Hoshizaki KMS-750MLH User manual

Hoshizaki
“A Superior Degree
of Reliability”
www.hoshizaki.com
Model
KMS-750MLH
Including
Condensing Unit Model SRK-7H
Modular Crescent Cuber
Serenity Series
Hoshizaki America, Inc.
Number: 73152
Issued: 8-13-2007
SERVICE MANUAL
™

2
IMPORTANT
Only qualified service technicians should attempt to install, service or maintain
this icemaker. No service or maintenance should be undertaken until the
technician has thoroughly read this Service Manual. Failure to service and
maintain the equipment in accordance with this manual may adversely affect
safety, performance and warranty coverage.
HOSHIZAKI provides this manual primarily to assist qualified service technicians in the
installation, maintenance and service of the icemaker.
Should the reader have any questions or concerns which have not been satisfactorily
addressed, please call, write or send an e-mail message to the HOSHIZAKI Technical
Support Department for assistance.
HOSHIZAKI AMERICA, INC.
618 Highway 74 South
Peachtree City, GA 30269
Attn: HOSHIZAKI Technical Support Department
Phone: [phone] Technical Service
[phone]
Fax: [phone]
[phone]
E-mail: techsuppor[email protected]
Web Site: www.hoshizaki.com
NOTE: To expedite assistance, all correspondence/communication MUST include the
following information:
• Model Number
• Serial Number
• Complete and detailed explanation of the problem

3
CONTENTS
I. Specifications...................................................................................................................... 5
A. Icemaker ....................................................................................................................... 5
1. KMS-750MLH – SRK-7H ........................................................................................ 5
B. Condensing Unit............................................................................................................ 6
1. SRK-7H ................................................................................................................... 6
II. General Information ........................................................................................................... 7
A. Construction................................................................................................................. 7
1. Icemaker ................................................................................................................. 7
2. Condensing Unit ..................................................................................................... 8
B. Sequence of Operation ................................................................................................. 9
1. One Minute Fill Cycle .............................................................................................. 9
2. Initial Harvest Cycle ................................................................................................ 9
3. Freeze Cycle ........................................................................................................... 9
4. Pump-Out Cycle ...................................................................................................... 9
5. Normal Harvest Cycle .......................................................................................... 10
C. Control Board.............................................................................................................. 12
1. Control Board Layout............................................................................................. 13
2. Features ................................................................................................................ 14
a) Maximum Water Supply Period – 6 minutes....................................................... 14
b) Harvest Backup Timer and Freeze Timer ........................................................... 14
c) High Temperature Safety .................................................................................... 14
d) Low Water Safety ............................................................................................... 14
e) High Voltage and Low Voltage Cut-outs ............................................................. 14
f) LED Lights and Audible Alarm Safeties............................................................... 15
3. Controls and Adjustments ..................................................................................... 16
a) Factory Default Dip Switch Settings ................................................................... 16
b) Harvest Timer (S4 dip switch 1 & 2) ................................................................... 16
c) Pump-Out Timer (S4 dip switch 3 & 4) ............................................................... 17
d) Pump-Out Frequency Control (S4 dip switch 5 & 6)........................................... 17
e) S4 Dip Switch 7 & 8 ........................................................................................... 17
f) Freeze Timer (S4 dip switch 9 & 10).................................................................... 18
g) Float Switch Control (S5 dip switch 1 through 5)................................................ 18
4. Control Board Check Procedure............................................................................ 18
5. Control Board Replacement ................................................................................ 19
D. Harvest Control – Thermistor ...................................................................................... 19
E. Float Switch................................................................................................................. 20
1. Explanation of Operation ....................................................................................... 20
2. Cleaning ................................................................................................................ 20
3. Float Switch Check Procedure ............................................................................. 20
F. Bin Control ................................................................................................................... 22
1. Explanation of Operation ....................................................................................... 22
2. Bin Control Check Procedure ............................................................................... 22
Please review this manual. It should be read carefully before the icemaker is serviced or
maintenance operations are performed. Only qualified service technicians should service
and maintain the icemaker. This manual should be made available to the technician prior to
service or maintenance.

