Norcold NX61 Manual de usuario

DO NOT install this refrigerator in below deck marine applications. Do not

install this refrigerator in ﬁxed indoor cabin or other dwelling applications. This

refrigerator must use only NORCOLD designed and approved outside air intake

and exhaust ventilation for correct and safe operation. Any other ventilation

could cause lethal combustion exhaust fumes and/or explosive propane gas

fumes to be in the living area and/or below deck.

Publication No. 636104B (27.01.2015)

Service Manual

WARNING

Gas / Electric Refrigerators

MODELS

NX61 / NX81

NX64 / NX84

NX64XIM / NX84XIM

NX64.3 / NX84.3

Questions?/Des questions?/¿Preguntas? 1-800-543-1219

NXA64 / NXA84

NXA64XIM / NXA84XIM

NXA64.3 / NXA84.3

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Refrigerator Service ManualNX6 / NX8 / NXA Models

CONTENTS

Introduction..................................................................................................4

About this Manual...................................................................................4

Model Identification.................................................................................4

Information Label....................................................................................4

Certification and Code Requirements.....................................................4

About Installation....................................................................................4

Replacement Parts.................................................................................4

TechnicalAssistance...............................................................................4

Model Identiﬁcation.....................................................................................5

Cooling Unit Serial Number....................................................................5

SafetyAwareness........................................................................................6

Safety Notice...........................................................................................6

Attention Statements...............................................................................6

Safety Statements...................................................................................6

Speciﬁcations..............................................................................................7

NX61 / NX81, NX64 / NX84, NXA64 / NXA84........................................7

Theory of Operation....................................................................................8

Overview.................................................................................................8

Cooling Unit............................................................................................8

Leveled Operation...................................................................................8

Gradual Decrease in Cooling Efficiency.................................................8

GasAbsorption System..........................................................................9

Electronic Controls................................................................................ 10

ManualAC Mode..................................................................................10

Manual LP Gas Mode............................................................................11

Manual DC Mode (3-way models only)..................................................11

Auto Mode.............................................................................................12

Theory of Operation -

Auto Modes .........................................................................................12

Background Operations........................................................................13

Diagnostic Prechecks................................................................................ 15

Fault Codes...............................................................................................16

NX61 / NX81 Fault Codes.....................................................................16

Solid Red Indicator Light ..............................................................16

Fault / Flash Pattern 1 AC Heater Error.........................................17

Fault / Flash Pattern 2 Service Error.............................................. 17

Fault / Flash Pattern 3

Open High Limit................................................................................17

Fault / Flash Pattern 4

AC Relay Error.................................................................................17

Fault / Flash Pattern 5

Flame On Should Not Be On............................................................18

Fault / Flash Pattern 8

LOW DC (1) Error.............................................................................18

Fault / Flash Pattern 9 LOW DC (2) Error ......................................18

Thermistor Fault .............................................................................19

Door Fault.......................................................................................19

Blank Display..................................................................................19

NX64 / NX84, NXA64 / NXA84 Fault Codes.........................................22

Diagnostic Mode - NX64 / NX84, NXA64 / NXA84....................................26

Screens and Diagnostic Segments Information....................................27

Ventilation..................................................................................................29

Roof Exhaust Venting...........................................................................29

Air Intake Vent.......................................................................................29

Roof Exhaust Vent................................................................................29

Baffles...................................................................................................30

Vertical Enclosures...............................................................................31

Double Sidewall Venting.......................................................................35

Double Side Wall Venting......................................................................36

LP Gas System ......................................................................................... 38

Pressure Requirements........................................................................38

Testing for LP Gas Leaks...................................................................... 38

Components..........................................................................................39

FlameAppearance................................................................................41

Burner Cleaning Procedure..................................................................42

Gas Lockout.......................................................................................... 44

Reset a Gas Lockout Condition -All Models.........................................44

NX61 / NX81, NX64 / NX84, NXA64 / NXA84 Gas Safety Valve Test:.44

Electrical Requirements and Components................................................45

DC Voltage Requirements and Polarity................................................45

DC Power Wiring Requirements...........................................................45

AC/DC Converter as Power Source...................................................... 45

AC Power Requirements......................................................................46

12VDC Ventilation Fan..........................................................................47

LowAmbient Heater (optional)..............................................................48

Cooling Unit............................................................................................... 48

Cooling System Monitoring...................................................................48

Troubleshooting Cooling Faults............................................................49

