Refrigerant Types: CFC, HCFC, HFC, HFO and Natural Refrigerants

Refrigerants are grouped by what is in the molecule. Chlorine is what matters for ozone depletion. CFCs and HCFCs contain chlorine and are ozone-depleting substances, known in the regulation as class I and class II substances. HFCs contain no chlorine and have an ozone depletion potential of zero (EPA: Test Topics).

The test topics expect you to place common refrigerants in the right family. You don't need chemical formulas: R-12 is a CFC, R-22 is an HCFC, and R-134a is an HFC.

Ozone depletion potential (ODP) compares a substance's effect on stratospheric ozone with the same mass of CFC-11, which is set at 1.0. EPA gives the ODPs of the common CFCs as 1 for CFC-11, CFC-12 and CFC-114, 0.8 for CFC-113 and 0.6 for CFC-115. HCFCs range from 0.01 to 0.1, and HFCs are zero. The Core test expects you to know the order: CFCs deplete more ozone than HCFCs, which deplete more than HFCs (EPA: Test Topics).

Global warming potential (GWP) measures how much a gas warms the climate compared with the same mass of carbon dioxide. A refrigerant can have zero ODP and still a high GWP, and EPA notes that some HFCs do. That is why HFCs are now regulated under the AIM Act. For example, the leak repair rules in 40 CFR Part 84 apply to HFC substitutes with a GWP greater than 53 (40 CFR 84.106(a)).

Section 608 sorts appliances by the refrigerant's liquid-phase saturation pressure at 104 °F. The class decides which certification you need and which evacuation level in Table 1 applies. The examples below are the ones the regulation itself gives.

The Montreal Protocol is the international treaty that controls the phaseout of production and use of ozone-depleting substances. In the United States, Title VI of the Clean Air Act carries it out. CFCs were phased out first. HCFCs are being phased out with the highest-ODP compounds going first (EPA: Test Topics). R-22, long the standard refrigerant in residential air conditioning, is an HCFC and part of that phaseout. The CFC and R-22 phaseout dates are Core test topics.

For the technician, the practical rules for existing R-22 equipment are about handling. You may recover R-22 and return it to the same appliance or to another appliance owned by the same person without reclaiming it (40 CFR 82.156(h)). If it goes to a different owner, it must first be reclaimed by an EPA-certified reclaimer (40 CFR 82.154(d)). The owner of a leaking R-22 appliance with 50 pounds or more may choose to retrofit or retire it instead of repairing it (40 CFR 82.157(c)). Retrofitting means converting an appliance to another refrigerant, and that may involve changing lubricants, gaskets, filters, driers, valves or O-rings (40 CFR 82.152).

Many modern refrigerants are blends of two or more components. ASHRAE numbering puts zeotropic blends in the 400 series, such as R-407C and R-410A, and azeotropic blends in the 500 series, such as R-500 and R-502. Appendix A to Subpart F lists them that way.

An azeotrope behaves like a single substance: it boils and condenses at one temperature for a given pressure. A zeotrope does not. Its components boil at different temperatures, so at a given pressure it starts to boil at one temperature (the bubble point) and finishes at a higher one (the dew point). The difference is called temperature glide.

Because the components behave differently, a zeotropic blend can leak unevenly. EPA's test topics call this fractionation: different components of a blend leak at different rates, which can change the makeup of what is left in the system. For the same reason, zeotropic blends are normally charged as a liquid, so the mix entering the system matches the cylinder.

EPA's Core topics stress that there are no true 'drop-in' replacements. Moving an appliance to a different refrigerant is a retrofit, and that may mean new lubricant, seals, filter-driers and other parts (40 CFR 82.152). Mixing refrigerants in one system or one recovery cylinder is a mistake: the mixture may be very hard or impossible to reclaim.

Lubricants are a big part of this. Many substitute refrigerants do not work with the oils used with CFCs and HCFCs, and CFCs and HCFCs do not work with many of the newer oils. The test topics give two pairings to remember: ester oils with R-134a, and alkylbenzene oils with HCFCs. Always follow the equipment and compressor manufacturer's oil specification.

The Type II topics add one more point: hydrocarbons are not approved for retrofits. Where propane or isobutane is used, it is in equipment designed for it, such as the end-uses listed below.

The venting prohibition in 40 CFR 82.154(a) covers CFCs, HCFCs and non-exempt substitutes such as HFCs. Some substitutes are exempt from the prohibition and from the rest of Subpart F, but only in the end-uses the rule lists. Outside those end-uses, they are covered like any other refrigerant.

• Carbon dioxide, nitrogen and water in any application.
• Ammonia in commercial or industrial process refrigeration, or in absorption units.
• Hydrocarbons in industrial process refrigeration that processes hydrocarbons.
• Propane (R-290) in listed equipment, including stand-alone retail food refrigerators and freezers, household refrigerators and freezers, self-contained room air conditioners, vending machines, self-contained ice machines and water coolers.
• Isobutane (R-600a) and R-441A in listed household and stand-alone retail food refrigeration and vending machines. R-441A is also exempt in self-contained room air conditioners and heat pumps.

Refrigerants also carry a safety class under ASHRAE Standard 34. The letter is toxicity: A is lower, B is higher. The number is flammability: 1 means no flame propagation, 2L is lower flammability, 2 is flammable and 3 is higher flammability. Familiar refrigerants such as R-22, R-134a and R-410A are A1. R-123 is B1, and EPA's Type III topics note that ASHRAE Standard 15 calls for an equipment-room refrigerant sensor for R-123 (EPA: Test Topics); current editions of Standard 15 require one for every refrigerant. Propane is A3.

A2L refrigerants, such as R-32 and R-454B, are mildly flammable and are now used in new comfort cooling equipment. Handle them according to the equipment manufacturer's instructions and the codes that apply where you work. For recovery, use equipment rated for them: recovery machines for flammable refrigerants are certified under appendix B4 of Subpart F, which draws on AHRI Standard 740 and UL 1963 Supplement SB (40 CFR 82.158(d)(3)). The 608 test topics themselves say little about A2Ls. Your manufacturer's training is the place for detailed procedures.