Part Number STH025 8/12 195Refrigeration ComponentsHEAD PRESSURE CONTROL VALVEManitowoc remote systems require head pressurecontrol valves with special settings. Replace defectivehead pressure control valves only with “original”Manitowoc replacement parts.Refrigerant Charge VerificationThe correct amount of refrigerant (name plate charge)is required to operate correctly at all ambientconditions.An ice machine with an overcharge or undercharge ofrefrigerant may function properly at higher ambienttemperatures 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 temperaturedrops.• A Safety limit is stored in control board memory.Refrigerant loss and ambient temperature are directlyrelated to each other. As the ambient temperaturedrops, more refrigerant is stored in the condenser.When the refrigerant charge and ambient temperaturecreate an undercharge of refrigerant in the freezecycle, the receiver dip tube will lose it’s liquid seal.Without liquid refrigerant to the TXV, the ice machinefails to make a full sheet of ice in 60 minutes and asafety limit #1 results.NOTE: When a head pressure control valve is beingreplaced or refrigerant charge is suspected, verify therefrigerant charge is correct by recovering therefrigerant, weighing and comparing to the nameplateamount. Refer to Refrigerant Recovery/Evacuation”page 207 for recovery procedures.
