MORTEX G18D SERIES User manual

MORTEXPRODUCTSINC501TERMINALRDFORTWORTH,TX76106Page1
INSTALLATION MANUAL
DOWNFLOW ONLY GAS FURNACE
SIZES 60, 70, 77, 90
MODELS: G18D SERIES CATEGORY I MOBILE HOME GAS FURNACE
LIST OF SECTIONS
1 – Safety 1 6 – Combustion Air and Vent System 19
2 – General Information 5 7 – Furnace Startup, Diagnostics and Sequence of Operation 27
3 – Furnace Duct connections and Duct System 8 8- Blower Performance 32
4 – Gas Supply and Valve Connections 10 9 – Wiring Diagrams 33
5 – Line and Low Voltage Wiring 14
LIST OF FIGURES
1 - Furnace Dimensions 7 18 – Typical Single Stage Heat / Cool Digital T’stat 2 Stage Furnace 18
2 – Duct Connector Dimensions 8 19 – Typical 2 Stage Heating/Cooling Digital T’stat Connections 18
3 – Duct Connector and Floor Base Installation 8 20 – Roof Jack Mounting Collars – Top of Furnace 20
4 – Air Distribution System – Single Trunk Duct 9 21 – Roof Jack Indoor Extension Pipes 20
5 – Air Distribution System – Double Trunk Duct 9 22 – Roof Jack Outdoor Extension Pipes 20
6 – Air Distribution Systems – Graduated trunk duct 9 23 – Roof Jack Assembly (Slope Saddle) 21
7 – Furnace Base Openings, Fuel, Electric & A/C Line Penetrations 9 24 – Roof Jack Crown Assembly 21
8 – Duct Connector Depths 9 25 – Combustion Air Path thru the Roof Jack & Thru the Pipes 22
9 - Outdoor Fresh Air Intake Knockout 10 26 – Outside Ambient Combustion Air Openings and Ducts 23
10 – White Rodgers 36J29 Gas valve 11 27 – Home Layout and Vent Clearances 24
11 – Supply Gas Piping 11 28 – Outside Combustion Air and Vent Safety Check Procedure 25
12- Furnace Component Locations 16 29 – Typical Roof Jack Installation 26
13 – Separate T’stat, Furnace & Cooling Unit WD 17 30 – Reading the Inlet (Supply) Gas Pressure (INP) 29
14 – Separate T’stat, furnace, Cooling Unit & Trans W.D. 17 31 – Reading the Outlet (Manifold) Gas Pressure 29
15 – Same T’stat, Separate Furnace, Cooling Unit & Trans W.D. 17 32 – Integrated Control Board 30
16 – Same T’stat Separate Furnace, Heat Pump and Transformers 18 33 – Wiring Diagram A/C Ready Furnace 33
17 – Same T’stats Separate Furnace, Cooling Unit and Transformers 18 34 - Wiring Diagram Heating Only 34
LIST OF TABLES
1 – Furnace Clearances to Combustibles 6 10 – Recommended Thermostat Wire Colors & Connections 19
2 – Model Nomenclature 7 11 – Estimated Free Area 22
3 – High Altitude Gas Orifice Chart 13 12 – Vent Clearances 24
4 – Gas Pipe Capabilities 14 13 – Roof Jack Specifications 26
5 – Ratings and Physical Electrical Data 14 14 – Input Calculations for a cu-ft Gas Meter 28
6 – Heating Only Models 1/3 HP Blower and Motor Rating 15 15 – Input calculations for a Mj/m³ Gas Meter 28
7 – A/C Ready Models 1/3 HP Blower & Motor Rating 15 16 – Inlet (Supply) Gas Pressure Range 29
8 – A/C Ready Models 3/4 HP Blower & Motor Rating 15 17 – Blower Performance 32
9 – Low Voltage, Wire Gage and Max Lengths 16
SECTION I: SAFETY
This is a safety alert symbol. When you see this symbol on
labels or in manuals be alert to the potential for personal injury.
Understand and pay particular attention to the signal words
DANGER, WARNING, or CAUTION.
DANGER: indicates an imminently hazardous situation, which if
not avoided, will result in death or serious injury.
WARNING: indicates a potentially hazardous situation, which if
not avoided, could result in death or serious injury.
CAUTION: indicates a potentially hazardous situation, which if
not avoided, may result in minor or moderate injury. It is also
used to alert against unsafe practices and hazards involving
property damage.
SAVETHISMANUALFORFUTUREREFERENCE

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SPECIFIC SAFETY RULES AND PRECAUTIONS
1. Only Natural gas or Propane (LP) gases are approved for
use with this furnace. Refer to the furnace rating plate or
SECTION IV of these instructions.
2. Install this furnace only in a location and position as
specified in SECTION II of these instructions.
3. A gas fired furnace for installation in a residential garage
must be installed as specified in SECTION I of these
instructions.
4. Provide adequate combustion and ventilation air to the
furnace space as specified in SECTION VI of these instructions.
5. Combustion products must be discharged outdoors.
Connect this furnace to an approved vent system only, as
specified in SECTION VI of these instructions.
6. Tests for gas leaks as specified in section IX of these
instructions. Never test for gas leaks with an open flame.
7. Always install furnace to operate within the furnaces
intended rise range with a duct system that has an external static
pressure within the allowable range, as specified in these
instructions. See furnace rating plate.
8. When a furnace is installed so that the supply duct(s) carry
the air circulated by the furnace to areas outside the space
containing the furnace, the return air shall also be handled by
duct(s) sealed to the furnace casing and terminating outside the
space containing the furnace.
9. The return air duct system is not required by the
manufacturer provided the combustion air and vent system have
been installed as a Two Pipe Sealed Combustion System and
provided a return air duct system is not required by state, local
or regional codes. Refer to sealed combustion systems section in
ANSI 223.1 (NFPA 54) – latest edition.
10. It is permitted to use the furnace for heating of buildings or
structures under construction. Installation must comply with all
of the manufacturer’s instructions including:
Proper vent installation.
Furnace must be operating under thermostatic control.
Return air duct must be sealed to the furnace.
Air filters must be in place.
Set furnace input rate and temperature rise per the
rating plate marking.
Means for providing outdoor air required for
combustion.
Return air maintained between 55°F (13°C) and 80°F
(27°C).
The air filter must be replaced upon substantial
completion of the construction process.
Clean furnace supply and return air duct work making
sure the duct system is free of saw dust, dirt, dust and
debris. Clean all of the furnace components upon
substantial completion of the of the construction
process.
Verify furnace operating conditions including:
Ignition
Input rate
Temperature rise
Venting system
Verify the furnace is operating according to the
manufacturer’s instructions.
11. When installed in a Manufactured (Mobile) Home: The
combustion air shall not be supplied from occupied spaces.
12. The size of the furnace shall be based on an acceptable heat
loss calculation for the structure. ACCA Manual “J” or other
approved methods may be used.
13. Gas fired heating equipment must be vented - do not
operate unvented
14. If you are replacing an existing furnace, it may be necessary
to replace the roof jack venting system. Improperly sized or the
wrong roof jack venting system can result in vent gas leakage or
the formation of condensate. Refer to the National Fuel Gas
Code ANSI Z223.1 or CAN/CGA B149.1 or .2 latest editions.
Failure to follow these instructions can result in injury or death.
15. To reduce the opportunity for condensation, the minimum
sea level input to the appliance, as indicated on the rating plate,
must not be less than 8% below the rated input.
16. Ensure that the supply voltage to the appliance, as indicated
on the rating plate, is not 5% greater than the rated voltage.
17. Manufactured (Mobile) Home Installation: This
appliance must be installed and maintained as a Two Pipe
Sealed Combustion Configuration. The combustion air pipe
must terminate in the same atmospheric zone as the vent pipe
and they must terminate external to the building.
18. Roof Jack Sizes:
Mortex is a 4” Vent Pipe with a 7” Combustion Air Pipe.
Coleman is a 5” Vent Pipe with a 8” Combustion Air Pipe.
Nordyne is a 5” Vent Pipe with a 8” Combustion Air Pipe.
If you replace a Coleman or Nordyne furnace with a Mortex and
do not change the vent the furnace will fire up for around 5
seconds to a minute and the flame will extinguish,
19. Modular Homes: This appliance can be installed in one of
the following configurations:
a. A Two Pipe Sealed Combustion Configuration. This
configuration has a combustion air pipe and a vent pipe that
terminates in the same atmospheric zone and is external to
the building. Refer to Figures 19 – 25.
b. A One Pipe Vent with Ambient Combustion Air
Configuration. This configuration has no combustion air
pipe connected to the burner box. The vent pipe terminates
external to the building.
c. A One Pipe Ventilated Combustion Air Configuration: This
configuration has the combustion air pipe connected to the
burner box and terminating in the attic or a crawl space.
The vent pipe terminates external to the building. The vent
FIRE OR EXPLOSION HAZARD
Failure to follow the safety warnings exactly could result in
serious injury, death or property damage. A fire or
explosion may result causing property damage, personal
injury or loss of life.
Never test for gas leaks with an open flame. Check all gas
piping connections with a commercially available soap
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pipe and the combustion air pipe do not terminate in the
same atmospheric zone. Refer to Figure
20. Modular Home Definition: Factory-built home
constructed to the state, local, or regional codes where the house
is located. The home is transported in one or more modules and
joined at the home site.
Manufactured (Mobile) Home Definition: Factory-built home
constructed, transported and installed under the federal building
code, administered by the U.S. Department of Housing and
Urban Development (HUD Code), rather than building codes
21. At their destination. The home is built, transported and
installed on a non-removable chassis.
GENERAL SAFETY REQUIREMENTS
This furnace should be installed in accordance with all
national and local building/safety codes and requirements, local
plumbing or waste water codes, and other applicable codes. In
the absence of local codes, install in accordance with the
National Fuel Gas Code ANSI Z223.1/NFPA 54, National Fuel
Gas Code, and/or CAN/CGA B149.1 Natural Gas and Propane
Installation Code (latest editions). Furnaces have been certified
to the latest edition of standard UL 307B
All installation and service of these furnaces must be
performed by a qualified installation and service agency
only as described by ANSI Z223.1, latest edition or in
Canada by a licensed gas fitter.
Refer to the furnace rating plate for the furnace model
number, and then refer to the dimensions, page 6 of these
instructions. Optional duct connector dimensions are shown
in Figures 2 thru 8. The optional duct connectors must be
installed according to the instructions.
Provide clearances to combustible materials as listed under
Clearances to Combustibles.
Provide clearances for servicing ensuring that service
access is allowed for both the burners and blower.
These models are ETL listed or approved for installation
into Manufactured (Mobile) Home, Modular Homes or in
Residential downflow applications.
Failure to carefully read and follow all instructions in this
manual can result in furnace malfunction, death, personal
injury and/or death.
Furnace for installation on combustible flooring shall not be
installed directly on carpeting, tile, or other combustible
materials other than wood flooring.
Check the rating plate and the power supply to be sure that
the electrical characteristics match. All models use nominal
115 VAC, 1 Phase, and 60 Hertz power supply. Do not
connect this appliance to a 50 Hertz power supply or a
power supply where the voltage exceeds 132 VAC.
This furnace must be installed so the components are
protected from water.
Installing and servicing heating equipment can be
hazardous due to the electrical and gas fired components.
Only trained and qualified personnel should install, repair,
or service gas heating equipment. Untrained service
personal can perform basic maintenance functions such as
cleaning exterior surfaces or replacing the air filters. When
working on heating equipment, observe precautions in the
manuals and on the labels attached to the unit and other
safety precautions that may apply.
These instructions cover minimum requirements and
conform to existing national standards and safety codes. In
some instances these instructions may exceed certain local
codes and ordinances, especially those who have not kept
up with changing residential construction practices. These
instructions are required as a minimum for a safe
installation.
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SAFETY REQUIREMENTS – INSTALLATION CODES
A manufactured (Mobile) Home installation must conform
with the Manufactured Home Construction and Safety
Standard, Title 24 CFR, Part 3280, or when this standard is
not applicable, the standard for Manufactured Home
Installations (Manufactured Home Sites, Communities, and
Setups) ANSI/NCS A225.1, and/or MH Series Mobile
Homes, CAN/CSA Z240
The appliance has been safety certified to UL307B.
Additional Installation Codes that may apply for your
installation are:
a. National Fuel Gas Code – ANSI Z223.1 / NFPA -54.
b. National Electrical Code ANSI / NFPA -70
c. Manufactured Housing – NFPA-501 and Fire Safety
Criteria for Mobile Home Installations – NFPA 501A
d. Recreational Vehicles – ANSI – 119 / NFPA-501C
e. In Canada, Installation Code for “Natural Gas Burning
Appliances and Equipment” CAN/CGA-B149.1 and
CAN/CGA-B149.2 Installation Code for “Propane
Burning Appliances and Equipment”.
f. Canadian Electrical Code, Part I (CSA C22.1)
g. All local, State, City, Township and Provincial Codes.
HEALTH HAZARD
Improper installation, adjustment, alteration, service or
maintenance can cause property damage, injury or death.
Incomplete combustion because of improper installation,
improper adjustment, alteration, service, or maintenance;
can result in exposure to substances which have been
determined by various state agencies to cause cancer, birth
defects or other reproductive harm.
Read the installation manual, users information and service
and maintenance manual thoroughly before installing or
servicing this equipment
Appliances must not be installed where they may be
exposed to potentially explosive or flammable atmosphere.
Installing this appliance in an explosive or flammable
atmosphere will result in a fire or explosion causing
personal injury, property damage and/or death.

