INSTALLATION
INSTRUCTIONS
ML193DF
E 2010 Lennox Industries Inc.
Dallas, Texas, USA
®
MERIT SERIES GAS FURNACE
DOWNFLOW AIR DISCHARGE
506475−01
01/2011
Supersedes 10/2010
Litho U.S.A.
THIS MANUAL MUST BE LEFT WITH THE
HOMEOWNER FOR FUTURE REFERENCE
This is a safety alert symbol and should never be ignored.
When you see this symbol on labels or in manuals, be alert
to the potential for personal injury or death.
CAUTION
As with any mechanical equipment, personal injury
can result from contact with sharp sheet metal
edges. Be careful when you handle this equipment.
DOWNFLOW
WARNING
Improper installation, adjustment, alteration, service
or maintenance can cause property damage, person-
al injury or loss of life. Installation and service must
be performed by a licensed professional installer (or
equivalent), service agency or the gas supplier.
AIR FLOW
Table of Contents
Unit Dimensions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
ML193DF Parts Arrangement . . . . . . . . . . . . . . . . . . . . . 3
ML193DF Gas Furnace . . . . . . . . . . . . . . . . . . . . . . . . . . 4
Shipping and Packing List . . . . . . . . . . . . . . . . . . . . . . . . 4
Safety Information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
Use of Furnace as a Construction Heater . . . . . . . . . . . 5
General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
Combustion, Dilution and Ventilation Air . . . . . . . . . . . . 6
Vent Piping Guidelines . . . . . . . . . . . . . . . . . . . . . . . . . . 15
Gas Piping . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30
Electrical . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32
Unit Start Up . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36
Gas Pressure Measurement . . . . . . . . . . . . . . . . . . . . . 38
Proper Combustion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38
High Altitude . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38
Testing Non Direct Appliances for Proper Air . . . . . . . 39
Other Unit Adjustments . . . . . . . . . . . . . . . . . . . . . . . . . . 40
Blower Motor Performance . . . . . . . . . . . . . . . . . . . . . . . 41
Service . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42
Planned Service . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44
Integrated Control Diagnostic Codes . . . . . . . . . . . . . . 44
Troubleshooting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45
Repair Parts List . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49
Start Up Checklist . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50
Setting Equipment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
Filters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
Duct System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
Pipe and Fittings Specifications . . . . . . . . . . . . . . . . . . . 12
Joint Cementing Procedure . . . . . . . . . . . . . . . . . . . . . . 14
Venting Practices . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
01/11
506475−01
Page 1
*2P0111*
*P506475-01*
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ML193DF Parts Arrangement
CONTROL BOX
(Includes integrated control,
transformer and door switch)
BAG ASSEMBLY
BLOWER MOTOR
(hidden)
BLOWER
ACCESS
PANEL
COMBUSTION
AIR INDUCER
BLOWER DECK
PRIMARY LIMIT
COLD END HEADER BOX
BURNER
ACCESS
PANEL
HEAT EXCHANGER
GAS VALVE
BURNER BOX ASSEMBLY
(includes sensor, rollout switches and ignitor)
FIGURE 1
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Check equipment for shipping damage. If you find any
damage, immediately contact the last carrier.
The following items may also be ordered separately:
1 − Thermostat
ML193DF Gas Furnace
The ML193DF Category IV gas furnace is shipped ready
for installation in the downflow position.
The furnace is equipped for installation in natural gas ap-
plications. A conversion kit (ordered separately) is re-
quired for use in propane/LP gas applications.
1 − Propane/LP changeover kit
Safety Information
The ML193DF can be installed as a Direct Vent or Non−
Direct Vent gas central furnace.
WARNING
NOTE − In Direct Vent installations, combustion air is taken
from outdoors and flue gases are discharged outdoors. In
Non−Direct Vent installations, combustion air is taken from
indoors and flue gases are discharged outdoors. See figure
2 for applications involving roof termination.
Improper installation, adjustment, alteration, service
or maintenance can cause property damage, person-
al injury or loss of life. Installation and service must
be performed by a licensed professional installer (or
equivalent), service agency or the gas supplier.
DIRECT VENT INSTALLATION
NON−DIRECT VENT
INSTALLATION
CAUTION
As with any mechanical equipment, personal injury
can result from contact with sharp sheet metal
edges. Be careful when you handle this equipment.
EXHAUST
OUTLET
EXHAUST
OUTLET
COMBUSTION
AIR INTAKE
OUTSIDE OF
HOUSE
Use only the type of gas approved for use with this furnace.
Refer to unit nameplate.
ML193DF units are CSA International certified to ANSI
Z21.47 and CSA 2.3 standards.
COMBUSTION
AIR INTAKE INSIDE
OF HOUSE
Building Codes
In the USA, installation of gas furnaces must conform with lo-
cal building codes. In the absence of local codes, units must
be installed according to the current National Fuel Gas Code
(ANSI-Z223.1/NFPA 54). The National Fuel Gas Code is
available from the following address:
ML193DF
ML193DF
American National Standards Institute, Inc.
11 West 42nd Street
New York, NY 10036
FIGURE 2
Shipping and Packing List
In Canada, installation must conform with current National
Standard of Canada CSA-B149 Natural Gas and Propane
Installation Codes, local plumbing or waste water codes
and other applicable local codes.
Package 1 of 1 contains
1 − Assembled ML193DF unit
1 − Bag assembly containing the following:
3 −Wire nuts
In order to ensure proper unit operation in non−direct vent
applications, combustion and ventilation air supply must be
provided according to the current National Fuel Gas Code
or CSA-B149 standard.
1 −Snap bushing
1 −Snap plug
Locations and Clearances
1 − Wire tie
This furnace is CSA International certified for installation
clearances to combustible material as listed on the unit
vice clearances must take precedence over fire protection
clearances.
1 −Condensate trap
1 −Condensate trap cap
1 −Condensate trap clamp
1 −2" diameter Air intake screen
For installation in a residential garage, the furnace must
be installed so that the burner(s) and the ignition source
are located no less than 18 inches (457 mm) above the
floor. The furnace must be located or protected to avoid
physical damage by vehicles. When a furnace is installed
in apublic garage, hangar, or other building that has a haz-
ardous atmosphere, the furnace must be installed accord-
ing to recommended good practice requirements and cur-
rent National Fuel Gas Code or CSA B149 standards.
DANGER
Danger of explosion.
There are circumstances in which odorant used with
LP/propane gas can lose its scent. In case of a leak,
LP/propane gas will settle close to the floor and may
be difficult to smell. An LP/propane leak detector
should be installed in all LP applications.
Page 4
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NOTE − Furnace must be adjusted to obtain a temperature
rise within the range specified on the unit nameplate. Failure
to do so may cause erratic limit operation and premature heat
exchanger failure.
tent operation down to 55°F (13°C) dry bulb for cases
where a night setback thermostat is used. Return air tem-
perature must not exceed 85°F (29°C) dry bulb.
The ML193DF furnace may be installed in alcoves, closets,
attics, basements, garages, utility rooms and crawl
spaces.
This ML193DF furnace must be installed so that its electri-
cal components are protected from water.
Installation in Combination with a Cooling Coil
This furnace design has not been CSA certified for installa-
tion in mobile homes, recreational vehicles, or outdoors.
shall be installed in parallel with, or on the upstream side of,
cooling units to avoid condensation in the heating compart-
ment. With a parallel flow arrangement, a damper (or other
means to control the flow of air) must adequately prevent
chilled air from entering the furnace. If the damper is manu-
ally operated, it must be equipped to prevent operation of ei-
ther the heating or the cooling unit, unless it is in the full
HEAT or COOL setting.
Never use an open flame to test for gas leaks. Check all
connections using a commercially available soap solution
made specifically for leak detection.
Use of Furnace as Construction Heater
Lennox does not recommend the use of ML193DF units as
a construction heater during any phase of construction.
Very low return air temperatures, harmful vapors and op-
eration of the unit with clogged or misplaced filters will dam-
age the unit.
When installed, this furnace must be electrically grounded
according to local codes. In addition, in the United States,
installation must conform with the current National Electric
Code, ANSI/NFPA No. 70. The National Electric Code
(ANSI/NFPA No. 70) is available from the following ad-
dress:
ML193DF units may be used for heating of buildings or
structures under construction, if the following conditions
are met:
National Fire Protection Association
1 Battery March Park
Quincy, MA 02269
• The vent system must be permanently installed per
these installation instructions.
• A room thermostat must control the furnace. The use of
fixed jumpers that will provide continuous heating is not
allowed.
In Canada, all electrical wiring and grounding for the unit
must be installed according to the current regulations of the
Canadian Electrical Code Part I (CSA Standard C22.1)
and/or local codes.
• The return air duct must be provided and sealed to the
furnace.
Heating Unit Installed Parallell to Air Handler Unit
• Return air temperature range between 60°F (16°C) and
80°F (27°C) must be maintained.
• Air filters must be installed in the system and must be
maintained during construction.
• Air filters must be replaced upon construction comple-
tion.
AIR HANDLER
GAS UNIT
• The input rate and temperature rise must be set per the
furnace rating plate.
• One hundred percent (100%) outdoor air must be pro-
vided for combustion air requirements during construc-
tion. Temporary ducting may supply outdoor air to the
furnace. Do not connect duct directly to the furnace.
Size the temporary duct following these instructions in
section for Combustion, Dilution and Ventilation Air in a
confined space with air from outside.
Dampers
(open during cooling
operation only)
Dampers
(open during heating
operation only)
• The furnace heat exchanger, components, duct system,
air filters and evaporator coils must be thoroughly
cleaned following final construction clean−up.
FIGURE 3
• All furnace operating conditions (including ignition, in-
put rate, temperature rise and venting) must be verified
according to these installation instructions.
NOTE − This furnace is designed for a minimum continu-
ous return air temperature of 60°F (16°C) or an intermit-
Page 5
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General
WARNING
These instructions are intended as a general guide and do
not supersede local codes in any way. Consult authorities
having jurisdiction before installation.
Insufficient combustion air can cause headaches,
nausea, dizziness or asphyxiation. It will also cause
excess water in the heat exchanger resulting in rust-
ing and premature heat exchanger failure. Excessive
exposure to contaminated combustion air will result
in safety and performance related problems. Avoid
exposure to the following substances in the com-
bustion air supply:
In addition to the requirements outlined previously, the fol-
lowing general recommendations must be considered
when installing a ML193DF furnace:
• Place the furnace as close to the center of the air dis-
tribution system as possible. The furnace should also be
located close to the chimney or vent termination point.
Permanent wave solutions
Chlorinated waxes and cleaners
Chlorine base 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, etc.
Hydrochloric acid
• When the furnace is installed in non−direct vent applica-
tions, do not install the furnace where drafts might blow
directly into it. This could cause improper combustion
and unsafe operation.
• When the furnace is installed in non−direct vent applica-
tions, do not block the furnace combustion air opening
with clothing, boxes, doors, etc. Air is needed for proper
combustion and safe unit operation.
Cements and glues
Antistatic fabric softeners for clothes dryers
Masonry acid washing materials
• When the furnace is installed in an attic or other insu-
lated space, keep insulation away from the furnace.
• When the furnace is installed in an unconditioned
space, consider provisions required to prevent freezing
of condensate drain system.
In the past, there was no problem in bringing in sufficient
outdoor air for combustion. Infiltration provided all the air
that was needed. In today’s homes, tight construction
practices make it necessary to bring in air from outside
for combustion. Take into account that exhaust fans, ap-
pliance vents, chimneys, and fireplaces force additional
air that could be used for combustion out of the house.
Unless outside air is brought into the house for combus-
tion, negative pressure (outside pressure is greater than
inside pressure) will build to the point that a downdraft
can occur in the furnace vent pipe or chimney. As a result,
combustion gases enter the living space creating a po-
tentially dangerous situation.
CAUTION
ML193DF unit should not be installed in areas nor-
mally subject to freezing temperatures.
WARNING
Product contains fiberglass wool.
Disturbing the insulation in this product during
installation, maintenance, or repair will expose you
to fiberglass wool. Breathing this may cause lung
cancer. (Fiberglass wool is known to the State of Cal-
ifornia to cause cancer.)
In the absence of local codes concerning air for combus−
tion and ventilation, use the guidelines and procedures in
this section to install ML193DF furnaces to ensure effi-
cient and safe operation. You must consider combustion
air needs and requirements for exhaust vents and gas
pip−ing. A portion of this information has been reprinted
with permission from the National Fuel Gas Code (ANSI−
Z223.1/NFPA 54). This reprinted material is not the com-
plete and official position of the ANSI on the referenced
subject, which is represented only by the standard in its
entirety.
Fiberglass wool may also cause respiratory, skin,
and eye irritation.
To reduce exposure to this substance or for further
information, consult material safety data sheets
available from address shown below, or contact your
supervisor.
Lennox Industries Inc.
P.O. Box 799900
Dallas, TX 75379−9900
In Canada, refer to the CSA B149 installation codes.
Combustion, Dilution & Ventilation Air
If the ML193DF is installed as a Non−Direct Vent Fur-
nace, follow the guidelines in this section.
CAUTION
Do not install the furnace in a corrosive or contami-
nated atmosphere. Meet all combustion and ventila-
tion air requirements, as well as all local codes.
NOTE − In Non−Direct Vent installations, combustion air
is taken from indoors and flue gases are discharged out−
doors.
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All gas-fired appliances require air for the combustion pro-
cess. If sufficient combustion air is not available, the fur-
nace or other appliance will operate inefficiently and un-
safely. Enough air must be provided to meet the needs of all
fuel−burning appliances and appliances such as exhaust
fans which force air out of the house. When fireplaces, ex-
haust fans, or clothes dryers are used at the same time as
the furnace, much more air is required to ensure proper
combustion and to prevent a downdraft. Insufficient air
causes incomplete combustion which can result in carbon
monoxide.
dangerous negative pressure condition. Air for combustion
and ventilation can be brought into the confined space ei-
ther from inside the building or from outside.
Air from Inside
If the confined space that houses the furnace adjoins a
space categorized as unconfined, air can be brought in by
providing two permanent openings between the two
spaces. Each opening must have a minimum free area of 1
2
square inch (645 mm ) per 1,000 Btu (.29 kW) per hour of
total input rating of all gas−fired equipment in the confined
space. Each opening must be at least 100 square inches
2
In addition to providing combustion air, fresh outdoor air di-
lutes contaminants in the indoor air. These contaminants
may include bleaches, adhesives, detergents, solvents
and other contaminants which can corrode furnace compo-
nents.
(64516 mm ). One opening shall be within 12 inches (305
mm) of the top of the enclosure and one opening within 12
EQUIPMENT IN CONFINED SPACE − ALL AIR FROM INSIDE
The requirements for providing air for combustion and ven-
tilation depend largely on whether the furnace is installed in
an unconfined or a confined space.
ROOF TERMINATED
EXHAUST PIPE
Unconfined Space
An unconfined space is an area such as a basement or
large equipment room with a volume greater than 50 cubic
3
OPENINGS
(To Adjacent
feet (1.42 m ) per 1,000 Btu (.29 kW) per hour of the com-
SIDE WALL
TERMINATED
EXHAUST PIPE
(ALTERNATE
LOCATION)
Unconfined
Space)
bined input rating of all appliances installed in that space.
This space also includes adjacent rooms which are not
separated by a door. Though an area may appear to be un-
confined, it might be necessary to bring in outdoor air for
combustion if the structure does not provide enough air by
infiltration. If the furnace is located in a building of tight
construction with weather stripping and caulking around
the windows and doors, follow the procedures in the air
from outside section.
NOTE − Each opening shall have a free area of at least one square
2
inch per 1,000 Btu (645mm per .29kW) per hour of the total input
rating of all equipment in the enclosure, but not less than 100 square
2).
inches (64516mm.
FIGURE 4
Confined Space
Air from Outside
If air from outside is brought in for combustion and ventila-
tion, the confined space shall be provided with two perma-
nent openings. One opening shall be within 12" (305mm)
of the top of the enclosure and one within 12" (305mm) of
the bottom. These openings must communicate directly
or by ducts with the outdoors or spaces (crawl or attic) that
freely communicate with the outdoors or indirectly
through vertical ducts. Each opening shall have a mini-
A confined space is an area with a volume less than 50 cubic
3
feet (1.42 m ) per 1,000 Btu (.29 kW) per hour of the com−
bined input rating of all appliances installed in that space. This
definition includes furnace closets or small equipment rooms.
When the furnace is installed so that supply ducts carry air
circulated by the furnace to areas outside the space con-
taining the furnace, the return air must be handled by ducts
which are sealed to the furnace casing and which terminate
outside the space containing the furnace. This is especially
important when the furnace is mounted on a platform in a
confined space such as a closet or small equipment room.
