In this troubleshooting situation, a technician has responded to a complaint of “not cooling” on a six-year-old R-410A split system that employs an up-flow gas furnace indoor air handler and a condensing unit that sits on the ground, and there is less than 20 feet of connecting tubing. An example of this piping configuration is shown in Figure One.
A factory installed molecular sieve filter-drier is located inside the condensing unit. Upon the technician’s arrival, no apparent electrical or air flow problem was found that would result in the lack of cooling capacity, necessitating a check of the refrigeration system. Connecting to the low side only, the result was a pressure reading that would be considered far below normal. Based on that information, the technician decided to add refrigerant.