R-407C Refrigerant: Properties, Uses, R-22 Retrofit & Phase-Down Status

OK, let’s dispense with all this fluff and just do it. You’re likely scratching your head about R-407C. Perhaps you have overheard whispers about it, read it on a quote or found it while Googling to find out just what is happening with your old R-22 system. So, what is R-407C?

Plain and simple, R-407C is a blended refrigerant that came in as a contender when R-22 began its slow exit from the world of HVAC back around the full enforcement of the Montreal Protocol. Maybe think of it as a stunt double, meant to act much like R-22 but without the damaging chlorine that eats up ozone. It’s basically a blend of three distinct hydrofluorocarbon (HFC) refrigerants: R-32, R-125, and R-134a. The software was also intended to be an easy swap, especially for direct expansion (DX) air ACs, heat pumps and medium-temperature refrigeration systems. But, as with any “easy button,” there were some caveats.

Deciphering R-407C: What’s Behind the Mask?

Let’s break down this blend. It is a zeotropic mix consisting of 23% R-32, 25% R-125, and 52% R-134a by weight. Each component contributes to the mix: R-32 for heat capacity, R-125 stabilizes the blend, making it not flammable and R-134a reduces the overall pressure. Pretty clever, right?

Now, here’s the twist: R-407C is a zeotropic mixture. What does that mean for you? It has what is known as “temperature glide.” To understand why, consider boiling water and alcohol. Water boils at 100°C, alcohol at 78°C, so the alcohol will boil off first by a longish way, and the liquid left will be changed in composition. R-407C acts similarly. It has a glide of approximately 7.2°C (or 4.62 K). It’s this glide that means the temperature and composition of the refrigerant being turned into (or out of) a liquid in your system isn’t just one thing. This can be a little tricky with certain TXVs, and can impact such things a superheat settings though.

When you compare its numbers directly to R-22, raw stats-wise, R-407C gives you roughly comparable energy efficiency and cooling capacity. In your compressor you may see perhaps a bit higher discharge pressure and a bit lower discharge temperature. But here’s the catch: it’s performance can start to decline at lower temperatures, so it’s not as great of a fit for deep refrigeration, 20°F (-6.7°C) and lower, when you might want a product like R404A.

Here’s a quick cheat sheet on some key physical properties:

Note: There’s a slight variance in reported R-22 GWP values; some list 1700 while others indicate 1960. I’ve included the range here for full transparency.

Where does R-407C come off getting the rep? (Applications)

So where, then, did R-407C really catch a break? It’s used most commonly in DX air conditioning and heat pump systems. You’ll also see it in medium-temperature refrigeration systems. It was available for sale as both new equipment and as a service refrigerant for existing R-22 equipment.

I have seen it in action in such contexts as:

• Small devices like ice machines and refrigerators.
• Older Liebert units.
• Some of those are reusable chillers and building heat pumps.
• Ice/water coolers.

It was, and is, a good solution when a total replacement of the system was not feasible, especially if the piping is buried or hard to reach.

The ‘‘Why Isn’t It More Popular? Conundrum

Here is where the story gets thick. If R-407C was intended to be an R-22 substitute, why didn’t it take over? That’s a question that a lot of techs and shop owners ask.

Here’s the straight scoop on why it didn’t become the baby of the HVAC family:

1. The Oil Change Odyssey: It’s a Pain, Plain and Simple. This is the biggest hurdle. Older R-22 systems commonly use mineral oil or alkylbenzene oil. R-407C poses a need for polyol ester (POE) oil, however. Mineral oil and POE oil are like oil and water – they’re simply not compatible (immiscible). You need to remove nearly all the old oil; otherwise, you’ll suffer from extreme oil return issues. It is that the lubricant will not flow properly to the compressor, or not at all, causing it to run dry and eventually fail. To do it right, you’ll have to go through multiple oil changes and system flushes (usually three or four cycles) to get the residual mineral oil down to 5% or less of the total lubricant in the system. That’s a lot of manpower, time and money. Though IIRC some R-22 compressors made post-2007 may already You will probably lose my charge of the old dry system.

