Scotsman NM1852R 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 NM1852R 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-22 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 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
Start Up . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
Component Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
Maintenance & Cleaning . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
Service Diagnosis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
Removal and Replacement
Water Reservoir & Bin Controls . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28
Thrust Bearing & Breaker . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
Auger . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30
Water Seal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31
Evaporator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32
Gearmotor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33
Refrigeration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34
Circuit Board Testing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35
Parts Lists and Wiring Diagrams are located in the center of this manual, printed on yellow
paper.
NM1852R
December 1992
Page 1

FOR THE INSTALLER
The NM1852R 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 (RC1222).
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
NM1852RE-32A
NM1852RE-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
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
NM1852R
December 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
NM1852R
December 1992
Page 3

REMOTE CONDENSER SPECIFICATIONS
22"
27.81"
19.86"
5.75"
1/2" MALE QUICK CONNECT
COUPLING FOR USE WITH
RT2225 OR RT2240
PRECHARGED LINE SET
LIQUID LINE 3/8" MALE
QUICK CONNECT
COUPLING FOR USE WITH
RT2225 OR RT2240
PRECHARGED LINE SET
3.5" 6.5"
1.9"
5.0"
5.38"
7.5"
32.56"
RT-2225 Precharged line set, 25’, R-22 - 2 required.
Or: RT-2240. Precharged line set, 40’, R-22 - 2 required.
DIMENSIONS
H" X W" X D"
MODEL USE WITH MINIMUM CIRC.
AMPACITY+ BASIC ELECTRICAL
RC1222 27.8" X 22 X 37.94" 1 NM1852R 2 208-230/60/1
+Included with the ice maker’s 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
NM1852R
December 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.
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
NM1852R
December 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, next 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.
Note: Tight spiral shown not required. Bend tubing
as tight as is practical.
Refrigerant charge is in the ice machine receiver.
Only a holding charge is in the "pre-charged" lines.
REMOTE CONDENSER
LOCATE REMOTE
CONDENSER
ABOVE ICEMAKER
SPIRAL
EXCESS
TUBING
INSIDE
BUILDING
NM1852R
December 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,
••Connect the 3/8 inch liquid line (schrader valve
end) to the remote condenser fitting marked
"liquid line".
••Connect the other end of the liquid line to the
icemaker fitting marked "liquid line."
••Connect the 1/2 inch discharge line (schrader
valve end) to the remote condenser fitting
marked "discharge line".
••Connect the other end of the liquid line to the
icemaker fitting marked "discharge line".
4. 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.
5. 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.
6. 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
NM1852R
December 1992
Page 7

FOR THE INSTALLER: Location
REMOTE
CONDENSER
EXCESS
PRECHARGED
TUBING INSIDE
BUILDING
ICEMAKER
SERVICE
ACCESS
SERVICE ACCESS
SIDE AND BACK
ROOF
CUTAWAY
WALL
CUTAWAY
CONTACT ROOFING
CONTRACTOR
NM1852R
December 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
NM1852R
December 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 rain proof 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
CONDENSER
ICEMAKER
JUNCTION BOX
POWER
SUPPLY
GROUND
THE
CHASSIS
RAIN PROOF
CONDUIT
NM1852R
December 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.
NM1852R
December 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?
11 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 position.
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?
NM1852R
December 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 correctly
according to the final check list on page 12.
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 25 psig + or - 2 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.
NM1852R
December 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 400 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 NM1852R
HEAD PRESSURE
CONTROL VALVE
NM1852R
December 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.
CONTACTOR
ON/OFF SWITCH
PUMP DOWN CONTROL
POTENTIAL RELAY
TRANSFORMER
CIRCUIT
BOARD
There are two control boxes in the machine.
NM1852R
December 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
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 .
••The spout switch will stop the machine
immediately if it opens. It is a manual reset
reset switch.
••A master switch is the manual control for each
system, but it is not a service disconnect.
ELECTRICAL SEQUENCE
NM1852R
December 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
NM1852R
December 1992
Page 17

OPERATION: Refrigeration
Beginning at the compressor, the refrigerant 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.
NM1852R
December 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
the 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.
NM1852R
December 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.
NM1852R
December 1992
Page 20