Refrigerant Pressure Temperature Chart UK: Quick Reference for HVAC Engineers
Saturation pressure-temperature (PT) data is one of the most frequently referenced resources for UK HVAC and refrigeration engineers. This guide provides quick-reference PT values for the most common UK refrigerants: R32, R410A, R404A, R134a, R407C, R1234yf and R22 (for legacy systems).
How to Use Pressure-Temperature Data
The saturation temperature is the temperature at which a refrigerant changes phase (evaporates or condenses) at a given pressure. On a refrigeration system: the low-side pressure gives the evaporating temperature; the high-side pressure gives the condensing temperature. Compare actual measured temperatures with PT values to diagnose charge issues, blocked expansion valves or heat exchanger fouling.
Key PT Values for Common UK Refrigerants
All pressures in bar gauge (barg). Use a certified digital manifold set to the correct refrigerant.
R32 (GWP 675, A2L):
- -20°C: 3.8 barg | -10°C: 5.8 barg | 0°C: 8.0 barg | 20°C: 14.8 barg | 40°C: 24.8 barg | 50°C: 31.0 barg
R410A (GWP 2,088, A1):
- -20°C: 3.7 barg | -10°C: 5.7 barg | 0°C: 7.9 barg | 20°C: 14.5 barg | 40°C: 24.3 barg | 50°C: 30.4 barg
R404A (GWP 3,922, A1):
- -30°C: 2.5 barg | -20°C: 4.4 barg | -10°C: 6.8 barg | 0°C: 9.7 barg | 20°C: 17.4 barg | 40°C: 28.5 barg
R134a (GWP 1,430, A1):
- -20°C: 0.33 barg | -10°C: 1.0 barg | 0°C: 2.0 barg | 20°C: 4.9 barg | 40°C: 9.6 barg | 50°C: 12.5 barg
R407C (GWP 1,774, A1) — approximate mid-point values:
- -20°C: 2.5 barg | -10°C: 4.0 barg | 0°C: 5.8 barg | 20°C: 11.3 barg | 40°C: 19.5 barg
R1234yf (GWP 4, A2L):
- -20°C: 0.8 barg | -10°C: 1.7 barg | 0°C: 3.0 barg | 20°C: 6.5 barg | 40°C: 12.1 barg
Important Notes for UK Engineers
- R407C is a zeotropic blend — it has a temperature glide of ~7°C. Use bubble point for liquid-side, dew point for vapour-side calculations.
- R404A and R407A have similar glide properties. Always use dew-point pressures for suction side on blends.
- Always zero-check and calibrate your manifold gauges before use. Inaccurate gauges lead to incorrect charge diagnosis.
- Digital manifolds with built-in PT charts (e.g. Testo 550s, Fieldpiece MG44) are recommended for accuracy and speed.
Carrying out a system service or charge verification? Source your refrigerant from Refrigerant Gas Supplies Ltd — UK F-Gas compliant, next-day delivery: R32, R410A, R404A, R134a.
Frequently Asked Questions
What is the saturation pressure of R32 at 0°C?
Approximately 8.0 bar gauge. At -10°C: 5.8 barg. At 40°C: 24.8 barg. Use a digital manifold set to R32 for accurate readings.
What is the saturation pressure of R410A at 0°C?
Approximately 7.9 bar gauge — very similar to R32. At -10°C: 5.7 barg. At 40°C: 24.3 barg.
Why do R404A systems run at higher pressures than R22?
R404A at 0°C is approximately 9.7 barg vs R22’s 4.0 barg. R22 systems cannot be converted to R404A without checking pressure ratings of all components.