Even a small leak around the base of the unit at the platform
or at the return air duct connection can cause a potentially
2
mum free area of 1 square inch per 4,000 Btu (645mm
per 1.17kW) per hour of total input rating of all equipment
in the enclosure. When communicating with the outdoors
through horizontal ducts, each opening shall have a mini-
2
mum free area of 1 square inch per 2,000 Btu (645mm
per .59kW) per total input rating of all equipment in the en-
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EQUIPMENT IN CONFINED SPACE − ALL AIR FROM OUTSIDE
(Inlet Air from Crawl Space and Outlet Air to Ventilated Attic)
EQUIPMENT IN CONFINED SPACE − ALL AIR FROM OUTSIDE
(All Air Through Ventilated Attic)
VENTILATION LOUVERS
(Each end of attic)
ROOF TERMINATED
EXHAUST PIPE
VENTILATION LOUVERS
(Each end of attic)
ROOF TERMINATED
EXHAUST PIPE
OUTLET
AIR
OUTLET
AIR
INLET AIR
(Ends 12" above
bottom)
SIDE WALL
TERMINATED
EXHAUST PIPE
(ALTERNATE
LOCATION)
SIDE WALL
TERMINATED
VENTILATION
EXHAUST PIPE
LOUVERS
(ALTERNATE
LOCATION)
INLET
AIR
(For unheated
crawl space)
NOTE−The inlet and outlet air openings shall each have a free area of
2
at least one square inch per 4,000 Btu (645mm per 1.17kW) per
hour of the total input rating of all equipment in the enclosure.
NOTE−The inlet and outlet air openings shall each have a free area
2
of at least one square inch per 4,000 Btu (645mm per 1.17kW) per
hour of the total input rating of all equipment in the enclosure.
FIGURE 6
EQUIPMENT IN CONFINED SPACE −
ALL AIR FROM OUTSIDE
FIGURE 5
ROOF TERMINATED
EXHAUST PIPE
If air from outside is brought in for combustion and ventila-
tion, the confined space must have two permanent open-
ings. One opening shall be within 12 inches (305 mm) of
the top of the enclosure and one opening within 12 inches
(305 mm) of the bottom. These openings must communi-
cate directly or by ducts with the outdoors or spaces (crawl
or attic) that freely communicate with the outdoors or indi-
rectly through vertical ducts. Each opening shall have a
OUTLET AIR
SIDE WALL
TERMINATED
EXHAUST PIPE
(ALTERNATE
LOCATION)
INLET AIR
2
minimum free area of 1 square inch (645 mm ) per 4,000
NOTE−Each air duct opening shall have a free area of at least one
2
Btu (1.17 kW) per hour of total input rating of all equipment
ing with the outdoors through horizontal ducts, each open-
ing shall have a minimum free area of 1 square inch (645
square inch per 2,000 Btu (645mm per .59kW) per hour of the total
input rating of all equipment in the enclosure. If the equipment room
is located against an outside wall and the air openings communi-
cate directly with the outdoors, each opening shall have a free area
2
of at least 1 square inch per 4,000 Btu (645mm per 1.17kW) per
hour of the total input rating of all other equipment in the enclosure.
2
mm ) per 2,000 Btu (.56 kW) per total input rating of all
FIGURE 7
When ducts are used, they shall be of the same cross−sec-
tional area as the free area of the openings to which they
connect. The minimum dimension of rectangular air ducts
shall be no less than 3 inches (75 mm). In calculating free
area, the blocking effect of louvers, grilles, or screens
must be considered. If the design and free area of protec-
tive covering is not known for calculating the size opening
required, it may be assumed that wood louvers will have
20 to 25 percent free area and metal louvers and grilles
will have 60 to 75 percent free area. Louvers and grilles
must be fixed in the open position or interlocked with the
equipment so that they are opened automatically during
equipment operation.
Shipping Bolt Removal
NOTE − The ML193DF09048C is equipped with a 1/2 hp
blower motor which has three flexible legs and one rigid
leg. The rigid leg is equipped with a shipping bolt and a flat
white plastic washer (rather than the rubber mounting
grommet used with a flexible mounting leg). See figure 8.
The bolt and washer must be removed before the fur-
nace is placed into operation. After the bolt and washer
have been removed, the rigid leg will not touch the blower
housing.
Page 8
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Allow for clearances to combustible materials as indicated
on the unit nameplate. Minimum clearances for closet or al-
ML193DF09048C BLOWER MOTOR
RIGID LEG
remove shipping bolt and washer
WARNING
Blower access panel must be securely in place when
blower and burners are operating. Gas fumes, which
could contain carbon monoxide, can be drawn into
living space resulting in personal injury or death.
FIGURE 8
Installation − Setting Equipment
WARNING
SETTING EQUIPMENT
Do not install the furnace on its front, back or in the
return air ducts to the back of the furnace. Doing so
will adversely affect the operation of the safety con-
trol devices, which could result in personal injury or
death.
AIR FLOW
AIR FLOW
AIR FLOW
Select a location that allows for the required clearances
that are listed on the unit nameplate. Also consider gas
supply connections, electrical supply, vent connection,
condensate trap and drain connections, and installation
and service clearances [24 inches (610 mm) at unit
front]. The unit must be level from side to side. Unit may
be positioned from level to 1/2" toward the front to aid in
draining. See figure 9.
1/2"
max.
FRONT VIEW
SIDE VIEW
SIDE VIEW
Unit must be level side−to−side. Unit may be positioned
from level to 1/2" toward the front to aid in draining.
FIGURE 9
Front
Horizontal
Back
NOTE − Do not install the furnace on its front, back or in the horizontal position
FIGURE 10
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WARNING
1 − Cut floor opening keeping in mind clearances listed on
unit rating plate. Also keep in mind gas supply connec-
tions, electrical supply, flue and air intake connections
and sufficient installation and servicing clearances.
See table 1 for correct floor opening size.
2 − Flange warm air plenum and lower the plenum into the
opening.
Improper installation of the furnace can result in per-
sonal injury or death. Combustion and flue products
must never be allowed to enter the return air system
or air in the living space. Use sheet metal screws and
joint tape to seal return air system to furnace.
In platform installations with furnace return, the fur-
nace should be sealed airtight to the return air ple-
num. A door must never be used as a portion of the
return air duct system. The base must provide a
stable support and an airtight seal to the furnace. Al-
low absolutely no sagging, cracks, gaps, etc.
3 − Set the unit over the plenum and seal the plenum to
the unit.
4 − Ensure that the seal is adequate.
For no reason should return and supply air duct sys-
tems ever be connected to or from other heating de-
vices such as a fireplace or stove, etc. Fire, explo-
sion, carbon monoxide poisoning, personal injury
and/or property damage could result.
NON−COMBUSTIBLE FLOOR OPENING SIZE
Front to Rear
Side to Side
Cabinet Width
in.
mm
502
502
in.
mm
422
511
The unit may be installed three ways in downflow applica-
tions: on non−combustible flooring, on combustible flooring
using an additive base, or on a reverse−flow cooling coil
cabinet. Do not drag the unit across the floor in the
downflow position. Floor and furnace flange damage
will result.
B Cabinet (17.5")
C Cabinet (21")
19 − 3/4
19 − 3/4
16 − 5/8
20−1/8
NOTE − Floor opening dimensions listed are 1/4 inch (6 mm) larger than
the unit opening. See dimension drawing on page 2.
tions.
Downflow Application Installation Clearances
Top
FURNACE
PROPERLY
SIZED FLOOR
OPENING
SUPPLY AIR
PLENUM
Left Side
Right Side
Bottom
FIGURE 12
Top
*Front
Back
Sides
Vent
0
0
Installation on Combustible Flooring Figure 13
0
1 − When unit is installed on a combustible floor, a down-
flow combustible flooring base must be installed be-
tween the furnace and the floor. The base must be or-
dered separately. See table 2 for opening size to cut in
floor.
0†
0
Floor
NC‡
*Front clearance in alcove installation must be 24 in. (610 mm).
Maintain a minimum of 24 in. (610 mm) for front service access.
†Allow proper clearances to accommodate condensate trap and
vent pipe installation.
‡The furnace may be installed on a combustible wood floor if an op-
tional additive base is installed between the furnace and the com-
bustible floor.
CAUTION
The furnace and combustible flooring base shall not
be installed directly on carpeting, tile, or other com-
bustible material other than wood flooring.
FIGURE 11
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COMBUSTIBLE FLOORING BASE OPENING SIZE
Front to Rear
Side to Side
Cabinet
Width
Catalog
Number
FURNACE
in.
22
mm
559
in.
mm
476
B Cabinet
(17.5")
11M60
11M61
18 − 3/4
C Cabinet
(21")
COOLING COIL
PLENUM
22
559
22 − 3/4
578
PROPERLY
SIZED FLOOR
OPENING
FURNACE
SUPPLY AIR
PLENUM
PROPERLY
SIZED FLOOR
OPENING
COMBUSTIBLE
FLOORING BASE
FIGURE 14
Return Air Opening −− Downflow Units
Return air may be brought in only through the top opening
of a furnace installed in the downflow position. The follow-
ing steps should be taken when installing plenum:
1 − Bottom edge of plenum should be flanged with a
FIGURE 13
2 − Sealing strips should be used to ensure an airtight seal
between the cabinet and the plenum.
2 − After opening is cut, set the combustible flooring base
into opening.
3 − In all cases, plenum should be secured to top of fur-
nace using sheet metal screws.
3 − Check fiberglass strips on the combustible flooring
base to make sure they are properly glued and posi-
tioned.
4 − Make certain that an adequate seal is made.
PLENUM
SECURE FROM
4 − Lower supply air plenum into the combustible flooring
base until plenum flanges seal against fiberglass
strips.
(Field Provided)
OUTSIDE CABINET
NOTE − Be careful not to damage fiberglass strips.
CABINET
Check for a tight seal.
SEALING STRIP
SIDE PANEL
(Field Provided)
5 − Set the furnace over the plenum.
Side View
6 − Ensure that the seal between the furnace and plenum
is adequate.
FIGURE 15
PLENUM
NOTE − Downflow combustible flooring kit is not used..
(Field Provided)
SEALING STRIP
1 − Refer to reverse−flow coil installation instructions for
correctly sized opening in floor and installation of cabi-
net.
(Field Provided)
CABINET
2 − When cooling cabinet is in place, set and secure the
furnace according to the instructions that are provided
with the cooling coil. Secure the furnace to the cabinet.
SIDE PANEL
SECURE FROM
INSIDE CABINET
Side View
FIGURE 16
3 − Seal the cabinet and check for air leaks.
Page 11
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Filters
Pipe & Fittings Specifications
All pipe, fittings, primer and solvent cement must conform
with American National Standard Institute and the Ameri-
can Society for Testing and Materials (ANSI/ASTM) stan-
dards. The solvent shall be free flowing and contain no
lumps, undissolved particles or any foreign matter that ad-
versely affects the joint strength or chemical resistance of
the cement. The cement shall show no gelation, stratifica-
tion, or separation that cannot be removed by stirring. Re-
terials.
This unit is not equipped with a filter or rack. A field−pro-
vided filter is required for the unit to operate properly. Table
3 lists recommended filter size.
A filter must be in place whenever the unit is operating.
TABLE 3
Furnace
Cabinet Width
Filter Size
17−1/2"
21"
16 x 25 x 1 (1)
CAUTION
Duct System
Solvent cements for plastic pipe are flammable liq-
uids and should be kept away from all sources of
ignition. Do not use excessive amounts of solvent
cement when making joints. Good ventilation should
be maintained to reduce fire hazard and to minimize
breathing of solvent vapors. Avoid contact of cement
with skin and eyes.
Use industry-approved standards to size and install the
supply and return air duct system. Refer to ACCA Manual
D. This will result in a quiet and low-static system that has
uniform air distribution.
NOTE − This furnace is not certified for operation in heating
mode (indoor blower operating at selected heating speed)
with an external static pressure which exceeds 0.5 inches
w.c. Operation at these conditions may result in improper
limit operation.
TABLE 4
PIPING AND FITTINGS SPECIFICATIONS
Schedule 40 PVC (Pipe)
D1785
F891
Schedule 40 PVC (Cellular Core Pipe)
Schedule 40 PVC (Fittings)
Supply Air Plenum
D2466
F441
If the furnace is installed without a cooling coil, a removable
access panel should be installed in the supply air duct. The
access panel should be large enough to permit inspection
of the heat exchanger. The furnace access panel must al-
ways be in place when the furnace is operating and it must
not allow leaks into the supply air duct system.
Schedule 40 CPVC (Pipe)
Schedule 40 CPVC (Fittings)
SDR−21 PVC or SDR−26 PVC (Pipe)
SDR−21 CPVC or SDR−26 CPVC (Pipe)
Schedule 40 ABS Cellular Core DWV (Pipe)
Schedule 40 ABS (Pipe)
F438
D2241
F442
F628
D1527
D2468
Schedule 40 ABS (Fittings)
Return Air Plenum
ABS−DWV (Drain Waste & Vent)
(Pipe & Fittings)
D2661
D2665
NOTE − Return air must not be drawn from a room
where this furnace, or any other gas−fueled appliance
(i.e., water heater), or carbon monoxide−producing de-
vice (i.e., wood fireplace) is installed.
PVC−DWV (Drain Waste & Vent)
Pipe & Fittings)
ASTM
SPECIFICATION
PRIMER & SOLVENT CEMENT
PVC & CPVC Primer
PVC Solvent Cement
CPVC Solvent Cement
ABS Solvent Cement
F656
D2564
F493
When return air is drawn from a room, a negative pres-
sure is created in the room. If a gas appliance is operating
in a room with negative pressure, the flue products can
be pulled back down the vent pipe and into the room. This
reverse flow of the flue gas may result in incomplete com-
bustion and the formation of carbon monoxide gas. This
raw gas or toxic fumes might then be distributed through-
out the house by the furnace duct system.
D2235
PVC/CPVC/ABS All Purpose Cement For
Fittings & Pipe of the same material
D2564, D2235, F493
D3138
ABS to PVC or CPVC Transition Solvent
Cement
CANADA PIPE & FITTING & SOLVENT
CEMENT
MARKING
Use fiberglass sealing strips, caulking, or equivalent seal-
ing method between the plenum and the furnace cabinet to
ensure a tight seal. If a filter is installed, size the return air
duct to fit the filter frame.
PVC & CPVC Pipe and Fittings
PVC & CPVC Solvent Cement
ULCS636
ABS to PVC or CPVC Transition Cement
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Low temperature solvent cement is recommended during
cooler weather. Metal or plastic strapping may be used for
vent pipe hangers. Uniformly apply a liberal coat of PVC
primer for PVC or use a clean dry cloth for ABS to clean in-
side socket surface of fitting and male end of pipe to depth
of fitting socket.
IMPORTANT
ML193DF exhaust and intake connections are made
of PVC. Use PVC primer and solvent cement when
using PVC vent pipe. When using ABS vent pipe, use
transitional solvent cement to make connections to
the PVC fittings in the unit.
Canadian Applications Only − Pipe, fittings, primer
and solvent cement used to vent (exhaust) this ap-
pliance must be certified to ULC S636 and supplied by a
single manufacturer as part of an approved vent (ex-
haust) system. In addition, the first three feet of vent
pipe from the furnace flue collar must be accessible for
inspection.
Use PVC primer and solvent cement or ABS solvent cement
nate, use all purpose cement, to bond ABS, PVC, or CPVC
pipe when using fittings and pipe made of the same materi-
als. Use transition solvent cement when bonding ABS to ei-
ther PVC or CPVC.
TABLE 5
OUTDOOR TERMINATION KITS USAGE
STANDARD
CONCENTRIC
Outdoor
Exhaust
Accelerator
(Dia. X
Outdoor
Flush-
Mount
Kit
1−1/2"
Concentric Concentric Concentric
2"
3"
Exhaust
Accelerator
(Dia. X
2" Wall Plate 3" Wall Plate
Kit
2" Wall
Ring Kit
VENT
PIPE
DIA.
Kit
ML193
UNIT
Kit
Kit
Kit
Length)
Length)
(in.)
71M80 69M29
or or
†44W92†† †44W92††
22G44
or 30G28†
44J40
or 81J20†
60L46
or 44W93†
1−1/2" X 12"
2" X 12"
15F74
51W11**
2
YES
YES
YES
YES
YES
YES
YES
YES
YES
YES
YES
YES
YES*
YES*
YES*
YES*
YES*
YES*
YES
YES
YES
YES
YES
YES
YES
YES
YES
YES
YES
YES
YES
YES
YES
YES
YES
YES
YES
YES
YES
YES
2−1/2
YES
YES
YES
YES
YES
YES
YES
YES
YES
045
070
3
2
2−1/2
3
2
YES
YES
YES
YES
YES
YES
YES
YES
2−1/2
3
YES
090
110
YES
3
YES
*Requires field−provided and installed 1−1/2" exhaust accelerator.
** Kit 51W11 is provided with a 1−1/2" accelerator which must be used for all ML193DF−045, −070 and −090 installations.
† Termination kits 44W92, 44W93, 30G28 and 81J20 approved for use in Canadian installations to meet CSAB149.
†† The 44W92 Concentric kit is provided with a 1−1/2" accelerator which must be installed on the exhaust outlet when this kit is used with the ML193DF045P36B and
ML193DF070P36B furnaces.
Page 13
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Venting Practices
Joint Cementing Procedure
All cementing of joints should be done according to the
specifications outlined in ASTM D 2855.
Piping Suspension Guidelines
SCHEDULE 40
PVC − 5’
all other pipe* − 3’
NOTE − A sheet metal screw may be used to secure
the intake pipe to the connector, if desired. Use a drill
or self tapping screw to make a pilot hole.
DANGER
DANGER OF EXPLOSION!
* See table 4 for allowable pipe.
NOTE − Isolate piping at the point where it exits the outside wall or
roof in order to prevent transmission of vibration to the structure.
Fumes from PVC glue may ignite during system
check. Allow fumes to dissipate for at least 5 minutes
before placing unit into operation.
