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Hoshizaki KM-251BAH, Service Manual

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Hoshizaki KM-251BAH Service Manual Download Page 10

10

C. Control Board

• A HOSHIZAKI exclusive solid-state control is employed in the KM-251BAH Self-

Contained Crescent Cuber.

• All models are pretested and factory-adjusted.

CAUTION

1. Fragile, handle very carefully.
2. A control board contains integrated circuits, which are susceptible to failure 

due to static discharge. It is especially important to touch the metal part of 
the unit when handling or replacing the board.

3. Do not touch the electronic devices on the board or the back of the board to 

prevent damage to the board.

4. Do not change wiring and connections. Do not misconnect K3, K4 and K5, 

because the same connector is used for the thermistor, float switch and 
mechanical bin control.

5. Always replace the whole board assembly if it goes bad.
6. Do not short out power supply to test for voltage.

Summary of Contents for KM-251BAH

Page 1: ...1 Hoshizaki A Superior Degree of Reliability www hoshizaki com Model KM 251BAH Self Contained Crescent Cuber Hoshizaki America Inc Number 73140 Issued 9 15 2006 SERVICE MANUAL ...

Page 2: ...ions or concerns which have not been satisfactorily addressed please call write or send an e mail message to the HOSHIZAKI Technical Support Department HOSHIZAKI AMERICA INC 618 Highway 74 South Peachtree City GA 30269 Attn HOSHIZAKI Technical Support Department Phone 1 800 233 1940 Technical Service 770 487 2331 Fax 1 800 843 1056 770 487 3360 E mail technicalsupport hoshizaki com Web Site www ho...

Page 3: ...minutes 12 b Harvest Backup Timer and Freeze Timer 12 c High Temperature Safety 12 d Low Water Safety 12 e High Voltage and Low Voltage Cut outs 12 f LED Lights and Audible Alarm Safeties 13 3 Controls and Adjustments 14 a Default Dip Switch Settings 14 b Harvest Control Thermistor 14 c Harvest Timer S4 dip switch 1 2 15 d S4 dip switch 3 4 5 6 7 8 15 e Freeze Timer S4 dip switch 9 10 15 f Float S...

Page 4: ...placement of Expansion Valve 32 F Removal and Replacement of Hot Gas Valve 33 G Removal and Replacement of Evaporator 34 H Removal and Replacement of Air Cooled Condenser 34 I Removal and Replacement of Thermistor 35 J Removal and Replacement of Fan Motor 36 K Removal and Replacement of Freeze or Harvest Water Valve 36 L Removal and Replacement of Wash Valve 37 M Removal and Replacement of Pump Mo...

Page 5: ...EIGHT Net 203 lbs 92 kg Shipping 220 lbs 100 kg CONNECTIONS ELECTRIC Cord Connection WATER SUPPLY Inlet 1 2 FPT DRAIN Outlet 3 4 FPT CUBE CONTROL SYSTEM N A Internal programming HARVESTING CONTROL SYSTEM Hot Gas and Water Thermistor and Timer ICE MAKING WATER CONTROL Timer Controlled Overflow Pipe COOLING WATER CONTROL N A BIN CONTROL SYSTEM Mechanical Level Switch and Timer COMPRESSOR Hermetic Mo...

Page 6: ... Condenser Control Box Spray Tube Evaporator Fuse Condenser Electrical Box Control Switch Compressor Freeze Water Valve Harvest Water Valve Expansion Valve Drier Wash Valve Rear View of Icemaker Water Tank Bin Control Switch back side of tank Float Switch Pump Motor Bin Control Detector Water Tank Bin Control Pump Motor ...

Page 7: ...e control board checks the position of LF S and proceeds to the freeze cycle if it is closed or calls for a 1 minute fill if it is open 3 Freeze Cycle LED 1 is on Comp and PM continue to run FMS energizes HGV closes water valve relay de energizes and HWV closes and the freeze cycle starts For the first 5 minutes the control board will not accept a signal from LF S This 5 minute minimum freeze acts a...

Page 8: ...d shuts the unit down Note To prevent incomplete batches of ice from forming on the evaporator the control board will only shut down the machine within the first 5 minutes of the freeze cycle If ice pushes the lever in after the first five minutes of the freeze cycle the control board will allow the machine to complete the freeze cycle and the following harvest cycle before shutting down the machine ...

