Manitowoc MD0420A, Руководство техника

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96 Part Number 040005626 5/17
Refrigeration Components
HEAD PRESSURE CONTROL VALVE
Manitowoc remote systems require head pressure
control valves with special settings. Replace defective
head pressure control valves only with “original”
Manitowoc replacement parts.
Refrigerant Charge Verification
The correct amount of refrigerant (name plate charge)
is required to operate correctly at all ambient
conditions.
An ice machine with an overcharge or undercharge of
refrigerant may function properly at higher ambient
temperatures and fails at lower ambient temperatures.
Symptoms of incorrect refrigerant amount are:
• Works during the day and malfunctions at night,
and/or fails whenever the outdoor temperature
drops.
• A Safety limit is stored in control board memory.
Refrigerant loss and ambient temperature are directly
related to each other. As the ambient temperature
drops, more refrigerant is stored in the condenser.
When the refrigerant charge and ambient temperature
create an undercharge of refrigerant in the freeze
cycle, the receiver dip tube will lose it’s liquid seal.
Without liquid refrigerant to the TXV, the ice machine
fails to make a full sheet of ice in 60 minutes and a
safety limit #1 results.
NOTE: When a head pressure control valve is being
replaced or refrigerant charge is suspected, verify the
refrigerant charge is correct by recovering the
refrigerant, weighing and comparing to the nameplate
amount. Refer to Refrigerant Recovery/Evacuation”
for recovery procedures.