Scotsman NM1850R User manual

INTRODUCTION
To the owner or user: The service manual
you are reading is intended to provide you,
and the maintenance or service technician,
with the information needed to install, start up,
clean, maintain, and service this ice system.
The NM1850R is a remote condenser modular
ice system. It features: front service for the
freezer, gearmotor, control box, water
reservoir, and bin control; an electronic circuit
for monitoring ice and water level; a
thermostatic expansion valve; and R-502 as
the refrigerant.
TABLE OF CONTENTS
For the Installer
Specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
Location . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
Remote Condenser . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
For the Plumber . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
For the Electrician . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
Final Check List . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
Start Up . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
Component Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
Maintenance & Cleaning . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
Service Diagnosis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26
Removal and Replacement
Water Reservoir & Bin Controls . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30
Thrust Bearing & Breaker . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31
Auger . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32
Water Seal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33
Evaporator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34
Gearmotor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35
Circuit Board Testing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37
Parts Lists and Wiring Diagrams are located in the center of this manual, printed on yellow
paper.
NM1850R
September, 1992
Page 1

FOR THE INSTALLER
The NM1850R is designed to fit
the following Scotsman storage
bins:
••B90 and extentions, with bin
top KBT18.
••BH800 no bin top needed.
••BH900 using bin top KBT14.
When installing a new system,
check to be sure that you have
everything you need before
beginning:
••Correct Bin
••Correct Ice Machine
••Correct Bin Top
••All kits, legs, and information
required for the specific job. BACK VIEW Liquid Line
Connection
(right system) Discharge Line
Connection
(left system)
Remote Condenser
Junction Box
Electrical Inlet
Water Inlet 3/8" Flare
Drain 3/4" FPT
21.66"
3"
5.25"
20.84"
Allow 6"
above
machine for
service.
15.53" 21"
3.1" 3.1"
4.5"
9.43"
17.8"
18.8"
There are two separate ice making
and refrigeration systems in this
model. The liquid and discharge
lines from each system must go to
separate circuits in one remote
condenser (RC1052).
* Minimum Circuit Ampacity is used to determine wire size and type per National Electric Code.
The Standard Finish is Enamel - Sandalwood. There is an optional stainless steel panel kit,
SPKFM42 available to convert the unit to Stainless Steel. It is field installed.
Model
Number
NM1850RE-32A
NM1850RE-3A
Dimensions
(w/o bin)
H X W X D
27" x 42" x 24"
same
Basic
Electrical
208-230/60/1
208-230/60/3
Ice
Type
NUGGET
same
Cond.
Type
R/Air
R/Air
Min.
Circuit
Ampacity
18.2
15.5
Max
Fuse
Size
25
20
TOP VIEW
Allow 6" of space behind the machine
for utility connections.
Ice Chute
6.7" x 6.2"
34.84" 13.84"
18.28"
SPECIFICATIONS: ICEMAKER
NM1850R
September, 1992
Page 2

FOR THE INSTALLER
Installation Limitations:
This ice system is designed to be installed
indoors, in a controlled environment:
Min Max
Air Temperature 500F 1000F
(Not including the remote condenser)
Water Temperature 400F 1000F
Water Pressure 20 PSIG 80 PSIG
Voltage -5% +10%
(Compared to the nameplate)
Operating the machine outside of the
limitations is misuse and can void the warranty.
Water Limitations:
An ice machine is a food manufacturing plant;
it takes a raw material, water, and turns it into
a food product, ice. The purity of the water is
very important in obtaining pure ice and in
maximizing product life. This is not intended
as a complete resource for water related
questions, but it does offer these general
recommendations:
1. Check with a water treatment specialist for
a water test, and recommendations regarding
filters and treatment.
2. In most cases, the water used to make ice
should be filtered or treated, depending upon
the water.
There is no one type of water filter
that will be effective in all situations.
That is
why a water test is important.
Scotsman Ice Systems are designed and
manufactured with the highest regard for
safety and performance. They meet or
exceed the standards of UL, NSF, and CSA.
Scotsman assumes no liability or responsibility
of any kind for products manufactured by
Scotsman that have been altered in any way,
including the use of any part and/or other
components not specifically approved by
Scotsman.
Scotsman reserves the right to make design
changes and/or improvements at any time.
Specifications and design are subject to
change without notice.
1.25" 21.12" Drain
3/4"
FPT
Typical Storage Bin - B90
NM1850R
September, 1992
Page 3