Refrigerant Leakage.............................................................................49

Disposal of Cooling Unit........................................................................49

Cooling System Diagnostic Flowchart..................................................50

Electrical Requirements and Components............................................52

Modes of Operation - NX61, NX81 ...........................................................54

Start Up:................................................................................................ 54

Shut Down:...........................................................................................54

Modes of Operation - NX64 / NX84, NXA64 / NXA84 ..............................55

Start Up:................................................................................................ 55

2-way Model Mode Indicators...............................................................55

3-way Model Mode Indicators...............................................................55

Shut Down:...........................................................................................56

NX64 / NX84, NXA64 / NXA84 Display Codes.........................................56

Ice Maker...................................................................................................57

Wire Harness........................................................................................57

Fill Tube ................................................................................................57

Water Valve...........................................................................................57

Specifications........................................................................................57

Ice Maker Troubleshooting Chart.......................................................... 58

Replacing the Ice Maker.......................................................................58

Cycle Test .............................................................................................59

Water FillAdjustment............................................................................60

Low Ice Yield......................................................................................... 60

Water Valve OperationTest ..................................................................60

Water Valve Solenoid Resistance......................................................... 60

Mold Heater Resistance Check............................................................61

Checking Voltage at Motor Terminals...................................................61

Winterizing the Ice Maker Water...........................................................61

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NX6 / NX8 / NXA ModelsRefrigerator Service Manual

Table of Contents - cont’d.

Figures

Fig. 1 - Refrigerator Information Label Location ..............................5

Fig. 2 - Cooling Unit Bar Code

Label Location....................................................................................5

Fig. 3 - GasAbsorption System........................................................9

Fig. 4 - Flash Patterns.................................................................... 16

Fig. 5A - Thermistor ....................................................................... 19

Fig. 5B - Thermistor in Ice.............................................................. 19

Fig. 6 - NX61 / NX81, NX64 / NX84, NXA64 / NXA84 Continuous 12-

Volt ...................................................................................................21

Fig. 7 - NX61 / NX81, NX64 / NX84, NXA64 / NXA84 Switched

12-Volts ............................................................................................21

Fig. 8 - NX64 / NX84, NXA64 / NXA84 Display Board ..................26

Fig. 9 - Diagnostic LEDs Segments Identification ..........................26

Fig. 10 - Roof Exhaust VentingArrangement. ...............................29

Fig. 11 - Rear View–Roof Exhaust Venting ....................................30

Fig. 12 - Baffles Req. for Inboard Roof Exhaust Vent Installation... 30

Fig. 13 - Vertical Enclosure Depth of 24 > 26 Inches ....................31

Fig. 14 - Vertical Enclosure Depth of 26 > Inches .........................32

Fig. 15 - Offset Vertical Enclosure Depth of 24 > 25 Inches .......... 33

Fig. 16 - Offset Vertical Enclosure Depth of 26 > Inches ............... 34

Fig. 17 - Double Side Wall Enclosure Depths of 24 > 26 Inches ... 36

Fig. 18 - Double Side Wall Enclosure Depth of 26 > Inches ..........37

Fig. 19 - LP Gas System Components........................................... 38

Fig. 20 - Solenoid Gas Valve..........................................................39

Fig. 21 - LP15 OrificeAssemblies ..................................................40

Fig. 22 - Burner............................................................................... 40

Fig. 23 - Burner Tube...................................................................... 40

Fig. 24 - Flue and Components...................................................... 41

Fig. 25 - Flue Baffle........................................................................ 41

Fig. 26 - FlameAppearance...........................................................41

Fig. 27 - Drip Cup and Burner Box Cover.......................................43

Fig. 28 - Burner and Components................................................. 43

Fig. 29 - DC Heater ........................................................................45

Fig. 30 -AC and DC Heaters (3-way refrigerator).......................... 46

Fig. 31 - Lamp/ThermistorAssembly..............................................46

Fig. 32 -AC Heater.........................................................................46

Fig. 33 -AC Power Cord................................................................. 47

Fig. 34 - Fan Mounted on Top ofAbsorber Coil..............................47

Fig. 35 - Fan Thermostat................................................................ 47

Fig. 36 - Fan with Installed NORCOLD Fan Kit.............................. 48

Fig. 38 - Wiring Diagram and Pictorial-LowAmbient Heater.......... 48

Fig. 37 - NORCOLD Fan Kit Wiring Pictorial................................. 48

Fig. 39 - Reset Pushbutton.............................................................48

