Manitowoc
Manitowoc Manitowoc
Other• Non-Manitowoc components in system• Improper water supply over evaporator refer to“Water System Checklist” on page 105.• Loss of heat transfer from tubing on back side ofevaporator• Restricted/plugged liquid line drier• Restricted/plugged tubing in suction side ofrefrigeration systemNOTE: Do not limit your diagnosis to only the itemslisted in the checklists.HOT GAS VALVEGeneralThe hot gas valve is an electrically operated valve thatopens when energized, and closes when deenergized.Normal OperationThe valve is de-energized (closed) during the freezecycle and energized (open) during the harvest cycle.The valve is positioned between the receiver and theevaporator and performs two functions:1. Prevents refrigerant from entering the evaporatorduring the freeze cycle.The hot gas valve is not used during the freezecycle. The hot gas valve is de-energized (closed)preventing refrigerant flow from the receiver intothe evaporator.2. Allows refrigerant vapor to enter the evaporator inthe harvest cycle.During the harvest cycle, the hot gas valve isenergized (open) allowing refrigerant gas from thedischarge line of the compressor to flow into theevaporator. The heat is absorbed by theevaporator and allows release of the ice slab.Exact pressures vary according to ambienttemperature. Harvest pressures can be found in the“Cycle Time/24 Hour Ice Production/RefrigerantPressure Charts” in this book.154 Part Number 80-01111-9 7/10
Hot Gas Valve AnalysisThe valve can fail in two positions:• Valve will not open in the harvest cycle.• Valve remains open during the freeze cycle.Valve Will Not Open in the Harvest CycleAlthough the circuit board has initiated a harvest cycle,the evaporator temperature remains unchanged fromthe freeze cycle.Valve Remains Open in the Freeze CycleSymptoms are dependent on the amount of leakage inthe freeze cycle. A small amount of leakage will causeincreased freeze cycle times. A large amount ofleakage will result in no ice produced.Use the following procedure and table to helpdetermine if a hot gas valve is remaining partially openduring the freeze cycle.1. Wait five minutes into the freeze cycle.2. Feel the inlet of the hot gas valve(s).ImportantFeeling the hot gas valve outlet or across the hotgas valve itself will not work for this comp arison.The h ot g as val ve o utlet i s on the suction sid e(cool refrigerant). It may be cool enough to toucheven if the valve is leaking.3. Feel the compressor discharge line.! WarningThe inlet of the hot gas valve and the compressordischarge line could be hot enough to burn yourhand. Just touch them momentarily.4. Compare the temperature of the inlet of the hotgas valves to the temperature of the compressordischarge line.Part Number 80-01111-9 7/10 155
- Page 104 and 105: INSTALLATION AND VISUAL INSPECTIONC
- Page 106 and 107: ICE FORMATION PATTERNEvaporator ice
- Page 108 and 109: SAFETY LIMIT FEATUREIn addition to
- Page 110 and 111: Safety Limit Notes• A safety limi
- Page 112 and 113: Safety Limit ChecklistThe following
- Page 114 and 115: Safety Limit #2Harvest time exceeds
- Page 116 and 117: Discharge Pressure High ChecklistIm
- Page 118 and 119: ProcedureStep1. Determine the ice m
- Page 120 and 121: Suction Pressure Low ChecklistImpro
- Page 122 and 123: Hot Gas Valve AnalysisThe valve can
- Page 124 and 125: FindingsThe inlet of the harvestval
- Page 126 and 127: DISCHARGE LINE TEMPERATURE ANALYSIS
- Page 128 and 129: REFRIGERATION COMPONENT DIAGNOSTICC
- Page 130 and 131: FINAL ANALYSISThe column with the h
- Page 132 and 133: Q130/Q170/Q210/Q270 Ice Machines On
- Page 134 and 135: QM20/QM30DIAGNOSING AN ICE MACHINET
- Page 136 and 137: QM30The QM30 ice machines have a ve
- Page 138 and 139: Ice Production CheckThe QM20/QM30 d
- Page 140 and 141: REFRIGERATION DIAGNOSTICSImportant:
- Page 142 and 143: 5. Install thermometer thermocouple
- Page 144 and 145: SM50DIAGNOSING AN ICE MACHINETHAT W
- Page 146 and 147: ICE QUALITY IS POOR — CUBES ARE S
- Page 148 and 149: ICE MACHINE RUNS AND NO ICE IS PROD
- Page 150 and 151: DISCHARGE PRESSURE HIGH CHECKLISTIm
- Page 152 and 153: ProcedureStep1. Determine the ice m
- Page 156 and 157: FindingsThe inlet of the harvestval
- Page 158 and 159: ADJUSTING CUBE WEIGHTThe cube weigh
- Page 160 and 161: Bin SwitchQM45/Q130/Q170/Q210/Q270F
- Page 162 and 163: Bin Switch Removal — QM45/Q1301.
- Page 164 and 165: Bin ThermostatQM20/QM30FunctionThe
- Page 166 and 167: SM50FunctionThe bin thermostat stop
- Page 168 and 169: Check Procedure! WarningHigh (line)
- Page 170 and 171: Temperature/Resistance ChartAs the
- Page 172 and 173: ON/OFF/WASH Toggle SwitchFUNCTIONTh
- Page 174 and 175: Ice Thickness ProbeQM45/Q130/Q170/Q
- Page 176 and 177: Compressor Electrical DiagnosticsTh
- Page 178 and 179: Fan Cycle ControlQM45/Q130/Q170/Q21
- Page 180 and 181: Filter-DriersLIQUID LINE FILTER DRI
- Page 182 and 183: REFRIGERANT RE-USE POLICYManitowoc
- Page 184 and 185: RECOVERY AND RECHARGING PROCEDURESQ
- Page 186 and 187: NOTE: Manifold gauges must be remov
- Page 188 and 189: ImportantManifold gau ges must be r
- Page 190 and 191: System Contamination CleanupGENERAL
- Page 192 and 193: MILD SYSTEM CONTAMINATION CLEANUPPR
- Page 194 and 195: REPLACING PRESSURE CONTROLS WITHOUT
- Page 196 and 197: Q270 Condenser Fan Motor Replacemen
- Page 198 and 199: MAX. 1300°F(700°C)SV30714. Apply
- Page 200 and 201: High Pressure Cutout (HPCO) Control
- Page 202 and 203: This Page Intentionally Left Blank2
Hot Gas Valve AnalysisThe valve can fail in two positions:• Valve will not open in the harvest cycle.• Valve remains open during the freeze cycle.Valve Will Not Open in the Harvest CycleAlthough the circuit board has initiated a harvest cycle,the evaporator temperature remains unchanged fromthe freeze cycle.Valve Remains Open in the Freeze CycleSymptoms are dependent on the amount of leakage inthe freeze cycle. A small amount of leakage will causeincreased freeze cycle times. A large amount ofleakage will result in no ice produced.Use the following procedure and table to helpdetermine if a hot gas valve is remaining partially openduring the freeze cycle.1. Wait five minutes into the freeze cycle.2. Feel the inlet of the hot gas valve(s).ImportantFeeling the hot gas valve outlet or across the hotgas valve itself will not work for this comp arison.The h ot g as val ve o utlet i s on the suction sid e(cool refrigerant). It may be cool enough to toucheven if the valve is leaking.3. Feel the compressor discharge line.! WarningThe inlet of the hot gas valve and the compressordischarge line could be hot enough to burn yourhand. Just touch them momentarily.4. Compare the temperature of the inlet of the hotgas valves to the temperature of the compressordischarge line.Part Number 80-01111-9 7/10 155