R-407C Refrigerant: What It Is, What It Replaces, and What Section 608 Says
What R-407C is made of, why it was built as an R-22 replacement, what changes when you retrofit, and which Section 608 and AIM Act rules apply when you service it.
On this page
- What is R-407C refrigerant?
- What does R-407C replace?
- How is R-407C different from R-22 and R-410A?
- Can you drop R-407C into an R-22 system?
- How do you charge R-407C?
- What does Section 608 require on an R-407C system?
- Is R-407C being phased out?
- What this means on the job
- Frequently asked questions
- What is R-407C refrigerant used for?
- Is R-407C a drop-in replacement for R-22?
- Can you mix R-407C and R-22?
- What oil does R-407C use?
- Is R-407C flammable?
- Do I need special certification to work on R-407C?
- Sources
R-407C is an HFC blend of R-32, R-125 and R-134a, rated A1 (non-flammable, low toxicity), with a GWP of about 1,774. It was designed to replace R-22 in air conditioning, and it has roughly 10 °F of temperature glide. It needs polyol ester oil, is charged as liquid, and falls under Type II (high-pressure) Section 608 work.
R-407C turns up in two places: converted R-22 equipment, and some chillers and packaged units built for it. The trouble starts when a technician treats it as "R-22 with a new label." It is a three-part blend with its own pressures, its own oil and its own charging rules. Get those wrong and you end up with a system that runs, but badly.
What is R-407C refrigerant?
R-407C is a zeotropic blend, which means its three components boil at different temperatures. Mixed by weight, it is about 23% R-32, 25% R-125 and 52% R-134a. None of the three contains chlorine, so R-407C has no ozone depletion potential. It is classified A1 by ASHRAE, the same safety group as R-22 and R-410A, so it is not an A2L refrigerant and carries no flammability handling rules.
Manufacturers built it to match R-22's capacity in air conditioning applications, at similar operating conditions. That is why EPA's SNAP program lists it as an acceptable R-22 substitute, and why most R-407C you meet in the field was a retrofit.
What does R-407C replace?
| Refrigerant | Replaced by R-407C? | Why or why not |
|---|---|---|
| R-22 | Yes, in air conditioning | Closest capacity match; the reason R-407C exists |
| R-410A | No | R-410A runs much higher pressures; the components are not compatible |
| R-404A | No | Different application (low temperature) and pressures |
| R-134a | Not typically | Different pressure range |
If you are weighing options for an aging R-22 system, R-22 replacement refrigerants and what actually works compares them. R-407C is the usual answer when the owner wants to keep the existing compressor and coils, and the usual wrong answer when someone expects it to be a pour-in swap.
How is R-407C different from R-22 and R-410A?
| R-22 | R-407C | R-410A | |
|---|---|---|---|
| Type | Single compound | Zeotropic blend | Near-azeotropic blend |
| Glide | None | About 10 °F | Under about 0.3 °F |
| Oil | Mineral | Polyol ester (POE) | Polyol ester (POE) |
| Charge as | Vapor or liquid | Liquid | Liquid |
| Pressures | Baseline | Close to R-22 | Much higher |
The pressure match is why technicians treat R-407C as the gentle option: your existing gauges, hoses and recovery cylinders are rated for it. A system that runs R-410A needs equipment rated for much higher pressures, which is covered in R-22 vs R-410A. The glide is the part that catches people. Read the actual values in the R-407C PT chart, which explains which column to use for superheat and which for subcooling.
Can you drop R-407C into an R-22 system?
Not as a simple top-off. A conversion has real steps:
- Recover the R-22 completely. You cannot mix the two.
- Change the oil. R-22 systems run mineral oil, and R-407C needs POE. Manufacturer guidance is to flush out the mineral oil down to a low residual percentage, so check the compressor maker's instructions rather than guessing.
- Replace the drier, and check the metering device and seals for compatibility.
- Weigh in the charge. R-407C does not charge at the same weight as R-22. Use the equipment manufacturer's retrofit guidance.
- Relabel the unit so the next technician knows what is inside.
None of this is a Section 608 requirement. It is the manufacturer's procedure and sound practice. Nothing in the regulation forces you to retrofit an R-22 system at all, and R-22 remains legal to service from reclaimed and stockpiled supply.
How do you charge R-407C?
Charge it as liquid from the cylinder, metered slowly into the suction side so liquid does not slug the compressor. A zeotropic blend charged as vapor draws off its lighter components first, which shifts the composition in both the cylinder and the system.