Wall Thickness Guidelines
24" maximum
3/4" minimum
1 − Measure and cut vent pipe to desired length.
Wall
inside
outside
2 − Debur and chamfer end of pipe, removing any ridges
or rough edges. If end is not chamfered, edge of pipe
may remove cement from fitting socket and result in a
leaking joint.
3 − Clean and dry surfaces to be joined.
4 − Test fit joint and mark depth of fitting on outside of pipe.
5 − Uniformly apply a liberal coat of PVC primer for PVC or
use a clean dry cloth for ABS to clean inside socket
surface of fitting and male end of pipe to depth of fitting
socket.
FIGURE 17
REPLACING FURNACE THAT
WAS PART OF A COMMON
VENT SYSTEM
CHIMNEY
OR GAS
VENT
(Check sizing
for water
heater only)
6 − Promptly apply solvent cement to end of pipe and in-
side socket surface of fitting. Cement should be ap-
plied lightly but uniformly to inside of socket. Take
care to keep excess cement out of socket. Apply sec-
ond coat to end of pipe.
FURNACE
(Replaced
by ML193)
WATER
HEATER
NOTE − Time is critical at this stage. Do not allow prim-
er to dry before applying cement.
7 − Immediately after applying last coat of cement to pipe,
and while both inside socket surface and end of pipe
are wet with cement, forcefully insert end of pipe into
socket until it bottoms out. Turn PVC pipe 1/4 turn dur-
ing assembly (but not after pipe is fully inserted) to dis-
tribute cement evenly. DO NOT turn ABS or cellular
core pipe.
OPENINGS
(To Adjacent
Room)
If an ML193DF furnace replaces a furnace which was com-
monly vented with another gas appliance, the size of the ex-
isting vent pipe for that gas appliance must be checked.
Without the heat of the original furnace flue products, the
existing vent pipe is probably oversized for the single water
heater or other appliance. The vent should be checked for
proper draw with the remaining appliance.
NOTE − Assembly should be completed within 20 sec-
onds after last application of cement. Hammer blows
should not be used when inserting pipe.
8 − After assembly, wipe excess cement from pipe at end
of fitting socket. A properly made joint will show a
bead around its entire perimeter. Any gaps may indi-
cate an improper assembly due to insufficient sol-
vent.
FIGURE 18
1 − In areas where piping penetrates joists or interior
walls, hole must be large enough to allow clearance on
all sides of pipe through center of hole using a hanger.
9 − Handle joints carefully until completely set.
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2 − When furnace is installed in a residence where unit is
shut down for an extended period of time, such as a
vacation home, make provisions for draining conden-
sate collection trap and lines.
Use the following steps to correctly size vent pipe diameter.
045, 070,
090, 110
or 135 btuh
1
Route piping to outside of structure. Continue with installa-
tion following instructions given in piping termination sec-
tion.
Furnace capacity?
Which termination?
Standard or
Concentric?
See table 5
CAUTION
2
Do not discharge exhaust into an existing stack or
stack that also serves another gas appliance. If verti-
cal discharge through an existing unused stack is re-
quired, insert PVC pipe inside the stack until the end
is even with the top or outlet end of the metal stack.
Which needs
most elbows?
Intake or
exhaust
3
CAUTION
The exhaust vent pipe operates under positive pres-
sure and must be completely sealed to prevent leak-
age of combustion products into the living space.
Vent Piping Guidelines
How many?
4
5
The ML193DF can be installed as either a Non−Direct
Vent or a Direct Vent gas central furnace.
NOTE − In Non-Direct Vent installations, combustion air is
taken from indoors and flue gases are discharged outdoors.
In Direct Vent installations, combustion air is taken from out-
doors and flue gases are discharged outdoors.
2", 2−1/2"
or 3"
Desired pipe size?
Intake and exhaust pipe sizing −− Size pipe according to
mitted.
TABLE 6
MINIMUM VENT PIPE LENGTHS
6
7
What is the altitude?
ML193DF
MODEL
MIN. VENT LENGTH*
15 ft. or
5 ft plus 2 elbows or
10 ft plus 1 elbow
045, 070, 090, 110
Use table 7 to find
max intake or exhaust
pipe length.
*Any approved termination may be added to the minimum length listed.
Regardless of the diameter of pipe used, the standard roof
and wall terminations described in section Exhaust Piping
Terminations should be used. Exhaust vent termination
pipe is sized to optimize the velocity of the exhaust gas as
FIGURE 19
NOTE − It is acceptable to use any pipe size which fits within
In some applications which permit the use of several differ-
ent sizes of vent pipe, a combination vent pipe may be
used. Contact Lennox’ Application Department for assis-
tance in sizing vent pipe in these applications.
NOTE − All horizontal runs of exhaust pipe must slope back
toward unit. A minimum of 1/4" (6mm) drop for each 12"
(305mm) of horizontal run is mandatory for drainage.
NOTE − Exhaust pipe MUST be glued to furnace exhaust
IMPORTANT
Do not use screens or perforated metal in exhaust or
intake terminations. Doing so will cause freeze−ups
and may block the terminations.
fittings.
NOTE − Exhaust piping should be checked carefully to
make sure there are no sags or low spots.
Page 15
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TABLE 7
Maximum Allowable Intake or Exhaust Vent Length in Feet
*Size intake and exhaust pipe length separately. Values in table are for Intake OR Exhaust, not combined total. Both Intake and Exhaust must be same pipe size.
Standard Termination at Elevation 0 − 10,000 ft.
2" Pipe
Model
2−1/2" Pipe
Model
3" Pipe
Model
Number
Of 90°
Elbows
Used
045
61
56
51
46
41
36
31
26
21
16
070
46
41
36
31
26
21
16
11
090
24
110
045
100
95
90
85
80
75
70
65
60
55
070
090
43
38
33
28
23
18
13
110
045
127
122
117
112
107
102
97
070
127
122
117
112
107
102
97
090
108
103
98
110
108
103
98
1
2
80
75
70
65
60
55
50
45
40
35
19
3
14
4
93
93
5
88
88
n/a
n/a
6
83
83
7
78
78
n/a
8
92
92
73
73
9
87
87
68
68
n/a
n/a
10
82
82
63
63
Concentric Termination Elevation 0 − 10,000 ft.
2" Pipe
Model
2−1/2" Pipe
Model
3" Pipe
Model
Number
Of 90°
Elbows
Used
045
53
48
43
38
33
28
23
18
13
n/a
070
38
33
28
23
18
13
090
22
110
045
90
85
80
75
70
65
60
55
50
45
070
70
65
60
55
50
45
40
35
30
25
090
39
34
29
24
19
14
110
045
111
106
101
96
070
111
106
101
96
090
104
99
94
89
84
79
74
69
64
59
110
104
99
94
89
84
79
74
69
64
59
1
2
17
3
12
4
5
91
91
n/a
n/a
6
86
86
7
81
81
n/a
8
76
76
n/a
n/a
9
71
71
10
66
66
Page 16
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TYPICAL EXHAUST PIPE CONNECTIONS
Pipe size determined in table 7.
2”
2”
2”
2”
2”
or
3”
TRANSITION
*2”
INTAKE
EXHAUST
DO NOT transition from smaller
to larger pipe size in horizontal
runs of exhaust pipe.
TOP VIEW
* When transitioning up in pipe size, use the shortest length of 2” PVC pipe possible.
NOTE − Exhaust pipe and intake pipe must be the same diameter.
FIGURE 20
TYPICAL INTAKE PIPE CONNECTIONS
2”
2”
Pipe size determined in table 7.
2”
2”
2”
or
TRANSITION
3”
3”
*2”
*2”
TRANSITION
*2”
INTAKE
EXHAUST
TOP VIEW
* When transitioning up in pipe size, use the shortest length of 2” PVC pipe possible.
NOTE − Intake pipe and exhaust pipe must be the same diameter.
FIGURE 21
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Intake Piping
General Guidelines for Vent Terminations
In Non-Direct Vent applications, combustion air is taken
from indoors and the flue gases are discharged to the out-
doors. The ML193DF is then classified as a non-direct
vent, Category IV gas furnace.
The ML193DF furnace may be installed in either direct
vent or non−direct vent applications. In non−direct vent
applications, when intake air will be drawn into the furnace
from the surrounding space, the indoor air quality must be
considered. Guidelines listed in Combustion, Dilution and
Ventilation Air section must be followed.
In Direct Vent applications, combustion air is taken from
outdoors and the flue gases are discharged to the out-
doors. The ML193DF is then classified as a direct vent,
Category IV gas furnace.
Follow the next two steps when installing the unit in Direct
Vent applications, where combustion air is taken from
outdoors and flue gases are discharged outdoors. The
provided air intake screen must not be used in direct
vent applications (outdoors).
In both Non-Direct Vent and Direct Vent applications, the
vent termination is limited by local building codes. In the
absence of local codes, refer to the current National Fuel
Gas Code ANSI Z223−1/NFPA 54 in U.S.A., and current
CSA−B149 Natural Gas and Propane Installation Codes in
Canada for details.
1 − Use cement to secure the intake pipe to the inlet air
connector.
Position termination according to location given in figure 23
obstructions and 12" above the average snow accumula-
tion.
2 − Route piping to outside of structure. Continue with
installation following instructions given in general
guide lines for piping terminations and intake and ex-
haust piping terminations for direct vent sections. Re-
At vent termination, care must be taken to maintain
protective coatings over building materials (prolonged
exposure to exhaust condensate can destroy protective
coatings). It is recommended that the exhaust outlet not be
located within 6 feet (1.8m) of a condensing unit because
the condensate can damage the painted coating.
TYPICAL AIR INTAKE PIPE CONNECTIONS
NON−DIRECT VENT APPLICATIONS
AIR
NOTE − If winter design temperature is below 32°F (0°C),
exhaust piping should be insulated with 1/2" (13mm), Ar-
maflex or equivalent when run through unheated space.
Do not leave any surface area of exhaust pipe open to out-
side air; exterior exhaust pipe should be insulated with
1/2" (13mm) Armaflex or equivalent. In extreme cold cli-
mate areas, 3/4" (19mm) Armaflex or equivalent may be
necessary. Insulation on outside runs of exhaust pipe
must be painted or wrapped to protect insulation from de-
terioration. Exhaust pipe insulation may not be necessary
in some specific applications.
INTAKE
SCREEN
(Provided)
NOTE − During extremely cold temperatures, below
approximately 20°F (6.7°C), units with long runs of vent
pipe through unconditioned space, even when insulated,
may form ice in the exhaust termination that prevents the
unit from operating properly. Longer run times of at least 5
minutes will alleviate most icing problems. Also, a heating
cable may be installed on exhaust piping and termination
to prevent freeze−ups. Heating cable installation kit is
available from Lennox. See Condensate Piping section
for part numbers.
NOTE − Air intake screen and elbow may be rotated, so that
screen may be positioned to face forward or to either side.
FIGURE 22
IMPORTANT
Do not use screens or perforated metal in exhaust
terminations. Doing so will cause freeze−ups and
may block the terminations.
Follow the next two steps when installing the unit in Non-
Direct Vent applications where combustion air is taken
from indoors and flue gases are discharged outdoors.
1 − Use field−provided materials and the factory−provided
air intake screen to route the intake piping as shown in
figure 22. Maintain a minimum clearance of 3" (76mm)
around the air intake opening. The air intake opening
(with the protective screen) should always be directed
forward, or sideways.
IMPORTANT
For Canadian Installations Only:
In accordance to CSA International B149 installation
codes, the minimum allowed distance between the
combustion air intake inlet and the exhaust outlet of
other appliances shall not be less than 12 inches
(305mm).
2 − Use cement to secure the intake pipe to the connector,
if desired.
Page 18
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VENT TERMINATION CLEARANCES
FOR NON−DIRECT VENT INSTALLATIONS IN THE USA AND CANADA
INSIDE CORNER
DETAIL
G
H
A
D
E
B
L
B
Fixed
Closed
B
B
I
C
Operable
Fixed
Closed
M
F
Operable
K
J
A
B
AREA WHERE TERMINAL
IS NOT PERMITTED
AIR SUPPLY INLET
VENT TERMINAL
1
2
US Installations
Canadian Installations
A =
Clearance above grade, veranda,
porch, deck or balcony
12 inches (305mm) or 12 in. 305mm)
above average snow accumulation.
12 inches (305mm) or 12 in. 305mm)
above average snow accumulation.
B =
Clearance to window or
door that may be opened
6 inches (152mm) for appliances <10,000
Btuh (3kw), 12 inches (305mm) for
appliances > 10,000 Btuh (3kw) and
<100,000 Btuh (30kw), 36 inches (.9m)
for appliances > 100,000 Btuh (30kw)
4 feet (1.2 m) below or to side of opening;
1 foot (30 cm) above opening
C =
D =
Clearance to permanently
closed window
* 12"
* 12"
Vertical clearance to ventilated soffit
located above the terminal within a
horizontal distance of 2 feet (mm)
from the center line of the terminal
* Equal to or greater than soffit depth.
* Equal to or greater than soffit depth.
* Equal to or greater than soffit depth.
E =
F =
Clearance to unventilated soffit
Clearance to outside corner
* Equal to or greater than soffit depth.
* No minimum to outside corner
* No minimum to outside corner
*
G = Clearance to inside corner
*
H = Clearance to each side of center line ex-
tended above meter / regulator assembly
3 feet (.9m) within a height 15 feet (4.5m) 3 feet (.9m) within a height 15 feet (4.5m)
above the meter / regulator assembly
*
above the meter / regulator assembly
I =
Clearance to service regulator
vent outlet
3 feet (.9m)
* 3 feet (.9m)
J =
Clearance to non−mechanical air
supply inlet to building or the com-
bustion air inlet to any other ap-
pliance
6 inches (152mm) for appliances <10,000
Btuh (3kw), 12 inches (305mm) for
appliances > 10,000 Btuh (3kw) and
<100,000 Btuh (30kw), 36 inches (.9m)
for appliances > 100,000 Btuh (30kw)
4 feet (1.2 m) below or to side of opening;
1 foot (30 cm) above opening
K =
L =
Clearance to mechanical air sup-
ply inlet
3 feet (.9m) above if within 10 feet
(3m) horizontally
6 feet (1.8m)
Clearance above paved sidewalk or
paved driveway located on public property
7 feet (2.1m)ꢀ
7 feet (2.1m)ꢀ
M =
Clearance under veranda, porch,
deck or balcony
12 inches (305mm)ꢁ
*12 inches (305mm)ꢁ
1
In accordance with the current ANSI Z223.1/NFPA 54 Natural Fuel Gas Code
*For clearances not specified in ANSI Z223.1/NFPA 54 or CSA B149.1,
clearance will be in accordance with local installation codes and the re-
quirements of the gas supplier and these installation instructions."
2
In accordance with the current CSA B149.1, Natural Gas and Propane Installation Code
ꢀ A vent shall not terminate directly above a sidewalk or paved driveway that is located
between two single family dwellings and serves both dwellings.
ꢁ Permitted only if veranda, porch, deck or balcony is fully open on a minimum of two
sides beneath the floor. Lennox recommends avoiding this location if possible.
FIGURE 23
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VENT TERMINATION CLEARANCES
FOR DIRECT VENT INSTALLATIONS IN THE USA AND CANADA
INSIDE CORNER
DETAIL
G
H
A
D
E
B
L
B
Fixed
Closed
B
B
I
C
Operable
Fixed
Closed
M
F
Operable
K
J
A
B
AREA WHERE TERMINAL
IS NOT PERMITTED
AIR SUPPLY INLET
VENT TERMINAL
1
2
US Installations
Canadian Installations
A =
Clearance above grade, veranda,
porch, deck or balcony
12 inches (305mm) or 12 in. 305mm)
above average snow accumulation.
12 inches (305mm) or 12 in. 305mm)
above average snow accumulation.
B =
Clearance to window or
door that may be opened
6 inches (152mm) for appliances <10,000 6 inches (152mm) for appliances <10,000
Btuh (3kw), 9 inches (mm) for appliances
> 10,000 Btuh (3kw) and <50,000 Btuh
(15 kw), 12 inches (305mm) for ap-
pliances > 50,000 Btuh (15kw)
Btuh (3kw), 12 inches (305mm) for
appliances > 10,000 Btuh (3kw) and
<100,000 Btuh (30kw), 36 inches (.9m)
for appliances > 100,000 Btuh (30kw)
* 12"
C =
D =
Clearance to permanently
closed window
* 12"
Vertical clearance to ventilated soffit
located above the terminal within a
horizontal distance of 2 feet (mm)
from the center line of the terminal
* Equal to or greater than soffit depth
* Equal to or greater than soffit depth
* Equal to or greater than soffit depth
* No minimum to outside corner
* Equal to or greater than soffit depth
* No minimum to outside corner
E =
F =
G =
Clearance to unventilated soffit
Clearance to outside corner
Clearance to inside corner
*
*
H = Clearance to each side of center line ex-
tended above meter / regulator assembly
3 feet (.9m) within a height 15 feet (4.5m) 3 feet (.9m) within a height 15 feet (4.5m)
above the meter / regulator assembly
above the meter / regulator assembly
I =
Clearance to service regulator
vent outlet
3 feet (.9m)
* 3 feet (.9m)
J =
Clearance to non−mechanical air
supply inlet to building or the com-
bustion air inlet to any other ap-
pliance
6 inches (152mm) for appliances <10,000 6 inches (152mm) for appliances <10,000
Btuh (3kw), 9 inches (mm) for appliances
> 10,000 Btuh (3kw) and <50,000 Btuh
(15 kw), 12 inches (305mm) for ap-
pliances > 50,000 Btuh (15kw)
Btuh (3kw), 12 inches (305mm) for
appliances > 10,000 Btuh (3kw) and
<100,000 Btuh (30kw), 36 inches (.9m)
for appliances > 100,000 Btuh (30kw)
K =
L =
Clearance to mechanical air sup-
ply inlet
3 feet (.9m) above if within 10 feet
(3m) horizontally
6 feet (1.8m)
Clearance above paved sidewalk or
paved driveway located on public property
7 feet (2.1m)ꢀ
* 7 feet (2.1m)
M =
Clearance under veranda, porch,
deck or balcony
*12 inches (305mm)ꢁ
12 inches (305mm)ꢁ
1
In accordance with the current ANSI Z223.1/NFPA 54 Natural Fuel Gas Code
*For clearances not specified in ANSI Z223.1/NFPA 54 or CSA B149.1, clear-
ance will be in accordance with local installation codes and the requirements
of the gas supplier and these installation instructions."