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These models are ETL Listed and approved for installation
into a Modular Home, Manufactured (Mobile) Home,
Trailers and Recreational Vehicles.
NOTE: All applicable codes take precedence over any
recommendation made in these instructions.
Refer to the unit rating plate for the model number.
Refer to the dimensions page for the supply air and duct
connector connections and dimensions.
Provide clearances from combustible materials as listed in
Clearances to Combustibles Table.
Failure to carefully follow the all instructions in this manual
can result in furnace malfunction, death, personal injury
and/or property damage.
Furnaces for installation on combustible flooring shall not
be directly installed on carpeting, tile, or other combustible
material other than wood flooring.
Check rating plate and power supply to be sure the
electrical characteristics match. All models require 115
VAC\, single (1) phase, 60 hertz power supply. Do not
connect this appliance to a 50 hertz voltage supply or a
voltage supply that has a voltage greater than 130 VAC.
The furnace shall be installed so the electrical components
are protected from water.
Installing and servicing heating equipment can be
hazardous due to the electrical components and the gas
fired components. Only trained and qualified personnel can
install, repair, maintain, and /or service gas heating
equipment. Untrained service personnel can perform basic
maintenance functions such as cleaning the exterior panels
or replacing the air filters. When working on heating
equipment, observe the precautions in the manuals and on
the labels attached to the appliance. Observe any safety
precautions that may apply.
These instructions cover the minimum installation
requirements and conform to existing national standards
and safety codes. In some instances these instructions may
exceed certain local codes and ordinances, especially those
who have not kept up with changing Modular Home and
Manufactured (Mobile) Home construction practices. These
instructions are required as a minimum for a safe
installation.
This furnace is certified with the controls furnished. For
replacement parts, please order according to the
replacement parts list located in the back of the Service and
Maintenance Manual. Refer to the rating plate to obtain the
model and serial numbers so the correct parts can be
ordered.
The furnace supply air blower is designed for correct
performance with this furnace. Do not attempt alter or use a
different type the fan or fan motor with this appliance.
SAFETY PRECAUTIONS
1. Disconnect power supply before making wiring connections
to prevent electrical shock and equipment damage.
2. All appliances must be wired strictly in accordance with
wiring diagram furnished with the appliance. Any wiring
different from the wiring diagram could result in a hazard to
persons and property.
3. Any original factory wiring that requires replacement must
be replaced with wiring material having a temperature
rating of at least 105°C.
4. When servicing or repairing this equipment, use only
factory-approved service replacement parts. A complete
replacements parts list may be obtained by contacting the
factory. Refer to the rating plate on the appliance for
complete appliance model number, serial number, and
company address. Any substitution of parts or controls not
approved by the factory will be at the owner’s risk.
COMBUSTION AIR QUALITY
(LIST OF CONTAMINANTS)
Excessive exposure to contaminated combustion air will result
in safety and performance related problems.
The furnace will require outdoor air for combustion when the
furnace is located in any of the following environments:
Restricted Environments.
Buildings with indoor pools.
Furnaces installed in laundry rooms.
Furnaces installed in hobby or craft rooms.
Furnace installed in chemical storage areas.
Chemical Exposure.
The furnace will require outdoor air for combustion when the
furnace is located in an area where the furnace is being
exposed to the following substances and/or chemicals.
Permanent wave solutions.
Chlorinated waxes or cleaners.
Chlorine based swimming pool chemicals.
Water softening chemicals.
De-icing salts or chemicals.
Carbon tetrachloride.
Halogen type refrigerants.
Cleaning solvents – such as perchloroethylene.
Printing inks, paint removers, varnishes, ECT.
Hydrochloric acid.
Cements and glues.
Antistatic fabric softeners.
Masonry acid washing materials.
When outdoor air is used for combustion, the combustion air
intake pipe termination must be located external to the building
and in an area where there is no exposure to the substances
listed above.
FIRE OR ELECTRICAL HAZARD
Failure to follow the safety warnings exactly could result in
serious injury, death, or property damage.
A fire or electrical hazard may result causing property
damage, personal injury or loss of life.