4
G. Switches ..................................................................................................................... 23
1. Control Switch ....................................................................................................... 23
2. Service Switch....................................................................................................... 23
a) DRAIN ................................................................................................................ 23
b) CIRC................................................................................................................... 23
c) WASH ................................................................................................................. 23
III. Technical Information ...................................................................................................... 24
A. Water Circuit and Refrigeration Circuit........................................................................ 24
B. Wiring Diagrams.......................................................................................................... 25
1. KMS-750MLH – SRK-7H....................................................................................... 25
C. Performance Data ....................................................................................................... 26
1. KMS-750MLH – SRK-7H....................................................................................... 26
IV. Service Diagnosis........................................................................................................... 27
A. 10-Minute Diagnostic Procedure................................................................................. 27
B. Diagnostic Charts........................................................................................................ 29
1. No Ice Production .................................................................................................. 29
2. Evaporator is Frozen Up........................................................................................ 32
3. Low Ice Production ................................................................................................ 33
4. Abnormal Ice ......................................................................................................... 33
5. Other...................................................................................................................... 33
V. Removal and Replacement of Components .................................................................... 34
A. Service for Refrigerant Lines ...................................................................................... 34
1. Refrigerant Recovery............................................................................................. 34
2. Brazing................................................................................................................... 34
3. Evacuation and Recharge [R-404A] ...................................................................... 35
B. Condensing Unit.......................................................................................................... 36
1. Removal and Replacement of Compressor........................................................... 36
2. Removal and Replacement of Condenser ............................................................ 37
3. Removal and Replacement of Hot Gas Valve and Liquid Line Valve..................... 37
4. Removal and Replacement of Headmaster (Condensing Pressure Regulator - C.P.
Regulator) .............................................................................................................. 38
5. Removal and Replacement of Fan Motor .............................................................. 39
C. Icemaker .................................................................................................................... 39
1. Removal and Replacement of Evaporator............................................................. 39
2. Removal and Replacement of Expansion Valve .................................................... 40
3. Removal and Replacement of Hot Gas Valve and Liquid Line Valve..................... 41
4. Removal and Replacement of Pump Motor........................................................... 42
5. Removal and Replacement of Fill and Harvest Water Valve.................................. 42
6. Removal and Replacement of Thermistor ............................................................. 43
VI. Cleaning and Maintenance Instructions ......................................................................... 44
A. Cleaning and Sanitizing ............................................................................................. 44
1. Cleaning Procedure............................................................................................... 44
2. Sanitizing Procedure - Following Cleaning Procedure .......................................... 46
B. Maintenance................................................................................................................ 46
C. Preparing the Icemaker for Long Storage................................................................... 47

