Scotsman NU150, NU220, NU100, NU300 Service Manual













SERVICE MANUAL
NU100/150/220/300













Part Number 99300407-01 Version: A

NU Undercounter Ice Machine Service Manual Table of Content

s

1

Tables of Content Page



How to use this manual 2
Model and serial number 2

Specifications 3-7

Overview and installation 8
Safety instructions 8
Position and level adjustment 8
Water supply and drainage connection 9
Power supply connection 9
Final check list 10

Start-up 11
Operating check 12
Ice machine adjustments 13

How the ice maker works 14
Freezing cycle 14-15
Harvest cycle

16-17

Components Description 18-20

Wiring diagram 21

Trouble shooting table 22-23

MAINTENANCE & CLEANING INSTRUCTION 24
Summary 24
Maintenance of refrigeration system 24
Water system cleaning 24-25
Winterizing Procedures 25



2

NU Under

counte

r Ice Machine

S

e

rvice ManualH

ow to use this manua

How to Use this manual



This manual is provided as an aid to the service
technician in installation, operation, and
maintenance of the ice machines. This manual
can also assist the service technician to
troubleshoot and diagnose most of the
problems that may occur with the machine.



Most aspects of the NU Series machines are
covered in this manual, however, if you
encounter any conditions not addressed herein,
please contact the Scotsman Technical Service
Department for assistance. You can contact the
Scotsman Technical Services Department in
the following ways:



Scotsman Ice systems (Shanghai) Co.LTD
Room 2503, Building NO.2, NO.20 of Xu Hong
Middle Road, Xuhui District, Shanghai, China

Telephone Numbers: [phone]
Service hotline: [phone]

[e-mail]
www.scotsman-china.com



NU series service part list is provided
separately with this manual.

Model and Serial Number

Model Numbers



Serial numbers

The serial number includes 12 numbers; the
front 2 letters are the series name, the next 2
numbers are referring to the year the machine
was manufactured, then the 2 month codes,
the final six numbers are the serial identifier.



NU 14 06

000001

Serialidentifier

Month

Yea r 

Seriesname

NU 15 0 H

A

2

Design change number

A=Air Cooled W=Water Cooled

H=Half Cube; F=Full Cube

Power
0 = 220V 50Hz

;

24h Ice Capacity
(21℃ Air/10 ℃ Water)
15*10=150 lbs

Series Name

3

NU Under

counte

r Ice Machine

S

e

rvice Manual

Sepec

ifi

cations

NU100/150 Specification





Water Temperature

NU100

Air Temperature

F 50° 60° 70° 90°
℃ 10° 15° 21° 32°
50° 121 lbs
10° 55 kg
70° 99 lbs
21° 45 kg
90° 70.4 lbs
32° 32 kg
100° 59.4 lbs
38° 27 kg



Water Temperature

NU150

Air Temperature

F 50° 60° 70° 90°
℃ 10° 15° 21° 32°
50° 176 lbs
10° 80 kg
70° 150 lbs
21° 68 kg
90° 106 lbs
32° 48 kg
100° 88 lbs
38° 40 kg



MODEL Condenser

Minimum

Circuit

Ampacity

(A)

Fuse

(A)

Water

Consumption

(Gal)

Power

Consumption

(KWH)

Size mm

(Width*Depth*Height)

Net

Weight

(kg)

32℃ Air/21℃ Water

100lbs Ice

NU100*A Air Cooled 3.5 10 32 12.6 600*610*770 50
NU150*A Air Cooled 4 10 20 8.5 600*610*770 50





4

NU Under

counte

r Ice Machine

S

e

rvice Manual

Sepec

ifi

cations

NU100/150 Size

With Short Foot With High Foot

5

NU Under

counte

r Ice Machine

S

e

rvice Manual

Sepec

ifi

cations

NU220/300 Specification



Water Temperature

NU220

Air Temperature

℉

50° 60° 70° 90°

℃

10° 15° 21° 32°

50° 242 lbs
10° 110 kg
70° 220 lbs
21° 100 kg
90° 154 lbs
32° 70 kg
100° 132 lbs
38° 60 kg



Water Temperature

NU300

Air Temperature

℉

50° 60° 70° 90°

℃

10° 15° 21° 32°

50° 308 lbs
10° 140 kg
70° 293 lbs
21° 133 kg
90° 220 lbs
32° 100 kg
100° 180 lbs
38° 82 kg

MODEL Condenser

Minimum

Circuit

Ampacity

(A)

Fuse

(A)

Water

Consumption

(Gal)

Power

Consumption

(KWH)

Size mm

(Width*

Depth*

Height)

Net

Weight

(kg)

32℃ Air/21℃ Water

100lbs Ice

NU220*A Air Cooled 4.5 10 19 9 650*690*870 65
NU300*A Air Cooled 5 10 19 8 650*690*1004 65



6

NU Undercounter Ice Machine Service Manual Specification

s

NU220 Size



7

NU Undercounter Ice Machine Service Manual Specification

s

NU300 Size



8

NU Undercounter Ice Machine Service Manual Overview and Installatio

n

Overview and installation

This manual is provided the instruction in
installation, start-up, operation, maintenance,
cleaning and each operation procedure for
Scotsman NU series ice machine.

