Manitowoc QD0202A, Руководство по обслуживанию

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Section 7 Refrigeration System
Part No. 80-1100-3
7-21
HARVEST VALVE TEMPERATURE CHECK
NOTE: This procedure requires checking both harvest
valves on dual expansion valve Q1300 and Q1800 ice
machines.
General
A harvest valve requires a critical orifice size. This
meters the amount of hot gas flowing into the evaporator
during the harvest cycle. If the orifice is even slightly too
large or too small, long harvest cycles will result.
A too-large orifice causes refrigerant to condense to
liquid in the evaporator during the harvest cycle. This
liquid will cause compressor damage. A too-small orifice
does not allow enough hot gas into the evaporator. This
causes low suction pressure, and insufficient heat for a
harvest cycle.
Refer to the Parts Manual for proper valve application. If
replacement is necessary, Use only “original” Manitowoc
replacement parts.
Harvest Valve Analysis
Symptoms of a harvest valve remaining partially open
during the freeze cycle can be similar to symptoms of
either an expansion valve or compressor problem. The
best way to diagnose a harvest valve is by using
Manitowoc’s Ice Machine Refrigeration System
Operational Analysis Table.
Use the following procedure and table to help determine
if a harvest valve is remaining partially open during the
freeze cycle.
1. Wait five minutes into the freeze cycle.
2. Feel the inlet of the harvest valve(s).
3. Feel the compressor discharge line.
4. Compare the temperature of the inlet of the harvest
valves to the temperature of the compressor
discharge line.
Important
Feeling the harvest valve outlet or across the
harvest valve itself will not work for this comparison.
The harvest valve outlet is on the suction side (cool
refrigerant). It may be cool enough to touch even if
the valve is leaking.
! Warning
The inlet of the harvest valve and the compressor
discharge line could be hot enough to burn your
hand. Just touch them momentarily.
Findings Comments
The inlet of the
harvest valve is cool
enough to touch and
the compressor
discharge line is hot. This is normal as the discharge line
should always be too hot to touch and
the harvestharvest valve inlet,
although too hot to touch during
harvest, should be cool enough to
touch after 5 minutes into the freeze
cycle.
The inlet of the
harvest valve is hot
and approaches the
temperature of a hot
compressor
discharge line. This is an indication something is
wrong, as the harvest valve inlet did
not cool down during the freeze cycle.
If the compressor dome is also entirely
hot, the problem is not a harvest valve
leaking, but rather something causing
the compressor (and the entire ice
machine) to get hot.
Both the inlet of the
harvest valve and
the compressor
discharge line are
cool enough to
touch. This is an indication something is
wrong, causing the compressor
discharge line to be cool to the touch.
This is not caused by a harvest valve
leaking.