Service
Condenser unit operation
The condensing unit is weatherproof and equipped to operate in ambient temperatures from – 20°F – 130°F
(– 29°C – 54.4°C). A dual pressure control provides compressor protection from excessive head pressures,
pumps the refrigeration system down and shuts the condensing unit off when the solenoid valve on the
evaporator unit is closed.
Low ambient operation: Reliable operation at low ambient temperature is achieved with a pumpdown cycle, a
crankcase heater and a head pressure control valve. As the ambient temperature falls and the head pressure
decreases the valve maintains a minimum head pressure of 215 psi by bypassing discharge gas around the
condenser to the receiver to increase the pressure at the condenser outlet. This backs liquid refrigerant up in the
condenser to reduce the area available for condensing which increases the head pressure to maintain the 215
psi set point. A check valve is installed in the liquid line between the receiver and the condenser to prevent liquid
migration from the receiver to the condenser during the off cycle. The crankcase heater works in conjunction with
a continuous pumpdown cycle to prevent accumulation of liquid refrigerant in the compressor oil during the off
c
This prevents compressor damage due to a flooded compressor start. The low pressure control will start the
condensing unit anytime the low side pressure rises above the 30 psi set point and pump the refrigerant out until
the pressure falls to 10 psi. The crankcase heater, which is energized whenever the condensing unit has power,
keeps the compressor oil warmer than the coldest location in the system. This minimizes off cycle refrigerant
migration. If power to the condensing unit is interrupted after the system is charged the compressor should not be
started unless the crankcase heater has been energized for at least four hours immediately prior to compressor
startup. However the compressor can safely be started during the refrigeration system charging process (without
the warm-up period) once sufficient refrigerant is in the system to maintain a positive pressure on the suction side
of the compressor.
Evaporator unit operation
Follett’s icemaker consists of four distinct functional systems:
1.
Refrigeration
system
2. Electrical control system
3. Water
system
4. Harvesting
system
These four systems work together to accomplish the production and harvesting of ice. A problem in any one
of these systems will result in improper operation of the entire ice production cycle. When troubleshooting the
icemaker, it is important to analyze the entire system operation to determine which system is not functioning
properly, then pinpoint the component within that system that is malfunctioning. Determine what corrective action
must be taken before making any adjustments or replacing any components.
The icemaking process
The Follett icemaker uses a stainless steel jacketed evaporator and operates on a continuous freezing cycle. Water is
supplied to the evaporator from the water reservoir where the water level is controlled by a float valve. This valve also
shuts off the water supply when the icemaker is not running.
When the icemaker is running, a layer of ice forms on the interior surface of the evaporator. This ice is continuously
removed by a slowly rotating (12 RPM) auger. The auger carries the ice upward into the cavity formed by the top
bearing housing and the compression loop, where it is compressed to remove excess water. When the ice reaches
the desired hardness it rotates within the cavity and is forced through a discharge port and compression nozzle and
into the ice transport tube. The discharge tube and compression nozzle are slightly restricted to further compress the
ice and produce the desired hardness. As the formation of ice continues, ice in the transport tube is pushed through
the tube to the storage compartment in the ice dispenser or ice storage bin.
A solid state control board located in the electrical box of the icemaker controls the normal operation of the icemaker
and monitors gearmotor torque. This control board will shut down the icemaker should an over-torque condition
occur. It is very important that you familiarize yourself with the operational sequences detailed in this manual before
attempting to service the icemaker.
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