R-404A vs R-507A
Reviewed · pressures computed with CoolProp 8.0 from the same data as the PT charts
Can you mix R-404A and R-507A?
No. They are different blends: R-404A is a three-component near-azeotrope, R-507A a two-component azeotrope that runs 3.8 psi higher at 40°F evaporating. A mixture matches neither PT chart. Changing refrigerant means recovering the full charge, evacuating and recharging.
Pressures side by side
Saturation pressure in psig at sea level. Evaporating rows use the vapor (dew) value, condensing rows the liquid (bubble) value, which is what you compare with suction and liquid-line gauges. The last column is R-507A minus R-404A.
| Saturation | R-404A | R-507A | Difference |
|---|---|---|---|
| Evaporator (vapor, dew) | |||
| -20°F | 16.0 | 17.6 | +1.6 (+10%) |
| 0°F | 32.6 | 34.8 | +2.2 (+7%) |
| 20°F | 55.3 | 58.2 | +2.9 (+5%) |
| 30°F | 69.3 | 72.7 | +3.3 (+5%) |
| 35°F | 77.1 | 80.7 | +3.6 (+5%) |
| 40°F | 85.4 | 89.2 | +3.8 (+4%) |
| 45°F | 94.2 | 98.3 | +4.0 (+4%) |
| 50°F | 103.6 | 107.9 | +4.3 (+4%) |
| Condenser (liquid, bubble) | |||
| 80°F | 175.4 | 179.6 | +4.2 (+2%) |
| 90°F | 204.5 | 209.3 | +4.9 (+2%) |
| 95°F | 220.2 | 225.4 | +5.2 (+2%) |
| 100°F | 236.8 | 242.3 | +5.5 (+2%) |
| 105°F | 254.2 | 260.1 | +5.9 (+2%) |
| 110°F | 272.5 | 278.8 | +6.3 (+2%) |
| 115°F | 291.8 | 298.5 | +6.7 (+2%) |
| 120°F | 312.1 | 319.2 | +7.2 (+2%) |
| 125°F | 333.3 | 340.9 | +7.6 (+2%) |
| 130°F | 355.7 | 363.8 | +8.1 (+2%) |
Properties
| Property | R-404A | R-507A |
|---|---|---|
| Safety class | A1 | A1 |
| Type | HFC, near-azeotropic blend | HFC, azeotropic blend |
| Composition (mass %) | R-125 44, R-143a 52, R-134a 4 | R-125 50, R-143a 50 |
| GWP (AR4) | 3,922 | 3,985 |
| Lubricant | POE (polyolester) | POE (polyolester) |
| Boiling point (14.7 psia) | -51.2°F | -52.1°F |
| Critical point | 161.8°F, 542 psia | 159.1°F, 537 psia |
| Glide at 40°F evaporating | 0.9°F | 0.0°F |
| Glide at 100°F condensing | 0.6°F | 0.1°F |
| US status | Legal to service existing systems; barred in most new commercial refrigeration under 40 CFR 84.54, with reclaimed refrigerant required for supermarket, transport and ice-maker service from Jan 1 2029. | Legal to service; barred in most new commercial refrigeration and transport under 40 CFR 84.54, with reclaimed refrigerant required for supermarket, transport and ice-maker service from Jan 1 2029. |
Component compatibility
| Item | R-404A | R-507A |
|---|---|---|
| Lubricant | POE | POE |
| Blend type | Near-azeotrope (R-125/R-143a/R-134a) | Azeotrope (R-125/R-143a) |
| Charging | Liquid | Liquid (Arkema) |
| Section 608 | High-pressure, Type II | High-pressure, Type II |
| Recovery machine | AHRI 740 machine (App. B3) | AHRI 740 machine (App. B3) |
| Cylinder | RAL 7044 gray (legacy orange) | RAL 7044 gray (legacy blue-green) |
| New RCU | Not allowed (GWP 3,922) | Not allowed (GWP 3,985) |
| Servicing existing systems | Allowed | Allowed |
What changes in the field
Very little on the gauges. From the PT data, at 40°F evaporating (dew) R-404A reads 85.4 psig and R-507A 89.2 psig. At -20°F the gap is 1.6 psi, and at 100°F condensing (bubble) R-404A is 236.8 psig and R-507A 242.3 psig. Both are high-pressure appliances under Section 608, so Type II or Universal certification covers both.