Fig. 40 - Cooling System Diagnostics............................................. 50

Fig. 41 - Wiring - NX61 / NX81, NX64 / NX84, NXA64 / NXA84.... 52

Fig. 42 - Wiring - NX61 / NX81, NX64 / NX84, NXA64 / NXA84.... 53

Fig. 43 - NX61, NX81 Display Board.............................................. 54

Fig. 44 - NX64 / NX84, NXA64 / NXA84 Display Board ................ 55

Fig. 45 - Ice Maker.......................................................................... 57

Fig. 46 - Ice Maker Mounting Hardware......................................... 58

Fig. 47 -Test points Land N............................................................59

Fig. 48 - Test pointsT and H...........................................................59

Fig. 49 - Water FillAdjustment Screw and Indicator.......................59

Fig. 50 - Energize water valve through test points V and L............ 60

Fig. 51 - Measure water valve solenoid resistance ........................60

Fig. 52 - Measure mold heater resistance...................................... 61

Fig. 53 - Check voltage to motor ................................................... 61

Fig. 54 - NX64IM / NX84XIM, NXA64IM / NXA84XIM – Ice Maker

Wired to RefrigeratorAC Cord..........................................................62

Fig. 55 - NX64IM / NX84XIM, NXA64IM / NXA84XIM – Ice Maker

Wired to Unit Refrigerator Cord........................................................62

Tables

Table 1: Temperature Set Points NX61 / NX81 ....................................14

Table 2: Temperature Set Points NX64 / NX84, NXA64 / NXA84.......................14

Table 3: Clearances for Roof Vented Installations................................30

Table 4: NX61, NX81 Operation Modes................................................ 54

Table 5: NX64 / NX84, NXA64 / NXA84 Operation Modes...................55

Table 6: NX64 / NX84, NXA64 / NXA84 Display Codes.......................56

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Refrigerator Service ManualNX6 / NX8 / NXA Models

About this Manual

This service manual provides maintenance, diagnostic, and

repair information for NORCOLD®models NX61 / NX81,

NX64 / NX84, NXA64 / NXA84 gas absorption refrigerators.

It is a reference tool designed for technicians who are

knowledgeable in the theory and operation of gas/electric

absorption refrigerators, liqueﬁed petroleum (LP) gas–

propane–systems, and AC/DC electrical systems as installed

in a variety of recreational vehicles (RV).

All information, illustrations, and speciﬁcations contained in

this publication are based on the latest product information

available at the time of publication. NORCOLD®reserves the

right to make changes at any time without notice.

Model Identiﬁcation

Models NX61, NX81, NX64, NXA64, NX84 and NXA84 are

2-way refrigerators that operate on AC power or LP gas.

Models NX64.3, NXA64.3 and NX84.3 and NXA84.3 are 3-way

refrigerators, that operate on AC power, LP gas, or DC power.

Letter(s) appended to the model number identify factory

installed accessories. See Fig. 1.

Information Label

The information label is located in the upper right corner of the

fresh food compartment just below the divider. See Fig. 1. The

label provides the following information:

• Serial number.

• Model number.

• LP gas (propane) pressure.

• Btu/h.

• AC voltage and amperage.

• DC voltage and amperage.

• Design certiﬁcation.

• Vent kit requirement.

INTRODUCTION

Certiﬁcation and Code Requirements

NORCOLD®NX6X / NX8X, NXA6X / NXA8X gas/electric

absorption refrigerators are certiﬁed under the latest edition

of ANSI Z21.19B standards for installation in mobile homes

or recreational vehicles, and with the Canadian Standards

Association CAN/CGA-1.4-M94.

Electrical components are compliant.

About Installation

Refrigerator installation must conform with the NX6/NX8

Installation Manual for the NORCOLD®limited warranty to be

in effect. Installation must also comply with applicable local

codes and standards set by the relevant certiﬁcation agency.

Replacement Parts

Use only authorized NORCOLD®replacement parts.

Generic parts do not meet NORCOLD®speciﬁcations for

safety, reliability, and performance. The use of unauthorized

aftermarket or generic replacement parts voids the

refrigerator's limited warranty coverage.