Page 9: ...rmistor temp reaches 48 F 9 C 3 9 kΩ or less Harvest timer starts LF S open Comp continues HGV de energized HWV de energized PM continues FMS energized FWV energized de energized for refills only LF S closed Freeze cycle operation turned over to LF S Comp continues HGV energized FMS de energized LF S Check LF S Check Maximum harvest water valve time 6 minutes HWV time is 6 minutes or the length of ...

Page 10: ...static discharge It is especially important to touch the metal part of the unit when handling or replacing the board 3 Do not touch the electronic devices on the board or the back of the board to prevent damage to the board 4 Do not change wiring and connections Do not misconnect K3 K4 and K5 because the same connector is used for the thermistor float switch and mechanical bin control 5 Always repl...

Page 11: ...Motor icemaking 5 Pump Motor harvest 6 Freeze Water Valve FWV 7 10 Supply Voltage 8 Open Switch for C board and ALPINE board service boards only Bin Control Switch Open LED yellow S4 Dip Switch Bin Control Switch Closed LED green Alarm Buzzer Power LED red lights when power is supplied to the board Relay LEDs 4 indicate which relays are energized as listed below LED 2 green Hot Gas Valve HGV Harve...

Page 12: ...d will signal this problem using 1 beep every 3 seconds The reset button on the control board must be pressed with power on to reset the safety d Low Water Safety The control board checks the position of the lower float switch at the end of the initial one minute water fill cycle and at the end of each harvest cycle If the lower float switch is closed the control board proceeds to the next cycle If t...

Page 13: ...V and PM are energized for 10 seconds between freeze and harvest LEDs 1 3 and 2 are on The built in safeties shut down the unit and have alarms as listed below No of Beeps every 3 sec Type of Alarm Notes 1 High Evaporator Temp temperature 127 F 53 C Check for harvest problem stuck HGV or relay hot water entering unit or shorted thermistor 2 Harvest Backup Timer harvest 20 min for two cycles in a r...

Page 14: ...he temperature of the evaporator outlet to start the harvest timer No adjustment is required If necessary check for resistance between thermistor leads and visually check the thermistor mounting located on the suction line next to the evaporator outlet Temperature F Temperature C Resistance kΩ 0 18 14 401 10 12 10 613 32 0 6 000 50 10 3 871 70 21 2 474 90 32 1 633 Check a thermistor for resistance...

Page 15: ...20 ON ON 180 d S4 dip switch 3 4 5 6 7 8 Factory set for optimum performance Do not adjust e Freeze Timer S4 dip switch 9 10 CAUTION Adjust to proper specification or the unit may not operate correctly The freeze timer setting determines the maximum allowed freeze time to prevent possible freeze up issues Upon termination of freeze timer the control board initiates the harvest cycle After 2 consecu...

Page 16: ...resolved 2 Check to make sure shipping tape has been removed and the wires are connected properly 3 Check to make sure no obstruction prevents the lever from moving to the bin empty position 4 Check proximity switch continuity to make sure it is not stuck open b Machine Will Not Shut Off 1 Confirm that the bin is full and the actuator is in the bin full position On the control board if the green LE...

Page 17: ...ite wire at pin 10 to a white neutral wire for 115 volts Always choose a white neutral wire to establish a good neutral connection when checking voltages A jumper also feeds 115 volts into pin 7 If no voltage is present check the 115 volt supply circuit 4 The output test switch provides a relay sequence test Make sure the control switch is in the ICE position then press the output test switch The ...

Page 18: ...switch located between relays X3 X4 to the ALP position If this switch is placed in the wrong position the unit will not start 4 Adjust the dip switches to the factory default settings See II C 3 a Default Dip Switch Settings S4 dip switch 8 must remain in the OFF position 5 Turn on the power supply then place the control switch in the ICE position The red LED should come on ...

Page 19: ... Harvest Water Valve Water Supply Wash Valve Spray Tube Condenser Access Valve High Pressure Switch Strainer Hot Gas Valve Discharge Line Compressor Access Valve Suction Line Expansion Valve Refrigerant Circuit Water Circuit Drain Water Tank Evaporator Drier Thermistor Insulation Tube Fan Float Switch Pump Motor ...

Page 20: ...t out 412 21 PSIG Cut in 327 21 PSIG 0 B Wiring Diagram 1 KM 251BAH air cooled 10 5 V Water Valve Relay Contactor appearance changed during 2006 Earlier style is shown here and new style is shown above in the wiring diagram ...

