HVAC PT Charts
RefrigerantASHRAE R-421A

R421A PT Chart

Updated October 12, 2026

R-421A

A1 Lower toxicity, no flame propagationHFC blend AIM Act HFC
R-421A AHRI Guideline N service cylinderIllustration of a refrigerant cylinder painted light green gray (RAL 7044), the color AHRI Guideline N-2017 calls for on all new refrigerant containers from 2020. Label: R421A, safety class A1, GWP 2,631. No red band: AHRI Guideline N-2017 reserves it for flammable refrigerants.R421AA1GWP 2,631
Illustration of a refrigerant cylinder painted light green gray (RAL 7044), the color AHRI Guideline N-2017 calls for on all new refrigerant containers from 2020[1], section 4.8. Label: R-421A, safety class A1, GWP 2,631. No red band: AHRI Guideline N-2017 reserves it for flammable refrigerants[1], section 4.7.
R-125/R-134a (58/42)

Binary HFC blend (58% R-125 / 42% R-134a). Branded as Choice R-421A by ICOR International. ASHRAE A1, GWP 2,631. An R-22 retrofit option emphasizing simplicity (binary blend, mineral-oil compatible) over the lower-GWP alternatives.

R-421A saturation pressure splits across its glide: dew 58.1 PSIG at 40°F, bubble 197.4 PSIG at 100°F, and 108.3–122.0 PSIG dew-to-bubble at 70°F. Use the dew column for superheat and the bubble column for subcooling. The full table below runs from −40°F to 150°F in 1°F steps.

Not yet checked against an independent source.

Saturation @ 70°F
122.0 / 108.3 PSIG
GWP (100-yr)
2,631 US EPA value, 40 CFR 84.64(b)
Temperature glide
7.6°F
Boiling point
bubble −41.2°F / dew −31.7°F
Sourced facts
Temperature glide
7.6°F at a 40°F dew point[3]
R-421A PT calculator Superheat

R-421A PT chart — printable saturation table

Looking for the R-421A PT chart PDF for shop reference? The complete pressure-temperature saturation table is below: every 1° increment from −40°F to 150°F (or to the refrigerant's critical temperature). Use the Print / Save as PDF button in the table header to download a clean, table-only PDF (the rest of the page is hidden from the print output).

