What is normal subcooling?

Most TXV systems target 8–12 °F of subcooling at the condenser outlet; always follow the data plate when it specifies a value.

What does low subcooling indicate?

Low or zero subcooling generally means undercharge or a liquid line restriction; the condenser is not fully filling with liquid.

What does high subcooling indicate?

High subcooling usually means overcharge, a restricted metering device, non-condensables, or a dirty or airflow-restricted condenser.

Subcool Calculator — TXV Charging

All calculators

Formula

Subcool = Bubble-point Temp (from P/T) − Measured Liquid Line Temp

Pick the refrigerant; the bubble point (liquid side) is looked up from its PT chart. Target subcool is on the equipment data plate (typ. 8–12°F).

Pressure basis

Rounding

Refrigerant

Liquid line pressure

psig

Measured liquid line temp

°F

Target subcool (nameplate)

°F

Saturation temp

83.6°F

R-410A @ 250.0 psig (250.0 psig)

Actual subcool

-11.4°F

Target 10.0°F · -21.4°F vs. target

Undercharged — low subcool means refrigerant flashing in liquid line. Find leak before adding. Negative subcool = no liquid at metering device. Check charge immediately.

How to use this calculator

Determine liquid line subcooling from head pressure and liquid line temperature.

Select the refrigerant and enter liquid line pressure with the correct psig/psia basis.
Enter the liquid line temperature at the condenser outlet.
Read subcooling as saturation (bubble point) temperature minus liquid temperature.
Compare against the manufacturer's target, typically 8–12 °F.

Frequently asked questions

What is normal subcooling?: Most TXV systems target 8–12 °F of subcooling at the condenser outlet; always follow the data plate when it specifies a value.
What does low subcooling indicate?: Low or zero subcooling generally means undercharge or a liquid line restriction; the condenser is not fully filling with liquid.
What does high subcooling indicate?: High subcooling usually means overcharge, a restricted metering device, non-condensables, or a dirty or airflow-restricted condenser.