Safety instruction

In order to ensure the machine working
normally in long term, please read the manual
carefully and implement strictly before
installation. The producer is not responsible for
any damage or body injury due to ignoring the
safety instructions. If there is any doubt, please
contact the local dealer.

Installation requirements

Please ensure the following items are met
during you determining the installation location:
y Power source: the power switch for the ice

machine should be hand reachable, ensure
that the power supply reliable grounded.

y Water supply: the water supply switch

should be hand reachable.
Water drain: be sure that the drain pipe has
3cm drop per meter.

In order to reach its high performance and
ensure its durability, please pay attention to the
following items:

Operating parameters Lowest Highest

Ambient temperature

10C

(50F)

40C

(100F)

Water inlet temperature 5C (40F) 35C(90F)

Water inlet pressure

1 bar

gauge

5 bar

gauge

Maximum power supply

variation based on the

nameplate

-10% +10%

Orientation and level adjustment

In order to get good ventilation and heat
radiation, the distance between the machine
and the wall, etc. should be more than 150mm.

Don’t hang curtain or pile any goods around the
machine to avoid overheat caused by bad
ventilation, be sure there is no heat source
(such as stove, oven, etc.) around the machine
and the working environment of the ice maker
should not be over humidity.

Before use, install the four supplied legs into
leg acceptor on bottom side of unit base, Level
the unit in both the left to right and front to rear
directions.

Note：

This ice machine is only designed for indoor
installation. For the loss or damage caused by
exceeding the following limited temperature or
involved in the security claims, it is beyond the
general finite warranty clause of Scotsman
producer.

Note：

In order to avoid any infection on the user, the
water for making ice should be the potable
water. If needs, please install water filter or
water processor.

9

NU Undercounter Ice Machine Service Manual Overview and Installatio

n

Water supply and drainage connection

Choose the ice machine water supply should
be considered:
y Water quality requirements：Ice thickness

detector cannot work normally in non

conductible water; Water containing too

many minerals will produce a cloudy like

ice and increase water scale accumulation

of each part of the water system.
y Enough water pressure ： The water

pressure should be between 1 to 5 bar. Ice

machine cannot work normally if the water

pressure is lower than 1 bar (14 psi).
You cannot ignore these three requirements,
because water is the key factor in the ice
making.

Water supply

Connect the 3/4" male thread connector of
water inlet solenoid valve with supply line
connector and install a water supply valve in an
accessible position between the water supply
line and the unit.
If water contains a high level of impurities, it is
advisable to install an appropriate water filter or
treatment facility.

Water Drain

The recommended drain tube is a plastic or
flexible tube with 18 mm (3/4") I.D. which runs
to an open sewer.
Note: The water supply and the water drain
must installation should conform to the local
code. In some case a licensed plumber or a
plumbing permit is required.

Note ：Ensure the drain pipe has 3 cm drop per
meter at least.

Electrical Connections

y See name plate for current requirements to

determine wire size to be used for electrical

connections.
y All SCOTSMAN ice machines require a

solid earth wire. All SCOTSMAN ice

machines are supplied from the factory

completely pre-wired and require only

electrical power connections to the wire

cord provided at rear of the unit.
y Make sure that the ice machine is

connected to its own circuit and individually

fused (see data plate for fuse size).

y The maximum allowed voltage variation

should not exceed -10% and + 10% of the
nameplate rating. Low voltage can cause
faulty functioning and may cause serious
damage to the overload switch and motor
windings.

y Check consistency between voltage on the

line and the ice maker’s data plate before
connecting the unit (power supply).

Note:

All external wiring should conform to national,
state and local standards and regulations.

10

NU Under

counte

r Ice Machine

S

e

rvice ManualFin

al Chec

k Li

st

Final Check List

1. Is the unit in a room where ambient

temperatures are within a Minimum of 10℃

(50℉) even in winter?

2. Is there at least a 15 cm (6") clearance

around the unit for proper air circulation?

3. Is the unit level? (IMPORTANT)

4. Have all the electrical and plumbing been

connected, and is the water supply valve

open?

5. Is the power supply voltage in accordance

with the nameplate ratings?

6. Has the water supply pressure been

checked to ensure a water pressure of at

least 1 bar (14 psi)?

7. Check all refrigerant lines and conduit lines

to guard against come-off by vibrations and

possible damage.

8. Have the bolts holding the compressor

been checked to ensure that the

compressor is fixed onto the mounting

base?

9. Have the ice bin and cabinet been wiped

clean?

10. Has the user been given the Manual and

been instructed on the importance of

periodic maintenance checks?

11. Has the manufacturer’s registration card

been filled in properly? Check for correct

model and serial number according to the

serial plate and mail the registration card to

the factory.