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Furnace Weights
Heat Only Models –152 lbs (68.95 kg)
A/C Ready Models -175 lbs (79.38 kg)
SECTION II: GENERAL INFORMATION
INSPECTION
As soon as the furnace is received, it should be inspected for
possible damage during transit. If damage is evident, the extent
of the damage should be noted on the carrier’s freight bill. A
separate request for inspection by the carrier’s agent should be
made in writing. Also, before installation the furnace should be
This product must be installed in strict compliance with the
installation instructions and any applicable local, state, and
national codes including, but not limited to building,
electrical, and mechanical codes.
This furnace area must never be used as a broom closet or
for any other storage purposes, as a fire hazard may be
created. Never store items such as the following on, near or
in contact with the furnace.
1. Spray or aerosol cans, rags, brooms, dust mops,
vacuum cleaners, or other cleaning tools.
2. Soap powders, bleaches, waxes, or other cleaning
compounds.
3. Plastic items or containers
4. Gasoline, kerosene, cigarette lighter fluid, dry cleaning
fluids, or other volatile fluids.
5. Paper bags, boxes, or other paper products.
1. Turn off all gas lines before installing appliance.
2. When leak testing the gas piping system; the appliance
gas control valve must be isolated from pressures
exceeding 14 inwc (1/2 psia) (3.5 kPa).
3. Check the gas inlet pressure before the gas control valve
to insure the pressure is:
a. 7 inwc (1.744 kPa) for natural gas.
b. 11 inwc (2.74 kPa) for propane gas
4. Purging of air from gas supply line should be performed
as described in ANSI Z223.1 - latest edition “National
Fuel Gas Code”, or in Canada in CAN/CGA-B149.1 or
B149.2 codes.
5. Do not attempt to reuse any mechanical or electronic
ignition controllers which have been wet. Replace
defective controller.
6. Servicing or repairing of this equipment must be
performed by a qualified service agency.
7.
Do not install unit outdoors.
HAZARD OF ASPHYXIATION: Negative pressure
inside the closet with closet door closed and the
furnace blower operating cannot be more negative
t
han minus 0.05 inwc.
Any attempt to relocate or bypass a safety control or
replace safety controls with a control that is not
approved or incompatible may result in personal injury,
substantial property damage or death.
IMPORTANT
1. To prevent premature heat exchanger failure, do
not locate any gas-fired appliances in area where
corrosive vapors are present in the atmosphere.
Refer to Section I COMBUSTION AIR
DO NOT wet electronic components or wire
connections during the leak test. Wetting electronic
components may damage to the circuitry and corrode
the wire connections which can cause a hazardous
situation.
Dry any moisture from all leads and terminals if
wetting occurs. Wait at least 12 hours for the electronic
components and wire connections to fully dry before
energizing the system.
Because of the potential of odorant fade, a gas leak may not
be detected by smell. It is recommended that black iron pipe
be used from the gas valve to outside the home in order to
prevent gas leaks inside or under the home. Copper tubing
and brass fittings (except tin lined) shall not be used if the
gas contains more than a trace (0.3 grains per 100 cubic ft.)
of hydrogen sulfide gas. Check with your gas supplier about
gas content and for a gas leak detector.

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checked for screws or bolts which may have loosened in transit.
There are no shipping or spacer brackets which need to be
removed before startup.
FURNACE LOCATION AND CLEARANCES
The furnace shall be located using the following guidelines
1. Where a minimum amount of air intake/vent piping
(smallest roof jack) will be required.
2. As centralized with the air distribution as possible.
3. Where adequate combustion air will be available
(particularly when appliance is not using outdoor air for
combustion air).
4. Where it will not interfere with proper air circulation in the
confined space.
5. Where the outdoor combustion air/ vent terminal will not be
blocked or restricted. Refer to combustion air/ vent
instructions located in Section VI. These minimum
clearances must be maintained throughout the installation.
6. Where the appliance will be installed in a level position
with no more than ¼” (0.6 cm) slope side to side and front
to back to provide proper condensate drainage.
INSTALLATION IN FREEZING TEMPERATURES
1. Furnace shall be installed in an area where ventilation
facilities provide for safe limits of ambient temperature
under normal operating conditions. Ambient temperatures
must not fall below 32° F (0° C) unless the condensate
system is protected from freezing.
2. Do not allow the return air temperature to be below 55°F
(13°C) for extended periods. To do so may cause
condensate to occur in the main heat exchanger, leading to
premature heat exchanger failure.
CLEARANCES FOR ACCESS
Ample clearances should be provided to permit easy access to
the appliance. The following minimum clearances are
recommended.
1. Twenty-four (24) inches (61 cm) between the front of the
furnace and an adjacent wall or other appliance, when
access is required for servicing or cleaning.
2. Eighteen (18) inches (46 cm) at the side where access is
required for passage to the front when servicing or for
inspection or replacement of the flue/vent connections.
Table 1: Furnace Clearances to Combustibles
INSTALLATION IN A RESIDENTIAL GARAGE
A gas-fired furnace for installation in a residential garage must
be installed as specified in these instructions. For installation in
a residential garage, the furnace must be installed so the gas
burner(s) and the ignition source are located not less than 18
inches (46 cm) above the floor. The appliance must be located
or protected to avoid physical damage by vehicles.
TOP LEFT SIDE RIGHT SIDE BACK FRONT FRONT DUCT ROOF JACK
ALCOVE CLOSET
6 in 0 in 0 in 0 in 18 in 6 in 0 in 6 in
LOW AMBIENT TEMPERATURE HAZARD
Improper installation in an ambient temperature that is
consistently below 55°F (13°C) could result in a hazard
resulting in premature heat exchanger failure, a fire,
property damage, personal injury or loss of life.
DO NOT store any chemicals or volatile fluids around the
appliance. This is a very dangerous practice that must be
avoided.
Storing chemicals around the appliance can lead to heat
exchanger corrosion which will cause premature heat
exchanger failure, which may result in personal injury,
substantial property damage or death.
Storing volatile fluids around the appliance can lead to an
explosion which can cause substantial property damage
that may result in personal injury, or death.

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Table 2: Model Nomenclature
FURNACES INSTALLED IN THE COMMONWEALTH OF
MASSACHUSETTS ONLY
For all side wall horizontally vented gas fueled equipment installed
in every dwelling, building, or structure used in whole or in part for
residential purposes, including those owned or operated by the
commonwealth and where the side wall exhaust vent termination is
less than seven 7 feet (2.1336 m) above a finished grade in the area
of the venting. This is including but not limited to decks and
porches and the flowing requirements must be satisfied:
1. INSTALLATION OF CARBON MONOXIDE DETECTORS.
The installing plumber or pipe fitter shall observe that a hard
wired carbon monoxide detector with a battery backup shall be
installed on the same floor level where the gas fired appliance is
being installed with the horizontal vent system. In addition, the
installing plumber or pipe fitter shall observe that a battery
operated or hard wired carbon monoxide detector with an alarm
is installed on each additional level of the dwelling, building, or
structure served by the side wall horizontal vented gas fueled
equipment. It shall be the responsibility of the property owner to
secure the services of qualified licensed professionals for the
installation of hard wired carbon monoxide detectors.
a. In the event that the side wall horizontally vented gas fueled
equipment is installed in a crawl space or an attic, the hard
wired carbon monoxide detector with alarm and battery
backup may be installed on the next adjacent level.
b. In the event that the requirements of this subdivision cannot
be met at the time of completion of the installation, the
owner shall have thirty (30) days to comply with the above
48 requirements; provided; that during the said thirty (30)
day period, a battery operated carbon monoxide detector
with an alarm be installed.
2.APPROVED CARBON MONOXIDE DETECTORS
Each of the carbon monoxide detectors are required by in
accordance with the above provisions and shall comply with
NFPA 720, be ANSI/UL 2034 listed and are IAS certified.
3.SIGNAGE
A metal or plastic identification plate shall be permanently
mounted to the exterior of the building at a minimum height of
eight (8) feet (2.438 m) above the grade directly in line with the
gas fired appliance or equipment horizontal exhaust vent
terminal. The sign shall be in print of no less than one-half (1/2)
inch (12.7 mm) in size and shall read “GAS VENT BELOW.
KEEP CLEAR OF ALL OBSTRUCTIONS”.
4.INSPECTION
The state or local gas inspector of the side wall horizontally
vented gas fueled equipment shall not approve the installation
unless, upon inspection, the inspector observes carbon monoxide
detectors and signage installed in accordance with the provisions
of 248 CMR 5.08(2)(a)1 through 4.
Figure 1: Furnace Dimensions
Coil cabinet or insulated cabinet is not shown in Figure 1. Add 4
inches to the height for a heating only (AH3) models for the
insulated cabinet and 25.5 inches to the A/C Ready (CA3 and
CA4) models for the coil cabinet.
Total Height
Heating Only 51.852” + 4” = 55.852”
A/C Ready 51.852” + 25.5” = 77.352”
G - Gas
G18
18 - 80% Efficient
D
D - Downflow
060
060, 070, 077, 090
Heating Capacity
A
A = 56"
H
H- Heating Only
3B
A
A - Revision Letter
Type of Blower
B - Constant Torque Motor
Indoor Blower
Horse Power
3 = 1/3 HP 5 SPD
4 = 3/4 HP 5 SPD
Furnace Configuration
A - A/C Ready
C = 77.5"