R-421A PT Chart — Pressure-Temperature Saturation Table

Computed with CoolProp 7.2.0 in 1°F steps · hvacptcharts.com

R-421A · 1° increments · °F / PSIG
Tinted rows: 32°F H₂O freeze
R-421A pressure-temperature saturation table in Fahrenheit and PSIG
Temp (°F)Bubble (PSIG)Dew (PSIG)
−40°F 0.56.1 in. Hg vac.
−39°F 0.95.5 in. Hg vac.
−38°F 1.34.8 in. Hg vac.
−37°F 1.74.1 in. Hg vac.
−36°F 2.13.3 in. Hg vac.
−35°F 2.52.6 in. Hg vac.
−34°F 3.01.8 in. Hg vac.
−33°F 3.41.1 in. Hg vac.
−32°F 3.90.3 in. Hg vac.
−31°F 4.40.3
−30°F 4.80.7
−29°F 5.31.1
−28°F 5.81.5
−27°F 6.31.9
−26°F 6.82.4
−25°F 7.42.8
−24°F 7.93.3
−23°F 8.43.7
−22°F 9.04.2
−21°F 9.64.7
−20°F 10.15.2
−19°F 10.75.7
−18°F 11.36.2
−17°F 11.96.7
−16°F 12.57.3
−15°F 13.27.8
−14°F 13.88.4
−13°F 14.48.9
−12°F 15.19.5
−11°F 15.810.1
−10°F 16.510.7
−9°F 17.211.3
−8°F 17.911.9
−7°F 18.612.6
−6°F 19.313.2
−5°F 20.113.9
−4°F 20.814.5
−3°F 21.615.2
−2°F 22.415.9
−1°F 23.216.6
0°F 24.017.3
1°F 24.818.1
2°F 25.618.8
3°F 26.519.6
4°F 27.420.3
5°F 28.221.1
6°F 29.121.9
7°F 30.022.7
8°F 30.923.6
9°F 31.924.4
10°F 32.825.2
11°F 33.826.1
12°F 34.827.0
13°F 35.827.9
14°F 36.828.8
15°F 37.829.7
16°F 38.830.7
17°F 39.931.6
18°F 40.932.6
19°F 42.033.6
20°F 43.134.6
21°F 44.235.6
22°F 45.436.6
23°F 46.537.7
24°F 47.738.7
25°F 48.939.8
26°F 50.140.9
27°F 51.342.0
28°F 52.543.2
29°F 53.844.3
30°F 55.045.5
31°F 56.346.7
32°F H₂O freeze57.647.9
33°F 59.049.1
34°F 60.350.3
35°F 61.751.6
36°F 63.052.8
37°F 64.454.1
38°F 65.855.4
39°F 67.356.8
40°F 68.758.1
41°F 70.259.5
42°F 71.760.9
43°F 73.262.3
44°F 74.763.7
45°F 76.365.2
46°F 77.866.6
47°F 79.468.1
48°F 81.169.6
49°F 82.771.1
50°F 84.372.7
51°F 86.074.3
52°F 87.775.9
53°F 89.477.5
54°F 91.279.1
55°F 92.980.8
56°F 94.782.4
57°F 96.584.1
58°F 98.385.9
59°F 100.287.6
60°F 102.089.4
61°F 103.991.2
62°F 105.893.0
63°F 107.894.8
64°F 109.796.7
65°F 111.798.5
66°F 113.7100.5
67°F 115.8102.4
68°F 117.8104.3
69°F 119.9106.3
70°F 122.0108.3
71°F 124.1110.4
72°F 126.3112.4
73°F 128.5114.5
74°F 130.7116.6
75°F 132.9118.7
76°F 135.2120.9
77°F 137.4123.1
78°F 139.7125.3
79°F 142.1127.5
80°F 144.4129.8
81°F 146.8132.1
82°F 149.2134.4
83°F 151.7136.7
84°F 154.1139.1
85°F 156.6141.5
86°F 159.1143.9
87°F 161.7146.4
88°F 164.3148.9
89°F 166.9151.4
90°F 169.5153.9
91°F 172.1156.5
92°F 174.8159.1
93°F 177.5161.7
94°F 180.3164.4
95°F 183.1167.1
96°F 185.9169.8
97°F 188.7172.5
98°F 191.6175.3
99°F 194.4178.1
100°F 197.4181.0
101°F 200.3183.9
102°F 203.3186.8
103°F 206.3189.7
104°F 209.4192.7
105°F 212.4195.7
106°F 215.5198.7
107°F 218.7201.8
108°F 221.8204.9
109°F 225.0208.0
110°F 228.3211.2
111°F 231.5214.4
112°F 234.8217.7
113°F 238.2220.9
114°F 241.5224.2
115°F 244.9227.6
116°F 248.4231.0
117°F 251.8234.4
118°F 255.3237.8
119°F 258.9241.3
120°F 262.4244.9
121°F 266.0248.4
122°F 269.7252.0
123°F 273.4255.7
124°F 277.1259.3
125°F 280.8263.1
126°F 284.6266.8
127°F 288.4270.6
128°F 292.3274.4
129°F 296.1278.3
130°F 300.1282.2
131°F 304.0286.2
132°F 308.0290.2
133°F 312.1294.2
134°F 316.2298.3
135°F 320.3302.4
136°F 324.4306.6
137°F 328.6310.8
138°F 332.9315.0
139°F 337.1319.3
140°F 341.5323.6
141°F 345.8328.0
142°F 350.2332.4
143°F 354.6336.9
144°F 359.1341.4
145°F 363.6346.0
146°F 368.2350.6
147°F 372.8355.2
148°F 377.4359.9
149°F 382.1364.7
150°F 386.9369.5
CoolProp 7.2.0 · PSIG/kPa = gauge · PSIA = PSIG + 14.6959 · kPa(abs) = kPa(gauge) + 101.325

Full saturation values at 1° increments. Toggle between °F / PSIG and °C / kPa. Use Print / Save as PDF for laminated shop reference, or download the CSV / JSON below for use in other tools. R-421A PT chart data: CoolProp 7.2.0 (published Helmholtz equations of state / mixture models — see the source citations above).