2
In accordance with the current CSA B149.1, Natural Gas and Propane Installation Code
ꢀ A vent shall not terminate directly above a sidewalk or paved driveway that is located
between two single family dwellings and serves both dwellings.
ꢁ Permitted only if veranda, porch, deck or balcony is fully open on a minimum of two
sides beneath the floor. Lennox recommends avoiding this location if possible.
FIGURE 24
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Details of Intake and Exhaust Piping Terminations for
Direct Vent Installations
between the end of the exhaust pipe and the end of
the intake pipe without a termination elbow is 8" and a
minimum distance of 6" with a termination elbow. See
NOTE − In Direct Vent installations, combustion air is tak-
en from outdoors and flue gases are discharged to out-
doors.
3"(76mm) MAX.
SIZE TERMINATION
PIPE PER TABLE 8.
Inches(mm)
NOTE − Flue gas may be slightly acidic and may adversely
affect some building materials. If any vent termination is
used and the flue gasses may impinge on the building ma-
terial, a corrosion−resistant shield (minimum 24 inches
square) should be used to protect the wall surface. If the
optional tee is used, the protective shield is recommended.
The shield should be constructed using wood, plastic,
sheet metal or other suitable material. All seams, joints,
cracks, etc. in the affected area should be sealed using an
UNCONDITIONED
ATTIC SPACE
8" (203mm) MIN
1/2" (13mm) FOAM
INSULATION IN
UNCONDITIONED
SPACE
12" (305mm) ABOVE
AVERAGE SNOW
ACCUMULATION
3" (76mm) OR
2" (51mm) PVC
Intake and exhaust pipes may be routed either horizontally
through an outside wall or vertically through the roof. In attic
or closet installations, vertical termination through the roof
tions.
PROVIDE SUPPORT
FOR INTAKE AND
EXHAUST LINES
DIRECT VENT ROOF TERMINATION KIT
(15F75 or 44J41)
1 − Exhaust and intake exits must be in same pressure
zone. Do not exit one through the roof and one on the
side. Also, do not exit the intake on one side and the
exhaust on another side of the house or structure.
FIGURE 25
2 − Intake and exhaust pipes should be placed as close
together as possible at termination end (refer to il-
lustrations). Maximum separation is 3" (76mm) on roof
terminations and 6" (152mm) on side wall termina-
tions.
2" EXTENSION FOR
2" PVC PIPE
1" EXTENSION FOR
3" PVC PIPE
FURNACE
EXHAUST
PIPE
4’’
GLUE EXHAUST
END FLUSH INTO
TERMINATION
FURNACE
INTAKE
PIPE
3 − On roof terminations, the intake piping should termi-
nate straight down using two 90° elbows (See figure
25).
1−1/2" ACCELERATOR
(all −070 and −090 units)
4 − Exhaust piping must terminate straight out or up as
shown. A reducer may be required on the exhaust pip-
ing at the point where it exits the structure to improve
the velocity of exhaust away from the intake piping.
See table 8.
FLUSH−MOUNT SIDE WALL TERMINATION KIT 51W11
FIGURE 26
TABLE 8
EXHAUST PIPE TERMINATION SIZE REDUCTION
ML193
MODEL
Termination
Pipe Size
7 − If intake and exhaust piping must be run up a side wall
to position above snow accumulation or other ob-
structions, piping must be supported every 24"
close coupled wall termination kits must be extended
When exhaust and intake piping must be run up an
outside wall, the exhaust piping must be terminated
equipped with a 90° elbow turndown. Using turndown
will add 5 feet (1.5m) to the equivalent length of the
pipe.
Exhaust Pipe Size
1−1/2" (38mm)
2" (51mm), 2−1/2" (64mm),
3" (76mm)
*045 and *070
*090
2" (51mm)
2" (51mm)
3" (76mm)
110
*ML193DF−045, −070 and −090 units with the flush−mount termination
must use the 1−1/2"accelerator supplied with the kit.
5 − On field−supplied terminations for side wall exit, ex-
haust piping may extend a maximum of 12 inches
(305mm) for 2" PVC and 20 inches (508mm) for 3"
(76mm) PVC beyond the outside wall. Intake piping
NOTE − Care must be taken to avoid recirculation of
exhaust back into intake pipe.
8 − A multiple furnace installation may use a group of up to
four terminations assembled together horizontally, as
6 − On field supplied terminations, a minimum distance
Page 21
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B
B
D
D
C
3
Intake
C
1
Front View of
Intake and Exhaust
A
Exhaust
A
2
Intake
Exhaust
D
TABLE 9
2" (51mm)
Vent Pipe
1
E
3" (76mm)
Vent Pipe
B
A− Clearance above
grade or average snow
accumulation
12" (508MM) Min.
12" (508MM) Min.
12"
B−Horizontal
separation between
intake and exhaust
6" (152MM) Min. 6" (152MM) Min.
24" (610 MM) Max 24" (610 MM) Max
C
2
C−Minimum from
end of exhaust to
inlet of intake
A
9" (227MM) Min. 9" (227MM) Min.
12" (305MM) Min.
16" (405 MM) Max.
12" (305MM) Min.
20" (508MM) Max.
D−Exhaust pipe length
E−Wall support distance
from top of each pipe
(intake/exhaust)
6" (152MM) Max. 6" (152MM) Max.
1
The exhaust termination tee should be connected to the 2" or 3" PVC flue pipe as shown in the illustration. Do
not use an accelerator in applications that include an exhaust termination tee. The accelerator is not required.
As required. Flue gas may be acidic and may adversely affect some building materials. If a side wall vent
2
termination is used and flue gases will impinge on the building materials, a corrosion−resistant shield (24 inches
square) should be used to protect the wall surface. If optional tee is used, the protective shield is recom-
mended. The shield should be constructed using wood, sheet metal or other suitable material. All seams, joints,
cracks, etc. in affected area, should be sealed using an appropriate sealant.
3
Exhaust pipe 45° elbow can be rotated to the side away from the combustion air inlet to direct exhaust away
from adjacent property. The exhaust must never be directed toward the combustion air inlet.
FIGURE 27
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FIELD SUPPLIED WALL TERMINATION OR
(15F74) WALL RING TERMINATION KIT
With INTAKE ELBOW
FIELD SUPPLIED WALL TERMINATION OR
(15F74) WALL RING TERMINATION KIT
NOTE − FIELD PROVIDED
REDUCER MAY BE
NOTE − FIELD PROVIDED
REDUCER MAY BE
1/2" (13mm) ARMAFLEX
REQUIRED TO ADAPT
1/2" (13mm) ARMAFLEX
REQUIRED TO ADAPT
INSULATION IN UN-
INSULATION IN UN-
LARGER VENT PIPE SIZE
LARGER VENT PIPE SIZE
CONDITIONED SPACE
TO TERMINATION
CONDITIONED SPACE
TO TERMINATION
SIZE TERMINATION
PER TABLE 8
SIZE TERMINATION
PER TABLE 8
D
B
D
B
STRAIGHT
APPPLICATION
A
STRAIGHT
APPPLICATION
C
C
A
1/2" (13mm) ARMAFLEX INSULATION
IN UNCONDITIONED SPACE
1/2" (13mm) ARMAFLEX INSULATION
IN UNCONDITIONED SPACE
D
D
E
* WALL
SUPPORT
E
* WALL
SUPPORT
B
B
A
A
EXTENDED
C
APPLICATION
C
EXTENDED
APPLICATION
arrangement.
arrangement.
* Use wall support every 24" (610 mm). Use two wall supports if
extension is greater than 24" (610 mm) but less than 48" (1219 mm).
NOTE − One wall support must be 6" (152 mm) from top of each pipe
(intake and exhaust)
* Use wall support every 24" (610 mm). Use two wall supports if
extension is greater than 24" (610 mm) but less than 48" (1219 mm).
NOTE − One wall support must be 6" (152 mm) from top of each pipe
(intake and exhaust)
2" (51mm)
Vent Pipe
3" (76mm)
Vent Pipe
2" (51mm)
Vent Pipe
3" (76mm)
Vent Pipe
A−Minimum clearance
above grade or average
snow accumulation
A−Minimum clearance
above grade or average
snow accumulation
12" (508MM)
12" (508MM)
12" (508MM)
6" (152MM)
8" (203MM)
12" (508MM)
6" (152MM)
8" (203MM)
B−Maximum horizontal
separation between
intake and exhaust
B−Maximum horizontal
separation between
intake and exhaust
6" (152MM)
6" (152MM)
C−Minimum from
end of exhaust to
inlet of intake
C−Minimum from
end of exhaust to
inlet of intake
6" (152MM)
20" (508MM)
6" (152MM)
6" (152MM)
12" (305MM)
6" (152MM)
D−Maximum exhaust
pipe length
D−Maximum exhaust
pipe length
12" (305MM)
6" (152MM)
20" (508MM)
6" (152MM)
E−Maximum wall support
distance from top of each
pipe (intake/exhaust)
E−Maximum wall support
distance from top of each
pipe (intake/exhaust)
FIGURE 29
FIGURE 28
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1−1/2" (38mm) accelerator
provided on 71M80 & 44W92
kits for ML193DF045P36B− &
070P36B
EXHAUST VENT
Front View
SIZE
TERMINATION
PIPE PER
INTAKE
AIR
FLASHING
12” (305mm)
Minimum
Above Average
Snow
(Not Furnished)
INTAKE
Accumulation
Top View
1/2" (13mm) Foam Insulation
in Unconditioned Space
SHEET METAL STRAP
(Clamp and sheet metal strap
must be field installed to support
the weight of the termination kit.)
FIELD−PROVIDED
REDUCER MAY
BE REQUIRED TO
ADAPT LARGER
VENT PIPE SIZE
TO TERMINATION
EXHAUST VENT
INTAKE AIR
CLAMP
FIELD−PROVIDED
REDUCER MAY BE REQUIRED
TO ADAPT LARGER VENT
PIPE SIZE TO TERMINATION
6 (152mm) MIN.
OUTSIDE WALL
DIRECT VENT WALL TERMINATION KIT
(30G28 or 81J20)
DIRECT VENT CONCENTRIC ROOFTOP TERMINATION
71M80, 69M29 or 60L46 (US)
41W92 or 41W93 (Canada)
FIGURE 30
FIGURE 33
1−1/2" (38mm) accelerator
provided on 71M80 &
FIELD−PROVIDED
44W92 kits for
ML193DF045P36B− &
EXHAUST VENT
Front View
REDUCER MAY BE
REQUIRED TO ADAPT
SIZE
070P36B
LARGER VENT PIPE
SIZE TO TERMINATION
TERMINATION
PIPE PER
OUTSIDE
WALL
INTAKE
INTAKE
AIR
AIR
EXHAUST
AIR
EXHAUST
AIR
Top View
12" (305mm) Min.
above grade or
average snow ac-
cumulation.
INTAKE
AIR
1/2" (13mm) Foam Insulation
in Unconditioned Space
INTAKE
AIR
CLAMP
(Not Furnished)
FIELD−PROVIDED
REDUCER MAY
BE REQUIRED TO
ADAPT LARGER
VENT PIPE SIZE
TO TERMINATION
GRADE
EXHAUST VENT
INTAKE AIR
DIRECT VENT CONCENTRIC WALL TERMINATION
71M80, 69M29 or 60L46 (US)
41W92 or 41W93 (Canada)
FIGURE 31
8" (206mm) MIN.
OUTSIDE WALL
12"
DIRECT VENT WALL TERMINATION KIT
(22G44 or 44J40)
EXHAUST
VENT
(305mm)
5−1/2"
(140mm)
5"
(127mm)
FIGURE 34
INTAKE
AIR
18" MAX.
(457mm)
Front View
EXHAUST VENT
12" (305mm) Min.
above grade or
average snow ac-
cumulation.
Inches (mm)
INTAKE
AIR
Side View
optional intake elbow
OPTIONAL VENT TERMINATION FOR MULTIPLE UNIT
INSTALLATION OF DIRECT VENT WALL TERMINATION KIT
(22G44, 44J40, 30G28 or 81J20)
FIGURE 32
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WALL TERMINATION KITS (CLOSE−COUPLE)
EXTENDED VENT FOR GRADE CLEARANCE
2 inch (51 mm) 22G44 (US)
3 inch (76 mm) 44J40 (US)
If intake and exhause pipe is less than 12 in. (305 mm)
above snow accumulation or other obstructions, field−
FIELD−PROVIDED
REDUCER MAY BE REQUIRED TO ADAPT
LARGER VENT PIPE SIZE TO TERMINATION
fabricated piping must be installed.
8” (203 mm) Min. for 2” (51 mm) & 3” (76 mm) DIA. pipe
between the end of the exhaust pipe and intake pipe
12” (305 mm) Max. for 2” (51 mm) Dia. Exhaust
20” (508 mm) Max. for 3” (76 mm) Dia. Exhaust
WALL SUPPORT*
12”
(305 mm)
EXHAUST
AIR
1/2” (13 mm)
FOAM INSULATION
(Field Furnished)
6” (152 mm)
Maximum
INTAKE
AIR
EXHAUST
AIR
INTAKE
AIR
5” (127 mm)
12” (305 mm) Minimum
8” (203 mm) Min.
12” (305 mm) Minimum
Above Grade or Average
Snow Accumulation
Above Grade or Average
5−1/2”
Snow Accumulation
(140 mm)
GRADE
GRADE
*Use wall support every 24" (610). Use two supports if
extension is greater than 24" but less than 48".
12” (305 mm) Max. for 2” (51 mm) Dia. Exhaust
20” (508 mm) Max. for 3” (76 mm) Dia. Exhaust
FIGURE 35
WALL TERMINATION KITS (CLOSE−COUPLE)
EXTENDED VENT FOR GRADE CLEARANCE
2 inch (51 mm) 30G28 (WTK Canada)
3 inch (76 mm) 81J20 (WTK Canada)
See Installation Instructions for additional information.
If intake and exhause pipe is less than 12 in. (305 mm)
FIELD−PROVIDED
REDUCER MAY BE REQUIRED TO ADAPT
LARGER VENT PIPE SIZE TO TERMINATION
above snow accumulation or other obstructions, field−
fabricated piping must be installed.
WALL SUPPORT*
12” (305 mm) Max. for 2” (51 mm) Dia. Exhaust
20” (508 mm) Max. for 3” (76 mm) Dia. Exhaust
12”
(305 mm)
EXHAUST
AIR
1/2” (13 mm)
FOAM INSULATION
(Field Furnished)
6” (152 mm)
Maximum
INTAKE
AIR
6” (152 mm)
Minimum
EXHAUST
AIR
INTAKE
AIR
5” (127 mm)
12” (305 mm) Minimum
6” (152 mm)
Minimum
12” (305 mm) Minimum
Above Grade or Average
Snow Accumulation
GRADE
Above Grade or Average
5−1/2”
(140 mm)
Snow Accumulation
GRADE
*Use wall support every 24" (610). Use two supports if
extension is greater than 24" but less than 48".
12” (305 mm) Max. for 2” (51 mm) Dia. Exhaust
20” (508 mm) Max. for 3” (76 mm) Dia. Exhaust
FIGURE 36
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ML193DF DIRECT VENT APPLICATION
USING E
SIZE TERMINATION
PIPE PER TABLE 8.
STRAIGHT−CUT OR
ANGLE−CUT IN DIRECTION
OF ROOF SLOPE *
12" (305mm)
ABOVE AVE.
SNOW
1/2" (13mm) FOAM
INSULATION
3" − 8"
(76mm−
203mm)
EXHAUST VENT
1/2" (13mm)
WEATHERPROOF
INSULATION
8" − 12"
(203mm − 305mm)
ACCUMULATION
SHOULDER OF FITTINGS
PROVIDE SUPPORT
OF PIPE ON TOP PLATE
Minimum 12" (305MM)
INTAKE PIPE
INSULATION (optional)
3" (76mm) OR
2" (51mm) PVC
above chimney top
plate or average snow
accumulation
UNCONDITIONED
ATTIC SPACE
SHEET
METAL TOP
PLATE
ALTERNATE
INTAKE PIPE
PROVIDE SUPPORT
FOR EXHAUST LINES
3" − 8"
(76mm−
203mm)
INSULATE
TO FORM
SEAL
EXTERIOR
PORTION OF
CHIMNEY
NON−DIRECT VENT ROOF TERMINATION KIT
(15F75 or 44J41)
*SIZE TERMINATION
PIPE PER TABLE 8.
