Refrigerant Pressure-Temperature Quick Reference
Why this matters
Field diagnosis of HVAC systems requires knowing what pressure should be at what temperature for each refrigerant. R-410A at 100°F should be 317 PSI on the high side. If gauge shows 250 PSI at 100°F, system is undercharged. The P-T chart is the field reference every HVAC tech uses; this is the consolidated card across common refrigerants.
How to read P-T charts
Saturated pressure = pressure of refrigerant in equilibrium with its liquid + vapor.
Read direction:
- Outdoor temp → corresponding high-side pressure
- Suction line temp → corresponding low-side pressure
- Superheat calculated as actual suction temp - saturated suction temp
- Subcooling calculated as saturated liquid temp - actual liquid line temp
R-410A (most common 2010+ residential)
Phase-out continuing 2025+; still dominant residential. EPA-rated maximum CO2 equivalent.
| Temp (°F) | Saturation pressure (PSIG) |
|---|---|
| 0 | 49 |
| 10 | 64 |
| 20 | 84 |
| 30 | 109 |
| 40 | 138 |
| 50 | 173 |
| 60 | 214 |
| 70 | 261 |
| 80 | 314 |
| 85 | 343 |
| 90 | 375 |
| 95 | 410 |
| 100 | 446 |
| 105 | 485 |
| 110 | 526 |
| 115 | 570 |
| 120 | 616 |
| 125 | 665 |
| 130 | 716 |
Critical temp: ~162°F. Beyond this, no liquid state regardless of pressure.
R-32 (next-generation residential 2024+)
Lower GWP (Global Warming Potential) than R-410A. Replacing R-410A in many new systems.
| Temp (°F) | Saturation pressure (PSIG) |
|---|---|
| 0 | 47 |
| 10 | 62 |
| 20 | 82 |
| 30 | 105 |
| 40 | 133 |
| 50 | 167 |
| 60 | 207 |
| 70 | 254 |
| 80 | 306 |
| 90 | 366 |
| 100 | 433 |
| 110 | 509 |
| 120 | 594 |
Similar to R-410A (within 5 - 10%); both A2L flammability classification.
R-22 (older residential, phasing out)
EPA-phased; production stopped 2020 U.S. (recovered/recycled stock still legal). Pre-2010 residential. NOT compatible with R-410A equipment.
| Temp (°F) | PSIG |
|---|---|
| 0 | 24 |
| 20 | 43 |
| 40 | 69 |
| 60 | 104 |
| 80 | 145 |
| 100 | 196 |
| 120 | 259 |
R-404A (commercial freezer)
| Temp (°F) | PSIG |
|---|---|
| -40 | 4 |
| -20 | 19 |
| 0 | 42 |
| 30 | 98 |
| 70 | 226 |
| 110 | 443 |
R-134a (older commercial + automotive)
| Temp (°F) | PSIG |
|---|---|
| 0 | 16 |
| 40 | 49 |
| 80 | 131 |
| 120 | 282 |
R-1234yf (auto next-gen, low-GWP R-134a replacement)
| Temp (°F) | PSIG |
|---|---|
| 0 | 17 |
| 40 | 47 |
| 80 | 114 |
| 120 | 240 |
R-454B (newer R-410A replacement)
Lower-GWP A2L refrigerant; pressure similar to R-410A within 3 - 8%.
How to use these charts in the field
Diagnosing AC operating (R-410A example):
Outdoor temp 95°F, condenser saturation 113 - 118°F target:
- Expected high-side pressure = ~ 410 - 460 PSI (correlates to 113 - 118°F)
- Actual reading at gauge
If low: undercharge OR insufficient airflow OR low load.
If high: overcharge OR dirty coil OR low airflow.
Low side:
- Indoor coil temp ~ 40°F target
- Expected low-side pressure = ~ 130 - 140 PSI for R-410A
- Actual reading
Superheat measurement:
- Suction line temp (with clamp thermometer)
- Saturated suction temp (from gauge pressure → P-T chart)
- Superheat = actual - saturated
- 8 - 15°F target typical for fixed orifice
- 8 - 12°F for TXV systems
Subcooling measurement:
- Liquid line temp at outdoor coil
- Saturated liquid temp (high-side gauge → P-T chart)
- Subcooling = saturated - actual
- 8 - 14°F target
Common refrigerant + chart errors
Wrong chart: R-410A reading on R-22 chart = wrong pressure target.
Wrong unit: PSIG vs PSIA off by ~14 PSI (atmospheric).
Ambient vs saturation: outdoor air temp ≠ saturated temp.
Probe placement: wrong location on tube = wrong reading.
Pressure gauge calibration: check zero on gauge regularly.
Refrigerant identification
Cylinder color codes (varies by manufacturer; verify):
- R-22: light green / teal
- R-410A: pink / rose
- R-32: brown / off-white
- R-404A: orange
- R-134a: light blue
- R-1234yf: dark gray / white
ALWAYS verify with label - color codes vary.
EPA certification
Required for handling refrigerants:
- Type I: small appliance (refrigerator, window AC)
- Type II: high-pressure (residential + commercial split systems)
- Type III: low-pressure (chillers)
- Universal: all types
Per 40 CFR Section 82. Must carry card.
Recovery + recycling
All refrigerant must be recovered before any open service. EPA prohibits venting.
Recovery rates:
- < 102°F low pressure: vacuum to 0 inHg
-
102°F: vacuum to 0 inHg + additional
- High-pressure: 0 PSIG minimum
Charge cylinder transfer: from recovery cylinder to clean cylinder for reuse, OR send to reclaim facility.
P-T calculation shortcut
For R-410A specifically (rough field calc):
- Pressure (PSIG) ≈ 1.5 × Temperature (°F) at moderate ranges
- 80°F → 120 PSI (low side)
- 100°F → 150 PSI
Not exact but useful for sanity-check.
Field tools
Manifold gauge set: digital OR analog; rated for high-pressure refrigerants.
Clamp thermometer: for line temp.
Calibrated for refrigerant: charge scale.
Recovery machine: required for service.
Vacuum pump: 2-stage 5 CFM typical residential.
Charge cylinder: temperature-corrected refill cylinders.
The single highest-impact P-T habit is the CROSS-CHECK during diagnostics. Don't trust just gauge OR just thermometer; cross-check both. Read high-side pressure → look up saturated temp on chart → compare to actual outdoor temp + about 35°F (typical condenser approach). If those don't match within 5°F, something's off. Most parts-swap diagnoses come from believing one measurement; pros cross-check measurements + identify the actual problem.
References
- ASHRAE Refrigeration Handbook
- EPA 40 CFR 82 (refrigerant regulation)
- AHRI 700 (refrigerant purity standards)
- Manufacturer pressure-temperature charts (Carrier, Trane, Goodman, etc.)
- Manuall internal: Refrigeration Cycle Theory, HVAC Efficiency Ratings Reference