A1
Lower toxicity, no flame propagation

Lower toxicity (Occupational Exposure Limit ≥ 400 ppm). No flame propagation in air at standard atmospheric pressure and 60°C. R-134a, R-22, R-410A, R-404A, R-744 (CO2) are A1.

Flammability
None (no flame propagation)
Toxicity
Lower (OEL ≥ 400 ppm)

Classification per ANSI/ASHRAE Standard 34-2022. See full reference.

Saturation pressure-temperature curve

Pressure
Temperature
°F
70°F: 122.0 PSIG (bubble)108.3 PSIG (dew)
Quick lookup — R-421A
122.0 / 108.3PSIG(841 / 747 kPa)
Bubble Dew· zeotropic blend
Range: −40 to 150°F Open full PT calculator →
Common service temperatures
32°F
58 / 48PSIG
Freezing
45°F
76 / 65PSIG
Heat-pump heat
70°F
122 / 108PSIG
Standard
75°F
133 / 119PSIG
Test ref
80°F
144 / 130PSIG
Warm
95°F
183 / 167PSIG
Summer peak

Saturation values from CoolProp 7.2.0 mixture model: R-125/R-134a, 58/42% by mass[3]. Operating pressure on a running system differs — see the operating-pressure references for in-use values.

At a glance

Chemistry

R-125/R-134a (58/42)
Binary HFC blend

Lubricant compatibility

POEMOAB

R-22 retrofit option. Mineral oil compatibility makes it a low-effort retrofit choice.

Blend composition

  • R-125 58.0%
  • R-134a 42.0%

Trade names

  • Choice R-421A — ICOR International

Common applications

  • R-22 retrofit (commercial AC, heat pumps)
  • Medium-temperature refrigeration

Properties

  • Boiling point (1 atm)
    bubble −41.2°F (−40.7°C), dew −31.7°F (−35.4°C)
  • Critical point
    No single point — blend critical locus
  • Molar mass
    111.75 g/mol
  • Temperature glide
    7.6°F
  • ODP
    0
  • GWP (100-yr)
    2,631 US EPA value, 40 CFR 84.64(b) IPCC: AR4 2,631 · AR5 2,385 · AR6 2,812
  • New-equipment status (US)
    Restricted in 48 new-equipment categories — US new-equipment rules (40 CFR 84.54).

What is R-421A?

R-421A is a binary blend of 58% R-125 and 42% R-134a by mass, developed by ICOR International as an R-22 retrofit refrigerant. The binary composition (only two components) simplifies manufacturing compared to the 3- and 5-component R-22 retrofit blends.

Compared to other "MO-compatible" R-22 retrofit options (R-417A, R-422A, R-422D, R-427A, R-438A), R-421A's lack of a hydrocarbon component means it relies on the HFC components themselves for mineral-oil miscibility — this works in practice for most R-22 retrofit applications but with somewhat less margin than the hydrocarbon-aided blends.

Where R-421A is used

  • R-22 retrofit (residential AC, heat pumps, light commercial)
  • Medium-temperature commercial refrigeration (R-22 retrofit)
  • Existing R-22 equipment service where oil change is impractical

Regulatory & phase-down status

R-421A's GWP of 2,631 is above every applicable 40 CFR 84.54 GWP limit for new equipment — for example the 700 limit for new residential and light-commercial AC and heat pumps (84.54(a)(1),(c)(1)). For new installations R-421A is not the choice; for R-22 retrofit work it remains commercially available.

The R-22 retrofit market itself is shrinking as the R-22 installed base ages out. New equipment installations use R-454B / R-32 / R-452B (residential AC) or R-448A / R-449A (commercial refrigeration) rather than refrigerant-only R-22 retrofits.

Service notes

Compatible with mineral oil (MO), alkylbenzene (AB), and POE oils. R-421A has moderate temperature glide (~7-8°F at typical operating pressures); TXV operation may require retuning after retrofit.

