How to Choose the Right Refrigerant for an Older Air Conditioner

By Get Freon Editorial Team · Last updated September 21, 2026

You do not choose a refrigerant for an older air conditioner. The equipment chose it, and your job is to work out which of a short list of legal, mechanically viable options that choice leaves you — then decide whether the one you pick is worth the labor it drags behind it.

For an R22 system the list has exactly three entries: recharge with R22 and change nothing; convert to a SNAP-listed retrofit blend and accept the lubricant, drier, seal, and charging work that specific blend requires; or recover the charge and quote a replacement. For an older R410A system the list has one entry — R410A — because no listed retrofit converts that equipment to anything else, and an A2L refrigerant needs equipment engineered for it. If the nameplate is missing or the charge is suspect, there is no selection decision at all yet: recover, identify, and start over.

Everything else in this article is about executing those branches correctly. That matters because the expensive failures on retrofit work are not wrong-refrigerant failures — they are right-refrigerant-wrong-procedure failures: oil that never got flushed, a drier left in place, a blend charged as vapor, a TXV never re-set.

Start With the Nameplate, Not the Catalog

The data plate on the outdoor unit or the rooftop's compressor compartment gives you the designation the system was built and charged for. That is the governing input, and it is the one most often skipped on an aging unit where the plate is faded, painted over, or reading through fifteen years of rust.

Two conditions make the plate unreliable, and both are common on older equipment:

The system was already retrofitted. A rooftop converted to a blend six years ago by another contractor may carry no indication of it beyond a peeling sticker. Retrofit work is supposed to be documented on the unit, but in practice it frequently is not.

The charge has been topped off with something else. A mixed charge cannot be identified by pressure-temperature behavior with any confidence, and every subsequent reading you take off it is meaningless.

Where either is plausible, the charge gets recovered and identified before any product selection happens. Recovering a mixed charge into a dedicated recovery cylinder is not a wasted hour — it is the only way to keep an unidentifiable mixture out of your reclaim stream and out of your next decision.

Can an Older AC Be Charged With What's Available Today?

Yes — with the caveat that "what's available" is not the same as "what's currently being manufactured."

U.S. production and import of R-22 ended on January 1, 2020, and servicing since then has drawn entirely on recovered, reclaimed, and previously produced stock, as EPA's HCFC phaseout guidance sets out. Nothing in that ended the legality of servicing an R22 system. An R22 unit may be repaired and recharged with R22 indefinitely, by a certified technician, for as long as supply exists and the equipment is worth the refrigerant.

So the honest answer to a customer asking whether their old unit can still be serviced is: yes, with the refrigerant it was built for, and the constraint is supply and cost rather than permission. What has changed is that the refrigerant is now a finite resource whose price behavior no longer tracks manufacturing cost — which is what makes the retrofit branch worth evaluating rather than dismissing.

The Three Branches an Older System Falls Into

Before comparing products, sort the job. The branch determines the scope of work, and the scope of work determines whether the refrigerant choice matters at all.

Branch one — R22 equipment worth keeping in service. Reasonable coil condition, no leak history you cannot explain, a compressor with life in it, and an owner who needs three to seven more seasons out of it. This branch has two live options and they are genuinely different jobs.

Branch two — R410A equipment. Serviceable with R410A and nothing else. Discussed in its own section below, because the questions customers ask about it are all based on a misunderstanding.

Branch three — equipment not worth another refrigerant purchase. A leaking evaporator on an out-of-warranty twenty-year-old unit with a compressor that ran undercharged for three seasons does not have a refrigerant question attached to it. Recovering the charge and quoting a replacement is the answer, and Get Freon's breakdown of when a recharge stops making sense against a replacement covers the economics of that call in more detail.

Option One: Keep the System on R22

The simplest path and, on a lot of jobs, the correct one.

What it costs you in labor: nothing beyond the repair itself. No oil work, no drier change beyond good practice, no TXV adjustment, no relabeling, no warranty conversation with the equipment manufacturer. Find the leak, fix it, verify the repair held, weigh in the charge.

What it costs you in product: more per pound than a current-production refrigerant, drawn from a supply that only shrinks. Get Freon's explanation of why refrigerant prices diverge so widely between models is the useful background when a facility contact questions the line item.