FIGURE 38
NOTE − Do not discharge exhaust gases directly into any chimney or vent stack. If ver-
tical discharge through an existing unused chimney or stack is required, insert piping
inside chimney until the pipe open end is above top of chimney and terminate as illus-
trated. In any exterior portion of chimney, the exhaust vent must be insulated.
12" (305mm) MAX. for 2" (51mm)
20" (508mm) MAX. for 3" (76mm)
1/2" (13mm) ARMAFLEX
INSULATION IN
UNCONDITIONED SPACE
FIGURE 37
1/2" (13mm)
ARMAFLEX
INSULATION
FIELD−PROVIDED
REDUCER MAY
BE REQUIRED TO
ADAPT LARGER
VENT PIPE SIZE
TO TERMINATION
Details of Exhaust Piping Terminations for Non-Direct
Vent Applications
PVC REDUCER
12" MIN.
(305mm)
Above Grade or
average snow
accumulation
Exhaust pipes may be routed either horizontally through an
outside wall or vertically through the roof. In attic or closet
installations, vertical termination through the roof is pre-
SIZE TERMINATION
PIPE PER TABLE 8.
NON−DIRECT VENT FIELD SUPPLIED WALL TERMINATION OR
(15F74) WALL TERMINATION KIT
1 − Exhaust piping must terminate straight out or up as
shown. The termination pipe must be sized as listed in
ity required to move the exhaust gases away from the
building.
FIGURE 39
3 − If exhaust piping must be run up a side wall to position
above snow accumulation or other obstructions, pip-
ing must be supported every 24 inches (610mm) as
shown in figure 40. When exhaust piping must be run
up an outside wall, any reduction in exhaust pipe size
must be done after the final elbow.
2 − On field supplied terminations for side wall exit, ex-
haust piping may extend a maximum of 12 inches
(305mm) for 2" PVC and 20 inches (508mm) for 3"
(76mm) PVC beyond the outside wall. See figure 39.
Page 26
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NOTE − If necessary the condensate trap may be installed
up to 5´ away from the furnace. Use PVC pipe to connect
trap to furnace condensate outlet. Piping from furnace
must slope down a minimum of 1/4" per ft. toward trap.
12" (305mm) MAX. for 2" (51mm)
20" (508mm) MAX. for 3" (76mm)
UNCONDITIONED
SPACE
6" (152mm)
Max
SIZE TER-
MINATION
PIPE PER
CONDENSATE TRAP AND PLUG LOCATIONS
*WALL SUPPORT
OUTSIDE WALL
FIELD−PROVIDED
REDUCER MAY BE
REQUIRED TO
ADAPT LARGER
VENT PIPE SIZE TO
TERMINATION
12" (305mm)
ABOVE GRADE OR
AVERAGE SNOW
ACCUMULATION
1/2" (13mm) FOAM
INSULATION IN
UNCONDITIONED
SPACE
Trap
(same on
right side)
1/2" (13mm) FOAM
INSULATION
*Use wall support every 24" (610). Use
two supports if extension is greater
than 24" but less than 48".
Plug
(same on left
side)
1−1/2 in.
NON−DIRECT VENT FIELD SUPPLIED WALL TERMINATION EX-
TENDED OR (15F74) WALL TERMINATION VENT PIPE EXTENDED
FIGURE 40
ML193DF NON−DIRECT VENT APPLICATION
USING EXISTING CHIMNEY
STRAIGHT−CUT OR
ANGLE−CUT IN DIRECTION
OF ROOF SLOPE
SIZE TERMINATION
PIPE PER TABLE 8.
3" − 8"
(76mm−
203mm)
EXHAUST VENT
1/2" (13mm)
WEATHERPROOF
INSULATION
Minimum 12" (305MM)
above chimney top
FIGURE 42
plate or average snow
accumulation
SHOULDER OF FITTINGS
PROVIDE SUPPORT
OF PIPE ON TOP PLATE
1 − Determine which side condensate piping will exit the
unit, location of trap, field−provided fittings and length of
PVC pipe required to reach available drain.
SHEET
METAL TOP
PLATE
at the appropriate location on the side of the unit. Install
field−provided 1/2" NPT male fitting into cold end head-
er box. Use teflon tape or appropriate pipe dope.
3" − 8"
(76mm−
203mm)
INSULATE
TO FORM
SEAL
EXTERIOR
PORTION OF
CHIMNEY
3 − Install the cap over the clean out opening at the base of
NOTE − Vinyl tubing may be used for condensate drain.
Tubing must be 1−1/4" OD X 1" ID and should be attached to
the drain on the trap using a hose clamp.
NOTE − Do not discharge exhaust gases directly into any chimney or vent stack. If ver-
tical discharge through an existing unused chimney or stack is required, insert piping
inside chimney until the pipe open end is above top of chimney and terminate as illus-
trated. In any exterior portion of chimney, the exhaust vent must be insulated.
4 − Install drain trap using appropriate PVC fittings, glue
all joints. Glue the provided drain trap as shown in fig-
FIGURE 41
Condensate Piping
This unit is designed for either right- or left-side exit of con-
tions.
NOTE − If necessary the condensate trap may be installed
up to 5 feet away from the furnace. Piping from furnace
must slope down a minimum of 1/4" per ft. toward trap.
Page 27
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5 − If unit will be started immediately upon completion of
installation, prime trap per procedure outlined in Unit
Start−Up section.
ML193DF with Evaporator Coil
Condensate line must slope downward away from the
trap to drain. If drain level is above condensate trap,
condensate pump must be used. Condensate drain
line should be routed within the conditioned space to
avoid freezing of condensate and blockage of drain
line. If this is not possible, a heat cable kit may be used
on the condensate trap and line. Heat cable kit is avail-
able from Lennox in various lengths; 6 ft. (1.8m) − kit
no. 26K68; 24 ft. (7.3m) − kit no. 26K69; and 50 ft.
(15.2m) − kit no. 26K70.
Condensate trap and
evaporator coil must drain
separately as shown.
Field−Provided Vent
CONDENSATE TRAP LOCATION
(shown with right side exit of condensation)
Drain
Field Provided Vent
min. 1" Above
Condensate Drain
FIGURE 44
Trap can be installed a
maximum of 5 ft. from furnace.
(*PVC Only)
CAUTION
Do not use copper tubing or existing copper
condensate lines for drain line.
1" min.
5’ max.
CAUTION
to drain
*Piping from furnace must slope down a minimum of
1/4" per ft. toward trap.
A separate drain line must be run to the drain
from the condensate trap to ensure proper
drainage and pressure switch operation. DO
NOT connect the condensate trap drain into the
drain line from the evaporator coil.
FIGURE 43
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TRAP / DRAIN ASSEMBLY USING 1/2" PVC OR 3/4" PVC
OPTIONAL Condensate Drain Connection
Adapter 1/2 inch slip X
Adapter 1/2 inch slip X
1/2 inch mpt (Not Furnished)
Condensate Drain
Connection In Unit
1/2 inch mpt (Not Furnished)
Vent
90° Street Elbow
1 (25) Minimum
1/2 inch PVC
5 Feet
Maximum
(Not Furnished)
Above Top of Condensate Drain
Connection In Unit
90° Elbow 1/2 inch PVC
Condensate Drain
Connection In Unit
(Not Furnished)
1/2 inch PVC Pipe
(Not Furnished)
1/2 inch PVC Pipe
(Not Furnished)
OPTIONAL Drain Piping
Drain Assembly for 1/2 inch Drain Pipe
Coupling 1/2 inch slip X slip
(Not Furnished)
1/2 inch PVC Pipe
(Not Furnished)
Drain Trap
Assembly
(Furnished)
1/2 inch PVC
(Furnished)
90° Elbow
1/2 inch PVC
(Not Furnished)
To
Drain
To
Drain
Drain Assembly for 3/4 inch Drain Pipe
Drain Trap
Clean Out
90° Elbow
90° Elbow
3/4 inch PVC
(Not Furnished)
3/4 inch PVC
(Not Furnished)
To
Drain
To
Drain
Coupling 3/4 inch slip X slip
(Not Furnished)
Drain Trap Assembly with 3/4 inch Piping
Drain Trap Assembly with 1/2 inch Piping
1 inch (25mm) Minimum Above Top of
Condensate Drain Connection In Unit
1 inch (25mm) Minimum Above Top of
Condensate Drain Connection In Unit
Vent
Drain Trap Assembly
(Furnished)
Vent
7
Condensate Drain
Connection In Unit
Condensate Drain
Connection In Unit
(178)
To
Drain
To
Drain
FIGURE 45
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Gas Piping
IMPORTANT
Compounds used on threaded joints of gas piping
must be resistant to the actions of liquified petro-
leum gases.
CAUTION
If a flexible gas connector is required or allowed by
the authority that has jurisdiction, black iron pipe
shall be installed at the gas valve and extend outside
the furnace cabinet. The flexible connector can then
be added between the black iron pipe and the gas
supply line.
Leak Check
After gas piping is completed, carefully check all piping
connections (factory− and field−installed) for gas leaks. Use
a leak detecting solution or other preferred means.
The furnace must be isolated from the gas supply system
by closing its individual manual shut-off valve during any
pressure testing of the gas supply system at pressures less
than or equal to 1/2 psig (3.48 kPa, 14 inches w.c.).
WARNING
Do not exceed 600 in−lbs (50 ft−lbs) torque when at-
taching the gas piping to the gas valve.
MANUAL MAIN SHUT−OFF
VALVE WILL NOT HOLD
NORMAL TEST PRESSURE
1 − Gas piping may be routed into the unit through either
the left- or right-hand side. Supply piping enters into
the gas valve from the side of the valve as shown in
FURNACE
ISOLATE
GAS VALVE
1/8" N.P.T. PLUGGED TAP
CAP
2 − When connecting gas supply, factors such as length of
run, number of fittings and furnace rating must be con-
lists recommended pipe sizes for typical applications.
FIGURE 46
NOTE − Use two wrenches when connecting gas pip-
ing to avoid transferring torque to the manifold.
3 − Gas piping must not run in or through air ducts, clothes
chutes, chimneys or gas vents, dumb waiters or eleva-
tor shafts. Center gas line through piping hole. Gas
IMPORTANT
When testing pressure of gas lines, gas valve must
valves can be damaged if subjected to pressures
greater than 1/2 psig (3.48 kPa).
4 − Piping should be sloped 1/4 inch per 15 feet (6mm per
5.6m) upward toward the gas meter from the furnace.
The piping must be supported at proper intervals, ev-
ery 8 to 10 feet (2.44 to 3.05m), using suitable hangers
or straps. Install a drip leg in vertical pipe runs to serve as
a trap for sediment or condensate.
WARNING
FIRE OR EXPLOSION HAZARD
5 − A 1/8" N.P.T. plugged tap or pressure post is located
on the gas valve to facilitate test gauge connection.
Failure to follow the safety warnings exactly could
result in serious injury, death, or property damage.
Never use an open flame to test for gas leaks. Check
all connections using a commercially available soap
solution made specifically for leak detection. Some
soaps used for leak detection are corrosive to certain
metals. Carefully rinse piping thoroughly after leak
test has been completed.
6 − In some localities, codes may require installation of a
manual main shut-off valve and union (furnished by in-
staller) external to the unit. Union must be of the
ground joint type.
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Left Side Piping
(Standard)
MANUAL
MAIN SHUT−OFF
VALVE
(With 1/8 in. NPT
Plugged Tap
Shown)
GROUND
JOINT
UNION
AUTOMATIC
GAS VALVE
(with manual
shut−off valve)
MANUAL
MAIN SHUT−OFF
VALVE
(With 1/8 in. NPT
Plugged Tap Shown)
AUTOMATIC
GAS VALVE
(with manual
shut−off valve)
Plug
Plug
GROUND
JOINT
UNION
DRIP LEG
Right Side Piping
(Alternate)
FIELD
PROVIDED
AND INSTALLED
DRIP LEG
Bellows Grommet
Bellows Grommet
NOTE − BLACK IRON PIPE ONLY TO BE ROUTED INSIDE OF CABINET
FIGURE 47
TABLE 10
GAS PIPE CAPACITY − FT3/HR (kL/HR)
Length of Pipe−Feet(m)
Nominal
Iron Pipe Size
−Inches(mm)
Internal
Diameter
−Inches(mm)
10
(3.048)
20
(6.096)
30
(9.144)
40
50
60
70
80
90
100
(12.192) (15.240) (18.288) (21.336) (24.384) (27.432) (30.480)
1/2
(12.7)
.622
(17.799)
175
(4.96)
120
(3.40)
97
(2.75)
82
(2.32)
73
(2.07)
66
(1.87)
61
(1.73)
57
(1.61)
53
(1.50)
50
(1.42)
3/4
(19.05)
.824
(20.930)
360
(10.19)
250
(7.08)
200
(5.66)
170
(4.81)
151
(4.28)
138
(3.91)
125
(3.54)
118
(3.34)
110
(3.11)
103
(2.92)
1
(25.4)
1.049
(26.645)
680
(19.25)
465
(13.17)
375
(10.62)
320
(9.06)
285
(8.07)
260
(7.36)
240
(6.80)
220
(6.23)
205
(5.80)
195
(5.52)
1−1/4
(31.75)
1.380
(35.052)
1400
(39.64)
950
(26.90)
770
(21.80)
660
(18.69)
580
(16.42)
530
(15.01)
490
(13.87)
460
(13.03)
430
(12.18)
400
(11.33)
1−1/2
(38.1)
1.610
(40.894)
2100
(59.46)
460
(41.34)
1180
(33.41)
990
(28.03)
900
(25.48)
810
(22.94)
750
(21.24)
690
(19.54)
650
(18.41)
620
(17.56)
2
(50.8)
2.067
(52.502)
3950
(111.85)
2750
(77.87)
2200
(62.30)
1900
(53.80)
1680
(47.57)
1520
(43.04)
1400
(39.64)
1300
(36.81)
1220
(34.55)
1150
(32.56)
2−1/2
(63.5)
2.469
(67.713)
6300
(178.39)
4350
(123.17)
3520
(99.67)
3000
(84.95)
2650
(75.04)
2400
(67.96)
2250
(63.71)
2050
(58.05)
1950
(55.22)
1850
(52.38)
3
(76.2)
3.068
(77.927)
11000
(311.48)
7700
(218.03)
6250
(176.98)
5300
(150.07)
4750
(134.50)
4300
(121.76)
3900
(110.43)
3700
(104.77)
3450
(97.69)
3250
(92.03)
4
(101.6)
4.026
(102.260)
23000
(651.27)
15800
(447.39)
12800
(362.44)
10900
(308.64)
9700
(274.67)
8800
(249.18)
8100
(229.36)
7500
(212.37)
7200
(203.88)
6700
(189.72)
NOTE − Capacity given in cubic feet of gas per hour (kilo liters of gas per hour) and based on 0.60 specific gravity gas.
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Removal of the Furnace from Common Vent
5 − After the main burner has operated for 5 minutes, test
for leaks of flue gases at the draft hood relief opening.
Use the flame of a match or candle.
In the event that an existing furnace is removed from a
venting system commonly run with separate gas ap-
pliances, the venting system is likely to be too large to
properly vent the remaining attached appliances.
6 − After determining that each appliance connected to the
common venting system is venting properly, (step 3)
return all doors, widows, exhaust fans, fireplace damp-
ers, and any other gas−burning appliances to their pre-
vious mode of operation.
Conduct the following test while each appliance is operat-
ing and the other appliances (which are not operating) re-
main connected to the common venting system. If the
venting system has been installed improperly, you must
correct the system as indicated in the general venting re-
quirements section.
7 − If a venting problem is found during any of the preced-
ing tests, the common venting system must be modi-
fied to correct the problem.
Resize the common venting system to the minimum
vent pipe size determined by using the appropriate
tables in Appendix G. (These are in the current stan-
dards of the National Fuel Gas Code ANSI Z223.1.
WARNING
CARBON MONOXIDE POISONING HAZARD
Failure to follow the steps outlined below for each
appliance connected to the venting system being
placed into operation could result in carbon mon-
oxide poisoning or death.
The following steps shall be followed for each ap-
pliance connected to the venting system being
placed into operation, while all other appliances
connected to the venting system are not in
operation:
Electrical
ELECTROSTATIC DISCHARGE (ESD)
Precautions and Procedures
CAUTION
Electrostatic discharge can affect electronic com-
ponents. Take precautions during furnace installa-
tion and service to protect the furnace’s electronic
controls. Precautions will help to avoid control ex-
posure to electrostatic discharge by putting the fur-
nace, the control and the technician at the same
electrostatic potential. Neutralize electrostatic
charge by touching hand and all tools on an un-
painted unit surface, such as the gas valve or blower
deck, before performing any service procedure.
1 − Seal any unused openings in the common venting sys-
tem.
2 − Inspect the venting system for proper size and horizontal
pitch. Determine that there is no blockage, restriction,
leakage, corrosion, or other deficiencies which could
cause an unsafe condition.
3 − Close all building doors and windows and all doors be-
tween the space in which the appliances remaining
connected to the common venting system are located
and other spaces of the building. Turn on clothes dry-
ers and any appliances not connected to the common
venting system. Turn on any exhaust fans, such as
range hoods and bathroom exhausts, so they will oper-
ate at maximum speed. Do not operate a summer ex-
haust fan. Close fireplace dampers.
