Manitowoc b970 series, Technician'S Handbook

Page: 109 / 264

Part Number STH025 8/12 109
Freeze Sequence
3. Prechill
The compressor is on for 30 seconds (60 seconds
initial cycle) to lower the temperature of the
evaporator(s) before the water pump is energized. The
water fill valve will energize and remain on until water
touches the low and high water level probes.
4. Freeze
Water Pump
The water pump(s) energizes and water flows over the
evaporator. The water pump is energized throughout
the freeze cycle.
Water Inlet Valve
The water inlet valve energized in prechill and can
energize up to two times in the freeze cycle. The
control board will prevent the water fill valve from
energizing after two 6 minute water fill time limits.
After water contacts the low and high water probes the
water fill valve de-energizes. Ice builds on the
evaporator and the water level drops. When water
loses contact with the high water probe, the water fill
valve energizes until water contacts the high water
probe again.
Ice Thickness Probe
The freeze cycle continues until the six minute freeze
lock expires and enough ice has formed to send a
signal from the ice thickness probe to the control
board.
During the first 6 minutes of the freeze cycle the ice
thickness probe microphone samples ambient noise. 6
minutes into the freeze cycle 4 baseline readings are
recorded. Ice formation on the evaporator will change
the readings; when two of the four baseline readings
are exceeded a harvest cycle starts.