Theory Of Operation; The Controls - KitchenAid KAR-13 Technical Education

ICE MAKING CONTROL
The freeze and harvest cycles are controlled
by a thermistor and an electronic control.
The electronic controller uses a thermistor that
is attached to the top of the evaporator to
monitor the evaporator temperature. When the
thermistor signals 28°F (–2°C), the control
begins to count down 10 minutes. The elec-
tronic control then switches the contacts of
relays X1 and X2, which stops the pump and
fan motors, and engerizes the hot gas and
water valves. This completes the freeze cycle,
and starts the harvest cycle.
HARVEST CONTROL
The ice cubes formed inside the ice making
cells are released by hot gas warming the
evaporator. When a small portion of the ice
melts on the ice making cells interior, the ice
drops down the ice guide into the storage bin.
When the evaporator is warmed further (to
approximately 45°F / 7°C), the thermistor sen-
ses the temperature rise, and the electronic
controller begins to count down 50 seconds.
The controller then switches the contacts of the
relays, which starts the pump and fan motors,
and de-energizes the hot gas and water valves.
This completes the harvest cycle, and starts
the freeze cycle. The harvest and freeze cycles
will continue until the bin is full of ice and the bin
thermostat is satisfied.

THEORY OF OPERATION

THE CONTROLS

At low temperature conditions where the har-
vest cycle exceeds 3 minutes, the water valve
will de-energize after 3 minutes.
At the initial start, or after a power failure, the
ice maker will begin in the harvest cycle, be-
cause the compressor is under a "no load"
condition (hot gas valve is energized). During
this time, any ice that is present on the evapo-
rator will be removed.
In the initial cycle at startup, or after shutdown
for bin control, water is supplied for 80 sec-
onds. The water valve de-energizes approxi-
mately 30 seconds after the freeze cycle starts.
NO ADJUSTMENT
The thermistor and electronic control are fac-
tory adjusted to produce constant ice all year,
and are not affected by changes in the ambient
and water temperatures. No adjustment is re-
quired for any frequency 50/60Hz or ambient
temperature from 45 to 100°F.
3-1
No Adjustment.
Controls Are Sealed.
If Seals Are Broken,
Replace Control.