Manitowoc Marine Q 1000, Service Technician'S Handbook

Page: 99 / 179

–89–
Procedure
Step
Example Using
QY0454A Model Ice Machine
1. Determine the ice
machine operating
conditions. Air temp. entering condenser:
90°F/32.2°C
Air temp. around ice machine:
80°F/26.7°C
Water temp. entering water fill valve:
70°F/21.1°C
2A. Refer to “Cycle Time” and
“Operating Pressure”
charts for ice machine
model being checked.
Using operating
conditions from step 1,
determine published
Freeze cycle time and
published Freeze cycle
suction pressure.
13.7-14.1 minutes
Published Freeze cycle time:
55-36 psig
Published Freeze cycle suction pressure:
2B. Compare the published
Freeze cycle time and
published Freeze cycle
suction pressure. Develop
a chart.
Published Freeze Cycle Time
(minutes)
Published Freeze Cycle Suction
Pressure (psig)
In the example, the proper suction pressure
should be approximately 44 psig at 7 minutes;
41 psig at 9 minutes; etc.
3. Perform an actual suction
pressure check at the
beginning, middle and end
of the Freeze cycle. Note
the times at which the
readings are taken. Manifold gauges were connected to the
example ice machine and suction pressure
readings taken as follows:
psig
Beginning of Freeze cycle: 59 (at 1 min.)
Middle of Freeze cycle:
48 (at 7 min.)
End of Freeze cycle: 40 (at 14 min.)
4. Compare the actual
Freeze cycle suction
pressure (step 3) to the
published Freeze cycle
time and pressure
comparison (step 2B).
Determine if the suction
pressure is high, low or
acceptable. In this example, the suction pressure is
considered high throughout the Freeze
cycle. It should have been:
Approximately 55 psig
(at 1 minute) – not 59
Approximately 44 psig
(at 7 minutes) – not 48
Approximately 36 psig
(at 14 minutes) – not 40
1 3 5 7 9 12 14
55 52 48 44 41 38 36