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SECTION III: FURNACE DUCT CONNECTIONS AND
DUCT SYSTEM
General Information
1. The duct system’s design and installation must handle an air
volume appropriate for the space being heated and must allow
the furnace to operate within the rating plate specifications.
2. The duct system’s design and installation must be in
accordance with the NFPA standards pamphlets 90A and 90B
(latest editions) or applicable national, provincial, state, local
fire, and safety codes.
3. The duct system’s design and installation must create a closed
duct system. Manufactured (Mobile) Home or Modular Home
installations. The furnace must be installed so the supply ducts
carry air circulated by the furnace to areas outside the space
containing the furnace. The return air is handled with a
louvered filter door attached to the furnace casing. The return
air duct(s) are not required by the manufacturer providing the
combustion air and vent system have been installed and
maintained as a two (2) pipe sealed combustion configuration
and provided the return air duct system is not required by state,
local, provincial, or regional codes.
4. The duct systems design and installation must consist of a
properly sized duct system that provides a complete path for
heated or cooled air to circulate through the air conditioning
and heating equipment and to and from the conditioned space.
When the furnace is used in conjunction with a cooling coil, the coil
must be installed parallel with, or in the supply air side of the
furnace to avoid condensation in the primary heat exchanger. When
a parallel flow arrangement is used, dampers or other means used to
control air flow must be adequate to prevent chilled air from
entering the furnace. If manually operated, the damper must be
equipped with means to prevent the furnace or the air conditioner
from operating unless damper is full heating or full cooling position.
Figure 2: Duct Connector Dimensions
Floor Base Installation and Duct Connection
Downflow combustible floor base is used for installations on
combustible material or floors. The combustible floor base is
recommended by not required because the furnace base is insulated.
The combustible floor base is shown in Figure 3. Follow the
instructions supplied with the combustible floor base accessory to
be sure it is properly installed.
Figure 3: Duct Connector and Floor Base Installation
Downflow Duct Connectors
All downflow installations must use a suitable duct connector
approved by the furnace manufacturer for use with this furnace.
The duct connectors are designed as a transition between the
furnace base and the rectangular duct system under the floor. Refer
to the instructions supplied with the duct connector for proper
installation. The duct connector part number can be found in the
“Accessory Parts List” located in the Users Information Manual /
Service and Maintenance Manual.
When replacing an existing furnace the duct connector must be
checked to determine if the furnace will properly fit the duct
connector so all of the holes in the furnace base line up with the
holes in the duct connector. If the holes do not line up then, the duct
connector must be replaced.
The duct system is a very important part of the installation. If the
duct system is improperly sized the furnace will not operate
The cooling coil must be installed in the coil cabinet, or
in the supply air duct, downstream of the heat exchanger.
Cooled air may not be passed over the heat exchanger.
The duct system must be properly sized to obtain the
correct airflow for the furnace size that is being installed.
Refer to the furnace rating plate for the correct rise and
static pressures.
If the ducts are undersized, the result will be high duct
static pressure, and/or high temperature rises which can
result in a heat exchanger overheating condition. This
condition can result in premature heat exchanger failure,
which can result in personal injury, property damage, or
death.

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properly. To properly design the duct work for the building, refer to
the ASHRAE Fundamentals Handbook, Chapter on Duct Design or
a company that specializes in Manufactured (Mobile) Home,
Modular Home and HUD Home duct designs.
Figure 4: Air Distribution System – Single Trunk Duct
Figure 5: Air Distribution System – Double Trunk Duct
Figure 6: Air Distribution System – Graduated Trunk Duct
Important: If the supply air duct is being connected to the
appliance without the use of an accessory duct connector, then a
transition duct must be installed with flanges or tabs that are
securely attached and sealed to the supply air duct and the base of
the appliance. The transition duct must have insulation between the
duct and any combustible material. The transition duct must be the
same dimensional size as the supply air opening in the base of the
appliance.
Figure 7: Furnace Base Openings for Fuel, Electrical and A/C
Line Penetrations
Figure 8: Duct Connector Depth
Alcove Installation
This furnace is approved for use in an alcove with both the heating
only (without an air conditioning coil) and the A/C ready models. A
minimum of 24 inches (61 cm) front clearance to a face wall or
partition is needed for service access and return air clearances.
Prior to installing the furnace make sure the holes are cut into the
floor for the refrigerant tubing, the electrical wiring is in place, the
thermostat wiring and the condenser control wiring is in place.
Install the furnace as follows:
1. Before installing the furnace, be sure you have enough
clearance to install the furnace and clearance for the return air.
Refer to Table 1 CLEARANCES.
2. Remove the top shipping cover and corner posts.
3. Remove the upper access panel (door).
4. Remove the lower access panel (door).
5. Set the furnace in place on the duct connector. Make sure the
supply air opening lines up with the opening in the duct
connector.
6. Slide the furnace on to the floor base. Push the furnace back
until the furnace casing is against the rear flange.
7. Secure the furnace to the floor by drilling two holes through
the furnace base and the floor base at the right and left front
inside corners of the cabinet. Use two screws to secure the
furnace to the floor.
8. When any air leaks have been sealed reinstall the coil cabinet
panels.
9. Remove the roof jack assembly and replace with a new roof
jack. Be sure to follow the roof jack installation instructions
exactly.
10. Connect the gas lines, the line voltage and low voltage wiring.
11. Remove the coil cabinet panels and seal around the duct
connector and the furnace base to prevent air leakage.
12. Install the cooling coil into the coil compartment (for A/C
ready models only). Replace the panels when the coil
installation is complete.
13. Check for gas leaks. If no leaks are found then turn on the gas
to the appliance.
14. Follow the procedure to “START THE APPLIANCE” located
in the Users Information Manual.
15. Verify the furnace is operating properly and set the thermostat
to the desired temperature.
16. Place the upper access panel on the furnace.
Important: Fabricate and install an inspection door in the plenum
base below the appliance to allow an annual inspection of the heat
exchangers. The inspection door can be fabricated by the following
method.

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1. Cut a rectangular opening in the plenum base. A sheet metal
plate can be made that completely covers the opening in the
base.
2. The plate must be secured with screws and sealed to prevent
leaks.
3. The coil cabinet doors can be removed to inspect the heat
exchanger on most Manufactured (Mobile) Home Downflow
Appliances.
Closet Installation
This furnace is approved for use in an alcove with both the heating
only (without an air conditioning coil) and the A/C ready models. A
minimum of 6” front clearance to a face wall or partition is needed
for service access and return air clearances.
Air filter Size – All Models take two (2) - 16” x 20” x 1”.
Prior to installing the furnace make sure the holes are cut into the
floor for the refrigerant tubing, the electrical wiring is in place, the
thermostat wiring and the condenser control wiring is in place.
Follow the sixteen steps above for installing the furnace.
FILTERS
Alcove Installations
All applications require the use of an internal filter. All filters
mounting provisions are factory supplied as part of the louvered
return grille door.
Closet Installations
All furnaces are shipped with air filters located in the return air
louvered door. It is permissible to remove the filters from the return
air louvered door and use a return filter grille that has been installed
into the wall above the furnace and has a sufficient size so it does
not restrict the return airflow. The recommended filter sizes for the
return air filter grille are shown below for throwaway filters that are
rated for a velocity of 300 feet/minute (91.44 m/minute):
1,200 CFM requires a 20 inch x 30 inch filter size.
1,600 CFM requires a 20 inch x 40 inch filter size.
1,800 CFM requires a 25 inch x 30 inch filter size.
2,000 CFM requires a 25 inch x 40 inch filter size.
The recommended filter sizes for the return air filter grille are
shown below for pleated air filters that are rated for a velocity of
500 feet/minute (152.4 m/minute):
1,200 CFM requires a 20 inch x 20 inch filter size.
1,600 CFM requires a 20 inch x 25 inch filter size.
1,800 CFM requires a 20 inch x 30 inch filter size.
2,000 CFM requires a 16 inch x 40 inch filter size.
IMPORTANT: Throw away air filters with a rated velocity of 300
feet per minute (91.44 m/minute) cannot be used on the furnace
return air louvered door because the air velocity is too high and will
destroy the filter. The filter velocity with this furnace is 400 feet per
minute (121.92 m/ minute). Do not use a filter that is rated for less
than 400 ft/min (121.92 m/minute).
Never use a filter deeper that 1 inch (2.54 cm) or a filter that has a
large pressure drop. This pressure drop will cause the appliance
airflow to be reduced causing the appliance temperature rise to
increase causing reduced efficiency and higher heat exchanger
temperatures. If the appliance does not operate within the specified
rise range on the name plate or the limit is cycling, then you must
change the air filter to a bigger size or reduce the thickness in order
to reduce the pressure drop across the air filter.
DOWNFLOW COOLING COIL CABINET
The cooling coil cabinet is supplied with the A/C Ready models.
The cabinet is 25.5 inches (64.77 cm) tall. The base of the cooling
coil cabinet can be mounted directly to the duct connector and
attached with screws. Make sure all of the openings in the furnace
base matchup with the openings in the duct connector, especially
the supply air opening. You can remove the coil cabinet doors in
order to confirm that all the holes in the base line up with the holes
in the duct connector. A combustible floor base is not required
when using a cooling coil cabinet.
Line up the duct openings and secure the coil cabinet to the
floor before installing the cooling coil.
OUTDOOR AIR ACCESSORY
A replacement furnace may have a blend air accessory that supplies
fresh air from outside through a 4 inch (10.16 cm) pipe that attaches
to the top cover of the appliance. There is a knockout and four
screw holes are located in the top cover of the appliance for the
attachment of a blend air damper or tube assembly. Refer to Figure
10 for knockout and screw hole locations.
Figure 9: Outdoor Fresh Air Intake Knockout
SECTION IV: GAS SUPPLY AND VALVE
CONNECTIONS
All field installed gas piping must be pressure tested for
leaks prior to operation of the appliance. Never test for gas
leaks with an open flame. Use a commercially available
soap solution made specifically for detection of leaks. Be
sure to check all connections.
Failure to properly check all connections for leaks or failure
to check any connections for leaks may result in a fire or
explosion causing property damage, personal injury or loss
of life.

