What Should R-22 Pressures Be?
Typical R-22 suction and discharge pressure ranges for residential air conditioning, indexed by outdoor ambient. Includes a four-step diagnostic procedure and the saturation-vs-operating distinction explained.
Saturation pressure ≠ operating pressure
The numbers below are operating pressures — what your manifold gauges read on a running system at a given outdoor ambient. Operating pressures depend on charge, ambient, indoor load, superheat, and subcooling. The R-22 saturation pressures are different — those are thermodynamic equilibrium values you can look up on the R-22 PT chart.
Operating pressure ranges
| Condition | Suction (low side) | Discharge (high side) | Superheat target | Subcooling target |
|---|---|---|---|---|
| Residential AC at 75°F outdoor, 75°F indoor return | 62–72 PSIG | 175–215 PSIG | 8–18°F | 8–14°F |
| Residential AC at 85°F outdoor | 65–75 PSIG | 210–250 PSIG | 8–15°F | 8–14°F |
| Residential AC at 95°F outdoor (rating condition) | 65–75 PSIG | 240–280 PSIG | 8–15°F | 8–12°F |
| Residential AC at 105°F outdoor | 70–80 PSIG | 275–320 PSIG | 10–18°F | 6–12°F |
| Residential AC at 115°F outdoor (hot-climate extreme) | 72–85 PSIG | 310–360 PSIG | 10–20°F | 5–10°F |
Source: ACCA Manual T charging procedures; EPA Section 608 study materials; manufacturer service literature for residential split systems on R-22
R-22 systems run at meaningfully lower pressures than R-410A or R-32 systems — the suction side typically sits in the 60–80 PSIG band rather than 120–145 PSIG, and the discharge side in the 240–320 PSIG band rather than 350–410 PSIG. That difference is structural: R-22 has a lower vapor pressure at every temperature. It is also why R-22 system components are not rated for the higher pressures of HFC systems, and why direct retrofits between the families are not feasible without component replacement.
The ranges above assume a properly-charged system in normal operating condition with adequate indoor airflow (typically 400 CFM/ton). Pressures outside the ranges suggest charge, airflow, or component issues — the diagnostic procedure below walks through how to interpret them.
R-22 saturation pressure quick reference
Saturation pressure at common service temperatures, from the verified PT dataset (CoolProp 7.2.0). Use this for quick mental cross-reference against your manifold readings — operating pressure on a running system varies around these saturation values based on charge, ambient, and load.
| Temperature | Saturation (PSIG) | PSIA | kPa gauge |
|---|---|---|---|
| -20°F | 10.2 | 24.9 | 70 |
| 0°F | 24.0 | 38.7 | 166 |
| 20°F | 43.1 | 57.8 | 297 |
| 40°F | 68.6 | 83.3 | 473 |
| 70°F | 121.4 | 136.1 | 837 |
| 95°F | 181.8 | 196.5 | 1253 |
| 120°F | 260.0 | 274.7 | 1792 |
R-22 saturation curve over the service temperature range. Source: CoolProp 7.2.0 (REFPROP-compatible Helmholtz EOS), generated 2026-06-05.
Operating envelope across application conditions
Operating pressure ranges visualized — suction (blue) and discharge (red) bars at each application condition. Wider bars indicate larger variation expected; tighter bars indicate the operating point is more constrained.
R-22 property snapshot
| Safety class | A1 |
| Type | hcfc |
| GWP (IPCC AR5, 100-yr) | 1810 |
| ODP | 0.055 |
| Normal boiling point | -41.5°F |
| Critical temperature | 205.1°F |
| Critical pressure | 709 PSIG |
| Temperature glide | 0.0°F |
| Lubricant compatibility | MO, AB |
| AIM Act affected | No |
Real service scenarios for R-22
Three field scenarios showing common diagnostic patterns when reading R-22 system pressures. Each maps manifold readings to a verdict and specific service action.
Properly-charged R-22 system at design ambient
Scenario · Residential R-22 TXV-equipped AC system, 95°F outdoor, 75°F indoor return air. System has been running 15-20 minutes at steady state and you're confirming charge.
R-22 undercharge — high SH + low SC fingerprint
Scenario · Same R-22 TXV system, six months later. Customer reports weak cooling on a 95°F day. You take readings to confirm what's going on.
R-22 overcharge — low SH + high SC fingerprint
Scenario · R-22 TXV system after a service add by gauge feel rather than weight. Compressor running noisy and customer reports higher power bills.
Operating envelope and equipment context — R-22
R-22pressures sit inside an operating envelope bounded by the refrigerant's thermodynamic properties (saturation curve, critical point) and the equipment's pressure-rated components. Understanding both bounds tells you what pressure readings are normal versus what readings indicate a system fault.
- Saturation envelope: R-22 saturation pressure ranges from 10 PSIG at −20°F to 182 PSIG at 95°F. Critical temperature is 205.1°F — above this point no saturation state exists.
- Equipment pressure rating: R-22 critical pressure is 709 PSIG. Per AHRI Standard 540-2020, the high-pressure cutout switch is typically set at approximately 85% of critical pressure to protect the compressor from running into the near-critical regime where small temperature swings produce large pressure excursions. For R-22, that's a practical cutout setpoint around 603 PSIG.
- Charging metric: R-22 is pure or near-azeotropic with minimal glide, so bubble ≡ dew on the saturation curve. Standard PT chart math applies without curve-selection concerns.
- Lubricant requirement: R-22 runs on MO / AB lubricant. Mineral oil is moisture-tolerant but limited to the refrigerant types it's rated for.
- Regulatory status: R-22 is not directly affected by the AIM Act. Service supply follows normal commodity dynamics.
