MORTEX G18D SERIES Guide

MORTEX PRODUCTS INC 501 TERMINAL RD FORT WORTH, TX 76106 Page 1
DOWNFLOW ONLY For Installation In:
SINGLE STAGE GAS FIRED FURNACE 1. Manufactured (Mobile) Homes
MODELS: G18D SERIES 2. Recreational Vehicles
3. Modular Homes & Buildings
For installation only in HUD manufactured homes per Construction Safety 24 CFR Part 3280
USERS INFORMATION MANUAL
3 – Startup and Shutdown Instructions.......................................................... 6
4 – Homeowner/User Maintenance ................................................................. 8
5 – Troubleshooting .............................................................................................18
6 – Blower Performance......................................................................................23
7 – Accessories and Replacement Parts ........................................................23
8 – Wiring Diagrams .............................................................................................27
13 – Flue Box Assembly.....................................................................................................14
14 – Combustion Air Assembly..........................................................................15
15 – Blower Assembly ...........................................................................................15
16 – Component Locations .................................................................................16
17 – White Rodgers Gas Valve.............................................................................20
18 – Measuring Inlet (Supply) Gas Pressure...................................................20
19 – Measuring Outlet (Manifold) Gas Pressure ..........................................20
20 – Integrated Furnace Control Board...........................................................22
21 – Replacement Parts Identication.............................................................24
22 – Wiring Diagram – Heating Only Models................................................27
23 – Wiring Diagram – A/C Ready Models......................................................28
6 – Blower Performance Chart....................................................................................23
7 – Accessories................................................................................................................23
8 – Replacement Parts List ..................................................................................... 25
9 – Hight Altitude Gas Orice Chart..................................................................... 26
1 – Safety.....................................................................................................................2
2 – Homeowner/User Information ....................................................................5
1 – Safety.................................................................................................................. 10
2 – Furnace Maintenance .................................................................................. 11
3 – Furnace Controls ............................................................................................ 15
4 – Sequence of Operation ............................................................................... 17
The following list includes important facts and information regarding this gas furnace.
1. Furnace is rated at 115 VAC at 60 Hz.
2. Furnace is available in “Heating Only”or “A/C Ready”congurations.
3. Furnace is designed for use with cooling only or heat pump systems when a cooling coil cabinet and indoor coil is used. A/C
ready models are furnished with a cooling coil cabinet. The appropriate indoor coil must be selected and ordered separately.
4. A hold-down strap is furnished with furnace.
5. This furnace is designed for downow applications only.
6. This furnace must not be operated with the control box cover or front access panels removed.
7. This furnace is certied by ETL for use in the United States only.
SAVE THIS MANUAL FOR FUTURE REFERENCE
1 – Component Locations.....................................................................................4
2 – Burner Flame ......................................................................................................4
3 – Furnace Examination Checkpoints.............................................................5
4 – White Rodgers Gas Valve Components .....................................................7
5 – Gas Supply Line Piping and Shuto Valve Location.............................7
6 – Louvered Return Air Door - Outside ..........................................................8
7 – Louvered Return Air Door Filter Rack ...................................................................8
8 – Burner Assembly.........................................................................................................11
9 – Heat Exchanger Assembly w/ Baes ..................................................... 12
10 – 4”Combustion Air Tube Flange ................................................................ 13
11 – Top Cover Screws and Combustion Air Pan Screws .......................... 13
12 – Flue Box Cover Screws.................................................................................. 13
1 – Inlet Gas Pressure Range ................................................................................... 20
2 – Nominal Manifold Pressure........................................................................... 20
3 – Input Calculations For Cubic Foot Gas Meter........................................... 21
4 – Input Calculations For Cubic Meter Gas Meter........................................ 21
5 – Dip Switch Settings - Circ Blr Mtr Speeds & Htg Blower O Delay ..... 22
Manufactured and Distributed by: Mortex Products Inc www.mortx.com
501 Terminal Rd
Fort Worth, TX 76106
LIST OF SECTIONS - USERS INFORMATION MANUAL
LIST OF SECTIONS -SERVICE AND MAINTENANCE MANUAL
LIST OF FIGURES
LIST OF TABLES
CONTACT INFORMATION

MORTEX PRODUCTS INC 501 TERMINAL RD FORT WORTH, TX 76106 Page 2
SECTION 1: SAFETY
This is a safety alert symbol. When this symbol is seen 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.
Homeowners and furnace users must read all instructions
in this manual before performing any maintenance on this
furnace. This manual must be saved for future reference.
Safety Requirements
1. The furnace area must be kept clear and free of combustible
materials, gasoline and other ammable vapors and liquids.
2. Insulating material may be combustible. The furnace must be
kept free and clear of insulating material. The furnace area must
be examined when the furnace is installed in an insulated space
to make sure that insulation is away from the furnace.
3. Follow the instruction exactly as shown on the operating
instructions label, or the startup and shutdown instructions
located on page 7 of this manual to properly start the furnace or
turn the furnace o.
4. Should the gas supply fail to shut o or if overheating should
occur, shut o the manual gas cock located on the gas pipe
before turning o the electrical power supply to the furnace.
5. Do not use this furnace if any part has been under water as
a ood damaged furnace is extremely dangerous to operate.
Attempts to use the furnace could result in a re or explosion.
A qualied service agency should be contacted to inspect
the furnace and replace all gas controls, control systems, and
electrical parts that have been wet. In some cases, the damage
may be so severe that the furnace may need to be replaced.
6. Flammable materials, solvents, or other volatile liquids should
be stored only in approved containers outside the home. These
materials vaporize easily and are extremely dangerous.
7. Do not store cleaning materials near the furnace. Materials such
as bleaches, detergents, powdered cleaners can cause corrosion
of the heat exchanger and premature failure.
8. Do not use the area around the furnace as a storage area for
items that could block the normal ow of air to the furnace.
This ow of air is required for ventilation of the various furnace
components.
CAUTION
CAUTION
This furnace requires periodic routine maintenance and
cleaning of the exterior surfaces by the homeowner or user
to remove dust and debris. Any additional service or repair
must be performed by qualied personnel. This furnace
must be serviced and maintained as specied in these
instructions and any applicable local, state, and national
codes including, but not limited to building, electrical, and
mechanical codes.
Any adjustment, service, or maintenance by the
homeowner or user may create a condition where the
operation of the product could cause property damage,
personal injury, and death.
Only qualied service personnel or installer may refer to
the service and maintenance section of this manual for
serving or repairing this furnace.
FIRE OR EXPOLSION HAZARD
This furnace is designed and approved for use with Natural
Gas or Propane (LP) only. Do not burn any liquid fuel or
solid fuel in this furnace.
Burning any unapproved fuel in this furnace will result in
damage to the furnace heat exchanger which could result
in a re, personal injury, property damage, and loss of life.
Burning any unapproved fuel in the furnace will result in
termination of the factory warranty.
FIRE AND ELECRTRICAL HAZARD
Failure to follow the safety warnings in this manual and in
the furnace labels could result in a re or electrical hazard
which may cause property damage, personal injury, or
death.
• Do not store or use gasoline or other ammable vapors
and liquids in the vicinity of this or any other appliance.
WHAT TO DO IF YOU SMELL GAS:
• Do not try to light any gas appliance.
• Do not touch any electrical switch.
• Do not use any phone in your building, including cell
phones.
• Leave building immediately.
• Call your gas supplier from a neighbor’s phone. Follow
the gas supplier’s instructions.
• If you cannot reach your gas supplier, call the re
department.
• Instruction and service must be performed by
aqualied installer, service agency or gas supplier.