5
I. Specifications
A. Icemaker
1. KMS-750MLH – SRK-7H
AC SUPPLY VOLTAGE 208-230/60/1 ( 3 wire with neutral for 115V )
AMPERAGE 13 A ( 5 Min. Freeze AT 104°F / WT 80°F )
MINIMUM CIRCUIT AMPACITY 20 A
MAXIMUM FUSE SIZE 20 A
APPROXIMATE ICE PRODUCTION Ambient WATER TEMP. (°F)
PER 24 HR. Temp.(°F) 50 70 90
lbs./day ( kg/day ) 70 * 770 (349) 749 (340) 691 (313)
Reference without *marks 80 754 (342) 722 (328) 647 (293)
90 749 (340) * 700 (318) 630 (286)
100 706 (320) 684 (310) 566 (257)
SHAPE OF ICE Crescent Cube
ICE PRODUCTION PER CYCLE 15 lbs. ( 6.8 kg ) 832 pcs.
APPROXIMATE STORAGE CAPACITY N/A
ELECTRIC & WATER CONSUMPTION 90/70°F 70/50°F
ELECTRIC W (kWH/100 lbs.) 1633 ( 5.6 ) 1636 ( 5.1 )
WATER gal./24HR (gal./100 lbs.) 109 ( 15.6 ) 245 ( 31.8 )
EXTERIOR DIMENSIONS (WxDxH) KMS-750MLH : 30" x 24" x 28" ( 762 x 610 x 711 mm )
SRK-7H : 50" x 17" x 28" ( 1270 x 432 x 711 mm )
EXTERIOR FINISH KMS-750MLH : Stainless steel; Galvanized steel ( Rear )
SRK-7H : Galvanized steel
WEIGHT KMS-750MLH : Net 128 lbs. (58kg ), Shipping 163 lbs. (74kg)
SRK-7H : Net 198 lbs. (90kg ), Shipping 240 lbs. (109kg)
CONNECTIONS - ELECTRIC Permanent Connection
- WATER SUPPLY Inlet 1/2" FPT
- DRAIN Outlet 3/4" FPT
- CONDENSATE DRAIN 5/8" OD Pipe
CUBE CONTROL SYSTEM Float Switch
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, Model CS08KQE-PFV
CONDENSER Air cooled, Fin and Tube type
EVAPORATOR Vertical type, Stainless Steel and Copper
REFRIGERANT CONTROL Thermostatic Expansion Valve
Condensing Pressure Regulator
REFRIGERANT CHARGE R-404A, 10 lb. 11 oz. ( 4850 g )
( Icemaker 7 oz.; Comp/Cond unit 10 lbs. 4 oz. )
DESIGN PRESSURE High 467 PSIG, Low 230 PSIG
P.C. BOARD CIRCUIT PROTECTION High Voltage Cut-out ( Internal )
COMPRESSOR PROTECTION Auto-reset Overload Protector ( Internal )
REFRIGERANT CIRCUIT PROTECTION Auto-reset High Pressure Control Switch
LOW WATER PROTECTION Float Switch
ACCESSORIES -SUPPLIED N/A
-REQUIRED Ice Storage Bin or Dispenser
OPERATING CONDITIONS VOLTAGE RANGE 187 - 253 V
AMBIENT TEMP.
KMS-750MLH 45 - 100° F
SRK-7H ( Outdoor use ) -20 - 122° F
WATER SUPPLY TEMP. 45 - 90° F
WATER SUPPLY PRESSURE 10 - 113 PSIG
ENG.F-011.1.0205
Note: We reserve the right to make changes in specifications and design without prior
notice.

6
B. Condensing Unit
1. SRK-7H
Note: We reserve the right to make changes in specifications and design without prior
notice.
AC SUPPLY VOLTAGE 208-230/60/1 ( 3 wire with neutral for 115V )
( Connection to icemaker )
AMPERAGE 13 A ( 5 Min. Freeze AT 104°F / WT 80°F )
MINIMUM CIRCUIT AMPACITY 20 A
MAXIMUM FUSE SIZE 20 A
EXTERIOR DIMENSIONS ( WxDxH ) 50" x 17" x 28" ( 1270 x 432 x 711 mm )
DIMENSIONS INCLUDING LEGS ( WxDxH ) 52-3/8" x 19-1/2" x 43" ( 1330 x 495 x 1092 mm )
EXTERIOR FINISH Galvanized steel
WEIGHT Net 198 lbs. ( 90 kg ) Shipping 240 lbs. ( 109 kg )
CONNECTIONS - ELECTRIC Permanent - Connection
- REFRIGERANT Suction line 1-1/8-12 UNF Fitting ( # 11 Parker )
Liquid line 1-1/16-12 UNF Fitting ( # 10 Parker )
COMPRESSOR Hermetic, Model CS08KQE-PFV
CONDENSER Air cooled, Fin and Tube type
COMPRESSOR PROTECTION Auto-reset Overload Protector ( Internal )
FAN MOTOR PROTECTION Thermal Protection
REFRIGERANT CIRCUIT PROTECTION Auto-reset High Pressure Control Switch
REFRIGERANT CONTROL Condensing Pressure Regulator
REFRIGERANT CHARGE 10 lbs. 4 oz. ( 4650 g )
DESIGN PRESSURE High 467 PSIG, Low 230 PSIG
OPERATING CONDITIONS VOLTAGE RANGE 187 - 253 V
AMBIENT TEMP. ( Outdoor use ) -20 - 122° F
ACCESSORIES -SUPPLIED Leg 2 pcs
Hex. Head Bolt w/Washer M8 x 16 16 pcs
Hex. Nut M8 16 pcs
ENG.F-032.1.0205