12. Has the user been given the name and the

phone number of the authorized

SCOTSMAN Service Agent?



11

NU Undercounter Ice Machine Service Manual Start U

p

Start-Up

After having correctly installed the ice maker
and completed the plumbing and electrical
connections, perform the following “Start-up”
procedure.

y Connect the main power switch.
y Power on the power switch on the right side

of the NU front panel.

Power Switch Panel

During the cleaning operation, check and see
that the incoming water flows through the inlet
pipe above the water trough into the drain pipe.

During the water filling phase the components
energized are:

 Water inlet solenoid valve
 Defrost solenoid valve
 Water pump
 Water drain solenoid valve

At the end of the cleaning operation, the unit
will enter into the freezing cycle automatically
with the start up of compressor; water level of
the water tank gets into the control state. The
water pump starts to work after the startup of
compressor 30 seconds. Fan Motor (air cooled
model) is controlled by the temperature sensor
of the condenser.

Note:

If within 3 Minutes of the water filling phase,
the machine water trough does not get filled
with water from the water inlet, it is advisable
to check:
y The water pressure of the water supply

pipe that must be at least 1 bar (14 psi).
Max 5 bar(70 psi).

y The filtering device installed in the water

pipe that may reduce the water pressure
below the Minimum value of 1 bar (14
psi).

y Any clogging situation occurs to the inlet

water strainer and/or the flow controller of
the inlet valve.

Note:

Every time the unit returns under power after
having been switched off, the water supply
valve, defrost valve, water pump and the water
drain valve get energized for a period of 3
Minutes, thus to admit new water to the
machine sump reservoir to fill it up and
eventually, to wash-off any dirt that can have
deposited in it during the unit off period.

12

NU Undercounter Ice Machine Service Manual Operating Chec

k

Operating check

If required, the refrigerant service gauges can
be mounted on the high pressure side and low
pressure side to check discharge and suction
pressures of the compressor. (The valve
welded with the compressor shell is low
pressure valve; the valve welded with
discharge tubes is high pressure valve)

Check the evaporator, check whether the spray
system is correctly seated and whether the
water jets spray water on the surface of the
evaporator uniformly, and also make sure that
there is no excessive water spilling from
evaporator plate into ice bin.

The ice making processes start with the water
uniformly flowing through the surface of the
evaporator, the ice molds then get gradually
refrigerated by the heat exchange which has
refrigerant flowing into the evaporator coil.
During the freezing process, the ice thickness
sensor controls the freezing cycle time. The

electric components in operation during the ice

making cycles are:

 Compressor
 Water pump
 Fan Motor is controlled by the temperature

sensor of the condenser.

The defrost cycle takes place with the defrost

valve and water drain valve simultaneously

activated. The electric components in operation
during defrost cycle are:

 Compressor
 Defrost valve
 Pump and the Water drain valve (controlled

by PC board and can drain after each
cycle)

 Fan Motor (air cooled model) is controlled

by the temperature sensor of the
condenser.

Inspection during defrost cycle

y Check whether the water drain's operation

is normal (if water drain function is set), and
that water in the sump reservoir is correctly
drained.

y Check the quality of ice cubes just released.

If it doesn’t reach the requirement, some
adjustment should be carried out (See
adjustment procedure). If the ice cubes are
thin and cloudy , probably the ice machine is
shortage of water or the water quality is not
good. It may require the usage of an
appropriate water filter or treatment unit.

y To make sure the correct operation of the

ice level control, use your hand to press the
ice sliding plate down which simulates the
bin is full, so the ice cube cannot go
through the ice sliding plate and fall into the
ice bin. After 40 seconds, the unit should
stop with the Bin Full indicator light on the
display plate of PC board. Move your hand
out to allow the resumption of the ice

Note:

The length of the defrost cycle is
automatically controlled by the program of
the PC board, depending on the ice required
thickness and ambient condition.

Note: The ice thickness sensor is installed
on the surface of the evaporator; the
length of the entire freezing cycle is
controlled by the interval time of the ice

thickness sensor probes the ice cubes.

 If room temperature is below 15℃, the

ice making cycle will be shorter (about
15-25 Minutes).

 If room temperature is above 30℃, the

ice making cycle will be longer (about
25-40 Minutes).

HighSide

LowSide

13

NU Undercounter Ice Machine Service Manual Operating Chec

k

sliding plate. After 3 minutes, the ice maker

returns to ice making cycle.

Remove the refrigerant service gauges (if fitted)
and refit the unit panels previous removed after
adjustment.

Instruct the user on the general operation of the
ice maker, the cleaning and maintenance.



14

NU Undercounter Ice Machine Service Manual Adjustment

s

Ice machine adjustments



Adjustment of ice thickness

The ice thickness has been adjusted to a
suitable position before it was shipped out. If
needed, adjust the screw on the ice thickness
sensor properly to meet the suitable thickness.
Clockwise rotation can make the ice thickness
thicker, while counterclockwise can make the
ice thickness thinner.

