R-454B PT Chart: How to Actually Read the Pressures

At 40 °F saturated vapor, R-454B reads about 107 psig; at 100 °F saturated liquid, about 301 psig. Because R-454B is a zeotropic blend, its PT chart prints two saturation values per temperature: use the dew point with suction pressure for superheat, and the bubble point with liquid-line pressure for subcooling. R-454B runs roughly 5 to 10 percent lower than R-410A throughout.

Almost every R-454B PT chart online is a scan of a distributor's PDF with no explanation attached. That is fine if you already know what you are looking at. If you do not, the chart quietly hands you two different numbers for the same temperature and says nothing about which one belongs in which calculation. Pick wrong and your superheat is off by the width of the glide before you have made a single adjustment — and you will chase a charge problem that does not exist.

What are the actual R-454B pressures?

These come from the Chemours Opteon Pressure-Temperature Guide for A/C, document OPTXLPTAC-2, which lists Opteon XL41 — the trade name for R-454B — alongside R-410A on the same sheet.

Note how the chart is laid out. The low-temperature rows print the saturated vapor (dew) pressure, because that is the evaporator side where you calculate superheat. The high-temperature rows print the saturated liquid (bubble) pressure, because that is the condenser side where you calculate subcooling. It is built for air conditioning service, not for physics homework.

Saturated vapor — dew point, use for superheat

Temperature	R-454B	R-410A
−20 °F	22.6 psig	26.2 psig
−10 °F	31.8 psig	36.3 psig
0 °F	42.7 psig	48.2 psig
10 °F	55.4 psig	62.2 psig
20 °F	70.3 psig	78.4 psig
30 °F	87.4 psig	97.0 psig
40 °F	107.0 psig	118.4 psig
50 °F	129.3 psig	142.6 psig

Saturated liquid — bubble point, use for subcooling

Temperature	R-454B	R-410A
60 °F	161.1 psig	170.7 psig
70 °F	190.5 psig	201.8 psig
80 °F	223.4 psig	236.5 psig
90 °F	260.0 psig	275.4 psig
100 °F	300.8 psig	318.5 psig
110 °F	345.9 psig	366.4 psig
120 °F	395.7 psig	419.4 psig
130 °F	450.5 psig	477.9 psig

Always work from the current chart published by the manufacturer of the refrigerant actually in the cylinder, and set your digital manifold or app to R-454B rather than leaving it on R-410A.

Why does the chart give two numbers for one temperature?

Because R-454B is zeotropic. It is a blend of R-32 and HFO-1234yf whose components boil at different temperatures, so the mixture does not change state at one fixed temperature the way a single refrigerant does. It changes across a range.

The bubble point is where the liquid first starts to boil. The dew point is where the last of the liquid has vaporized. The spread between them is temperature glide, and for R-454B it is small — around 2 °F. Small is why R-454B feels familiar on the gauges. Small is not zero, which is why the chart still prints both.

R-410A is near-azeotropic, so its glide is negligible in service and a single column is enough. Moving to R-454B is the point where reading the correct column stops being optional. The composition and behavior of R-454B covers the blend itself in more detail, and R-32 against R-454B is worth reading if you see both in the field — R-32 is a single component with no glide at all, so its chart has only one column.

Which column do you use for superheat and subcooling?

This is the whole practical point of the chart:

Calculation	Pressure you read	Chart value you use
Superheat	Suction line	Dew point (saturated vapor)
Subcooling	Liquid line	Bubble point (saturated liquid)

The logic follows the physics. Superheat measures how far past complete vaporization the vapor has gone, and complete vaporization happens at the dew point. Subcooling measures how far below the start of condensation the liquid has dropped, and that boundary is the bubble point.

Swap them and every reading carries a built-in error equal to the glide. Two degrees does not sound like much until it is the difference between a charge you accept and a charge you keep adjusting.

Does a lower reading mean the system is undercharged?

No, and this is the most common misread on R-454B systems. R-454B is simply a lower-pressure refrigerant than R-410A at the same temperature — about 11 psig lower at 40 °F saturated vapor, about 18 psig lower at 100 °F saturated liquid.

A technician who spent a decade on R-410A has a set of expected gauge readings memorized. As R-410A is phased down and A2L equipment becomes the default, those numbers are wrong more often than not — and they are wrong in the direction that looks like a low charge. Adding refrigerant to bring the pressure up to the R-410A number you remember will overcharge the system.

Work from temperature and the correct chart column, not from remembered pressures. And if the system did lose charge, remember that a zeotropic blend cannot simply be topped off — the composition of what is left behind is no longer what is on the nameplate.