REMOTE CONDENSER SPECIFICATIONS
22"
27.81"
19.86"
5.75"
1/2" MALE QUICK CONNECT
COUPLING FOR USE WITH
RT625 OR RT640
PRECHARGED LINE SET
LIQUID LINE 3/8" MALE
QUICK CONNECT
COUPLING FOR USE WITH
RT625 OR RT640
PRECHARGED LINE SET
3.5" 6.5"
1.9"
5.0"
5.38"
7.5"
32.56"
RT-625 Precharged line set, 25’, R-502 - 2 required.
Or: RT-640. Precharged line set, 40’, R-502 - 2 required.
DIMENSIONS
H" X W" X D"
MODEL USE WITH MINIMUM CIRC.
AMPACITY+ BASIC ELECTRICAL
RC1052 27.8" X 22 X 37.94" 1 NM1850R 2 208-230/60/1
+Included with the icemakers minimum circuit ampacity. Use this
value to determine wire size between icemaker and fan motor.
ICEMAKER NAMEPLATE
LOCATED ON BACK PANEL
SERIAL PLATE LOCATED
BEHIND FRONT PANEL
NM1850R
September, 1992
Page 4

FOR THE INSTALLER
Location
After uncrating and inspection, the unit is
ready for installation. It is important that the
machine be installed in a location where it has
enough space around it to be accessible for
service, usually a minimum of 6 inches. Try to
avoid hot, dirty and crowded locations. Be
sure that the location for the machine is within
the limitations described on page 3.
Storage Bin
Tip the storage bin on its back, using parts of
the carton to protect the exterior finish. Install
the legs into the threaded holes in the bottom
of the bin. Turn the leg levelers all the way in
preparation for leveling later. Return the bin to
the upright position, remove paper covering
the bin gasket.
Install the bin top according to the directions
with the bin top.
Note: Do not push bin into position, but lift it
there. Pushing a bin, especially one with ice in
it, can cause damage to the legs and the leg
mounts. Ice Maker
The machine is heavy, so the use of a
mechanical lift is recommended for lifting the
machine high enough to install on top of the
bin. After the unit is placed on the bin, line it
up so it is even with the back side. Secure the
machine to the bin with the hardware provided
with the machine.
Remove the front panel and remove any
shipping blocks.
Note: Be sure to allow a 6" minimum space
above the top of the machine for service.
Typical Storage Bin with Extension and Bin Top
NM1850R
September, 1992
Page 5

FOR THE INSTALLER: Remote Condenser
Location
Limited to a 40 foot or a 25 foot length of
precharged refrigerant tubing connecting the
icemaker to the remote condenser. The
condenser must be above or level with the
icemaker.
Select the best available location, protecting
the condenser from extremes of dirt, dust, and
sun.
Meet all applicable building codes. Usually
the services of a licensed electrician are
required.
Roof Attachment
1. Install and attach the remote condenser to
the roof of the building, using the methods and
practices of construction that conform to the
local building codes, including having a
roofing contractor secure the condenser to the
roof.
2. Have an electrician connect the remote
condenser fan motor to the icemaker, using
the junction box at the back of the icemaker.
PRECHARGED LINE ROUTING
////////////////////////////CAUTION/////////////////////////////
Do not connect precharged tubing until all
routing and forming of the tubing is complete.
See the coupling instructions, page for
connecting instructions.
/////////////////////////////////////////////////////////////////////////
1. Each set of precharged refrigerant lines
(either 25 foot or 40 foot) consists of a 3/8 inch
diameter liquid line and a 1/2 inch diameter
discharge line. Both ends of each line have
quick connect couplings, one end has a
schrader valve connection, that end goes to
the condenser.
Note: The openings in the building ceiling or
wall, listed in the next step, are the minimum
sizes recommended for passing the refrigerant
lines through.
2. Have the roofing contractor cut a minimum
hole for the refrigerant lines of 1 3/4 inch.
Check local codes, a separate hole may be
required for the electrical power to the
condenser.
////////////////////////////CAUTION/////////////////////////////
DO NOT KINK OR CRIMP REFRIGERANT
TUBING WHEN INSTALLING IT.
/////////////////////////////////////////////////////////////////////////
3. Route the refrigerant lines through the roof
opening.
Follow straight line routing whenever possible.
Any excess tubing MUST be retained within
the building.
4. Spiral the excess length of pre charged
tubing inside the building. Use a horizontal
spiral (as illustrated) to avoid any traps in the
lines.
5. Have the roofing contractor seal the holes
in the roof per local codes.
REMOTE CONDENSER
LOCATE REMOTE
CONDENSER
ABOVE ICEMAKER
SPIRAL
EXCESS
TUBING
INSIDE
BUILDING
NM1850R
September, 1992
Page 6

