R22 Superheat Chart
Target superheat for fixed-orifice R-22 residential AC. Same formula as R-410A; R-22 pressures are substantially lower across the envelope.
Interactive lookup and matrix
Measured at the return-air grille with a wet-wick psychrometer. Typical cooling: 60–72°F WB.
Shaded thermometer near the condenser. Design condition: 95°F.
| WB \ DB | 55°F | 60°F | 65°F | 70°F | 75°F | 80°F | 85°F | 90°F | 95°F | 100°F | 105°F | 110°F | 115°F |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| 50°F | 7.5 | 5.0 | — | — | — | — | — | — | — | — | — | — | — |
| 52°F | 10.5 | 8.0 | 5.5 | — | — | — | — | — | — | — | — | — | — |
| 54°F | 13.5 | 11.0 | 8.5 | 6.0 | — | — | — | — | — | — | — | — | — |
| 56°F | 16.5 | 14.0 | 11.5 | 9.0 | 6.5 | — | — | — | — | — | — | — | — |
| 58°F | 19.5 | 17.0 | 14.5 | 12.0 | 9.5 | 7.0 | — | — | — | — | — | — | — |
| 60°F | 22.5 | 20.0 | 17.5 | 15.0 | 12.5 | 10.0 | 7.5 | 5.0 | — | — | — | — | — |
| 62°F | 25.5 | 23.0 | 20.5 | 18.0 | 15.5 | 13.0 | 10.5 | 8.0 | 5.5 | — | — | — | — |
| 64°F | 28.5 | 26.0 | 23.5 | 21.0 | 18.5 | 16.0 | 13.5 | 11.0 | 8.5 | 6.0 | — | — | — |
| 66°F | 31.5 | 29.0 | 26.5 | 24.0 | 21.5 | 19.0 | 16.5 | 14.0 | 11.5 | 9.0 | 6.5 | — | — |
| 68°F | 34.5 | 32.0 | 29.5 | 27.0 | 24.5 | 22.0 | 19.5 | 17.0 | 14.5 | 12.0 | 9.5 | 7.0 | — |
| 70°F | 37.5 | 35.0 | 32.5 | 30.0 | 27.5 | 25.0 | 22.5 | 20.0 | 17.5 | 15.0 | 12.5 | 10.0 | 7.5 |
| 72°F | 40.5 | 38.0 | 35.5 | 33.0 | 30.5 | 28.0 | 25.5 | 23.0 | 20.5 | 18.0 | 15.5 | 13.0 | 10.5 |
| 74°F | 43.5 | 41.0 | 38.5 | 36.0 | 33.5 | 31.0 | 28.5 | 26.0 | 23.5 | 21.0 | 18.5 | 16.0 | 13.5 |
| 76°F | 46.5 | 44.0 | 41.5 | 39.0 | 36.5 | 34.0 | 31.5 | 29.0 | 26.5 | 24.0 | 21.5 | 19.0 | 16.5 |
— = target below 5°F; superheat charging not recommended at these conditions. Industry convention on Trane and Carrier bead charts.
R-22 saturation quick table (evaporator range)
R-22 saturation pressures at typical evaporator conditions. Values from CoolProp 7.2.0. R-22 is a pure HCFC — no glide, single curve.
| Saturation temp | PSIG |
|---|---|
| 35°F | 61.5 PSIG |
| 40°F | 68.6 PSIG |
| 45°F | 76.1 PSIG |
| 50°F | 84.1 PSIG |
| 55°F | 92.6 PSIG |
Where this R-22 chart comes from — the short version
The R-22 target values in the matrix above come from the same formula used for every fixed-orifice residential refrigerant — the R-22 specialization is just that we pair the target with an R-22 saturation quick table so you don't need a separate PT chart in hand. The formula itself, TSH = ((3 × WB) − 80 − DB) / 2, has a looser history than "spec" suggests: its precise origin was never recorded, and it survives because it's close enough in the heart of the chart where most residential charging happens.
The best account is recounted by HVAC School, who put the question to Wayne Pendergast, keeper of several published versions of the chart. The story traces to Carrier: a residential AC charged perfectly by weight on the lab bench, then run across a matrix of indoor and outdoor conditions with resulting superheat plotted at each point. That empirical plot — not a derived equation — is the ancestor of every target superheat chart in the trade, including this R-22 one. Treat as an industry account, not audited history. The formula came later; HVAC School describes it as "likely reverse engineered" from the chart. AC Service Tech's coverage concurs that the formula "may not match exactly" the chart it approximates: the small discrepancies near the middle widen substantially toward the corners, enough that the formula stops being trustworthy exactly where charging is most delicate.
That's why this page blanks target cells below 5°F. The sub-5°F corners are where published charts themselves go blank and where the formula's fit is least trustworthy — charging by superheat simply isn't reliable there. The universal target superheat chart page carries the full origin account.