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Figure 10: WR 36J29 Gas Valve
GAS PIPING INSTALLATION
Properly sized black iron, approved flexible or steel pipe must be
used when making the gas connections to the furnace. Check the
local codes on the use of flexible pipe. Some local codes do not
allow the use of flexible pipe. Always use a listed connector. Do
not use a connector that has been serviced by another gas appliance.
Some utility companies may require pipe sizes larger than the
minimum sizes listed in these instructions and in the codes. Some
local codes may require pipe sizes that are larger than the minimum
sizes listed in these instructions.
The installation of a drip leg and a ground union is required.
IMPORTANT: Plan your gas supply piping route before
determining the gas entry. Use 90 degree service elbow(s), or short
nipples and conventional 90 degree elbow(s) to enter through the
cabinet access holes.
Figure 11: Supply Gas Piping
1A 1/8” NPT plugged tapping, accessible for test gauge
connection, must be installed immediately upstream of the gas
connection to the furnace.
2If local codes allow the use of a flexible gas appliance
connector, always use a new listed connector. So not use a
connector that has previously serviced another gas appliance.
3Piping to units should conform to local and national
requirements for type and volume of gas handled, and pressure drop
allowed in the line. Refer to Table 4 to determine the number of
feet of pipe and the BTU Input to determine the proper size pipe for
the unit to be installed. The length of pipe will determine the pipe
diameter. Refer to Table 4. When several units are served by the
same main, the total capacity, BTU/H and length of main must be
considered. Avoid pipe sizes smaller than 1/2" (1.27 cm).
Table 4 allows for a 0.3" W.C. (0.075 kPa) pressure drop in the




ON / OFF
Pressure
Convertable
OUT P
IN P
VENT
Manifold Pressure Tap
Electrical Terminals
Gas Supply Line
Pressure Tap
GAS FLOW
Switch
Regulator
INLET
OUTLET
Wrench Boss
FLOW
GAS LINE
GAS SUPPLY GAS SUPPLY
GAS LINE
GAS SUPPLY PIPING
ONPOSITION
OFF POSITION
LINE VALVE
UNION
LINE VALVE
UNION
DRIP LEG
DRIP LEG
An overpressure protection device such as a pressure
regulator must be installed in the gas piping system up
stream of the furnace and must act to limit the downstream
pressure to the gas valve so it does not exceed 0.5 PSI (14”
WC (3.48 kPa)). Pressures exceeding 0.5 PSI (14” WC (3.48
kPa)) at the gas valve will cause damage to the gas valve,
the furnace, or some of its components. This will result in a
fire or explosion that will cause property damage and loss of
life.
1.Purging of air from gas lines should be performed as
described in ANSI Z223.1 - latest edition “National Fuel
Gas Code”, or in Canada CAN/CGA-B149 codes.
2When leak testing the gas supply piping system, the
appliance and its combination gas control must be isolated
during any pressure testing in excess of 14" W.C. (0.5 psi
(3.48 kPa)).
2.The unit should be isolated from the gas supply piping
system by closing its field installed manual shut-off valve.
This manual shut-off valve should be located within 6 ft
(1.83 m) of the heater.
3.Turn off all gas before installing appliance.
IMPORTANT
To prevent premature heat exchanger failure, the input to the
appliance, as indicated on the serial plate, must not exceed
the rated input by more than 5%.
Never apply a pipe wrench to the body of the gas valve
when installing or removing the gas pipe. The pipe wrench
must be placed on the gas valve “Wrench Boss”. Refer to
Figure 11.
Placing a wrench on the body of the gas valve will cause
damage to the valve causing improper operation and/or
leaking. This can result in a fire or explosion that can result
in personnel injury, property damage and loss of life.

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supply pressure from the building main to the unit. The inlet
pressure to the unit must be 6-7" W.C. (1.495-1.744 kPa) for
natural gas and 11-14" W.C. (2.74-3.48 kPa) for propane gas. When
sizing the inlet gas pipe diameter make sure that the unit supply
pressure can be met after the 0.3" W.C. (0.075 kPa) has been
subtracted.
If the 0.3" W.C. (0.075 kPa) pressure drop is too high, refer to the
National Fuel Gas Code NFPA-54 for other gas pipe capacities.
3 Install a ground joint union with brass seat and a manual shut-
off valve adjacent to the unit for emergency shut-off and easy
servicing of controls. A 1/8" (0.3175 cm) NPT plugged tap
accessible for test gauge connection is located on the gas valve.
4 Provide a sediment trap (Drip Leg) before each unit in the line
at the low spot to trap any debris in the line before it reaches the gas
valve. Refer to Figure 12.
5When performing leak testing, if the test pressure is above 14"
W.C. (0.50 psi (3.48 kPa)), you must close the field installed
shut-off valve to disconnect the appliance and its combination
gas control from the gas supply line. Plug the supply line before
testing. When testing pressures 14" W.C. (0.50 psi (3.48 kPa))
or below, close the manual shut-off valve on the appliance
before testing.
PROPANE CONVERSION PROCEDURE
Converting the Unit from Natural Gas to Propane Gas
1. If the appliance has been operating\, follow the procedure to
properly turn off the furnace located in the Users Information
Manual.
2. Turn off the gas supply at the valve in the line upstream of the
furnace or at the gas meter.
3. Disconnect the ground union in the gas supply line.
4. Disconnect the gas piping from the gas valve.
5. Disconnect the brown wires from the gas valve electrical
terminals.
6. Remove the two (2) screws that secure the gas valve manifold
assembly to the burner mounting plate.
7. Remove the brass gas orifice from the gas valve manifold.
8. Brass Orifice location is the opposite end of the manifold from
the gas valve.
9. Remove the propane orifice from the bag that is hung on the
gas valve.
10. Install the propane orifice into the gas manifold pipe. Place the
natural gas orifice into the bag and hang it on the gas valve.
11. Place the gas valve mounting bracket on the burner mounting
plate and secure with the screws you removed in step 5.
12. Reconnect the electrical wires to the terminals on top of the gas
valve.
13. Reconnect the gas supply piping to the gas valve. Remember to
place the wrench only on the gas valve wrench boss, and then
tighten the gas supply piping.
14. Reconnect the ground unions and tighten.
15. Remove the NATURAL GAS Tag located on the burner
mounting plate and replace it with the PROPANE GAS tag that
was in the bag. Place the NATURAL GAS tag in the bag that
is hanging on the gas valve.
16. Turn the gas supply valve back to the “ON” position and check
all of the connections for leaks.
17. Follow the procedure properly to start the appliance located in
the Users Information Manual.
HIGH ALTITUDE GAS ORIFICE CONVERSION
This furnace is constructed at the factory for Natural Gas-Fired
operation at 0 – 2000 ft (0 – 609.6 m) above sea level.
The gas orifice must be changed in order to operate properly when
installed in a location where the altitude is greater than 2,000 ft
(609.6 m) Refer to Table 3 in order to determine the proper gas
orifice size for the altitude where the furnace will be operating.
HIGH ALTITUDE PRESSURE SWITCH
CONVERSION
Changing the pressure switch when the appliance is installed in a
location below 6,500 ft (1,981 m) is generally not required unless the
pressure switch will not stay closed. Above 6,500 ft (1,981 m)
change only if switch will not stay closed.
The recommended pressure switch setting when the appliance is
located in an altitude above 6,500 ft (1,981 m) is 0.10 in-wc. (0.0249
kPa)
The recommended pressure switch setting when the appliance is
located in an altitude above 8,500 ft (2,591 m) is 0.10 in-wc (0.0249
kPa).
Refer to the accessories parts list in the Users Information Manual
for the correct pressure switch part number.
The gas supply must be turned off at the manual shutoff
valve (gas cock) and the electrical power disconnected
before proceeding with the conversion.
Never use an open flame to check for leaks. Fire or
explosion could occur. Since some leak solutions including
soap and water may cause corrosion or stress cracking, the
piping must be rinsed with water after testing unless it has
been determined that the leak solution is non-corrosive.