COUPLING INSTRUCTIONS
/////////////////////////////CAUTION/////////////////////////////
The couplings on the sets of precharged lines
are self sealing when installed properly.
Carefully follow the instructions:
//////////////////////////////////////////////////////////////////////////
1. Remove the protector caps and plugs.
Wipe the seats and threaded surfaces with a
clean cloth to be certain that no foreign matter
remains on them.
2. Lubricate the inside of the couplings,
especially the O-Rings with refrigerant oil.
3. Begin tightening the couplings together by
hand, then using two wrenches (it is important
that ONLY the nut on the precharged lines be
turned, the other parts of the couplings must
NOT be allowed to turn or the process will tear
out the diaphragms and they will be loose in
the refrigeration system) tighten the coupling
until it bottoms out or a definite increase in
resistance is felt.
4. Using a marker or pen, mark a line
lengthwise from the coupling union nut to the
bulkhead. Then tighten the coupling and
additional 1/4 turn. As the nut turns, the line
will show when 1/4 turn is made.
5. Connect the 3/8 inch liquid line (schrader
valve end) to the remote condenser fitting
marked "liquid line".
6. Connect the other end of the liquid line to
the icemaker fitting marked "liquid line."
7. Connect the 1/2 inch discharge line
(schrader valve end) to the remote condenser
fitting marked "discharge line".
8. Connect the other end of the liquid line to
the icemaker fitting marked "discharge line".
9. After all connections are made, and after
the king valve has been opened, check the
couplings for leaks.
FOR THE INSTALLER: Precharged Lines
SCHRADER
VALVE NO SCHRADER
VALVE
TO REMOTE
CONDENSER TO ICEMAKER
3/8" LIQUID LINE
1/2" DISCHARGE
LINE
3/8" LIQUID LINE
1/2" DISCHARGE
LINE
SERVICE PORTS
REMOTE CONDENSER
NM1850R
September, 1992
Page 7

FOR THE INSTALLER: Location
REMOTE
CONDENSER
EXCESS
PRECHARGED
TUBING INSIDE
BUIDLING
ICEMAKER
SERVICE
ACCESS
SERVICE ACCESS
SIDE AND BACK
ROOF
CUTAWAY
WALL
CUTAWAY
CONTACT ROOFING
CONTRACTOR
NM1850R
September, 1992
Page 8

FOR THE PLUMBER
CONFORM TO ALL APPLICABLE CODES
Water Inlet
The recommended water supply is
cold water. Use 3/8" O.D. copper
tubing, connect to the 3/8" male
flare at the back of the cabinet.
Install a hand valve near the
machine to control the water
supply. Drains
There is one 3/4" FPT drain at the
back of the cabinet, the drain line
is of the gravity type, and 1/4 inch
per foot fall is an acceptable pitch
for the drain tubing. There should
be a vent at the highest point of
the drain line, and the ideal drain
receptacle would be a trapped and
vented floor drain. Use only 3/4"
rigid tubing.
Storage Bin: A separate gravity
type drain needs to be run.
Insulation of this drain line is
recommended.
FLOOR DRAIN
VENT BIN DRAIN
3/4" FPT
VENT
ICEMAKER
DRAIN,
3/4" FPT
WATER INLET
3/8" MALE
FLARE
FIELD
SUPPLIED
WATER FILTER
HAND SHUT
OFF VALVE
CONNECT TO
COLD WATER
NM1850R
September, 1992
Page 9