The unit is equipped with a field make−up box on the left
hand side of the cabinet. A field−provided make−up box can
be installed on the exterior of the right side of the furnace to
facilitate installation. If the make−up box is moved to the
right side, clip the wire ties that bundle the wires together
excess wire must be pulled into the blower compartment.
Secure the excess wire to the existing harness to protect it
from damage.
4 − Follow the lighting instructions. Turn on the appliance
that is being inspected. Adjust the thermostat so that
the appliance operates continuously.
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Complete the wiring connections to the equipment. Use the
provided unit wiring diagram and the field wiring diagram
able for Class II rating for thermostat connections.
INTERIOR MAKE−UP BOX
(FACTORY− INSTALLED LEFT SIDE)
Electrically ground the unit according to local codes or, in
the absence of local codes, according to the current Na-
tional Electric Code (ANSI/NFPA No. 70) for the USA and
current Canadian Electric Code part 1 (CSA standard
C22.1) for Canada. A green ground wire is provided in the
field make−up box.
MAKE−UP
BOX INSIDE
CABINET
Left side
NOTE − The ML193DF furnace contains electronic compo-
nents that are polarity sensitive. Make sure that the furnace
is wired correctly and is properly grounded.
Generator Use − Voltage Requirements
The following requirements must be kept in mind when
specifying a generator for use with this equipment:
FIGURE 48
D The furnace requires 120 volts + 10% (Range: 108
volts to 132 volts)
EXTERIOR MAKE−UP BOX
(FIELD PROVIDED RIGHT SIDE)
D The furnace operates at 60 Hz + 5% (Range: 57 Hz to
63 Hz)
D The furnace integrated control requires both polarity
and proper ground. Both polarity and proper grounding
should be checked before attempting to operate the
furnace on either permanent or temporary power
D Generator should have a wave form distortion of less
than 5% RHD
MAKE−UP
BOX
OUTSIDE
CABINET
Accessory Terminals
Right Side
One line voltage ꢂEAC" 1/4" spade terminal is provided on
control configuration. This terminal is energized when the
indoor blower is operating. Any accessory rated up to one
amp can be connected to this terminal with the neutral leg
of the circuit being connected to one of the provided neutral
terminals. If an accessory rated at greater than one amp is
connected to this terminal, it is necessary to use an exter-
nal relay.
FIGURE 49
wiring diagram and troubleshooting.
The power supply wiring must meet Class I restrictions.
Protected by either a fuse or circuit breaker, select circuit
protection and wire size according to unit nameplate.
NOTE − Unit nameplate states maximum current draw.
Maximum Over−Current Protection allowed is 15 AMP.
Holes are on both sides of the furnace cabinet to facilitate
wiring.
One line voltage ꢂHUM" 1/4" spade terminal is provided on
the furnace integrated control. See figure 53 for integrated
control configuration. This terminal is energized in the
heating mode when the combustion air inducer is operat-
ing. Any humidifier rated up to one amp can be connected
to this terminal with the neutral leg of the circuit being con-
nected to one of the provided neutral terminals. If a humidi-
fier rated at greater than one amp is connected to this termi-
nal, it is necessary to use an external relay.
Install a separate (properly sized) disconnect switch near
the furnace so that power can be turned off for servicing.
Before connecting the thermostat or the power wiring,
check to make sure the wires will be long enough for servic-
ing at a later date. Remove the blower access panel to
check the length of the wire.
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Install the room thermostat according to the instruc-
thermostat designations. If the furnace is being
matched with a heat pump, refer to the FM21 installa-
tion instruction or appropriate dual fuel thermostat in-
structions.
ML193DF and CONDENSING UNIT
THERMOSTAT DESIGNATIONS
(Refer to specific thermostat and outdoor unit.)
Thermostat
Furnace
Condensing
Unit
Indoor Blower Speeds
*CONDENSING
UNITꢃ
1 − When the thermostat is set to ꢂFAN ON," the indoor
blower will run continuously on the heating speed
when there is no cooling or heating demand.
POWER
R
R
W1
Y
HEAT
W
Y
CONDENSING
UNITꢃ
COOLING
2 − When the ML193DF is running in the heating mode,
the indoor blower will run on the heating speed.
INDOOR BLOWER
G
G
C
CONDENSING
UNITꢃ COMMON
3 − When there is a cooling demand, the indoor blower will
run on the cooling speed.
COMMON
C
*NOTE − ꢀR" REQUIRED ON SOME OUTDOOR UNITS
FIGURE 50
TYPICAL ML193DF FIELD WIRING DIAGRAM
IGNITOR
*NOTE − ꢀR" REQUIRED ON SOME OUTDOOR UNITS
*R
FIGURE 51
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INTEGRATED CONTROL
(Automatic Hot Surface Ignition System)
TERMINAL DESIGNATIONS
Humidifier (120VAC)
HUM
LINE
XFMR
EAC
Input (120VAC)
Transformer (120VAC)
Electronic Air Cleaner (120VAC)
Blower − Cooling Speed (120VAC)
Blower − Heating Speed (120VAC)
Dead terminals to park alternate spd taps
Flame sensor
COOL
HEAT
PARK
FLAME
NEUTRALS
Neutral terminals (120VAC)
3 AMP, 32 VAC FUSE
BLOWER OFF
DELAY JUMPER
FIGURE 53
Unit Start−Up
WARNING
FOR YOUR SAFETY READ BEFORE OPERATING
Danger of explosion. Can cause injury
or product or property damage. Should
the gas supply fail to shut off or if
overheating occurs, shut off the gas
valve to the furnace before shutting off
the electrical supply.
WARNING
Do not use this furnace if any part has been under-
water. A flood−damaged furnace is extremely dan-
gerous. Attempts to use the furnace can result in
fire or explosion. Immediately call a qualified ser-
vice technician to inspect the furnace and to replace
all gas controls, control system parts, and electrical
parts that have been wet or to replace the furnace,
if deemed necessary.
BEFORE LIGHTING the unit, smell all around the fur-
nace area for gas. Be sure to smell next to the floor be-
cause some gas is heavier than air and will settle on the
floor.
The gas valve on the ML193DF is equipped with a gas
control switch. Use only your hand to move switch. Never
use tools. If the switch will not move by hand, do not try to
repair it. Force or attempted repair may result in a fire or
explosion.
CAUTION
Before attempting to perform any service or mainte-
nance, turn the electrical power to unit OFF at dis-
connect switch.
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Placing the furnace into operation:
MANIFOLD
PRESSURE
ADJUSTMENT
SCREW
MANIFOLD
PRESSURE
OUTLET
ML193DF units are equipped with an automatic hot sur-
face ignition system. Do not attempt to manually light
burners on this furnace. Each time the thermostat calls
for heat, the burners will automatically light. The ignitor
does not get hot when there is no call for heat on these
units.
Priming Condensate Trap
INLET
PRESSURE
PORT
The condensate trap should be primed with water prior to
start−up to ensure proper condensate drainage. Either
pour 10 fl. oz. (300 ml) of water into the trap, or follow
these steps to prime the trap:
GAS VALVE SHOWN IN ON POSITION
FIGURE 54
12− If the appliance will not operate, follow the instructions
ꢂTurning Off Gas to Unit" and call your service techni-
cian or gas supplier.
1 − Follow the lighting instructions to place the unit into op-
eration.
2 − Set the thermostat to initiate a heating demand.
Turning Off Gas to Unit
3 − Allow the burners to fire for approximately 3 minutes.
1 − Set the thermostat to the lowest setting.
4 − Adjust the thermostat to deactivate the heating de-
mand.
2 − Turn off all electrical power to the unit if service is to be
performed.
5 − Wait for the combustion air inducer to stop. Set the
thermostat to initiate a heating demand and again al-
low the burners to fire for approximately 3 minutes.
3 − Remove the upper access panel.
4 − Move gas valve switch to OFF.
5 − Replace the upper access panel.
6 − Adjust the thermostat to deactivate the heating de-
mand and wait for the combustion air inducer to stop.
At this point, the trap should be primed with sufficient
water to ensure proper condensate drain operation.
Failure To Operate
If the unit fails to operate, check the following:
1 − Is the thermostat calling for heat?
2 − Are access panels securely in place?
3 − Is the main disconnect switch closed?
4 − Is there a blown fuse or tripped breaker?
5 − Is the filter dirty or plugged? Dirty or plugged filters will
cause the limit control to shut the unit off.
6 − Is gas turned on at the meter?
WARNING
If you do not follow these instructions exactly, a fire
or explosion may result causing property damage,
personal injury or death.
7 − Is the manual main shut-off valve open?
8 − Is the internal manual shut-off valve open?
9 − Is the unit ignition system in lockout? If the unit locks out
again, inspect the unit for blockages.
1 − STOP! Read the safety information at the beginning of
this section.
2 − Set the thermostat to the lowest setting.
3 − Turn off all electrical power to the unit.
Heating Sequence Of Operation
1 − When thermostat calls for heat, combustion air inducer
starts.
4 − This furnace is equipped with an ignition device which
automatically lights the burners. Do not try to light the
burners by hand.
2 − Combustion air pressure switch proves blower opera-
tion. Switch is factory−set and requires no adjustment.
3 − After a 15−second prepurge, the hot surface ignitor en-
ergizes.
5 − Remove the upper access panel.
4 − After a 20−second ignitor warm−up period, the gas
valve solenoid opens. A 4−second Trial for Ignition peri-
od begins."
7 − Wait five minutes to clear out any gas. If you then smell
gas, STOP! Immediately call your gas supplier from a
neighbor’s phone. Follow the gas supplier’s instruc-
tions. If you do not smell gas go to next step.
5 − Gas is ignited, flame sensor proves the flame, and the
combustion process continues.
6 − If flame is not detected after first ignition trial, the igni-
tion control will repeat steps 3 and 4 four more times
before locking out the gas valve (ꢂWATCHGUARD"
flame failure mode). The ignition control will then auto-
matically repeat steps 1 through 6 after 60 minutes.
To interrupt the 60−minute ꢂWATCHGUARD" period,
move thermostat from ꢂHeat" to ꢂOFF" then back to
ꢂHeat". Heating sequence then restarts at step 1.
9 − Replace the upper access panel.
10− Turn on all electrical power to to the unit.
11− Set the thermostat to desired setting.
NOTE − When unit is initially started, steps 1 through 11
may need to be repeated to purge air from gas line.
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Manifold Pressure Measurement
Gas Pressure Adjustment
1 − Remove the threaded plug from the outlet side of the
gas valve and install a field−provided barbed fitting.
Connect to a manometer to measure manifold pres-
sure.
Gas Flow (Approximate)
TABLE 11
GAS METER CLOCKING CHART
Seconds for One Revolution
Natural LP
2 − Start unit and allow 5 minutes for unit to reach steady
state.
ML193
Unit
3 − While waiting for the unit to stabilize, notice the flame.
Flame should be stable and should not lift from burner.
Natural gas should burn blue.
1 cu ft
Dial
80
2 cu ft
Dial
1 cu ft
Dial
2 cu ft
DIAL
−045
−070
−090
−110
160
110
82
200
136
102
82
400
272
204
164
4 − After allowing unit to stabilize for 5 minutes, record
manifold pressure and compare to value given in table
12.
55
41
33
66
NOTE − Shut unit off and remove manometer as soon as an
accurate reading has been obtained. Take care to remove
barbed fitting and replace threaded plug.
Natural−1000 btu/cu ft
LP−2500 btu/cu ft
NOTE − To obtain accurate reading, shut off all other gas
appliances connected to meter.
Proper Combustion
Furnace should operate minimum 15 minutes with correct
manifold pressure and gas flow rate before checking com-
bustion. Take combustion sample beyond the flue outlet
and compare to the tables below. The maximum carbon
Furnace should operate at least 5 minutes before check-
ing gas flow. Determine time in seconds for two revolu-
tions of gas through the meter. (Two revolutions assures a
more accurate time). Divide by two and compare to time
is incorrect, check gas orifices for proper size and restric-
tion. Remove temporary gas meter if installed.
monoxide reading should not exceed 50 ppm.
TABLE 13
ML193
CO %
2
CO %
For L.P.
For Nat
2
Unit
−045
−070
−090
−110
Supply Pressure Measurement
A threaded plug on the inlet side of the gas valve provides
access to the supply pressure tap. Remove the threaded
plug, install a field−provided barbed fitting and connect a
proper supply line pressure. Replace the threaded plug af-
ter measurements have been taken.
7.2 − 7.9
8.6 − 9.3
High Altitude Information
NOTE − In Canada, certification for installations at eleva-
tions over 4500 feet (1372 m) is the jurisdiction of local au-
thorities.
TABLE 12
Manifold and Supply Pressure (Outlet) inches w.c.
ML193DF units require no manifold pressure adjustments
for operation at altitudes up to 10,000 feet (3048 m) above
sea level. Units installed at altitude of 4501 − 10,000 feet
(1373 to 3048m) require a pressure switch change which
pressure switch requirements at varying altitudes.
Supply
Pressure in.wg.
Model
Input Sizes
Manifold
Pressure in.wg.
Fuel
Min.
Max.
Nat. Gas
L.P. Gas
All sizes
All sizes
4.5
10.0
3.5
11.0
13.0
The combustion air pressure switch is factory−set and re-
quires no adjustment.
10.0
NOTE − A natural to L.P. propane gas changeover kit is nec-
essary to convert this unit. Refer to the changeover kit
installation instruction for the conversion procedure.
NOTE − A natural to LP/propane gas changeover kit is nec-
essary to convert this unit. Refer to the changeover kit
installation instruction for the conversion procedure.
Page 38
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TABLE 14
Conversion Kit and Pressure Switch Requirements at Varying Altitudes
High Altitude
Natural Burner
Orifice Kit
High Altitude
LP/Propane
Burner Orifice Kit
Natural to
LP/Propane
LP/Propane
to Natural
High Altitude Pressure
Switch
ML193
Unit
4501 − 7500 7501 −10,000
ft
0 − 7500 ft
(0 − 2286m)
7501 − 10,000 ft
(2286 − 3038m)
0 − 7500 ft
(0 − 2286m)
7501 − 10,000 ft
(2286 − 3038m)
ft
(1373 −
2286m)
(2286 −
3048m)
−045
−070
−090
−110
*69W73
73W37
*73W81
*68W68
74W90
74W91
* Conversion requires installation of a gas valve manifold spring which is provided with the gas conversion kit.
Pressure switch is factory set. No adjustment necessary. All models use the factory−installed pressure switch from 0−4500 feet (0−1370 m).
2 − Visually inspect the venting system for proper size and
Testing of Non−Direct Vent Applications
horizontal pitch. Determine there is no blockage or re-
for Proper Venting and Sufficient
Combustion Air
striction, leakage, corrosion, or other deficiencies
which could cause an unsafe condition.
3 − To the extent that it is practical, close all building doors
and windows and all doors between the space in which
WARNING
CARBON MONOXIDE POISONING HAZARD!
the appliances connected to the venting system are lo-
cated and other spaces of the building.
Failure to follow the steps outlined below for each
appliance connected to the venting system being
placed into operation could result in carbon monox-
ide poisoning or death.
The following steps shall be followed for each ap-
pliance connected to the venting system being
placed into operation, while all other appliances con-
nected to the venting system are not in operation.
4 − Close fireplace dampers.
5 − Turn on clothes dryers and any appliances not con-
nected to the venting system. Turn on any exhaust
fans, such as range hoods and bathroom exhausts, so
they will operate at maximum speed. Do not operate a
summer exhaust fan.
6 − Follow the lighting instruction to place the appliance
being inspected into operation. Adjust thermostat so
appliance will operate continuously.
After the ML193DF gas furnace has been started, the fol-
lowing test should be conducted to ensure proper venting
and sufficient combustion air has been provided to the
ML193DF as well as to other gas-fired appliances which
are separately vented.
7 − Use the flame of match or candle to test for spillage of
flue gases at the draft hood relief opening after 5 min-
utes of main burner operation.
8 − If improper venting is observed during any of the
above tests, the venting system must be corrected or
sufficient combustion/make-up air must be provided.
The venting system should be re-sized to approach
the minimum size as determined by using the ap-
propriate tables in appendix G in the current standards
of the National Fuel Gas Code ANSI−Z223.1/NPFA 54
in the U.S.A., and the appropriate Natural Gas and
Propane appliances venting sizing tables in the cur-
rent standard of the CSA−B149 Natural Gas and Pro-
pane Installation Codes in Canada.
If a ML193DF furnace replaces a Category I furnace which
was commonly vented with another gas appliance, the size
of the existing vent pipe for that gas appliance must be
checked. Without the heat of the original furnace flue prod-
ucts, the existing vent pipe is probably oversized for the
single water heater or other appliance. The vent should be
checked for proper draw with the remaining appliance.
The test should be conducted while all appliances (both in
operation and those not in operation) are connected to the
venting system being tested. If the venting system has
been installed improperly, or if provisions have not been
made for sufficient amounts of combustion air, corrections
must be made as outlined in the previous section.
9 − After determining that each appliance remaining
connected to the common venting system properly
vents when tested as indicated in step 3, return
doors, windows, exhaust fans, fireplace dampers
and any other gas-burning appliance to their previous
condition of use.
1 − Seal any unused openings in the venting system.
