Swapping the Other Half of an R-410A Split Can Create a Prohibited New System
EPA says replacing a coil after a condensing unit, or the reverse, counts as a new system. North Carolina requires the existing A1 coil or air handler to go when an A2L outdoor unit arrives. Reclaimers processed 6.5 million pounds of R-410A in 2025, about 1.2 percent less than in 2024.
- "Mildly Flammable" Describes How an A2L Burns and Does Not Measure Ignition Odds
- A2L Rules Vary City to City Because Codes Adopt Safety Standards Edition by Edition
- R-454B and R-32 Change Cylinders, Leak Detectors and Ignition Checks on the Job
- Swapping the Other Half of an R-410A Split Can Create a Prohibited New System
- R-32's Record Abroad Rests on Small Splits and Thin Incident Data
A failed R-410A condensing unit can still go back on its existing coil. EPA treats replacing that coil a few years later as a different legal event. In the preamble to its May 26 Technology Transitions rule, the Environmental Protection Agency wrote that after a condensing unit swap, "the subsequent replacement of the indoor coil would be considered the installation of a new system," and it said the reverse order works the same way. The rule faces five petitions for review in the D.C. Circuit, led by No. 26-1168; AHRI and the Alliance for Responsible Atmospheric Policy told the court in August they were not seeking a stay.
UL 60335-2-40 and ASHRAE 15 are sold documents and were not reviewed for this article, so statements about listings below are as North Carolina's code office and the manufacturers describe them. On any job, the unit's instructions and the authority having jurisdiction govern.
Where a repair stops being a repair
Under 40 CFR 84.54(e), certain actions count as installing a system once it is charged to full charge. Two can reach a residential job: assembling a system for the first time from used or new components, and increasing the cooling capacity of an existing system. Outside supermarkets the capacity test has no tolerance, so an upsized R-410A condensing unit on an old coil falls under it on the face of the text.
Most commenters wanted R-410A service condensing units ended, calling them a loophole. EPA called them "the intended effect" of its 2023 rule and rejected the claim that they allow endless replacement. "The EPA has consistently stated that replacing all components over time constitutes the installation of a new system," the agency wrote.
The regulation also allows a new R-410A system where all specified components, a term covering condensing units, condensers, compressors, evaporator units and evaporators, were made in or imported into the U.S. before 2025. The preamble's coil passage cites no clause of 84.54(e) and does not mention that carve-out. On the plain text, replacing the other half would pass only if the new part and the part staying behind both predate 2025, and a later unit labeled for service would not qualify. EPA does not walk through that case.
EPA also addressed performance. In a system with one replaced half, it wrote, "the unmatched components may work though they were not specifically designed to operate with one another," with efficiency possibly below a designed match but better than the old pair.
The A1 half and the A2L half
EPA's 2021 SNAP listing allows R-454B and R-32 only in new equipment designed for them, and neither may be used as a retrofit refrigerant. North Carolina's Office of the State Fire Marshal reached partial changeouts on listing grounds in an interpretation dated June 6, 2025. "The existing A1 air handler or indoor evaporator coil is required to be replaced," it says of an A2L outdoor unit going in. It reaches the same result for an A2L indoor unit paired with an A1 outdoor unit that stays.
The office went further on coil-only jobs. "There is not an approved method for partial split-systems replacements that solely replace an A1 coil with an A2L coil while leaving the existing air handling enclosure in place," it wrote, because the listing covers the air handler as a whole. That interpretation applies under North Carolina's 2018 codes. A web search for comparable published interpretations from other states turned up none, which does not show that other jurisdictions would rule differently.
Manufacturers' wording varies. Bryant's 246S heat pump instructions say "For use with R-454B indoor units only." Rheem's RP17AY manual says an R-410A or R-22 coil "has not been evaluated for use with R-454B and may lack a refrigerant detection system," and that retrofitting an R-410A system "violates the product listing." Daikin's R-32 language is less direct than North Carolina's. Its DC3SQ manual says that if an existing coil stays while the refrigerant type changes, the installer should "ensure the indoor coil and metering device are compatible," and it recommends a new coil. Its DC6TE manual says that otherwise "the indoor coil must be replaced." Neither defines compatible, and both say that when a condensing unit or air handler is replaced, the system "must be manufacturer approved" and AHRI matched.