Technical Assistance

If unable to resolve technical issues using the information

provided in this manual, technical support is available through

NORCOLD®Customer Service Center:

Telephone: 1-800-444-7210

Fax: 1-734-769-2332

World Wide Web: www.norcold.com

The following information is required to process technical

support requests; refer to the following page:

• Refrigerator Model Number

• Refrigerator Serial Number

• Refrigerator Cooling Unit Serial Number

• Recreational Vehicle (RV) Make/Model/Year

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NX6 / NX8 / NXA ModelsRefrigerator Service Manual

Fig. 1 - Refrigerator Information Label Location

MODEL IDENTIFICATION

xxxxxxxxxxxxxxxxxxxxxxxxxxx

xxxxxxxxxxxxxxxxxxxxxxxxx

xxxxxxxxxxxxxxxxxxx

xxxxxxxxxxxxxxxxxxxxxxxxx

xxxxxxxxxxxxxxxxxxxxxxx

NORCOLD

Serial Number

Model Number

x.xx

LBS.

test pressure

xxx VOLTS - AC xx HZ

x.xx AMPS xxx Watts

xx VDC xx HZ

x.x AMPS xx xx Watts

Group Code

Input Pressure

BTUH

Refrigerant

Certied

Explanation

1N = Norcold

2X = Sequence number indicating custom features

36 or 8 = Approximate storage volume in cubic feet

4X = Sequence number indicating custom features

5Models available. Blank = 2-Way operation, .3=3-Way operation

6Icemaker unit. Blank = does not have ice maker, IM = has icemaker

7Blank = Is not equipped for low ambient operation, C = Is equipped for low ambient operation

8Door design: Blank: Insert panel doors, SS: Stainless steal wrapped, BK: Black wrapped, WH:

White wrapped, WPM: Pewter Royce wrapped

9Fan: Blank: No fan, F = Equipped (1) Fan, F2 = Equipped (2) Fans, V = Equipped (1) High

Velocity Fan

10 Door swing: L = Left-hand door swing, R = Right-hand door swing

11 P=Black acrylic door panels

12 Packaging Type: Blank: Corrugated packaging, T = Returnable packaging tray, M6 = 6-unit

multi-pack

NX610.3 IM C BK X R P T

xxxxxxxxxxxxxxxxxxxxxxxxxxx

xxxxxxxxxxxxxxxxxxxxxxxxx

xxxxxxxxxxxxxxxxxxx

xxxxxxxxxxxxxxxxxxxxxxxxx

xxxxxxxxxxxxxxxxxxxxxxx

ORCOLD

Serial Number / Model Number Location

A. Serial Number

B. Model Number

C. Group Code

D. BTu/h

E. Amount of refrigerant in cooling

unit

F. AC Voltage/amperage

G. DC Voltage/amperage

Fig. 2 - Cooling Unit Bar Code

Label Location.

Be sure to have the cooling unit serial

number available if you need technical

support on this component.

1167359

NORCOLD

Cooling Unit Bar Code Location

Cooling Unit Serial Number

The cooling unit serial number appears on the cooling unit bar

code label. The label is afﬁxed to the surface of the cooling

unit leveling chamber.

Note: The actual refrigerator label speciﬁes the features applicable to that unit.

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Refrigerator Service ManualNX6 / NX8 / NXA Models

Safety Statements

Do not modify, alter, or equip the refrigerator to the use

of any other fuel (natural gas, butane, etc.). NX6X/NX8X,

NXA6X, NXA8X refrigerators are designed and equipped

for the use of LP gas–propane gas–only.

Incorrect installation, adjustment, alteration, or maintenance

of the refrigerator can cause personal injury, property

damage, or both.

Do not smoke, light ﬁres, or create sparks when working on

the propane gas system.

Do not use an open ﬂame for leak testing any of the

propane gas system components. Propane gas is highly

ﬂammable and explosive.

Always use two wrenches to tighten or loosen LP

gas connections. Damaged connections, piping, and

components create the potential for gas leaks.

All electrical connections and repairs to the refrigerator

must comply with all applicable codes. Refer to the

certiﬁcation and code requirements section of the NX6X/

NX8X Installation Manual.

Do not work on live electrical circuits. Turn off AC power

and DC power sources before attempting to remove,

service, or repair any of the refrigerator's electrical or

electronic components.

Do not modify, bypass, or eliminate any of the refrigerator's

electrical components, electronic circuits, or propane gas

system components.