MORTEX PRODUCTS INC 501 TERMINAL RD FORT WORTH, TX 76106 Page 3
FIRE OR ELECTRICAL HAZARD
Failure to follow the safety warnings could result in a re
or electrical hazard which may cause property damage,
personal injury, or death.
This furnace must not be installed where it may be
exposed to potentially explosive or ammable
atmosphere. Installing this furnace in an explosive or
ammable atmosphere may result in a re or explosion
causing property damage, personal injury, or death.
HAZARD OF ASPHYXIATION: Negative pressure inside
a closet with closet door closed and the furnace blower
operating must not be more than 0.05”W.C.
To prevent premature heat exchanger failure, do not locate
any gas-red appliances in area where corrosive vapors
are present in the atmosphere. Refer to the section on
COMBUSTION AIR QUALITY.
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 furnace gas valve to outside
the home in order to prevent gas leaks inside the home.
Copper and brass tubing and ttings (except tin lined)
must not be used if the gas contains more than a trace
(0.3 grains per 100 cubic ft.) of hydrogen sulde gas.
Check with the gas supplier about gas content and for
a gas leak detector.
This furnace must not be installed where it may be
exposed to potentially explosive or ammable atmosphere.
Installing this furnace in an explosive or ammable
atmosphere may result in a re or explosion causing
personnel injury, property damage, or death.
D
D
ANGER
ANGER
ELECTRICAL OR EXPLOSION HAZARD
Do not use this furnace if any part has been under water.
A ood damaged furnace is extremely dangerous.
Attempts to operate a ood damaged furnace may result in
a re.
A qualied contractor, installer, or service agency must be
contacted to inspect the furnace for any water damage and
replace components, controls, or electrical parts that have
been damaged or replace the furnace.
D
D
ANGER
ANGER
USE ONLY NATURAL GAS OR HD-5 PROPANE
FUEL IN THIS FURNACE.
DO NOT USE “COMMERCIAL GRADE PROPANE”
OR ANY PROPANE BLEND OTHER THAN HD-5.
IF A FUEL OTHER THAN NATURAL GAS OR HD-5
PROPANE IS USED IN THIS FURNACE, YOUR
WARRANTY WILL BE VOID.
COMBUSTION AIR QUALITY
(LIST OF CONTAMINANTS)
This furnace requires 100% outdoor air for combustion. This
furnace must not be installed in the following environments.
• Restricted environments
• Buildings with indoor pools
• Laundry rooms
• Hobby or craft rooms
• Chemical storage areas
• Chemical Exposure
The furnace must not be exposed to the following substances and
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
• Hydrochloric acid
• Cements and glues
• Antistatic fabric softeners
• Masonry acid washing materials
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. Any exposure to the substances
listed above will void the furnace warranty.

MORTEX PRODUCTS INC 501 TERMINAL RD FORT WORTH, TX 76106 Page 4
Do no wet electronic components or wire connections
during the gas leak test. Wetting electronic components
may damage circuitry and wire connections and can cause
a hazardous situation.
Dry moisture from all leads and terminals if wetting does
occur.
Wait at least 12 hours for the electronic components and
wire connections to fully dry before energizing the furnace.
This furnace area must never be used as a broom closet, for
any other storage purposes or allow the furnace to come in
contact with the following substances.
1. Spray or aerosol cans, rags, brooms, dust mops, vacuum
cleaners, or other cleaning tools.
2. Soap powders, bleaches, waxes, other cleaning
compounds, plastic items or containers
3. Gasoline, kerosene, cigarette lighter uid, dry cleaning
uids, or other volatile uids.
4. Paper bags, boxes, or other paper products.
FIRE OR ELECTRICAL HAZARD
Servicing the furnace can be hazardous due to exposure
to electrical components. Only trained and qualied
personnel are allowed to service or repair this furnace. The
homeowner or user must never attempt to service or repair
this furnace.
The homeowner or user may perform only basic
maintenance functions such as cleaning of exterior
surfaces and replacing the air lters.
Observe all precautions in the manuals and on the
attached labels when performing maintenance on this
furnace.
Figure 1: Component Locations
Figure 2: Burner Flame

MORTEX PRODUCTS INC 501 TERMINAL RD FORT WORTH, TX 76106 Page 5
EXAMINING THE FURNACE
It is the homeowner’s or user’s responsibility to ensure that an
annual inspection of this furnace is made by a qualied service
agency. The qualied service agency must examine the furnace as
outlined in steps below before each heating season.
1. Examine the heat exchanger, vent pipe, combustion air
passages, vent connectors and chimney to be sure they are
clear and free of obstructions.
2. Examine the vent pipe making sure it is rmly in place, that it
is attached to the top of the furnace and it is physically sound
without holes and all of the connections are secure.
3. Examine the return air louvered door to make sure it is
physically sound, fastened securely to the furnace casing.
4. Examine the furnace casing making sure the physical support is
sound without sagging, cracks, or gaps.
5. Examine the furnace base making sure it is physically sound
without cracks, gaps, or sagging and that it has a good seal to
the casing.
6. Examine the furnace casing for obvious signs of deterioration.
7. Examine the burner ame to make sure the burner is adjusted
properly. The ame should appear long and cylindrical with a
blue color. Some yellow streaks may appear, especially near the
tip of the ame. The ame on a furnace operating on propane
(LP) will appear less blue and has considerably more yellow
streaking.
Figure 3: Burner Flame
SECTION 2: HOMEOWNER/USER INFORMATION
How the Furnace Works
Heating Cycle
1. The thermostat calls for heat which energizes furnace control
board“W”terminal.
2. The combustion air blower is energized for a pre-purge period
to remove any remaining gases from the heat exchanger and
will send those gases out the exhaust vent.
3. After the pre-purge period, the combustion air proving
pressure switch electrical contacts close if there is no exhaust
vent restriction.
4. After the pressure switch contacts closes, the hot surface igniter
is energized and will glow.
5. After the igniter has time to become suciently hot, the gas
valve will open and allow gas to ow to the burner. The gas will
ignite as it passes by the igniter and a ame will be established.
The ame sensor will sense the presence of ame and send
a signal back to the control board that a ame is present. The
control board will keep the gas valve open as long as the ame
sensor detects the presents of a ame and there is a call for heat
by the thermostat unless one of the 2 limit switches senses an
over-temperature condition.
6. After ignition has been established long enough for the heat
exchanger to heat up, the circulating blower motor will be
energized which distributes warm air throughout the home.
7. When the temperature of the home has reached the
temperature setting on the thermostat, the 24 VAC signal will be
removed from the “W” terminal on the control board which
causes the gas valve to de-energize and the burner ame to
extinguish. The circulating blower motor will shut down after
the heat exchanger has suciently cooled down.
8. The furnace will then be in “stand-by” mode until there is
another call for heat.
The furnace is equipped with the components and controls
necessary for proper and safe operation and identied in Figure 1.