2. The Parts Swap Shuffle: More Hidden Expenses. It’s not just the oil. POE oil can be harsh on certain materials. It would be necessary to swap out all parts with Teflon seals, sight glasses, ball valves, caps/stems, as the POE oil can break down non-freaggin’ approved seals and you may inevitably leak gas. This also compounds the difficulties and expenses of the retrofit.

3. Performance Hiccups: Not the Perfect Fit in Every Scenario. Although R-407C can work perfectly well, it has its eccentricities:

• Efficiency: Some people write that it is “much less efficient” than R-22, especially in extreme heat. In colder climates, such in my state of Minnesota, it might even require you to step up the condenser fan horse power or ajust settings of fan cycle control because it “seems to not want to condense as easy as R-22“.
• Temperature Glide and TXVs: Remember this temperature glide I mentioned? It can make metering superheat settings “touchy,” especially with thermostatic expansion valves (TXVs). This can play havoc with efficiency, and in some cases, create customer complaints. It seems to be more effective with fixed orifice metering systems where the problem doesn’t seem to exist as much.
• Loss Of Capacity: There have been reports of the system losing capacity, especially at low evaporator temperatures. That could mean that your system will not cool as well with 448A as you did with R-22, or you will need more compressor swept volume to provide the same amount of heat transfer.

4. The Market Pick: R-410A Was the Clear Choice. Bad timing for R-407C. When the phaseout for R-22 began, another refrigerant — R-410A — became readily available for new systems. R-410A had a couple of advantages that made it the clear favorite for new equipment design:

• It’s Design Restrictions: It didn’t have the same ‘design restrictions’ to deal with that made retrofitting R-22 systems to R-407C so difficult.
• Similar Capacity: For new compressors, it provided a capacity similar to R-22.
• Oil Compatibility for New Systems: New R-410A systems were actually deigned for also with POE oil so there wasn’t this huge oil change challenge for new installations.
• Lack of Temperature Glide: There it’s hardly any temperature glide for R-410A, just 0.08 K, hence the design and operation of system gets clearer and easier than most of the other system whose glide are higher. Basically, when businesses had to change refrigerants for new equipment, R-410A was the more convenient, simpler route.

5. The Upsell Factor: New Systems = $$$. Let’s be real. Indeed, it’s frequently “much more profitable to upsell a customer” to a new, more efficient system than trying to force through a complex, costly retrofit, he said. When you are looking at a 20-year-old system, spending a lot of money to retrofit into something that might still have performance hiccups, it doesn’t make economic sense for the customer.

6. Leakage Concerns: R-407C is not prone to operating on a compressor’s discharge vapor leak (two-phase) and continuing to operate effectively.The refrigerant may be stratified in the evaporator and may give liquid or two phase refrigerant when three assignments are not made. The lower boiling point fractions can evaporate and the higher boiling point fractions practically are left behind (performant).

Environmental Standing & The Clock Is Ticking

So, R-407C is absolutely zero ozone-depleting (ODP=0). That’s a win. But, it remains an HFC that retains a GWP of about 1600-1774. Just to give you a sense: 1 kg of R-407C would cause global warming 1600-1774 times more than 1 kg of CO2 over a period of 100 years.

Although this GWP is a bit lower than R-22 (avl 1700-1960) and comparable to R-410A (GWP 1890 even)., when viewed thru the prism of today, as discussed it’s still quite high. High GWP HFCs such as R-407C are being phased out by the Kigali Amendment to the Montreal Protocol and F-Gas regulations globally as well.

In the USA, newly developed chillers using refrigerants such as R-407C became forbidden to import from January 1, 2024 onward. Canada then does the same as of 1 January 2025. That makes it a stop-gap solution at best — after all that, there’s no question that its days are numbered, and manufacturers are aggressively lobbying for even lower GWP options such as R-32 (GWP=675) and other next-generation refrigerants R-452B, R-454B, R-454C.

Safety & Handling: Don’t Skip This Part!

