Technicians with R-22 experience will need to become familiar with working with high and low side pressures that are much higher when using R-410A. A typical R-22 system operating normally with a head pressure of 260 psig at a 120-degree condensing temperature and a low side pressure of 76 psig at a 45-degree evaporator saturation temperature will find the equivalent pressures in a R-410A system to be much higher.
A normally operating R-410A system with the same condensing temperature of 120 degrees and a 45 degree evaporator saturation temperature will have a high side pressure of 418 psig and a low side pressure of 130 psig.
Although refrigerant 410A is a near-azeotrope and has a slight temperature glide, there is no need to correct for refrigerant dew point and bubble point differences. Superheat and sub cooling calculations can be calculated the same way we have always done with R-22 refrigerant. The only difference will be the higher pressure-temperature relationship when reading the temperature-pressure chart. The temperature glide for R-410A is only .3 degrees Fahrenheit and can be ignored and fractionation is not a concern.
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