Dual-listed coils do not bridge the gap once they are in service. The Advanced Distributor Products (ADP) detection kit manual says the A1 or A2L flexibility "is applicable only for the first-time installation and not applicable for converting (retrofitting) existing coils in the field," even though the same manual calls the kit compatible with "any R-410A coil or AHU as outlined in the product installation instructions." Lennox says converting a refrigerant-versatile coil after initial installation "violates the safety agency mark and, therefore, voids the warranty."
| Job | Federal text or EPA preamble | Code office and manufacturers |
|---|---|---|
| Same-capacity R-410A condensing unit on the existing R-410A coil, first swap | Not a new system | North Carolina: the combination must be listed and meet the manufacturer's instructions. If they are silent, the contractor determines compatibility. |
| Coil replaced after the condensing unit, or the reverse | New system, subject to the 700 GWP limit and the pre-2025 component condition | Not addressed in the documents read |
| Larger R-410A condensing unit on the existing coil | Capacity increase counts as an installation | Not addressed in the documents read |
| A2L outdoor unit on an existing A1 coil or air handler | SNAP: new equipment only | North Carolina: prohibited. Rheem: coil not evaluated. Bryant: R-454B indoor units only. Daikin: compatibility check, with the system manufacturer approved and AHRI matched. |
| A2L indoor unit with an existing A1 outdoor unit | SNAP: new equipment only | North Carolina: prohibited |
| A2L coil in an existing air handler cabinet | Not addressed in the documents read | North Carolina: no approved method |
| Dual-listed coil, in service on R-410A, converted later | SNAP: no retrofit | ADP and Lennox: first installation only |
| New A2L coil on an existing gas furnace | Not addressed in the documents read | North Carolina: depends on the instructions, typically allowed. It expects most to require flame arrest for a continuous pilot in the same room, and likely detection wired to the furnace. Lennox's kit bars twinned furnaces. |
Manufacturers split on the old line set
The federal position is the most permissive. In its 2021 rule EPA concluded that "existing tubing can be inspected and if suitable re-used" with the system still treated as new. North Carolina says existing line sets are typically permitted if they meet the manufacturer's requirements. The manufacturers then split.
| Document | Position | Stated conditions |
|---|---|---|
| Rheem RP17AY (R-454B) | Must be cleaned or replaced, "recommended to replace the lineset if possible" | Purge and flush with nitrogen, correct sizing, liquid line drier, acid test of the oil with a suction drier if positive. Joints brazed, welded or mechanical fittings listed to UL 207. |
| Johnson Controls YC4 (R-454B); Bosch BOVA repeats it | Replace the piping, or if not practical, take precautions | Inspect for kinks and corrosion, find low spots, flush with a commercial kit, fit a suction drier and remove it after 50 hours of operation |
| Oxbox J5HP5, a Trane Technologies brand (R-454B) | "Not recommended" | If reused, correct size and length, free of leaks, acid and oil, joints brazed and not soldered |
| Daikin DC3SQ (R-32) | Reuse addressed, with a new coil recommended | Drain residual oil where possible, approved flushing agent recommended, then a nitrogen purge |
| Lennox transition guidance | Reuse not addressed. "Continue maintaining best practices for cleanliness and brazing" as with R-410A | Length and diameter differ by manufacturer |
On cleaning method, Rheem names nitrogen, while Johnson Controls and Daikin name a flush kit or agent. Their stated concerns differ too. Johnson Controls cites cross-contamination of oils and refrigerants in the piping, and Rheem, writing about the coil and not the line set, says an old coil "could also contain PVE or POE oil which is incompatible with the POE oil used in R-454B systems." Bryant adds that failures of mechanical or crimp line set fittings "would not be covered under the equipment limited warranty."
Detection commissioning tests the controls
Trane's coil guide puts the duty on the installer, who "must verify that the refrigerant leak detection system actuates all mitigating actions." It starts the test by shorting two pins on the mitigation board. The blower runs, zone dampers open, the compressor stops and connected ignition sources lose power, for about five minutes.
Other makers use a different trigger for a similar check. Lennox and ADP boards run a five-minute purge at power-up, then a Test button under a call for cooling should produce a flashing blue LED, blower on and compressor off. Under a heating call the burners should also go off, and both makers say installation is complete after both sequences pass. Johnson Controls has the installer disconnect the sensor wire or move a jumper during a Y call, confirm after 15 seconds that the compressor call has dropped with 24 VAC at G, reconnect, wait five minutes and repeat on a W call. For its own brands' furnaces, Daikin's R-32 coil manual requires the A2L function enabled on the furnace board and the furnace manual's verification step finished before commissioning.
The Trane, Lennox, ADP and Johnson Controls procedures show that the board and its outputs respond to a simulated signal. None of them, as written, exposes the sensor to refrigerant.