You have to give any refrigerant serious respect. Here’s what you need to know about R-407C.

• Flammability: It comes with a A1 (nonflammable) rating. That’s a good thing. But one of its ingredients, R-32, is slightly flammable. Moreover,whenever you need compressed air to leak test or anything else, never ever mix R407C with air under pressure as it turns flammable when exposed to high levels of air/oxygen under pressure or high temperatures.
• Toxicity It is “very low in toxicity” with an AEL of 1000 ppm. But breathing high concentrations can also result in nervous system depression (with symptoms such as dizziness, headache, confusion), and even cardiac sensitization, which can cause abnormal heart rhythms and be fatal in extreme cases. Do not, under any circumstances, give a patient with a sensitive heart more catecholamines in its adrenaline form; you will make the situation worse.
• Thermal Decomposition: When exposed to open flames or hot surfaces above 300-400C, the substance decomposes producing toxic, irritating gases such as hydrogen fluoride and carbonyl fluoride. Ventilate the work area at all times and recover the refrigerant before applying an open flame.
• Physical Dangers: It may cause frostbite on contact with skin or eyes in liquid form.
• ATTENTION: Must wear personal protective equipment: safety glasses and gloves. Ensure good ventilation. Never remove any cylinder safety device, or subject a cylinder to temperature above 52°C (125°F).
• Oil Compatibility (Again! ): I can’t say this enough. -407C is useable with only POE oils. You can’t run mineral oil and alkylbenzene oils, either; they will separate and not mix well at all, and you’ll lose oil return and could blow up your compressor.
• Material Compatibility: Most pure materials are compatible with R-407C (common metals, oils, lubricants, etc.), but not all plastics and elastomers (and sometimes O-rings and gaskets) are. Old elastomers in contact with R-22 may have absorbed differently and that changing to R-407C could result in new leaks needing replacement. And absolutely: Always consult your equipment’s owner’s manual.
• Desiccant Compatibility: Compatible with and will not absorb the R-32 component, XH-11 desiccant is recommended for use in filter/driers.

The R-22 to R-407C Retrofit Playbook

So if you’re the unlucky owner of an R-22 system and a complete replacement isn’t in the cards just yet, then retrofit to R-407C may be a temporary fix. It must be done with exquisite care, like a surgeon’s precise incision.

Here’s the lowdown, step by step:

1. Baseline Data: The first thing to do before you even starting working on an R-22 system is to collect data on the system operation (pressures, temperatures, superheat, subcooling, etc.). So, that gives you something to shoot for with R-407C.

2. The Big One, the Oil Swap: This is where it really gets real.

• You will have to pump out the old mineral or alkylbenzene oil from the compressor and other components of the system.
• Then, you add an appropriate POE oil.
• Here’s the trick: You’ll probably have to do this a few times (usually three or four). After each change, run the system with the R-22 (that’s still in there, and yes, you read that right, run it temporarily with R-22 ) in it for at least 8 hours (or for complex systems, 48-72 hours) to guarantee homogenous mixing of the oil and to flush out as much mineral oil as possible. The target is to reduce the mineral oil concentration to 5% or less of the over all lubricant.

3. Recover R-22: When the oil flush is complete, be sure to recover all R-22 from the system with a good recovery unit and cylinder. I would also recommend weighing the amount of R-22 that was removed as this will help you calculate the R-407C charge.

4. Filter/Drier Replace: This it not optional. Replace old filter/drier with a new one that is R-407C and POE oil compatible. Suggested is XH-11 drier.

5. Evacuate and Leak Test: Same as here, nothing special. Evacuate the system to a deep vacuum full vacuum ( 29.9″ Hg) to evacuate any air and non-condensables. Then, leak check thoroughly.

6. Charge with R-407C:

• Recover/R-407C should always be charged as a liquid. That temperature glide, remember? Charging as a vapor can also be some kind of fractionation, altering the composition of the blend and potentially screwing around with performance.
• You simply charge the system 90-95% by weight of the original R-22 charge.
• Put approximately 80% of the calculated charge on the high-pressure side of the refrigeration system (with the compressor not running). Once the pressure equalizes you can add the rest to the suction with the compressor running but keep liquid off of the compressor itself.