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Table 3: High Altitude Gas Orifice Size Chart
ELEVATION PART NO. ORIFICE DIA. DRILL SIZE PART NO. ORIFICE DIA. DRILL SIZE PART NO. ORIFICE DIA. DRILL SIZE PART NO. ORIFICE DIA. DRILL SIZE
SEA LEVEL 72AG-144 0.144 27 72AG-157 0.157 22 72AG-166 0.166 19 72AG-173 0.173 17
2,000 72AG-140 0.140 28 72AG-154 0.154 23 72AG-161 0.161 20 72AG-169 0.169 18
3,000 72AG-140 0.140 28 72AG-152 0.152 24 72AG-161 0.161 20 72AG-166 0.166 19
4,000 72AG-136 0.136 29 72AG-149 0.149 25 72AG-159 0.159 21 72AG-166 0.166 19
5,000 72AG-136 0.136 29 72AG-147 0.147 26 72AG-157 0.157 22 72AG-161 0.161 20
6,000 72AG-136 0.136 29 72AG-144 0.144 27 72AG-154 0.154 23 72AG-159 0.159 21
7,000 72AG-128 0.128 30 72AG-144 0.144 27 72AG-149 0.149 25 72AG-157 0.157 22
8,000 72AG-128 0.128 30 72AG-140 0.140 28 72AG-147 0.147 26 72AG-154 0.154 23
9,000 72AG-128 0.128 30 72AG-136 0.136 29 72AG-144 0.144 27 72AG-152 0.152 24
10,000 72AG-120 0.120 31 72AG-136 0.136 29 72AG-140 0.140 28 72AG-147 0.147 26
ELEVATION PART NO. ORIFICE DIA. DRILL SIZE PART NO. ORIFICE DIA. DRILL SIZE PART NO. ORIFICE DIA. DRILL SIZE PART NO. ORIFICE DIA. DRILL SIZE
SEA LEVEL 72AG-086 0.086 44 72AG-093 0.093 42 72AG-096 0.096 41 72AG-104 0.104 37
2,000 72AG-082 0.082 45 72AG-093 0.093 42 72AG-093 0.093 42 72AG-101 0.010 38
3,000 72AG-082 0.082 45 72AG-089 0.089 43 72AG-093 0.093 42 72AG-099 0.099 39
4,000 72AG-082 0.082 45 72AG-089 0.089 43 72AG-093 0.093 42 72AG-099 0.099 39
5,000 72AG-081 0.081 46 72AG-089 0.089 43 72AG-089 0.089 43 72AG-098 0.098 40
6,000 72AG-078 0.078 47 72AG-086 0.086 44 72AG-089 0.089 43 72AG-096 0.096 41
7,000 72AG-078 0.078 47 72AG-086 0.086 44 72AG-086 0.086 44 72AG-093 0.093 42
8,000 72AG-076 0.076 48 72AG-082 0.082 45 72AG-086 0.086 44 72AG-093 0.093 42
9,000 72AG-076 0.076 48 72AG-081 0.081 46 72AG-082 0.082 45 72AG-089 0.089 43
10,000 72AG-073 0.073 49 72AG-078 0.078 47 72AG-081 0.082 46 72AG-089 0.089 43
60,00 BTU FURNACE 70,00 BTU FURNACE 77,00 BTU FURNACE 90,00 BTU FURNACE
NATURAL GAS
PROPANE GAS
60,00 BTU FURNACE 70,00 BTU FURNACE 77,00 BTU FURNACE 90,00 BTU FURNACE
PROPANE AND HIGH ALTITUDE KITS
It is very important to choose the correct kit and/or gas orifices for the altitude where the appliance will be operating. It is also
very important to choose the correct kit and/or gas orifices for the type of gas the appliance will be burning. Only use Natural
Gas Orifices in appliances operating on Natural Gas. Only use Propane Gas for appliances that have been converted to use HD-5
Propane (LP) Gas. Do not use this furnace with butane or butane air gases.
Incorrect gas orifices or a furnace that has been improperly converted will create an extremely dangerous condition resulting in
premature heat exchanger failure, excessive sooting, DANGEROUSLY HIGH LEVELS OF CARBON MONOXIDE
resulting in personal injury, property damage, a fire hazard and/or loss of life.
High altitude and HD-5 propane (LP) conversions are required for the appliance to maintain proper operation. An authorized
dealer or qualified service contractor must make all gas conversions. In Canada, a certified conversion station or qualified
service agency, using factory specified and/or approved parts must perform the conversion. The installer must take every
precaution to insure the appliance has been properly converted by using the correct gas orifices and placing the gas valve
regulator in the proper position for the gas being used.
DO NOT attempt to drill out any orifices to obtain the proper size. The orifice MUST be drilled with precision equipment
ONLY. Hand drilling orifices WILL CAUSE misalignment of the burner flame causing the flame to impinge on the heat
exchanger resulting in premature heat exchanger failure, dangerously high levels of carbon monoxide, personal injury,
property damage and/or death.

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Table 4: Gas Pipe Capabilities
Note: capabilities up to 14” W.C. (0.50 PSI (3.48 kPa)) Gas Pressure through Schedule 40 Pipe.
Cubic Feet per Hour with a pressure drop of 0.3” W C (0.0075 kPa).
Natural Gas – Specific Gravity – 0.60
Propane Gas – Specific Gravity – 1.50
SECTION V: LINE AND LOW VOLTAGE
WIRING
POWER SUPPLY
The furnace internal wiring is complete except for the power
supply and the thermostat wires. See wiring diagram and/or
Table 5, 6 and 7 for fuse and circuit current. The minimum
circuit breaker dice is 15 amps. A fused switch is recommended
to be mounted on the side of the unit fused for the proper
current. Multiply 1.25 to the current value shown in the tables
below for the proper breaker size. The minimum supply wire
size is 14 gauge and the minimum ground wire size is 14 gauge.
The use of cable connectors on incoming power supply wires to
relieve any strain on wiring is recommended.
The furnace must be electrically grounded in accordance with
local codes or, in absence of local codes, with the National
Electrical Code, ANSI/NFPA 70, and / or the Canadian
Electrical Code CSA22.1, Part 1, if an external electrical source
is utilized.
Proper methods for field installing electrical wiring:
i. Between the furnace and devices not attached to the
furnace.
ii. Between the separate devices that are field installed
and located.
iii. Exterior to the furnace between the burner assembly
and a limit control or a fan control.
Wiring shall conform to the temperature limitations of 63°F
(35°C) rise.
The furnace shall be installed so the electrical components shall
be protected from water.
Table 5 Ratings & Physical Electrical Data
to 20 1/2 5/8
Natural to 60 1/2 -
60 to 70 - 3/4
to 40 1/2 -
Propane to 70 - 5/8
to 80 1/2 -
to 20 - 5/8
to 50 1/2 -
Natural to 60 - 3/4
70 to 80 3/4 -
to 30 1/2 -
Propane to 60 - 5/8
to 80 1/2 -
MODEL
G18D TYPE OF GAS LENGTH (FT) PIPE SIZE (IN) PIPE SIZE IN OD
to 20 - 5/8
to 50 1/2 -
Natural to 60 - 3/4
77 to 80 3/4 -
to 30 1/2 -
Propane to 60 - 5/8
to 80 1/2 -
to 40 1/2 3/4
Natural to 50 - 3/4
90 to 30 1/2 -
Propane to 40 - 5/8
to 60 1/2 3/4
PIPE SIZE
(IN) PIPE SIZE IN OD
MODEL
G18D TYPE OF GAS LENGTH (FT)
Input Output Cabinet Width
Max. External
Static Pressure,
Duct inwc AFUE Air Temp. Rise Range
60,000 48,000 19.5" 0.30 80% 40-70
70,000 56,000 19.5" 0.30 80% 40-70
77,000 61,600 19.5" 0.30 80% 40-70
90,000 72,000 19.5" 0.30 80% 45-75
Input Max Outlet Air Temp Blower Size Max. Over- Circuit Protection
60,000 170 10 x 8 15
70,000 170 10 x 8 15
77,000 170 10 x 8 15
90,000 175 10 x 8 15
Min. Wire Size (AWG)
@ 75 FT One Way
14
14
14
14
USECOPPERCONDUCTORSONLY.

MORTEXPRODUCTSINC501TERMINALRDFORTWORTH,TX76106Page15
Table 6: Heating Only Models; Blower Motor Ratings
Table 7: A/C Ready Models; Blower Motor Ratings
Table 8: A/C Ready Models; Blower and Motor Ratings
Model G18D060AH3BA G18D070AH3BA G18D077AH3BA G18D090AH3BA
BlowerMotorHP 1/31/31/31/3
BlowerMortorSPD 5 5 5 5
BlowerMotorAmpsFLA 6.1 6.1 6.1 6.1
NominalAirFlow 1,100 1,100 1,100 1,100
24VACCurrent@60HZ 0.49 0.49 0.49 0.49
TotalUnitAmps 2.54 2.54 2.54 2.54
Model G18D060CA3BA G18D070CA3BA G18D077CA3BA G18D090CA3BA
BlowerMotorHP 1/3 1/3 1/3 1/3
BlowerMortorSPD5555
BlowerMotorAmpsFLA 6.9 6.9 6.9 6.9
NominalAirFlow 1,100 1,100 1,100 1,100
24VACCurrent@60HZ 0.49 0.49 0.49 0.49
TotalUnitAmps 2.54 2.54 2.54 2.54
Model G18D060CA4BA G18D070CA4BA G18D077CA4BA G18D090CA4BA
BlowerMotorHP 3/43/43/43/4
BlowerMortorSPD5555
BlowerMotorAmpsFLA 6.9 6.9 6.9 6.9
NominalAirFlow 1,700 1,700 1,700 1,700
24VACCurrent@60HZ 0.49 0.49 0.49 0.49
TotalUnitAmps 6.7 6.7 6.7 6.7

