R-427A is an HFC retrofit blend for existing R-22 systems, whose production and import ended in 2020; at an AR4 GWP of 2,138 it is above every EPA Technology Transitions GWP limit for new AC and refrigeration equipment (the highest is 1,400), and as an HFC blend its supply falls under the AIM Act phasedown.
R-427A 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-427A saturation pressure, psig at sea level
°F
°C
Liquid psig
Vapor psig
-40
-40.0
2.2
5.1″ Hg
-39
-39.4
2.7
4.4″ Hg
-38
-38.9
3.1
3.7″ Hg
-37
-38.3
3.6
3.0″ Hg
-36
-37.8
4.0
2.2″ Hg
-35
-37.2
4.5
1.4″ Hg
-34
-36.7
5.0
0.7″ Hg
-33
-36.1
5.5
0.1
-32
-35.6
6.0
0.5
-31
-35.0
6.5
0.9
-30
-34.4
7.0
1.3
-29
-33.9
7.6
1.7
-28
-33.3
8.1
2.2
-27
-32.8
8.7
2.6
-26
-32.2
9.2
3.1
-25
-31.7
9.8
3.5
-24
-31.1
10.4
4.0
-23
-30.6
11.0
4.5
-22
-30.0
11.6
5.0
-21
-29.4
12.2
5.5
-20
-28.9
12.8
6.0
-19
-28.3
13.5
6.5
-18
-27.8
14.1
7.1
-17
-27.2
14.8
7.6
-16
-26.7
15.5
8.2
-15
-26.1
16.2
8.8
-14
-25.6
16.9
9.3
-13
-25.0
17.6
9.9
-12
-24.4
18.3
10.5
-11
-23.9
19.1
11.1
-10
-23.3
19.8
11.8
-9
-22.8
20.6
12.4
-8
-22.2
21.3
13.0
-7
-21.7
22.1
13.7
-6
-21.1
22.9
14.4
-5
-20.6
23.7
15.1
-4
-20.0
24.6
15.8
-3
-19.4
25.4
16.5
-2
-18.9
26.3
17.2
-1
-18.3
27.1
17.9
0
-17.8
28.0
18.7
1
-17.2
28.9
19.4
2
-16.7
29.8
20.2
3
-16.1
30.8
21.0
4
-15.6
31.7
21.8
5
-15.0
32.7
22.6
6
-14.4
33.6
23.4
7
-13.9
34.6
24.3
8
-13.3
35.6
25.1
9
-12.8
36.6
26.0
10
-12.2
37.7
26.9
11
-11.7
38.7
27.8
12
-11.1
39.8
28.7
13
-10.6
40.9
29.7
14
-10.0
42.0
30.6
15
-9.4
43.1
31.6
16
-8.9
44.2
32.5
17
-8.3
45.4
33.5
18
-7.8
46.5
34.6
19
-7.2
47.7
35.6
20
-6.7
48.9
36.6
21
-6.1
50.1
37.7
22
-5.6
51.4
38.8
23
-5.0
52.6
39.9
24
-4.4
53.9
41.0
25
-3.9
55.2
42.1
26
-3.3
56.5
43.2
27
-2.8
57.8
44.4
28
-2.2
59.2
45.6
29
-1.7
60.5
46.8
30
-1.1
61.9
48.0
31
-0.6
63.3
49.2
32
0.0
64.7
50.5
33
0.6
66.2
51.8
34
1.1
67.6
53.1
35
1.7
69.1
54.4
36
2.2
70.6
55.7
37
2.8
72.1
57.0
38
3.3
73.7
58.4
39
3.9
75.2
59.8
40
4.4
76.8
61.2
41
5.0
78.4
62.6
42
5.6
80.0
64.1
43
6.1
81.7
65.6
44
6.7
83.3
67.0
45
7.2
85.0
68.6
46
7.8
86.7
70.1
47
8.3
88.5
71.7
48
8.9
90.2
73.2
49
9.4
92.0
74.8
50
10.0
93.8
76.4
51
10.6
95.6
78.1
52
11.1
97.5
79.8
53
11.7
99.3
81.4
54
12.2
101.2
83.1
55
12.8
103.1
84.9
56
13.3
105.0
86.6
57
13.9
107.0
88.4
58
14.4
109.0
90.2
59
15.0
111.0
92.0
60
15.6
113.0
93.9
61
16.1
115.1
95.8
62
16.7
117.2
97.7
63
17.2
119.3
99.6
64
17.8
121.4
101.5
65
18.3
123.5
103.5
66
18.9
125.7
105.5
67
19.4
127.9
107.5
68
20.0
130.2
109.6
69
20.6
132.4
111.6
70
21.1
134.7
113.7
71
21.7
137.0
115.9
72
22.2
139.3
118.0
73
22.8
141.7
120.2
74
23.3
144.1
122.4
75
23.9
146.5
124.7
76
24.4
148.9
126.9
77
25.0
151.4
129.2
78
25.6
153.9
131.5
79
26.1
156.4
133.9
80
26.7
159.0
136.2
81
27.2
161.6
138.6
82
27.8
164.2
141.1
83
28.3
166.8
143.5
84
28.9
169.5
146.0
85
29.4
172.2
148.5
86
30.0
174.9
151.1
87
30.6
177.7
153.7
88
31.1
180.4
156.3
89
31.7
183.3
158.9
90
32.2
186.1
161.6
91
32.8
189.0
164.3
92
33.3
191.9
167.0
93
33.9
194.8
169.8
94
34.4
197.8
172.6
95
35.0
200.8
175.4
96
35.6
203.8
178.3
97
36.1
206.8
181.2
98
36.7
209.9
184.1
99
37.2
213.1
187.1
100
37.8
216.2
190.0
101
38.3
219.4
193.1
102
38.9
222.6
196.1
103
39.4
225.9
199.2
104
40.0
229.1
202.3
105
40.6
232.5
205.5
106
41.1
235.8
208.7
107
41.7
239.2
211.9
108
42.2
242.6
215.2
109
42.8
246.1
218.5
110
43.3
249.5
221.9
111
43.9
253.1
225.2
112
44.4
256.6
228.7
113
45.0
260.2
232.1
114
45.6
263.8
235.6
115
46.1
267.5
239.1
116
46.7
271.2
242.7
117
47.2
274.9
246.3
118
47.8
278.7
249.9
119
48.3
282.5
253.6
120
48.9
286.3
257.3
121
49.4
290.2
261.1
122
50.0
294.1
264.9
123
50.6
298.1
268.7
124
51.1
302.0
272.6
125
51.7
306.1
276.5
126
52.2
310.1
280.5
127
52.8
314.2
284.5
128
53.3
318.4
288.5
129
53.9
322.5
292.6
130
54.4
326.8
296.8
131
55.0
331.0
300.9
132
55.6
335.3
305.2
133
56.1
339.6
309.4
134
56.7
344.0
313.7
135
57.2
348.4
318.1
136
57.8
352.9
322.5
137
58.3
357.4
326.9
138
58.9
361.9
331.4
139
59.4
366.5
336.0
140
60.0
371.1