FOR THE ELECTRICIAN
CONFORM TO ALL APPLICABLE CODES
The electrical power to the unit is supplied
through the junction box at the rear of the
machine.
Check the nameplate (located on the back
panel) for the voltage requirements, and for
the minimum circuit ampacity. The machine
requires a solid chassis to earth ground wire.
The ice maker should be connected to its own
electrical circuit so it would be individually
fused. Voltage variation must remain within
design limitations, even under starting
conditions.
Electrically the remote condenser fan motor is
connected to the icemaker at the contactor
terminals for the compressor and the fan
motor operates whenever the compressor
operates.
Electrical connections are made at the
junction box at the back of the icemaker and
at the junction box on the remote condenser.
The remote condenser must be wired to the
icemaker in accordance with local and
national electrical codes with a minimum of 18
Awg. wire with an ground bonding wire
connected to the ground screws provided in
both the condenser and machine field wiring
boxes. All outdoor wiring must be in rainproof
conduit.
All external wiring must conform to
national, state, and local electrical codes.
The use of a licensed electrician is
required to perform the electrical
installation.
TERMINAL STRIP
FOR REMOTE
CONDESNER
ICEMAKER
JUNCTION BOX
POWER
SUPPLY
GROUND
THE
CHASSIS
RAIN PROOF
CONDUIT
NM1850R
September, 1992
Page 10

FOR THE INSTALLER: Completed Installation
INSULATED
PRECHARGED
REFRIGERANT
TUBING
A typical installation should generally appear
as illustrated below. The remote condenser
must be located above the icemaker and the
precharged lines installed per the instructions
on page 6.
NM1850R
September, 1992
Page 11

FOR THE INSTALLER: Final Check List
1. Is the ice system installed
indoors in a location where
the air and water
temperatures are controlled,
and where they do not exceed
the design limitations?
2. Is there an electrical
service disconnect within sight
of the installed machine? Has
the voltage been checked,
and compared to nameplate
requirements?
3. Have all the plumbing
connections been made and
checked for leaks?
4. Has the machine and bin
been leveled?
5. Is there a minimum of 6"
clearance at the rear, left,
right and above the machine
for proper service access?
6. Is the water pressure a
minimum of 20 psig?
7. Has the machine been
secured to the bin?
8. Is there a water shut off
valve installed near the
machine?
9. Is the remote condenser
installed per local building
codes, and in a place where it
has adequate ventilation and
minimal solar heat gain?
10. Has all shipping material
and literature (inside the front
panel) been removed from the
units?
121 Have the remote
condenser and precharged
lines been properly installed?
12. Has the electrical
connection between the icemaker and the
condenser been made?
13. Verify that the master switches are in the
OFF postion.
14. Switch on the electrical power.
15. Refer to Pre-Start instructions, the next
page.
ROOF
HOLES
SEALED?
POWER
SUPPLY?
LEVELED?
PLUMBING?
REMOTE
CONDENSER
SECURED?
NM1850R
September, 1992
Page 12

START UP Pre-Start Inspection
1. Remove the front, left, and right side
service panels.
2. Check that any styrofoam shipping blocks
have been removed.
3. Inspect the interior of the machine for loose
screws or wires. Check that no refrigerant
lines are rubbing each other. Check that the
fan blade turns freely (remote condenser).
4. Check that the refrigerant lines are properly
installed.
5. Check that the electrical power has been
on for at least 12 hours and that the
compressor domes are warm.
6. Check that the unit is installed corerectly
according to the final check list on page 14.
Start Up
1. Go through the pre-start inspection.
2. Open the hand valve, observe that water
enters the water reservoirs, fills the tubes from
the reservoirs to the evaporators, and then
shuts off. Check for leaks.
3. Open each King (receiver service) valve.
4. Switch each master switch on.
The electrical start up sequence is now on
automatic.
A. There should be a short (15 second) delay
before the gearmotor starts.
B. After the gearmotor starts, the liquid line
valve will open, the low pressure control will
close and the compressor will start.
5. The remote condenser fan turns, and the
condenser begins to discharge warm air.
6. The unit should soon be making ice, if
desired the low side pressure of each system
can be checked, it should be 30 psig + or - 4
psig. The discharge pressure will depend
upon air and water temperatures, but should
be between 200 psig and 280 psig.
7. THERE ARE NO ADJUSTMENTS TO
MAKE, so replace the panels.
8. Clean and/or sanitize the storage bin
interior, wipe off the exterior with a clean,
damp cloth.
9 Give the owner/user the service manual,
instruct him/her in the operation of the unit,
and make sure they know who to call for
service.
10. Fill out the manufacturers registration
card, and mail it to the Scotsman Factory.
11. Fill out the field quality audit form, and mail
it to the Scotsman factory.
NM1850R
September, 1992
Page 13

