Subcool Calculator
Calculate subcool for air conditioning systems to verify proper refrigerant charge and optimize system performance.
For Licensed & Trained HVAC Technicians Only
This checklist is intended exclusively for use by licensed, certified, and trained HVAC professionals. It is not a DIY guide and should not be used by untrained individuals to perform repairs or diagnostics. The purpose of this checklist is to help qualified technicians maintain a consistent, step-by-step workflow so that no critical step is overlooked or skipped during service.
Subcool Calculator
Read from the high-side gauge on your manifold
Measure at the liquid line near the service valve or condenser outlet
What is Subcool?
Subcool is the difference between the saturation temperature of refrigerant and the actual temperature of the liquid refrigerant. It indicates how much the liquid has been cooled below its condensing temperature, which is essential for proper system charging and efficient operation.
How to Measure Subcool
- Connect your manifold gauges to the service ports
- Read the liquid line pressure from the high-side gauge (PSIG)
- Attach a temperature probe to the liquid line near the service valve or condenser outlet
- Record the liquid line temperature
- Use this calculator to determine subcool and charging status
Subcool Guidelines
Subcool vs Superheat
Subcool is measured on the high-pressure side (liquid line) and indicates proper refrigerant charge.
Superheat is measured on the low-pressure side (suction line) and protects the compressor from liquid refrigerant.
Both measurements are essential for proper system diagnosis and charging.
Refrigerant Types
R-410A
Common refrigerant in modern mini-split and residential AC systems. Being phased out due to environmental concerns.
R-32
Newer, more environmentally friendly refrigerant with lower global warming potential. Increasingly common in mini-splits.
R-454B
Next-generation refrigerant designed to replace R-410A with significantly lower environmental impact.
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