R-744 (CO2) Pressure at -20°F — Saturation P-T Data
How This Was Calculated
Saturation pressure interpolated from ASHRAE tabular data for R744. Normal operating pressure range.
- P_sat
- Saturation pressure: 214 PSI
- T_input
- Input temperature: -20°F
- T_data
- ASHRAE tabular reference data: R744
Important Considerations
-20°F is a very low operating temperature. At these suction conditions, R744 refrigeration systems face reduced compressor efficiency due to low suction pressure and high compression ratios. Crankcase heaters are critical to prevent refrigerant migration into oil. Head pressure control (fan cycling or fan speed control) is needed to maintain minimum condensing pressure. For heat pump operation, defrost cycles become more frequent below 20°F.
The saturation pressure shown (for R744 at -20°F) is the baseline for measuring superheat and subcooling. Suction superheat = suction line temperature minus evaporator saturation temperature. Subcooling = condensing saturation temperature minus liquid line temperature. Typical targets: 8–12°F superheat at the evaporator (TXV systems), 10–20°F subcooling at the condenser. Deviations indicate improper charge, metering device issues, or non-condensables.
R-744 (CO2) is classified A1 (non-toxic, non-flammable) but operates at extremely high pressures (up to 1,500+ PSI). Specialized high-pressure rated equipment, piping, and safety valves are mandatory. CO2 can displace oxygen in enclosed spaces — ventilation and detection systems required.
R744 has a GWP of 1 — meaning 1 lb released equals 1 lbs of CO2 equivalent warming over 100 years. This is a low-GWP refrigerant and is considered environmentally preferable under current and projected regulations. It aligns with AIM Act long-term goals and is unlikely to face near-term restrictions. Choosing low-GWP equipment protects against future regulatory compliance costs.
Saturation pressure-temperature data for R744 derived from ASHRAE Fundamentals Handbook, Chapter 30 (Thermophysical Properties of Refrigerants), and verified against manufacturer published data (Chemours Opteon, Honeywell Solstice). Values represent saturated conditions at sea level.