R-422A Pressure Temperature Chart
Complete Guide to R-422A Pressure Temperature Chart (PT Chart)
HVAC Pressure, Temperature, Charging, Troubleshooting & Refrigeration Applications
R-422A is a widely used retrofit refrigerant designed as a replacement for R-22 in air conditioning and refrigeration systems. For HVAC technicians, understanding the R-422A Pressure Temperature Chart (PT Chart) is essential for accurate charging, troubleshooting, and maintaining system efficiency.
This ultra-detailed guide will help you master:
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R-422A refrigerant properties
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PT chart values (°C & PSI, °F & PSI)
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How to read and use PT charts
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Superheat and subcooling calculations
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Charging methods
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Real HVAC troubleshooting examples
What is R-422A Refrigerant?
R-422A is an HFC blend refrigerant used as a drop-in replacement for R-22 in many systems.
Composition
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R-125
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R-600a (small amount)
Key Properties of R-422A
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Type: HFC blend
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ODP: 0
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GWP: ~3143
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Glide: ~2–3°C
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Oil Compatibility: Mineral oil / POE
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Application: Retrofit for R-22 systems
What is a Pressure Temperature Chart?
A PT chart shows the relationship between:
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Pressure (PSI / Bar)
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Temperature (°C / °F)
It represents saturation conditions, where refrigerant changes phase between liquid and vapor.
R-422A Pressure Temperature Chart (°C vs PSI)
| Temperature (°C) | Pressure (PSI) |
|---|---|
| -20°C | 18.5 PSI |
| -15°C | 24.5 PSI |
| -10°C | 31.8 PSI |
| -5°C | 40.5 PSI |
| 0°C | 50.8 PSI |
| 5°C | 63.0 PSI |
| 10°C | 77.2 PSI |
| 15°C | 93.5 PSI |
| 20°C | 112.1 PSI |
| 25°C | 133.1 PSI |
| 30°C | 156.7 PSI |
| 35°C | 183.0 PSI |
| 40°C | 212.1 PSI |
| 45°C | 244.2 PSI |
| 50°C | 279.5 PSI |
R-422A Pressure Temperature Chart (°F vs PSI)
| Temperature (°F) | Pressure (PSI) |
|---|---|
| -5°F | 21.0 PSI |
| 0°F | 26.5 PSI |
| 5°F | 32.5 PSI |
| 10°F | 39.2 PSI |
| 15°F | 46.6 PSI |
| 20°F | 54.7 PSI |
| 25°F | 63.7 PSI |
| 30°F | 73.6 PSI |
| 40°F | 96.2 PSI |
| 50°F | 123.3 PSI |
| 60°F | 155.5 PSI |
| 70°F | 193.4 PSI |
| 80°F | 237.5 PSI |
| 90°F | 288.4 PSI |
| 100°F | 346.7 PSI |
How to Read R-422A PT Chart
Step-by-Step Method
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Measure pressure using manifold gauge
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Find pressure value in PT chart
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Read corresponding saturation temperature
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Compare with actual pipe temperature
Example
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Suction pressure = 50 PSI
👉 Saturation temperature ≈ 0°C
Understanding Temperature Glide in R-422A
Unlike pure refrigerants, R-422A has temperature glide (2–3°C).
What This Means
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Evaporator and condenser temperatures are not constant
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Use:
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Dew point (vapor) for superheat
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Bubble point (liquid) for subcooling
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Applications of R-422A
1. R-22 Retrofit Systems
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Split AC
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Package units
2. Commercial Refrigeration
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Cold rooms
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Display units
3. Industrial Cooling
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Process cooling
Importance of PT Chart in HVAC
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Accurate refrigerant charging
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Quick fault detection
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Efficiency improvement
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Compressor safety
R-422A Charging Methods
1. Charging by Weight
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Best and most accurate method
2. Superheat Method (Capillary System)
Superheat = Actual Temp – Saturation Temp
👉 Ideal: 8–12°C
3. Subcooling Method (TXV System)
Subcooling = Saturation Temp – Liquid Temp
👉 Ideal: 5–10°C
Superheat and Subcooling Explained
Superheat
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Prevents liquid refrigerant entering compressor
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Indicates evaporator performance
Subcooling
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Ensures full liquid refrigerant
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Improves efficiency
Normal Pressure Range for R-422A
Low Side
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40 – 70 PSI
High Side
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150 – 300 PSI
Common HVAC Problems Using PT Chart
1. Low Pressure
Causes:
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Refrigerant leakage
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Low charge
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Blocked filter
2. High Pressure
Causes:
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Overcharging
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Dirty condenser
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Poor airflow
3. High Superheat
Causes:
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Undercharge
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Expansion valve fault
Real HVAC Troubleshooting Example
Scenario:
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Low suction pressure
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High superheat
👉 Diagnosis: Undercharged system
👉 Solution: Add refrigerant using PT chart
R-422A vs Other Refrigerants
| Refrigerant | Type | Use | Pressure |
|---|---|---|---|
| R-422A | HFC Blend | R-22 retrofit | Medium |
| R-22 | HCFC | Old systems | Medium |
| R-410A | HFC | Modern AC | High |
Advantages of R-422A
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No ozone depletion
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Easy retrofit for R-22
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Compatible with existing oil
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Widely available
Disadvantages of R-422A
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Temperature glide
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High GWP
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Slight efficiency drop vs R-22
Safety Precautions
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Wear safety gloves
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Use proper gauges
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Avoid mixing refrigerants
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Follow manufacturer guidelines
Best Practices for HVAC Technicians
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Always use PT chart
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Check superheat & subcooling
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Maintain airflow
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Avoid guess charging
Future of R-422A
Due to environmental regulations, R-422A is being replaced by:
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R-32
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R-454B
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R-290
Frequently Asked Questions (FAQ)
1. What is R-422A used for?
R-22 retrofit systems
2. What is normal pressure for R-422A?
Low side: 40–70 PSI
3. Does R-422A have glide?
Yes, about 2–3°C
4. Can R-422A replace R-22?
Yes, commonly used retrofit
5. Is R-422A still used?
Yes, but gradually being phased down
Conclusion
The R-422A Pressure Temperature Chart is a crucial tool for HVAC professionals. By mastering it, you can:
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Diagnose systems accurately
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Charge refrigerant properly
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Improve efficiency
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Prevent costly failures
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