When it is clearly right: small charges, short remaining service life, single-repair situations, and any job where the added labor of a conversion would exceed the refrigerant savings. On a 6 lb residential split with four seasons left in it, a conversion is almost never worth the hours.

When it stops being right: large charges, a fleet of them, or a system you expect to keep for a decade. That is where the arithmetic starts favoring a one-time conversion.

Option Two: Convert to a SNAP-Listed Retrofit Blend

Under the Significant New Alternatives Policy program, EPA maintains the list of substitutes acceptable for retrofitting existing equipment in each end use. For residential and light commercial air conditioning and heat pumps, EPA's SNAP substitutes listing for this end use names the acceptable R-22 retrofit options, a sample of which appear below with their listed GWP values.

Designations and GWP values as listed by EPA's SNAP program for retrofit use in residential and light commercial air conditioning and heat pumps. The full listing includes additional blends and one option restricted to residential window units.

R407C sits alongside these as the long-established HFC conversion route, and it behaves differently enough from the mineral-oil-tolerant blends to be treated as its own path — which is the next section.

Two constraints apply to every entry on that list. SNAP acceptability is granted per end use, so a blend acceptable for retrofitting comfort cooling is not automatically acceptable in refrigeration; check the end use, not just the model. And all of these are HFC blends, which means their supply sits inside the AIM Act phasedown of HFC production and consumption described in EPA's frequently asked questions on the HFC phasedown. Converting an R22 system to a 2,700-GWP HFC blend solves a supply problem for this decade, not permanently.

The Lubricant Question Decides the Job Scope

This is the fork that separates a half-day conversion from a full day of flushing, and it is the single most useful thing to establish before you quote the work.

Blends that tolerate the existing oil

Some retrofit blends are formulated to return oil with the mineral or alkylbenzene lubricant already in the system. Chemours' retrofit guidelines for R438A state that in most cases no lubricant change is necessary, noting that "in many cases, systems converted to this refrigerant are operating with the same mineral oil or alkylbenzene lubricant that was used with the previous chlorofluorocarbon (CFC) or hydrochlorofluorocarbon (HCFC) refrigerant." The same R438A retrofit guidelines do call for adding POE — roughly 20% of the total oil charge — where the system has a liquid receiver or a known oil-return problem, and require it on screw compressors.

"No oil change in most cases" is not "no work." The same guidance directs you to change the filter drier for one rated for HFC service, to replace critical elastomeric seals because older seals can start leaking after conversion, and to charge at approximately 85% of the R-22 charge initially, trimming up as the system stabilizes.

Blends that require POE

R407C is the reference case, and its requirements are firm. The Chemours R-407C retrofit guidelines call for replacing mineral oil with POE and note that "three or four lubricant changes are usually sufficient to get the residual oil content in the POE down to 5% or less" — the target being residual mineral oil at roughly 5 wt% or below of total lubricant. Initial charge runs about 80% by weight of the original R-22 charge, high side first with the compressor off, the balance into the suction side while running.

Three or four oil changes on a rooftop with a long line set is real labor, and it is the number to carry into the quote. It is also why the compressor-replacement scenario is often where a conversion makes the most sense: if the compressor is coming out anyway, the oil work is already in the job. Get Freon's walkthrough of refrigerant, oil, and cleanup planning on an R22 compressor replacement covers how those two decisions interact.

The comparison in short form:

Requirements as published in the manufacturer's retrofit guidelines for each blend. Always work from the guidelines for the exact product in hand — these are representative, not interchangeable.

Glide, Charging, and Why Vapor Charging Ruins a Blend Conversion

Every blend on the retrofit list is zeotropic: its components boil at different temperatures, so liquid and vapor in the cylinder are not the same composition. Draw vapor and you pull the lighter component preferentially, leaving a cylinder — and a system — charged with something other than the blend you bought.

Both manufacturers state the rule without qualification. The R-407C guidance directs you to "remove liquid refrigerant from the cylinder to charge the unit." The R438A guidance specifies removal "as a liquid only from charging cylinder" because vapor composition differs from liquid composition in the container, and warns that charging liquid into the compressor "will cause serious irreversible damage." Liquid out of the cylinder, metered into the system correctly — not liquid slugged into the suction line.

Glide has two further consequences in the field. Superheat and subcooling readings must be taken against the blend's own pressure-temperature data, with the correct dew and bubble points, rather than an R22 chart; and a TXV that was set well for R22 typically needs its superheat re-set even when the valve itself stays. Skipping that adjustment is how a technically correct retrofit produces a system that runs but never quite performs.