Whether detection applies at all can turn on the old line set. Lennox counts total charge as factory plus field-added refrigerant, line set included, and requires detection at 4 pounds or more of R-454B, adding that it "may be required" below that. Johnson Controls states the trigger as above 3.9 pounds. Lennox's ELKA air handler sheet lists 271 cfm of mitigation airflow and, at sea level, 149.9 square feet of minimum conditioned area for 10 pounds of charge, with the area multiplied by 1.18 at 6,560 feet. Lennox also warns that its board "has been tested with Lennox coils only."
What the warranty paper ties to the match
Bryant's R-454B certificate makes the match a condition of its Unit Replacement Limited Warranty. The outdoor unit "must be installed in combination with a matching indoor coil," certified and listed in the AHRI directory, and the supplied filter drier must be installed. The certificate also excludes "any cost to replace, refill or dispose of refrigerant." Rheem says a properly matched indoor section should be selected "to assure the outdoor unit warranty remains valid." Daikin's documents differ with each other: the DC6TE manual calls unmatched systems "strongly discouraged," and the coil manual says they are "not permitted."
An AHRI listing and a safety listing answer different questions. North Carolina's general partial-replacement interpretation says the code's listing requirement means marks such as UL or ETL, "but not AHRI, which is a rating."
Keeping the refrigerants apart
The 2025 cylinder shortage produced field shortcuts that manufacturers warned about in Contracting Business that June. "Then, the next guy coming along doesn't know what refrigerant he's taking out," said Jim VerShaw, Trane's chief engineer for residential HVAC and supply, describing R-410A put into R-454B equipment. Carrier's Nick Arch said "only the refrigerant listed on the unit nameplate should be used," and the magazine reported Carrier's position that R-454B and R-32 are not interchangeable.
The technical reasons offered do not all agree in degree. Jessica Wood of Honeywell's Solstice Advanced Materials said R-454B "has quite a high glide" and that "as you move product, it's going to lose its composition." Rheem's manual lists an atmospheric bubble point of minus 59.6 degrees F and a dew point of minus 58.0 degrees F, a spread of 1.6 degrees at that one condition.
In the recovery cylinder, Arkema's reclaim FAQ says to use a separate cylinder for each refrigerant because a mixture has "no value," and its listed exceptions, such as R-404A with R-507A, do not include R-410A with an A2L. It also warns that refrigerant trapped in hoses can cross-contaminate.
The tail in pounds
- 2022: 3,569,249 pounds
- 2023: 4,625,948 pounds
- 2024: 6,573,726 pounds
- 2025: 6,495,147 pounds
R-410A passed HCFC-22 as the most reclaimed refrigerant in EPA's table in 2024. The agency's page says total HFC reclamation rose about 10 percent in 2025 and names R-410A and HFC-134a as the main drivers of the year-over-year growth, but its spreadsheet shows R-410A slipping about 1.2 percent that year while HFC-134a rose from about 2.59 million to 2.96 million pounds.
Since Jan. 1, 2026, refrigerant sold as reclaimed may hold no more than 15 percent virgin material by weight, under 40 CFR 84.112. The rule's 2029 reclaimed-refrigerant service mandate names supermarket systems, refrigerated transport and automatic commercial ice makers, so residential R-410A service stays outside it. RMI authors, writing in ACHR News in May, cited estimates that reclaim was about 3 percent to 10 percent of U.S. HFC consumption as of 2022, and they reported no statistically significant differences in capacity or power between virgin and reclaimed refrigerant in a 3-ton split heat pump and a 5-ton rooftop unit.
EPA disagrees that repairs will push demand "beyond what can be met with virgin and reclaimed HFCs," while conceding prices may rise as the phasedown continues. Hudson Technologies, which sells reclaimed refrigerant, describes them as soft for now. On its second-quarter call, CEO Ken Gaglione put R-410A "in the $6 area" and blamed excess channel inventory plus illegal imports he had come to understand were "in the millions of pounds," an effect he called "hard to quantify."
R-454B's documented price history is mostly from 2025. Honeywell raised prices 15 percent in February and 8 percent in March, then announced a 42 percent surcharge and a $4-per-pound increase, ACHR News reported that April. The publication wrote that a cylinder could top $900 that summer, and by October HARDI's Alex Ayers said "the crisis is over," with prices elevated but falling. HARDI CEO Talbot Gee said in early 2026 that the year looked "more normal-ish." No current R-454B per-pound price from a primary document could be confirmed.
