Marine Q 1800 Ice Machine Service Manual - Manitowoc Ice

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Electrical SystemPTCR DIAGNOSTICSWhat is a PTCR?A PTCR (or Positive Temperature CoefficientResistor) is made from high-purity, semiconductingceramics.A PTCR is useful because of its resistance versustemperature characteristic. The PTCR has a lowresistance over a wide (low) temperature range, butupon reaching a certain higher temperature, itsresistance greatly increases, virtually stoppingcurrent flow. When the source of heat is removed,the PTCR returns to its initial base resistance.In severe duty cycles, it can be used to repeatedlyswitch (virtually stop) large currents at linevoltages.PTCR’s have been used for many years in millionsof HVAC applications. In place of using theconventional start relay/start capacitor, a simplePTCR provides the starting torque assistance toPSC (Permanent Split Capacitor) single-phasecompressors, which can equalize pressures beforestarting.Compressor Start SequencePTCR’s provide additional starting torque byincreasing the current in the auxiliary (start)winding during starting. The PTCR is wired acrossthe run capacitor (in series with the start winding).1. It is important for the refrigerant discharge andsuction pressures to be somewhat equalizedprior to the compressor starting. To assureequalization of pressures the hot gas valve (andHPR valve on remotes) will energize for 45seconds prior to compressor starting. The hotgas valve (and HPR valve on remotes) remainson for an additional 5 seconds while thecompressor is starting.2. When starting the compressor, the contactorcloses and the PTCR, which is at a lowresistance value, allows high starting current toflow in the start winding.3. The current passing through the PTCR causes itto rapidly heat up, and after approximately .25-1second it abruptly “switches” to a very highresistance, virtually stopping current flowthrough it.4. At this point the motor is up to speed and allcurrent going through the start winding will nowpass through the run capacitor.5. The PTCR remains hot and at a high resistanceas long as voltage remains on the circuit.6. It is important to provide time betweencompressor restarts to allow the PTCR to cooldown to near its initial temperature (lowresistance). When the contactor opens to stopthe compressor, the PTCR cools down to itsinitial low resistance and is again ready toprovide starting torque assistance. To assure thePTCR has cooled down, during an automaticshut-off, the Q model ice machines have a builtin3-minute off time before it can restart.14
Electrical SystemQ-Model Automatic Shut-Off and RestartWhen the storage bin is full at the end of a harvestcycle, the sheet of cubes fails to clear the watercurtain and will hold it open. After the water curtainis held open for 7 seconds, the ice machine shutsoff. To assure the PTCR has cooled, the icemachine remains off for 3 minutes before it canautomatically restart.The ice machine remains off until enough ice hasbeen removed from the storage bin to allow the iceto fall clear of the water curtain. As the watercurtain swings back to operating position, the binswitch closes and the ice machine restarts, providedthe three-minute delay period is complete.L1SV1506During Start-Up (First .25 - 1.0 Seconds)L1CONTACTORCONTACTSCRSCOMPRESSORCONTACTORCONTACTSCRSCOMPRESSORRUN CAPACITORRRPTCRRRUN CAPACITORPTCRRL2L2SV1507After Start-Up(Current Flows Through Run Capacitor)Troubleshooting PTCR’sWHY A GOOD PTCR MAY FAILTO START THE COMPRESSORThe PTCR must be cooled before attempting to startthe compressor, otherwise the high starting torquemay not last long enough.For example, if the PTCR is properly cooled, say60°F (15.6°C) when the compressor starts, it willtake .25 to 1.0 seconds before its temperaturereaches 260°F (126.6°C), and current flow isstopped.If the PTCR is still warm, say 160°F (71.1°C) whenthe compressor starts, it will take only .125 to .50seconds before its temperature reaches 260°F(126.6°C), and current flow is stopped. Thisdecreased time may be insufficient to start thecompressor.A good PTCR may be too hot to operate properly atstart-up because:• The ice machine’s 3-minute delay has beenoverridden. Opening and closing the servicedisconnect or cycling the toggle switch fromOFF to ICE will override the delay period.• The control box temperature is too high.Though rare, very high air temperatures (intensesunlight, etc.) can greatly increase thetemperature of the control box and its contents.This may require a longer off time to allow thePTCR to cool.• The compressor has short-cycled, or thecompressor overload has opened. Move thetoggle switch to OFF and allow the compressorand PTCR to cool.Continued on next page…15
Page 1: MarineQ 1800Ice MachineService Manu
Page 4 and 5: Table of ContentsRefrigeration Syst
Page 6 and 7: Electrical SystemWiring Diagram Seq
Page 8 and 9: Electrical SystemFreeze Sequence3.
Page 10 and 11: Electrical SystemHarvest Sequence5.
Page 12 and 13: Electrical System7. Automatic Shut-
Page 14 and 15: Electrical SystemQ1800 - 1 PHASECAU
Page 16 and 17: Electrical SystemCheck ProcedureWat
Page 20 and 21: Electrical SystemThere are other pr
Page 22 and 23: Electrical SystemELECTRONIC CONTROL
Page 24 and 25: Electrical SystemIce Thickness Prob
Page 26 and 27: Electrical SystemIce Machine Cycles
Page 28 and 29: Electrical SystemDIAGNOSING FREEZE
Page 30 and 31: Electrical SystemProblem: Water Wil
Page 32 and 33: Refrigeration SystemRefrigeration S
Page 34 and 35: Refrigeration SystemBEFORE BEGINNIN
Page 36 and 37: Refrigeration SystemICE FORMATION P
Page 38 and 39: Refrigeration SystemSAFETY LIMITSGe
Page 40 and 41: Refrigeration SystemSafety Limit #2
Page 42 and 43: Refrigeration SystemANALYZING DISCH
Page 44 and 45: Refrigeration SystemFreeze Cycle Su
Page 46 and 47: Refrigeration SystemQ Model Dual Ex
Page 48 and 49: Refrigeration SystemCycle Time/24 H
Page 50 and 51: Refrigeration SystemSelf-Contained
Page 52 and 53: Refrigeration SystemMild System Con
Page 54 and 55: Refrigeration SystemFIG. A - “PIN
Page 56 and 57: Refrigeration SystemREFRIGERANT DEF
Page 58 and 59: Refrigeration System Section 7HFC R
Page 60: Refrigeration System Section 756

Marine Q 1800 Ice Machine Service Manual - Manitowoc Ice

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