Manitowoc Ice CM MODEL STH003 - Manual (Page 50)

50
PROCEDURE
Step
.
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.
19.1 - 21.7 minutes
Published freeze cycle time:
20-3 PSIG
Published freeze cycle
suction pressure:
Published Freeze Cycle Time
(minutes)
2B. Compare the published
freeze cycle time and
published freeze cycle
suction pressure. Develop a
chart. 1 5 10 15 20
20 16 12 8 3
Published Freeze Cycle Suction
Pressure (psig)
In the example, the proper suction
Pressure should be approximately 16
PSIG at 5 minutes; 12 PSIG at 10
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:
30 (at 1 min.)
Middle of freeze cycle:
22 (at 10 min.)
End of freeze cycle:
8 (at 20 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 20 PSIG
(at 1 minute) – not 30
Approximately 12 PSIG
(at 10 minutes) – not 22
Approximately – 3 PSIG
(at 20 minutes) – not 8