Do not wet or spray liquids on or near electrical

connections or electronic components. Most liquids,

including leak detection solutions, are electrically

conductive and pose the potential for an electric shock

hazard, short electrical components, damage electronic

circuits, and/or ignite a ﬁre.

Do not use leak test solutions that contain ammonia or

chlorine. Ammonia and chlorine degrade copper and brass

components.

The cooling unit is a sealed system under pressure! Do

not try to repair or recharge the cooling unit. Do not bend,

drop, weld, drill, puncture, saw, or strike the cooling unit.

Handle a leaking cooling unit with extreme caution!

The cooling unit contains ammonia, hydrogen, and sodium

chromate. Ammonia can cause severe skin and eye burns.

Hydrogen is highly ﬂammable, can ignite and burns with

an intense ﬂame. Certain chromium compounds, such as

sodium chromate, are carcinogenic.

Do not use extension cords. Do not remove the grounding

prong from the refrigerator AC power cord. Do not use a

two prong adapter to connect the refrigerator to the AC

outlet.

Do not over-fuse electrical circuits. Use speciﬁed fuses and

AWG wire sizes. The speciﬁcation section of this manual

provides fuse size information. Refer to the NX6XNX8X

Installation Manual for the correct AWG wire size

speciﬁcations.

Prevent child entrapment! Before disposing of the

refrigerator, remove all doors and fasten all shelves with

retainers.

Some of the refrigerator's metal components have sharp

corners and edges. Wear hand protection, such as cut

resistant gloves, and exercise extreme care when handling

the refrigerator.

Make sure all hardware such as hinges and fasteners

(retaining screws, etc.), are properly fastened.

SAFETY AWARENESS

Safety Notice

It is not possible to anticipate all of the conceivable ways

or conditions under which the refrigerator may be serviced

or to provide cautions as to all of the possible hazards that

may result. Standard and accepted safety precautions and

equipment should be used when working on electrical circuits

and handling toxic or ﬂammable materials. Safety goggles and

other required protection should be used during any process

that can cause material removal, such as when removing a

leaking cooling unit and cleaning components.

Attention Statements

The safety alert symbol

followed by the word WARNING or

CAUTION identiﬁes potential safety hazards or conditions.

The safety alert symbol with the appropriate heading appears on

all safety labels posted on the refrigerator and safety awareness

notices presented throughout this manual.

CAUTION

The above heading identifies hazards, which if

ignored can cause injury and/or property damage.

WARNING

The above heading identiﬁes hazards or conditions,

which if ignored can cause serious injury, death, and/

or extensive property damage.

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NX6 / NX8 / NXA ModelsRefrigerator Service Manual

SPECIFICATIONS

NX61 / NX81, NX64 / NX84, NXA64 / NXA84

NX61 / NX81 - Electronic

• Push Button - On/Off, Mode, and Temperature Set

• LED Indicator Lights

• Self-Diagnostic with Fault Indicators

• 2-Way Operation

• Three Separate Temperature Settings (With Backup Operating System Mode)

• Sleep Mode

NX64 / NX84, NXA64 / NXA84 - Electronic

• Push Button - On/Off, Mode, and Temperature Set

• Backlit LCD (Liquid Crystal Display) with Icon Indicators

• Self-Diagnostic with Fault Codes

• 2-Way Operation (Standard), 3-Way Operation (Optional)

• Nine Separate Temperature Settings (With Backup Operating System Mode)

• 10 Individual Diagnostic Screens

• Sleep Mode

Rough opening dimensions (H x W x D)

NX6XX, NXA6XX ---------------------------------------------------------------------------------------52

7/8 in. x 23 1/2 in. x 24 in.

NX8XX, NXA8XX ---------------------------------------------------------------------------------------59 7/8in. x 23

1/2in. x 24 in.

Decorative panels dimensions

Thickness ------------------------------------------------------------------------------------------------------------------------- 3/16 in.

Freezer door (H x W, both models) ----------------------------------------------------------------15 11/16 in. x 21 19/32 in.

Upper panel ---------------------------------------------------------------------------------------------15 11/16 in. x 21 19/32 in.

Fresh food compartment (H x W)

NX61 / NX64 / NXA64 ------------------------------------------------------------------------------ 32 25/32 in. x 21 19/32 in.

NX81 / NX84 / NXA84 ------------------------------------------------------------------------------- 39 25/32 in. x 21 19/32 in.