7. Start of Operation and Regulation: Turn on the equipment, wait for it to stabilize and gradually set the charge and controls. In some cases you may have to adjust your superheat settings on your TXV to account for the temperature glide.

8. Everything Labeled: Last, label system components so it’s clear that the system is now operating on R-407C and POE oil. This will be important for the service in the future.

It’s a process. And it’s not necessarily a smooth journey even then. Some systems are just not feasible for a retrofit. And if your system is still under warranty, you certainly should speak with the equipment or compressor manufacturer first, or you could void it.

Conclusion & The Road Ahead

So, there you have it. R-407C is a non-ozone depleting binary blend of HFC refrigerants R-32 and R-134a, and has been used as R-22 replacement in many air conditioning and medium temperature refrigeration systems. It delivered R-22 like performance but had its own set of issues, particularly the necessity to change from mineral oil to POE and the nuances of how to deal with its temperature glide.

In the end, even though R-407C carved out a market for itself, it never dominated as a lead R-22 alternative for new through-virtual-new equipment, primarily because R-410A and its simpler design needs for new-based new equipment were introduced. Moving forward, the industry is already moving beyond R-407C toward the use of low GWP refrigerants such as R-32 in place of higher GWP refrigerants such as R-407C (GWP: 1600-1774). Time is running out, with import bans now in place, or coming soon, in many areas.

If you have an existing system and you are retrofitting, it is important to know R-407C’s attributes, the detailed process, and the limitations of it. It’s a stopgap, a bridge, but not a final destination in the long march of refrigerants’ evolution. That’s why you need to keep up with all the changes in refrigerants, technology, and safety.

Here Are Your Burning Questions Answered (FAQ)

Here are a few questions you might be asking about R-407C:

Q1: Am I able to simply “plop” R-407C into my R-22 system without any other alterations? A1: No, that is a disaster waiting to happen. R-407C is often referred to as a “drop-in replacement” for R-22, but that’s misleading. The biggest step is replacing the lubricant in the system, commonly mineral oil to POE oil, which can sometimes take many flushes to remove a significant amount of the original oil. Otherwise you take the chance of having a compressor failure from lack of proper oil return.

Q2: Will R-407C perform as well as R-22 in my equipment? A2: In many applications, R-407C operates with comparable capacity and energy efficiency to R-22. Yet certain systems, particularly in warmer parts of the country, may see a perceived drop in performance or struggle to condense as well as R-22. TXV systems may also be “finicky” due to the temperature glide of R-407C and need to be dialed in.

Q3: Is R-407C flammable? A3: It is not (R-407C is an A1 which means nonflammable). But, it is important to realize that R-407C can be made flammable when mixed with a large percent of air or oxygen at higher pressures or temperatures when there is an ignition source. This is the reason you should never mix it with air to use as an aid in leak testing.

Q4: How long until R-407C is gone? Is it being phased out? A4: Yes, R-407C is in the process of being phased out globally, because of its high Global Warming Potential (GWP) under regulations like the Kigali Amendment and F-Gas? For instance, new technology chillers with the refrigerant R-407C couldn’t be imported into the USA from January 1st 2024 and Canada will adopt this rule from January 1st 2025. It will be around for some time for servicing of existing equipment but will no longer be produced and the industry is now transitioning to lower GWP alternatives.

Q5: What are the primary disadvantages of retrofitting with R-407C? A5: The primary disadvantages are the labour-intensive and expensive oil changes from mineral oil to POE involving numerous flushing operations. There is also the possibility of needing to replace some seals and parts. Furthermore, certain systems will suffer a small efficiency loss (especially in hottish climates) or side effects with TXV’s from its temperature glide. Taking those factors into account, it’s often more economical for homeowners to just go ahead and have their system replaced if their R-22 unit is old.

That’s the lowdown on R-407C. Cooling agent refrigerant with a history and a future in the world of HVAC.