Refrigeration measurements
Refrigerant Subcooling Calculator
Calculate the temperature difference between a matched condensing saturation temperature and a measured liquid-line temperature.
Subcooling inputs
Use a saturation temperature derived for the same refrigerant, pressure point, and liquid-line location.
How to use this calculator
- Identify the refrigerant and obtain a saturation temperature from the corresponding high-side pressure using a reliable source.
- Measure the liquid-line temperature at the same documented point used for the check.
- Enter the matched temperatures in the same unit system and review the difference.
Formula
A temperature difference has the same numeric size in degrees Celsius and kelvin; a Fahrenheit difference converts to kelvin by multiplying by 5/9.
Variables and measurement boundaries
| Input | Use | Important limit |
|---|---|---|
| Condensing saturation temperature | Temperature corresponding to the matched refrigerant pressure | Requires correct refrigerant property data |
| Liquid-line temperature | Actual liquid-pipe measurement | Location must be stated |
| Subcooling | Temperature difference below saturation | Does not by itself prescribe a charge |
Example
If the matched condensing saturation temperature is 100°F and the liquid line is 90°F, subcooling is 10°F, or 5.56 K. Both readings must correspond to the same refrigerant and operating condition.
Result interpretation
Subcooling is a measured state difference. A negative result means the values or measurement locations should be checked. Equipment design, receiver arrangement, liquid-line pressure drop, refrigerant, and manufacturer service procedure determine how a qualified technician interprets the reading.
Do not use a generic target
This calculator intentionally supplies no target subcooling value. Manufacturer instructions, system configuration, and the documented measurement location control the applicable procedure.
Frequently asked questions
Can I use any pressure-temperature chart?
No. Use a reliable chart or property source for the exact refrigerant and the appropriate dew/bubble convention where applicable.
Where should liquid-line temperature be measured?
Use the location specified by the relevant service method, such as condenser outlet or expansion-valve inlet, and keep it consistent with the pressure basis.
Does this result tell me how to charge the system?
No. Follow the equipment manufacturer’s service procedure and qualified refrigeration practice.