DC power

DC input voltage requirements --------------------------------------------------------------------------- 10.5VDC to 15.4VDC

DC Fuse, F1 on Power Board --------------------------------------------------------Automotive Blade, Type APR-5A-Tan

DC Fuse, F1 on optional DC Board --------------------------------------------Automotive Blade, Type APR-30A-Green

DC Heater (Optional) ------------------------------280W/14VDC, (0.67to 0.73), Current 16A to 18A @ 12VDC

Divider Heater ------------------------------------ 3.1W/12VDC, (43to 50), Current 240mA to 279mA @ 12VDC

Gas Valve --------------------------------------- 1.75W/12VDC, (74to 92), Current 130mA to 162mA @ 12VDC

Interior Light-------------------------------------------------GE #214, Miniature Automotive Light Bulb, ½ A @ 13.5VDC

AC power

AC input voltage requirements ------------------------------------------------------------------------------108VAC to 132VAC

AC Fuse, F2 on Power Board ------------------------- AGC Series, 8A, Fast Acting, Glass Tube (1/4 in. x 1-1/4 in.)

AC Heater--------------------------------------------- 300W/120VAC, (46to 51), Current 2.3A to 2.6A @ 120VAC

LP gas (propane)

Operating pressure (Input pressure to gas valve) ------------------------------------------------- 10.5 in. to 11.5 in. W.C.

Burner rating (Heat output)--------------------------------------------------------------------------- 1420 Btu/h @ 11 in. W.C.

Burner oriﬁce size ----------------------------------------------------------------------------------------------------------------- LP15

Gas ignition------------------------------------------------------------------------------------------ Electronic with ﬂame sensing

Electrode tip-to-burner gap---------------------------------------------------------------------------------------1/8 in. to 3/16 in.

Off-level operating limits

Side-to-side------------------------------------------------------------------------------------------------------3 degrees-maximum

Front-to-back----------------------------------------------------------------------------------------------------6 degrees-maximum

Temperature Sensor ---------- ---------------------------------------- Thermistor, Fin mounted (10th ﬁn from the right)

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Refrigerator Service ManualNX6 / NX8 / NXA Models

THEORY OF OPERATION

The NX6X/NX8X MODEL gas absorption refrigerators are

comprised of two separate systems that together allow the

refrigerator to cool. When performing service it is important

to have a basic understanding of each system and their

interaction with one another and how this interaction provides

for cooling/refrigeration.

These two “systems” are the:

• Cooling Unit

• Refrigerator Controls (Electronic Controls)

Overview

Cooling Unit

The cooling unit is a self-contained gravity ﬂow absorption

refrigeration system. The refrigerant charge is a solution of

water, ammonia, sodium hydroxide, and sodium chromate.

In order to produce cooling a precise heat must be applied to

the boiler area which in turn initiates a chemical reaction that

extracts heat from the freezer and fresh food compartments,

thus providing "cooling."

This precise heat is supplied to the cooling unit via heaters

and/or a LP gas burner which are controlled by the

refrigerators electronic controls. The refrigerant transfers the

heat from the freezer and fresh food cabinets to the absorber

coils. At the absorber coils the metal surface absorbs the heat

and air ﬂow over the external surfaces of the coils carries

the heat away. A more detailed description of the absorption

process can be found under the heading “Cooling Unit

Detailed Description" on the following pages.

A thermal air current created by the rising hot air ﬂows out of

the enclosure through either a roof exhaust vent or a sidewall

exhaust vent (depending on installation). The ﬂowing air

mass passes over the surface of the condenser ﬁns where it

absorbs heat transferred from the ammonia vapors ﬂowing

through the condenser. The thermal airﬂow process creates

a "chimney effect" that creates a continuous draft of cooling

and combustion air. The fresh air drafted by the chimney effect

removes rejected heat, supports combustion, and expels

the exhaust gases produced by the combustion process.

Obstructions, restrictions, or modiﬁcations to vents or the

enclosure will affect the heat absorption cycle. Poor cooling

unit performance may be due to:

• Loose insulation interfering with the ventilation process

• Construction material or debris left in the enclosure

• Insect screen covering vents

• Plastic sheeting covering vents

• Items stored in the enclosure

• Modiﬁcations to vents or enclosure

• No roof or sidewall vent openings

Leveled Operation

The circulation of the refrigerant through the cooling unit is

accomplished by gravity ﬂow; therefore, the refrigerator must

be operated leveled. Off-level operation affects the ﬂow of the

refrigerant through the cooling system. The maximum off-level

operation limits are:

• 3° (Degrees) from side-to-side

• 6° (Degrees) from front-to-back

Exceeding the maximum off-level limits can permanently

damage the cooling unit. The cooling unit or its performance is

not affected when the vehicle is in motion.

