Manitowoc J-1300, Руководство по обслуживанию

Страница: 125 / 165

Section 7 Refrigeration System
7-20
ANALYZING SUCTION PRESSURE
DURING FREEZE CYCLE
The suction pressure gradually drops throughout the
freeze cycle. The actual suction pressure (and drop
rate) changes as the air and water temperatures
entering the ice machine change. This affects 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. “Operating Pressure” and “Freeze Cycle
Time” charts can be found later in this section.
NOTE: Analyze discharge pressure before analyzing
suction pressure. High or low discharge pressure may
be causing high or low suction pressure.
Procedure
Step Example Using JY604A Model Ice Machine
1. Determine the ice machine operating
conditions. Air temp. entering condenser:
Air temp. around ice machine:
Water temp. entering float valve:
90 ° F/32.2 ° C
80 ° F/26.7 ° C
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.
Published freeze cycle
time:
10.6 - 12.5 minutes
Published freeze cycle
suction pressure:
52-23 PSIG
Published Freeze Cycle Time (minutes)
2B. Compare the published freeze cycle time
and published freeze cycle suction
pressure. Develop a chart. 1 2 4 6 8 10 12
52 48 43 38 33 28 23
Published Freeze Cycle Suction Pressure (psig)
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. Beginning of freeze cycle:
Middle of freeze cycle:
End of freeze cycle:
48 PSIG at 4 minutes
42 PSIG at 8 minutes
28 PSIG at 12 minutes
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. Time Into
Freeze Cycle
4 minutes
8 minutes
12 minutes
Published
Pressure
43 PSIG
33 PSIG
23 PSIG
Actual
Pressure
48 PSIG
42 PSIG
28 PSIG
Result
High
High
High