HVACR service technicians using a checklist when servicing a troubled refrigeration system may wonder how the compressor discharge temperature can be so high when the condensing temperature is not. There could be several reasons why. In this article, we will examine two scenarios for a low-temperature, TXV/receiver refrigeration system using R-134a as the refrigerant. The service checklist in the first scenario is for a refrigeration system that has an undercharge of refrigerant.