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 about 318 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 in the installed residential base. It is an A1 (non-flammable) blend, which is what separates it from the A2L replacements coming in behind it.
| Temp (°F) | Saturation pressure (PSIG) |
|---|---|
| 0 | 48 |
| 10 | 62 |
| 20 | 78 |
| 30 | 97 |
| 40 | 118 |
| 50 | 143 |
| 60 | 170 |
| 70 | 201 |
| 80 | 236 |
| 85 | 255 |
| 90 | 274 |
| 95 | 295 |
| 100 | 318 |
| 105 | 341 |
| 110 | 365 |
| 115 | 391 |
| 120 | 418 |
| 125 | 447 |
| 130 | 477 |
Critical temp: 160°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 | 49 |
| 10 | 63 |
| 20 | 80 |
| 30 | 99 |
| 40 | 121 |
| 50 | 146 |
| 60 | 174 |
| 70 | 206 |
| 80 | 241 |
| 90 | 281 |
| 100 | 326 |
| 110 | 375 |
| 120 | 429 |
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 | 16 |
| 0 | 33 |
| 30 | 69 |
| 70 | 147 |
| 110 | 270 |
R-134a (older commercial + automotive)
| Temp (°F) | PSIG |
|---|---|
| 0 | 6 |
| 40 | 35 |
| 80 | 87 |
| 120 | 171 |
R-1234yf (auto next-gen, low-GWP R-134a replacement)
| Temp (°F) | PSIG |
|---|---|
| 0 | 9 |
| 40 | 38 |
| 80 | 89 |
| 120 | 169 |
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 = ~ 380 - 410 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 = ~ 118 PSI for R-410A at a 40°F coil (about 130 PSI at 45°F)
- 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.
How far you have to pull it down is set by the appliance type and its charge size, not by a single rule of thumb. EPA publishes the required evacuation levels in 40 CFR 82.156; read them off that table or off your recovery machine's listing, because the number changes between a residential split system, a large commercial rack, and a low-pressure centrifugal chiller. Small high-pressure residential equipment (R-22, R-410A, R-32) is the common case and comes down to atmospheric. Low-pressure chillers go far deeper and need a machine listed for that duty.
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) ≈ 3 × Temperature (°F) between 40°F and 100°F saturation
- 40°F → 120 PSI (actual 118)
- 80°F → 240 PSI (actual 236)
- 100°F → 300 PSI (actual 318)
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 outdoor air temp plus the condenser split. On modern high-efficiency equipment that split runs about 20°F over ambient; on older standard-efficiency units it stretches toward 30°F. That is why the 95°F example above targets a 113 to 118°F saturated condensing temperature. If the measured split lands well outside that, 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