Discharge-Bypass Valves Operation

Discharge-bypass valves (DBV) respond to changes in downstream or suction pressure (see Fig. 11-37). When the pressure boiling point above the valve, the valve remains closed. As the suction pressure falls below the valve, the valve meets and begins to open. Like all modulating valves type, the size of the opening is proportional to the change in the variable is controlled. In this case, the variable suction pressure. As the suction pressure drops, the valve is opened next to the limit valve is reached. However, in normal applications, there is not enough pressure to change to open these valves to the limit of their stroke. The amount of pressure change is available from the point at which it is desirable that the valve is closed to the point where it should be open varies with the refrigerant boiling point. For this reason, DBVs calculated on the basis of the permissible temperature change of the evaporator from the closed position nominal opening. 6F (3.3C) change is considered to be normal for most applications, and is the basis of assessments of capacities.

..