Page 39
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Other Unit Adjustments
HEAT FAN-OFF TIME IN SECONDS
NOTE − See troubleshooting flow charts if any safety
switches are found to be open.
Primary Limit
The primary limit is located on the heating compartment
vestibule panel. This limit is factory set and requires no ad-
justment.
NO JUMPER
To adjust fan−off timing, reposition jumper across pins to
achieve desired setting.
Flame Rollout Switches (Two)
60 Second
off Time
90 Second
off Time
120 Second
off Time
180 Second
off Time
These manually reset switches are located on the front of
the burner box.
Pressure Switch
The pressure switch is located in the heating compartment
on the cold end header box. This switch checks for proper
combustion air inducer operation before allowing ignition
trial. The switch is factory−set and must not be adjusted.
FIGURE 55
Temperature Rise
After the furnace has been started and supply and return air
temperatures have been allowed to stabilize, check the
temperature rise. If necessary, adjust the blower speed to
maintain the temperature rise within the range shown on
the unit nameplate. Increase the blower speed to decrease
the temperature. Decrease the blower speed to increase
the temperature rise. Failure to adjust the temperature rise
may cause erratic limit operation.
Blower Speeds
Follow the steps below to change the blower speeds.
1 − Turn off electrical power to furnace.
2 − Remove blower access panel.
3 − Disconnect existing speed tap at integrated control
speed terminal.
NOTE − Termination of any unused motor leads must be
insulated.
Fan Control
The fan on time of 30 seconds is not adjustable. The fan off
delay (amount of time that the blower operates after the
heat demand has been satisfied) may be adjusted by
changing the jumper position across the five pins on the
integrated control. The unit is shipped with a factory fan off
setting of 90 seconds. The fan off delay affects comfort and
is adjustable to satisfy individual applications. Adjust the
fan off delay to achieve a supply air temperature between
90° and 110°F at the moment that the blower is de−ener-
gized. Longer off delay settings provide lower return air
temperatures; shorter settings provide higher return air
4 − Place unused blower speed tap on integrated control
ꢂPARK" terminal or insulate.
5 − Refer to blower speed selection chart on unit wiring dia-
gram for desired heating or cooling speed. See Blower
performance data beginning on the next page.
6 − Connect selected speed tap at integrated control
speed terminal.
7 − Resecure blower access panel.
8 − Turn on electrical power to furnace.
9 − Recheck temperature rise.
Thermostat Heat Anticipation
Set the heat anticipator setting (if adjustable) according to
the amp draw listed on the wiring diagram that is attached
to the unit.
Exhaust and Air Intake Pipe
1 − Check exhaust and air intake connections for tightness
and to make sure there is no blockage.
Electrical
2 − Is pressure switch closed? Obstructed exhaust pipe
will cause unit to shut off at pressure switch. Check ter-
mination for blockages.
1 − Check all wiring for loose connections.
2 − Check for the correct voltage at the furnace (furnace
operating).
3 − Obstructed pipe or termination may cause rollout
switches to open. Reset manual flame rollout switches
on burner box assembly if necessary.
3 − Check amp-draw on the blower motor.
Motor Nameplate__________Actual__________
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BLOWER DATA
ML193DF045P36B PERFORMANCE (Less Filter)
ML193DF090P48C PERFORMANCE (Less Filter)
Air Volume / Watts at Various Blower Speeds
Air Volume / Watts at Various Blower Speeds
External
Static
Pressure
in. w.g.
External
Medium-
Medium-
Medium-
Medium-
Static
Pressure
in. w.g.
High
Low
High
Low
High
Low
High
Low
cfm Watts cfm Watts cfm Watts cfm Watts
1615 650 1385 555 1205 465 1045 390
1605 640 1375 545 1195 455 1035 380
1500 620 1340 525 1165 445 1015 370
1450 590 1290 490 1125 420 975 365
1350 560 1235 480 1090 405 920 345
1300 545 1170 450 1035 380 875 335
1195 500 1095 425 990 365 840 320
1140 485 1020 400 895 345 780 300
1025 450 920 370 840 330 695 275
945 435 800 335 700 295 605 250
cfm Watts cfm Watts cfm Watts cfm Watts
2145 900 1865 740 1545 635 1295 530
2135 890 1855 730 1540 625 1290 520
2065 845 1815 710 1525 600 1285 500
2010 825 1760 685 1510 580 1275 485
1930 775 1705 630 1495 575 1235 455
1845 740 1645 610 1450 530 1215 450
1745 700 1525 550 1380 505 1185 430
1620 650 1460 535 1315 480 1110 405
1450 585 1340 505 1220 445 1020 375
1320 555 1130 450 1010 385 920 345
0.00
0.10
0.20
0.30
0.40
0.50
0.60
0.70
0.80
0.90
0.00
0.10
0.20
0.30
0.40
0.50
0.60
0.70
0.80
0.90
ML193DF070P36B PERFORMANCE (Less Filter)
ML193DF110P60C PERFORMANCE (Less Filter)
Air Volume / Watts at Various Blower Speeds
Air Volume / Watts at Various Blower Speeds
External
External
Medium-
High
Medium-
Low
Medium-
High
Medium-
Low
Static
Pressure
in. w.g.
Static
Pressure
in. w.g.
High
Low
High
Low
cfm Watts cfm Watts cfm Watts cfm Watts
1505 660 1310 570 1090 455 940 390
1480 625 1295 550 1070 435 935 365
1405 585 1255 515 1055 425 930 350
1355 580 1225 475 1045 405 900 330
1305 540 1165 470 1010 385 890 325
1270 525 1110 425 975 370 835 305
1175 500 1080 415 925 345 815 290
1105 460 1000 395 855 320 745 270
1040 440 925 365 790 300 670 250
920 400 825 335 680 270 560 225
cfm Watts cfm Watts cfm Watts cfm Watts
2410 1390 2190 1080 1860 910 1560 735
2405 1385 2180 1070 1855 905 1555 730
2285 1345 2120 1030 1850 865 1540 720
2220 1315 2015 1005 1770 840 1535 705
2185 1295 1950 955 1750 815 1530 685
2045 1240 1830 925 1680 790 1500 660
1965 1220 1710 890 1575 755 1445 640
1820 1165 1610 850 1495 720 1370 615
1625 1155 1510 820 1400 695 1315 595
1455 1110 1390 790 1350 660 1210 565
0.00
0.10
0.20
0.30
0.40
0.50
0.60
0.70
0.80
0.90
0.00
0.10
0.20
0.30
0.40
0.50
0.60
0.70
0.80
0.90
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3 − Remove the clean out cap from the condensate trap
and empty water. Inspect the trap then reinstall the
drain plug.
Service
Cleaning Heat Exchanger
WARNING
ELECTRICAL SHOCK, FIRE,
OR EXPLOSION HAZARD.
If cleaning the heat exchanger becomes necessary, follow
the below procedures and refer to figure 1 when disassem-
bling unit. Use papers or protective covering in front of fur-
nace while removing heat exchanger assembly.
Failure to follow safety warnings exactly could result
in dangerous operation, serious injury, death or
property damage.
Improper servicing could result in dangerous opera-
tion, serious injury, death, or property damage.
Before servicing, disconnect all electrical power to
furnace.
1 − Turn off electrical and gas supplies to the furnace.
2 − Remove the furnace access panels.
3 − Disconnect the 2 wires from the gas valve.
4 − Remove gas supply line connected to gas valve. Re-
move gas valve/manifold assembly.
When servicing controls, label all wires prior to dis-
connecting. Take care to reconnect wires correctly.
Verify proper operation after servicing.
5 − Remove sensor wire from sensor. Disconnect 2-pin
plug from the ignitor.
6 − Disconnect wires from flame roll−out switches.
7 − Loosen clamps at vent elbow. Disconnect condensate
drain tubing from flue collar. and remove the vent el-
bow.
At the beginning of each heating season, system should be
checked as follows by a qualified service technician:
Blower
8 − Remove four burner box screws at the vestibule panel
and remove burner box. Set burner box assembly
aside.
Check the blower wheel for debris and clean if necessary.
The blower motors are prelubricated for extended bearing
life. No further lubrication is needed.
NOTE − If necessary, clean burners at this time. Follow
procedures outlined in Burner Cleaning section.
9 − Mark and disconnect all combustion air pressure tub-
ing from cold end header collector box.
WARNING
10 − Mark and remove wires from pressure switches. Re-
move pressure switches. Keep tubing attached to
pressure switches.
The blower access panel must be securely in place
when the blower and burners are operating. Gas
fumes, which could contain carbon monoxide, can
be drawn into living space resulting in personal inju-
ry or death.
11 − Disconnect the plug from the combustion air inducer.
Remove two screws which secure combustion air in-
ducer to collector box. Remove combustion air induc-
er assembly. Remove ground wire from vest panel.
Filters
All air filters are installed external to the unit. Filters should
be inspected monthly. Clean or replace the filters when
lists recommended filter sizes.
12 − Remove electrical junction box from the side of the fur-
nace.
13 − Mark and disconnect any remaining wiring to heating
compartment components. Disengage strain relief
bushing and pull wiring and bushing through the hole in
the blower deck.
Exhaust and air intake pipes
Check the exhaust and air intake pipes and all connections
for tightness and to make sure there is no blockage.
14 − Remove the primary limit from the vestibule panel.
15 − Remove two screws from the front cabinet flange at
the blower deck. Spread cabinet sides slightly to allow
clearance for removal of heat exchanger.
NOTE − After any heavy snow, ice or frozen fog event the
furnace vent pipes may become restricted. Always check
the vent system and remove any snow or ice that may be
obstructing the plastic intake or exhaust pipes.
16 − Remove screws along vestibule sides and bottom
which secure vestibule panel and heat exchanger as-
sembly to cabinet. Remove two screws from blower
rail which secure bottom heat exchanger flange. Re-
move heat exchanger from furnace cabinet.
Electrical
1 − Check all wiring for loose connections.
2 − Check for the correct voltage at the furnace (furnace
operating).
17 − Back wash heat exchanger with soapy water solution
or steam. If steam is used it must be below 275°F
(135°C) .
3 − Check amp−draw on the blower motor.
Motor Nameplate__________Actual__________
Winterizing and Condensate Trap Care
1 − Turn off power to the furnace.
18 − Thoroughly rinse and drain the heat exchanger. Soap
solutions can be corrosive. Take care to rinse entire
assembly.
2 − Have a shallow pan ready to empty condensate water.
Page 42
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19 − Reinstall heat exchanger into cabinet making sure that
the clamshells of the heat exchanger assembly are
resting on the support located at the rear of the cabi-
net. Remove the indoor blower to view this area
through the blower opening.
38 − Follow lighting instructions to light and operate fur-
nace for 5 minutes to ensure that heat exchanger is
clean and dry and that furnace is operating properly.
39 − Replace heating compartment access panel.
Cleaning the Burner Assembly
20 − Re-secure the supporting screws along the vestibule
sides and bottom to the cabinet. Reinstall blower and
mounting screws.
1 − Turn off electrical and gas power supplies to furnace.
Remove upper and lower furnace access panels.
2 − Disconnect the 2−pin plug from the gas valve.
3 − Remove the burner box cover.
21 − Reinstall cabinet screws on front flange at blower
deck.
4 − Disconnect the gas supply line from the gas valve. Re-
move gas valve/manifold assembly.
22 − Reinstall the primary limit on the vestibule panel.
23 − Route heating component wiring through hole in blow-
er deck and reinsert strain relief bushing.
24 − Reinstall electrical junction box.
5 − Mark and disconnect sensor wire from the sensor. Dis-
connect 2-pin plug from the ignitor at the burner box.
6 − Remove four screws which secure burner box assem-
bly to vest panel. Remove burner box from the unit.
25 − Reinstall the combustion air inducer. Reconnect the
combustion air inducer to the wire harness.
7 − Use the soft brush attachment on a vacuum cleaner to
gently clean the face of the burners. Visually inspect
the inside of the burners and crossovers for any block-
age caused by foreign matter. Remove any blockage.
26 − Reinstall pressure switches and reconnect pressure
switch wiring.
27 − Carefully connect combustion air pressure switch
hosing from pressure switches to proper stubs on
cold end header collector box.
8 − Reconnect the sensor wire and reconnect the 2−pin
plug to the ignitor wiring harness.
28 − Reinstall condensate trap.
9 − Reinstall the burner box assembly using the existing
four screws. Make sure that the burners line up in the
center of the burner ports.
29 − Reconnect exhaust piping and exhaust drain tubing.
30 − Reinstall burner box assembly in vestibule area.
31 − Reconnect flame roll−out switch wires.
10 − Reinstall the gas valve manifold assembly. Reconnect
the gas supply line to the gas valve. Reinstall the burn-
er box cover.
32 − Reconnect sensor wire and reconnect 2−pin plug from
ignitor.
33 − Secure burner box assembly to vestibule panel using
four existing screws. Make sure burners line up in
center of burner ports.
11 − Reconnect 2−pin plug to gas valve.
12 − Replace the blower compartment access panel.
34 − Reinstall gas valve manifold assembly. Reconnect
gas supply line to gas valve.
13 − Refer to instruction on verifying gas and electrical con-
nections when re−establishing supplies.
35 − Reconnect 2 wires to gas valve.
14 − Follow lighting instructions to light and operate fur-
nace for 5 minutes to ensure that heat exchanger is
clean and dry and that furnace is operating properly.
36 − Replace the blower compartment access panel.
37 − Refer to instruction on verifying gas and electrical con-
nections when re−establishing supplies.
15 − Replace heating compartment access panel.
Page 43
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Return air duct − Must be properly attached and provide
Planned Service
an air seal to the unit.
A service technician should check the following items dur-
ing an annual inspection. Power to the unit must be shut off
for safety.
Operating performance − Unit must be observed during
operation to monitor proper performance of the unit and the
vent system.
Fresh air grilles and louvers (on the unit and in the room
where the furnace is installed) − Must be open and unob-
structed to provide combustion air.
Combustion gases − Flue products must be analyzed and
compared to the unit specifications.
Problems detected during the inspection may make it nec-
essary to temporarily shut down the furnace until the items
can be repaired or replaced.
Burners − Must be inspected for rust, dirt, or signs of water.
Vent pipe − Must be inspected for signs of water, cracked,
damaged or sagging pipe, or disconnected joints.
Instruct the homeowners to pay attention to their
furnace. Situations can arise between annual furnace in-
spections that may result in unsafe operation. For instance,
items innocently stored next to the furnace may obstruct
the combustion air supply. This could cause incomplete
combustion and the production of carbon monoxide gas.
Unit appearance − Must be inspected for rust, dirt, signs
of water, burnt or damaged wires, or components.
Blower access door − Must be properly in place and pro-
vide a seal between the return air and the room where the
furnace is installed.
Ignition Control Board Diagnostic Codes
DIAGNOSTIC CODES
Make sure to Identify LED’S Correctly.
LED #1 (Red)
LED #2 (Green)
DESCRIPTION
SIMULTANEOUS
SLOW FLASH
SIMULTANEOUS
SLOW FLASH
Power on − Normal operation.
Also signaled during cooling and continuous fan.
SIMULTANEOUS
FAST FLASH
SIMULTANEOUS
FAST FLASH
Normal operation − signaled when heating demand initiated at thermostat.
Primary limit switch open. Limit must close within 3 minutes or unit goes into 1
hour Watchguard.
SLOW FLASH
OFF
ON
Pressure prove switch open.
SLOW FLASH
OR: Blocked inlet/exhaust vent;
OR: Pressure switch closed prior to activation of combustion air inducer.
ALTERNATING
SLOW FLASH
ALTERNATING
SLOW FLASH
Watchguard 1 hour −− burners failed to ignite or lost flame 5 times during single
heating demand.
SLOW FLASH
ON
OFF
Flame sensed without gas valve energized.
SLOW FLASH
Rollout switch open. OR: 12-pin connector improperly attached.
ON
ON
ON
OFF
Circuit board failure or control wired incorrectly.
OFF
ON
FAST FLASH
SLOW FLASH
Main power polarity reversed. Switch line and neutral.
SLOW FLASH
FAST FLASH
Low flame signal. Measures below 1.5 microamps. Replace flame sense rod.
ALTERNATING
FAST FLASH
ALTERNATING
FAST FLASH
Improper main ground.
OR: Line voltage below 90 volts.
NOTE − Slow flash rate equals 1 Hz (one flash per second). Fast flash rate equals 3 Hz (three flashes per second).
Minimum flame sense current = 0.5 microAmps.
Page 44
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Troubleshooting: Heating Sequence of Operation
HEATING SEQUENCE OF OPERATION
ABNORMAL HEATING MODE
NORMAL HEATING MODE
POWER ON
GAS VALVE OFF. COMBUSTION AIR INDUCER OFF.
INDOOR BLOWER DELAY OFF.
LED #1 ON
NO
CONTROL SELF−CHECK OKAY?
LED #2 ON
(RESET CONTROL BY TURNING MAIN POWER OFF.)
YES
NO
POLARITY REVERSED.
LED #1 −− FAST FLASH
LED #2 −− SLOW FLASH
IS POLARITY CORRECT?
YES
NO
IMPROPER GROUND.
LED #1 −− ALTERNATING FAST FLASH
LED #2 −− ALTERNATING FAST FLASH
IS THERE A PROPER GROUND?
YES
NO
LEDs SIGNAL FAST ALTERNATING FLASH.