7
II. General Information
A. Construction
1. Icemaker
Spray Tubes
Hot Gas Valve
Liquid Line Valve
Service
Valve
(High Side)
Drier
Wash Valve
Service
Valve
(Low Side)
Fill Water Valve
Control Board
Pump Motor
Float Switch
Drain Water Valve
Control Switch
Bin Control Switch
Service Switch
Harvest Water Valve
Thermistor
Control Box

8
2. Condensing Unit
Condenser
Headmaster
(C.P. Regulator)
Hot Gas Valve
Liquid Line Valve
Junction Box
Receiver Tank
Accumulator Shut-off Valve
(Low Side)
Compressor
Shut-off Valve (High Side)
Fan Motor and Fan Blade
Access Valve
Thermostat (Discharge Pipe)

9
B. Sequence of Operation
The steps in the sequence are as outlined below. When power is supplied, the red
"POWER OK" LED and the green "BC CLOSED" LED on the control board come on (If
the yellow "BC OPEN" LED is on, the unit will not start. In this case clear ice away from
the bin control actuator in the bin area). A 5-second delay occurs at startup. Note that the
order of the green sequence LEDs from the outer edge of the board is 1, 4, 3, 2.
1. One Minute Fill Cycle
LED 4 is on. FWV opens and the fill period begins. After 1 minute, the board checks for a
closed LF/S. If LF/S is closed, the harvest cycle begins. If not, FWV will remain energized
through additional 1 minute cycles until water enters the sump and LF/S closes. This
serves as a low water safety to protect the water pump.
2. Initial Harvest Cycle
LEDs 1, 4 and 2 are on. Comp, FMR, HGVs, HWV and X1 relay energize, FWV closes.
The control board monitors the warming of the evaporator via the thermistor located
on the suction line. When the thermistor reaches 48°F (9°C), the control board reads a
3.9 kΩsignal from the thermistor and turns harvest termination over to the adjustable
harvest timer which is factory set for normal conditions. The timer has settings of 60,
90, 120, and 180 seconds (S4 dip switch 1 & 2). When the harvest timer completes its
count down, the harvest cycle is complete and the freeze cycle starts. The minimum
total time allowed by the board for a complete harvest cycle is 2 minutes. HWV is open
during harvest for a maximum of 6 minutes or the length of harvest minus 50 seconds,
whichever is shorter. LED 4 goes off when HWV closes. PM energizes and runs for the
last 50 seconds of harvest. LED 3 comes on when PM energizes. At the end of harvest,
the 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, FMR and PM continue to run, LLVs open, HGVs close. For the first
5 minutes the control board will not accept a signal from LF/S. This 5 minute minimum
freeze acts as a short cycle protection. At the end of 5 minutes, LF/S assumes control.
As ice builds on the evaporator the water level in the sump lowers. The freeze continues
until LF/S opens and terminates ice production, provided the 5 minute freeze timer has
expired.
Note: Because the KMS-750MLH does not require a refill, the UF/S is not used.
4. Pump-Out Cycle
LEDs 1, 4, 3, and 2 are on. With dip switches 5 and 6 in the factory default postion,
the 1st pump out occurs after the 11th freeze cycle and every 10th cycle thereafter.
Comp and FMR continue to run, DWV, HWV, and HGVs open, LLVs close. PM stops
for 2 seconds. PM restarts, pumping water from the water tank through the DWV and
down the drain. At the same time, water flows through the vent tube to power flush the
F/S. After 10 seconds, the pump out is complete. The pump-out frequency control is
factory-adjusted to drain the water tank every 10 cycles, and no adjustment is required.
However, where water quality is bad and the icemaker needs a pump out more often, the
pump-out frequency can be adjusted. See "II.C.3.d) Pump-Out Frequency Control."