Gradual Decrease in Cooling Efﬁciency

A gradual decrease in cooling efﬁciency is not a clear

indication of cooling system failure. Other factors that affect

cooling efﬁciency include ventilation, the heat input, off-level

operation, lack of service and maintenance, inadequate

repairs, or unauthorized ﬁeld modiﬁcations. If any of these

factors exist and are not corrected, a replacement cooling

unit will also perform inefﬁciently or fail. Step-by-step

troubleshooting is the best approach when dealing with

a gradual decrease in cooling. It is important to consider

that, though not efﬁciently, the cooling unit is working.

Troubleshooting should always begin by checking ventilation,

then thoroughly checking the cooling unit, and heat sources.

In the majority of reported cases, the problem is related to

the installation, which in turn hinders cooling unit ventilation.

Additionally, ambient air temperature plays a signiﬁcant role

if the unit is not installed correctly. Incorrect installation can

lead to poor ventilation, which in turn relates to poor cooling

performance.

The unit's service and maintenance history should be

considered when checking a cooling unit for poor cooling

performance. The service history and the scope of service

work performed may lead directly to cause and resolution

of a cooling problem. The cooling unit has to reach normal

operating temperatures before troubleshooting can take place.

It takes an average of four hours for the refrigerant to reach

normal operating temperatures. The time frame to reach

operating temperatures depends on ambient air temperature.

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NX6 / NX8 / NXA ModelsRefrigerator Service Manual

Theory of Operation - cont’d.

A rich solution (RS) leaves the absorber vessel and passes

through the liquid heat exchanger to the bottom of the pump

tube. Utilizing a cartridge type heater (AC or DC) or a LP

gas burner, a precise heat is applied to this area which in

turn causes the temperature of the solution to rise. This

temperature increase causes ammonia and some water

vapor to be driven out of the solution, forming vapor bubbles

which push columns of liquid up the pump tube.

As these columns of liquid exit the pump tube the liquid falls

downward through the rectiﬁer where the temperature is

increased causing additional ammonia vapor to be released.

The remaining liquid, now a weak ammonia-water solution

(WS), ﬂows through the external shell of the liquid heat

exchanger where it transfers its residual heat to the rich

solution (RS) and enters the top of the absorber coil at a

reduced temperature. The ammonia-water vapor passes

through the water separator whose reduced temperature

causes any water vapor to condense and drop back down to

the boiler mixing with the existing weak solution (WS). The

ammonia vapor (AV) rises and enters the condenser where

it condenses (liqueﬁes) into pure liquid ammonia (LA). The

liquid ammonia, via gravity, drops into the tubular coil of the

freezer and cabinet evaporators and wets the internal surface

of the tubes.

The weak ammonia-hydrogen gas that was previously

released at the top of the absorber coil passes over the

wetted surfaces of the evaporator tubing causing the liquid

ammonia to evaporate into the hydrogen. The now rich

ammonia-hydrogen gas mixture (RG) draws heat from inside

the refrigerator. The weight of the hydrogen-ammonia gas

mixture (RG) is heavier than that of the weak gas (WG).

Consequently, it falls through the gas heat exchanger into the

top of the absorber vessel. From this point it enters the bottom

of the absorber coil.

The rich ammonia-hydrogen gas mixture (RG) travels up

through the absorber and makes contact with the weak

solution (WS) traveling down from the top of the absorber. As

the weak solution (WS) drops through the absorber it absorbs

the ammonia from the rich ammonia-hydrogen gas mixture

(RS). The relatively pure hydrogen (WG) exits the top of the

absorber coils to the evaporator and the rich solution falls to

the bottom of the absorber vessel where the cycle starts again.

Gas Absorption System

Fig. 3 - Gas Absorption System

www.norcold.com/cda

Refrigerator Service ManualNX6 / NX8 / NXA Models

Electronic Controls

A precise heat is applied to the boiler area of the cooling

unit causing a chemical reaction within the cooling unit that

ultimately results in the refrigerator cooling. The heat applied is

done so by means of:

• Cartridge type heaters (AC or DC heaters)

positioned in heater wells welded to the surface of

the boiler

• LP Gas burner positioned below the boiler such

that the heat from the ﬂame is directed across the

surface of the boiler

These heat sources are turned on/off via the combination of

the electronic controls and a temperature sensor located inside

the refrigerator fresh food compartment. A temperature setting

is set at the electronic controls and as the temperature sensor

warms and cools the heat source is turned on/off accordingly.

