Manitowoc J250 Service Manual page 99

Electrical System
Control Board
HARVEST INITIATION
(ICE THICKNESS PROBE)
Manitowoc's patented solid state electronic sensing
circuit assures consistent ice formation. It does not
rely on the refrigeration system (pressure), the
temperature of the evaporator, or timers.
The ice machine must be in the freeze cycle six
minutes prior to harvest cycle initiation. See "Freeze
Time Lock-In Feature" for details.
As the ice forms on the evaporator, water (not ice)
will contact the ice thickness probe. After the water
completes this circuit for six to ten continuous
seconds, a harvest sequence is initiated.
L.E.D. Lights
BIN SWITCH LIGHT
The light is on when the bin switch (water curtain) is
closed, and off when the bin switch is open.
This light functions any time power is supplied to the
ice machine, even when the toggle switch is in the
OFF or CLEAN position. This indicates the primary
power supply (line voltage) at the control board is
functioning, without having to take a voltage reading.
6-48
HARVEST/SAFETY LIMIT LIGHT
This light's primary function is to be on as water
contacts the ice thickness probe during the freeze
cycle and remain on throughout the entire harvest
cycle. The light will flicker as water splashes on the
probes.
The light's secondary function is to continuously
flash when the ice machine is shut off on a safety
limit, and to indicate which safety limit shut off the
ice machine.
CLEAN LIGHT
This light is only on the new style control board. It is
on whenever a SeCS or AuCS (cleaning) cycle is
in progress.
Freeze Time Lock-In Feature
This feature prevents the ice machine from short
cycling in and out of harvest.
The control board locks the ice machine in the freeze
cycle for six minutes. If water contacts the ice
thickness probe during these six minutes, the harvest
light will come on (to indicate that water is in contact
with the probes), but the ice machine will stay in the
freeze cycle. After the six minutes are up, a harvest
sequence is initiated.
To allow the service technician to initiate a harvest
cycle without delay, this feature is not used on the
first cycle after moving the toggle switch OFF and
back to ICE.
Section 6