Drainage adjustment

The adjustment of the drainage number of the
ice machine depends on the local water quality
and water cleanliness.

Recommendation：

To obtain a higher degree of transparency ice
and to maintain the cleanliness of the sink,
recommends that the drainage is set behind
one ice making cycle, this is the factory setting.

Note：

When adjusting the screw on the ice thickness
sensor, do not adjust too much, 1 laps per time
or so; after three cycles, if the ice thickness still
cannot meet the requirements, adjust it again.
The ice thickness could be adjusted to a
required level by this mean.

Thicker

15

NU Undercounter Ice Machine Service Manual How the ice maker work

s

How the ice maker works

For NU ice maker, the water for making ice is pumped into the spray pipe by water pump. After flew
out from the holes of spray pipe, then it will flow over the surface of the ice plate with constant and
even speed. At this spot, some of the water will turn into ice; the other will flow back to the water
trough by gravity and will be re-circulated by water pump.

Freezing Cycle

The refrigerant gas discharged from the
compressor gets into the condenser, where it is
cooled and condensed into liquid. The liquid
will flow into drier filter, and then it will pass
through the expansion valve. After that, the
pressure and temperature of the refrigerant
liquid will get much lower.

Then the refrigerant begins to evaporate when
it gets into the evaporator coil pipes and
exchange heat with water following over the ice

molds.

The refrigerant then increases in volume and
changes entirely into vapor during heat
exchanging process. The refrigerant vapor then
passes through the suction line heat exchanger
(used to prevent that any small amount of liquid
refrigerant may reach the compressor) at the
suction line and flow through the suction pipe. It
exchanges heat with the refrigerant flowing into

the capillary tube or liquid line copper tubes

(warmer), before to be sucked in the

compressor and to be re-circulated as hot
vapor.

The 30 seconds before freezing cycle is
pre-cooling period, in this period, the
compressor is working, water pump is not, fan
is working (controlled by the temperature
sensor of condenser) and water inlet valve is
working (controlled by the water-level sensor in
the water trough).

The freezing cycle is controlled by the ice
thickness sensor, as long as the sensor probes
the ice and holds for 30s, the ice thickness has
reached the set point. Then, the freezing cycle
is end. The total time of freezing cycle depends
on the ambient temperature and ice thickness
set.

Note:

Ice making indicator light, ZBLX green light
on the display board (on the PC board
display-ZBL1) will be illuminating since the

beginningof ice making.

16

NU Undercounter Ice Machine Service Manual How the ice maker work

s

During refrigeration cycle, the pressure range
of high-pressure side is:
NU100： 15～26 bar （218psi～377psi）

NU150： 15～27bar （218psi～391psi）
NU220： 15～26 bar （218psi～377psi）
NU300： 15～27bar （218psi～391psi）

The pressure of the high-pressure side is
controlled by the condensation temperature
sensor located at the condenser. If the
condensation temperature senor senses the
condensation temperature exceeds the set
value, it will feed back to the PC board which
will control the operation of fan.

Contrarily, when the condensation temperature
senor is lower than the set value of
condensation temperature, it will feed back to
the PC board which will control the outage of
fan.

At the start of freezing cycle, pressure of
refrigeration suction side or low-pressure side
is rapidly reduced; the pressure will be
gradually reduced as the ice thickness
increases. When the ice cube is completely
formed in the ice mold, pressure reaches:
NU100： 5～2 bar （58psi～29psi）

NU150： 5～2 bar （58psi～29psi）
NU220： 5～2 bar （58psi～29psi）
NU300： 5～2 bar

（58psi～29psi）
Overall length of freezing cycle is between
15-40 Minutes.

Notes:

If condensation temperature probe senses
the temperature is higher than 70℃(160°F),
the unit will stop caused by the startup of
protection device, while the R2LX on display
board will be illuminating(light SL1 on PC
board will quickly blink), warning user of too
high condensation temperature.

After the condensation temperature is lower
than 70℃(160°F), switch off the unit by the

power button before the unit restarts, and
switch on the ice maker, then waiting for 3
Minutes. After 3 Minutes of water injection,

the ice maker is working normally.
Reasons for abnormal operation as follows:

Condenser is block;
y Air temperature is higher than 40 ℃

(100°F);

y To avoid abnormal operation and risk of

the unit, the user should cut off the power
upon one of the above reasons.

Note：

If defrost cycle does not start 60 Minutes after
the starting of freezing cycle, the unit will
automatically identify as freezing overtime and
automatically enter into the defrost cycle. If the
freezing overtime occurs to the ice maker 5
times in a row (caused by short of refrigerant,
abnormal operation of defrost valve, etc.),
freezing indicator light-ZBLX+R1LX lights will
be blinking(on the PC board, it shows light
SL1 blinking and light ZBL1 blinking). At this
time, the user needs to disconnect the unit
and contact with the service agent.