10
5. Normal Harvest Cycle
LEDs 1, 4 and 2 are on. Comp, FMR and HGVs remain energized. HWV and X1 relay
energize, PM stops. As the evaporator warms, the thermistor reaches 48°F (9°C). The
control board then receives the thermistor's 3.9 kΩsignal and starts the harvest timer.
When the harvest timer completes its count down, the harvest cycle is complete. The
minimum total time allowed by the board for a complete harvest cycle is 2 minutes. HWV
is energized during harvest for a maximum of 6 minutes or the length of harvest minus
50 seconds, whichever is shorter. LED 4 goes off when HWV closes. PM energizes and
runs for the last 50 seconds of harvest. LED 3 comes on when PM energizes. At the
end of harvest, the 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.
The unit continues to cycle through freeze and harvest cycles until the bin control
activates (opens) and 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 bin control actuator in (open) 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.
Legend: Comp–compressor; DWV–drain water valve; FMR–remote fan motor; F/S–float
switch; FWV–fill water valve; HGV–hot gas valve; HWV–harvest water valve;
LF/S–lower float switch contacts; LLV–liquid line valve; PM–pump motor;
UF/S–upper float switch contacts (not used on models with 0 refill)

11
Components Energized when the Control Switch is in the SERVICE Position When in the "SERVICE" position, the control switch supplies power to the service switch and the machine is in service mode. The service switch has three positions: "DRAIN," "CIRC." and "WASH." See the information below for details of each function.
DRAIN Power is supplied to the pump and drain valve. This drains the water tank. CIRC. Power is supplied to the pump only. This operation can be used to circulate cleaner and
sanitizer for extended periods of time over the outside surface of the evaporator.
WASH Power is supplied to the pump and wash valve. This operation is used to circulate cleaner
and sanitizer over both the inside and outside surfaces of the evaporator.
4. Pump-Out Cycle
Legend: Comp - compressor DWV - drain water valve FMR - remote fan motor FWV - fill water valve HGV - hot gas valve HWV - harvest water valve LF/S - lower float switch contacts LLV - liquid line valve PM - pump motor
KMS-750MLH Sequence Flow Chart and Component Operation
1. One Minute
Fill Cycle
2. Harvest Cycle 3. Freeze Cycle
Pump motor stops for 2 sec. and then runs for 10 sec.
Cycle Steps
FWV energized
LF/S open
LF/S closed
Comp energized FMR energized HGV energized HWV energized FWV de-energized DWV de-energized
Thermistor temp reaches 48°F (9°C) (3.9 kΩor less) Harvest timer starts
LF/S open
Comp continues FMR continues PM continues LLV energizes HGV de-energized
LF/S closed
Freeze cycle operation turned over to LF/S
PM de-energizes 2 sec. ,
energizes for 10 sec. Comp continues FMR continues DWV energized HGV energized HWV energized LLV de-energized
LF/S check
LF/S check
• Maximum harvest water valve time: 6 minutes
(HWV time is 6 minutes or the length of harvest minus 50 sec., whichever is shorter. PM energizes and runs for the last 50 sec. of harvest.)
• Maximum harvest time: 20 minutes
Thermistor in control
1 to 3 minute timer in control
• Minimum freeze time: 5 minutes • Maximum freeze time: freeze timer setting
5 minute timer in control
Lower float switch in control
Initial startup always begins here
"G" board will have 5 second delay
If LF/S is open, compressor stops and cycle returns to 1 minute fill
Factory set for every 10th cycle
50 sec.
PM energized HWV de-energized
LF/S open

12
C. Control Board
• A HOSHIZAKI exclusive solid-state control is employed in the KMS-750MLH Modular
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, mechanical bin
control and float switch.
5. Always replace the whole board assembly if it goes bad.
6. Do not short out power supply to test for voltage.