MORTEXPRODUCTSINC501TERMINALRDFORTWORTH,TX76106Page16
Figure 12: Furnace Component Locations
Line Wiring Connections
1. Remove the control box cover.
2. Install the cable connector on the 5/8” (15.875 mm) dia
hole on the left side of the control box.
3. Strip ½” (12.7 mm) of the insulation on the end of each
wire.
4. Insert the wires through the hole in the casing and through
the cable connector.
5. Use a wire nut to connect the black wire to the black pig tail
wire and tighten until the wires are securely fastened.
6. Use a wire nut to connect the white wire to the white pigtail
wire and tighten until the wires are securely fastened.
7. Use a green ground wire with a ring terminal. Insert a
green screw through the ring terminal and into the screw
hole and tighten the screw. Make the ground wire is
securely fastened to the control box. Connect the new
green wire with the bare supply wire and secure with a
wire nut, Ground screw hole location is in the small box
with the supply voltage wires.
8. Reinstall the control box cover.
IMPORTANT - All field installed wiring must be done in
accordance with the National Electrical Code ANSI/NFPA 70 –
latest edition or Canadian Electrical Code CSA C22.1 Part 1 or
all local codes. Unit must be electrically grounded according to
these codes.
The supply power wires from the main circuit breaker
panel to the furnace must be protected with a circuit
breaker.
Thermostat Wiring
Thermostat wires are routed through side of furnace and connect
to the pig tail wires located above the control box. The
thermostat wires should also be no smaller than 22 gauges Refer
to Table 9 for recommended wire gauge and lengths.
Table 9: Low Voltage Wire Gauge and Max Lengths
Maximum
Wire Length Thermostat Wire Gauge Thermostat Wire Maximum Current
0 - 112 Feet 18 3.0 Amps
0 - 70 Feet 20 3.0 Amps
0 - 30 Feet 22 3.0 Amps
For personal safety be sure to turn the electrical power
“OFF” at the main entrance (Circuit Breaker Box) and at
the appliance before attempting any service or maintenance
operations. Home owners and / or furnace users should
never attempt to perform any maintenance which requires
opening the furnace control box door. Refer to Figure 13 for
the location of the ON/OFF switch.
Disconnect power supply before making wiring
connections to prevent electrical shock and equipment
damage.
If sheathed cable is used, refer to NEC National
Electrical Code (NFPA 70) or the Canadian Electrical
Code, Part 1 (CSA C22.1) and local codes for additional
requirements concerning supply circuit wiring.
This appliance must be field wired strictly in accordance
with the wiring diagram furnished with this appliance.
Any altered wiring or wiring not specified on the wiring
diagram could result in a hazard to persons and /or
property causing personnel injury, property damage or
death.
Any original factory wiring that requires replacement
must be replaced with wiring material having a
temperature rating of at least 35°C.
Ensure the supply voltage to the appliance is not greater
than 5% above or below the rated voltage shown on the
appliance rating plate.

MORTEXPRODUCTSINC501TERMINALRDFORTWORTH,TX76106Page17
The low voltage factory wires are 18 gauge. The thermostat
wires connect to the pigtail wires of the same color.
The use of a five (5) conductor cable from the thermostat to the
furnace is recommended for typical heating installations.
The thermostat wire colors and the typical connections are listed
in Table 10.
The adjustable heat anticipator in the thermostat is pre-set at
0.40 Amps. This setting should be checked at the time of
installation
In most cases the thermostat may be a “self-setting" type in
which case no amp setting will be found on the thermostat,
eliminating the need for any field adjustment.
Thermostat should be located on an inside wall in an open area
to more closely regulate average room air, preferably, where
there is air movement back to furnace. Locating height of
thermostat is important. Thermostat should be located
preferably upstream from the furnace return airflow, not within
3 feet of from any windows, 52 to 66 inches above the floor,
where it will not be affected by heat from the unit or other
sources, or drafts from frequently opened doors.
DO NOT place the thermostat within 3 feet (91.44 cm) of any
the furnace supply air registers
DO NOT place the thermostat within 3 feet (91.44 cm) of any
the air conditioner supply air registers
Maintenance, operating and/or programming instructions are in
the envelope accompanying the thermostat. Give the envelope to
the home owner after the installation is complete.
NOTE: There is a 3 Amp slow blow bar fuse located on the left
side of the control board that protects the 24 VAC circuit.
Replace the fuse only with the equivalent 3 Amp Automotive
type fuse.
Separate Heating and Cooling Thermostats
If the heating/cooling system in your house is a central heating
and cooling system but the furnace and the cooling unit are
controlled by separate thermostats then the use of a thermostat
interlock switch is required in order to prevent the furnace and
the air conditioner from operating at the same time.
Figure 13: Separate Thermostats, Furnace and Cooling Unit
Figure 14: Separate Thermostat, Furnace, Cooling Unit and
Transformers
Figure 15: Same Thermostat, Separate Furnace, Cooling
Unit and Transformers
Common
Transformer
R
Transformer
24 VAC
Air Handler
Switch
Interlock
Thermostat
COOL
HEAT
COM
C
W
G
R
Y
C
Thermostat
Cooling
Thermostat
Heating
Y
G
R
W
G
Condenser
Outdoor Unit
R
Common
Transformer
Transformer
24 VAC
Air Handler
Switch
Interlock
Thermostat
COOL
HEAT
COM
C
W
G
R
Y
C
Thermostat
Cooling
Thermostat
Heating
Y
G
R
W
G
R
Transformer
Condenser
Outdoor Unit
R
HEAT
COOL
24 VAC
Transformer
Common
G
R
W
Y
Cooling
Thermostat C
Y
R
G
W
C
COM HEAT
COOL
Thermostat
Interlock
Switch
Furnace
24 VAC
Transformer
Transformer
Heating /
Common
Condenser
Outdoor Unit
R24 VAC
Transformer
Transformer
Common
C
Do not locate thermostat within three feet of any of the
following items:
1. Furnace supply air registers
2. Cooling unit supply air registers
3. Lights or heat lamps
4. Aquariums
5. Televisions, stereo, amplifiers, surround sound
systems
6. Stoves or any cooking appliance
7. Refrigerator
8. Washer and/or dryer
9. Hot water tank
10. Sink or near any hot water
11. Within 15 feet of any electric space heater
12. Within two feet of any sunlight

MORTEXPRODUCTSINC501TERMINALRDFORTWORTH,TX76106Page18
Figure 16: Same Thermostat; Separate Furnace and Heat
Pump Unit with separate transformers
Figure 17: Same Thermostat, separate Furnace and Cooling
Unit and transformers
Typical Heating/Cooling Thermostat Wiring Connections
1. Remove the control box cover.
2. Insert the wires from the thermostat through the grommet in
the left side of the casing next to the low voltage wire
pigtails above the control box.
3. Strip ½” of the insulation on the end of each wire.
4. Connect the Red (24 VAC) supply thermostat wire to the
Red low voltage pigtail wire and secure with a wire nut.
5. Connect the White (heating) thermostat wire to the White
low voltage pigtail wire and secure with a wire nut.
6. Connect the Green (indoor fan) thermostat wire to the
Green low voltage pigtail wire and secure with a wire nut.
7. Connect the Yellow (air conditioning) wire from the
thermostat with the Yellow low voltage pigtail wire on the
furnace and with the wire that goes to the “Y” terminal on
the condenser unit. Fasten the three wires together securely
with a wire nut.
8. Connect the Black (24 VAC Common) wire from the
thermostat with the Black low voltage pigtail wire on the
furnace and with the (Common) wire that is connected to
the “C” terminal on the outdoor unit. Fasten the three wires
together securely with a wire nut.
9. Reinstall the control box cover.
Figure 18: Typical Single Stage Heating/Cooling
Digital Thermostat with Two Stage Furnace
Figure 19: Typical Two Stage Heating/Cooling Digital
Thermostat Connections
Typical Heat Pump - Heating/Cooling Thermostat Wiring
Connections
1. Remove the control box cover.
2. Insert the wires from the thermostat through the grommet in
the left side of the casing next to the low voltage wire
pigtails above the control box.
3. Strip ½” of the insulation on the end of each wire.
4. Connect the Red (24 VAC) supply thermostat wire to the
Red low voltage pigtail wire and secure with a wire nut.
RC
RH
G
Thermostat
R
G
W
C
Air Handler
24 VAC
Transformer
Transformer
Common
Condenser
Outdoor Unit
W/E
C
W2
Y
O
Y
RC
RH
G
W/E
T
C
W2
Y
O
Add Jumper if Outdoor Stat is not used
24 VAC
Transformer
Transformer
Common
Optional Outdoor
Temperature Switch
RH
RC
G
Thermostat
R
G
W
C
Air Handler
24 VAC
Transformer
Transformer
Common
Condenser
Outdoor Unit
W
C
Y
R
C
Y
24 VAC
Transformer
Transformer
Common
G
R
Thermostat Air Handler
24 VAC
Transformer
Transformer
Common
Condenser
Outdoor Unit
W
Y
C
R
G
W
W2
C
Y
C
G
R
Thermostat Air Handler
24 VAC
Transformer
Transformer
Common
Condenser
Outdoor Unit
W
Y
C
R
G
W
W2
C
Y
C
W2
When the furnace and air conditioning units are separate but
they are using the same thermostat a thermostat interlock
system must be provided to prevent simultaneous operation
of the furnace and air conditioner. Simultaneous operation
can result in equipment overheating, equipment damage,
and energy wastes. Refer to Figures 14, 15 and 16.
Do Not connect the Yellow wire to the thermostat unless an
outdoor unit is installed.

