R-507A Pressure Temperature Chart
Complete Guide to R-507A Pressure Temperature Chart (PT Chart)
Pressure, Temperature, Applications, Charging Methods & HVAC Troubleshooting Guide
R-507A is a widely used HFC refrigerant blend in commercial refrigeration systems, especially in low- and medium-temperature applications. If you are an HVAC technician, contractor, or refrigeration engineer, understanding the R-507A pressure temperature chart (PT chart) is critical for accurate system diagnosis, proper refrigerant charging, and maintaining efficiency.
This comprehensive guide will cover everything you need to know about:
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R-507A refrigerant properties
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Pressure–temperature relationship
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How to read and use the PT chart
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Superheat and subcooling calculations
-
Charging methods
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Troubleshooting using real HVAC scenarios
What is R-507A Refrigerant?
R-507A is a near-azeotropic blend of:
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R-125 (50%)
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R-143a (50%)
It was developed as a replacement for R-502, which was phased out due to ozone depletion.
Key Properties of R-507A
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Type: HFC blend
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ODP (Ozone Depletion Potential): 0
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GWP: ~3985
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Glide: ~0°C (near azeotropic)
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Boiling Point: -46.7°C
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Oil Type: POE (Polyolester)
What is a Pressure Temperature Chart?
A Pressure Temperature (PT) chart shows the relationship between:
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Pressure (PSI / Bar)
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Temperature (°C / °F)
It represents the saturation point where refrigerant exists in both liquid and vapor state.
R-507A Pressure Temperature Chart (°C vs PSI)
Here are commonly used values:
| Temperature (°C) | Pressure (PSI) |
|---|---|
| -40°C | 9.5 PSI |
| -35°C | 13.2 PSI |
| -30°C | 17.8 PSI |
| -25°C | 23.4 PSI |
| -20°C | 30.3 PSI |
| -15°C | 38.6 PSI |
| -10°C | 48.6 PSI |
| -5°C | 60.5 PSI |
| 0°C | 74.5 PSI |
| 5°C | 90.9 PSI |
| 10°C | 109.8 PSI |
| 15°C | 131.5 PSI |
| 20°C | 156.3 PSI |
| 25°C | 184.4 PSI |
| 30°C | 216.1 PSI |
| 35°C | 251.6 PSI |
| 40°C | 291.0 PSI |
| 45°C | 334.5 PSI |
| 50°C | 382.3 PSI |
R-507A Pressure Temperature Chart (°F vs PSI)
| Temperature (°F) | Pressure (PSI) |
|---|---|
| -40°F | 8.6 PSI |
| -30°F | 13.8 PSI |
| -20°F | 21.5 PSI |
| -10°F | 32.2 PSI |
| 0°F | 46.8 PSI |
| 10°F | 66.3 PSI |
| 20°F | 91.7 PSI |
| 30°F | 123.8 PSI |
| 40°F | 163.6 PSI |
| 50°F | 212.4 PSI |
| 60°F | 271.6 PSI |
| 70°F | 342.5 PSI |
| 80°F | 426.6 PSI |
| 90°F | 525.5 PSI |
| 100°F | 640.9 PSI |
How to Read the R-507A PT Chart
Step-by-Step Guide
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Measure system pressure using manifold gauge
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Locate pressure on PT chart
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Read corresponding temperature
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Compare with actual pipe temperature
Example
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Suction pressure: 60 PSI
👉 Corresponding temp ≈ -5°C
This indicates the evaporator saturation temperature.
Where is R-507A Used?
1. Commercial Refrigeration
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Supermarkets
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Display freezers
2. Cold Storage
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Food storage
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Ice plants
3. Industrial Refrigeration
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Process cooling
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Blast freezers
Importance of PT Chart in HVAC
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Ensures correct refrigerant charge
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Helps diagnose faults quickly
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Prevents compressor failure
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Improves system efficiency
R-507A Charging Methods
1. Charging by Weight
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Most accurate method
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Follow manufacturer specifications
2. Superheat Method
Used for capillary systems
Formula:
Superheat = Actual Temp – Saturation Temp
3. Subcooling Method
Used for TXV systems
Formula:
Subcooling = Saturation Temp – Liquid Temp
Superheat and Subcooling Explained
Superheat
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Prevents liquid floodback
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Indicates evaporator performance
👉 Normal Range: 6°C to 12°C
Subcooling
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Ensures full liquid refrigerant
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Improves system efficiency
👉 Normal Range: 4°C to 8°C
Normal Pressure Range of R-507A
Low Side (Suction)
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20 – 60 PSI
High Side (Discharge)
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150 – 300+ PSI
Common HVAC Problems Using PT Chart
1. Low Pressure
Causes:
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Refrigerant leak
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Blocked filter
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Low charge
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 issue
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 reference
R-507A vs Other Refrigerants
| Refrigerant | Type | Usage | Pressure |
|---|---|---|---|
| R-507A | HFC | Commercial refrigeration | High |
| R-404A | HFC | Similar applications | Slightly lower |
| R-134a | HFC | Domestic & automotive | Medium |
Advantages of R-507A
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Zero ozone depletion
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No temperature glide
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Stable performance
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Ideal for low-temp systems
Disadvantages of R-507A
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High GWP
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Being phased down globally
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Requires POE oil
Safety Precautions
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Always wear PPE
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Avoid refrigerant leaks
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Use proper charging equipment
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Never mix refrigerants
Best Practices for Technicians
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Always use PT chart during servicing
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Check superheat & subcooling
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Maintain proper airflow
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Use digital gauges for accuracy
Future of R-507A
Due to environmental regulations, R-507A is gradually being replaced by:
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R-448A
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R-449A
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CO₂ (R-744) systems
Frequently Asked Questions (FAQ)
1. What is R-507A used for?
Commercial refrigeration and low-temperature systems
2. What is normal pressure for R-507A?
Low side: 20–60 PSI, High side: 150–300+ PSI
3. Is R-507A same as R-404A?
Similar but slightly different performance
4. Can R-507A replace R-404A?
Yes, in many systems with proper adjustments
5. Is R-507A being phased out?
Yes, due to high GWP
Conclusion
The R-507A Pressure Temperature Chart is an essential tool for HVAC professionals working in refrigeration systems. By understanding and properly using the PT chart, technicians can:
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Diagnose issues accurately
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Charge refrigerant correctly
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Improve system efficiency
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Prevent costly breakdowns
Mastering the R-507A PT chart will make you a more skilled and reliable HVAC technician.
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