COMPONENT DESCRIPTION
Control Box: Contains the electrical controls
that operate the machine.
High Pressure Cut Out: A manual reset
switch sensing the high side refrigeration
pressure. It is set to shut the machine off at
450 psig.
Evaporator: A vertical stainless steel tube,
refrigerated, and water filled. In it, there is a
stainless steel auger.
Reservoir: Float operated, it maintains the
water level in the evaporator at a constant
level, it also contains the water level sensor.
Water Level Sensor: Senses if there is water
in the reservoir to make ice out of. Will shut
the machine off it there is none.
Ice Discharge Chute: Directs the ice
produced by the evaporator into the storage
bin.
Ice Level Sensor: An electronic "eye", it
senses the presence of ice in the bottom of
the ice discharge chute. Operates to turn the
ice machine on and off automatically as the
level of ice in the bin changes.
Gear Motor: An oil filled, speed reduction
gearbox, driving the auger.
Cleaning Drain Tube: When uncapped and
lowered, drains the evaporator.
Compressor: The refrigerant vapor pump.
Expansion valve: The refrigerant metering
device.
CONTROL BOX
EXPANSION VALVE
WATER LEVEL
SENSOR RESERVOIR
CLEANING
DRAIN TUBE
EVAPORATOR
GEAR MOTOR
ICE LEVEL
SENSOR
HIGH PRESSURE
CUT OUT
COMPRESSOR
ICE CHUTE
NOTE: THERE ARE TWO OF
EACH OF THE LISTED
COMPONENTS IN A FM2400R
HEAD PRESSURE
CONTROL VALVE
NM1850R
September, 1992
Page 14

COMPONENT DESCRIPTION: Control Box
Contactor: A definite purpose contactor
connecting the compressor and the remote
condenser fan motor to the power supply.
Circuit Board: Controlling the ice machine
through sensors and relays. The sensors are:
ice level, and water level. The relays are for
the gear motor (with a built in time delay to
clear the evaporator of ice when the unit turns
off) and for the liquid line valve.
Transformer: Supplies low voltage to the
circuit board.
Pump Down Control: An automatic reset
pressure switch connected to the low side of
the refrigeration system. Controls the
compressor.
Potential Relay: The compressor start relay.
On/Off Switch: Manual control for the
machine.
Prior Models: A manual reset switch was
part of the circuit board. Lights up when the
unit shuts off from the ice discharge chute
being overfilled (opening the microswitch at
the top of the chute) or if the high pressure cut
out switch opens. Not used after July, 1990.
CONTACTOR
ON/OFF SWITCH
PUMP DOWN CONTROL
POTENTIAL RELAY
TRANSFORMER
CIRCUIT
BOARD
There are two control boxes in the machine.
NM1850R
September, 1992
Page 15

Refer the wiring diagram as needed.
The two ice making systems operate
independently except for the fan motor of the
remote condenser. If either one of the systems
is operating, the fan will be ON.
If the machine is switched off at the master
switch, but is otherwise ready to go, switching
the master switch to ON does the following:
••The bin empty light on the circuit board
goes on
••There is a 15 second delay
••If there is enough water in the reservoir, the
circuit board will allow the machine to start
up.
Start up consists of:
••The liquid line relay and auger motor relay
become energized, connecting power to the
liquid line solenoid coil and to the windings
of the auger motor.
••The liquid line solenoid opens, raising the
low side pressure.
••The pump down control closes.
••The auger motor starts, and the centrifugal
switch closes, connecting power to the
compressor contactor coil.
••The contactor is energized, connecting
power to: the compressor and the fan motor
relay.
••The fan motor and the compressor start.
••As ice goes past the ice level sensors, the
bin empty light will stay on, and the
machine will continue to run, unless the ice
stays between the sensors for more than
15 seconds (bin full). At that point, the bin
empty light goes out, and the machine
shuts down.
Shut Down consists of:
••The liquid line solenoid closes, lowering the
suction pressure.
••The pump down control opens.
••The compressor contactor opens
••The compressor and fan motor stop (unless
the other ice making system is on, then the
fan motor stays ON).
••The auger motor is run by the circuit board
for 2.5 more minutes, clearing out ice in the
evaporator, and then
••The auger motor relay opens, and the
auger motor stops.
If the ice level sensor is clear (bin empty) for
more than 15 seconds, the machine will start
up again.
Another purpose of the circuit board is to turn
the machine off if there is not enough water in
the machine.
••When the water level in the reservoir falls
below the water level sensor, the machine
will "shut down"
••When the water refills the reservoir, the
machine will start up again.
Separate from the circuit board:
••The high pressure control will stop the
machine immediately if it opens. It is
manually reset at the control and, on prior
models, at the reset switch on the circuit
board.
••The spout switch will stop the machine
immediately if it opens. It is a manual reset
reset switch. Prior models had an automatic
reset switch.
••A master switch is the manual control for
each system, but it is not a service
disconnect.
ELECTRICAL SEQUENCE
NM1850R
September, 1992
Page 16