MORTEXPRODUCTSINC501TERMINALRDFORTWORTH,TX76106Page19
NOTE: If the cooling unit is separate from the furnace and
each have a transformer then remove the Red jumper
wire on the RC” and “RH” terminals on the thermostat
and connect the wire that goes to the “R” terminal the
outdoor unit to the “RC” terminal on the thermostat
and connect the wire that goes to the “R” terminal on
the furnace to the “RH” terminal on the thermostat. If
you do not have the “RH” and “RC” terminals on the
thermostat you must buy a new thermostat or a
thermostat interlock switch.
1. Connect the White (heating) wire from the thermostat to the
White low voltage pigtail wire on the furnace and the White
wire from the “E” terminal on the outdoor unit. Fasten the
three wires together securely with a wire nut.
2. Connect the Green (indoor fan) wire from the thermostat to
the Green low voltage pigtail wire on the furnace and
securely fasten the two wires together with a wire nut.
3. Connect the Yellow wire from the thermostat to the yellow
wire on the furnace and the wire that is connected to the
“Y” terminal on the outdoor unit. Fasten the three wires
together securely with a wire nut.
4. Connect the Black (24 VAC Common) wire from the
thermostat with the Black low voltage pigtail wire on the
furnace and with the (Common) wire from the “C” terminal
on the outdoor unit. Fasten the three wires together securely
with a wire nut.
5. Connect the Orange (Reversing Valve Solenoid) wire from
the thermostat with the wire from the “O” terminal on the
outdoor unit. Fasten the two wires together securely with a
wire nut.
6. Connect the Brown (2nd Stage Heating) wire from the
thermostat with the wire from the “W2” terminal on the
outdoor unit. Fasten the two wires together securely with a
wire nut.
Table 10: Recommended Thermostat Wire Colors and Connections.
Note: 24 VAC Common wire must be used for digital thermostats.
SECTION VI: COMBUSTION AIR AND VENT
SYSTEM
ROOF JACK VENT SAFETY
Category I — a central furnace that operates with a non-
positive vent static pressure and with a flue loss not less than 17
percent. The combustion system is fan assisted.
This Category I direct vent furnace is designed for
Manufactured Home and Modular Home applications. It may be
installed without modification in a garage, equipment room,
alcove, or any other indoor location where all required clearance
to combustibles and other restrictions are met.
CATEGORY 1 - 450 F MAX VENT TEMP.
The direct venting system must be installed in accordance with
Section 5.3, Air for Combustion and Ventilation, of the National
Fuel Gas Code Z223.1/NFPA 54 (latest edition), or Sections 7.2,
7.3 or 7.4 of CSA B149.1, National Gas and Propane Codes
(latest edition) or applicable provisions of the local building
code and these instructions.
The furnace shall be connected to the manufacturer
recommended roof jack direct vent system, and shall never be
connected to a factory-built or masonry chimney.
The furnace shall not be connected to a chimney / vent
serving a separate appliance designed to burn solid fuel.
When replacing a competitor’s furnace with a Mortex
Furnace the installer MUST change the Roof Jack. The
Mortex Roof Jack pipes are smaller. This will cause leaking
between the vent and the combustion air if the installer tries
to use a Coleman or Nordyne Roof Jack on a Mortex
Furnace. The Roof Jack Sizes are shown below:
Coleman has an 8” Outer Pipe and a 5”Iinner Pipe.
Nordyne has an 8” Outer Pipe and a 5”Iinner Pipe
Heating/CoolingThermostatWireColorCode
WireColor Description
Letter
Code
FurnacePigTail
WireConnection
Thermostat
Connection
Condenser
Connections
RED 24VAC R Red R N/A
WHITE Heat(1stStageHeat) W White WorW1 N/A
GREEN IndoorFan G Green G N/A
YELLOW Cooling‐Stage1 Y Yellow YorY1 YorY1
BLACK 24VACCommon BLK Black C C
HeatPump‐Heating/CoolingThermostatWireColorCode
WireColor Description
Letter
Code
FurnacePigTail
WireConnection
Thermostat
Connection
Condenser
Connections
RED 24VAC R Red R N/A
WHITE Heat(1stStageHeat) W White E N/A
GREEN IndoorFan G Green G N/A
YELLOW Cooling‐Stage1 Y Yellow YorY1 YorY1
BLACK 24VACCommon BLK Black C C
BROWN Heat(Optional2ndStageHeat) BRN N/A W2 W2
ORANGE HeatPumpReversingValveSolenoid O N/A O O
BLUE Cooling‐(Optional2ndStageCooling) BLU N/A Y2 Y2

MORTEXPRODUCTSINC501TERMINALRDFORTWORTH,TX76106Page20
Mortex has a 7” Outer Pipe and a 4” Inner Pipe.
Using a Coleman or Nordyne Roof Jack on a Mortex
Furnace will cause vented combustion products to get drawn
into the combustion air causing the flame to extinguish
within 10 seconds because the flame is running out of
oxygen.
These instructions list the maximum vent gas temperature. This
temperature must be used to select the appropriate venting
clearances.
It is recommended that the appliance is installed in a location
where the space temperature is 32 °F (0°C) or higher. If the
appliance is installed in a location where the ambient
temperature is below 32 °F (0°C), the combustion by-products
could condense causing damage to the appliance heat
exchanger.
IMPORTANT: The “ROOF JACK VENT SYSTEM” must be
installed as specified in these instructions for Manufactured and
Modular Homes.
This appliance cannot be common vented with another gas
appliance.
Combustion air cannot be supplied from occupied spaces. The
Mortex roof jack vent system must be used with this furnace.
Approved Manufactured (Mobile) Homes and Modular Homes
must be vented with an approved roof jack that consists of a 4”
diameter vent pipe and a 7” diameter outer pipe only. Do not
use a roof jack provided by any other manufacturer.
VENTING
Category I roof jack direct venting consists of vertically venting
one appliance in roof jack vent using two single wall metal
pipes and a crown assembly.
The roof jack type vent system extends in a general vertical
direction and does not contain offsets. A vent system having any
offset is not permitted.
The vent system consists of a four inch (4”) inner pipe attached
to the flue collar (4” collar) on the top of the heat exchanger just
below the top of the furnace and an outer seven inch (7”) pipe.
The combustion air is drawn between the inner four inch (4”)
pipe and the outer seven inch (7”) pipe. The seven inch (7”) pipe
is attached to a flange in the top cover and must be secured to
the top cover with a minimum of two (2) mechanical fasteners,
such as screws or rivets.
Figure 20: Roof Jack Mounting Collars – Top of Furnace
VENTING INTO AN EXISTING ROOF JACK
The furnace shall not be connected to another manufacturers
factory built roof jack vent system. If the furnace is connected to
another manufacturer’s roof jack vent system the furnace will
not vent properly especially if the existing roof jack consists of
larger diameter pipes.
Installing the correct roof jack is required. The installer must
change the roof jack vent system when installing a new furnace
or replacing an existing furnace.
ROOF JACK EXTENSIONS AND CROWN ASSEMBLY
1. The roof jack extensions and the crown assembly must be
installed in accordance with nationally recognized building
codes or standards and /or these instructions.
2. The roof jack has optional indoor and outdoor extensions.
The outdoor extensions must be used to extend the crown
assembly above the snow line.
3. The indoor extensions, shown in Figure 21, are 7 inches in
dia (Left Pipe) and 4 inches in dia (Right Pipe). The 4 inch
dia pipe is placed inside the 7 inch dia pipe. The extensions
are used when the roof jack is too short to extend to the
furnace. The extensions are available in a 10 inch length
and a 31 inch length. Refer to accessories parts list in the
Service and Maintenance Manual.
Figure 21: Roof Jack Indoor Extension Pipes
4. The outdoor extension, shown in Figure 22 has a 4 inch dia
pipe is fastened to the inside the 7 inch dia pipe. The
extension is used when the roof jack crown assembly must
be extended because of snow line, the roof peak or other
obstructions. The extension is available in a 16 inch length.
Refer to accessories parts list in the Service and
Maintenance Manual.
Figure 22: Roof Jack Outdoor Extension Pipes
5. The roof jack crown assembly must extend at least three (3)
ft (0.91 cm) above the highest point where it passes through
a roof of a building and at least two (2) feet higher than any
Venting into another manufacturers roof jack vent system
that is equipped with larger diameter vent and combustion
air pipes will cause combustion products being vented to be
drawn into the combustion air. This will result in a reduced
amount of oxygen to the burner flame and will cause the
flame to extinguish within the first 5 to 15 seconds or less.