R-22

R-22's molecular structure (one carbon atom, one chlorine, two fluorines, one hydrogen) gives it lower vapor pressure than the smaller HFC molecules in R-410A. R-22 boils at −41°F at atmospheric pressure; R-32 boils at −61°F; R-125 boils at −55°F. The lower R-22 boiling point means lower saturation pressures at any operating temperature.

At a 95°F outdoor design ambient, an R-22 system runs about 181 PSIG saturation versus R-410A's 278 PSIG (CoolProp 7.2.0). On a 70°F bench-test condition the spread is 121 PSIG (R-22) versus 202 PSIG (R-410A). This is why R-22 service equipment runs the legacy 500 PSI manifold gauge standard — R-22 operating envelope simply doesn't need the 800 PSI rating R-410A demands [accamanualT].

The pressure-envelope difference is why R-22 to R-410A refrigerant-only retrofit is not feasible. R-22 equipment components (compressor housings, condenser tubing, expansion valves, service ports) are rated for R-22's pressures, not R-410A's. Trying to operate R-22 equipment with R-410A would over-pressurize multiple components beyond their design ratings.

R-22's chemical formula CHClF₂ includes one chlorine atom per molecule. When R-22 leaks to the atmosphere and rises to the stratosphere (15-50 km altitude), UV radiation breaks the chlorine-carbon bond. The freed chlorine atom catalyzes ozone destruction — a single chlorine atom can destroy thousands of ozone molecules before being removed from the atmosphere.

This chemistry is what gives R-22 its ozone-depletion potential of 0.055 [montrealprotocol]. The reference is R-11 (a CFC with ODP defined as 1.0); R-22 destroys ozone at about 5.5% the rate of R-11 per kilogram released. CFCs like R-11, R-12, and R-13 had ODP 1.0 or higher; HCFCs like R-22 and R-123 had ODP 0.01-0.06; HFCs like R-32, R-125, and R-134a have ODP 0 (no chlorine).

R-22's global warming potential is 1810 (IPCC AR5, 100-year horizon) [ipccar5]. This means a 1 kg release of R-22 traps 1,810 times more atmospheric heat over 100 years than 1 kg of CO₂. The figure is high — comparable to R-407C (1774) and R-410A (2088), all in the same HFC-era tier.

For US regulatory purposes, however, R-22's GWP is not the binding constraint. R-22 was phased out under the Montreal Protocol HCFC schedule for its ozone-depletion potential (0.055), implemented as 40 CFR Part 82 Subpart A [epacfr82]. The EPA AIM Act, which targets refrigerants based on GWP, applies only to HFCs — R-22 is an HCFC and is not subject to AIM Act provisions.

This regulatory distinction matters when comparing R-22's situation to that of R-410A. R-410A is phased down under AIM Act for GWP reasons; the threshold (700 GWP) sits below R-410A's 2088. R-22 had no such GWP-based cutoff — it was phased out for chlorine chemistry, full stop, and its still-considerable GWP burden continues to influence retrofit-vs-replace economics for the installed base.

R-22 was added to the Montreal Protocol's controlled substances list via the 1992 Copenhagen Amendment [montrealprotocol]. The US implementation through EPA's 40 CFR Part 82 Subpart A established a multi-stage HCFC phase-out:

• 1996 — Production cap established at consumption baseline
• 2003 — 35% reduction in production allocation
• 2010 — Ban on new equipment manufacturing using R-22 (existing equipment continued to be serviceable)
• 2015 — 90% reduction in production allocation
• 2020 — Complete ban on US virgin R-22 production and import [epacfr82]
• 2030 — Final Montreal Protocol HCFC phase-out (developed nations)

The 2020 production ban was the regulatory event that shifted R-22's economics. From 2020 forward, all R-22 used to service the installed base must come from reclaimed material — recovered from end-of-life equipment, processed back to AHRI 700 purity spec, and resold [ahri700]. Service costs have risen 8-15× from 2019 baseline as reclaim supply tightens.