This process of turning on/off the heat source(s) can be

accomplished in various operating modes. These operating

modes are:

• Manual AC Mode - While operating in this mode

the AC cartridge type heater is operated to provide

heat to the boiler area of the cooling unit (2-way &

3-way models)

• Manual LP Gas Mode - While operating in this

mode the LP Gas burner is operated to provide

heat to the boiler area of the cooling unit (2-way &

3-way models)

• Manual DC Mode - While operating in this mode

the DC cartridge type heater is operated to provide

heat to the boiler area of the cooling unit (3-way

models only)

• Auto Mode - While operating in this mode the

electronic control will automatically select the

mode to be utilized. It will attempt to operate the

heat source requirements in the following order of

priority (All models):

• 1st Priority Choice - AC Electric (AC cartridge

type heater)

• 2nd Priority Choice – LP gas (LP Gas Burner)

• 3rd Priority Choice – (3-way models only) - DC

Electric (DC cartridge type heater)

Dependent upon the model number NX6X/NX8X refrigerators

are either considered 2-way or 3-way model refrigerators

(See Model Identiﬁcation section of this manual). 2-way

refrigerators are capable of operating priority choices 1 and/

or 2 via separate Manual Modes or an Automatic Mode. 3-way

refrigerators are capable of operating all 3 priority choices via

separate Manual Modes or an Automatic Mode.

The mode of operation and temperature setting is selected

via the optical display assembly located on the front of the

refrigerator. A thermistor is mounted on the ﬁn assembly

located inside the fresh food compartment. The thermistor

acts as a temperature sensor, reporting the temperature

sensed to the optical display. The optical display then relays

this information to the power board that then turns on/off the

appropriate heat source accordingly. The optical display board,

power board, thermistor, and other components within the

refrigerator are interconnected via a wire harness.

Manual AC Mode

To operate in the Manual AC mode the optical display must be

placed to operate in this mode. Once done so, the refrigerator

will cool via the AC mode and ONLY the AC mode. While in

the AC mode the refrigerators electronic controls will function

as follows:

The power board is responsible for:

• Measuring the AC input voltage

• Measuring the AC heater current

• Measuring the resistance value of the thermistor

• Turning ON/OFF the AC heater output

• Communicating with the Optical Display Board

The optical display board is responsible for:

• Determining if the AC input voltage is available or

not available

• Determining if the AC heater current is acceptable

or not acceptable

• Determining if the thermistor value is above or

below preset temperature range cut-in/cut-out

values

• Determining when the power board is to turn ON/

OFF the AC heater output

• Communicating with the Power Board

AC voltage is applied to the power board via the AC power

cord at terminals L1 (Hot) and L2 (Neutral). This AC voltage

passes through the AGC Series, 8A, Fast Acting, Glass Tube

Fuse (F2) where it is then measured. This measurement is

communicated to the optical display board which determines

if the applied voltage is below or above 85VAC. If the voltage

is above 85VAC, the determination is that AC voltage is

available. If not, it is determined that AC voltage is not

available and the appropriate voltage related fault will be

displayed on the optical display.

• NX61 / NX81 = Power ON indicator is Solid RED

• NX64 / NX84 = "no AC" with audible alarm/beeper

• NXA64 / NXA84 = "no AC" with audible alarm/

beeper

The power board also measures the thermistor value and

reports it to the optical display board. The thermistor, a

temperature device whose internal resistance goes down as

the temperature goes up, is connected to the power board via

terminals P2-1 and P2-6. The optical display board compares

the actual thermistor value to preset cut-in and cut-out

temperature values for each of the particular temperature

settings. Should the thermistor value fall below a particular

cut-in value it will request the power board to turn ON the AC

heater relay (K2). Should the thermistor value go above a

particular cut-out value it will request the power board to turn

OFF the AC heater relay.

Any time relay K2 is turned ON, AC voltage is applied to

the AC heater via the now closed K2-contacts. Any time AC

voltage is applied to the AC heater, an AC current is produced.

Theory of Operation - Manual AC Mode

Theory of Operation - cont’d.

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