R-422B is an HFC retrofit blend for existing R-22 equipment, whose production and import ended in 2020; its AR4 GWP of about 2,526 is far above the 700 limit that EPA's Technology Transitions rule sets for new residential and light-commercial AC, EPA names it among refrigerants barred from several new refrigeration products, and as an HFC blend its supply falls under the AIM Act phasedown.
R-422B pressure-temperature table
Every 5°F shown. Liquid = bubble point (use for subcooling); vapor = dew point (use for superheat). ″ Hg = inches of mercury vacuum.
R-422B saturation pressure, psig at sea level
°F
°C
Liquid psig
Vapor psig
-40
-40.0
1.0
5.5″ Hg
-39
-39.4
1.4
4.8″ Hg
-38
-38.9
1.9
4.1″ Hg
-37
-38.3
2.3
3.4″ Hg
-36
-37.8
2.7
2.6″ Hg
-35
-37.2
3.1
1.9″ Hg
-34
-36.7
3.6
1.1″ Hg
-33
-36.1
4.0
0.3″ Hg
-32
-35.6
4.5
0.2
-31
-35.0
5.0
0.6
-30
-34.4
5.5
1.1
-29
-33.9
6.0
1.5
-28
-33.3
6.5
1.9
-27
-32.8
7.0
2.3
-26
-32.2
7.5
2.8
-25
-31.7
8.0
3.2
-24
-31.1
8.6
3.7
-23
-30.6
9.1
4.2
-22
-30.0
9.7
4.7
-21
-29.4
10.3
5.2
-20
-28.9
10.9
5.7
-19
-28.3
11.4
6.2
-18
-27.8
12.1
6.7
-17
-27.2
12.7
7.3
-16
-26.7
13.3
7.8
-15
-26.1
13.9
8.3
-14
-25.6
14.6
8.9
-13
-25.0
15.2
9.5
-12
-24.4
15.9
10.1
-11
-23.9
16.6
10.7
-10
-23.3
17.3
11.3
-9
-22.8
18.0
11.9
-8
-22.2
18.7
12.5
-7
-21.7
19.4
13.2
-6
-21.1
20.2
13.8
-5
-20.6
20.9
14.5
-4
-20.0
21.7
15.2
-3
-19.4
22.5
15.9
-2
-18.9
23.3
16.6
-1
-18.3
24.1
17.3
0
-17.8
24.9
18.0
1
-17.2
25.7
18.8
2
-16.7
26.6
19.5
3
-16.1
27.4
20.3
4
-15.6
28.3
21.1
5
-15.0
29.2
21.9
6
-14.4
30.1
22.7
7
-13.9
31.0
23.5
8
-13.3
31.9
24.4
9
-12.8
32.9
25.2
10
-12.2
33.8
26.1
11
-11.7
34.8
26.9
12
-11.1
35.8
27.8
13
-10.6
36.8
28.8
14
-10.0
37.8
29.7
15
-9.4
38.8
30.6
16
-8.9
39.9
31.6
17
-8.3
40.9
32.5
18
-7.8
42.0
33.5
19
-7.2
43.1
34.5
20
-6.7
44.2
35.5
21
-6.1
45.4
36.6
22
-5.6
46.5
37.6
23
-5.0
47.6
38.7
24
-4.4
48.8
39.8
25
-3.9
50.0
40.9
26
-3.3
51.2
42.0
27
-2.8
52.5
43.1
28
-2.2
53.7
44.2
29
-1.7
55.0
45.4
30
-1.1
56.2
46.6
31
-0.6
57.5
47.8
32
0.0
58.8
49.0
33
0.6
60.2
50.2
34
1.1
61.5
51.5
35
1.7
62.9
52.8
36
2.2
64.3
54.0
37
2.8
65.7
55.3
38
3.3
67.1
56.7
39
3.9
68.5
58.0
40
4.4
70.0
59.4
41
5.0
71.5
60.8
42
5.6
73.0
62.2
43
6.1
74.5
63.6
44
6.7
76.0
65.0
45
7.2
77.6
66.5
46
7.8
79.2
68.0
47
8.3
80.8
69.5
48
8.9
82.4
71.0
49
9.4
84.0
72.5
50
10.0
85.7
74.1
51
10.6
87.3
75.7
52
11.1
89.1
77.3
53
11.7
90.8
78.9
54
12.2
92.5
80.6
55
12.8
94.3
82.2
56
13.3
96.1
83.9
57
13.9
97.9
85.6
58
14.4
99.7
87.4
59
15.0
101.6
89.1
60
15.6
103.4
90.9
61
16.1
105.3
92.7
62
16.7
107.3
94.5
63
17.2
109.2
96.4
64
17.8
111.2
98.3
65
18.3
113.2
100.2
66
18.9
115.2
102.1
67
19.4
117.2
104.0
68
20.0
119.3
106.0
69
20.6
121.4
108.0
70
21.1
123.5
110.0
71
21.7
125.6
112.1
72
22.2
127.8
114.1
73
22.8
129.9
116.2
74
23.3
132.2
118.3
75
23.9
134.4
120.5
76
24.4
136.6
122.7
77
25.0
138.9
124.9
78
25.6
141.2
127.1
79
26.1
143.6
129.3
80
26.7
145.9
131.6
81
27.2
148.3
133.9
82
27.8
150.7
136.3
83
28.3
153.2
138.6
84
28.9
155.6
141.0
85
29.4
158.1
143.4
86
30.0
160.6
145.8
87
30.6
163.2
148.3
88
31.1
165.8
150.8
89
31.7
168.4
153.3
90
32.2
171.0
155.9
91
32.8
173.7
158.5
92
33.3
176.3
161.1
93
33.9
179.1
163.7
94
34.4
181.8
166.4
95
35.0
184.6
169.1
96
35.6
187.4
171.8
97
36.1
190.2
174.6
98
36.7
193.1
177.4
99
37.2
196.0
180.2
100
37.8
198.9
183.1
101
38.3
201.8
186.0
102
38.9
204.8
188.9
103
39.4
207.8
191.8
104
40.0
210.9
194.8
105
40.6
213.9
197.8
106
41.1
217.0
200.9
107
41.7
220.2
204.0
108
42.2
223.3
207.1
109
42.8
226.5
210.2
110
43.3
229.8
213.4
111
43.9
233.0
216.6
112
44.4
236.3
219.9
113
45.0
239.7
223.1
114
45.6
243.0
226.5
115
46.1
246.4
229.8
116
46.7
249.8
233.2
117
47.2
253.3
236.6
118
47.8
256.8
240.1
119
48.3
260.3
243.6
120
48.9
263.9
247.1
121
49.4
