Manitowoc Indigo Series Technician's Handbook page 144

Analyzing Suction Pressure
The suction pressure gradually drops throughout the
freeze cycle. The actual suction pressure (and drop
rate) changes as the air and water temperature
entering the ice machine changes. These variables
also determine the freeze cycle times.
To analyze and identify the proper suction pressure
drop throughout the freeze cycle, compare the
published suction pressure to the published freeze
cycle time.
Analyze discharge pressure before analyzing
NOTE:
suction pressure. High or low discharge pressure may
be causing high or low suction pressure.
1. Determine the ice machine operating conditions:
Air temp. entering condenser______
Air temp. around ice machine______
Water temp. entering sump trough______
2. Refer to Operating Pressure table (starting on
page 221) for ice machine being checked.
Use the operating conditions determined in step 1
to find the published normal discharge pressures.
Freeze Cycle______
Harvest Cycle______
3. Perform an actual suction pressure check.
1 Minute into the
Freeze Cycle
Middle of Freeze Cycle
End of Freeze Cycle
4. Compare the actual suction pressure (step 3) with
the published suction pressure (step 2).
The suction pressure is normal when the
NOTE:
actual pressure falls within the published pressure
range for the ice machine's operating conditions. It is
normal for the suction pressure to be higher at the
beginning of the Freeze cycle (when load is greatest),
then drop throughout the Freeze cycle.
144
Freeze Cycle
psig (kPa)
__________
__________
__________
Part Number STH025 8/12