MORTEX PRODUCTS INC 501 TERMINAL RD FORT WORTH, TX 76106 Page 6
General Homeowner/User Information
1. Refer to the furnace rating plate for the furnace model number
and specications for safe operation.
2. Provide clearance for service access to the burner
compartment, control box, and the blower compartment.
3. Failure to carefully read and follow all of the instructions in
this manual can result in malfunction of the furnace, property
damage, personal injury, or death.
4. If the furnace is installed in a residential garage, it must be
installed so the burner is located not less than 18 inches above
the oor and the furnace must be located or protected to avoid
physical damage by vehicles.
The Service Technician
A qualied service technician is required to perform any service
or repairs on the furnace. If the furnace gives any indication
of improper operation, call the service technician. The service
technician is allowed to perform the normal routine care of your
furnace as well as service and repairs and can detect potential
problems and make corrections before trouble develops.
Preventative maintenance of this type will allow the furnace to
operate with minimal concerns to the homeowner or users and
will add years of reliable comfort.
Warranty and Responsibilities
It is the responsibility of the homeowner to make certain the
furnace has been properly installed and adjusted to operate
properly.
The manufacturer warrants the furnace to be free from defects
in material or workmanship for a stated time in the warranty
agreement. The manufacturer will not be responsible for any
repair costs to correct problems due to improper setup, improper
installation, improper furnace adjustments, adding parts that
are not listed by the manufacturer for use with the furnace, and
improper operating procedures by the homeowner or users.
Specic examples of service calls which will be excluded from
warranty reimbursement are:
1. Correcting faulty duct work due to too few ducts or ducts that
are too small to provide proper air ow through the furnace.
2. Correcting wiring problems in the electrical circuit to the
furnace.
3. Resetting circuit breakers or on/o switches used for servicing.
4. Furnace problems caused by installation and operation of any
air conditioning unit, heat pump, or other air quality devise
which is not approved for use with this furnace.
5. Adjusting or calibrating the thermostat.
6. Problems caused by construction debris which has fallen into
the furnace.
7. Replacement of fuses.
8. Problems caused by dirty air lters.
9. Problems caused by restrictions in the return or supply air ow
causing low air ow.
The home owner should establish a thorough understanding of
these responsibilities with the installer or service company to
prevent misunderstandings at a later time.
While Homeowner or User is Away From Home
The furnace is equipped with safety shuto devices which will
shut o the gas burner in case of a malfunction. For this reason, it
is never practical to assume the furnace will operate unattended
for a long period of time.
If the homeowner or user is planning to be away from home for
a long period of time, someone should be asked to check on the
home every day especially when the outside temperature may fall
below 35°F to ensure the furnace is operating properly to prevent
water pipes from freezing.
When to Call For Service Assistance
Very often time can be saved if the service agency is given
information about a furnace problem ahead of time. This will
enable the service agency to possibly identify the source of
the problem prior to the service call and determine the specic
replacement components that may be required so the service
agency can arrive with the parts to x the problem.
SERVICE AGENCY INFORMATION
Fill in Below
MODEL NUMBER:
SERIAL NUMBER:
SERVICE COMPANY:
ADDRESS:
TELEPHONE (DAYTIME):
TELEPHONE (EMERGENCY)
NOTES:
Failure to follow these instruction exactly may result in
a re or explosion which can cause property damage,
personnel injury, and / or loss of life.
SECTION 3: STARTUP AND SHUTDOWN
INSTRUCTIONS
Safety Information
Read the safety instructions below before trying to start the
furnace.
1. This furnace does not have a pilot light. It is equipped with an
ignition device which automatically lights the burner. Do not
try to light the burner by hand.
2. Before starting the furnace, smell around the furnace area for
gas. Be sure to smell next to the oor because some gases are
heavier than air and will settle on the oor.
3. Only use a nger to push the gas control switch to the “ON”
position. Never use tools. If the switch will not operate by hand,
don’t try to repair it. Call a qualied service technician. Force or
attempted repair may result in a re or explosion.
4. Do not use this furnace if any part has been under water.
Immediately call a qualied service technician to inspect the
furnace and replace parts and controls that have been under
water.

MORTEX PRODUCTS INC 501 TERMINAL RD FORT WORTH, TX 76106 Page 7
Starting the Furnace
1. STOP! Read the safety information above.
2. Set the thermostat mode to“OFF”.
3. Turn o the electric power to the furnace.
4. Remove the furnace access panel.
5. Move the gas control switch to the“OFF”position. Do not
force it. See Figure 4 for the switch location.
6. Wait 5 minutes to clear out any gas. If gas is smelled, follow
Step 2 in the safety information above. If there is no gas
smell, go to Step 7 below.
7. Move gas control switch to the“ON”position. Do not force it.
See Figure 4 for the switch location.
8. Replace the burner access panel.
9. Turn on electrical power to the furnace.
10. Set the thermostat mode to“HEAT” and the temperature
setting above the room temperature. Burner will typically
light after 30-60 seconds, but it may take multiple tries due to
air in the gas line. The furnace will attempt to light the burner
3 times before it will lock out for 1 hour at which time it will try
to light again.
11. If the furnace will not light, follow the instructions“Shutting
the Furnace O” below.
Shutting the Furnace O
1. Set the thermostat mode to“OFF”.
2. Turn o the electrical power to the furnace if service is to be
performed.
3. Remove furnace access panel.
4. Move gas control switch to the“OFF”position.
5. Replace burner access panel.
The Furnace Fails to Operate Properly
If any abnormalities are observed while the furnace is operating,
perform the following checks:
1. Check the setting on the thermostat to make sure the
thermostat is set above the room temperature.
2. Check to see if the electrical power is turned on at the circuit
breakers at the main electrical panel (circuit breaker box) or
check any on/o switches that may be used for service
disconnect switches.
3. Make sure the air lters are clean, return grilles are not
obstructed, and supply air registers are open.
4. Make sure the control switch on the gas valve is in the
“ON” position. Refer to Figure 4 for the gas valve control switch
location.
5. Make sure the gas cock or valve shown in Figure 5 is in the
“ON” position.
If the cause of the malfunction is not obvious, do not attempt
to repair the furnace. Call a qualied service agency to repair
the furnace.
Should overheating occur, turn the gas cock or gas valve
in the gas supply line to the “OFF”position. After the
furnace has cooled o, turn the circuit breakers in the main
electrical panel (circuit breaker box) to the “OFF” position.
Call a qualied service personal to troubleshoot and repair
the furnace. Do not allow the furnace to continue to cycle
on the overtemperature limit switches.
Figure 4: White Rodgers Gas Valve Components
Figure 5: Gas Supply Piping & Shuto Valve Location

Pull the top out to remove
Air Filters are located on the back of this door
MORTEX PRODUCTS INC 501 TERMINAL RD FORT WORTH, TX 76106 Page 8
This furnace requires maintenance at the beginning of each heat-
ing season to assure proper operation. The annual service must be
performed by qualied service technician. The homeowner/user
is expected to perform general cleaning of the exterior surfaces,
clean dust from the louvers in the return air door, and replace-
ment of the air lters. Air lters must be checked every month
and replaced as needed. Figures 6 and 7 show the location of the
air lters in the louvered return air door. If the louvered return air
grille does not contain lters, the return air lters may be located
in a return air lter grille on the closet wall.
Before proceeding, make sure the area is well ventilated.
Turn the thermostat mode to“OFF”. If the circulating
blower is running, wait until it stops automatically. Follow
the “Shutting the Furnace O” instructions located in
Section 3: Startup and Shutdown Instructions on page
7 of this manual. Check all metal parts and surfaces to
make sure they have cooled to room temperature before
performing maintenance on the furnace.
SECTION 4: HOMEOWNER/USER MAINTENANCE
Figure 6: Louvered Return Air Door - Outside
Figure 7: Louvered Return Air Door Filter Rack
(Requires Two 16” x 20” x 1” High Velocity Air Filters)
Every time the lters are changed, the following items should be
visually inspected.
• Check combustion air and vent pipe for blockage.
• Check for leaks in the vent pipe.
• Check for dirt or lint on any surfaces or on components.
Do not try to clean any of the surfaces or components or try to
repair or replace any components. Cleaning of the furnace and
its components and repairing or replacing components must be
done by a qualied service professional.
• Check for excessive amounts of dirt and lint on components.
• Check for obvious damaged or deteriorated components or
surfaces.
• Check for water on any surface inside or outside of the furnace.
If during the visual inspection of the furnace any of the above
conditions are found, do not operate the furnace. Call a qualied
service technician to check, clean, or repair the furnace. The
service technician can provide additional information or answer
questions about the operation of the furnace and why the furnace
must be checked or cleaned.
If all components appear to be in good operating condition,
replace the front panels and follow the “Starting the Furnace”
instructions in Section 3: Startup and Shutdown Instructions on
page 7 of this manual.
Replacing Air Filters in the Louvered Return Air Door
All models require two 16”x 20” x 1” high velocity pleated air
lters which are located in the louvered return door on the front
of the furnace.
Follow the steps below to replace the air lters located in the
furnace louvered return air door.
1. Follow the procedure“Shutting the Furnace O” in Section 3:
Startup and Shutdown on page 7 of this manual.

MORTEX PRODUCTS INC 501 TERMINAL RD FORT WORTH, TX 76106 Page 9
2. Pull back on the top of the return air grille door until it pops
out of the retainer clip.
3. Let the top of the door fall outward and then lift up slightly
and outward and set the door on the oor.
4. Remove the center retaining bracket by pushing down on the
left side of the bracket then use a small at blade screwdriver
to pry it out.
5. Remove both air lters from the door. These lters are
disposable lters. Do not attempt to clean the lters and reuse
them.
6. Insert the replacement air lters in the door.
7. Place the center retaining bracket between the 2 air lters.
Slide the bracket under the ange on the left side of the door.
Place a at blade screwdriver between the bracket and
the right side door ange and slide the bracket past the door
ange until the bracket is back into place. Use a rubber mallet
to straighten the right side door ange if necessary.
8. Lift the door up against the cabinet and align the slots in the
bottom of the door with the tabs on the divider panel.
9. Push the door forward lining up the plastic door strike in the
top cover with the hinge in the door.
10. Push the top of the door on the left side forward until the door
strike snaps into the latch.
11. Push the top of the door on the right side forward until the
door strike snaps into the latch.
Follow the “Starting the Furnace” instructions in Section 3:
Startup and Shutdown Instructions on page 7 of this
manual.
Optional Return Air Filter Grille
Some installations may utilize one or more eld supplied return
air lter grilles that has been installed in the closet or alcove wall
above the furnace. If there are no lters in the furnace louvered
return air door, look for a return air lter grille or grilles on the wall
the closet or alcove. To replace the lters in a return air lter grille,
turn the thumbscrews or levers on the face of the grille door and
allow the grille door to fall outward providing access to the lter.
Replace the air lter in the return air lter grille with the same size
and type lter that was removed. Once the new lter is in place,
close the grille door and secure it with the thumbscrews or levers.