340.6
141
60.6
375.8
345.2
142
61.1
380.4
349.9
143
61.7
385.2
354.6
144
62.2
390.0
359.4
145
62.8
394.8
364.2
146
63.3
399.7
369.1
147
63.9
404.6
374.0
148
64.4
409.6
379.0
149
65.0
414.6
384.1
150
65.6
419.6
389.1
151
66.1
424.7
394.3
152
66.7
429.8
399.5
153
67.2
435.0
404.7
154
67.8
440.2
410.1
155
68.3
445.5
415.4
156
68.9
450.8
420.8
157
69.4
456.2
426.3
158
70.0
461.6
431.9
159
70.6
467.0
437.5
160
71.1
472.5
443.1
Saturation pressures computed with CoolProp 8.0.0 (R427A.mix) on October 10, 2026, gauge pressure at sea level. Checked against Arkema published chart at 10 points; largest difference 0.52 psi. How these numbers are made.
What R-427A is and where it is used
R-427A is a four-part HFC blend of R-32, R-125, R-143a and R-134a, made by Arkema as Forane 427A. It is rated A1 and has zero ozone depletion potential. Arkema developed it as a retrofit for R-22 in low- and medium-temperature refrigeration and in air conditioning, so existing R-22 equipment can stay in service without new expansion valves or major components.
Arkema puts the capacity loss against R-22 at about 3% at a 45°F evaporator, with lower discharge temperatures than R-22. R-22 production and import ended in 2020. For other options, see R-22 replacements and R-422B.
How to read the R-427A chart
Arkema describes R-427A as a zeotropic blend, so the bubble and dew columns differ. At 40°F the chart gives 76.8 psig bubble and 61.2 psig dew. At a fixed pressure the glide is about 10.5°F at 60 psig and 7.9°F at 250 psig.
Superheat: convert suction pressure with the dew column. At 60 psig the dew point is 39.1°F. Try the superheat calculator.
Subcooling: convert liquid pressure with the bubble column. At 250 psig the bubble point is 110.1°F. Try the subcooling calculator.
Arkema warns that the R-427A pressure-temperature relationship differs from R-22, so the expansion valve may need adjusting after a retrofit. Background: bubble point, dew point and glide.
Typical R-427A pressures after an R-22 retrofit
Take a 40°F evaporator and a 110°F condenser as round example temperatures, not targets:
Suction (dew at 40°F): R-427A 61.2 psig, R-22 68.6 psig
Condensing at 110°F: R-427A 249.5 psig bubble and 221.9 psig dew, R-22 226.4 psig
Arkema's guidance is to expect suction pressure 0 to 5 psi lower and discharge pressure 0 to 10 psi higher than the same system ran on R-22, with lower superheat and subcooling, and higher pressures on high-load or high-ambient days. Arkema treats how the system ran on R-22 as the guide, and has techs add liquid to reach the target superheat or subcooling rather than an old R-22 pressure.
Retrofit and service notes
Charge as liquid only. Disposable cylinders have no dip tube, so turn them upside down. Where vapor would normally be charged, install a valve in the charging line to flash the liquid. Arkema warns that liquid introduced into a running system can damage the compressor.
Initial charge. Arkema suggests about 95% of the original R-22 charge by weight, up to 100% if needed.
Oil. Mineral oil or alkylbenzene is often acceptable if the system has an oil separator and good oil return on R-22. Otherwise change to POE. One oil change is usually enough because R-427A tolerates up to 15% residual oil. Arkema says tandem compressors without oil separators and chillers with large suction lines need a full change to POE.
Seals and drier. Replace the filter drier. Arkema recommends replacing seals and gaskets on any R-22 retrofit, and notes that in many HVAC systems the Schrader core is the only external seal involved.
Sight glass. Arkema says some bubbles at the compressor sight glass are normal for this zeotropic blend and do not by themselves mean an undercharge.
No mixing. Recover all the R-22 first. Arkema says a system already converted to R-427A can be topped off with liquid R-427A after a leak, but if a large part of the charge is lost, recover the rest and weigh in a new charge.