1	37.9	35.5	36.2
40 °F	68.6	63.2	59.4	60.5
50 °F	84.1	78.8	74.1	75.5
90 °F	168.4	194.1	170.4	181.2
100 °F	195.9	225.5	198.2	210.6
110 °F	226.4	260.3	229.0	243.1

All values psig. Per the sheet's key, the blends' values at 50 °F and below are saturated vapor (dew point, for superheat). Above that, they are saturated liquid (bubble point, for subcooling).

Read an R-407C system against the R-22 column and the suction side looks about 5 psi low. That is a few degrees of false superheat, which is enough to make a correct charge look short. On the high side it goes the other way. Someone who "tops it off with 22" to fix a number that was never wrong ends up with a mixed, contaminated charge that no chart describes.

So before you trust any reading on an older unit, look for a retrofit label and ask the owner what has been added. The R-22 replacement refrigerant guide covers what each substitute changes.

Which reading do you use for superheat and subcooling?

With pure R-22, the chart value is the same either way, but the pressure you take is not:

Calculation	Pressure you read	Temperature you measure
Superheat	Suction line, at the service port	Suction line, near the same point
Subcooling	Liquid line	Liquid line, at the condenser outlet

Superheat is the measured suction-line temperature minus the saturation temperature you looked up. Subcooling is the saturation temperature you looked up minus the measured liquid-line temperature. The metering device decides which one you charge by: a fixed orifice charges by superheat, and a TXV charges by subcooling. What each reading actually tells you covers the combinations.

What should R-22 pressure be on a 90-degree day?

There is no single right number, and an answer that gives you one is guessing.

Suction pressure follows evaporator coil temperature, which moves with indoor load, airflow and humidity. Head pressure follows condensing temperature, which sits above outdoor ambient by an amount set by the condenser's design and cleanliness. A correctly charged unit reads differently on a humid 90-degree afternoon than on a dry one. The chart converts pressure to temperature, and the manufacturer's charging chart or installation instructions tell you what the resulting superheat or subcooling should be.

What does R-22 standing pressure tell you?

When a system has been off long enough to equalize, both sides read the saturation pressure at the temperature of the refrigerant. With an 80 °F unit, that is about 144 psig.

That is useful for two things. It confirms there is still liquid refrigerant in the system, and a reading well off the chart value for the ambient temperature suggests either a different refrigerant or non-condensables. It says nothing about how much refrigerant is in there. A system can be half empty and still show a perfectly normal standing pressure, as long as some liquid remains.

Do the pressures change what Section 608 requires?

No. PT readings, superheat and charging procedure are service practice. None of them appears in 40 CFR Part 82. What does apply to an R-22 system is the same framework as any other refrigerant. A residential R-22 split system is a high-pressure appliance, which makes it Type II work.

Requirement	Source
Do not knowingly vent or release refrigerant	Section 608 — 40 CFR 82.154(a)
Only certified technicians may buy it	Section 608 — 40 CFR 82.154(c)
Recover to the Table 1 level before opening the system	Section 608 — 40 CFR 82.156
Leak repair once the full charge is 50 lb or more	Section 608 — 40 CFR 82.157
Target superheat and subcooling	Manufacturer — the unit's charging instructions
Evacuating to 500 microns before recharging	Best practice, not a Section 608 evacuation level

For a high-pressure appliance with a full charge under 200 pounds, Table 1 of 82.156 requires 0 inches of mercury before you open it. Where the table splits on November 15, 1993, that date refers to when the recovery equipment was made, not the age of the R-22 system. Recovered R-22 can go back into equipment belonging to the same owner. Selling it on requires reclamation first. Is R-22 still available? covers the supply side.

What this means on the job

On an R-22 call, the first question is not what the gauges say. It is whether this is still R-22. Check for a retrofit label, ask about past service, and set your manifold to the refrigerant that is actually there.

After that the process is the same as on any system. Take both pressures and both line temperatures, convert, calculate superheat and subcooling, and compare against the manufacturer's target. If the charge is short, the system has a leak. Given what reclaimed R-22 costs, finding it before adding more is a question of economics as well as of the law. If you are working toward Type II, the practice test questions on recovery and refrigerant handling are where R-22 service rules come up most.

Frequently asked questions

How do you read an R-22 PT chart?

Read the pressure on your gauge, find that value in the R-22 column, and read across to the temperature. That is the refrigerant's saturation temperature at that pressure. Subtract it from the measured suction-line temperature for superheat, or subtract the measured liquid-line temperature from it for subcooling, then compare with the manufacturer's target.

What are normal pressures for R-22?

There is no fixed normal value. A 40 °F evaporator corresponds to about 69 psig, which is typical under moderate load. A 100 °F condensing temperature corresponds to about 196 psig. Both move with indoor load, airflow and outdoor temperature, so judge the charge by superheat or subcooling against the manufacturer's target, not by the raw pressure.

Does R-22 have temperature glide?

No. R-22 is a single compound, HCFC-22, so it boils and condenses at one temperature for each pressure. Its PT chart needs only one column, and that column is exact. R-22 replacement blends such as R-407C do have glide, which is why their charts separate dew-point and bubble-point values.

Can I use an R-22 chart on a system converted to R-407C or R-422B?

No. Those blends run at different pressures than R-22 at the same temperature, and they have glide. On the Chemours sheet, R-407C reads 63.2 psig at 40 °F against R-22's 68.6 psig. Reading a retrofitted system against the R-22 column makes a correct charge look wrong.

What is R-22 standing pressure at 80 degrees?

About 144 psig, per the Chemours chart, once the system has been off long enough to equalize at 80 °F. Standing pressure confirms that liquid refrigerant is present and roughly what it is. It cannot tell you whether the system is fully charged, because any amount of remaining liquid produces the same saturation pressure.

Can you still buy R-22 to charge a system?

Yes, if you hold a Section 608 certification. No new R-22 has been produced or imported since January 1, 2020, but reclaimed R-22 and remaining pre-2020 stock are legal to sell to certified technicians and to use in existing equipment. Section 608 certification does not expire, so an older card still qualifies.

Sources

• Chemours, Pressure-Temperature Guide for A/C (OPTXLPTAC-2)
• EPA, Technicians and Contractors: Frequent Questions on the ODS Phaseout
• EPA, Refrigerant Sales Restriction
• 40 CFR 82.154, Prohibitions
• 40 CFR 82.156, Required practices
• 40 CFR 82.157, Appliance maintenance and leak repair