R-407A PT Chart: How to Actually Read the Pressures
Real R-407A pressure-temperature values in °F and °C, why the liquid and vapor columns sit so far apart, which one to use for superheat and subcooling, and which leak repair rules bind an R-407A system.
On this page
- What are the actual R-407A pressures?
- Why are the liquid and vapor columns so far apart?
- Which column do you use for superheat and subcooling?
- What should R-407A suction pressure be?
- Does Section 608 leak repair apply to an R-407A system?
- Is R-407A a drop-in replacement for R-22?
- What this means on the job
- Frequently asked questions
- What is R-407A pressure at 40 °F?
- Which column of the R-407A chart do I use?
- What is the glide of R-407A?
- Is R-407A the same as R-407C?
- Does R-407A require leak repair?
- Do I need a special certification to work on R-407A?
- Sources
At 40 °F saturation, R-407A reads about 69 psig on the vapor column and about 86 psig on the liquid column. At 100 °F, it reads about 210 psig vapor and 238 psig liquid. R-407A is a zeotropic blend with a wide glide, so the two columns are not interchangeable. Use the vapor column for superheat and the liquid column for subcooling.
R-407A turns up in commercial refrigeration: walk-ins, reach-ins and rack systems that were built for, or converted away from, R-22 and R-404A. Most R-407A charts online are a bare distributor PDF with two columns and no explanation, which is a problem the first time you pick the wrong column and miss your target by ten degrees. It is also a refrigerant where the leak repair rules that apply in 2026 are not the ones most technicians learned for Section 608.
What are the actual R-407A pressures?
These values come from the Arkema Forane 407A saturation pressure-temperature chart, which was generated from the NIST REFPROP database. Pressures are psig.
| Temperature | Liquid (bubble) | Vapor (dew) |
|---|---|---|
| −20 °F (−28.9 °C) | 15.6 psig | 8.5 psig |
| −10 °F (−23.3 °C) | 23.2 psig | 14.9 psig |
| 0 °F (−17.8 °C) | 32.2 psig | 22.5 psig |
| 10 °F (−12.2 °C) | 42.8 psig | 31.6 psig |
| 20 °F (−6.7 °C) | 55.1 psig | 42.3 psig |
| 30 °F (−1.1 °C) | 69.3 psig | 54.8 psig |
| 40 °F (4.4 °C) | 85.6 psig | 69.4 psig |
| 50 °F (10.0 °C) | 104.2 psig | 86.1 psig |
| 70 °F (21.1 °C) | 148.8 psig | 127.0 psig |
| 90 °F (32.2 °C) | 204.8 psig | 179.3 psig |
| 100 °F (37.8 °C) | 237.7 psig | 210.4 psig |
| 110 °F (43.3 °C) | 273.9 psig | 245.2 psig |
| 120 °F (48.9 °C) | 314.0 psig | 284.0 psig |
For orientation, the vapor column runs close to R-22 and the liquid column sits closer to R-404A, and both are well below R-410A. Set your digital manifold to R-407A before you connect it. If the unit label says R-407C or R-407F, this is the wrong chart even though the names look alike, and the R-407C chart is the one to use for that blend.
Why are the liquid and vapor columns so far apart?
Because R-407A is a blend whose components boil at noticeably different temperatures.
R-407A is a mixture of R-32, R-125 and R-134a. The bubble point is where liquid first starts to boil; the dew point is where the last liquid has vaporized. In between, the mixture is part liquid and part vapor and its temperature climbs. That climb is temperature glide.
You can read the glide straight off the chart. At 40 °F the vapor column says 69.4 psig, and the liquid column shows that same pressure (69.3 psig) at 30 °F. The same pressure is a 30 °F bubble point and a 40 °F dew point, so the glide there is about 10 °F, and it runs around 8 to 11 °F across the working range. That is far more than a near-azeotropic blend like R-404A, which is under 2 °F.
For a technician, it means the single "saturation temperature" you may be used to from an R-22 chart does not exist. The same pressure corresponds to two temperatures, and the right one depends on what you are calculating.
Which column do you use for superheat and subcooling?
| Calculation | Pressure you read | Chart column | Where you take the temperature |
|---|---|---|---|
| Superheat | Suction, at the evaporator outlet or service port | Vapor (dew) | Suction line, at the same point |
| Subcooling | Liquid line | Liquid (bubble) | Liquid line, near the condenser or receiver outlet |
A worked example. Suction reads 42.3 psig, and the vapor column says that is a 20 °F dew point. If the suction line is 30 °F at that spot, you have 10 °F of superheat. On the liquid side, a reading of 237.7 psig corresponds to a 100 °F bubble point. If the liquid line is 90 °F, you have 10 °F of subcooling.
Use the wrong column and the error is not small. Reading 42.3 psig against the liquid column would put the evaporator near 3 °F, an error of roughly 17 degrees. Superheat and subcooling, and what each reading actually tells you covers how the two readings combine to diagnose a system.
Because of the glide, R-407A should be charged as a liquid out of the cylinder. Vapor leaves the cylinder richer in the lighter components and shifts the blend. Follow the manufacturer's charging instructions for the equipment.
What should R-407A suction pressure be?
There is no single correct number, and any chart that prints one is assuming a design you may not have.
