Field calculation
Subcooling Calculator and Chart
Convert measured liquid-side pressure to bubble saturation temperature, then subtract measured liquid-line temperature.
Example: R-410A at 340.9 psig corresponds to about 105°F bubble saturation. With a 95°F liquid-line temperature, actual subcooling is about 10°F. Use the equipment manufacturer’s target and charging procedure for the final comparison.
Actual is not target
Actual subcooling is a measured thermodynamic temperature difference. Target subcooling is equipment-specific. Follow the charging procedure for the exact unit and refrigerant; do not treat the 5°F, 10°F, or 15°F reference differences as recommended targets.
Crawlable reference
R-410A Subcooling Reference Chart
Bubble saturation pressure from 70°F to 150°F, plus example liquid-line temperatures 5°F, 10°F, and 15°F below saturation.
Use the pressure/bubble-temperature columns for lookup. The three liquid-temperature columns show arithmetic differences only and are not charging recommendations.
No R-410A reference rows match the current search.
Scroll horizontally to view additional columns and vertically to view additional rows. Column headers remain visible while scrolling.
| Bubble temp °C | Saturation pressure | Example liquid-line temperature | Copy | ||||
|---|---|---|---|---|---|---|---|
| psig | kPa(g) | 5°F below | 10°F below | 15°F below | |||
| 70°F | 21.1°C | 201.8 psig | 1391 kPa(g) | 65°F | 60°F | 55°F | |
| 75°F | 23.9°C | 219.4 psig | 1513 kPa(g) | 70°F | 65°F | 60°F | |
| 80°F | 26.7°C | 237.0 psig | 1634 kPa(g) | 75°F | 70°F | 65°F | |
| 85°F | 29.4°C | 255.6 psig | 1762 kPa(g) | 80°F | 75°F | 70°F | |
| 90°F | 32.2°C | 274.1 psig | 1890 kPa(g) | 85°F | 80°F | 75°F | |
| 95°F | 35.0°C | 295.6 psig | 2038 kPa(g) | 90°F | 85°F | 80°F | |
| 100°F | 37.8°C | 317.0 psig | 2186 kPa(g) | 95°F | 90°F | 85°F | |
| 105°F | 40.6°C | 340.9 psig | 2350 kPa(g) | 100°F | 95°F | 90°F | |
| 110°F | 43.3°C | 364.7 psig | 2515 kPa(g) | 105°F | 100°F | 95°F | |
| 115°F | 46.1°C | 392.0 psig | 2703 kPa(g) | 110°F | 105°F | 100°F | |
| 120°F | 48.9°C | 419.4 psig | 2892 kPa(g) | 115°F | 110°F | 105°F | |
| 125°F | 51.7°C | 447.6 psig | 3086 kPa(g) | 120°F | 115°F | 110°F | |
| 130°F | 54.4°C | 475.9 psig | 3281 kPa(g) | 125°F | 120°F | 115°F | |
| 135°F | 57.2°C | 506.9 psig | 3495 kPa(g) | 130°F | 125°F | 120°F | |
| 140°F | 60.0°C | 538.0 psig | 3709 kPa(g) | 135°F | 130°F | 125°F | |
| 145°F | 62.8°C | 572.5 psig | 3947 kPa(g) | 140°F | 135°F | 130°F | |
| 150°F | 65.6°C | 607.0 psig | 4185 kPa(g) | 145°F | 140°F | 135°F | |
Reference scope: R-410A bubble saturation from 70°F to 150°F at 5°F increments. The calculator uses bounded linear interpolation between these source-aligned checkpoints and never extrapolates.
Table actions
Method
How Subcooling Is Calculated
Subcooling is the number of temperature degrees a liquid refrigerant is below its saturated-liquid temperature at the same pressure. In field work, first convert measured liquid-side pressure to the refrigerant’s bubble saturation temperature, then compare that value with the measured liquid-line temperature.
For refrigerant blends with meaningful temperature glide, use the bubble-point saturation temperature for liquid-line subcooling. Dew point is the vapor-side reference used for superheat.
Both temperatures must represent the same refrigerant and pressure condition. A positive result indicates liquid below its bubble saturation temperature.
Field setup
Where to Measure Subcooling
Use liquid-side pressure and liquid-line temperature at the manufacturer-specified service locations.
Liquid-side pressure
Measure gauge pressure at the liquid service port specified by the equipment manufacturer. The calculator converts that pressure to the R-410A saturated-liquid bubble temperature.
Liquid-line temperature
Clamp the temperature probe to the liquid line at the manufacturer-specified location. Use good metal contact and insulation around the probe when required by the procedure.
Calculate actual subcooling
Subcooling = bubble saturation temperature − measured liquid-line temperature.
A positive result means the measured liquid temperature is below the pressure-derived bubble temperature.
Measurement Sequence
- Confirm the refrigerant from the equipment documentation.
- Operate the system under the manufacturer’s stated charging conditions and allow it to stabilize.
- Measure liquid-side pressure at the specified service port.
- Measure liquid-line temperature at the specified location with good probe contact and insulation where required.
- Convert pressure to bubble saturation temperature and subtract the measured liquid-line temperature.
