Transport refrigeration system having means for enhancing the capacity of a heating cycle

A transport refrigeration system 10, and method of operating same, which includes a compressor 14, a receiver 26, an evaporator 42, an accumulator 44, and valve means 18 which initiates heating and cooling modes or cycles which utilize hot compressor gas. Instead of pressurizing receiver 26 at the start of a heating cycle, which traps refrigerant in condenser 24, the heating capacity of a heating cycle is enhanced by connecting the outlet of receiver 26 and the inlet of accumulator 44 in direct fluid flow communication during a heating cycle. Lower pressure in accumulator 44 allows liquid refrigerant in receiver 26 to be directed into accumulator 44, while permitting refrigerant in condenser 24 to drain into receiver 26, to make additional liquid refrigerant available during the heating cycle.