Part Number STH025 11/16 145
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.
NOTE: Analyze discharge pressure before analyzing
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
223) 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.
Freeze Cycle
psig (kPa)
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).
NOTE: The suction pressure is normal when the
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.
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