Why This Matters to Contractors
EPA says the R-22 phaseout informed its R-410A repair policy, and a commenter read that record the opposite way, reporting that more than 22,000 R-22 condensing units still sold in 2017 and estimating over 15 percent of the installed AC and heat pump base still runs on R-22. The agency took that same estimate as a sign of "a healthy" reclamation market, and its spreadsheet shows 4.58 million pounds of HCFC-22 reclaimed in 2025, five years after virgin R-22 ended. R-410A's supply ending is softer on paper. HFC allowances, which cover every regulated HFC and not R-410A alone, drop from 60 percent to 30 percent of baseline in 2029, 20 percent in 2034 and 15 percent in 2036, where EPA notes they continue indefinitely, yet on EPA's reading a system that took a service-labeled condensing unit has no R-410A option left when its coil fails, whatever the refrigerant costs that year.
Sources
- EPA, "Phasedown of Hydrofluorocarbons: Reconsideration of Certain Regulatory Requirements," 91 FR 31284, May 26, 2026. federalregister.gov
- Code of Federal Regulations, 40 CFR 84.54, current text. ecfr.gov
- Code of Federal Regulations, 40 CFR 84.52, definitions, current text. ecfr.gov
- Code of Federal Regulations, 40 CFR 84.112, reclamation, current text. ecfr.gov
- Code of Federal Regulations, 40 CFR 84.7, phasedown schedule, current text. ecfr.gov
- EPA, SNAP Rule 23 final rule, 86 FR 24444, May 6, 2021. federalregister.gov
- EPA, "Summary of Refrigerant Reclamation Trends." epa.gov
- EPA, "Section 608 Quantity Reclaimed 2000-2025," spreadsheet. epa.gov
- North Carolina Office of the State Fire Marshal, "Compatible/Properly Matched Partial Replacement of a Split System Heat Pump or Air Conditioner, A2L Refrigerant Considerations," June 6, 2025. ncosfm.gov
- North Carolina Office of the State Fire Marshal, "Compatible/Properly Matched Partial Replacement of a Split System Heat Pump or Air Conditioner," republished 2025. ncosfm.gov
- Rheem, RP17AY variable speed R-454B outdoor unit installation instructions. budgetheating.com
- Johnson Controls Ducted Systems, YC4 series R-454B outdoor split-system installation manual, 6411591-UIM-B-0824. yorknow.com
- Bosch, BOVA R-454B outdoor split-system installation manual, 6765108-UIM-A-0826. bosch-homecomfort.com
- Oxbox, J5HP5 R-454B heat pump installation and operation manual. tranetechnologies.com
- Trane, Installer's Guide, Cased Aluminum "Convertible" Coil, 18-AD45D1-1B-EN, Jan. 29, 2024. tranetechnologies.com
- Daikin Comfort, DC3SQ condensing unit installation and service reference, IM-IOD-4048B. daikincomfort.com
- Daikin Comfort, DC6TE condensing unit installation instructions, IM-IOD-1064B. daikincomfort.com
- Daikin Comfort, upflow/downflow coils installation instructions, IM-IO-4012C. daikincomfort.com
- Bryant, 246S single-stage heat pump installation instructions, II246S-02. shareddocs.com
- Bryant, Limited Warranty for Air Conditioner and Heat Pump Condensing Units with Puron Advance (R-454B) Refrigerant, edition 8/26. shareddocs.com
- Lennox, refrigerant detection system blower control board instructions, 508466-01. lennox.com
- Lennox, refrigerant detection system non-communicating control board instructions, 508426-01. lennox.com
- Lennox, refrigerant sensor replacement instructions for ELKA air handlers, 508747-01, March 2025. lennox.com
- Lennox, "Transitioning to Low GWP Refrigerants." lennoxpros.com
- Advanced Distributor Products, A2L Refrigerant Detection System Kit installation instructions. siglers.com
- Arkema, Forane reclaim program FAQ. arkema.com
- Nicole Krawcke, Contracting Business, "HVACR Leaders to Contractors: Don't Mix and Mismatch," June 12, 2025. contractingbusiness.com
- ACHR News, "Honeywell Announces 42% Surcharge on R-454B," April 17, 2025. achrnews.com
- ACHR News, "HARDI on R-454B: 'The Crisis Is Over,'" October 2025. achrnews.com
- ACHR News, "No New Refrigerant Transition, But Challenges Persist," March 30, 2026. achrnews.com
- Ankit Kalanki and Raghav Muralidharan, ACHR News, "Refrigerant Recovery Is a Revenue Opportunity," May 30, 2026. achrnews.com
- Motley Fool, Hudson Technologies second-quarter 2026 earnings call transcript. fool.com
- Motion to expedite, D.C. Circuit No. 26-1168, August 2026. carbon-pulse.com (PDF)
- ACHR News, "EPA's Revised Refrigerant Rule Draws Praise, Criticism and Lawsuits," Aug. 6, 2026. achrnews.com