The real difference is the blend. R-404A is R-125/R-143a/R-134a (44/52/4 by mass) and shows a small glide, about 0.9°F at 40°F evaporating. R-507A is R-125/R-143a (50/50), an azeotrope with practically no glide. On R-404A, read the dew column for superheat and the bubble column for subcooling. On R-507A the two columns are effectively the same. Use the superheat calculator and subcooling calculator with the refrigerant actually on the nameplate.
Both run on POE. Copeland lists POE-32 for both, and Arkema says that when converting an R-502 system to R-507A, residual mineral oil should be brought down to 5% or less. Both should be charged as liquid. Arkema says R-507A “should be charged in liquid phase” even though it is an azeotrope, and you can flash it through a metering valve if vapor feed is needed.
Cylinders are now the same RAL 7044 light green-gray under AHRI Guideline N-2017. The legacy label colors are orange for R-404A and blue-green (teal) for R-507A, so read the label, not the paint.
Retrofit or replacement
Do not top off one with the other. The mixture is not an ASHRAE-designated refrigerant, so no PT chart matches it. You can’t set superheat or subcooling properly on it, and the system can no longer be serviced by the nameplate. If a system must change from one to the other:
- Recover the full charge into a dedicated, labeled recovery cylinder. For high-pressure appliances that means 0 in Hg under 200 lb and 10 in Hg at 200 lb or more (equipment made on or after Nov 15 1993).
- Replace the filter-drier, evacuate and leak check.
- Charge the new refrigerant as liquid, then set superheat and subcooling to the equipment maker’s targets.
- Relabel the system with the refrigerant and oil.
The oil can stay because both run on POE. In practice, though, few owners convert between these two. Both have GWPs near 4,000 and face the same rules, so a conversion usually goes to a lower-GWP blend. Chemours lists its Opteon XP40 (R-449A) as a replacement for both R-404A and R-507, and R-448A is the other common choice. The options are compared on the R-404A replacement page and in R-448A vs R-449A.
Capacity, efficiency and cost
None of the sources here gives a capacity or efficiency comparison between R-404A and R-507A. Rated equipment data from the system maker is the place to look.
Both are in the same regulatory position. On the AR4 basis, R-404A is 3,922 and R-507A is 3,985. Under 40 CFR 84.54 as amended by 91 FR 31284, new remote condensing units are limited to GWP below 1,400 from July 27 2026, and new supermarket systems from Jan 1 2027. New cold storage is limited to 700 from July 27 2026. Both refrigerants exceed all three limits. EPA SNAP already listed both as unacceptable in new cold storage warehouses from Jan 1 2023.
Servicing existing equipment with either refrigerant remains legal. From Jan 1 2029, servicing supermarket systems, refrigerated transport and automatic commercial ice makers must use reclaimed HFC. Supply sits under the AIM Act phasedown: allowances are 60% of baseline in 2024–2028 and 30% in 2029–2033. See AIM Act refrigerant rules.
Common questions
What is the difference between R-404A and R-507A?
R-404A has 4% R-134a in it and is a near-azeotrope with a small glide. R-507A is only R-125 and R-143a and behaves like a single fluid. Pressures are close, with R-507A a few psi higher, and both use POE.
Can you still use R-404A?
Yes, for servicing existing systems. New remote condensing units, supermarket systems and cold storage cannot be built with it under the 2026 limits.
PT charts and calculators
Sources
- ASHRAE Refrigerant Designations (Standard 34 numbers and blend compositions) ashrae.org
- Arkema Forane Technical Digest forane.arkema.com
- Copeland AE Bulletin 93-11: Refrigerants and Lubricants Approved for Use in Copeland Compressors webapps.copeland.com
- 40 CFR 84.54: Technology Transitions restrictions by sector ecfr.gov
- 91 FR 31284 (May 26 2026): Phasedown of HFCs, reconsideration of Technology Transitions requirements federalregister.gov
- EPA SNAP: Substitutes in Cold Storage Warehouses epa.gov
- Chemours Opteon XP40 (R-449A) product information C-10021 meiersupply.com
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