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:
R-507A refrigerant properties
Pressure–temperature relationship
How to read and use the PT chart
Superheat and subcooling calculations
Charging methods
Troubleshooting using real HVAC scenarios
What is R-507A Refrigerant?
R-507A is a near-azeotropic blend of:
R-125 (50%)
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
Type: HFC blend
ODP (Ozone Depletion Potential): 0
GWP: ~3985
Glide: ~0°C (near azeotropic)
Boiling Point: -46.7°C
Oil Type: POE (Polyolester)
What is a Pressure Temperature Chart?
A Pressure Temperature (PT) chart shows the relationship between:
Pressure (PSI / Bar)
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
Measure system pressure using manifold gauge
Locate pressure on PT chart
Read corresponding temperature
Compare with actual pipe temperature
Example
Suction pressure: 60 PSI
👉 Corresponding temp ≈ -5°C
This indicates the evaporator saturation temperature.
Where is R-507A Used?
1. Commercial Refrigeration
Supermarkets
Display freezers
2. Cold Storage
Food storage
Ice plants
3. Industrial Refrigeration
Process cooling
Blast freezers
Importance of PT Chart in HVAC
Ensures correct refrigerant charge
Helps diagnose faults quickly
Prevents compressor failure
Improves system efficiency
R-507A Charging Methods
1. Charging by Weight
Most accurate method
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
Prevents liquid floodback
Indicates evaporator performance
👉 Normal Range: 6°C to 12°C
Subcooling
Ensures full liquid refrigerant
Improves system efficiency
👉 Normal Range: 4°C to 8°C
Normal Pressure Range of R-507A
Low Side (Suction)
20 – 60 PSI
High Side (Discharge)
150 – 300+ PSI
Common HVAC Problems Using PT Chart
1. Low Pressure
Causes:
Refrigerant leak
Blocked filter
Low charge
2. High Pressure
Causes:
Overcharging
Dirty condenser
Poor airflow
3. High Superheat
Causes:
Undercharge
Expansion valve issue
Real HVAC Troubleshooting Example
Scenario:
Low suction pressure
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
Zero ozone depletion
No temperature glide
Stable performance
Ideal for low-temp systems
Disadvantages of R-507A
High GWP
Being phased down globally
Requires POE oil
Safety Precautions
Always wear PPE
Avoid refrigerant leaks
Use proper charging equipment
Never mix refrigerants
Best Practices for Technicians
Always use PT chart during servicing
Check superheat & subcooling
Maintain proper airflow
Use digital gauges for accuracy
Future of R-507A
Due to environmental regulations, R-507A is gradually being replaced by:
R-448A
R-449A
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:
Diagnose issues accurately
Charge refrigerant correctly
Improve system efficiency
Prevent costly breakdowns
Mastering the R-507A PT chart will make you a more skilled and reliable HVAC technician.
Get a Future-Ready HVAC Work Today
Planning a large commercial or institutional project? Get in touch with Vipul HVAC House, Gujarat’s trusted HVAC Site Works (SITC) contractor.
Call: +91 9825636606
Email: info@vipulhvacsolution.in
Visit: www.vipulac.in
Vipul AC – Gujarat’s Expert in Airport HVAC Work.
One Response