TM 10-8145-222-23
0003
REFRIGERATION UNIT CONTINUED
Compressor Unloader
The compressor is equipped with an unloader (Figure 8, Item 1) that is electronically controlled by the microprocessor.
Unloaders are used for capacity control. Capacity controlled cylinders are easily identified by the solenoid (Figure 8,
Item 2) which extends from the side of the cylinder head. When the unloader relay is energized, the solenoid valve
opens and cylinders unload. Unloaded cylinders operate with little or no pressure differential and consume little
power. A de-energized solenoid reloads cylinders.
NOTE
The unloader relay is locked in for a minimum of five minutes once it is energized due
to suction pressure.
Temperature Control. In low speed cooling or heating, unloader relays may energize to unload compressor banks.
Figure 8. Compressor Unloader.