R22 PT Chart

Enter a temperature to get R-22's saturation pressure, or a gauge reading to get its saturation temperature — °F or °C, psig, psia, kPa or bar — from NIST data, −40°F to 150°F.

Home & PropertyWorldwideSource: NIST Chemistry WebBook (SRD 69), R22 saturation propertiesFree, no sign-up

Full R-22 PT chart, −40°F to 150°F (every 5°F)

°F	°C	psig
-40	-40.0	0.6
-35	-37.2	2.6
-30	-34.4	4.9
-25	-31.7	7.4
-20	-28.9	10.2
-15	-26.1	13.2
-10	-23.3	16.5
-5	-20.6	20.1
0	-17.8	24.0
5	-15.0	28.3
10	-12.2	32.8
15	-9.4	37.8
20	-6.7	43.1
25	-3.9	48.8
30	-1.1	55.0
35	1.7	61.5
40	4.4	68.6
45	7.2	76.1
50	10.0	84.1
55	12.8	92.6

°F	°C	psig
60	15.6	101.6
65	18.3	111.2
70	21.1	121.4
75	23.9	132.2
80	26.7	143.6
85	29.4	155.7
90	32.2	168.4
95	35.0	181.8
100	37.8	195.9
105	40.6	210.8
110	43.3	226.4
115	46.1	242.8
120	48.9	260.0
125	51.7	278.0
130	54.4	296.9
135	57.2	316.7
140	60.0	337.4
145	62.8	359.0
150	65.6	381.7

How to read the R-22 PT chart

Choose what you know. A temperature, to find the matching saturation pressure — or a gauge reading, to find the temperature R-22 boils or condenses at that pressure.
Enter the value and its unit. Temperatures in °F or °C; pressures in psig, psia, or kPa or bar gauge.
Read the saturation point. The result shows the temperature and the pressure in every unit, interpolated from NIST's 1°F table.
Use it for superheat or subcooling. The saturation temperature from a suction or liquid-line pressure is the figure a measured line temperature is compared against.
Open the full chart if you want the table. The complete chart from −40°F to 150°F in 5°F steps sits under the tool, with °C and psig.

10 situations where the R-22 PT figure is needed

Converting a suction gauge reading to a saturation temperature

A technician reading 68.6 psig on the suction side of an R-22 system gets 40°F as the saturation temperature — the starting point for superheat.

Working out subcooling from the liquid line

The saturation temperature at the head pressure, minus the measured liquid-line temperature, is subcooling. The tool supplies the first number.

Checking a gauge set's built-in scale

Analog gauges print PT scales for several refrigerants. A precise figure for R-22 at the reading is useful when the printed scale is hard to read.

Servicing older R-22 equipment

Older systems may still contain R-22. Having its PT data on a phone, without an app, saves digging out a paper chart.

Working in metric units

Technicians outside the US read bar or kPa. The tool converts both ways and shows °C.

Confirming a standing pressure in a system that is off

With the system off and at ambient temperature, the PT chart shows the pressure R-22 would have at that temperature — a figure to compare a gauge against.

Teaching refrigeration students

The chart and lookup show the relationship between pressure and boiling point directly, with the source data cited.

Checking a low-side pressure in a cold room

Low saturation temperatures down to −40°F are covered, which matters for refrigeration rather than comfort cooling.

Double-checking a value from a manufacturer's chart

The data here were compared with a refrigerant supplier's published R-22 chart and agree within 0.05 psi at the points checked.

Printing a chart for the truck

Open the full chart and print the page for a paper copy from −40°F to 150°F.

Where the R-22 data comes from

The pressures come from the NIST Chemistry WebBook, NIST Standard Reference Database 69, 'Thermophysical Properties of Fluid Systems', for R22 (chlorodifluoromethane, CAS 75-45-6). The saturation table was retrieved in 1°F steps from −40°F to 150°F with pressure in psia, and is built into this page — nothing is fetched while you use it.

Gauge pressure is absolute pressure minus a standard atmosphere of 14.696 psia. Values between whole degrees, and the reverse lookup from pressure to temperature, use linear interpolation between adjacent 1°F rows. As a cross-check, the values were compared with the iGas USA R22 pressure-temperature chart at eleven temperatures from −40°F to 130°F; all agree within 0.05 psi, for example 68.6 psig at 40°F, 195.9 psig at 100°F and 260.0 psig at 120°F.

R-22 is a single-component refrigerant, so its bubble and dew points are the same and there is one saturation pressure for each temperature. That is not true of blends such as R-410A or R-404A, which this chart does not cover.

The limits: gauge figures assume sea level; at altitude the atmosphere is lower, so a gauge reads higher for the same absolute pressure. The chart covers −40°F to 150°F. A saturation pressure describes the refrigerant, not the correct operating pressure of a system — that depends on load, airflow and the equipment manufacturer's charging procedure.

This page provides property data. It is not a charging procedure. R-22 handling and recovery are regulated work for certified technicians.

Sources

NIST Chemistry WebBook — Thermophysical Properties of R22 — Saturation properties used to build the chart (SRD 69)
iGas USA — R22 Pressure-Temperature Chart (PDF) — Supplier chart used as the cross-check
U.S. EPA — Section 608 Technician Certification — The certification required for working with refrigerants such as R-22

Frequently asked questions

What is the R-22 pressure at 40°F?

68.6 psig (83.3 psia), from NIST's saturation data. That is the pressure at which R-22 boils at 40°F.

What temperature is 260 psig on R-22?

120°F. Enter 260 psig in pressure mode to see it in °C and other units.

Why do different charts show slightly different numbers?

Charts are rounded and built from slightly different property models. The NIST values here agree with a supplier's published chart within 0.05 psi at the points checked.

Does altitude change the reading?

Gauge pressure does. This page assumes sea-level atmosphere (14.696 psia). Higher up, the atmosphere is lower, so a gauge reads more for the same absolute pressure; the psia figure does not change.

Can I use this chart for R-410A?

No. R-410A is a different refrigerant — a blend — with its own pressure-temperature relationship. Use a chart for that refrigerant.

Does this tell me if the system is charged correctly?

No. It gives the refrigerant's saturation properties. Charging depends on the equipment manufacturer's procedure, including superheat or subcooling targets and operating conditions.