MORTEX PRODUCTS INC 501 TERMINAL RD FORT WORTH, TX 76106 Page 10
SERVICE AND MAINTENANCE MANUAL
THE HOMEOWNERS AND FURNACE USERS MUST STOP HERE!
This section has been designed to assist a qualied service
agency in performing service and maintenance on this furnace.
Homeowners or furnace users must never attempt to perform
maintenance or service on this furnace, especially when furnace
components must be replaced or adjusted.
The furnace manufacturer is not responsible for damage
to the furnace or furnace malfunctions due to improper
parts changes, improper maintenance, improper furnace
adjustments, or improper modications made by the
homeowner or furnace user.
The furnace manufacturer is not responsible for damages,
repairs, or injury if the homeowner or furnace user uses
this section of the instructions in an attempt to perform
maintenance or repairs to the furnace. This practice is very
dangerous and may result in property damage, personal
injury, or death due to a re, explosion, or electrical shock.
If the homeowner or the furnace user attempts to perform
any maintenance or repairs to this furnace, the warranty
will be voided and the homeowner will be responsible for
all repair costs and/or damages.
Improper adjustment, service or maintenance may create a
condition where the operation of the product could cause
property damage, personal injury, or death.
FIRE OR ELECTRICAL HAZARD
Failure to follow the safety warnings in this manual or on
labels axed to the furnace may result in a re or electrical
hazard which may cause property damage, serious injury,
or death.
This is a safety alert symbol. When this symbol is seen 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.
The following safety rules must be followed when servicing
this furnace.
CAUTION
CAUTION
This product must be serviced and maintained as specied
in these instructions and to any applicable local, state,
and national codes including, but not limited to building,
electrical, and mechanical codes.
SAFETY REQUIREMENTS
1. This gas red furnace is powered by a 115 volt, 60 Hz electrical
supply circuit. Check each electrical circuit with a meter to
be sure the power has been disconnected before servicing the
furnace.
2. Insulating materials may be combustible. This furnace must be
kept free and clear of insulating materials.
3. Follow the instructions in Section 3: Startup and Shutdown
Section of the User Information Manual to properly start or
shut the furnace o.
4. Make sure all moving parts have come to a complete stop
before the furnace door is removed to perform service or
maintenance. Moving parts can cause serious injury or death if
clothing or body parts get caught in the moving parts.
SECTION 1: SAFETY
ELECTRICAL SHOCK AND FIRE HAZARD
• Failure to follow the safety warnings in the manual or
on the labels axed to the furnace may result in property
damage, serious injury, or death.
• Improper servicing could result in property damage,
serious injury, or death.
• Placing jumper wires between the RED and WHITE
thermostat wires at the furnace in order to bypass the
thermostat and energize the heater is an extremely
dangerous practice that can result in damage to the
thermostat, property damage, serious injury, or death.
• Before servicing, disconnect all electrical power to the
furnace.
• When servicing controls, label all wires prior to
disconnecting to aid in proper reconnection of wires.
• Verify proper operation after servicing by turning the
thermostat above the room temperature for a brief period
of time to ensure future operation.

MORTEX PRODUCTS INC 501 TERMINAL RD FORT WORTH, TX 76106 Page 11
SECTION 2: FURNACE MAINTENANCE
This furnace must be inspected, cleaned, and adjusted by a
certied dealer or qualied service technician once a year or
before the start of each heating season. The following items must
be inspected, cleaned, serviced, or replaced if there are signs of
deterioration.
1. The roof jack vent terminal.
2. The furnace roof jack combustion air intake passageways.
Should it be necessary to service the vent / combustion air
intake system, this service must be conducted by a qualied
service agency. The operation of the furnace requires the vent
combustion air intake system to be sealed and have adequate
passageways for venting and combustion air to the furnace.
3. The burners, igniter, and ame sensor.
4. The circulating blower wheel and motor. Check for dirt, dust,
or debris in the blower wheel and motor.
5. The supply air duct system for excessive dust, dirt or debris.
6. The louvered return air door for excessive dust, dirt or debris.
7. All electrical wiring for wear or damage.
8. Check the air-conditioning coil for dust, debris or damage.
9. Check the air-conditioning coil drain pan for proper drainage
to prevent water backup into the furnace.
10. The furnace casing and all interior sheet metal panels or
dividers.
Furnace Cleaning Procedure
NOTE: The cleaning procedure listed below must be performed
by a qualied service agency only!
Burner Removal, Cleaning, and Reinstallation
The main burners should be removed and visually inspected
for dirt and debris accumulation during the annual inspection
and maintenance call. Follow the procedure below if cleaning of
burner is required.
1. Follow the instruction in Section 3: Startup and Shutdown
Instructions of the User Information Manual to properly
shut the furnace o.
2. Remove the burner compartment access panel on the front
of the furnace.
3. Turn o the valve in the gas supply line and loosen the
ground union joint. Refer to Figure 5 on page 7 of the User
Information Manual.
4. Remove the gas line from the gas valve. Be sure to use a
wrench on the gas valve hub (wrench boss) located on the
inlet side of the gas valve to keep the gas valve from rotating
when the gas line is being removed.
5. Remove the electrical wires from the terminals on the gas
valve.
6. Unplug the wires from the ame sensor and ignitor.
7. Remove the sixteen (16) screws from the burner mounting
plate and remove the burner assembly. Refer to Figure 8.
8. Lift the burner assembly up, turning slightly to clear the air
baes and slide the burner assembly back to remove it.
9. Remove dirt or debris using a small soft brush and a vacuum
cleaner.
10. Never clean the burners using water. Water will cause the
burner to corrode or rust.
11. Re-insert the burner assembly between the air baes and
slide forward until the burner mounting plate screw holes line
up with the holes in the burner box.
12. Secure the burner assembly to the burner box with the screws
that were removed in step 7.
13. Reconnect the ame sensor and igniter wires that were
disconnected in step 6.
14. Reconnect the electrical wires to the terminals on the gas
valve.
15. Connect the gas supply line. It is recommended that a new
pipe that is properly chamfered, reamed, and free of burrs and
chips be used. If the old pipe is reused, be sure it is clean and
free of rust, scale, burrs, chips, and old pipe joint compound.
16. Apply pipe joint compound that is approved for all gases only
to the male threads of the pipe joints. Do not apply compound
to the rst two threads nearest the end of the pipe.
17. Use a wrench on the gas valve hub (wrench boss) located
on the inlet side of the gas valve to prevent the gas valve from
rotating when the gas line is being tightened. Do not over
tighten the gas pipe which will damage the gas valve. Use
a torque wrench to tighten the inlet gas pipe to a maximum
of 375 in-lbs. If a torque wrench is not available, hand tighten
the pipe and then turn the pipe an additional ½ – ¾ turn or
until connection is snug and not leaking.
18. Connect the union joint and tighten the union.
19. Turn the manual gas valve to the“ON”position. Refer to
Figure 5.
20. Reinstall the burner compartment access panel on the front
of the furnace.
21. Follow the instructions as shown in Section 3: Startup and
Shutdown Instructions of the User Information Manual to
properly start the furnace.
Figure 8: Burner Assembly
Do not over-torque the gas supply pipe into the gas valve.
If the pipe is over tightened, the valve will be damaged.
The furnace manufacturer recommends hand tightening
the gas supply pipe, then tightening an additional ½ - ¾
turn with a wrench or until the connection is snug and not
leaking.
After the gas supply pipe has been tightened, check for
leaks with a commercially available soap solution made
specically for detection of leaks. Never test for gas leaks
with an open ame.