OPERATION: Water Water enters the machine through the 3/8"
male flare at the rear of the cabinet, divides
into two inlet lines to each water reservoir
which it enters through the float valve. The
water them goes out the bottom of the
reservoir tanks to the bottom of the
evaporators.
Reservoir overflow or evaporator
condensation is combined into a common
drain line and routed to the drain.
ADJUSTMENT OF WATER LEVEL
EVAPORATOR
DRAIN
WATER
LEVEL
EVAPORATOR
ICE
CHUTE
DRAIN
STRAINER
WATER SCHEMATIC
RESERVOIR
WATER INLET
NM1850R
September, 1992
Page 17

OPERATION: Refrigeration
Beginning at the compressor, the refrigerant
502 is compressed into a high temperature
gas. The discharge line directs this gas to the
condenser. At the remote condenser the
gas is cooled by air and it then condenses
into a liquid. This high pressure liquid then
goes through the liquid line to the head
pressure control valve, into the receiver,
through the liquid line valve and then through
the expansion valve. The thermostatic
expansion valve meters liquid refrigerant into
the evaporator, the volume of liquid refrigerant
depending upon the temperature of the
evaporator; warmer evaporators get more
refrigerant and colder evaporators get less. At
the evaporator, the refrigerant enters an area
of relatively low pressure, where it can easily
"boil off" or evaporate. As it evaporates, it
absorbs heat from the evaporator and
whatever is in contact with it (such as the
water inside it). After the evaporator, the
refrigerant, now a low pressure vapor, goes
through the suction line back to compressor,
where the cycle is repeated.
REMOTE CONDENSER
DETAIL OF HEAD
PRESSURE CONTROL
VALVE
EVAPORATOR
DISCHARGE
LINE LIQUID LINE
HEAD
PRESSURE
CONTROL
VALVE
RECEIVER COMPRESSOR
Refrigeration Schematic
KING
VALVE SUCTION
LINE
THERMOSTATIC
EXPANSION
VALVE
LIQUID LINE
VALVE
There are two separate refrigeration systems in this machine.
NM1850R
September, 1992
Page 18

OPERATION: Refrigeration
Low Condensing Temperature
The refrigeration system under low condenser
air temperatures is much the same as it is
under higher temperatures, with the exception
that the resulting low head pressures cause
the head pressure control to close off the
liquid line between ththe condenser and the
receiver. This forces more refrigerant into the
condenser (with a small amount of discharge
gas going into the receiver to maintain
pressure until the head pressure is built back
up to the rated gauge pressure of 220 psig).
At that pressure the valve opens up the liquid
line from the condenser to the receiver.
LIQUID LINE
VALVE
THERMOSTATIC
EXPANSION
VALVE
SUCTION
LINE
KING
VALVE
Refrigeration Schematic
COMPRESSOR
RECEIVER
HEAD
PRESSURE
CONTROL
VALVE
LIQUID LINE
DISCHARGE
LINE
EVAPORATOR
DETAIL OF HEAD
PRESSURE CONTROL
VALVE
REMOTE CONDENSER
There are two separate refrigeration systems in this machine.
NM1850R
September, 1992
Page 19

OPERATION: Refrigeration PUMP DOWN
During the pump down cycle (usually initiated
by the circuit board de-energizing the liquid
line valve) the discharge gases flow through
their normal path to the remote condenser,
through the head pressure control, and into
the receiver. At this point the refrigerant flow
is stopped by the closed liquid line valve. This
action forces the refrigerant into the receiver
and keeps it out of the compressor. The
pump down continues until the low pressure
control turns the compressor off.
REMOTE CONDENSER
EVAPORATOR
DISCHARGE
LINE LIQUID LINE
HEAD
PRESSURE
CONTROL
VALVE
RECEIVER COMPRESSOR
Refrigeration Schematic
KING
VALVE
SUCTION
LINE
THERMOSTATIC
EXPANSION
VALVE
LIQUID LINE
VALVE
There are two separate refrigeration systems in this machine.
NM1850R
September, 1992
Page 20