Installing and servicing A2L systems

Before you start

Training. Rheem’s servicing section says work on its R-454B units is for personnel trained by a training organization or manufacturer, with the competence documented by a certificate. Lennox: anyone installing, decommissioning or maintaining the unit “must be properly trained with A2L refrigerants.” This is on top of EPA Section 608 certification.

Tools. Carrier’s 50FE instructions: “All service equipment or components must be A2L refrigerant rated.” Rheem’s tool list (800 psig manifold and hoses, 400 psig recovery cylinders) is on the A2L refrigerants guide; machines and cylinders are on recovery machine compatibility.

The work area. Rheem, Trane and Lennox print near-identical rules before opening an A2L circuit:

• Check the area with a suitable refrigerant detector before and during work. The detector must be non-sparking, adequately sealed or intrinsically safe.
• Keep ignition sources, including smoking, away from where refrigerant could be released. Rheem calls for “No Smoking” signs.
• Have a dry powder or CO2 extinguisher at hand for hot work.
• Work in the open or with ventilation, and keep it running while you work.

Line sets: reuse or replace

Rheem’s (-)P17AY R-454B instructions are the strictest of the manuals reviewed:

• If an existing R-410A or R-22 line set is reused, it “must be purged and flushed with nitrogen before use. It is recommended to replace the lineset if possible.”
• “Lines must be cut when replacing R-410A or R-22 systems with a R-454B system.”
• If the line set stays, blow it out with nitrogen to remove as much mineral oil as possible and drain oil from low spots.
• The line set must be sized for the new unit. A liquid line filter drier is required; if the oil tests positive for acid, a suction line filter drier is mandatory.

Trane’s ODR-SVN003D installer’s guide asks you to verify that existing joints are brazed, not soldered, and that the lines are the right size and “free of leaks, acid, and oil.”

The indoor coil is a separate question. Rheem: an R-410A or R-22 coil “has not been evaluated for use with R-454B and may lack a refrigerant detection system.” Use an indoor unit approved for the outdoor unit.

Joints and piping

Rheem allows only brazed joints, welded joints, or mechanical joints using fittings listed to UL 207 on R-454B line sets, and the joints must comply with local building code. In the ICC required changes to the 2018 IMC, Table 1101.2 lists refrigeration fittings, “including press-connect, flared and threaded,” under UL 109 and UL 207. Trane: for mechanical connections, confirm a negative leak test.

Lennox and Trane add that piping must be protected from physical damage and that all field joints must be accessible for inspection before being covered or enclosed. The 2024 IMC text in the ICC A2L change document also covers A2L piping:

• 1109.3.1: copper, aluminum or steel tube in stud, joist or rafter spaces less than 1-1/2 in from the edge of the member needs steel shield plates at least 0.0575 in (No. 16 gage), extending 2 in beyond each side of the tube.
• 1109.2.7: refrigerant pipe outside the equipment space is identified with the refrigerant and safety group; for A2L the label adds “WARNING – Risk of Fire. Flammable Refrigerant.”

Brazing, pressure test and evacuation

The steps match R-410A practice; see nitrogen pressure testing and evacuation microns. A2L-specific points from the manuals:

• Nitrogen while brazing (Rheem, Trane). Trane gives purge times by line length and flow, for example 2 minutes at 15 cu ft/hr for runs under 50 ft. Trane also notes that A2L equipment has red-marked service ports and pipes.
• Test gas. IMC 1110.3 (2024 text) lists oxygen-free nitrogen, helium, argon, or nitrogen with a hydrogen or helium tracer, and bars oxygen, air and combustible gases. Rheem warns that oxygen “reacts violently with oil.”
• Test pressure. Rheem: nitrogen to 500 psig maximum, hold at least 15 minutes. Trane: indoor unit and line set to the maximum pressure on the nameplate for at least 60 minutes, outdoor unit isolated and never tested above 450 psig.
• Vacuum. Rheem: 500 microns, held at or below 500 for at least 15 minutes. Trane: pull to 350 microns; complete if it does not rise above 1,500 microns in 10 minutes. Rheem warns never to run the compressor in a vacuum.

Leak checking an A2L system

From the Rheem and Lennox service text:

• No halide torch “or any other detector using a naked flame.”
• Electronic detectors are allowed if they are not an ignition source and suit the refrigerant. They “shall be set at a percentage of the LFL of the refrigerant,” calibrated to the refrigerant, with “25 % maximum” confirmed, and calibrated in a refrigerant-free area.
• Bubble and fluorescent fluids are acceptable, but avoid detergents with chlorine, which can corrode the copper.
• Rheem: test field-made line set joints with an A2L-compatible detector sensitive to 0.2 oz/year (5 g/year) or better.

After evacuation and opening the valves, Rheem says to check all joints and piping with an A2L-compatible detector. If you find a leak, recover the refrigerant before repairing it.

Charging and labeling

Rheem: charge R-454B as liquid. Its charging rules for A2L add: keep hoses short, earth the system before charging, do not overfill, and label the system when charging is complete. The system is pressure-tested with purging gas before recharging, leak-tested after charging but before commissioning, and leak-tested again before leaving the site.

Write the total system charge (factory charge plus field charge) on the label next to the nameplate; Rheem and Trane both require it. IRC M1411.5 in the ICC 2021 IRC change document requires the installer’s contact information, the system charge and the refrigerant number on the manufacturer’s label. The total charge also decides the room area limits: see A2L charge limits.

Commissioning the leak detection system

• Trane: “All systems require Refrigerant Detection Systems.” The checkout list includes “Confirm Refrigerant Leak Detection system is operational” and “Confirm refrigerant quantity is marked on OD unit.”
• Lennox: the unit’s safety measures are electrically powered, so “the unit must be electrically powered at all times after installation, other than when servicing.” Replace refrigerant sensors only with those the manufacturer specifies.
• Carrier’s 50FE has a test button that runs the dissipation sequence for 60 seconds. Details and Carrier’s operating table are on the refrigerant detection systems page.

Opening a charged system for repair

If a leak needs brazing, Rheem, Trane and Lennox say to recover all the refrigerant, or isolate it with shutoff valves away from the leak. Lennox lists the sequence:

1. Safely remove refrigerant following local and national regulations.
2. Evacuate the circuit.
3. Purge the circuit with inert gas.
4. Evacuate.
5. Purge the circuit with inert gas.
6. Open the circuit.

Rheem’s version marks the purge and evacuation steps “optional for A2L” and adds continuous inert-gas flushing when a flame is used to open the circuit. Both say to purge with oxygen-free nitrogen, never compressed air or oxygen, and keep the vacuum pump outlet away from ignition sources. Recovery itself is covered in refrigerant recovery.

Electrical repairs and decommissioning

Rheem’s checks before electrical work: discharge capacitors safely to avoid sparking, keep live parts away while charging, recovering or purging, and confirm earth bonding. For sealed components, disconnect power first; if power is unavoidable, put a permanently operating leak detector at the most critical point. Replace sealed electrical components, and replace parts only to the manufacturer’s specification.

When decommissioning, Rheem says to recover into cylinders on a scale, fill to no more than 80% liquid volume, and label the equipment as decommissioned and emptied, dated and signed, with labels stating it contains flammable refrigerant.