MORTEX PRODUCTS INC 501 TERMINAL RD FORT WORTH, TX 76106 Page 12
CARBON MONOXIDE HAZARD
If the gaskets on the combustion air blower assembly or
the ue box cover are damaged or deteriorated, leaks
in the combustion system may develop. Leaks in the
combustion system will cause incomplete combustion
which may allow high levels of carbon monoxide to leak
into the living space.
Under no circumstances should the furnace be operated
if the combustion air blower or ue box gaskets are
damaged or deteriorated. Turn the furnace o and do
not operate it until these gaskets have been replaced.
Figure 9: Heat Exchanger Assembly w/ Baes
Cleaning the Heat Exchanger
1. Remove the burner assembly as described in steps 1-8 in
“Burner Removal and Cleaning” on the previous page of this
manual.
2. Remove the combustion air baes from the burner box.
The combustion air baes are secured to the vestibule panel
with two screws on each bae located on the top and bottom
of the bae.
3. Use a brush and a vacuum cleaner to remove soot, dust, and
debris from the inside of the heat exchanger.
4. Check all of the baes for cracks or deterioration.
5. Use a mirror to check the bae inside the drum at the top of
the heat exchanger for cracks or deterioration.
6. Check the heat exchanger for any visible signs of cracks or
holes.
7. Use a brush and vacuum cleaner to clean soot, dust, and
debris from the inside of the burner box.
8. Reinstall the combustion air baes in the burner box.
The combustion air baes are secured to the vestibule panel
with two screws on each bae located on the top and bottom
of the bae.
9. Reinstall the burner assembly as described in steps 9-16 of
“Burner Removal and Cleaning” on the previous page of
this manual.

MORTEX PRODUCTS INC 501 TERMINAL RD FORT WORTH, TX 76106 Page 13
Cleaning the Flue Box Assembly
1. Follow the instructions in Section 3: Startup and Shutdown
Instructions of the User Information Manual to properly
shut this furnace down.
2. Remove the louvered return air lter door on the front of the
furnace.
3. Slide the roof jack combustion air and vent piping upward as
far as possible to remove the pipes from the combustion air
and vent anges at the top of the furnace.
4. Remove the 4 screws that secure the blend air adapter to the
top cover if a blend air system is being used.
5. Remove the 11 screws from the furnace top cover.
Figure 10: 4” Combustion Air Tube Flange
Figure 12: Flue Box Cover Screws
Figure 11: Top Cover Screws
and Combustion Air Pan Screws
6. Remove the three 1/4”-20 nuts next to the ue collar.
7. Remove the two 3/16”-16 Phillips head screws from the ange
at the top of the 4”combustion air pipe located inside the
blower compartment (See Figure 10).
8. Remove the 3 screws from the combustion pan cover. Refer to
Figure 11.
9. Remove the top cover. Be very careful not to damage the
insulation and the gaskets. If the insulation or the gaskets are
damaged, they must be replaced.
10. Remove the 16 screws from the ue box cover. Do not mix
these screws with the other screws as these are stainless steel
which is required due to the heat and corrosive ue products.
Refer to Figure 12 for screw locations.
11. Remove the ue box cover. Be very careful not to damage
the gasket on the ange. If the gasket is damaged, it must be
replaced.
12. Use a brush and vacuum cleaner to clean the tubes and the
ue box area.
NOTE: Debris removed from the wall of the tubes by the brush
will fall into the base of the heat exchanger. Be sure to vacuum
the base to remove the debris after brushing all of the tubes.
13. Place the ue box cover on top of the ue box base and secure
with the stainless steel screws that were removed in step 9.
NOTE: Inspect the gasket to make sure it is not damaged.
A good seal between the ue box cover and the ue box base
is required for the furnace to operate properly and to prevent
leakage of ue products into the conditioned space. Replace
the gasket if it is damaged.
14. Place the top cover on top of the furnace. Make sure the bolt
holes in the combustion air pan line up with the 1/4”-20 bolts
next to the ue collar.
NOTE: Inspect the gasket between the combustion air pan and
the ue box to make sure it is not damaged. Replace the
gasket if it is damaged. A good seal between the combustion
air pan and the ue box is required for the furnace for the
furnace to operate properly.
15. Install the three 1/4”-20 nuts on the three 3 bolts and tighten
until secure.
16. Install the 11 screws in the top cover and tighten until secure.
Do not over-tighten and strip these screws.
17. Place the blend air bracket over the 4” hole and align the screw
holes. Install the screws to secure it to the top cover. NOTE:
This step is not required if a blend air system is not used.
18. Install the louvered return air lter door on the front of the
furnace.
19. Follow the instructions in Section 3: Startup and Shutdown
Instructions of the User Information Manual to properly
start the furnace.

MORTEX PRODUCTS INC 501 TERMINAL RD FORT WORTH, TX 76106 Page 14
Figure 13: Flue Box Assembly
Cleaning the Combustion Air Assembly
The combustion air assembly should be removed and visually
inspected for dust and debris accumulation during the annual
inspection. If cleaning is required, follow the steps below.
1. Follow the instructions in Section 3: Startup and Shutdown
Instructions of the User Information Manual to properly
shut the furnace o.
2 Remove the louvered return air lter door on the front of the
furnace.
3. Remove the burner compartment access panel on the front of
the furnace.
4. Turn the valve in the gas supply line to the“OFF”position and
loosen the ground union joint (See Figure 5).
5. Remove the gas line from the gas valve. Use a wrench on the
gas valve hub (wrench boss) located on the inlet side of the
gas valve to prevent the gas valve from rotating when the gas
line is being removed.
6. Remove the wires from the gas valve terminals.
7. Unplug the wires from the ame sensor and igniter.
8. Remove the 10 screws from the burner mounting plate and
remove the burner assembly (See Figure 8).
9. Lift the burner assembly and turn it slightly too clear the air
baes and slide the burner assembly back to remove it.
10. Remove the 1/4” tube from the top right side of the burner box.
11. Remove the 4 screws that secure the combustion air baes to
the burner box / vestibule panel (See Figure 14).
12. Remove the 4 remaining screws that secure the burner box to
the vestibule panel. Be careful not to damage the gasket
on the back side of the burner box. If the gasket is damaged,
it must be replaced. A good seal between the burner box and
the vestibule panel is required for the furnace to operate
properly.
13. Remove the 2 Phillips head screws the secure the bottom of
the combustion air assembly to the 4”pipe.
14. Grasp the burner box and twist slightly while pulling down
to remove the 4” pipe from the combustion air housing
(See Figure 14).
15. Unplug the male and female insulated terminals that go to the
combustion air assembly.
16. Remove the 2 screws in the top of the combustion air housing
and remove the assembly from the upper 4”pipe (See Figure 14).
17. Use a soft bristle brush and vacuum cleaner to clean the dust
and debris from the housing, motor and prop fans. Be careful
not to damage the plastic fans. Use the vacuum cleaner when
brushing the pipe and fan to prevent the dust and debris from
entering the motor windings. Dust and debris will cause the
motor to run hotter and will reducing motor’s life.
18. Place the round black gasket on the 4”upper pipe so the pipe
sits inside the grove in the gasket and slide the combustion air
housing into the gasket. Secure the housing to the 4”pipe
with 2 screws removed in step 16. Make sure the gasket is
properly inserted into the pipe so there is a good seal at the
pipe and around the combustion air housing.
19. Place the round black gasket on the 4”lower pipe so that the
pipe sits inside the grove in the gasket and slide the combustion
air housing into the gasket. Secure the housing to the 4”pipe
with the 2 screws removed in step 13. Make sure the gasket is
properly inserted into the pipe so there is a good seal at the
pipe and around the combustion air housing.
20. Place the gasket on the back side of the burner box so it is
between the burner box and the vestibule panel. If the gasket
is damaged, it must be replaced. There must be a good seal
between the burner box and the vestibule panel for the
furnace to operate properly. Install the 4 screws that were
removed in step 11 and tighten until secure.
21. Place the combustion air baes into the burner box and use
the 4 screws that were removed in step 10 to secure the
baes to the burner box.
22. Connect the 1/4”tube to the nipple located on the top right
side of the burner box (See Figure 14).
23. Install the burner assembly and secure the assembly to the
burner box with the 10 screws that were removed in step 8.
24. Connect the 2 white wires to the igniter.
25. Connect the yellow wire to the ame sensor.
26. Connect the brown wires to the gas valve terminals.
27. Connect the gas supply line. It is recommended that a new
pipe that is properly chamfered, reamed, and free of burrs and
chips be installed. If the old pipe is reused, it must be clean
and free of rust, scale, burrs, chips, and old pipe joint compound.
28. Apply pipe joint compound that is approved for all gases only
to the male threads of the pipe joints. Do not apply compound
to the rst two threads nearest the end of the pipe.
29. Use a wrench on the gas valve hub (wrench boss) located on
the inlet side of the gas valve to prevent the gas valve from
rotating when the gas line is being tightened. Do not] over
tighten the gas pipe which will cause damage to the gas valve.
Use a torque wrench to tighten the pipe to a maximum of 375
in-lb. If a torque wrench is not available, tighten the gas pipe
by hand and then turn the pipe an additional ½ - ¾ turn or
until the connection is snug and not leaking.
30. Connect the union joint and tighten the union.
31. Turn the manual gas valve to the “ON” position (See Figure 5).
32. Check the entire gas supply line for leaks.
33. Install the burner compartment access panel on the furnace.
34. Install the louvered return air lter door on the furnace.
35. Follow the instructions in Section 3: Startup and Shutdown
Instructions of the User Information Manual to properly
start this furnace.
Cleaning the Indoor Fan Assembly
1. Follow the instructions in Section 3: Startup and Shutdown
Instructions of the User Information Manual to properly
shut the furnace o.
2. Remove the louvered return air lter door located on the front
of the furnace.
3. Remove the burner compartment access panel located on the
front of the furnace.
4. Unplug the blower motor wiring harness 6-pin plug located on
the right side of the control box.
5. Remove the 2 screws on the right side of the blower mounting
bracket.