Blend composition also shifts after a vapor leak, which is why a converted system that has leaked and been partially topped off is no longer reliably the blend on its label.

What a Retrofit Actually Changes in the Field

The full sequence, in the order the work happens:

1. Leak-test and repair first. Converting a leaking system wastes the new charge and guarantees a return trip. On equipment with a full charge of 50 lb or more, an exceeded leak rate also carries an affirmative repair obligation under EPA's leak repair requirements, with verification testing at the conclusion of the work.
2. Recover the existing charge into a dedicated cylinder, keeping recovered R22 separate from anything else.
3. Do the lubricant work the chosen blend requires — nothing, POE addition, or repeated flushes to the residual target.
4. Replace the filter drier with one rated for the replacement refrigerant.
5. Replace critical elastomeric seals, per the blend's guidance, before pressure returns to the system.
6. Pressure-test and evacuate to a deep vacuum that holds with the pump valved off.
7. Charge liquid only, starting at the blend's specified percentage of the original charge, and trim to the manufacturer's method.
8. Re-set the TXV superheat against the blend's own data.
9. Relabel the unit with the refrigerant and lubricant now in it, dated. The next technician on that roof — possibly you, in four years — depends on this step, and it is the one most often skipped.

What Happens With Older R410A Equipment

Every part of the retrofit conversation above applies to R22 systems. It does not transfer to R410A, and the questions customers ask here come from assuming it does.

There is no listed retrofit substitute that converts existing R410A equipment to a lower-GWP refrigerant. The A2L refrigerants now going into new equipment — R454B, R32 — are mildly flammable under the ASHRAE safety classification scheme documented in ASHRAE's refrigerant designations resource, and equipment must be engineered for that class: component selection, leak detection, ventilation provisions, and charge limits in certain applications. The International Code Council's tracking of EPA's Technology Transitions program and the A2L shift covers how that has reshaped new equipment rather than existing installs.

So an older R410A rooftop gets R410A. It remains fully legal to own, service, and recharge — the HFC restrictions govern what may be manufactured, not what may be maintained. The planning implication for a facility with a mixed fleet is simply that R410A is now the legacy refrigerant on the newer half of the fleet, and its supply sits under the same phasedown as the retrofit blends.

Why "Drop-In" Is a Sales Word

No refrigerant on the SNAP retrofit list is a drop-in, and the term should not survive into a quote or a customer conversation.

Every one of them changes something you must act on: the oil, the drier, the seals, the charging method, the metering device setting, the nameplate, or several of those at once. Capacity is close but not identical — the R-407C guidance puts relative cooling capacity at 98 to 106 percent of R-22 depending on conditions, with higher discharge pressures. "Close enough that the system works" is not the same as "nothing needs to change," and the difference is exactly where callbacks live.

The other reason to retire the phrase is liability. Telling an owner a conversion is a drop-in sets the expectation that performance and reliability will be identical, and it invites the follow-up question you do not want: why the invoice includes four hours of oil flushing. Describe it as a conversion, scope it honestly, and the conversation is straightforward.

Never Mix, and Never Top Off With Something Else

This holds regardless of which branch the job is on, and it is worth being explicit because the shortcut is tempting on a hot afternoon with the wrong cylinder on the truck.

A system takes the refrigerant it was designed or properly converted for, and nothing else. Both manufacturers' retrofit guidelines say it plainly — do not mix, and do not top off a CFC or HCFC charge with a replacement blend. The consequences are cumulative: a mixed charge cannot be accurately charged or diagnosed because its pressure-temperature behavior belongs to no published chart; it cannot be reclaimed, so it becomes a disposal problem; and depending on what was combined, it can produce pressures the components were never rated for.

Retrofits are system-specific engineering decisions covering oil compatibility, metering device sizing, seal materials, and component pressure ratings. A blend acceptable in one end use is not automatically acceptable in another, and a blend that worked on one rooftop is not thereby approved for the chiller next to it. Recovery, charging, and retrofit work all require appropriate EPA Section 608 certification.

Costing the Decision Across a Fleet

On a single unit the labor usually decides it. Across a portfolio — a property manager with eleven aging rooftops, a service company with a book of R22 customers — the comparison is worth laying out properly, because the answer is frequently different for different units in the same building.