Temperature glide

Temperature glide across evaporator at constant pressureR-421A at 69 PSIG suction→ refrigerant flow →Entry: 40.0°F Mid: 43.7°F Exit: 47.4°F Glide = 7.4°F Position along evaporator coil40°F 47°F

R-421A is a zeotropic blend: at constant pressure it boils across a temperature range rather than at a single point. Use the dew curve for superheat, bubble curve for subcooling.

Operating cycle

CompressorRaises pressureCondenserRejects heat to outdoorsExpansion deviceDrops pressureEvaporatorAbsorbs heat from indoorsDischarge: 228 PSIG, 180°F Liquid: 228 PSIG, 100°F Evap inlet: 58 PSIG, 40°F (two-phase)Suction: 58 PSIG, 50°F Example cycle for R-421A (40°F evap, 110°F condenser, 10°F superheat, 10°F subcooling)

Phase-down timeline

R-421A contains HFC-125 and HFC-134a, regulated substances under the AIM Act. Its GWP under 40 CFR 84.64 is 2,631, at or above the limit in 48 of the categories 40 CFR 84.54 restricts (listed under “All 84.54 categories restricting R-421A”).

  • From January 1, 2025 — new self-contained residential & light-commercial AC and heat pump products: manufacture / import restricted (GWP ≥ 700).
  • From January 1, 2025 — new residential & light-commercial AC and heat pump systems (except VRF): installation restricted (GWP ≥ 700), unless every specified component was manufactured or imported before January 1, 2025.
  • From January 1, 2026 — new variable refrigerant flow (VRF) residential & light-commercial AC and heat pump systems: installation restricted (GWP ≥ 700); systems whose specified components were all manufactured or imported before January 1, 2026 may be installed until January 1, 2027, or until January 1, 2028 when a building permit issued before October 5, 2023 specifies the refrigerant.
  • From January 1, 2028 — new self-contained residential & light-commercial AC and heat pump products: sale and distribution restricted (GWP ≥ 700).

HFC production & consumption allowances step down to 30% of baseline in 2029–2033, 20% of baseline in 2034–2035, and 15% of baseline in 2036 and later (42 U.S.C. 7675(e)(2)(C)).

Full 40 CFR 84.54 new-equipment rules for R-421A →

US new-equipment rules (40 CFR 84.54)

R-421A contains HFC-125 and HFC-134a, regulated substances under the AIM Act. Under 40 CFR 84.64(b) its GWP is 2,631: each component's GWP times its mass fraction; components without a GWP under 84.64 are left out (84.64(c)). That value is compared against each 40 CFR 84.54 subsector limit below.