MORTEX PRODUCTS INC 501 TERMINAL RD FORT WORTH, TX 76106 Page 15
Figure 14: Combustion Air Assembly
Figure 15: Blower Assembly
6. Remove the 2 screws on the left side of the blower mounting
bracket.
7. Lift the blower upward while moving it to the left and pull the
blower back to remove it.
8. Use a vacuum cleaner and a small brush to remove any dust
and debris from the blower compartment.
9. Check in the area below the blower compartment where the
heater exchanger tubes are located and remove any dust and
debris from around the heat exchanger tubes. Be careful not
to damage the heater exchangers with the vacuum hose or the
brush.
10. Place a piece of cardboard on top of the indoor cooling coil to
collect the dislodged dust and debris and prevent it from
falling on the coil.
11. Check the blower wheel for dust and debris. Use a brush and
vacuum cleaner to remove any dust or debris from the blower
wheel. Be careful not the move or accidentally remove the
balance weight(s) located on the blower wheel blades . If a
weight is moved or removed, the blower wheel will vibrate. If
the blower wheel is vibrating, it must be replaced.
12. Check the blower motor for dust and debris. Clean the
openings in the motor housing as these openings allow air
to enter and cool the motor windings. Dust and debris
blocking these openings will cause the motor to run hotter
than normal and will shorten the life of the motor.
13. Reinstall the blower assembly and secure the assembly using
the screws that were removed in steps 5 and 6.
14. Connect the blower motor wiring harness 6-pin plug to the
mating plug located on the right side of the control box.
15. Reinstall the burner compartment access panel on the front of
the furnace.
16. Reinstall the louvered return air lter door on the front of the
furnace.
17. Follow the instructions in Section 3: Startup and Shutdown
Instructions of the User Information Manual to properly
start the furnace.
The following describes the furnace controls and how they
operate. Refer to Figure 16 for component locations.
1. Limit Switch – An auto-reset over-temperature limit switch is
located on the vestibule panel to sense overheating of the heat
exchangers and its contacts will open if the temperature around
the switch rises above its set-point, shutting down the burner.
2. Manual Reset Limit Switch – A manual reset over-temperature
limit switch is located in the burner compartment to shut the
burner down if the switch contacts open due to overheating in
the blower compartment due to a failed blower motor.
3. Integrated Furnace Control Board – The integrated furnace
control board manages all control functions needed for the
operating of the furnace. The control board provides outputs for
3 speed taps for the circulating blower motor (heating, cooling,
and continuous fan), the induced draft blower, the main gas
valve, and the hot surface igniter. The control board receives
inputs from the thermostat, pressure switch, limit switches, and
ame sensor.
4. Pressure Switch – The pressure switch senses the negative
pressure in the induced draft blower housing and closes its
contacts when the negative pressure reaches the set point of
the switch.
5. Induced Draft Blower Assembly – The induced draft blower
assembly consists of a motor, blower wheel, and =
blower housing and draws the combustion air and by-products
of combustion through the heat exchanger tubes and forces
them up the exhaust vent.
6. 3 Amp Fuse – An automotive type fuse is located on the
integrated furnace control and is used for over-current
protection of the 24 VAC system control circuit.
7. Transformer – The transformer is used to step down voltage
from 115 VAC to 24 VAC and provides the required 24 VAC for
the system control circuit.
SECTION 3: FURNACE CONTROLS

MORTEX PRODUCTS INC 501 TERMINAL RD FORT WORTH, TX 76106 Page 16
Figure 16: Component Locations

MORTEX PRODUCTS INC 501 TERMINAL RD FORT WORTH, TX 76106 Page 17
SECTION 4: SEQUENCE OF OPERATION
Normal Heating Mode Sequence of Operation
1. Thermostat Call for Heat: The thermostat calls for heat by
energizing the“W” terminal.
2. Pressure Switch Proving: The control board checks to see the
pressure switch is open. If the pressure switch is closed when
the call for heat occurs, the control will lockout and begin to
ash a “2” fault code on the Status LED. If the pressure switch
contacts are open, the control board energizes the induced
draft blower and waits for the pressure switch contacts to close.
If the pressure switch contacts do not close within 60 seconds,
the control board will lockout, de-energize the induced draft
blower, and will ash a “3”fault code on the Status LED.
3. Pre-Purge: If the pressure switch contacts close, the control
board continues to energize the induced draft blower for a
25 second pre-purge period during which the pressure switch
contacts must remain closed.
4. Igniter Warm-Up: The control board energizes the hot surface
ignitor output for 25 seconds to allow the ignitor to warm up
to operating temperature. The induced draft blower remains
energized and the pressure switch must remain closed.
5. Ignition Activation Period: The control board energizes the
main gas valve for 5 seconds. The induce draft blower and
ignitor outputs remain energized.
6. Flame Proving Period and Blower On-Delay: The control board
de-energizes the hot surface igniter. The gas valve and induced
draft blower outputs remain energized. If ame is sensed at
the ame sensor 2 seconds after the igniter is de-energized,
the control board energizes the circulating blower motor on
the heating speed after a 30 seconds on-delay. The gas valve
and inducer outputs remain energized. If ame is not sensed,
the control board de-energizes the gas valve and initiates an
ignition retry as described in Ignition Re-Try below.
7. Steady-State Operation: The heating inputs are continuously
monitored by the control board to ensure the limit switch and
pressure switch contacts are closed, ame is present, and the
thermostat call for heat remains.
8. Post-Purge: When the thermostat call for heat is satised, the
control board de-energizes the gas valve. The induced draft
blower output remains energized for a 15-second post-purge
period.
9. Blower O-Delay: The circulating blower motor is de-energized
after the selected heating blower o-delay (100 or 150 seconds)
is completed. The blower o-delay timing begins when the
thermostat is satised.
Interrupted Thermostat Call
If the thermostat demand for heat is removed before the ame
recognition period has ended, the control board will continue to
energize the induced draft blower for the post-purge period and
de-energize all outputs.
If the thermostat demand for heat is removed after the ame
recognition period has ended (successful ignition), the induced
draft blower will continue to operate through a post-purge period
and the circulating blower motor will continue to operate on the
heating speed for the heating blower o-delay o period.
Ignition Retry
If ame is not established on the rst trial for ignition period,
the gas valve is de-energized and the induced draft blower
remains energized for an inter-purge period. The ignitor is then
re-energized for an ignitor warm up period and the control board
initiates another trial for ignition. This sequence repeats for up to
3 trials for ignition.
If ame is not established on the third trial for ignition (initial try +
2 re-tries), the control board de-energizes the gas valve, ashes a
“1”fault code on the Status LED, and lockouts out heat operation
for 1 hour and will then repeat the trial for ignition process.
Ignition Recycle
If ame is established for 10 seconds or longer and the ame is
then lost, the gas valve is de-energized, the induced draft blower
continues to operate, and an inter-purge period is initiated. The
circulating blower motor will remain energized on the selected
heating speed as long as there is a successful ignition and ame
is sensed prior to the end of the heating blower o-delay. When
the inter-purge period has ended, the ignitor is re-energized and
the control board initiates another ignitor warm-up and trial for
ignition. The control board will recycle up to 6 ame losses (5
re-cycles) within a single call for heat before entering the lockout
mode.
Call for Continuous Fan
When the thermostat calls for continuous fan (G) without a call
for heating or cooling, the control board energizes the circulating
blower motor on the continuous speed.
If a call for heat (W) occurs during continuous fan operation,
the circulating blower motor will be de-energized until after
a successful ignition and blower on-delay at which point the
circulating blower motor will be energized on the selected
heating speed.
When the thermostat FAN switch is moved to the OFF position,
the control board de-energizes the circulating blower motor.
Call for Cooling – Intermittent Blower
When the thermostat calls for cooling (Y), the circulating blower
motor is energized on the selected cooling speed after a 6 second
cooling blower on-delay. When the call for cooling is satised, the
control board de-energizes the circulating blower motor after the
45 second blower o-delay.
Limit Switch Open
Any time the limit switch contacts open, the gas valve and ignitor
will be de-energized, the circulating blower motor will continue
to operate on the selected HEAT speed, the induced draft blower
will run continuously, and the Status LED will ash a“4”fault code.
Limit Switch Re-Closes
If the limit switch contacts close after being open for less than
6 minutes, the induced draft blower will continue to operate
through a post-purge delay and the circulating blower will
continue to operate through the selected heating blower
o-delay. The control board will then attempt another ignition
cycle beginning with the pressure switch check.
Limit Switch Lockout
If the limit switch opens 3 times during the same call for heat and
re-closes each time, the control will enter a 1 hour lockout period
and will continuing to ash a“4” fault code on the Status LED
during the lockout period.
Limit Switch Remains Open
If the limit switch opens and remains open for more than 6
minutes and there is no ame sensed, the control board will
enter the fan failure lockout mode. The induced draft blower and