13
Control Board
Part Number 2A3792-01 (factory); 2A3792-02 (service)
Control Products "G" Control Board
Alarm Reset Button
Output Test Button
(used to test relays on board)
Connector K3
Harvest Control
(thermistor)
Connector K4
Mechanical Bin
Control
Label
(board revision level
indicated on label
on side of relay)
Connector K5
Float Switch
Part Number
Connector K1
Pins #1 through #10
#1, 9 Magnetic Contactor
#2 Hot Gas Valves (HGV)
Water Valve Relay
#3 Liquid Line Valves (LLV)
#4 Pump Motor (icemaking)
#5 Pump Motor (harvest)
#6 Fill 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)
LED 2 (green)
Hot Gas Valves (HGV)
LED 3 (green)
Pump Motor (PM)
(PM on, but LED off,
at freeze cycle)
LED 4 (green)
Fill Water Valve
(FWV) (when LED 2
is off)
Harvest Water Valve
(HWV) (when LED 2
is on)
LED 1 (green)
Compressor (Comp)
Connector K2
Transformer
S5 Dip Switch
(factory set -
do not adjust)
1. Control Board Layout

14
2. Features
a) Maximum Water Supply Period – 6 minutes
The harvest water valve will be open during harvest for 6 minutes or the length of harvest
minus 50 seconds, whichever is shorter.
b) Harvest Backup Timer and Freeze Timer
The harvest backup timer shuts down the icemaker if, for two cycles in a row, the harvest
cycle takes more than 20 minutes to complete. The control board will signal this problem
using 2 beeps every 3 seconds.
The freeze timer shuts down the icemaker if, for two cycles in a row, the freeze cycle
takes longer than the time specified to complete. The control board will signal this
problem using 3 beeps every 3 seconds. The time is factory set using S4 dip switch 9 &
10.
The alarm reset button on the control board must be pressed with power on to reset
either of these safeties.
c) High Temperature Safety
The temperature of the suction line in the refrigeration circuit is limited by the high
temperature safety. This protects the unit from excessively high temperatures. If the
evaporator temperature rises above 127 ± 7°F (53 ± 4°C), the control board reads a
.804 kΩsignal from the thermistor and operates the safety. This shuts down the circuit
and the icemaker automatically stops.
The control board will signal this problem using 1 beep every 3 seconds. The alarm 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 the lower float switch is open, the
control board calls for a one minute water fill cycle. After one minute, the control board
checks the position of the float and either proceeds to the next cycle if the lower float
switch is closed or calls for an additional one minute fill if the switch is open. This serves
as a low water safety to protect the water pump.
e) High Voltage and Low Voltage Cut-outs
High voltage and low voltage cut-outs help protect the icemaker from supply voltages
outside of the accepted range.
If miswiring causes excessive voltage (147Vac ±5% or more for 3 seconds) on the
control board, the high voltage cut-out shuts down the circuit and the icemaker
automatically stops. The control board will signal this problem using 7 beeps every 3
seconds.
The icemaker also automatically stops in cases of insufficient voltage (92Vac ±5% or
less). The control board will signal this problem using 6 beeps every 3 seconds.
When the proper supply voltage is resumed, the icemaker automatically starts running
again.

15
f) LED Lights and Audible Alarm Safeties
The red LED indicates control voltage and will remain on unless a control voltage
problem occurs. At startup a 5 second delay occurs while the board conducts an internal
timer check. A beep occurs when the control switch is moved to the "ICE" position.
The green LEDs 1 through 4 energize and sequence from initial startup as listed in the
table below. Note that the order of the LEDs from the outer edge of the board is 1, 4, 3, 2.
For more information, see "II.B. Sequence of Operation."
Sequence Step LED Energized
Components
Time LEDs are On
Min. Max. Avg.
1 Minute Fill Cycle 4 FWV 60 seconds
Harvest Cycle 1, 4 and 2 HWV, HGV,
Comp,FMR
2 minutes 20 minutes 3 to 5 minutes
Last 50 seconds of harvest, HWV de-energizes and PM energizes
(LEDs 1, 3 and 2 are on)
Freeze Cycle 1 Comp, PM,
FMR, LLV
5 minutes freeze timer
setting
30 to 35 minutes
Pump-Out 1, 4, 3, and
2
Comp, HGV,
PM, HWV,
DWV, FMR
10 seconds 20 seconds factory default
setting
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, stuck HM or
shorted thermistor.
2 Harvest Backup Timer
(harvest > 20 min. for two
cycles in a row)
Check for open thermistor, HGV not opening,
TXV leaking by, low charge or inefficient Comp.
3 Freeze Timer
(freeze > specified setting
for two cycles in a row)
Timer is factory set using
S4 dip switch 9 & 10
Check for a float switch stuck closed (up), HWV
or FWV leaking by, HGV leaking by, TXV not
feeding properly, low charge, HM not bypassing
or inefficient compressor.
To reset the above safeties, press the alarm reset button with the power supply on.
6 Low Voltage
(92Vac ±5% or less)
Red LED will turn off if voltage protection oper-
ates.
The control voltage safeties automatically reset
when voltage is corrected.
7 High Voltage
(147Vac ±5% or more)
Legend: Comp–compressor; DWV–drain water valve; FMR–remote fan motor; FWV–fill
water valve; HGV–hot gas valve; HM–headmaster; HWV–harvest water valve;
LLV–liquid line valve; PM–pump motor; TXV–thermostatic expansion valve