EffectiveEquipment subsectorLimitRestriction
January 1, 2025Self-contained residential & light-commercial AC and heat pump productsGWP ≥ 700Manufacture / import(a)(1)
January 1, 2025Residential & light-commercial AC and heat pump systems (except VRF)GWP ≥ 700Installation(c)(1)
January 1, 2026Variable refrigerant flow (VRF) residential & light-commercial AC and heat pump systemsGWP ≥ 700Installation(c)(2)
January 1, 2028Self-contained residential & light-commercial AC and heat pump productsGWP ≥ 700Sale / distribution(b)
All 84.54 categories restricting R-421A (48)
Refrigeration, air conditioning & heat pumps (41)
January 1, 2025Self-contained residential & light-commercial AC and heat pump productsGWP ≥ 700(a)(1)
January 1, 2025Chillers for comfort coolingGWP ≥ 700(a)(10)(i)
January 1, 2025Chillers for ice rinksGWP ≥ 700(a)(10)(ii)
January 1, 2025Residential dehumidifiersGWP ≥ 700(a)(2)
January 1, 2025Household refrigerators and freezersGWP ≥ 150(a)(3)
January 1, 2025Retail food refrigeration — stand-alone unitsGWP ≥ 150(a)(4)
January 1, 2025Vending machinesGWP ≥ 150(a)(5)
January 1, 2025Refrigerated transport — road and marine (self-contained products)listed refrigerant(a)(7)
January 1, 2025Residential & light-commercial AC and heat pump systems (except VRF)GWP ≥ 700(c)(1)
January 1, 2025Chillers for comfort coolingGWP ≥ 700(c)(3)
January 1, 2025Ice rinksGWP ≥ 700(c)(4)
January 1, 2025Refrigerated transport — road or marine systemslisted refrigerant(c)(8)
January 1, 2026Chillers for industrial process refrigeration, fluid exiting the chiller warmer than −22°F (−30°C)GWP ≥ 700(a)(10)(iii)
January 1, 2026Industrial process refrigeration products (non-chiller), charge 200 lb or greater, refrigerant entering the evaporator warmer than −22°F (−30°C)GWP ≥ 150(a)(12)(i)
January 1, 2026Industrial process refrigeration products (non-chiller), charge less than 200 lb, refrigerant entering the evaporator warmer than −22°F (−30°C)GWP ≥ 300(a)(12)(ii)
January 1, 2026Ice makers — batch type up to 1,000 lb of ice per 24 h and continuous type up to 1,200 lb per 24 hGWP ≥ 150(a)(8)(i)
January 1, 2026Industrial process refrigeration systems (non-chiller), charge 200 lb or greater, evaporator inlet warmer than −22°F (−30°C), not the high-temperature side of a cascadeGWP ≥ 150(c)(10)(i)
January 1, 2026Industrial process refrigeration systems (non-chiller), charge less than 200 lb, evaporator inlet warmer than −22°F (−30°C)GWP ≥ 300(c)(10)(ii)
January 1, 2026Industrial process refrigeration — high-temperature side of cascade systems, evaporator inlet warmer than −22°F (−30°C)GWP ≥ 300(c)(10)(iii)
January 1, 2026Variable refrigerant flow (VRF) residential & light-commercial AC and heat pump systemsGWP ≥ 700(c)(2)
January 1, 2026Chillers for industrial process refrigeration, fluid exiting the chiller warmer than −22°F (−30°C)GWP ≥ 700(c)(5)(i)
July 27, 2026Refrigerated transport — intermodal containers with a box temperature of −31°F (−35°C) or higherGWP ≥ 700(a)(6)
July 27, 2026Retail food refrigeration — remote condensing unitsGWP ≥ 1,400(c)(11)(i)
July 27, 2026Refrigerated transport — intermodal containers with a box temperature of −31°F (−35°C) or higherGWP ≥ 700(c)(7)
July 27, 2026Cold storage warehouse systemsGWP ≥ 700(c)(9)(i)
January 1, 2027Self-contained products in data center, information technology equipment facility, and computer room coolingGWP ≥ 700(a)(11)
January 1, 2027Ice makers — batch type above 1,000 lb of ice per 24 h and continuous type above 1,200 lb per 24 hlisted refrigerant(a)(8)(ii)
January 1, 2027Refrigerated food processing and dispensing products outside the scope of UL 621, charge 500 g or lessGWP ≥ 150(a)(9)(i)
January 1, 2027Refrigerated food processing and dispensing products outside the scope of UL 621, charge greater than 500 glisted refrigerant(a)(9)(ii)
January 1, 2027Supermarket systemsGWP ≥ 1,400(c)(12)(i)
January 1, 2027Data center, information technology equipment facility, and computer room cooling systemsGWP ≥ 700(c)(13)
January 1, 2027Automatic commercial ice machines with a remote condenserlisted refrigerant(c)(14)
January 1, 2027Refrigerated food processing and dispensing equipment with a remote condenserlisted refrigerant(c)(15)
January 1, 2028Chillers for industrial process refrigeration, fluid exiting the chiller from −58°F to −22°F (−50°C to −30°C)GWP ≥ 700(a)(10)(iv)
January 1, 2028Industrial process refrigeration products (non-chiller), refrigerant entering the evaporator from −58°F to −22°F (−50°C to −30°C)GWP ≥ 700(a)(12)(iii)
January 1, 2028Refrigerated food processing and dispensing products within the scope of UL 621 (ice cream makers)listed refrigerant(a)(9)(iii)
January 1, 2028Industrial process refrigeration systems (non-chiller), evaporator inlet from −58°F to −22°F (−50°C to −30°C)GWP ≥ 700(c)(10)(iv)
January 1, 2028Chillers for industrial process refrigeration, fluid exiting the chiller from −58°F to −22°F (−50°C to −30°C)GWP ≥ 700(c)(6)(i)
January 1, 2032Retail food refrigeration — remote condensing unitsGWP ≥ 150 (200 lb or greater, not the cascade high side); GWP ≥ 300 (less than 200 lb); GWP ≥ 300 (cascade high side)(c)(11)(ii)
January 1, 2032Supermarket systemsGWP ≥ 150 (200 lb or greater, not the cascade high side); GWP ≥ 300 (less than 200 lb); GWP ≥ 300 (cascade high side)(c)(12)(ii)
January 1, 2032Cold storage warehouse systemsGWP ≥ 150 (200 lb or greater, not the cascade high side); GWP ≥ 300 (less than 200 lb); GWP ≥ 300 (cascade high side)(c)(9)(ii)
Motor vehicle air conditioning (3)
October 24, 2024Motor vehicle air-conditioning in Model Year 2025 and later light-duty passenger cars and trucks (gross vehicle weight rating under 8,500 lb)GWP ≥ 150(a)(13)(i)
Model Year 2028Motor vehicle air-conditioning in medium-duty passenger vehicles, heavy-duty pickup trucks and complete heavy-duty vans whose air-conditioning will not be modified by upfittersGWP ≥ 150(a)(13)(ii)
January 1, 2028Motor vehicle air-conditioning in certain nonroad vehicles (agricultural tractors over 40 horsepower; self-propelled agricultural machinery; compact equipment; construction, forestry and mining equipment; and commercial utility vehicles)GWP ≥ 150(a)(13)(iii)
Foam blowing agents (2)
January 1, 2025Foam products: rigid polyurethane appliance foam, commercial refrigeration foam, laminated boardstock, marine flotation foam, sandwich panels, slabstock; flexible polyurethane; integral skin polyurethane; polystyrene (extruded boardstock, billet, extruded sheet); phenolic insulation board and bunstock; polyisocyanurate laminated boardstock; polyolefin; rigid polyurethane spray foamGWP ≥ 150(a)(14)
January 1, 2026Foam products in the (a)(14) formulations for use in space and military applicationsGWP ≥ 150(a)(15)
Aerosol propellants / solvents (2)
January 1, 2025Aerosol productsGWP ≥ 150(a)(16)(i)
January 1, 2028Aerosol products (all, except defense sprays as defined in 84.3)GWP ≥ 150(a)(16)(ii)

