Working With A2L Refrigerant

The HVAC industry is moving from Puron refrigerant to Puron Advance. This article, written by product experts at Behler-Young, explains a brief overview of some changes that will take place when transitioning to HFO A2L Refrigerants like R454B. First, read and follow all equipment manufacturers' installation and service instructions to ensure the safe operation of HFO approved equipment. All installation and service are to be performed by professionally trained service personnel only! All technicians working with CFCs, HCFCs, HFCs and HFO refrigerants are required by law to have proper EPA 608 certifications.

Why? In 1987, CFCs (R12) and HCFCs (R22) were slated to be phased out under the Montreal Protocol Agreement. These refrigerants had a high Ozone-Depleting Potential (ODP). New HFC refrigerants like R410A and R404A were adopted to replace them, as they had little or no ODP. However, these non-ODP refrigerants have been found to be greenhouse gases and have a high Global Warming Potential (GWP).

The next round of refrigerants is called HFOs or Hydrofluoroolefins, such as R454B. These refrigerants have a much lower GWP, less than seven hundred. They are slightly flammable, so they fall under a new classification, A2L, or mildly flammable.

What does A2L or Mildly Flammable mean?

A2L means that it is difficult to ignite, has relatively low energy release, and has a low flame spread rate. Most household objects, such as a toaster or space heater, will not ignite the refrigerant. Ignition, if possible, would require an open flame or other high-energy ignition source. Once ignited, the flame cannot normally be maintained once the ignition source has been removed. The flame spread is less than 0.5 MPH. Most people walk at 2.5 MPH or more. The Lower Explosive Limit, or LEL, is over 11%. LP gas has an LEL of 2.1% in comparison. In most cases, we will never get close to enough refrigerant in an entire system to reach the LEL.

The new A2L equipment will require a refrigerant detector or mitigation sensor located at the base of the evaporator. This will be connected to a Mitigation or Dilution board wired to the furnace or air handler. If the sensor detects more than 20% of the LEL, the control will shut the furnace or A/C off. Then, it will bring on the system blower to dissipate or dilute the refrigerant throughout the space. This dilution will keep it from getting close to its LEL. Once the levels reach a safe limit again, the equipment will come back on as needed.

All system components, including the condensing unit, evaporator coil, metering device, and all accessories, must be rated for use with A2L refrigerants. There will be no retrofitting to R454B from R410A.

Using Tools with R454B

Most of your current tools should work fine with R454B and R32. However, you will need to confirm that your vacuum pump, recovery machine, and leak detectors are compatible with A2Ls like R454B.  Check with the equipment manufacturer before using any existing tools with A2L refrigerants. The refrigerant tank will have Left-Handed (backward) threads and will require an adapter. Filter driers will need to be approved for use with A2L refrigerants. Unit service valves will have straight stubs to easily use crimp type fittings. Caution must be taken when using an open flame with A2L refrigerants.

New Procedures to Follow When Working with R454B

Field Service Procedures formerly recommended are not required. Follow the steps listed below when working with A2L refrigerant.

1. Recovery refrigerant to required EPA recovery levels.
2. Purge the system with Nitrogen.
3. Evacuate the entire system.
4. Purge the system with Nitrogen a second time. 
5. Evacuate again.
6. Open systems and make repairs using brazing and cutting. 
7. Pressure test and leak check the system. 
8. Evacuate the system to 500 Microns. 
9. Recharge using proper Superheat or Subcooling methods as appropriate.