Interpretation
Actual Subcooling vs. Target Subcooling
Actual subcooling
A measured operating-state temperature difference calculated from pressure-derived bubble temperature and liquid-line temperature.
Target subcooling
An equipment-specific charging value supplied by the manufacturer. Some procedures adjust that target for line length, lift, or other installation conditions.
Use the OEM target
The calculator can compare actual subcooling with a target you enter, but it does not create or recommend the target.
Verification
Worked Subcooling Examples
Example 1 — R-410A actual subcooling
Given: liquid-side pressure = 340.9 psig; measured liquid-line temperature = 95°F.
Lookup: 340.9 psig corresponds to about 105°F bubble saturation temperature in the reference dataset.
Calculation: SC = 105 − 95 = 10°F.
Sanity check: line temperature is below bubble saturation temperature, so the entered state is consistent with subcooled liquid.
Example 2 — Compare with an OEM target
Given: the same measured state and an equipment target of 9°F.
Actual: 10°F. Difference: +1°F above the entered target.
Interpretation: the numerical comparison alone is not an instruction to add or remove refrigerant; apply the complete manufacturer charging procedure and tolerances.
Important limitations
What High, Low, or Negative Subcooling Can—and Cannot—Tell You
A subcooling reading is one diagnostic measurement, not a complete diagnosis. Refrigerant charge, condenser heat rejection, restrictions, airflow or water flow, metering-device behavior, sensor error, measurement location, ambient conditions, and equipment design can all affect the observed state.
- Lower than OEM target
- Can occur for multiple reasons. Verify measurement quality, operating conditions, and the complete OEM procedure before changing charge.
- Higher than OEM target
- Can also have multiple causes. Do not assume overcharge without additional system checks.
- Negative result
- The measured line temperature is above the calculated bubble temperature. Recheck refrigerant, pressure, units, probe location, and operating state.
- Correct target match
- Still does not by itself prove overall system performance or eliminate other faults.
Dataset scope: the live calculator on this release is intentionally limited to the validated embedded R-410A dataset. Do not use R-410A pressure values for another refrigerant; use the refrigerant pressure-temperature reference to obtain the correct bubble temperature.
Opening, recovering, adding, or removing refrigerant must follow applicable safety, environmental, certification, and equipment requirements.
Sources and Calculation Basis
The released server-rendered dataset is a transformed R-410A saturation reference with bounded interpolation; proprietary manufacturer charging tables are not reproduced.
The page separates property lookup from charging targets. Bubble saturation temperature is the liquid-side reference for subcooling; the manufacturer’s procedure controls the target and charging decision. The embedded R-410A values are a bounded field-reference subset aligned with the site’s current refrigerant pressure-temperature reference.
- CoolProp thermophysical-property projectCoolProp 8.0.0 is the handoff-approved open-source property-model basis. Saturated-liquid states use quality Q = 0. This page publishes a bounded, source-aligned field-reference subset rather than embedding a runtime dependency.
- NIST REFPROPReference-quality thermodynamic-property software used as independent validation context. Proprietary REFPROP software and bulk tables are not redistributed.
- ASHRAE TerminologySupports the definition of refrigeration subcooling relative to bubble-point temperature at the stated pressure. ASHRAE tables are not reproduced.
- Trane installation/service literature 18-AC77D1-6Used only to illustrate equipment-specific target subcooling, service-valve measurements, stabilization, and installation corrections. Manufacturer charging tables are not reproduced.
Dataset and Source-Check Details
- Publisher
- Turn2Engineering
- Shared page release
- CORE 18.2.0
- Property-model basis
- CoolProp 8.0.0 / saturated-liquid bubble state
- Released embedded dataset
- R-410A, 70°F to 150°F, 5°F checkpoints
- Interpolation
- Bounded linear interpolation only; no extrapolation
- Pressure reference
- Gauge pressure; standard atmosphere 14.6959 psi / 101.325 kPa
- Rights status
- Original transformed reference; proprietary ASHRAE/REFPROP/OEM tables not reproduced
- CSV scope
- Turn2Engineering transformed R-410A reference only
- Source checked
- August 15, 2026
Frequently asked questions
Subcooling Chart FAQ
Convert liquid-side pressure to the refrigerant’s bubble saturation temperature, then subtract the measured liquid-line temperature.
Use saturated-liquid bubble temperature for liquid-line subcooling; dew temperature is the vapor-side reference used for superheat on gliding blends.
Use the target and tolerance specified by the exact equipment manufacturer rather than assuming a universal target.
The entered liquid-line temperature is above the calculated bubble saturation temperature, so the measurements do not describe subcooled liquid under those assumptions.
No. Use the complete manufacturer charging procedure and verify refrigerant, operating conditions, measurement locations, airflow or water flow, and other required checks.
Field takeaway
Use Bubble Temperature for the Measurement and the OEM Procedure for the Target
Actual subcooling is bubble saturation temperature minus measured liquid-line temperature. Use the chart and calculator for the thermodynamic relationship, then use the equipment manufacturer’s target, tolerances, and charging instructions to interpret the result.
For additional refrigerants or a broader pressure-temperature lookup, continue with the Refrigerant Pressure Temperature Chart.