Principles of Operation
Loading the cylinders one by one as required, increase compressor capacity. Similarly, unloading one or more cylinders, as and when required, can reduce the compressor capacity. Externally mounted solenoid valves, controlled by a signal from a remote device provide reliable response to system load.
In one of the methods for loading and unloading the cylinders, high pressure and low pressure refrigerant gas from the discharge or suction side of the compressor is used to actuate the unloader piston mechanism. An internal passage from suction and discharge chamber is connected to an internal passage in the compressor solenoid valve plate. Capacity control solenoid valves SVRF-3W are mounted on this plate.
During energized condition of the solenoid valve SVRF-3W; high-pressure gas is fed below the unloader piston, moving it up against unloader spring pressure plus the suction pressure (top portion of the piston is exposed to suction pressure). The unloader piston moves up, sealing the suction port seat. This allows the compression to take place and the cylinder gets loaded.
During the de-energized state, low-pressure gas from the suction side is admitted below the unloader piston. Since the top portion of this piston also is exposed to low pressure, the unloader spring pushes the piston away from the seat, thus unloading the cylinder.
Thus, solenoid valve type SVRF-3W is energized to load the compressor and de-energized to unload the compressor.