Diagrams.ink / HVAC training simulation
Superheat and subcooling: what four readings can and can’t tell you
A simplified split cooling system with a fixed-orifice metering device. Pick a condition, read the gauges and line clamps, then watch the two calculated numbers appear from what the refrigerant is doing inside the coils.
Simplified split air conditioner · fixed orifice · cutaway, not to scale · illustrative R-410A-type saturation tableNormal charge · reference example
1Pick a condition to simulate
▾Tap a condition. Tap the lettered tags A–D on the machine to see each reading.
Hot vaporCondensing (vapor + liquid)Subcooled liquidBoiling in evaporatorSuperheated vapor
1Compressor
2Condenser coil + fan
3Liquid line (small, warm)
4Fixed orifice (piston)
5Evaporator coil
6Suction line (large, cool)
7Filter + blower
A–DMeasurement points
2Inspect the four readings
ASuction line
Clamp on the suction line near the compressorBEvaporating sat.
CLiquid line
Clamp on the liquid line near the condenserDCondensing sat.
3Calculate
Superheat = suction line − evaporating saturation
Subcooling = condensing saturation − liquid line
Saturation temperature is the boiling/condensing point for the gauge pressure. Every number here uses one unit system, and differences are in temperature-difference units.
Units
Warmer outdoor air raises condensing temperature and shifts what “normal” looks like.
Training model with example numbers, not field data or a charging chart.
Why these readings alone are not a diagnosis
- Targets move. A fixed-orifice system’s expected superheat changes with indoor and outdoor conditions; the equipment maker’s data sets the target, not a single number.
- Different faults overlap. Low superheat can come from overcharge or from poor airflow; high superheat from a low charge or from a restriction. Subcooling and airflow help separate them, and still don’t settle it.
- Measurements can mislead. Sensor contact, insulation, gauge accuracy, running time and where the lines are read all change the answer.
How the model works
Each condition is a set of example saturation and line temperatures. Superheat and subcooling are computed from the four readings exactly as shown above. Evaporator and condenser colours show how much of each coil carries superheated vapor or subcooled liquid. Airflow, flow speed, filter and gauges follow the same state.
SH = A − B SC = D − C
Training only. This simulation does not tell anyone to add, remove or release refrigerant. Working on a refrigerant circuit needs proper certification, equipment and the manufacturer’s instructions. Use readings like these as clues, together with airflow, electrical and other checks.