Page 21: ...70 21 80 27 90 32 min 100 38 70 21 80 27 90 32 min 100 38 70 21 200 14 1 231 16 2 254 17 9 80 27 223 15 7 271 19 1 285 20 0 90 32 231 16 2 305 21 4 323 22 7 PSIG kg cm 2 G 100 38 229 16 1 309 21 7 340 23 9 70 21 33 2 3 37 2 6 40 2 8 80 27 36 2 6 43 3 0 44 3 1 90 32 37 2 6 48 3 4 50 3 5 PSIG kg cm 2 G 100 38 37 2 6 48 3 4 52 3 7 APPROXIMATE ICE PRODUCTION PER 24 HR AMBIENT TEMP ºF ºC WATER TEMP ºF ...

Page 22: ... bad 1 minute timer in board 4 Initial Harvest Cycle LEDs 1 4 and 2 are on The freeze water valve de energizes and the hot gas valve energizes also energizing the water valve relay the harvest water valve energizes and the contactor coil energizes to start the compressor The evaporator warms and the thermistor senses 48 F 9 C The control board then receives the thermistor s 3 9 kΩ signal and turns...

Page 23: ...ssures should follow performance data provided in this manual 6 Normal Harvest Cycle same as the initial harvest cycle Return to step 4 Note Unit continues to cycle until bin control is satisfied or power is switched OFF The unit always restarts at the 1 minute fill cycle B Diagnostic Charts 1 No Ice Production Problem Possible Cause Remedy 1 The icemaker will not start a Power Supply 1 Off breaker ...

Page 24: ...ecommended pressure k Water Valves 1 Mesh filter or orifice gets clogged and water supply cycle does not finish 1 Clean 2 Coil winding opened 2 Replace 3 Wiring to water valve 3 Check for loose connection or open and replace l Control Board 1 Defective or in alarm 1 See II C 6 Control Board Check Procedure m Control Switch 1 WASH position 1 Move to ICE position 2 Bad contacts 2 Check and replace 2 Wa...

Page 25: ... Board Check Procedure 5 No water comes from spray tubes Water pump will not start or freeze cycle time is too short a Water Supply Line 1 Water pressure too low and water level in water tank too low 1 Check and get recommended pressure b Water Valves 1 Dirty mesh filter or orifice and water level in water tank too low 1 Clean c Water System 1 Water leaks 1 Check connections for water leaks and repl...

Page 26: ...phragm does not close 1 Check for water leaks with icemaker off c Control Board 1 Defective 1 See II C 6 Control Board Check Procedure 2 All ice formed on evaporator does not fall into bin in harvest cycle a Evaporator 1 Scaled up 1 Clean b Water Supply Line 1 Water pressure too low 1 Check and get recommended pressure c Water Filter System 1 Dirty Restricted 1 Replace filter d Water Valves 1 Dirty...

Page 27: ... or condenser ambient or water temperature water pressure and refrigerant charge b See chart 2 1 and check float switch water valves and control board c Check pump hot gas valve expansion valve refrigerant charge and compressor 2 Harvest cycle time is long a See chart 2 2 and check control board thermistor evaporator ambient and or water temperature water supply line water valves and hot gas valve ...

Page 28: ...orn out 1 Replace 2 Fan blade deformed 2 Replace fan blade 3 Fan blade does not move freely 3 Replace c Compressor 1 Bearings worn out or cylinder valve broken 1 Replace 2 Mounting pad out of position 2 Reinstall d Refrigerant Lines 1 Rub or touch other lines or surfaces 1 Replace 3 Ice in storage bin often melts a Drain Line 1 Plugged 1 Clean b Ice Cube Guides 1 Out of position Circulated water f...

Page 29: ...ses and a vacuum pump to the system Be sure to connect charging hoses to both high and low side access valves IMPORTANT The vacuum level and vacuum pump may be the same as those for current refrigerants However the rubber hose and gauge manifold to be used for evacuation and refrigerant charge should be exclusively for POE oils 2 Turn on the vacuum pump Never allow the oil in the vacuum pump to flo...

Page 30: ... charging the unit with a little refrigerant raising the pressure with nitrogen and using an electronic leak detector Note All brazing connections inside the evaporator case are clear paint coated Sandpaper the brazing connections before unbrazing the components Use a good abrasive cloth to remove the coating C Removal and Replacement of Compressor IMPORTANT Always install a new drier every time t...

Page 31: ...e nameplate for the required refrigerant charge 17 Connect the terminals and replace the terminal cover in its correct position 18 Replace the removed parts in the reverse order of which they were removed Replace the panels in their correct positions 19 Turn on the power supply D Removal and Replacement of Drier IMPORTANT Always install a new drier every time the sealed refrigeration system is ope...

