Refrigeration System; Refrigeration System Diagnostics; General; Refrigeration System Operation - Manitowoc QR0670C Technician Manual

Refrigeration System

REFRIGERATION SYSTEM DIAGNOSTICS

General

Verify the water and electrical systems are functioning
properly before diagnosing the refrigeration system or
it's components.
A dirty evaporator increases the length of the harvest
cycle and will cause the ice machine to shut off on
safety limit #2. All Manitowoc Ice Machines must have
their evaporator(s) cleaned first, if a safety limit #2 is in
memory.

Refrigeration System Operation

FREEZE CYCLE
The compressor sends high pressure, high
temperature gas to the condenser.
Air-Cooled Models - Discharge pressure will exceed
the fan cycle control cut in set point and the condenser
fan motor(s) energizes. The condenser removes heat
and the refrigerant condenses to a high pressure
liquid. The head pressure control valve will modulate
to maintain the correct head pressure and refrigerant
temperature.
Water-Cooled Models - The head pressure control
valve modulates from the bypass position to the non-
bypass position as the head pressure exceeds its set
point. The condenser removes heat and the refrigerant
condenses to a high pressure liquid. The water
regulating valve will modulate to maintain the correct
head pressure and refrigerant temperature.
The refrigerant enters the ice machine head section
and is stored in the receiver. Liquid refrigerant leaves
the receiver through a dip tube and passes through the
line drier and liquid line solenoid valve. The refrigerant
then passes through the heat exchanger where the
liquid is sun-cooled before delivery to the TXV. The
liquid refrigerant passes through the expansion valve
orifice and enters the evaporator as a low pressure
saturated vapor. As the refrigerant changes to an all
vapor state, heat is absorbed from the evaporator. The
–123–