Controller - Scotsman UC2024 Series Service Manual

UC2024 and UC2724 Service Manual

Controller

The controller is a computer, a computer that has
sensors and relays.
The evaporator thermistor provides electrical
resistance readings to the controller.
The sump water thermistor also provides resistance
readings to the controller.
There are relays for the compressor contactor coil, the
water pump, the inlet water solenoid valve and the hot
gas valve.
At start up, the inlet water valve and hot gas valve are
energized for a set time, after which the compressor
contactor is energized. After a few seconds more, the
hot gas valve and inlet water valves are de-energized
and remain closed until harvest.
When the reservoir water temperature falls to a preset
point, the water pump will shut off for 30 seconds.
This is the anti-slush period.
During Freeze or Harvest the temperature of the
suction line thermistor will change, eventually
reaching a setpoint. At that time the Timer light will
switch on, indicating that the suction line thermistor's
resistance is at the setpoint, which is very near to the
end of the cycle.
Restarts
Power Interruption:
An automatic restart process occurs after power is
reconnected. The Anti-Slush light will be on. After a 90
second delay, the inlet water valve and hot gas valves
are energized, and 15 seconds later the compressor
starts. No lights will be on. The inlet water and hot gas
valves will be on for 90 seconds. After they shut off
the water pump starts and normal ice making begins.
Water Interruption:
There is no shut off for a water interruption unless
the model is water cooled. Water cooled models
that experience a water interruption will shut the
compressor off because the high pressure cut out
opens. After a significant amount of time and after the
water supply has been restored, the high pressure cut
out will close, and the compressor restarts.
Air cooled operation without water will, of course, yield
no ice. The freeze cycles will be short and harvest
timed.
Load Tables
Stand By
Compressor
Fan motor
Hot gas valve
Inlet water valve
Water pump
Controller
Start Up
Compressor
Fan motor
Hot gas valve
Inlet water valve x
Water pump
Controller
Freeze
Compressor
Fan motor
Hot gas valve
Inlet water valve
Water pump
Controller
Harvest
Compressor
Fan motor
Hot gas valve
Inlet water valve x
Water pump
Controller
November 2019
Page 20
On Off
x
x
x
x
x
x
On Off
x
x
x
x
x
On Off
x
x Off if pressure
low
x
x
x
x
On Off
x
x
x
x
x