R-404A PT Chart
Saturation pressure for R-404A from -40°F to 150°F. Look up a pressure or temperature, switch to metric, and check typical operating pressures.
By BrazeJobs Team · Updated
R-404A Lookup
Saturation Pressure
84.4 psig
Saturation Temp
39.8°F
Chart range: -40°F to 150°F. Enter vacuum as a negative pressure. Check R-404A superheat and subcooling
R-404A PT Chart
| Temp | Pressure |
|---|---|
| -40°F | 4.3 psig |
| -35°F | 6.8 psig |
| -30°F | 9.5 psig |
| -25°F | 12.5 psig |
| -20°F | 15.7 psig |
| -15°F | 19.3 psig |
| -10°F | 23.2 psig |
| -5°F | 27.5 psig |
| 0°F | 32.1 psig |
| 5°F | 37.0 psig |
| 10°F | 42.4 psig |
| 15°F | 48.2 psig |
| 20°F | 54.5 psig |
| 25°F | 61.2 psig |
| 30°F | 68.4 psig |
| 35°F | 76.1 psig |
| 40°F | 84.4 psig |
| 45°F | 93.2 psig |
| 50°F | 103.0 psig |
| 55°F | 113.0 psig |
| 60°F | 123.0 psig |
| 65°F | 135.0 psig |
| 70°F | 147.0 psig |
| 75°F | 159.0 psig |
| 80°F | 173.0 psig |
| 85°F | 187.0 psig |
| 90°F | 202.0 psig |
| 95°F | 218.0 psig |
| 100°F | 234.0 psig |
| 105°F | 252.0 psig |
| 110°F | 270.0 psig |
| 115°F | 289.0 psig |
| 120°F | 310.0 psig |
| 125°F | 331.0 psig |
| 130°F | 353.0 psig |
| 135°F | 377.0 psig |
| 140°F | 401.0 psig |
| 145°F | 426.0 psig |
| 150°F | 453.0 psig |
About R-404A
R-404A is an HFC blend built for low- and medium-temperature commercial refrigeration. For years it was the default in walk-in freezers, reach-ins, ice machines and supermarket cases.
It has the highest GWP of the common refrigerants, which is why it is being replaced. Its glide is small, about 1°F. Hudson publishes one pressure column for R-404A, which tracks the vapor (dew) pressure, so the chart below shows one column.
In a walk-in freezer, the evaporator typically runs 10 to 15°F below the box temperature, so a -10°F box means an evaporator around -20 to -25°F. The chart turns that into the suction pressure you should see, and it is the same conversion you use to set low pressure control cut-in and cut-out points for a given box temperature.
- Walk-in coolers and freezers
- Reach-in and display cases, ice machines
- Supermarket racks and transport refrigeration
R-404A Properties
Key facts for identifying R-404A and choosing tools, oil and replacements.
| Property | Value |
|---|---|
| Type | HFC |
| Composition | R-143a 52%, R-125 44%, R-134a 4% by weight |
| ASHRAE safety class | A1 |
| GWP (IPCC AR4) | 3,922 |
| Boiling point at 1 atm | -51.8°F |
| Critical temperature | 162.5°F |
| Oil | POE (polyolester) |
| Trade names | Suva HP62, Genetron 404A, Forane 404A |
| Replaces | None |
| Replaced by | R-448A, R-290 |
Typical R-404A Operating Pressures
Suction pressure is the vapor (dew) pressure at the evaporator temperature; head pressure is the liquid (bubble) pressure at the condensing temperature. The temperatures are common design points, not charging targets.
| Condition | Evaporator | Suction | Condensing | Head |
|---|---|---|---|---|
| Walk-in cooler (medium temp) | 20°F | 54.5 psig | 110°F | 270.0 psig |
| Walk-in freezer (low temp) | -20°F | 15.7 psig | 110°F | 270.0 psig |
How to Read the R-404A PT Chart
The chart covers -40°F to 150°F. Pressures are gauge pressure (psig), the number your manifold shows; switch to °C and kPa above if you work in metric.
The chart has one pressure column because liquid and vapor share the same saturation pressure at each temperature. Use the same column for superheat (suction side) and subcooling (liquid side).
To read it, find the pressure on your gauge and read across to the saturation temperature, or start from a temperature and read the pressure. The lookup above interpolates between rows for you.
Superheat and Subcooling Formulas
The PT chart turns a gauge pressure into a saturation temperature. Compare that with a line temperature to get superheat or subcooling.
- Tsuction
- Suction line temperature near the outdoor unit or compressor, °F
- Tliquid
- Liquid line temperature leaving the condenser, °F
- Tsat
- Saturation temperature at the gauge pressure, °F
Gauge pressure (psig) is pressure above atmospheric. Below 0 psig, the chart shows vacuum in inches of mercury.
Worked Example: R-404A Superheat and Subcooling
Walk-in cooler (medium temp): an R-404A system reads 54.5 psig suction with a 30°F suction line, and 270.0 psig on the liquid line with a 100°F liquid line.
- Saturation temperature at 54.5 psig: 20.0°F.
- Superheat: 30°F − 20.0°F = 10.0°F.
- Saturation temperature at 270.0 psig: 110.0°F.
- Subcooling: 110.0°F − 100°F = 10.0°F.
Is R-404A Being Phased Out?
With a GWP of 3,922, R-404A is a main target of the HFC phasedown. EPA’s Technology Transitions rule sets lower GWP limits for most types of new commercial refrigeration, so new equipment uses R-448A, R-449A, R-290 or CO2 instead.
R-404A stays available for service, and many existing systems are retrofitted to R-448A or R-449A, which work with the same POE oil.
R-404A Field Tips
Practical points for working on R-404A systems, from the sources below.
Sources: Honeywell: Solstice N40 (R-448A), ACHR News: Charging refrigeration systems with blended refrigerants, Arkema: Forane retrofit guidelines