Do the pressures change what Section 608 requires?

No. Nothing about pressure changes your obligations under 40 CFR Part 82, and nothing about R-454B changes which certification you hold. A residential split system is a high-pressure appliance whether it holds R-410A or R-454B, so it is Type II work either way.

What does change is your equipment. Under 40 CFR 82.158, recovery equipment manufactured or imported on or after January 1, 2017 is certified under Appendix B3 for non-flammable refrigerants or Appendix B4 for flammable refrigerants. A machine approved only for A1 refrigerants is not approved equipment for an R-454B job, and that is a federal requirement rather than a manufacturer preference.

Two separate rulebooks are in play, and blurring them is how technicians get caught out:

Requirement	Where it comes from
Do not knowingly vent or release it	Section 608 — 40 CFR 82.154(a)
Recover the charge before opening the system	Section 608 — 40 CFR 82.156
Recovery equipment certified for flammable refrigerant	Section 608 — 40 CFR 82.158, Appendix B4
Charge liquid, never vapor, from a blend cylinder	Best practice — blend composition, not Part 82
Target pressures, superheat and subcooling values	Manufacturer — the equipment installation instructions
Ventilation, ignition-source control, charge limits	Not Part 82 — ASHRAE 15, the equipment listing, local code

The manufacturer's chart itself carries the handling warnings: do not mix refrigerants, no A2L is a retrofit refrigerant, A2Ls go in new equipment only, and always remove blends from the cylinder as liquid. Those are correct instructions. They are not Section 608 text, and knowing what EPA actually requires for A2Ls keeps the two straight.

What this means on the job

Replace the numbers in your head, not just the gauges in your bag. The habit that catches people is not ignorance of the chart — it is muscle memory from R-410A, which reads higher at every single temperature.

Concretely: set the manifold to R-454B before you connect it. Take the saturation temperature from the dew column when you are working suction, from the bubble column when you are working the liquid line. Compare your result to the target in the manufacturer's installation instructions for that specific unit, not to a rule of thumb.

Keep the current chart to hand rather than a printout of unknown vintage, and confirm your recovery machine is listed under Appendix B4 before the job, not after you have opened the system. If you are still working toward the Type II section, the practice questions on recovery, evacuation and blends cover the material these systems lean on hardest.

Frequently asked questions

Are R-410A and R-454B pressures the same?

No. They are close enough to feel familiar but different enough to matter. R-454B reads lower at every temperature — roughly 107 psig against 118 psig at 40 °F saturated vapor, and about 301 psig against 319 psig at 100 °F saturated liquid. Treating an R-454B reading as low charge is a common and expensive mistake.

What are good operating pressures for R-454B?

There is no universal answer, because correct pressures depend on the specific equipment, the load and the ambient conditions. Use the PT chart to convert pressure to saturation temperature, calculate superheat and subcooling, then compare those against the targets in that unit's installation instructions. Pressure alone tells you very little.

Do you charge R-454B as a liquid or a vapor?

Charge liquid. Pulling vapor from a zeotropic blend removes the more volatile component preferentially, changing the composition of both what enters the system and what stays in the cylinder. To get it into a running system, meter liquid through a restrictor into the suction line rather than dumping liquid at the suction port.

Which PT column do I use for subcooling on R-454B?

The bubble point, read against liquid-line pressure. Subcooling measures how far the liquid has dropped below the temperature at which condensation begins, and that boundary is the bubble point. Superheat uses the other column — dew point against suction pressure.

Can I read R-454B pressures off an R-410A gauge scale?

No. The scales differ at every temperature, so an R-410A scale will give you a saturation temperature several degrees off, and the error compounds through your superheat or subcooling math. Use a manifold or app set to R-454B, or read the pressure and convert with the correct chart yourself.

Does using R-454B require a different EPA certification?

No. Section 608 certification is decided by appliance class, not refrigerant, and there is no EPA A2L endorsement. Certification also does not expire. Separate flammable-refrigerant safety training may be required by your employer, a manufacturer or local code, which is a different thing from federal certification.

Sources

• Chemours, Opteon Pressure-Temperature Guide for A/C (OPTXLPTAC-2)
• Chemours, Opteon XL41 (R-454B) product information
• 40 CFR 82.154 — Prohibitions
• 40 CFR 82.158 — Standards for recovery and/or recycling equipment
• EPA, Refrigerant Recovery and Recycling Equipment Certification
• EPA, Section 608 Technician Certification Requirements