Page 32: ... drier located below the expansion valve then place the new drier in position 7 Braze all fittings while purging with nitrogen gas flowing at a pressure of 3 to 4 PSIG WARNING Always protect the valve body by using a damp cloth to prevent the valve from overheating Do not braze with the valve body exceeding 250 F 121 C 8 Check for leaks using nitrogen gas 140 PSIG and soap bubbles 9 Evacuate the sys...

Page 33: ...he solenoid 7 Disconnect the hot gas valve and the strainer 8 Place the new valve and new strainer in position 9 Remove the drier located behind the upper rear panel then place the new drier in position 10 Braze all fittings while purging with nitrogen gas flowing at a pressure of 3 to 4 PSIG CAUTION Always protect the valve body by using a damp cloth to prevent the valve from overheating Do not bra...

Page 34: ...uding drier while purging with nitrogen gas flowing at a pressure of 3 to 4 PSIG 10 Check for leaks using nitrogen gas 140 PSIG and soap bubbles 11 Evacuate the system and charge it with refrigerant See the nameplate for the required refrigerant charge 12 Replace the removed parts in the reverse order of which they were removed 13 Open the water supply line shut off valve 14 Turn on the power suppl...

Page 35: ...refully 2 Always use a recommended sealant High Thermal Conductive Type Model KE4560RTV manufactured by SHINETSU SILICONE Part Code 60Y000 11 or Part Code 4A0683 01 equivalent 3 Always use a recommended foam insulation non absorbent type or equivalent 4 Do not shorten or cut the thermistor leads when installing it 1 Turn off the power supply 2 Remove the panels 3 Disconnect the thermistor leads fr...

Page 36: ...ews securing the compressor base and the condenser Carefully slide the refrigeration assembly forward 5 Remove the closed end connectors from the fan motor leads 6 Remove the fan motor bracket and fan motor 7 Remove the fan blade from the old fan motor and attach it to the new fan motor 8 Install the new fan motor and replace the removed parts in the reverse order of which they were removed 9 Repl...

Page 37: ...ew valve and then install the valve 8 Replace the removed parts in the reverse order of which they were removed 9 Open the water supply line shut off valve 10 Turn on the power supply 11 Check for leaks 12 Replace the panels in their correct positions M Removal and Replacement of Pump Motor 1 Turn off the power supply 2 Remove the top panel and the insulation panel 3 Disconnect the pump suction an...

Page 38: ...acement of Spray Tube 1 Turn off the power supply 2 Remove the top panel and the insulation panel 3 Remove the rubber hoses from the spray tube water supply pipe 4 Release the clamps and disconnect the rubber hoses 5 Remove the spray tube 6 Install the new spray tube and replace the removed parts in the reverse order of which they were removed 7 Replace the panels in their correct positions 8 Turn...

Page 39: ...e the control switch on the control box to the OFF position and move it back to the ICE position after 3 minutes The defrost cycle starts and the cubes will be removed from the evaporator 4 Move the control switch to the OFF position Open the door 5 Disconnect the suction hose to drain the water See Fig 1 6 Reconnect the suction hose back in its correct position after all of the water has drained ...

Page 40: ...WAY Economics Laboratory Inc with 1 gallon 3 8 l of warm water 25 Wash the bin control switch housing water tank float switch detector Cube Guide A Cube Guide B suction hose drain pan drain tube and frame pipe by using a nylon scouring pad brushes and the cleaning solution In addition to the removed parts also wash the bin liner Bracket L and Bracket R with the solution 26 Discard the cleaning solu...

Page 41: ...tion of about 200 ppm 6 Pour the sanitizing solution into the water tank and allow the sanitizer to sit for 10 minutes 7 Move the control switch to the WASH position 8 Close the door 9 After 15 minutes move the control switch to the OFF position 10 Open the door 11 Disconnect the suction hose to drain the water Reconnect the suction hose back in its correct position after all of the water has drai...

Page 42: ...ezing temperatures To drain all water from the icemaker follow the steps below 1 Remove the front panel top panel and insulation panel 2 Move the control switch on the control box to the OFF position 3 Wait 3 minutes then move the control switch to the ICE position 4 Allow the icemaker to complete the one minute fill cycle LED 4 is on then move the switch back to the OFF position 5 Close the potabl...

Page 43: ...nd harvest water valve hose 15 Close the potable water supply line drain valve 16 Remove all ice from the storage bin and clean the bin 17 Turn off the power supply at the breaker box 18 Place the panels back in their correct positions ...

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