R-448A PT Chart
Saturation pressure for R-448A from -40°F to 150°F, with liquid (bubble) and vapor (dew) columns. Look up a pressure or temperature, switch to metric, and check typical operating pressures.
By BrazeJobs Team · Updated
R-448A Lookup
Liquid (Bubble)
89.0 psig
Vapor (Dew)
72.1 psig
Bubble Point
29.8°F
Dew Point
39.9°F
Chart range: -40°F to 150°F. Enter vacuum as a negative pressure. Check R-448A superheat and subcooling
R-448A PT Chart
| Temp | Liquid (Bubble) | Vapor (Dew) |
|---|---|---|
| -40°F | 4.9 psig | 0.0 psig |
| -35°F | 7.5 psig | 2.1 psig |
| -30°F | 10.4 psig | 4.4 psig |
| -25°F | 13.5 psig | 7.0 psig |
| -20°F | 17.0 psig | 9.8 psig |
| -15°F | 20.8 psig | 13.0 psig |
| -10°F | 24.9 psig | 16.4 psig |
| -5°F | 29.3 psig | 20.2 psig |
| 0°F | 34.2 psig | 24.3 psig |
| 5°F | 39.4 psig | 28.8 psig |
| 10°F | 45.1 psig | 33.6 psig |
| 15°F | 51.2 psig | 38.9 psig |
| 20°F | 57.8 psig | 44.6 psig |
| 25°F | 64.8 psig | 50.7 psig |
| 30°F | 72.3 psig | 57.3 psig |
| 35°F | 80.4 psig | 64.4 psig |
| 40°F | 89.0 psig | 72.1 psig |
| 45°F | 98.2 psig | 80.3 psig |
| 50°F | 108.0 psig | 89.0 psig |
| 55°F | 118.0 psig | 98.4 psig |
| 60°F | 129.0 psig | 108.0 psig |
| 65°F | 141.0 psig | 119.0 psig |
| 70°F | 154.0 psig | 130.0 psig |
| 75°F | 167.0 psig | 142.0 psig |
| 80°F | 181.0 psig | 155.0 psig |
| 85°F | 195.0 psig | 169.0 psig |
| 90°F | 211.0 psig | 183.0 psig |
| 95°F | 227.0 psig | 198.0 psig |
| 100°F | 244.0 psig | 214.0 psig |
| 105°F | 262.0 psig | 231.0 psig |
| 110°F | 281.0 psig | 249.0 psig |
| 115°F | 300.0 psig | 268.0 psig |
| 120°F | 321.0 psig | 288.0 psig |
| 125°F | 343.0 psig | 309.0 psig |
| 130°F | 365.0 psig | 331.0 psig |
| 135°F | 389.0 psig | 355.0 psig |
| 140°F | 414.0 psig | 379.0 psig |
| 145°F | 440.0 psig | 405.0 psig |
| 150°F | 467.0 psig | 433.0 psig |
About R-448A
R-448A is a non-flammable HFC/HFO blend for low- and medium-temperature commercial refrigeration. It replaces R-404A in new supermarket systems and retrofits, at about a third of R-404A’s GWP.
It is a zeotropic blend with significant glide, so the chart gives liquid (bubble) and vapor (dew) columns. Superheat uses the dew column, subcooling the bubble column.
- Supermarket rack systems and display cases
- Walk-in coolers and freezers, new and retrofit
- Retrofit of R-404A and R-22 refrigeration
R-448A Properties
Key facts for identifying R-448A and choosing tools, oil and replacements.
| Property | Value |
|---|---|
| Type | HFC/HFO blend |
| Composition | R-32 26%, R-125 26%, R-134a 21%, R-1234yf 20%, R-1234ze(E) 7% by weight |
| ASHRAE safety class | A1 |
| GWP (IPCC AR4) | 1,387 |
| Boiling point at 1 atm | -50.7°F |
| Critical temperature | 182.6°F |
| Oil | POE (polyolester) |
| Trade names | Solstice N40 |
| Replaces | R-404A, R-22 |
| Replaced by | None |
Typical R-448A 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 | 44.6 psig | 110°F | 281.0 psig |
| Walk-in freezer (low temp) | -20°F | 9.8 psig | 110°F | 281.0 psig |
How to Read the R-448A 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.
R-448A is a zeotropic blend, so it boils over a range of temperatures instead of at one point. That range is the glide. The liquid (bubble) column gives the pressure where the first bubble forms; the vapor (dew) column gives the pressure where the last drop of liquid boils off.
At 20°F, the bubble pressure is 57.8 psig and the dew pressure is 44.6 psig. Read the other way, at 44.6 psig the glide is about 10.4°F.
Use the vapor (dew) column for superheat on the suction line and the liquid (bubble) column for subcooling on the liquid line. Mixing them up shifts the answer by the glide.
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
- Tdew
- Dew point at suction pressure (vapor column), °F
- Tbubble
- Bubble point at liquid pressure (liquid column), °F
Gauge pressure (psig) is pressure above atmospheric. Below 0 psig, the chart shows vacuum in inches of mercury.
Worked Example: R-448A Superheat and Subcooling
Walk-in cooler (medium temp): an R-448A system reads 44.6 psig suction with a 30°F suction line, and 281.0 psig on the liquid line with a 100°F liquid line.
- Dew point at 44.6 psig: 20.0°F.
- Superheat: 30°F − 20.0°F = 10.0°F.
- Bubble point at 281.0 psig: 110.0°F.
- Subcooling: 110.0°F − 100°F = 10.0°F.
Is R-448A Being Phased Out?
R-448A is a main retrofit and new-system replacement for R-404A. For some new commercial refrigeration categories, EPA’s Technology Transitions rule sets GWP limits below R-448A’s, so check the rule for the system type before specifying it.
It uses the same POE oil as R-404A, which keeps retrofits simpler, but its glide means expansion valves and controls need resetting.
R-448A Field Tips
Practical points for working on R-448A systems, from the sources below.
Sources: Honeywell: Solstice N40 (R-448A), ACHR News: Charging refrigeration systems with blended refrigerants, HVAC School: Glide, blends and why you can’t mix refrigerants