MORTEX PRODUCTS INC 501 TERMINAL RD FORT WORTH, TX 76106 Page 18
circulating blower motor will be de-energized and the control
board will enter the fan failure lockout mode until the thermostat
is reset or power to the furnace is cycling o and back on.
Pressure Switch Opens
If the pressure switch opens after ame has been established, the
control board de-energized the gas valve and initiates a normal
post-purge and blower heating o-delay. When the blower
heating o-delay is complete, the circulating blower motor is
de-energized. If the pressure switch closes, the control board
begins an ignition sequence if the thermostat is still calling for
heat.
The control board will ignore a pressure switch opening of
less than 2 seconds, but the gas valve will be de-energized
momentarily while the pressure switch is open which may cause
a loss of ame. If there is a loss of ame, the control board will
initiate the Ignition Recycle procedure.
If the pressure switch opens for more than 2 seconds during a
pre-purge or inter-purge period, the control board will wait for
the pressure switch to re-close. The purge time re-starts when
the pressure switch closes. If the pressure switch remains open
for 60 seconds, the control board will enter the lockout mode,
de-energize the induced draft blower, and begin to ash a “2” fault
code on the Status LED.
Undesired Flame
If ame is sensed while the gas valve is de-energized, the control
board will energize the induced draft blower and circulating
blower motor on heating speed. All other outputs will remain o
and the Status LED will ash a“5”fault code. When ame is no
longer sensed, the induced draft blower will enter a post-purge
period and the circulating blower motor will continue to operate
until selected heating blower o-delay is completed. The control
will not be locked out and continue with normal operation
following the blower o-delay.
Lockout
Soft Lockout: The gas valve will be de-energized and the control
board will not initiate an ignition attempt. The control board
will still respond to an open limit switch and undesired ame by
energizing the induced draft blower and circulating blower motor.
The control board will automatically exit the lockout mode after
1 hour. The control can be manually forced to exit the lockout
mode by cycling the electrical power to the furnace o and then
back on or removing the thermostat call for heat for more than 2
seconds.
Hard Lockout: If a gas valve hardware fault, a ame sense
hardware fault has occurred or if the limit switch is open for
more than 5 minutes, the control board will enter a hard lockout
condition. To exit a hard lockout, electrical power to the furnace
must be cycled o and then back on or the thermostat call for
heat must be removed.
For personnel safety, turn the electrical power“OFF” at
the main electrical panel (circuit breaker box) and at the
furnace before attempting any service or maintenance
operations. Homeowners must never attempt to perform
any maintenance on the furnace or remove any furnace
access panels except for removing the louvered return air
lter door when replacing the lters with the electrical
power to the furnace disconnected.
SECTION 5: TROUBLESHOOTING
The following checks should be made before troubleshooting
the furnace controls for a no-heat issue. If the integrated furnace
control board Status LED is not on, perform the following checks.
1. Check the circuit breakers or fuses that supply line voltage
electrical power to the furnace to make sure they are in the
“ON” position and have not tripped.
2. Check any “ON/OFF”switches that are external to the furnace
to make sure they are turned on.
3. Check to make sure the connections to the line voltage
electrical supply pigtails are secure.
4. Check for a loose or missing ground wire to the furnace.
5. Check for loose wiring connections on the 115 VAC power
supply control board terminals.
6. Check for loose connections on the integrated furnace control
board terminals.
7. Check the control board is connected securely to the chassis
ground connection.
8. Check for 24 VAC between the“R”and “COM” terminals on
the control board. If 24 VAC is not present, check for a failed
transformer.
9. If 24 VAC is present between the“R”and“COM” terminals on
the control board, check for 24 VAC between the“W”and
“COM”terminals. If 24 VAC is not present between the“W”
and“COM” terminals, replace the control board.
10. Check for loose wiring connections on the furnace components.
11. Check all gas line shuto valves to make sure the valves are in
the“ON”position.
12. If the furnace is operating, but not operating correctly,
review Section 4: Sequence of Operation to determine
which component is malfunctioning.
Integrated Furnace Control Board Diagnostics
The control continuously monitors its own operation and the
operation of the system. A green LED labeled “STATUS”is provided
on control board to indicate system status and faults. Below is a
guide to the Status LED codes. If a failure occurs, the STATUS LED
will indicate the failure code by the number of ashes. If the LED
is on and not ashing, the control is operating normally. If the LED
is o, the power to the control is o, the 3 amp fuse on the control
board has blown, or the control board is defective. Check the
power to the control board and check to see if the fuse is blown.
If there is 115 VAC between the control board “L1”and“NEUTRAL”
terminals and 24 VAC between the control board “R”and “C”
terminals and the STATUS LED is not on, the board is defective and
must be replaced.