Suction pressure follows evaporator coil temperature, which the equipment designer sets some degrees below box temperature. As an illustration only: a freezer coil designed to run near −20 °F corresponds to a vapor-column reading of about 8.5 psig. A medium-temperature cooler coil near 20 °F corresponds to about 42 psig. If the number you see is far from the design, the diagnosis comes from comparing the coil temperature and superheat to the manufacturer's targets, not from the chart alone.
Head pressure works the same way. Liquid pressure maps to a condensing temperature, and that temperature sits above the air or water the condenser rejects heat into. A condenser on a 95 °F roof and one in a cool machine room will read very differently and both can be correct.
Does Section 608 leak repair apply to an R-407A system?
The answer has two halves, and the second is the one that is easy to miss.
Under Section 608, no. The leak repair rule at 40 CFR 82.157 applies to appliances with 50 pounds or more of a Class I or Class II refrigerant (CFCs and HCFCs such as R-22). R-407A contains only HFCs, so it is not covered.
Under the AIM Act, it can be. EPA's Emissions Reduction and Reclamation rule set up a separate leak repair program at 40 CFR 84.106. According to EPA's leak repair fact sheet, it covers appliances holding 15 pounds or more of a refrigerant containing an HFC, or a substitute with a GWP above 53. R-407A contains HFCs, so an R-407A appliance at or above that charge falls inside it.
| Section 608 (40 CFR 82.157) | AIM Act (40 CFR 84.106) | |
|---|---|---|
| Refrigerants covered | CFCs and HCFCs, or blends containing them | HFCs, and substitutes with GWP above 53 |
| Charge threshold | 50 lb or more | 15 lb or more |
| R-407A rack with 40 lb | Not covered | Covered |
The duty falls on the owner or operator, but the owner cannot calculate a leak rate without your service records of what you added and when. The rest of Section 608 still applies in full. You may not knowingly vent the refrigerant (40 CFR 82.154), and you must recover it to the required level before opening the system (40 CFR 82.156). R-407A systems are high-pressure, so this is Type II work. For a high-pressure appliance under 200 pounds, recovered with equipment manufactured on or after November 15, 1993, the required level is 0 inches of mercury. That date is the recovery machine's manufacture date, not the appliance's. A 500-micron dehydration vacuum before charging is good service practice, not the Section 608 recovery requirement.
Is R-407A a drop-in replacement for R-22?
Not a true one. R-407A is used as an R-22 replacement in commercial refrigeration, but a retrofit involves more than swapping the cylinder. The lubricant, the metering device and the expected pressures all need to be checked against the equipment manufacturer's retrofit guidance, and the glide changes how you read the gauges. R-22 replacement refrigerant: what actually works covers the options and what Section 608 requires during a retrofit. Section 608 does not require a retrofit in the first place, and it does not stop you from servicing an existing R-22 system.
What this means on the job
Confirm the refrigerant on the nameplate before you pick a chart. Read suction against the vapor column and liquid against the liquid column, and compare superheat and subcooling to the manufacturer's targets rather than a number from a forum. Charge as a liquid.
When you add refrigerant to a system holding 15 pounds or more, record how much, what, when and on which appliance, and give the record to the owner. If a system keeps needing top-ups, find the leak first. If you are still working toward Type II, the Type II practice test covers the recovery levels and leak rates these systems depend on.
Frequently asked questions
What is R-407A pressure at 40 °F?
About 69.4 psig on the vapor column and 85.6 psig on the liquid column, per the Arkema chart. Use the vapor figure to find the dew point for superheat and the liquid figure for the bubble point for subcooling. The gap between them reflects the blend's temperature glide.
Which column of the R-407A chart do I use?
Use the vapor, or dew point, column when calculating superheat from suction pressure. Use the liquid, or bubble point, column when calculating subcooling from liquid-line pressure. Because R-407A glides by roughly 8 to 11 °F, picking the wrong column produces a large error.
What is the glide of R-407A?
The chart shows roughly 8 to 11 °F of glide across the working range, meaning the liquid pressure equals the vapor pressure about that many degrees higher. It comes from the different boiling points of its three components, R-32, R-125 and R-134a, and is the reason the blend is charged as a liquid.
Is R-407A the same as R-407C?
No. They share a number family but are different blends with different compositions and different pressures. Check the nameplate and use the chart for the refrigerant actually in the system. Mixing up the two charts leads to wrong superheat and subcooling figures.
Does R-407A require leak repair?
Not under Section 608, which covers CFC and HCFC systems. Under the AIM Act leak repair rule at 40 CFR 84.106, appliances with 15 pounds or more of an HFC-containing refrigerant are covered. Owners are responsible, but they rely on your service records.
Do I need a special certification to work on R-407A?
No. A Type II or Universal Section 608 certification covers high-pressure appliances, including R-407A systems, and the certification does not expire. What changes with R-407A is the record keeping you provide for the AIM Act leak rules, not the credential you hold.
Sources
- Arkema, Forane 407A Saturation Pressure-Temperature Data
- EPA, Leak Repair Requirements for Appliances Containing HFCs and Certain Substitutes (fact sheet, January 2026)
- 40 CFR 84.106 — Leak repair
- 40 CFR 82.157 — Appliance maintenance and leak repair
- 40 CFR 82.154 — Prohibitions
- 40 CFR 82.156 — Proper evacuation of refrigerant from appliances
Notice
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