Fixed-orifice only — the mechanism behind the rule
The chart applies to fixed-orifice R-22 metering (pistons, capillary tubes) and to nothing else. On a fixed-orifice system, superheat is what the charge produces — add refrigerant and SH falls, remove and SH rises, so SH IS the charging indicator. On an R-22 TXV or EEV system, the valve actively holds SH near a fixed setpoint by throttling; SH tells you the valve is working, not the charge. HVAC School's fixed-orifice-only rule reduces to that distinction: charge a system whose SH responds to charge by SH, and one whose SC responds to charge by SC. For R-22 systems with TXV metering, charge by subcooling per the OEM nameplate (typically 8–12°F) — this page does not apply to those.
Reading your gauges
On a properly-charged R-22 residential AC at 95°F outdoor with 64°F indoor WB, the evaporator runs around 40°F saturation (68.6 PSIG). The manifold reads slightly higher after superheat pickup on the suction line. Measured suction-line temperature minus 40°F is your measured superheat; match against the 8.5°F target from the matrix.
R-22 saturation pressures are about 60% of R-410A across the envelope — different absolute PSIG values but the same target-superheat math. If you're used to R-410A numbers and switch to an R-22 service call, adjust your gauge-reading habits, not the target.
The 95°F outdoor DB reference isn't arbitrary — it's the AHRI Standard 210/240 cooling rating condition, which is why residential AC specs and OEM charging charts center on the same anchor. If you're charging on a day materially warmer or cooler than 95°F outdoor, the target shifts along the DB axis but the matrix accounts for it directly. If your climate parks you chronically at sub-5°F targets (dry-air regions with warm outdoor DB), AC Service Tech's guidance is to consider a TXV conversion or an accumulator on the suction line — either restores enough operating margin to charge with confidence.
When target renders as "—"
Cells below 5°F blank because charging by superheat is unreliable at those setpoints. If you land in a blanked cell, verify WB and DB measurements first (dry wick = 2–3°F low; sun on the DB probe = 5–10°F high), then confirm the equipment is fixed-orifice.
Related tools
- Superheat Calculator — measured SH from suction PSIG and line temp.
- R-22 reference page — full PT chart, properties, phase-down context.
- What pressure should R-22 be? — full residential AC operating envelope.
- Target Superheat Chart (universal) — the formula and applicability, refrigerant-independent.
- R-22 vs R-410A comparison — pressure envelope, lubricant, and retrofit differences.
Frequently asked
›What is the target superheat for a fixed-orifice R-22 system?
It depends on indoor wet-bulb and outdoor dry-bulb. Use TSH = ((3 × WB) − 80 − DB) / 2. At the 64°F indoor WB / 95°F outdoor DB design point, target superheat is 8.5°F. Look up other combinations in the interactive matrix above.
›Is the target-superheat formula the same for R-22 and R-410A?
Yes. The formula sets the operating point based on load conditions (WB) and heat rejection (DB); the refrigerant enters only when you convert measured suction pressure to saturation temperature. The R-22 and R-410A charts have the same target values in the same cells — only the PT-chart conversion differs.
›Where do I still find R-22 fixed-orifice equipment in service?
R-22 residential AC production ended in 2010; virgin R-22 production stopped in January 2020 under the EPA HCFC phase-out. Equipment installed 1990–2010 is still widely in service and legal to maintain with reclaimed R-22. Most of that equipment uses fixed-orifice metering (piston or capillary tube), so the target-superheat method still applies during service.
›What is normal R-22 suction pressure at 95°F outdoor?
On a properly-charged R-22 residential AC at the 95°F rating condition, evaporator saturation runs around 40°F (68.6 PSIG). Manifold reads slightly higher due to superheat pickup on the suction line. See /what-pressure-should-r22/ for the full envelope and OEM-observed manifold band.
›Can I use this chart for an R-22 system retrofitted to R-407C or R-422D?
The target-superheat method still applies (retrofit blends don't change the fixed-orifice charging approach), but the suction-pressure to saturation-temperature conversion uses the retrofit refrigerant's PT curve. R-407C is zeotropic with ~11°F glide — use the dew curve at the evaporator outlet. R-422D is a near-azeotrope — single curve is adequate.
›Reclaimed R-22 is expensive. Is it worth troubleshooting to superheat target rather than just swapping the system?
Depends on remaining equipment life and reclaim cost in your market. Reclaimed R-22 typically runs $50–150/lb (2024–2026 residential service market). A residential AC with a ~4 lb charge and 5+ years of expected life is worth diagnosing and correcting to target. A 20+ year-old system with a leaking coil is often better replaced with new equipment; superheat-charge the new one instead.