16
3. Controls and Adjustments
a) Factory Default Dip Switch Settings
The dip switches are factory-adjusted to the following positions:
S4 Dip Switch
Dip Switch No. 1 2 3 4 5 6 7 8 9 10
KMS-750MLH OFF OFF OFF ON ON ON ON OFF OFF ON
S5 Dip Switch (Do Not Adjust)
Dip Switch No. 1 2 3 4 5
KMS-750MLH OFF OFF OFF OFF OFF
b) Harvest Timer (S4 dip switch 1 & 2)
The harvest timer starts counting when the thermistor reads 48°F (9°C) at the evaporator
outlet. No adjustment is required under normal use, as the harvest timer is adjusted to
the suitable position. Before changing this setting, call the HOSHIZAKI Technical Support
Department at 1-800-233-1940 for recommendations. Keep in mind that setting the
harvest timer to a longer setting will decrease 24 hour production.
Dip Switch Setting Time
(seconds)
No. 1 No. 2
OFF OFF 60
ON OFF 90
OFF ON 120
ON ON 180
S4 Dip Switch
Freeze Timer (9 & 10)
Pump-Out Frequency Control (5 & 6)
Pump-Out Timer (3 & 4)
Harvest Timer (1 & 2)
Normally in the OFF position (8)
Do not adjust (7)

17
c) Pump-Out Timer (S4 dip switch 3 & 4)
CAUTION
Leave in the factory default position; otherwise, the harvest water valve will not
open during pump out.
During cycles when a pump out is called for, the pump motor drains the water tank for
the time determined by the pump-out timer. The pump-out timer acts in place of the
harvest timer during cycles with a pump out. The pump-out timer setting also determines
whether the harvest water valve is open or closed during pump-out.
The pump-out timer is factory-adjusted, no adjustment is required.
Dip Switch Setting Time (seconds) Harvest
Water
Valve
No. 3 No. 4 T1 T2
OFF OFF 10 150 closed
ON OFF 10 180 closed
OFF ON 10 120 open
ON ON 20 180 closed
T1: Time to drain the water tank
T2: Harvest timer at pump out
Depending on the pump-out frequency control setting (dip switch 5 & 6), pump out
occurs every cycle, or every 2nd, 5th or 10th cycle.
d) Pump-Out Frequency Control (S4 dip switch 5 & 6)
The pump motor drains the water tank at the frequency set by the pump-out frequency
control.
The pump-out frequency control is factory-adjusted to drain the water tank every
10 cycles, and no adjustment is required. With dip switches 5 and 6 in the factory
default postion, the 1st pump out occurs after the 11th freeze cycle and every 10th cycle
thereafter. However, where water quality is bad and the icemaker needs a pump out
more often, the pump-out frequency can be adjusted as shown in the table below.
Dip Switch Setting Frequency
No. 5 No. 6
OFF OFF every cycle
ON OFF every 2 cycles
OFF ON every 5 cycles
ON ON every 10 cycles
e) S4 Dip Switch 7 & 8
Factory set for optimum performance. Do not adjust.

