Originally Posted by T-Top
Hey Ttop I am not always right but I do know refrigerants.I have been to Emerson,Bristol, and Tecumseh Compressor Company's Train the trainer courses. These are special courses given to people such as myself so I can teach the courses to other professional HVAC people. I take this industry seriously because many people do not and that gives us all a bad name.
Installation of R-410A systems requires a few things that R-22 doesn't necessarily require. All R-410A systems have a liquid line filter-dryer included, which must be installed. Before and during brazing, nitrogen must be run through the line set and indoor coil. When using low pressure, it must be below 0.45 mmHg. Like mineral oil used with R22, POE (Polyol ester) oil absorbs moisture, but unlike mineral oil, POE oil breaks down in the presence of moisture to form acids. R-410A must be liquid charged. On a new installation, additional refrigerant should be added for every five foot section of liquid line after the first 15 feet (typical factory precharge). If a R-410A system is undercharged, one must carefully put liquid through the vapor line. Vapor charging R-410A will contaminate the system. Liquid charging will allow the ingredients to mix in the proper proportions. The operating pressures with R-410A are higher than R-22. Typical head pressure will be somewhere in the 275 to 375 psi range, while suction will be in the vicinity of 150 psi. All R-410A systems use an expansion valve at the indoor coil. If one has a universal coil (one that can use R-22 or R-410A) the valve must be installed and the piston removed. Coils designed for R-410A already have the expansion valve installed. When an R-410A system is serviced, the refrigerant must be recovered. This is important because of its high global warming potential. In many countries, it is illegal to discharge any refrigerant, including R-410A.
My entire life has been spent in this industry and since I am a old man that has been a long time.
One thing I try to do every day is to learn something about this industry since no one can know it all.