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Superheat And Subcooling Calculator

Work out superheat and subcooling instantly with clear inputs, formula shown and shareable results.

About Superheat And Subcooling Calculator

Superheat is how far the suction vapour has been heated above its saturation temperature, and subcooling is how far the liquid has been cooled below it. Together they show whether the charge and metering device are matching the evaporator load: superheat reads the evaporator side, subcooling reads the condenser side.

Formulas

Superheat

Superheat = suction line temp - evaporator saturation temp

Subcooling

Subcooling = condenser saturation temp - liquid line temp

Worked example

With the default values below, Superheat And Subcooling Calculator returns Suction superheat of 15.0. Change any input above and every figure here is recalculated in your browser.

Inputs used

Suction line temperatureminimum -40 °F
55 °F
Evaporator saturation temperatureminimum -40 °F
40 °F
Liquid line temperatureminimum -40 °F
85 °F
Condenser saturation temperatureminimum -40 °F
105 °F

Results

Suction superheat
15.0 °F
Liquid subcooling
20.0 °F
Superheat assessment
Normal operating range
Subcooling assessment
High — suggests overcharge or a restricted metering device

Step by step

  1. 1Values used
  2. 2Superheat
  3. 3Subcooling
  4. 4Suction superheat= 15.0 °F
  5. 5Liquid subcooling= 20.0 °F
  6. 6Superheat assessment= Normal operating range
  7. 7Subcooling assessment= High — suggests overcharge or a restricted metering device

Assumptions and limits

  • The result is derived only from the 4 inputs listed above. Anything not among them is not part of the calculation.
  • In particular, this calculator does not take inflation, tax, fees or charges or compounding frequency into account.
  • Figures are rounded for display to 1 decimal place, so totals built from several rounded parts can differ slightly from the unrounded arithmetic.

How these calculators are built and tested is described on the Methodology page. If a figure looks wrong, please report it.

Frequently Asked Questions

How is the Superheat And Subcooling figure worked out?

Superheat = suction line temp - evaporator saturation temp. Superheat is how far the suction vapour has been heated above its saturation temperature, and subcooling is how far the liquid has been cooled below it.

Which one do I trust when they disagree?

On a TXV or EEV system charge by subcooling, because the valve holds superheat constant. On a fixed orifice system charge by superheat using the manufacturer's target chart.

What values do I need to enter?

This calculator takes 4 inputs: Suction line temperature, Evaporator saturation temperature, Liquid line temperature, Condenser saturation temperature. The pre-filled defaults are a realistic worked example — replace them with your own site or project figures.

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