CSZ ZP 16, Installation, Operation & Maintenance Manual, Page: 39 / 88

GENERAL DESCRIPTION
Page 2-23
SINGLE STAGE CONTROL SYSTEM
(Refer to Refrigeration Diagram in Drawing Section)
Mode: Normal cooling/heating
When there is call for cooling the R-404A liquid line solenoid (2-SOL), and the Liquid Injection Solenoid (8-
SOL) energize, the R-404A compressor turns on. High pressure switch (1 PS) will turn off the compressor if
a high discharge pressure is reached. Contact Cincinnati Sub-Zero’s service department if this occurs. The
high pressure switch automatically resets. When there is a call for cooling 2-SOL is energized. When the
chamber is near the set point the controller begins to cycle 2-SOL on and off. At the same time the R-404A
hot gas by-pass solenoid (9-SOL) is cycling on and off opposite of 2-SOL. If the controller does not call for
cooling for ninety seconds the refrigeration system will turn off. For heating, solenoid (2-SOL) is de-energized
and the heaters are activated.
Mode: Humidity
In humidity mode, the system starts in the same manner as above with the following differences:
When Dehumidi fi cation is called for, Solenoid H-11 SOL is energized. This allows refrigerant to fl ow in the
humidity loop.
When humidity is called for, Solenoid H-11 SOL is de-energized.
For Dry Bulb Temperature cooling in humidity mode, solenoid H-2 SOL is energized. This allows refrigerant to
fl ow through the R-404A humidity dry bulb T.E.V. which has tighter temperature control.
For Dry Bulb Temperature heating, solenoid H-2 SOL is de-energized and the heaters are activated.