R-407A and R-407C are both HFC blends built to replace R-22, and both get quoted as the R-22 replacement by people who should know better. They are not interchangeable. One is a refrigeration blend, the other is an air-conditioning blend, and the difference usually shows up on the first service call after the retrofit.
Here is what actually separates them, how to choose for a specific system, and the retrofit steps that get skipped.
Why two replacements exist
R-22 was an HCFC, and its phaseout pushed the industry in two directions at once. Air-conditioning systems needed something that behaved like R-22 at the same pressures and temperatures. Commercial refrigeration needed something that could hold capacity at medium and low temperatures, where R-22 systems were also common.
R-407C was aimed at the first problem and R-407A at the second. Both are non-flammable A1 blends with zero ozone depletion potential, both need POE oil, and both have a temperature glide of roughly 5 K. The similarities are why they get confused. The differences are why they are not interchangeable.
What actually differs
| R-407A | R-407C | |
|---|---|---|
| Composition (R-32 / R-125 / R-134a) | 20 / 40 / 40 | 23 / 25 / 52 |
| GWP (AR4) | roughly 2,100 | roughly 1,800 |
| Built for | medium and low-temperature commercial refrigeration | R-22 air-conditioning retrofits, chillers |
| Evaporator behavior | closer to R-404A | closer to R-22 |
The composition is the whole story. R-407C carries more R-134a, which pulls its pressure-temperature curve close to R-22. R-407A carries more R-125, which is what gives it the capacity to hold a low-temperature case.
Picking the right one
Match the blend to the evaporator duty, not to the compressor brand or to whatever the supply house has on the shelf.
- Walk-ins, reach-ins, display cases, and other medium or low-temperature equipment: R-407A is the usual pick. In low-temperature duty it holds capacity closer to what the case was designed for.
- Residential and light-commercial splits, plus chillers: R-407C keeps pressures near R-22 levels, so the existing components stay in their design range.
- Anything running below about -10 degrees F evaporator: neither blend is a great fit, and the system should be evaluated as a replacement rather than a retrofit.
If you are converting a system that already runs one of them, the answer is simpler: stay with what is already in the system unless the equipment is being replaced anyway.
The retrofit steps that get skipped
Neither blend is a drop-in. A conversion touches more than the cylinder.
- Oil. R-22 systems run mineral oil, and both blends require POE. That means a full oil change, or at minimum a documented flush and new oil charge. Skipping this is how you get a sludged compressor six months later.
- Filter driers. Replace them. The retrofit will move debris that was sitting quietly in the system.
- Expansion valve. Expect to adjust superheat, and on some systems to change the TEV nozzle.
- Charge as liquid only. Both blends are zeotropic. Vapor charging pulls the wrong fraction out of the cylinder and leaves you with a charge that is not the blend you paid for.
- Label the equipment. New refrigerant, new charge weight, date. Future techs and future compliance records both depend on it.
Glide: the part that trips people
Both blends change temperature as they boil and condense, which is why a PT chart for these refrigerants lists two numbers per pressure. Using the wrong one throws your readings off by several degrees.
The practical rule: use the dew point when you calculate superheat at the evaporator, and the bubble point when you calculate subcooling at the condenser. If you have been reading superheat against an average or against the bubble point, your charge has been wrong by a few degrees this whole time and the system has been compensating for it.
Three mistakes worth naming
- Treating the two blends as interchangeable. They are not, and a low-temperature case charged with R-407C will struggle to pull down.
- Charging vapor. It is the fastest way to end up with an unknown mixture in the system.
- Sizing the charge by pressure alone. With glide in play, pressure tells you less than it does on an azeotrope.
Quick Reference
Can I use R-407C in a freezer?
Not as a first choice. R-407A holds low-temperature capacity better, and below roughly -10 degrees F you should be looking at replacement equipment rather than a retrofit.
Which one has the lower GWP?
R-407C, at roughly 1,800 against roughly 2,100 for R-407A. Both are far above the low-GWP alternatives now entering the market, so neither is a long-term answer on its own.
Do I need a new expansion valve?
Not always, but expect to adjust superheat and on some systems to change the nozzle. Plan for it in the quote rather than discovering it on site.
Can the two blends be mixed?
No. Mixing two zeotropic blends gives you a refrigerant nobody can identify, chart, or reclaim cleanly.
Ordering for a conversion
Match the cylinder to the job. A 25 lb R-407A cylinder covers a medium or low-temperature retrofit, while 25 lb of R-407C is the right call for an R-22 air-conditioning conversion. Both are factory-sealed, which matters more than it sounds when you are charging a blend by liquid weight.
If you want the charging procedure in more detail, the guide to charging blended refrigerants covers liquid charging, glide and the field checks that catch a bad charge before the customer does.
Pick the blend for the evaporator, change the oil, charge it as liquid, and label the unit before you leave.