Common R-22 measurement mistakes
- PSIG vs PSIA confusion. Service manifold gauges read PSIG; tables sometimes use PSIA. PSIA = PSIG + 14.696. Confusing the two shifts saturation lookups by ~5°F at low-side pressures.
- R-22 has minimal glide(pure refrigerant or near-azeotrope), so bubble ≡ dew on the saturation curve. Curve selection on the PT chart doesn't matter for R-22.
- Probing temperature without insulating. Ambient air pulls the reading toward room temperature, inflating apparent superheat or depressing apparent subcooling.
- Reading before steady state. Allow 10-20 minutes after compressor start for pressures and temperatures to stabilize.
- Treating saturation as operating. Saturation is the thermodynamic reference; operating pressure on a running system depends on charge, ambient, load, superheat, and subcooling.
When pressures fall outside R-22 normal range
Use the calculators on this site to convert your readings into superheat, subcooling, and diagnostic patterns:
- Superheat Calculator — suction PSIG + line °F → superheat for R-22.
- Subcooling Calculator — liquid PSIG + line °F → subcooling.
- Combined SH/SC/PT — both sides + pattern-matching diagnostic banner.
- System Pressure Diagnostic — multi-input diagnostic with approach temperatures.
- High head pressure causes — decision tree for high-side problems.
Diagnostic procedure
Step-by-step procedure to interpret R-22 pressure readings on a service call. Emitted as HowTo structured data for search-engine rich results.
1Measure outdoor ambient and indoor return-air temperatures
Record the outdoor dry-bulb temperature near the condenser unit (not in direct sun) and the indoor return-air temperature at the air handler. These set the expected operating range. R-22 residential AC is rated at 95°F outdoor / 80°F indoor dry-bulb (67°F wet-bulb) per AHRI standard 210/240.
Tools: Outdoor dry-bulb thermometer, Indoor return-air dry-bulb thermometer
2Read low-side (suction) and high-side (discharge) pressures
Connect the manifold gauge set to the suction and discharge service ports. Let the system run for 10–15 minutes under load before recording values — pressures stabilize after the system finds equilibrium with the load. Compare against the operating-range table above for your outdoor ambient.
Tools: Refrigerant manifold gauge set rated for R-22 (500 PSI minimum), Service-valve adapter if needed
3Compare to expected ranges and identify the deviation
If low-side is below normal range: suspect undercharge, restriction in the liquid line (filter-drier), or low evaporator airflow. If low-side is above normal: suspect overcharge, dirty evaporator coil, or compressor inefficiency. If high-side is above normal: overcharge, dirty condenser coil, restricted condenser airflow, or non-condensable contamination. If high-side is below normal: undercharge, low ambient, or compressor wear.
4Verify with superheat and subcooling
Pressure readings alone do not diagnose the cause. Measure superheat at the suction line and subcooling at the liquid line. Classic patterns: high superheat + low subcooling = undercharge; low superheat + high subcooling = overcharge; both abnormal in the same direction = airflow or metering device issue. The /superheat-calculator/ and /subcooling-calculator/ pages walk through the math; the combined calculator shows both with an interpretation banner.
Tools: Contact or clamp-on temperature probe (+/-1°F), Probe insulation
Frequently asked
›What's the normal operating pressure for R-22 at 95°F outdoor?
Expect roughly 65–75 PSIG suction and 240–280 PSIG discharge on a properly-charged residential R-22 system at the 95°F rating condition. Saturation pressure at 95°F is 181 PSIG; the suction is lower than saturation because the evaporator runs colder than ambient (typically a 40°F saturation), and the discharge is higher because the condenser runs hotter than ambient (typically 110–115°F saturation).
›How does R-22 pressure compare to R-410A?
R-22 operates at roughly 60% of R-410A's pressures across the operating envelope. On the same 95°F day with comparable system designs, R-22 suction is ~65–75 PSIG while R-410A is ~125–145 PSIG; R-22 discharge is ~240–280 PSIG while R-410A is ~350–410 PSIG. This is why R-410A equipment uses heavier-gauge tubing and higher-rated service equipment, and why R-22-to-R-410A is a full system replacement rather than a drop-in refrigerant swap.
›Why are my R-22 pressures higher than the table shows?
Most common: condenser airflow is restricted (dirty coil, blocked fins, leaves), the condenser fan is slow or off, or non-condensables (air, moisture from inadequate evacuation) are in the system. Less common: overcharge — but overcharge usually shows itself in subcooling more than discharge pressure. Always verify with subcooling: high subcooling + high discharge is the overcharge fingerprint.
›Why are my R-22 pressures lower than the table shows?
Most common: undercharge from a slow leak. Verify with superheat — high superheat + low subcooling is the undercharge fingerprint. Less common: indoor airflow problem reducing load (clogged filter, restricted ducts), low ambient (system runs short cycles), or compressor wear. Pressure-add charge ONLY after locating and repairing the leak per EPA Section 608.
›What lubricant is in an R-22 system?
Mineral oil (MO) is the historical standard for R-22. Alkylbenzene (AB) was used in some 1990s-era systems. POE oil is NOT used with R-22 in original systems — POE is required only for HFC retrofits. Adding POE to a working R-22 system serves no purpose and risks contamination.
›How accurate are these operating pressure ranges?
These are guidance ranges drawn from ACCA Manual T, EPA Section 608 study materials, and manufacturer service literature for residential split systems. Actual pressures depend on the specific equipment design, line-set length and elevation, charge accuracy, indoor airflow, and ambient conditions. The equipment data plate or service manual is the authoritative reference for any specific system.
R-22 full reference
Saturation chart, properties, retrofit guidance.
Superheat Calculator
Suction PSIG + line °F → superheat.
Subcooling Calculator
Liquid PSIG + line °F → subcooling.