17

NU Undercounter Ice Machine Service Manual How the ice maker work

s

Defrost cycle

The defrost cycle starts after the completion of
the freezing cycle. Refrigerant hot gas
discharged from the compressor flows into the
evaporator coil though defrost valve.

Refrigerant circulated in the evaporator coil
heats the ice molds to melt the ice cubes. Ice
cubes fall off from the mold cup, into declining
ice sliding plate by gravity and finally fall into
the ice bin.

After the end of defrost cycle, hot gas valve,
drain valve (equipped as per PC board) closed.
The unit starts its new ice making cycle.

Refrigerant charge
Refrigerant: R404A
NU100：320g

NU150：320g
NU220：360g
NU300：400g

Components Description

Ice thickness sensor

The ice thickness sensor is located at the top of

the evaporator plate. During freezing cycle, if

the sensor probes ice, it will convert into
electronic signal which will be transmitted to the
PC board.

The PC board will control the time of the
freezing cycle according to the ice thickness

signal. The time of the freezing cycle depends

on the ambient temperature and the ice
thickness; the higher the temperature is and
the thicker the Ice thickness sets, the longer

freezing cycle will be.

Condenser temperature sensor

The condenser temperature sensor probe is
located in the condenser, which detects the
condenser temperature variations and
transmits electronic signals to PC board.

Ice Full Controller

The ice full controller is divided into two parts:
one part is a magnet part which is installed in
the ice slide plate, and the other part is a
magnetic sensor, which is installed on the
plastic frame of the evaporator.

If the ice trough is not re-set and the
magnetism is not sensed by the magnetic
sensor within 40 seconds, it means that the ice
cubes made in the last freezing cycle cannot
drop into the ice storage bin, the ice storage bin

Note:

If the condenser temperature probe detects
that the condenser temperature is over 70℃
(160℉), the PC board will stop the operation
of the machine immediately. The light R2LX
will alarm and keep illuminating (The light
SL1 on PC board will

q

uickly blink

)

Note ：

Ice thickness sensor is inoperative with non
conductible water.

Note:

Defrost indicator light TBLX is illuminating
(on PC board, the light TBL1 is illuminating)
at the start of defrost.

18

NU Undercounter Ice Machine Service Manual Components Descriptio

n

is full and the Bin Full BMLX (BML1 on PC
board) Red LED indicates.

When the ice in the storage bin is taken out or
moved, the ice trough is re-set, the magnetic
sensor detects the magnetism, and the state of
ice bin full is released then enters into the
freezing cycle.

Note:

If the state of “ice bin full” is released within 3
minutes, the Bin Full BMLX Red LED blinks,
3 minutes later the ice machine will enter into
freezing cycle automatically.
If the state of ”ice bin full” is released after 3
minutes more, the ice machine will enter into
freezing cycle upon it is started.

19

NU Undercounter Ice Machine Service Manual Components Descriptio

n

Water Level Sensor

The water level sensor is located at the top of
the water tank. When water level reaches a
certain level during water filling, the magnetic
sensor of the water level sensor detects the
magnetism and signals it to the PC board.
Once the PC board receives the signal, then it
will power off the water inlet valve and water
filling is stopped.

The water level sensor is installed on the
support of water level sensor and can be
adjusted.

Vertical Type Water Spray System

The water pump spray out the water sucked
from the water tank. The water flow into the
spray tube through the PVC tube, then pass the
pinholes on the water tube, and then flow
evenly through the ice molds of the evaporator,
thus ice cubes are made. It is cycled
continually.

Water pump

The water pump operates continually
throughout the freezing cycle and keeps water
flowing continually through the ice molds of the
evaporator and produces ice cubes.

Recommendation:
The water pump should be checked at least
every 3 months.

Water Inlet Solenoid valve - 3/4" Male Fitting

The water inlet solenoid valve is located on the
up and down water support. The incoming
water is controlled by the PC board, among
which one water flow controller is used to
control the water flow incoming the water tank.

Defrost Solenoid Valve

The defrosting solenoid valve, located at the
hot gas bypass tube, is consisted of valve body
and coil. During defrosting and water filling
period, operation is controlled by the PC board.

During the defrost cycle, the defrost solenoid
valve is energized and sucks the push rod of
the valve body in order to let the hot gas
discharged from the compressor to flow directly
into the evaporator pipe to melt the formed ice
cubes.

Fan

The Fan is controlled by PC board to draw
cooling air through the condenser fins, thus to
lower the discharge temperature of the
compressor. Normally it operates intermittently
only during the freezing cycle to keep the
condenser pressure between two
corresponding pressure values.

Compressor

The hermetic compressor is the heart of the
refrigerant system of the ice machine and it is
used to circulate and retrieve the refrigerant
throughout the entire system.

It compresses the low pressure refrigerant
vapor causing its temperature to rise and
become high pressure hot vapor which is then
released through the discharge valve and then
will reach the condenser.

