The Systems - Scotsman UC2024 Series Service Manual

UC2024 and UC2724 Service Manual

The Systems

Commercial cube ice machines must do several
things to supply the user with ice:
1. Determine when to make ice.
2. Produce a user acceptable quality form of cubed
ice.
3. Determine when the ice is ready for release.
4. Determine when the ice has been released.
5. Refill the sump with water.
6. Discharge extra water to dilute any mineral build
up.
7. Determine when to shut off.
Those seven requirements are taken care of by
the control system, water system and refrigeration
system.
Control System:
The components of this product's control system are
the controller, the evaporator thermistor, the ice plate
flap switch and the pressure controls.
The evaporator thermistor is attached to the suction
line, near the evaporator. As ice thickness increases,
the temperature of the suction line will decrease.
When it reaches a preset temperature, the resistance
of the thermistor will also be at a preset point. That
triggers a timer in the controller which finishes the
freeze cycle.
The ice sensing flap is normally up or open. A magnet
on the right end is positioned away from the plate
switch, signaling to the controller that ice is needed.
When the ice releases, it falls by gravity over the
ice sensing plate, closing the flap and causing the
magnet to pass by the plate switch. This terminates
the harvest cycle. If ice has built up in the bin enough
to cause the plate flap to remain depressed, the
magnet is now positioned next to the plate switch,
signaling that the bin is full and no ice is needed. Ice
making will stop.
There is no maximum freeze or harvest time. There
is minimum harvest time, based on the suction line
thermistor reaching a preset temperature. If, during
harvest, the ice has not released to trip the flap
switch, and the suction line thermistor has reached a
preset point, the harvest will continue until it times out.
After that the system returns to a freeze mode.
Water System:
The components of the water system are the inlet
water solenoid, the overflow standpipe, the water
distributor and the water pump.
Water enters the sump during the harvest cycle thru
the open inlet water solenoid valve. The inlet water
solenoid valve remains open for a fixed time, then
shuts off. That amount of time is enough to fill and
overfill the sump, the overfill amount dilutes the sump
water and keeps the machine from excessive mineral
build up.
The water pump circulates the water during the freeze
cycle. It forces water up to the spray bar, where it is
distributed evenly to flood the evaporator surface.
Water flows over the ice sensing plate, but goes into
the open plate door, and back into the sump.
Refrigeration System:
The components of the refrigeration system are the
compressor, condenser, thermostatic expansion valve
and the hot gas valve.
The refrigeration system has three modes: Freeze,
harvest and off. During freeze the compressor
is circulating refrigerant thru the condenser and
thermostatic expansion valve and into the evaporator.
During harvest the hot gas valve coil is energized,
opening a path to the inlet of the evaporator. This
forces hot gas into the evaporator, warming it up
enough to release the ice frozen to it. When the bin is
full, the system is off.
November 2019
Page 16