R-32 (A2L)
R-32 Superheat & Subcooling Calculator
Check charge on R-32 equipment with the calculator preloaded for the pure A2L refrigerant behind most ductless mini splits. Full PT chart, charging targets, and the service notes that make R-32 different: zero glide, higher head pressures, hotter discharge.
R-32 Pressure-Temperature Chart
| Pressure (psig) | Sat. Temp (°F) |
|---|---|
| 26.8 | -20°F |
| 37.1 | -10°F |
| 49.3 | 0°F |
| 63.5 | 10°F |
| 71.5 | 15°F |
| 80 | 20°F |
| 89.2 | 25°F |
| 99.1 | 30°F |
| 109.7 | 35°F |
| 121 | 40°F |
| 133 | 45°F |
| 145.9 | 50°F |
| 159.5 | 55°F |
| 174.1 | 60°F |
| 189.5 | 65°F |
| 205.8 | 70°F |
| 223.2 | 75°F |
| 241.5 | 80°F |
| 260.9 | 85°F |
| 281.3 | 90°F |
| 302.9 | 95°F |
| 325.7 | 100°F |
| 349.6 | 105°F |
| 374.9 | 110°F |
| 401.4 | 115°F |
| 429.3 | 120°F |
| 458.6 | 125°F |
| 489.4 | 130°F |
R-32 suction pressures land close to R-410A, but the high side runs noticeably higher: at 100°F condensing, R-32 reads about 326 psig where R-410A reads 317 psig. If you jump between R-410A and R-32 equipment all day, the elevated head pressure on a healthy R-32 system is normal, not a dirty condenser.
R-32 Target Superheat & Subcooling
| Metering device | Target superheat | Target subcooling | Charging method |
|---|---|---|---|
| TXV | 8–15°F | 8–14°F | Charge by subcooling; the TXV holds superheat |
| Fixed orifice (piston) | 5–20°F | 4–10°F | Charge by superheat from the manufacturer charging chart |
On inverter mini splits, these generic ranges are a sanity check, not a charging method. Compressor speed changes both pressures continuously, so always use the manufacturer test mode and the service manual tables, and charge by weight.
Where You Will See R-32
R-32 (difluoromethane) is a pure single-component A2L refrigerant with a GWP of 675. It has dominated ductless equipment worldwide for a decade, and in the US it is now standard across mini splits and multi-zone systems from Daikin, Mitsubishi Electric, Fujitsu, LG, and others. Some ducted and side-discharge equipment uses it as well, though most US ducted lines went to R-454B. If you service ductless, you service R-32.
Because R-32 is a pure compound, it has zero temperature glide: it boils and condenses at a single temperature for a given pressure. That makes PT work simple. It also means vapor charging cannot fractionate anything, one of the few refrigerants left where topping off from the vapor port is technically harmless (still follow the manufacturer procedure).
R-32 Charging Notes
The two field realities that separate R-32 from R-410A: discharge temperature and charge criticality. R-32 compresses hotter, roughly 15–30°F higher discharge temperature at comparable conditions, so manufacturers lean on injection circuits and inverter limits to protect the compressor. A slightly overcharged or airflow-starved R-32 unit hits discharge protection faster than R-410A equipment would, which is worth remembering when a unit derates or trips on hot afternoons.
Charge criticality comes from the equipment type. Mini splits hold small, precisely specified charges: factory charge plus an adder per foot of line set beyond the base length, both printed on the nameplate. Superheat and subcooling verify the result and diagnose faults, but the charging method is the scale. When history on a system is unknown, recover, pull a proper vacuum, and weigh the charge back in rather than chasing numbers by feel.
A2L handling applies just like R-454B: A2L-rated recovery equipment and leak detectors, no open flame on a charged circuit, ventilation in tight spaces, and keep any factory refrigerant-leak sensors functional after service.
Worked Example: R-32 System Check in Test Mode
An R-32 multi-zone system running the manufacturer forced-cooling test mode, with gauge access on both service ports. Field readings: suction pressure 121 psig, suction line temperature 49°F, liquid pressure 312 psig, liquid line temperature 88°F.
Saturated suction temp at 121 psig = 40°F
Superheat = 49°F − 40°F = 9°F
Saturated liquid temp at 312 psig = 97°F
Subcooling = 97°F − 88°F = 9°F
Diagnosis: Superheat 9°F and subcooling 9°F both land inside the 8–15°F and 8–14°F targets. The charge checks out against the service manual values for these conditions. Note the higher head pressure than an R-410A tech expects: 312 psig at only 97°F condensing is normal for R-32.
R-32 Charging FAQs
What is normal superheat for R-32?
With a TXV or EEV, target superheat for R-32 is 8-15°F. With a fixed orifice, use the manufacturer charging chart (typically 5-20°F depending on outdoor ambient and indoor wet bulb). On inverter-driven mini splits, superheat floats with compressor speed, so check it in the manufacturer's forced-run or test mode and treat the installation manual value as the target.
Is R-32 the same as R-410A?
No, but they are related. R-410A is a 50/50 blend of R-32 and R-125; R-32 by itself is a pure single-component refrigerant. R-32 has a GWP of 675 versus 2,088 for R-410A, runs similar suction pressures, noticeably higher liquid pressures, and hotter compressor discharge temperatures. They are not interchangeable in equipment.
Can I put R-32 in an R-410A system?
No. R-410A equipment is not listed for flammable (A2L) refrigerants and lacks the leak detection and electrical design R-32 requires. Discharge temperatures also run hotter on R-32, which the R-410A compressor was not designed around. Service R-410A systems with R-410A.
Can I use R-32 gauges on R-454B?
Not for saturation readings. R-32 and R-454B have different pressure-temperature curves: at 100°F saturated, R-32 reads about 326 psig while R-454B reads about 297 psig. Reading a 454B system against an R-32 scale skews every superheat and subcooling number. Use the correct PT scale on your probes or select the actual refrigerant in this calculator.
Do I charge R-32 as liquid or vapor?
Either works without fractionation because R-32 is a pure compound, not a blend. Liquid charging is still faster and is what most manufacturers specify; throttle liquid slowly into the suction side so it flashes before reaching the compressor. Follow the equipment manual, and remember all handling must follow A2L practice.
Why are R-32 discharge temperatures so high?
R-32 has a higher heat of compression than R-410A, so compressor discharge runs roughly 15-30°F hotter at comparable conditions. Manufacturers manage this with vapor or liquid injection and discharge temperature limits in the inverter logic. For the tech it means discharge line temperature is a useful health check on R-32 equipment, and overcharging or restricted airflow shows up as discharge overheat trips sooner than it would on R-410A.
How do I check the charge on an R-32 mini split?
Weigh-in is the primary method: mini splits are critically charged, and the nameplate lists the factory charge plus an ounces-per-foot adder for line sets beyond the base length. Superheat and subcooling are verification and diagnostic tools, not the charging method. Run the unit in the manufacturer's test mode, compare readings to the service manual table for the current conditions, and if the charge is in doubt, recover, evacuate, and weigh it back in.
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