Water Drain Solenoid Valve

The water drain solenoid valve is controlled by
the PC board. Based on the different
configuration of the PC board(Drainage is set
behind one ice freezing cycle, which is set by
factory), it starts operating for 30 seconds so
that all remaining water containing minerals in
the water tank drains out.

Note:

When the water level in the water tank is
considered to be too high and water
overflows whenever water is filled, it is
means that the water level sensor cannot
control the water inlet valve, the position of
the water level sensor can be adjusted lower.
If the position of the water level sensor is
adjusted low and the problem is not solved, it
means that the water level sensor is failure
and should be re

p

laced.

20

NU Undercounter Ice Machine Service Manual Components Descriptio

n

High Pressure Control switch

The high Pressure Control is in the ice machine,
when the ice machine occurs failure and the
high pressure is more than 33bar(462psi), the
high pressure control switch will cut off the
electricity supply to protect the ice machine.
The indicator lights ZBLX+R1LX will be keeping
blink (on the PC board, light SL1 will bright.)
until the high pressure lowers to 23bar (322psi),
then can restart the ice machine.

Water temperature sensor

The water temperature sensor, located in the
water pipes from the water pump to the ice
plate, is used to detect the temperature of
circulating water in real time and sent signals to
PC board with which controls the operation of
pump during the ice making cycle.

Thermostatic Expansion Valve

The Thermostatic Expansion Valve regulates
the flow of refrigerant to the evaporator and
reduces pressure of liquid refrigerant from
condensing pressure to evaporating pressure.

This drop in pressure causes the refrigerant to
cool. The cooled refrigerant absorbs heat from
the water circulating over the evaporator. As
the evaporator fills with liquid refrigerant, the
evaporator becomes colder.

The flow of refrigerant into the evaporator is
controlled by the temperature at the outlet of
the evaporator. The expansion valve bulb,
mounted to the top of the suction pipe, senses
the evaporator outlet temperature causing the
expansion valve to open or close.

As ice forms on the evaporator, the
temperature drops and the flow of refrigerant
into the evaporator decreases, resulting in a
drop in suction pressure.

The evaporator should become completely
flooded (filled with liquid refrigerant) during the
freezing cycle. Only a completely flooded
evaporator will have a uniform freeze pattern
(ice forms across the evaporator). A starved
evaporator (not enough liquid refrigerants) will
have poor or have no ice formation, the outlet
tube(s) exiting the evaporator will also not frost.
All tubes should frost approximately 5 minutes
from the start of the freezing cycle.

An expansion valve that is restricted or not
opening properly will starve the evaporator
resulting in lower than normal suction pressure.
A low refrigerant charge will also starve the
evaporator and cause low suction and
discharge pressures. If not sure the amount
refrigerant in the system, retrieve it back and
recharge of the correct amount of refrigerant
and then re diagnosis whether the valve is
defective.

If the evaporator is starved but the suction
pressure is higher than normal, it shows the
TXV is good; If the TXV keeps open or if the
thermal bulb doesn’t contact well with the
suction pipe, the flow of refrigerant into the
evaporator will be too much and the liquid
refrigerant will flood the compressor. The
suction pressure will be higher than normal; the
formation of ice is uniform, but the ice making
cycle will become longer.

symptoms issue corrections

Evaporator
flooded but
suction pressure
not dropping.
Compressor has
been checked
and appears
well.

Suction pipe at
compressor may
be colder than
normal

the thermal
bulb of TXV
doesn’t
contact well
with the
suction pipe

TXV bulb is
installed
incorrect

System
overcharged

Tighten bulb clamp,
and confirm that the
insulation is good.
Put the thermal
bulb on the top of
suction pipe.
Recharge the
refrigerant, and
replace the TXV.

Evaporator
starved, no frost
on pipe(s)
exiting
evaporator,
suction pressure
is low.

Machine low
on refrigerant
charge

TXV restricted
or stuck

Retrieve the
recharged
refrigerant back and
recharge of the
correct amount of
refrigerant
Replace TXV and
dry filter

Air filter

The NU series air cooled ice machine is
equipped with air inlet filter. As the ice machine
runs, part of dust will be sucked in the machine
through the filter, thus it cuts down the air
volume to be sucked in and then the efficiency
of the ice machine.

21

NU Undercounter Ice Machine Service Manual Components Descriptio

n

In order to enable the ice machine working
efficiently, had better clean the air filter monthly.
If the filter is damaged due to aging, call the
Scotsman service agent to replace it.

Power switches on front panel

There are two buttons on NU front panel: the
right green switch is the power switch, the red
switch is the cleaning switch.

PC Board (Data processor)

The PC board, fitted in its box located in the left
bottom of the front of the unit, consists of one
power-in high voltage transformer, one PC
board with both high and low voltage and a
display panel connected with the PC board.

The PC board is the brain of the ice machine; it
receives signals transmitted from the four
sensors through its micro processor to control
the operations of the different electrical
components of the ice machine (such as
compressor, Fan, defrosting valve, water inlet
valve, drain valve, water pump).

