Refrigerant PT Chart — Free Online Calculator
Look up the saturation pressure for R-410A, R-32, R-454B, or R-22 at any temperature between −40°F and 130°F. Enter the saturation temperature from your manifold gauge reading to get psig and bar(a) instantly — essential for calculating superheat and subcooling in the field.
Enter refrigerant and temperature
Typical range: −40 to 130°F (−40 to 54°C). Values outside this range are clamped to the table ends.
Saturation Pressure (psig)
Pressure bar(a)
—
Phase state
—
Warning
Data from ASHRAE 2021 tabulated values with linear interpolation. Pressures are gauge (psig) referenced to 14.696 psia atmospheric. For certification work, use a calibrated manifold set.
Common operating pressure reference
| Condition | Sat. Temp | R-410A (psig) | R-22 (psig) | R-32 (psig) |
|---|---|---|---|---|
| Normal suction (AC) | 40°F | 118 psig | 69 psig | 142.9 psig |
| Normal discharge (AC) | 120°F | 392 psig | 214 psig | 411.1 psig |
| Heat pump suction (heating) | 20°F | 105.7 psig | 40.4 psig | 100.2 psig |
| Ambient lock-out (~−10°F) | −10°F | 59.4 psig | 16.2 psig | 52.4 psig |
Sources: ASHRAE Handbook — Fundamentals (2021); manufacturer PT charts from Honeywell, Chemours, and Daikin. R-454B pressures closely track R-32 at −3 to −5%.
How the Refrigerant PT Chart Works
The pressure-temperature relationship for a pure refrigerant (or near-azeotropic blend) follows the Clausius-Clapeyron equation. Antoine constants are fit to measured saturation data from ASHRAE Fundamentals. This calculator uses tabulated data with linear interpolation between points for accurate field results without requiring iterative calculations.
Gauge vs absolute pressure
Manifold gauges read psig (gauge pressure), which is absolute pressure minus atmospheric (14.696 psi). Bar(a) is absolute pressure in bar. Add 14.696 psi to convert psig to psia, then multiply by 0.068948 to get bar(a).
Why refrigerants need their own PT chart
Each refrigerant has unique thermodynamic properties — molecular weight, critical point, and intermolecular forces — that determine how rapidly pressure changes with temperature. Never use one refrigerant's PT chart to diagnose a system charged with a different refrigerant.
Superheat calculation
Superheat = suction line temperature − saturation temperature at suction pressure. Read suction pressure, look up the corresponding saturation temperature on this chart, then subtract from the actual suction line temperature measured with a clamp probe.
R-454B and A2L safety
R-454B is an A2L mildly flammable refrigerant. Its PT curve is very close to R-410A — but equipment must be specifically rated for A2L refrigerants. A2L-rated manifold sets, recovery machines, and leak detectors are required.
Worked example
A concrete field example showing how to use the PT chart to diagnose refrigerant charge on an R-410A system.
Diagnosing superheat on an R-410A split system
You connect your manifold to an R-410A system and read 124 psig on the suction gauge. Your clamp thermometer on the suction line reads 52°F.
Conclusion: The suction pressure of 124 psig corresponds to a 30°F saturation temperature. With a 22°F superheat, the system is operating above the typical TXV target — check outdoor ambient, indoor conditions, and airflow before adding refrigerant.
Checking discharge pressure on an R-410A condenser at 95°F outdoor ambient
At 95°F outdoor ambient, the condensing saturation temperature is typically 30–35°F above ambient, so approximately 125–130°F.
Conclusion: A discharge pressure significantly above the PT-chart value for the expected condensing temperature indicates a problem — dirty coil, non-condensables in the system, or excessive charge are the primary suspects.
Frequently asked questions
Common questions about refrigerant PT charts and field pressure-temperature diagnostics.
What is a PT chart used for?
A pressure-temperature (PT) chart gives the saturation pressure of a refrigerant at any temperature. HVAC technicians use it to convert gauge pressure readings from their manifold gauges into the saturation temperature, then calculate superheat (suction side) or subcooling (liquid side). Every refrigerant has its own PT chart.
Why are R-410A and R-32 pressures so similar?
R-410A is a near-azeotropic blend of R-32 and R-125 (50/50 by weight). R-32 alone has slightly higher pressures than R-410A, particularly at higher temperatures. R-454B is designed to replace R-410A with lower GWP while maintaining similar pressures.
What pressure should I expect on the suction side of an R-410A AC?
At normal operating conditions (40°F evaporator saturation temperature), R-410A suction pressure is approximately 118 psig. During hot summer pulldown, suction pressure may temporarily be higher.
What is R-454B and when do I need it?
R-454B (trade name Opteon XL41) is an A2L mildly flammable refrigerant replacing R-410A in new equipment starting with DOE efficiency standards. Equipment designed for R-454B requires A2L-rated tools and procedures. Never substitute refrigerants without manufacturer authorization.
PT chart readings. Now quote the refrigerant repair.
A PT chart lookup tells you what the saturation condition should be — TradesQuote turns the service call scope into a detailed, line-item estimate in seconds. Describe the job or upload photos, and our AI builds quantities, unit prices, and totals, validated by a built-in quality control agent.
AI line-item estimates
Quantities, unit prices, and totals generated instantly.
Knowledge base
Upload past jobs so estimates reflect your real pricing.
Shareable & signable
Clients review, accept, and sign from a public link.
No credit card required · 14-day free trial · Cancel anytime