R-454B (Puron Advance)
R-454B Superheat & Subcooling Calculator
Check charge on R-454B systems with the calculator preloaded for the A2L refrigerant that replaced R-410A in new ducted equipment. Full PT chart, TXV and fixed orifice targets, and the A2L handling notes that actually change how you charge.
R-454B Pressure-Temperature Chart
| Pressure (psig) | Sat. Temp (°F) |
|---|---|
| 20 | -24.3°F |
| 40 | -3.6°F |
| 60 | 11.9°F |
| 70 | 18.5°F |
| 80 | 24.5°F |
| 90 | 30°F |
| 100 | 35.2°F |
| 110 | 40°F |
| 120 | 44.6°F |
| 130 | 48.9°F |
| 140 | 52.9°F |
| 150 | 56.8°F |
| 160 | 60.5°F |
| 170 | 64.1°F |
| 180 | 67.5°F |
| 190 | 70.8°F |
| 200 | 73.9°F |
| 210 | 77°F |
| 220 | 80°F |
| 240 | 85.6°F |
| 260 | 90.9°F |
| 280 | 95.9°F |
| 300 | 100.7°F |
| 320 | 105.2°F |
| 340 | 109.6°F |
| 360 | 113.8°F |
| 380 | 117.8°F |
| 400 | 121.6°F |
| 420 | 125.3°F |
| 450 | 130.6°F |
For quick sanity checks: a typical R-454B system on a mild day runs a 40–45°F evaporator, which puts suction pressure around 110–121 psig. Condensing at 100–110°F puts liquid pressure around 297–342 psig. If your gauges are far outside those windows with the system running steady, verify the reading before touching the charge.
R-454B 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 |
What Is R-454B?
R-454B is the A2L refrigerant that replaced R-410A in new ducted residential and light commercial equipment. Under the AIM Act, new AC and heat pump systems manufactured in the US moved to lower-GWP refrigerants starting January 1, 2025, and most major ducted equipment lines (Carrier, Bryant, Trane, American Standard, Lennox and others) chose R-454B. Carrier markets it as Puron Advance. It is a blend of R-32 and R-1234yf with a GWP of 466, versus 2,088 for R-410A.
The good news for charging: R-454B behaves very much like R-410A on the gauges. It runs slightly lower pressures at the same saturation temperature (42°F is about 114 psig on R-454B versus roughly 123 psig on R-410A), and the superheat and subcooling targets are the same 8–15°F and 8–14°F with a TXV. The diagnostic logic you know from R-410A carries over directly: high superheat with low subcooling still means low charge, low superheat with high subcooling still means overcharge.
A2L Charging Notes for R-454B
What changes is handling, not thermodynamics. R-454B is mildly flammable (A2L), which drives four practical rules. First, charge liquid only: R-454B is a zeotropic blend, and vapor charging fractionates it, pulling off a different composition than what stays in the cylinder. Second, use A2L-rated recovery machines, hoses, and leak detectors; standard R-410A recovery equipment is not listed for flammable refrigerants. Third, no brazing or open flame on a circuit holding charge; recover first, then purge with nitrogen while brazing. Fourth, respect the equipment leak-detection system: many R-454B air handlers carry refrigerant sensors that drive the blower on a detected leak per UL 60335-2-40, and that circuit must stay functional after service.
R-454B has about 2°F of temperature glide. That is small enough that published field PT charts use single averaged values, and this calculator does the same. On a critically charged system where you are splitting hairs at the edge of a target range, remember the glide adds roughly a degree of uncertainty; charge to the middle of the manufacturer target rather than the edge.
One thing R-454B is not: a retrofit refrigerant. R-410A equipment is not listed for A2Ls and cannot legally or safely take R-454B. Service existing R-410A systems with R-410A, and install R-454B only in equipment designed for it.