Servicing. 40 CFR 84.54 restricts new manufacture/import, later sale/distribution, and installation. "Installation" is defined in 84.54(e); repairing or servicing existing R-421A equipment is not an installation unless it meets 84.54(e), so existing systems can keep being serviced. From January 1, 2029, servicing or repairing R-421A equipment in supermarket systems, refrigerated transport or automatic commercial ice makers must be done with reclaimed refrigerant[2].

Source: 40 CFR 84.54, current through 91 FR 31329 (May 26, 2026). Installation defined at 40 CFR 84.54(e).

Global warming potential, in context

R-22 retrofit blends

R-407C1.8kR-221.8kR-427A2.1kR-438A2.3kR-417A2.3kR-422B2.5kR-421A2.6kR-422D2.7kR-422A3.1k

Retrofit and replacement paths

R-421A replaces

Replacements for R-421A

R-421A vs R-22, R-32, R-454B: saturation pressure

Saturation pressure (PSIG, gauge) for R-421A vs R-22, R-32, R-454B — zeotropic blends shown as dew / bubble. Each column shows the percent difference from R-421A. Source: CoolProp 7.2.0 dataset.
TempR-421AR-22R-32R-454B
0°F17.3 / 24.024.0(+0%)49.3(+105%)42.7 / 45.3(+89%)
40°F58.1 / 68.768.6(−0%)121.0(+76%)107.0 / 112.0(+63%)
70°F108.3 / 122.0121.4(−0%)205.8(+69%)183.1 / 190.5(+56%)
100°F181.0 / 197.4195.9(−1%)325.7(+65%)290.9 / 300.8(+52%)

Frequently asked

›How does R-421A compare to R-417A for R-22 retrofit?

