What R-404A is and where it is used
R-404A is a near-azeotropic blend of R-125, R-143a and R-134a (44/52/4 by weight). Arkema says it was formulated to closely match R-502 and has been approved by many compressor and system makers for new medium- and low-temperature refrigeration equipment: food display and storage cases, cold storage rooms, ice machines, transport and process refrigeration. Arkema also lists it as a replacement or retrofit for R-22 in that work. It is ASHRAE safety group A1. Its 100-year GWP is 3922 (AR4) or 3943 (AR5), far above the limits EPA now sets for new stand-alone retail food units, remote condensing units, supermarket systems and cold storage warehouses.
How to read the R-404A chart
R-404A has a small glide, so the chart gives a bubble (liquid) and a dew (vapor) pressure for each temperature. At 55 psig the dew point is 19.8°F and the bubble point 18.8°F, only 1.0°F apart, but use the right column anyway.
- Superheat: convert suction pressure with the dew column. A freezer suction of 16 psig is -20.0°F. Subtract that from the suction line temperature measured at the same point.
- Subcooling: convert liquid pressure with the bubble column. At 250 psig the bubble point is 103.8°F. Subtract the liquid line temperature from it.
The superheat calculator and subcooling calculator select the column for you. Bubble point, dew point and glide explains the difference.
Example R-404A pressures in refrigeration
Pressures follow the saturation temperatures in the coils. The figures below are worked examples at assumed coil temperatures, not targets for any system:
- Freezer: an evaporator at a -20°F dew point runs about 16.0 psig suction.
- Cooler: an evaporator at a 20°F dew point runs about 55.3 psig.
- Head: at 105°F and 115°F condensing (bubble) temperatures, head pressure is 254.2 psig and 291.8 psig.
Set the charge and controls from the equipment manufacturer's data.
Service notes
- Charging: Arkema says R-404A should be charged as liquid to prevent fractionation. Where vapor is normally charged into a system, install a valve in the charging line that flashes the liquid to vapor.
- Leaks: Arkema reports that testing shows fractionation from system leaks is typically not a problem with R-404A: fix the leak and top off the charge.
- Oil: POE. When converting an R-502 system, Arkema says to replace the original oil with POE and reduce the old oil to 5% or less of the original charge. Consult the equipment maker on pressure relief, because R-404A runs higher pressures than R-502.
Regulations and replacements
EPA's Technology Transitions rule, as amended in May 2026, set a GWP limit of 150 for new stand-alone retail food units from 2025. New remote condensing units installed from July 27, 2026 and new supermarket systems installed from January 1, 2027 face an interim limit of 1,400 until January 1, 2032. New cold storage warehouses face 700 from July 27, 2026. R-404A exceeds all of these, and EPA also names it as prohibited in new road and marine refrigerated transport from January 1, 2025. EPA says existing products and systems can be serviced and repaired throughout their useful life.
Lower-GWP replacements offered by refrigerant makers include R-448A (GWP 1,386) and R-449A (GWP 1,396), both under the 1,400 interim limit, and R-407A (GWP 2107). R-448A runs lower suction pressure than R-404A at the same coil temperature: 44.1 psig against 55.3 psig dew at 20°F. National Refrigerants advises closing R-404A expansion valves 1 to 2 turns after a retrofit to R-448A, then adjusting superheat. For R-449A, Chemours says retrofits require TXV adjustment and in most cases suggests replacing the R-404A power element with an R-449A one. Follow the refrigerant maker's retrofit guide.