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f) 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 consecutive timer terminations, the control board shuts the
machine down. In this case, see "IV.B.3. Low Ice Production" for possible solutions.
The freeze timer is factory adjusted and no adjustment is required.
Dip Switch Setting Time
(minutes)
No. 9 No. 10
OFF OFF 60
OFF ON 50
ON OFF 70
ON ON 60
g) Float Switch Control (S5 dip switch 1 through 5)
Do not adjust. These must be left in the factory default position or the unit will not operate
properly.
4. Control Board Check Procedure
Before replacing a control board that does not show a visible defect and that you suspect
is bad, always conduct the following check procedure. This procedure will help you verify
your diagnosis.
1) Check the S4 and S5 dip switch settings to assure that they are in the factory default
positions.
2) Turn the control switch to "ICE" and check for proper control voltage. If the red LED
is on, the control voltage is good. If the red LED is off, check the control transformer
circuit.
3) Check the 115 volt input at the wire harness terminals and the 10-pin connector. Check
the brown and white 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.) On the 10 pin connector, a jumper also feeds 115 volts into pin #7. If no
voltage is present, check the 115 volt supply circuit.
4) The output test button provides a relay sequence test. Make sure the control switch is
in the "ICE" position, then press the output test button. The correct lighting sequence
should be 1, 4, 3, 2. Some components (e.g., the compressor) will cycle during the test.
Note that the order of the relays from the outer edge of the board is 1, 4, 3, 2. After
checking the sequence, the unit automatically starts at the 1 minute fill cycle. If the
LEDs light in a different sequence, the control board is bad and should be replaced.

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5. Control Board Replacement
The application switch located between relay X3 & X4 must be set to match the original
board application. Place this switch in the ALP position. The dip switches should be
adjusted to the factory default settings as outlined in this manual. S4 dip switch #8 must
remain in the "OFF" position.
D. Harvest Control – Thermistor
A thermistor (semiconductor) is used for a harvest control sensor. The resistance varies
depending on the suction line temperatures. The thermistor detects the 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 by using the following procedure:
1) Disconnect the connector K3 on the board.
2) Remove the thermistor. See "V.C.6. Removal and Replacement of Thermistor."
3) Immerse the thermistor sensor portion in a glass containing ice and water for 2 or 3
minutes.
4) Check for a resistance between thermistor leads. Normal reading is within 3.5 to 7 kΩ.
Replace the thermistor if it exceeds the normal reading.

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E. Float Switch
1. Explanation of Operation
The float has 2 switches within the float switch. The lower switch (black and blue wires) is
used for low water safety protection and termination of the freeze cycle. The upper switch
(black and red wires) is not used on the KMS-750MLH.
2. Cleaning
Depending on local water conditions, scale may build up on the float, float switch shaft
and inside the housing. Scale on the float or shaft can cause the float to stick causing
erratic operation. The float switch should be cleaned and checked before replacing.
First, disconnect the black K5 float switch connector from the control board and remove
the float switch and rubber boot from the icemaker. Remove the rubber boot from the
float switch. Twist the mechanical lock at the top of the float housing and lower out the
float and float shaft. Remove the retainer clip from the shaft and slide the float off the
shaft. Soak the switch assembly in ice machine cleaner. Wipe down the shaft, float,
housing, and rubber boot with cleaning solution. See "VI. Cleaning and Maintenance
Instructions."
3. Float Switch Check Procedure
Before replacing a float switch that you suspect is bad, make sure the float switch has
been cleaned. This procedure will help you verify your diagnosis. The float switch has
three wires. The black wire is common. The blue wire is for the lower float switch contact
and the red wire is for the upper float switch contact. The upper switch is not used on the
KMS-750MLH.
1) Disconnect the black K5 float switch connector from the control board.
2) Drain the reservoir water.
3) Turn the control switch to "ICE".
4) As water fills the reservoir, the lower float switch contacts should close. Check continuity
of the lower float switch contacts using the black and blue wires.
5) Turn the control switch to "OFF".
6) Drain the reservoir water.
7) As water drains, the lower float switch contacts should open. Check continuity of the
lower float switch contacts using the black and blue wires.
8) Reconnect the black K5 connector to the control board when finished.