⚡ AnythingOnline
❄️
Subcooling & Superheat Diagnostic Calculator mechanical
100% Free • No Sign-Up

Subcooling & Superheat Diagnostic Calculator

Calculate condenser subcooling and evaporator superheat to diagnose refrigerant charge levels, expansion valve (TXV/EEV) performance, and non-condensable gases.

Refrigerant & Metering Type

High-Side & Low-Side Field Measurements

Thermodynamic Diagnostics

System Diagnostic Status
-- Condition
-- action
Condenser Subcooling
-- °F
-- °F Cond Sat
Evaporator Superheat
-- °F
-- °F Evap Sat
Target Subcooling Range: 10°F to 14°F (TXV standard)
Target Superheat Range: 8°F to 14°F (TXV standard)
Liquid Slugging Risk: --
Subcooling measures the solid liquid column seal entering the expansion valve; superheat ensures complete evaporation before vapor enters the compressor.

Recommended Tools & Equipment

Tested hardware and components for high reliability

100% Free Tool Zero Sign-Up

Frequently Asked Questions

What is subcooling and why is it used to charge TXV systems?

Subcooling is the temperature drop of liquid refrigerant below its saturated condensing temperature: Subcooling = Saturated Condenser Temp - Liquid Line Temp. Systems with Thermostatic Expansion Valves (TXVs) must be charged by subcooling because the TXV continuously modulates refrigerant flow to maintain constant superheat.

What is superheat and why is it critical for compressor reliability?

Superheat is the sensible temperature rise of refrigerant vapor above its saturated boiling temperature: Superheat = Suction Line Temp - Saturated Evaporator Temp. Having positive superheat (typically 8°F to 14°F) guarantees that 100% of liquid refrigerant has boiled into gas before entering the compressor crankcase, preventing mechanical liquid slugging.

How do you distinguish between an undercharged system and a restricted TXV?

Both conditions exhibit high superheat and low suction pressure. However, an undercharged system has LOW subcooling (less than 5°F) because there is insufficient liquid in the condenser. A restricted TXV or plugged filter drier has HIGH subcooling (above 15°F) because refrigerant backs up inside the condenser coil.