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AG 31-011 • REFRIGERANT PIPING DESIGN
How to Size Liquid Lines (continued)
Step 7- Determine The Sub-cooling Required for Saturated
Liquid at the TX Valve
The sub-cooling require to have saturated liquid at the TX
valve can be found by:
Subcooling = Actual Saturation Temperature – Saturation
Temperature
TX Valve
Subcooling = 120.0°F – 117.8°F = 2.2°F
Step 8- Determine the Required Sub-cooling for Proper
Operation
2.2°F is the amount of sub-cooling required to have saturated
liquid refrigerant at the TX valve. Anything less, and the
refrigerant will start to flash and the TX valve will not operate
properly. For TX valves to operate properly and avoid
diaphragm fluttering, there should be an additional 4°F of sub-
cooling at the TX Valve.
Subcooling Requirement = TX Valve Temperature + Minimum
System Temperature
Subcooling Requirement = 2.2°F + 4.0°F = 6.2°F