267.5
250.7
122
50.0
271.1
254.3
123
50.6
274.8
257.9
124
51.1
278.5
261.6
125
51.7
282.2
265.3
126
52.2
286.0
269.1
127
52.8
289.8
272.9
128
53.3
293.6
276.7
129
53.9
297.5
280.6
130
54.4
301.5
284.5
131
55.0
305.4
288.5
132
55.6
309.4
292.5
133
56.1
313.4
296.5
134
56.7
317.5
300.6
135
57.2
321.6
304.7
136
57.8
325.8
308.9
137
58.3
329.9
313.1
138
58.9
334.2
317.3
139
59.4
338.4
321.6
140
60.0
342.8
325.9
141
60.6
347.1
330.3
142
61.1
351.5
334.7
143
61.7
355.9
339.2
144
62.2
360.4
343.7
145
62.8
364.9
348.3
146
63.3
369.4
352.9
147
63.9
374.0
357.5
148
64.4
378.6
362.2
149
65.0
383.3
367.0
150
65.6
388.0
371.8
151
66.1
392.8
376.6
152
66.7
397.6
381.5
153
67.2
402.4
386.5
154
67.8
407.3
391.5
155
68.3
412.3
396.5
156
68.9
417.3
401.6
157
69.4
422.3
406.8
158
70.0
427.4
412.0
159
70.6
432.5
417.3
160
71.1
437.6
422.6
Saturation pressures computed with CoolProp 8.0.0 (R422B.mix) on October 10, 2026, gauge pressure at sea level. Checked against Chemours published chart at 8 points; largest difference 0.78 psi. How these numbers are made.
What R-422B is and where it is used
R-422B is a blend of R-125, R-134a and a small amount of isobutane (R-600a). Chemours sells it as Freon NU-22B. It is rated A1 and was designed as a retrofit refrigerant for R-22 air conditioning, both residential and commercial. It lets an existing R-22 system keep running after the R-22 is recovered, usually without changing the oil or the metering device.
R-22 production and import ended in 2020. R-422B is one of several service blends for those systems. See R-22 replacements for how it compares with R-427A and others.
How to read the R-422B chart
R-422B is zeotropic. At any temperature the liquid (bubble) pressure is higher than the vapor (dew) pressure. At 40°F the chart shows 70.0 psig bubble and 59.4 psig dew. At a fixed pressure the glide is about 7.6°F at 60 psig, narrowing to 4.8°F at 250 psig.
Superheat: use the dew column. At 60 psig suction the dew point is 40.4°F. The superheat calculator does this for you.
Subcooling: use the bubble column. At 250 psig liquid pressure the bubble point is 116.0°F. Use the subcooling calculator.
Assume a 40°F evaporator saturation temperature and a 110°F condensing temperature, as round example values, not targets. Compared with R-22 at the same temperatures:
Suction (dew at 40°F): R-422B 59.4 psig, R-22 68.6 psig
Head (bubble at 110°F): R-422B 229.8 psig, R-22 226.4 psig
National Refrigerants describes the same pattern: low-side pressure runs a few psi lower than with R-22, while high-side pressure stays very similar. Do not chase old R-22 suction pressures after a retrofit. National's procedure is to compare the new readings with the R-22 baseline you recorded before the retrofit and adjust the charge or system settings as needed.
Retrofit and service notes
Recover all the R-22 first. National says not to top off a system that contains R-22 with R-422B. Record the weight of R-22 recovered.
Oil. R-422B works with mineral oil, alkylbenzene and POE. The isobutane helps carry mineral oil back to the compressor in systems without a receiver. If oil return is poor, National Refrigerants suggests adding a few ounces of POE.
Charge as liquid. Remove liquid from the cylinder and start at about 90 to 95% of the original R-22 charge by weight, then adjust.
Parts. Replace the filter drier, Schrader cores, cap O-rings and any leaking seals. A correctly sized R-22 TXV is usually fine. Orifice systems may not perform exactly the same, though the orifice usually does not need replacing.
Capacity. National says to expect some capacity loss against R-22, larger at high ambient, and slightly longer run times.
Label the system with the refrigerant and oil type.