R-22 specified equipment makes up the largest portion of the current U.S. air conditioning residential installed base, and over the past few years the price of R-22 refrigerant has increased to the point where homeowners are starting to look for alternatives. Reasons for this search are typically tied around a system that has a leak, as refrigerant does not “wear out” or lose “potency” over time. Recently, this website has received several inquires about using R-410A to supplement this “loss of charge” situation amongst the R-22 install systems.
Can R-410A charge be added to “top off” an R-22 system?
The short answer “NO.”
To better understand this answer, let’s briefly take a look at each of these refrigerants. R-22, which is a HCFC (Hydrochlorofluorocarbon), is currently the most commonly found refrigerant in U.S. AC systems. ARI lists AC condition points as (45°F/130°F) for an R-22 (azeotropic) are listed as 297psig / 76psig. Service technicians use a PT (pressure/temperature) chart to understand these conditions and relate them back to a known pressure/temperature correlation. This means that a technician will use his manifold gauges (typically a “red’ and “blue” gauge set) to find the system pressures at a particular point, while the system is running. This pressure will then be used with the PT Chart to determine the temperature and chemical state of the refrigerant in that portion of the system. R-410A (zeotropic), which is an HFC (Hydrofluorocarbon), is listed under the same ARI condition points of (45°F/130°F) is 477pisg / 130pisg. When comparing the pressures of R-410A to that of R-22, R-410A is almost twice the pressure per the same temperature. Again, a service technician would also use this pressure/temperature correlation to determine the R-410A system conditions and the basis for making any adjustments.
Because each of these refrigerants has a known pressure/temperature point, which is determined using a known chemical manufacturers’ PT chart listing, mixing two different refrigerants with two completely different pressures, would produce a mixture of a new chemical blend without a known pressure/temperature correlation. In other words, what chart would a technician use to determine system conditions containing a mixture of the two different refrigerants? Along this same line, there are several other problems like mineral oil (use with R-22) and its lack of miscibility with R-410A refrigerant …but I think you get the point, and hopefully understand the answer a little better.