HVAC Direct Expansion with Top Hot-Gas Feed
In the evaporator shown in Fig. 10-10, when the defrost cycle is initiated, the hot gas is introduced through the hot-gas solenoid valve to the manifold. It then passes through the balancing glove valve and the pan coil to a check valve that prevents liquid crossover. From the check valve, hot gas is directed to the top of the evaporator. Here, it forces the refrigerant and accumulated oil from the relief regulator (valve A). This regulator has been de-energized to convert it to a relief regulator set at about 70 psig. It meters defrost condensate to the suction line and accumulator.