CONTROL WILL NOT RESPOND TO A CALL FOR
HEATING UNTIL VOLTAGE RISES ABOVE 95 VOLTS.
IS VOLTAGE
ABOVE 90 VOLTS?
GAS VALVE OFF. COMBUSTION AIR INDUCER ON.
INDOOR BLOWER ON.
LED #1 −− ON. LED #2 −− SLOW FLASH.
YES
NO
ROLLOUT SWITCH CLOSED?
SEQUENCE HOLDS UNTIL ROLLOUT SWITCH CLOSES
AND POWER IS RESET OR T’STAT IS INTERRUPTED
FOR MINIMUM OF 1 SECOND.
YES
GAS VALVE OFF. COMBUSTION AIR INDUCER ON.
INDOOR BLOWER ON HEATING SPEED.
LED #1 −− SLOW FLASH
NO
BURNER OFF?
(Flame sensed without gas valve energized)
LED #2 −− OFF
YES
NO
NORMAL OPERATION:
LED #1 −− SLOW FLASH
LED #2 −− SLOW FLASH
YES
COMBUSTION AIR INDUCER OFF.
INDOOR BLOWER ON
LED #1 SLOW FLASH RATE
LED #2 −− ON
THERMOSTAT CALLS FOR HEAT:
LED #1 −− FAST FLASH
LED #2 −− FAST FLASH
NO
YES
PRIMARY LIMIT SWITCH. CLOSED?
GAS VALVE OFF.
COMBUSTION AIR INDUCER OFF.
YES
INDOOR BLOWER OFF WITH DELAY.
LED #1 OFF
LED #2 SLOW FLASH
NO
IS COMBUSTION AIR
PRESSURE SWITCH OPEN?
(Sequence holds until pressure switch
opens or thermostat resets control.)
YES
IS COMBUSTION AIR INDUCER
ENERGIZED?
YES
PRESSURE SWITCH IS IN WATCHGUARD MODE.
GAS VALVE OFF. COMBUSTION AIR INDUCER OFF.
INDOOR BLOWER OFF WITH DELAY.
YES
NO
HAS COMBUSTION AIR PRESSURE
SWITCH CLOSED IN 2.5 MINUTES?
LED #1 −− OFF. LED #2 −− SLOW FLASH.
IS 5-MINUTE RESET PERIOD COMPLETE?
YES
CONTINUED NEXT PAGE
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Troubleshooting: Heating Sequence of Operation (Continued)
HEATING SEQUENCE CONTINUED
NORMAL HEATING MODE
ABNORMAL HEATING MODE
15-SECOND COMBUSTION AIR INDUCER PREPURGE
INITIATED BY CLOSED PRESSURE SWITCH.
LEDS SIGNAL
ALTERNATING
YES
NO
NO
FAST FLASH UNTIL
VOLTAGE IS ABOVE
95 VOLTS, THEN
RESTARTS HEATING
SEQUENCE.
IS VOLTAGE ABOVE 90 VOLTS?
IGNITOR WARM-UP −− 20 SECONDS.
YES
YES
4-SECOND TRIAL FOR IGNITION.
GAS VALVE OPENS. IGNITOR ENERGIZED FOR
FIRST 3 SECONDS OF THE TRIAL.
GAS VALVE OFF. COMBUSTION AIR INDUCER ON.
INDOOR BLOWER OFF.
HAS CONTROL FAILED TO SENSE FLAME FOR
FIVE CONSECUTIVE TRIES DURING A SINGLE
HEAT DEMAND?
YES
NO
NO
FLAME STABILIZATION PERIOD.
4 SECONDS
YES
FLAME RECTIFICATION CURRENT
CHECK. CAN FLAME BE PROVEN WITHIN
4 SECONDS AFTER GAS VALVE OPENS?
(0.5 microamps)
WATCHGUARD MODE. GAS VALVE OFF.
COMBUSTION AIR INDUCER OFF.
INDOOR BLOWER OFF WITH DELAY
LEDs SIGNAL WATCHGUARD FAILURE CODE.
IS 60-MINUTE RESET PERIOD COMPLETE?
YES
YES
NO
NO
YES
HAS CONTROL RESET IGNITION
SEQUENCE FOUR TIMES?
FLAME PRESENT?
YES
LIMIT SWITCH WATCHGUARD
MODE. GAS VALVE, COMB. AIR
INDUCER AND INDOOR BLOW-
ER OFF. LEDs SIGNAL LIMIT
SWITCH OPEN UNTIL MAIN
POWER IS
LOW FLAME SIGNAL
(Does not affect operation of control)
LED #1 −− SLOW FLASH
NO
FLAME SIGNAL 1.5 MICROAMPS OR GREATER?
YES
LED #2 −− FAST FLASH
INDOOR BLOWER ON
AFTER 30−SECOND DELAY
INTERRUPTED OR
T’STAT IS CYCLED
GAS VALVE DE−ENERGIZED.
COMBUSTION AIR INDUCER DE−ENERGIZED.
YES
OFF/ON FOR 1 SEC.
MINIMUM. 60−MINUTE
WATCHGUARD PE-
RIOD STARTS AT
TIME LIMIT CLOSES.
IS 60−MIN. PERIOD
COMPLETE?
INDOOR BLOWER ON UNTIL SWITCH CLOSES.
LED #1 −− SLOW FLASH. LED #2 −− ON.
IS LIMIT SWITCH CLOSED?
NO
PRIMARY AND SECONDARY LIMIT
SWITCHES CLOSED?
YES
YES
HAS PRIMARY LIMIT RESET
TIME EXCEEDED 3 MINUTES?
YES
NO
GAS VALVE POWER OFF.
NO
COMBUSTION AIR INDUCER POWER ON.
INDOOR BLOWER ON
LED #1 −− ON. LED #2 −− SLOW FLASH.
ROLLOUT SWITCH CLOSED?
YES
SEQUENCE HOLDS UNTIL ROLLOUT SWITCH IS RESET
AND MAIN POWER IS INTERRUPTED OR
THERMOSTAT IS CYCLED OFF/ON FOR 1 SEC. MINIMUM.
NO
COMBUSTION AIR PRESSURE
SWITCH CLOSED?
YES
GAS VALVE DE−ENERGIZED.
COMBUSTION AIR INDUCER ON.
INDOOR BLOWER OFF WITH DELAY
LED #1 −− OFF. LED #2 −− SLOW FLASH.
HAS CAB SWITCH CLOSED IN 2.5 MINUTES?
YES
THERMOSTAT DEMAND SATISFIED.
YES
LED #1 & #2 SIMULTANEOUS SLOW FLASHES.
NO
YES
5-MINUTE PRESSURE SWITCH
WATCHGUARD MODE.
COMB. AIR INDUCER CONTINUES 5-SECOND
POST PURGE AFTER T’STAT DEMAND IS SATISFIED.
INDOOR AIR BLOWER COMPLETES SELECTED ꢂOFF"
DELAY BEFORE SHUTTING OFF.
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Troubleshooting: Cooling Sequence of Operation
COOLING SEQUENCE OF OPERATION
NORMAL COOLING MODE
ABNORMAL COOLING MODE
POWER ON
IGNITION CONTROL MAIN POWER ON.
GAS VALVE OFF. COMBUSTION AIR INDUCER OFF.
INDOOR BLOWER OFF WITH NORMAL DELAY.
SIGNAL CIRCUIT BOARD FAILURE AT LED.
NO
CONTROL SELF DIAGNOSTIC CHECK.
IS CONTROL OPERATING NORMALLY?
INTERRUPT MAIN POWER TO RESET CONTROL.
YES
NO
SIGNAL IMPROPER GROUND AT LED.
CONTROL WILL CONTINUE TO CALL FOR COOLING
IN THIS CONDITION.
IS THERE A PROPER GROUND?
YES
SIGNAL POLARITY REVERSED AT LED. CONTROL
WILL CONTINUE TO CALL FOR COOLING IN THIS
CONDITION.
NO
IS POLARITY CORRECT?
YES
NO
LED SIGNALS LOW VOLTAGE. CONTROL WILL
CONTINUE TO CALL FOR COOLING
IN THIS CONDITION.
IS VOLTAGE
ABOVE 90 VOLTS?
YES
GAS VALVE OFF. COMBUSTION AIR INDUCER ON.
INDOOR BLOWER ON.
NO
ROLLOUT SWITCH MONITORED CONTINUOUSLY.
IS ROLLOUT SWITCH CLOSED?
SIGNAL ROLL-OUT SWITCH OPEN AT LED.
SEQUENCE HOLDS UNTIL ROLLOUT SWITCH CLOSES
AND MAIN POWER IS INTERRUPTED OR THERMOSTAT
IS CYCLED OFF/ON FOR 1 SEC. MINIMUM.
YES
LED: SLOW FLASH RATE REMAINS UNCHANGED
THROUGHOUT COOLING CYCLE.
THERMOSTAT CALLS FOR COOLING.
COMPRESSOR CONTACTOR AND SYSTEM FAN
ENERGIZED WITH 2-SECOND DELAY
(COOLING SPEED). EAC TERM. ENERGIZED.
THERMOSTAT OPENS.
COMPRESSOR OFF.
SYSTEM FAN AND EAC TERM. OFF
WITH 45-SECOND DELAY.
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Troubleshooting: Continuous Fan Sequence of Operation
CONTINUOUS HEAT SPEED FAN SEQUENCE OF OPERATION
LED: SLOW FLASH RATE REMAINS
UNCHANGED THROUGHOUT SEQUENCE.
MANUAL FAN SELECTION MADE AT THERMOSTAT.
CONTROL (G) ENERGIZES SYSTEM FAN AT HEAT
SPEED. EAC TERMINAL IS ENERGIZED.
HUM TERM. ENERGIZES
WITH COMB. AIR INDUCER.
THERMOSTAT CALLS FOR HEAT (W).
YES
NO
SYSTEM FAN REMAINS ON
HEATING SPEED.
THERMOSTAT CALLS FOR COOLING.
YES
NO
SYSTEM FAN SWITCHED TO COOL SPEED.
EAC TERM. REMAINS ON.
THERMOSTAT OPENS.
HUM TERM. DE−ENERGIZES
WITH COMB. AIR INDUCER
THERMOSTAT OPENS.
MANUAL FAN SELECTION MADE AT THERMOSTAT.
CONTROL (G) ENERGIZES SYSTEM FAN AT HEAT
SPEED. EAC TERM. ENERGIZED.
SYSTEM FAN REMAINS ON
HEATING SPEED.
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Repair Parts List
The following repair parts are available through Lennox dealers. When ordering parts, include the complete furnace model
number listed on the CSA nameplate −− Example: ML193DF04536B. All service must be performed by a licensed pro-
fessional installer (or equivalent), service agency, or gas supplier.
Cabinet Parts
Upper access panel
Heating Parts
Flame Sensor
Blower access panel
Top Cap
Heat exchanger assembly
Gas manifold
Control Panel Parts
Transformer
Combustion air inducer
Gas valve
Integrated control board
Door interlock switch
Blower Parts
Main burner cluster
Main burner orifices
Pressure switch
Blower wheel
Ignitor
Motor
Primary limit control
Flame rollout switches
Motor mounting frame
Motor capacitor
Blower housing cutoff plate
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Start−Up & Performance Check List
UNIT SET UP
Furnace:
Model Number_______________
Serial Number_________________
SUPPLY
AIR
Line Voltage
2
4
1
GAS SUPPLY
Natural Gas
LP Propane Gas
3
Piping Connections Tight
Leak Tested
Flter
RETURN AIR
2
Supply Line Pressure ꢀW.C.________
1
Gas Supply Pressure
DUCT SYSTEM
3
1
SUPPLY AIR DUCT
Sealed
Insulated (if necessary)
RETURN DUCT
Sealed
2
INTAKE / EXHAUST PIPE
All Joints Primed and Glued
Filter Installed and Clean
Terminations Installed Properly
Grilles Unobstructed
Horizontal Pipes Sloped (if applicable)
Condensate Trap Primed / Line Sloped
VOLTAGE CHECK
4
Supply Voltage _____
Electrical Connections Tight
Pipes Supported
Heat Cable Installed and Operable (if applicable)
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UNIT OPERATION
HEATING MODE
COOLING MODE
GAS MANIFOLD PRESSURE ꢀW.C._____
1
2
INDOOR BLOWER AMPS______
3
4
COMBUSTION SAMPLE CO % CO PPM_______
2 ______
TEMPERATURE DROP
Return Duct Temperature _________
_
INDOOR BLOWER AMPS______
TEMPERATURE RISE
3
4
Supply Duct Temperature _______
Temperature Drop = _________
5
TOTAL EXTERNAL STATIC (dry coil)
Supply External Static _______
Supply Duct Temperature ________
_
Return Duct Temperature
_____
Return External Static + ______
Total External Static = _______
Temperature Rise = ________
TOTAL EXTERNAL STATIC
5
8
DRAIN LINE
Leak Free
Supply External Static _______
Return External Static + ______
Total External Static = _______
THERMOSTAT
6
7
9
CONDENSATE LINE
Leak Free
Adjusted and Programmed
Explained Operation to Owner
VENT PIPE
Leak Free
Combustion CO
2
2
7
SUPPLY
AIR
Thermostat
Temperatures
8
Gas Manifold Pressure
9
4
1
Blower Motor Amps
6
3
Duct Static
5
RETURN AIR
Contractor’s: Name_________________________Telephone_____________Checklist Completed____________________
Job Address_____−________________________________Technician’s Name___________________________________
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Requirements for Commonwealth of Massachusetts
Modifications to NFPA−54, Chapter 10
4 − INSPECTION. The state or local gas inspector of the
side wall, horizontally vented, gas−fueled equipment
shall not approve the installation unless, upon inspec-
tion, the inspector observes carbon monoxide detec-
tors and signage installed in accordance with the pro-
visions of 248 CMR 5.08(2)(a) 1 through 4.
Revise NFPA−54 section 10.8.3 to add the following re-
quirements:
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 above the finished grade in the area of the venting, in-
cluding but not limited to decks and porches, the following
requirements shall be satisfied:
EXEMPTIONS: The following equipment is exempt
from 24 CMR 5.08(2)(a) 1 through 4:
1 − The equipment listed in Chapter 10 entitled ꢂEquip-
ment Not Required to Be Vented" in the most current
edition of NFPA 54 as adopted by the Board; and
2 − Product Approved side wall, horizontally vented, gas−
fueled equipment installed in a room or structure sepa-
rate from the dwelling, building or structure used in
whole or in part for residential purposes.
1 − INSTALLATION OF CARBON MONOXIDE DETEC-
TORS. At the time of installation of the side wall, hori-
zontally vented, gas−fueled equipment, the installing
plumber or gasfitter shall observe that a hard−wired
carbon monoxide detector with an alarm and battery
backup is installed on the floor level where the gas
equipment is to be installed. In addition, the installing
plumber or gasfitter shall observe that a battery−oper-
ated or hard−wired carbon monoxide detector with an
alarm is installed on each additional level of the dwell-
ing, building or structure served by the side wall, hori-
zontally vented, gas−fueled equipment. It shall be the
responsibility of the property owner to secure the ser-
vices of qualified licensed professionals for the instal-
lation of hard−wired carbon monoxide detectors.
MANUFACTURER REQUIREMENTS −
GAS EQUIPMENT VENTING SYSTEM PROVIDED.
When the manufacturer of Product Approved side wall,
horizontally vented, gas−fueled equipment provides a vent-
ing system design or venting system components with the
equipment, the instructions provided by the manufacturer
for installation of the equipment and the venting system
shall include:
1 − Detailed instructions for the installation of the venting
system design or the venting system components:
and
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 detec-
tor with alarm and battery back−up may be installed
on the next adjacent floor level.
2 − A complete parts list for the venting system design or
venting system.
MANUFACTURER REQUIREMENTS −
GAS EQUIPMENT VENTING SYSTEM NOT PROVIDED.
b − In the event that the requirements of this subdivi-
sion cannot be met at the time of completion of
installation, the owner shall have a period of thirty
(30) days to comply with the above requirements;
provided, however, that during said thirty (30) day
period, a battery−operated carbon monoxide detec-
tor with an alarm shall be installed.
When the manufacturer of Product Approved side wall,
horizontally vented, gas−fueled equipment does not pro-
vide the parts for venting the flue gases, but identifies ꢂspe-
cial venting systems," the following requirements shall be
satisfied by the manufacturer:
2 − APPROVED CARBON MONOXIDE DETECTORS.
Each carbon monoxide detector as required in accor-
dance with the above provisions shall comply with
NFPA 720 and be ANSI/UL 2034 listed and IAS certi-
fied.
1 − The referenced ꢂspecial venting system" instructions
shall be included with the appliance or equipment
installation instructions; and
2
The ꢂspecial venting systems" shall be Product Ap-
proved by the Board, and the instructions for that sys-
tem shall include a parts list and detailed installation
instructions.
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 above grade di-
rectly in line with the exhaust vent terminal for the hori-
zontally vented, gas−fueled heating appliance or
equipment. The sign shall read, in print size no less
than one−half (1/2) inch in size, ꢂGAS VENT DIRECT-
LY BELOW. KEEP CLEAR OF ALL OBSTRUC-
TIONS."
A copy of all installation instructions for all Product
Approved side wall, horizontally vented, gas−fueled
equipment, all venting instructions, all parts lists for
venting instructions, and/or all venting design instruc-
tions shall remain with the appliance or equipment at
the completion of the installation.
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