The lamps on the control box

BMLX： Ice full
ZBLX： Freezing
TBLX： Defrosting
SWLX： Water Supplying
R1LX： Water Shortage

R2LX： High Temperature Alarm
CLLX： Cleaning
MODE： Mode Button（Function is the same
with the main control board MODE)
CLEAN： Clean button（Function is the same
with the main control board CLEAN)

Mode Button Functions

Press the button one time in order, the machi ne
will enter the next step:
Power on - Water Supplying – Pre-Cooling –
Freezing - Defrosting - Ice Bin Full Detecting

The function of the clean button

As power switching on, the clean button only
activates in the first minute. Press the clean
button and hold for 5 seconds, the ice machine
will enter into the clean procedure automatically .
Had better use Scotsman supplied cleaning
solution and sanitizer to clean and sanitize.

Alarm lamps failure description:

lamps State Failure Description
BMLX + R1LX On Ice trough failure
ZBLX + R1LX On Making ice overtime

more than 5 times

R1LX + R2LX On Condenser sensor

failure

BMLX + R2LX On Ice thickness sensor

failure

SWLX + R2LX On Water level sensor

failure
R1LX On Shortage of water
R2LX On High temperature

alarm
R1LX + R2LX Blink High pressure alarm
TBLX Blink Ice harvest overtime

more than 3 times
SWLX Slowly

Blink

Water temperature

sensor failure

Warning:

Only authorized maintenance people are
allowed to press the MODE button.

22

NU Undercounter Ice Machine Service Manual Wiring Diagra

m

Wiring diagram NU100/150/220/300



23

NU Undercounter Ice Machine Service Manual Trouble Shooting Tabl

Trouble shooting table

Symptom Possible Cause Suggested Correction

Unit does not
run

Abnormal power supply Check power supply voltage, if no voltage, check

power supply line
Check power supply voltage, if it is low, contact
power supply company

The fuse on PC board blew Replace the fuse. If the fuse is broken again, check

the cause.
The machine is stopped
abnormally(such as high
temperature protection)

Press the MODE key on the PC board to reset, the

machine starts or starts automatically 2 hours later

or unplug the power plug, plug it again 3 minutes

later, the machine starts.
Ice full Adjust the position of the ice cubes in the storage

bin to let the ice trough reset and then start the

machine
Abnormal water supply See the processing method for water-shortage

Compressor
runs
intermittently

Low voltage Check circuit for overloading
Non-condensable gas in
system

Check power supply voltage, if it is low, contact

power supply company

Purge the system and re-charge
Compressor starting device
with loose wires

Check for loose wires in starting device
Mechanical problem Replace compressor

Cubes too
small

Ice making cycle too short Check the distance between the ice thickness and

the evaporator plate
Expansion valve partially
blocked

Check the expansion valve, if damage , replace

it
Moisture in the system Purge the system and re-charge
Shortage of water See the processing method for water-shortage

Shortage of refrigerant

Check for leaks in the refrigerating system &

recharge

Cloudy ice

Shortage of water See the processing method for water- shortage
Dirty water supply Use water softener or water filter
Accumulated impurities Cleaning as the procedure
Water temperature sensor
failure

Replace the water temperature sensor

Shortage of
water

Water spilling out through ice
chute

Tighten the screws on the clamping plate of the

PVC pipe to reduce water flow
Water inlet solenoid valve not

opening

Check, if damage, replace it
Water leak in water tank

Check for the leaking points and repair it.

If necessary, replace it.

Water inlet valve blocked Replace the water inlet valve
Water drain valve leak Check, if damage, replace it

24

NU Undercounter Ice Machine Service Manual Trouble Shooting Tabl

Trouble shooting table

Symptom Possible Cause Suggested Correction

Irregular cubes
size & some cloudy

Spray pipe blocked Clean the spray pipe
Shortage of water

See the processing method for

water-shortage
Machine unlevel Level the machine as required
Water temperature sensor failure Replace the water temperature sensor

Decreased ice
capacity

Inefficient compressor Replace the compressor
Water valve leak Check, if damage, replace it
Spray pipe blocked Check, if blocked, clean it.
Non-condensable gas in system Vacuum and re-charge
Bad ventilation Improve ventilation or put the machine

to the good ventilation place
Too much dust on air filter Clean the air filter, if needed, replace it.
Expansion valve partially blocked Check, if damage, replace it
Defrost valve leaking Change charged volume, release

slowly
Refrigerant over charge
Shortage of refrigerant

Vacuum and re-charge according to the

nameplate
Discharge pressure too high or
too low

Check for the cause of incorrect

discharge pressure
Defrost valve blocked or not

open

Check, if damage, replace it

Unit doesn’t defrost
or no ice

PC board Failure

Check, if damage, replace it
Defrost valve not opening Check, if damage, replace it

Water inlet solenoid valve not
opening

Check, if damage, replace it

Incorrect discharge
pressure

Inoperative condenser sensor Check, if damage, replace it
Too much or less charged

refrigerant, or non-refrigerant gas
was charged

Check whether the refrigeration system

is leakage

Vacuum and re-charge according to the

nameplate and the requirement from

Scotsman Company
Inoperative PC board Check, if damage, replace it

Excessive water on
unit base

Water system leak

Check for the leaking points and repair

it. If necessary, replace it.