Similar function (MO-compatible R-22 retrofit blends) with composition differences. R-421A is binary (R-125/R-134a only); R-417A is ternary (R-125/R-134a/R-600 — the hydrocarbon component aids miscibility). R-421A: GWP 2,631. R-417A: GWP 2,346, hydrocarbon-aided mineral oil miscibility. Both are AIM-Act-affected and not for new equipment; the choice between them is largely distributor availability and contractor preference.

›What is the normal operating pressure of R-421A?

Operating pressure depends on evaporator load and ambient. The saturation pressures are in the PT table and the comparison table on this page.

›What lubricant does R-421A use?

Compatible with mineral oil (MO), alkylbenzene (AB), and POE. The hydrocarbon-free binary blend has somewhat less miscibility margin than hydrocarbon-aided R-22 retrofit blends (R-417A, R-422 series, R-438A) but works in practice for most retrofits.

›Does R-421A have temperature glide?

Yes — about 7-8°F at typical evaporator pressures. Use the dew curve for superheat measurement. TXV systems may require retuning after retrofit; EXV systems handle the glide automatically.

›Should I use R-421A or replace the R-22 equipment?

Same economic analysis as other R-22 retrofits. For equipment less than ~10 years old in good condition with no other major issues, R-421A retrofit can be cost-effective. For older equipment with multiple service-life concerns, full replacement with modern R-454B / R-32 equipment provides better long-term value through higher efficiency and longer expected service life.

›Is R-421A a near-azeotrope?

No — R-421A has meaningful temperature glide (~7-8°F at typical operating pressures), placing it in the zeotropic category. This is similar to other R-22 retrofit blends in this family (R-417A, R-422 series). For service work treat it as a zeotrope: dew curve for superheat, bubble curve for subcooling, charge by weight not by gauge.

›What is the GWP of R-421A?

2631 (mass-weighted from R-125 and R-134a components). This is higher than R-22's GWP of 1,810. Like other R-22 retrofit HFC blends, the GWP exchange isn't favorable on a per-pound basis — the retrofit's value is operational continuity (no equipment replacement) rather than climate-impact reduction.

Download this dataset

Full PT chart for R-421A · CC BY 4.0 · attribute the source

CSV JSON

Sources & citations

  1. [1]
    2017 Guideline for Assignment of Refrigerant Container Colors (AHRI Guideline N-2017). AHRI. 2017. https://www.ahrinet.org/system/files/2023-06/AHRI_Guideline_N_2017.pdf (accessed October 2, 2026)
  2. [2]
    40 CFR 84.112 — Reclamation. eCFR (Office of the Federal Register). up to date as of 9/25/2026. https://www.ecfr.gov/current/title-40/chapter-I/subchapter-C/part-84/subpart-C/section-84.112 (accessed October 2, 2026). 89 FR 82859, Oct. 11, 2024
  3. [3]
    CoolProp 7.2.0. CoolProp (I. H. Bell, J. Wronski, S. Quoilin, V. Lemort). https://coolprop.org/ (accessed October 2, 2026). Bell, I. H.; Wronski, J.; Quoilin, S.; Lemort, V. Pure and Pseudo-pure Fluid Thermophysical Property Evaluation and the Open-Source Thermophysical Property Library CoolProp. Ind. Eng. Chem. Res. 53, 2498–2508 (2014). https://doi.org/10.1021/ie4033999

Data sources & provenance

PT chart
CoolProp 7.2.0 mixture model: R-125/R-134a, 58/42% by mass
Properties
CoolProp 7.2.0 + ASHRAE Standard 34-2022
GWP (100-yr)
US EPA value, 40 CFR 84.64(b) · IPCC AR4/AR5/AR6 on the GWP rankings
Table computed
October 2026

Reference material. Always verify pressure values against the equipment data plate and manufacturer service literature before charging or troubleshooting a specific system. Saturation pressure differs from operating pressure — see superheat & subcooling fundamentals. See how this PT table is calculated in our methodology.