R410A Superheat Chart
Target superheat for fixed-orifice R-410A residential AC. Look up target by indoor WB × outdoor DB, then match against measured superheat at the suction line.
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-410A saturation quick table (evaporator range)
Convert suction pressure to evaporator saturation temperature (or vice versa) at typical AC evap conditions. Values from CoolProp 7.2.0.
| Saturation temp | PSIG (bubble) |
|---|---|
| 35°F | 107.7 PSIG |
| 40°F | 118.8 PSIG |
| 45°F | 130.6 PSIG |
| 50°F | 143.2 PSIG |
| 55°F | 156.5 PSIG |
Where this R-410A chart comes from — the short version
The R-410A target values in the matrix above come from the same formula used for every fixed-orifice residential refrigerant — the R-410A specialization is just that we pair the target with an R-410A 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-410A 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-410A metering (pistons, capillary tubes) and to nothing else. The mechanism is clean: 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-410A 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 the TXV / EEV side of R-410A charging, see the R-410A charging chart.
Reading your gauges
On a properly-charged R-410A residential AC at the 95°F rating condition with 64°F indoor WB, the evaporator runs around 40°F saturation (118.8 PSIG). The manifold at the low-side service port reads slightly higher than this due to superheat pickup on the suction line between the coil and the port. Measured suction-line temperature minus 40°F is your measured superheat; match against the 8.5°F target from the matrix.
At a warmer 105°F outdoor day the condenser saturation climbs into the 115–120°F range (419.4PSIG), the evaporator can hold at ~40°F saturation with adequate airflow, and the target superheat drops (target at 64°F WB / 105°F DB = 3.5°F — see the "—" footnote if the matrix blanks a cell). Charge decisions still follow the same procedure; the SH target just shifts.
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 out because charging by superheat becomes unreliable there — normal probe error swamps the target. If your operating point falls in a blanked cell, verify the measurements first (dry psychrometer wick, sun-shaded DB probe), then check that the system is actually fixed-orifice. Many modern R-410A residential AC units built after 2015 are TXV and should be charged by subcooling instead.
Related tools
- Superheat Calculator — measured SH from suction PSIG and line temp for R-410A and any other refrigerant.
- R-410A reference page — full PT chart, properties, GWP, lubricant, retrofit context.
- What pressure should R-410A be? — full residential AC operating envelope with head + suction ranges.
- R410A Charging Chart — two-method charging: TXV/EEV by subcooling, fixed-orifice by superheat.
- Target Superheat Chart (universal) — the underlying formula and applicability, refrigerant-independent.
Frequently asked
›What is the target superheat for a fixed-orifice R-410A system?
It depends on indoor wet-bulb and outdoor dry-bulb. Use the formula TSH = ((3 × WB) − 80 − DB) / 2. At the design point of 64°F indoor WB and 95°F outdoor DB, target superheat is 8.5°F. Look up other combinations in the interactive matrix above.
›How do I read R-410A suction pressure at the evaporator?
Connect the manifold to the low-side service port and read pressure in PSIG after 10–15 minutes of steady operation. Convert to evaporator saturation temperature using the R-410A quick table on this page (or the interactive PT calculator). The saturation temp is what the coil is boiling at; the suction-line temp minus that is superheat.
›Does R-410A have temperature glide that affects superheat measurement?
R-410A is a near-azeotrope with ~0.7°F glide — small enough that most techs treat it as a single-curve fluid for service purposes. The bubble and dew saturation curves are essentially the same. This differs from R-407C or R-454C, where the ~11°F and ~29°F glide requires using the dew curve at the evaporator outlet.
›Should I use this chart if my R-410A system has a TXV?
No. TXV systems regulate superheat to a fixed setpoint (typically 8–15°F) regardless of ambient. Superheat on a TXV system tells you the valve is working — it does not tell you the charge state. Charge TXV / EEV R-410A systems by subcooling (typically 8–12°F per the OEM nameplate). See the R-410A Charging Chart for the subcooling method.
›What is normal R-410A suction pressure at 95°F outdoor?
On a properly-charged residential R-410A system at the 95°F rating condition, the evaporator runs around 40°F saturation (118.8 PSIG). Actual manifold suction reads slightly higher after superheat pickup on the line between the coil and the service port. See /what-pressure-should-410a/ for the full operating envelope with the OEM-observed manifold band.
›The measured superheat is far from the target — what do I do?
First verify measurement: WB, DB, suction pressure, and line-temp probe placement. Then add or recover in small increments (1–2 oz at a time on residential systems), giving 5 minutes between adjustments to re-steady. Persistently high SH with low subcooling = undercharge. Persistently low SH with high SC = overcharge. Neither pattern matches = check indoor airflow and metering-device installation before touching charge.