Three inputs move a unit between rows. The charge size sets how much refrigerant cost a conversion actually avoids — the savings scale with pounds, the labor largely does not. The expected remaining life sets how many service events the conversion pays back over; below about three seasons it rarely does. And whether the system is already open matters more than either: a compressor changeout or a coil replacement absorbs most of the conversion labor, which is why the right time to convert a fleet unit is usually when something else has already failed on it.

Sourcing and Paperwork Before the Truck Leaves

Once the branch is chosen, the supply side is straightforward as long as it is settled before the appointment rather than during it.

Match the product to the decision, not to what is nearest on the shelf. A system staying on its original charge is served from a 30LB R22 refrigerant cylinder. A POE conversion on light commercial comfort cooling typically runs on the 23/25/52 HFC-32 / HFC-125 / HFC-134a blend supplied as a 25LB R407C refrigerant cylinder. Newer legacy equipment stays on a 25LB R410A refrigerant cylinder. When you are planning across a mixed fleet and need to compare refrigerant options and confirm available cylinder sizes before ordering, the full refrigerant lineup at Get Freon shows the models side by side.

Two pieces of housekeeping are worth doing at order time rather than at the end of the job. Confirm product identity and documentation on arrival — the checks in Get Freon's guide to verifying refrigerant product identity and documentation when ordering online apply to conversion blends as much as to R22. And if a job needs paperwork in hand before the crew mobilizes, Support@GetFreon.com handles order and documentation questions.

Then bring the exact blend's retrofit guidelines to the site. Charge percentages, oil requirements, and superheat guidance differ between products that look interchangeable on a shelf, and the guidelines for the product in hand are the only authority on the procedure.

Frequently Asked Questions

What refrigerant does my old AC use?
The data plate on the outdoor unit or compressor compartment states it. On aging equipment, treat the plate as a starting point rather than proof — the unit may have been converted, or topped off with something else, and either possibility means recovering and identifying the charge before proceeding.

Is there a drop-in replacement for R22?
No. Several SNAP-listed blends are acceptable for retrofitting R22 comfort-cooling equipment, and each one requires specific work — lubricant handling, a new drier, seal replacement, liquid-only charging, and a superheat adjustment. The term "drop-in" misrepresents all of them.

Can you replace or mix AC refrigerants?
Replace, yes, through a documented retrofit to a blend listed for that end use. Mix, no. A combined charge cannot be charged accurately, cannot be diagnosed against any published chart, and cannot be reclaimed.

Do I have to change the oil to retrofit an R22 system?
It depends entirely on the blend. R407C requires a POE conversion with repeated flushes until residual mineral oil is down to roughly 5% of the lubricant charge. R438A retains the existing mineral or alkylbenzene oil in most cases, with POE added in defined situations such as systems with liquid receivers or screw compressors.

Why does a blend have to be charged as a liquid?
Because the components boil at different temperatures, cylinder vapor and cylinder liquid are not the same composition. Vapor charging transfers the lighter component preferentially and leaves both the cylinder and the system holding something other than the specified blend.

Can an older R410A system be converted to R454B or R32?
No. There is no listed retrofit that converts existing R410A equipment, and A2L refrigerants require equipment designed for their safety class — component selection, detection, ventilation, and charge limits. An older R410A system is serviced with R410A.

Does retrofitting affect the equipment warranty?
It can, and the manufacturer's retrofit guidance itself advises contacting the equipment manufacturer about warranty implications before converting. On equipment still under any coverage, that call happens before the quote goes out.

Is a lower-GWP retrofit blend a permanent solution?
No. The listed R22 retrofit blends are HFCs, and their production and consumption sit under the AIM Act phasedown. A conversion buys a decade of serviceability on equipment worth keeping; it does not move the system onto the long-term platform.

The Decision, In One Line

The nameplate tells you what the options are; the lubricant requirement tells you what the job costs; the remaining life of the equipment tells you whether to do it at all.

An older air conditioner in reasonable condition with a large charge and several seasons ahead of it is a good candidate for a documented conversion, particularly if something else on it has already failed and the system is open. The same unit with a leaking coil, high compressor hours, and a small charge is a replacement quote with a recovery step in front of it. Either way, the refrigerant is the last thing you decide, not the first.