MORTEX PRODUCTS INC 501 TERMINAL RD FORT WORTH, TX 76106 Page 19
Integrated Control Board Diagnostic Codes
1 Flash - System Lockout. Ignition Retries Exceeded
Failure to sense ame is often caused by carbon deposits on the
ame sensor, a disconnected or shorted ame sensor lead, or a
poorly grounded furnace. Carbon deposits can be cleaned with
emery cloth or steel wool. Verify the sensor is not contacting the
burner and is located in a good position to sense ame.
The ignitor must be positioned to light the gas when the valve
opens. If the ignitor has been replaced, verify the position has not
changed.
Check sensor lead for shorting and verify the furnace is grounded
properly. Verify the gas supply to gas valve, the gas valve is in the
“ON”position and is furnace lighting properly. Verify ame engulfs
the ame sensor during ignition attempts and gas pressures are
correct.
2 Flashes - Pressure Switch Stuck Closed
Check the pressure switch function and verify the combustion air
motor is o.
3 Flashes - Pressure Switch Stuck Open
Check pressure switch function and tubing. Verify the combustion
air motor is running and pulling sucient vacuum to engage
pressure switch.
4 Flashes - Open Limit Switch
Verify continuity through the main limit switch located in the
control box and the manual reset limit switch located next to the
blower.
5 Flashes - Flame Sensed More Than 4.24 seconds After Gas
Valve is De-Energized.
Verify the gas valve is opening and shutting down properly. Flame
in burner assembly should extinguish promptly at the end of the
cycle. Check orice and gas pressure.
6 Flashes – Flame Rollout Switch Open
The furnace does not have a rollout switch. The 12 pin plug has a
purple jumper wire in place of the switch. Check the jumper wire
to be sure it is securely inserted into the plug.
7 Flashes - Low Flame Sense Signal
Low ame sense current is often caused by carbon deposits on
the ame sensor, a poorly grounded furnace or a mis-aligned
ame sense probe. Carbon deposits can be cleaned with emery
cloth or steel wool. Check furnace and control board grounding.
Verify the ame sensor is located in the ame. The minimum
current for proper operation is 0.5 DC micro amps.
8 Flashes - Ignitor Relay Fault
The ignitor relay on the control board has failed. Replace the
control board.
9 Flashes - Twinning Fault
If twinning is used, verify eld installed wiring is connected
correctly. Verify both control boards are the same model.
10 Flashes - Open Fuse
Verify the 3 amp fuse on the control board has opened. Verify
there are no shorted circuits and replace the fuse.
11 Flashes - Ignitor Open (External to the Control)
Verify the ignitor is operating correctly and has not failed by
checking to see if it glows during the ignition cycle. If it does not
glow during the ignition cycle, replace the ignitor.
12 Flashes - Combustion Air Blower Relay Error
The relay built into the control board has failed. Replace the
control board.
Rapid Flash - Reverse Polarity
Reverse the incoming power wires connected to the control
board“L1”and “Neutral” terminals.
Continuous On - Normal Operation - No Fault
O - Control Failure / No Power / Internal Fault / IEQ Loss
Verify there is 115 VAC across the control board“L1”and “Neutral”
terminals. Replace control if power is at the control and the LED is
o.
Fault Code Retrieval: The control will ash the last 5 fault codes
that occurred when the push button is pressed to give the service
tech more troubleshooting capability. The last fault code is
ashed rst.
Flame Sense Current
Normal ame sense current is approximately 2.8 micro amps DC.
Minimum ame sense current threshold is 0.5 micro amps DC.
Checking and Adjusting the Gas Inlet Pressure
1. Follow the procedure for “Shutting The Furnace O” located
in Section 3: Startup and Shutdown Instructions in the User
Information Manual.
2. Turn the switch on the gas valve to the“OFF”position. Refer to
Figure 18 for switch location.
3. Turn o the gas supply at the ball valve or gas cock upstream
of the gas valve.
4. Locate the furnace gas control.
5. Find the gas valve pressure ports labeled“IN P”which is the
inlet or line pressure tap (See Figure 18) and remove the
pressure port cap.
6. Use a 3/32” (2.4 mm) Allen wrench to loosen the “IN P”port set
screw by turning it counter clockwise one (1) turn only.
DO NOT REMOVE THE SET SCREW.
7. Connect the 1/8” (3.175 mm) ID exible tubing to the positive
side of the“U” tube monometer or pressure gauge and the
other end of the tubing to the port marked “IN P” on the gas
valve as shown in Figure 19.
8. Turn the ON/OFF switch on the gas control to the“ON”position.
9. Follow the “Starting the Furnace” instructions located in
Section 3: Startup and Shutdown Instructions in the User
Information Manual to properly start the furnace.
10. Check the line pressure. If the pressure is at the pressure
specied in Table 1, go to step 10. If the pressure is not at the
correct pressure, adjust the pressure at the regulator upstream
of the gas valve while the furnace is operating until the correct
pressure is measured at the gas valve pressure port.
11. Follow the procedure to “Shutting the Furnace O”
instructions located in Section 3: Startup and Shutdown
Instructions in the User Information Manual.
12. Turn the switch on the gas valve to the “OFF” position.
13. Turn o the gas supply at the ball valve or gas cock upstream
of the gas valve.
14. Remove the“U”tube monometer or pressure gauge from “IN
P” and tighten the set screw. Replace the pressure port cap.
15. After the correct inlet pressure has been conrmed, follow the
instructions on the next page for checking the manifold
pressure.

MORTEX PRODUCTS INC 501 TERMINAL RD FORT WORTH, TX 76106 Page 20
Figure 17: White Rodgers Gas Valve
Figure 18: Measuring Inlet (Supply)
Gas Pressure (IN P)
Figure 19: Measuring Outlet (Manifold)
Gas Pressure (OUT P)
Table 1: Inlet (Supply) Gas Line Pressure Range
Table 2: Nominal Manifold Gas Pressure
INLET GAS PRESSURE RANGE
NATURAL GAS PROPANE (LP)
MINUMUM 4.5”W.C. (1.12 kPa) 11.0”W.C. (2.74 kPa)
MAXIMUM 10.5”W.C. (2.21 kPa) 13.0”W.C. (3.24 kPa)
NOMINAL MANIFOLD PRESSURE
NATURAL GAS 3.5”W.C. (0.87 kPa)
PROPANE (LP) GAS 10.0”W.C. (2.49 kPa)
Checking the Manifold Pressure
1. Find the gas valve pressure ports labeled “OUT P” (See Figure
18). OUT P is the manifold pressure tap.
2. Use a 3/32”(2.4 mm) Allen wrench to loosen the set screw by
turning it counter clockwise one (1) turn only on the “IN P”port.
DO NOT REMOVE THE SET SCREW.
3. Connect the 1/8”(3.175 mm) ID exible tubing to the positive
side of the “U” tube monometer or pressure gauge and the
other end of the tubing to the port marked“IN P” on the gas
valve as shown in Figure 20.
4. Follow the “Starting the Furnace” instructions located in
Section 3: Startup and Shutdown Instructions in the User
Information Manual to properly start the furnace.
5. With the furnace operating, read the manifold pressure. The
pressure should be between 3.3”W.C. and 3.6”W.C. for natural
gas and 9.8”W.C. and 10.2”W.C. for propane (LP). Check the
input using the calculations in Table 3 or Table 4. page. If the
input is not within 8% of the input listed on the furnace data
plate, replace the gas valve.
6. Turn the switch on the gas valve to the “OFF” position.
7. Remove the pressure hose from the pressure port and tighten
the set screw.
8. Follow the “Starting the Furnace” instructions located in
Section 3: Startup and Shutdown Instructions in the User
Information Manual to properly start the furnace.
9. Proceed to Temperature Rise Check and Adjustment.
Checking the Furnace Input Rate
The gas pressure regulator in the combination gas control is
adjusted at the factory for average gas conditions. It is important
that gas be supplied to the furnace in accordance with the input
rating listed on the furnace data plate. Actual input should be
checked and necessary adjustments made after the furnace is
installed. Over-ring, a result of excessive gas input, reduces
the life of the furnace and increases maintenance. Under no
circumstances should the input exceed that shown on the data
plate.
Input can be determined by the meter-timing method as long as
all other gas burning appliances connected to the meter are o
during the test. If this is not possible, use the pressure method.
“IMPORTANT”: Inlet pressure and manifold pressure must
be checked with the furnace operating when making nal
adjustments.
Meter Timing Method
1. Shut o all other gas-burning appliances served by the gas
meter, including those with pilot lights.
2. Start the furnace and determine the number of seconds it
takes to consume 2 cu. ft. or 0.1 cu. meter of natural gas or 1 cu.
ft. or 0.05 cu. meter of propane gas. Refer to Table 3 or Table 4
for the procedure for calculating heating input.
The heating value of gas may be obtained from the local utility or
gas dealer. If the utility or gas dealer does not know the heating
value of the gas you may use the values shown below:
Use 1030 BTU/cu. ft. (38.4 Mj/m³) for natural gas
Use 2500 BTU/cu. ft. (93.15 Mj/m³) for propane gas
BTU/cu. ft. or Mj/m³ = heating value of gas