25

NU Undercounter Ice Machine Service Manual Clean and Maintenanc

Clean and maintenance

General

The periods and the procedures for
maintenance and cleaning can be adjusted.

Cleaning, especially, depends upon local water
and ambient conditions and the ice volume
produced. Each ice machine must be
maintained individually in accordance with its
particular location requirements.

Ice-making System Maintenance
description

The following maintenance on the ice machine
should be scheduled at least two times per
year:

1. Unplug the power plug at the end of the
defrost cycle.

2. Check and clean the water inlet strainer.

3. Check that the ice machine is leveled in
side to side and in front to rear directions.

4. Use special ice machine cleaning liquid to
clean water system, evaporator and ice
storage bin.

5. When air cooled icemaker stops, can
remove the air filter.

6. Check for water leaks and tighten drain
pipe. Pour water into storage bin to verify
whether the drain pipe is Smooth and
clean.

7. Check for refrigerant leaks.

8. Check size, condition and quality of ice
cubes. Perform adjustment of cube size
control as required.

Water System Cleaning
Cleaning

1. Prepare special cleaning solution for the ice
machine in a plastic container.

2. Scoop out all the ice cubes stored into the
bin to prevent them from being
contaminated with the cleaning solution.

3. Use a brush to take some cleaning solution
to dissolve the impurity material on the ice
module of the evaporator and clean scale
deposit.

4. Pour the cleaning solution into the water

trough of the ice machine.

5. Turn on the power switch, press “clean
button” and hold for 5 seconds, let the
machine go to the Cleaning and rinsing
procedure (Cleaning RED light will blink
fast), all cleaning and rinsing time is about
40 minutes. After cleaning and rinsing
procedure finished, the cleaning RED light
will blink slowly.

6. Remove the water spray pipe and the water
trough to wash them separately (if
necessary).

7. Turn off the power switch after cleaning and
rinsing process finished. Turn on the power
switch again, the ice machine starts
freezing cycle normally.

Sanitizing

1. Do sanitizing after cleaning operation for
the ice machine:

2. Prepare a plastic container, use warm
water of 45-50℃ (113℉-122℉) to dilute
the cleaning sanitizer.

3. Pour the sanitizer into the water trough of
the ice machine.

4. Turn on the power switch, press “clean
button” and hold for 5 seconds, let the
machine go into the cleaning and rinsing
procedure (Cleaning RED light will blink
fast), all cleaning and rinsing time is about

Warning:
Never mix the cleaning solution with the

Note:

Cleaning solution for ice machine is
corrosive. If it splashing on your mouth can
cause mouth burns, So don't make it splash.
In case cleaning solution splashes on your
mouth or eyes, use a lot of water or milk to
wash and should go to hospital immediately.
When washing the external surface, children
are not allowed to close.
Cleaning solution should be kept away from
children.

Warning:

Before opening cleaning solution, must check
the instruction of the cleaning solution in
order to avoid dama

g

e.

Note:

Cleaning should be varied according the
local water quality and the operating
condition of each ice machine. Check
frequently cleanliness of ice cubes and the
components of the water system before and
after cleaning to determine the cleaning
frequency and procedures needed.

26

NU Undercounter Ice Machine Service Manual Clean and Maintenanc

40 minutes. After cleaning and rinsing
procedure finished, the cleaning RED light
will blink slowly.

5. At the end of the freezing cycle, make sure
of proper quality and cleanness of the ice
cubes and that, they do not have any acid
taste.

Wipe clean and rinse the inner surfaces of the
storage bin.

Winterizing Procedures

1. Check the ice machine, if ice is being made,
initiate harvest or wait for freezing cycle
end.

2. At the beginning of harvest, cut off the
water supply to the ice machine.

3. At the end of harvest, cut off the power
switch and drain water in the system
completely as far as possible.

4. Take out all of the ice in the storage bin and
discard.

Important!

Whenever the ice machine is taken out of
operation during the winter months, the
procedure below must be performed. Failure to
do so may cause serious damage and will void
all warranties.

Note:

To prevent the accumulation of undesirable
bacterial, it is necessary to sanitize the
interior of the storage bin every week.

Note:

If the ice is cloudy and sour, use hot water to
dissolve them and pour them to the safety
place appointed in order to avoid eating by
mistake which may cause injury.





























Scotsman Ice Systems (Shanghai) Co., Ltd.





Address ： Room 2505, Building 2, No 20
Xuhong Middle Rd, Shanghai, China. (200235)

Phone：00 86 - 21- 61313200

Fax: 00 86 - 21- 61313330
Hotline: 00 86 - 4006300076
E-Mail: [e-mail]
Website: www.scotsman-china.com