The same fractionation problem affects leaks. After a significant vapor leak, what remains may no longer be R-407C in the proportions the chart assumes. Topping it off keeps the error in the system. Recovering the charge and weighing in a fresh one removes it. That is manufacturer guidance and good service practice, not a Section 608 mandate. If you want to know what readings should look like once it is charged, superheat and subcooling and what each reading tells you covers the method.
What does Section 608 require on an R-407C system?
R-407C is high-pressure, so this is Type II work, and Universal certification covers it too.
- No venting. You may not knowingly release it while maintaining, servicing, repairing or disposing of an appliance. See 40 CFR 82.154.
- Recovery before opening. You must evacuate to the required level before opening the system, set out in 40 CFR 82.156. For a high-pressure appliance under 200 pounds recovered with equipment manufactured on or after November 15, 1993, that level is 0 inches of mercury. The date refers to the recovery machine, not the air conditioner.
- Section 608 leak repair does not reach it. The ozone-depleting-substance leak repair rule at 40 CFR 82.157 covers appliances with ozone-depleting refrigerant, and R-407C is not one.
- The AIM Act leak repair rule can apply. From January 1, 2026, 40 CFR 84.106 covers appliances holding 15 pounds or more of an HFC-containing refrigerant. Per EPA's leak repair fact sheet, the leak rate triggers are 10% for comfort cooling, 20% for commercial refrigeration and 30% for industrial process refrigeration, and the residential and light commercial air conditioning subsector is exempt. A converted house system is outside it. A large R-407C packaged unit or chiller may be inside it.
Is R-407C being phased out?
Partly. Under the AIM Act, HFC production and import are being phased down, which pushes supply down and price up over time. EPA's Technology Transitions rule sets a 700 GWP limit for new residential and light commercial air conditioning and heat pump systems from January 1, 2025. At about 1,774, R-407C cannot be used in those. What the rules restrict is new equipment and new supply, not repair: servicing an existing R-407C system stays legal.
What this means on the job
Read the label before you touch the gauges, set the manifold to R-407C, and charge by weight as liquid. Compare readings to the equipment manufacturer's targets rather than to R-22 habits. If someone has converted a system and not labeled it, identify the refrigerant before you trust any chart.
A deep vacuum after an oil change is good practice, not the Section 608 evacuation requirement, and the exam does test that difference. To check your recovery levels and blend handling, work through the Type II practice test and the EPA 608 study guide.
Frequently asked questions
What is R-407C refrigerant used for?
R-407C is used mainly in air conditioning, as a replacement for R-22 in converted equipment and in some chillers and packaged units designed for it. It was formulated to match R-22's capacity at similar operating conditions. It is not suited to low-temperature refrigeration, where R-404A and its replacements are used instead.
Is R-407C a drop-in replacement for R-22?
No. R-407C is often called a retrofit refrigerant, but converting means recovering the R-22, changing from mineral oil to polyol ester oil, replacing the drier and weighing in a new charge. The pressures are close to R-22, which is why the conversion is practical, but it is not a simple top-off.
Can you mix R-407C and R-22?
No. Mixing refrigerants produces an unknown blend with unpredictable pressures and performance, and it makes the contents impossible to recover, reclaim or recycle properly. Recover the old refrigerant completely before adding a different one, and label the system with what you installed.
What oil does R-407C use?
R-407C uses polyol ester (POE) oil. R-22 systems run mineral oil, which does not circulate properly with R-407C, so a retrofit needs the oil changed and flushed. Follow the compressor manufacturer's guidance on how much residual mineral oil is acceptable.
Is R-407C flammable?
No. R-407C is classified A1 by ASHRAE, meaning low toxicity and no flame propagation. Unlike R-32 or R-454B, which are A2L and mildly flammable, R-407C needs no flammability-specific handling, though normal cylinder and pressure safety still applies.
Do I need special certification to work on R-407C?
No. Type II or Universal Section 608 certification covers R-407C because it is a high-pressure refrigerant, and certification currently does not expire. There is no separate credential for blends. The exam does expect you to understand glide, liquid charging and recovery levels.
Sources
- 40 CFR 82.154 — Prohibitions
- 40 CFR 82.156 — Proper evacuation of refrigerant from appliances
- 40 CFR 82.157 — Appliance maintenance and leak repair
- 40 CFR 84.106 — Leak repair
- EPA, Leak Repair Requirements for Appliances Containing HFCs and Certain Substitutes (fact sheet, January 2026)
- EPA, Technology Transitions HFC Restrictions by Sector
- Arkema, Forane 407C Pressure Temperature Chart
Notice
Get EPA 608 is an independent study aid. It is not affiliated with, endorsed by, or approved by the U.S. Environmental Protection Agency, the ESCO Institute, Mainstream Engineering, or HVAC Excellence.