Worked Example: New R-454B Heat Pump with TXV
A 2026-installed R-454B heat pump in cooling mode, TXV metering. Field readings: suction pressure 110 psig, suction line temperature 50°F, liquid pressure 300 psig, liquid line temperature 91°F.
Saturated suction temp at 110 psig = 40°F
Superheat = 50°F − 40°F = 10°F
Saturated liquid temp at 300 psig = 100.7°F
Subcooling = 100.7°F − 91°F = 9.7°F
Diagnosis: Superheat 10°F sits inside the 8–15°F TXV target and subcooling 9.7°F sits inside 8–14°F. The system is properly charged. Log both numbers on the startup sheet: baseline readings on a new A2L install are worth their weight when the same unit gets a warranty call two summers later.
R-454B Charging FAQs
What should my subcooling be on 454B?
Target subcooling for R-454B with a TXV is 8-14°F, measured at the liquid line near the condenser outlet. Subcooling is the primary charging indicator on TXV systems. Many manufacturers print a specific subcooling target on the unit nameplate (often 10-12°F); the nameplate value always wins over generic ranges.
What is normal superheat for R-454B?
With a TXV, normal superheat for R-454B is 8-15°F at the suction line near the outdoor unit. With a fixed orifice, target superheat depends on outdoor ambient and indoor wet bulb, typically 5-20°F, so use the manufacturer charging chart. Superheat below 5°F risks liquid floodback to the compressor.
Can I use my R-410A gauges on R-454B?
Your manifold body handles the pressures fine because R-454B runs slightly lower than R-410A, but the R-410A temperature scale on an analog gauge will give wrong saturation temperatures. Use an R-454B PT scale, digital probes with R-454B selected, or this calculator. Hoses, recovery machines, and vacuum pumps used on R-454B should be A2L rated per the manufacturer.
Do I charge R-454B as liquid or vapor?
Charge R-454B as liquid from the cylinder. It is a blend of R-32 and R-1234yf, so vapor charging can fractionate the blend and shift its composition. Invert the cylinder (or use a liquid port) and throttle liquid into the suction side slowly through a charging valve or metering device so slugs never reach the compressor.
Is R-454B dangerous to work with?
R-454B is classified A2L: low toxicity and mildly flammable. It is much harder to ignite than propane (A3) and needs a strong ignition source plus a concentrated leak, but it changes work practices: no open flames or brazing on a charged circuit, A2L-rated recovery equipment, ventilation in enclosed spaces, and leak detection per UL 60335-2-40 on the equipment side.
Can I retrofit my R-410A system to R-454B?
No. R-454B is not a drop-in replacement for R-410A. Existing R-410A equipment is not listed for A2L refrigerants and lacks the required leak detection, airflow mitigation, and electrical design. Existing R-410A systems keep getting serviced with R-410A; R-454B goes only into equipment designed and listed for it.
Does R-454B have temperature glide?
Yes, but it is small, roughly 2°F. R-454B is a zeotropic blend, so bubble point and dew point differ slightly at the same pressure. In field practice the glide is close to gauge accuracy, and published PT charts for R-454B typically show single averaged values, which is how this calculator treats it. R-407C, by comparison, has 9-11°F of glide and needs explicit bubble/dew handling.
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All-Refrigerant Calculator
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A2L Charge Limit Calculator
Maximum A2L charge for a room, or minimum room area for a charge, per UL 60335-2-40 and ASHRAE 15.2. Covers R-454B, R-32, and 6 more refrigerants.
EPA Refrigerant Leak Rate Calculator
Topping off a 15+ lb system triggers a leak rate calculation under 40 CFR 84.106 as of January 1, 2026. Run the EPA math and check the thresholds.
BTU / HVAC Load Calculator
Size the system by climate zone, insulation, windows, and duct location with automatic tonnage recommendations.
Charging a brand-new A2L install? Check the sizing too.
New R-454B equipment means a fresh chance to catch an oversized replacement. Run the load by climate zone, insulation, and windows before you trust the old tonnage.