Lennox G40DF Series Guide

04/01
*2P0401*
504,322M
*P504322M*
G40DF(X)
SERIES
Litho U.S.A.
504,322M
4/2001
WHAT TO DO IF YOU SMELL GAS:
DDo not try to ight any app iance.
DDo not touch any e ectrica switch; do not use any
phone in your bui ding.
DImmediate y ca your gas supp ier from a neighbor's
phone. Fo ow the gas supp ier's instructions.
DIf you cannot reach your gas supp ier, ca the fire deĆ
partment.
DExtinguish any open f ames.
GAS FURNACE
Do not store or use gaso ine or other f amĆ
mab e vapors and iquids in the vicinity of
this or any other app iance.
Insta ation and service must be performed by
a qua ified insta er, service agency or the gas
supp ier.
E 2001 Lennox Industries Inc.
Dallas, Texas, USA

If the information in this manua is not fo owed
exact y, a fire or exp osion may resu t causing
property damage, persona injury or oss of
ife.
WARNING

age 2
G40DF(X) Parts Identification
FIGURE 1
DURALOKTM HEAT
EXCHANGER
ASSEMBLY
LOWER ACCESS
PANEL
BURNERS
BLOWER
MOTOR
GAS
MANIFOLD
CABINET
CONTROL BOX
GAS
VALVE
COMBUSTION AIR
PROVING
(PRESSURE) SWITCH
COMBUSTION AIR
INDUCER
BLOWER ACCESS
PANEL
FLUE
COLLAR
TOP CAP
SURELIGHTt
CONTROL BOARD
FLUE CHASE
WARNING
Product contains fiberg ass woo .
Disturbing the insu ation in this product during
insta ation, maintenance, or repair wi expose you
to fiberg ass woo . Breathing this may cause ung
cancer. (Fiberg ass woo is known to the State of Ca Ć
ifornia to cause cancer.)
Fiberg ass woo may a so cause respiratory, skin,
and eye irritation.
To reduce exposure to this substance or for further
information, consu t materia safety data sheets
avai ab e from address shown be ow, or contact your
supervisor.
Lennox Industries Inc.
P.O. Box 799900
Da as, TX 75379-9900
NOTE - This manual must be left with the equipment
user.
WARNING
Do not set thermostat be ow 60°F (16°C) in heating
mode. Setting thermostat be ow 60°F (16°C) reduces
the number of heating cyc es. Damage to the unit
may occur that is not covered by the warranty.
WARNING
If overheating occurs or if gas supp y fai s to shut off,
shut off the manua gas va ve to the app iance before
shutting off e ectrica supp y.
CAUTION
Before attempting to perform any service or mainteĆ
nance, turn the e ectrica power to unit OFF at the
disconnect switch.

age 3
WARNING
Do not use this furnace if any part has been under
water. Immediate y ca a qua ified service technician
to inspect the furnace and to rep ace any part of the
contro system and any gas contro which has been
under water.
IMPORTANT
Any additions, changes, or conversions required in
order for the app iance to satisfactori y meet the apĆ
p ication needs must be made by a Lennox service
technician using factory specified and approved
parts.
WARNING
Improper insta ation, adjustment, a teration, service
or maintenance can cause property damage, personĆ
a injury or oss of ife. Insta ation and service must
be performed by a qua ified insta er, service agency
or the gas supp ier.
Important Directions
1 - Keep the furnace area clear and free of combustible
material, gasoline, and other flammable vapors and
liquids. If it is installed in an insulated area, the furnace
must be kept free of insulating material. Insulating maĆ
terial may be combustible.
2 - DO NOT obstruct air flow to unit. Unit must receive an
unobstructed flow of combustion and ventilating air.
3 - DO NOT store chlorine or fluorine products near unit
or introduce these products into the combustion air.
These products can cause furnace corrosion.
4 - DO NOT draw return air from a room where this furĆ
nace, or any other gas app iance (ie., a water heatĆ
er), is insta ed. When return air is drawn from a room,
a negative pressure is created in the room. If a gas apĆ
pliance 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 combustion and the
formation of carbon monoxide gas. This toxic gas
might then be distributed throughout the house by the
furnace duct system.
WARNING
The b ower door and f ue chase must be secure y in
p ace when the b ower and burners are operating.
Gas fumes, which cou d contain carbon monoxide,
can be drawn into the iving space resu ting in perĆ
sona injury or death.
Your furnace is a gas app iance. It is critical that the gas
supplied to the unit be completely burned to avoid the proĆ
duction of carbon monoxide gas. Complete combustion of
the gas requires, but is not limited to, correct gas pressure
and gas flow rate, adequate combustion, air, and proper
venting.
WARNING
Carbon monoxide gas is invisib e, odor ess and
toxic.
Exposure to carbon monoxide gas can cause personal injuĆ
ry and even death to all occupants, including pets. Any item
that is powered by or gives off heat from a combustion proĆ
cess (including lawn mowers, automobiles, and fireplaces)
has the potential to produce carbon monoxide gas. Because
of this, Lennox recommends the use of a carbon monoxĆ
ide detector in your home, even if you do not own gas
app iances. When propane is used, Lennox also recomĆ
mends use of a propane detector. Reliable detectors are
available at reasonable retail prices. Contact your Lennox
dealer or propane supplier for more details about this inĆ
vestment in your safety.
Your furnace is designed to meet standards set by nationĆ
al agencies, and to operate safely when properly installed
and maintained. However, the unit's performance can be
greatly impacted by the individual installation and the opĆ
erating environment. It is your responsibility to ensure that
this appliance is maintained. roper maintenance is critiĆ
cal for your safety and the satisfactory operation of the
product. Lennox strong y recommends annua inĆ
spection and maintenance of this app iance. Contact
your Lennox dealer for an inspection by a qualified service
technician.
Lighting Information & Operation
WARNING
If you do not fo ow these instructions exact y, a fire
or exp osion may resu t causing property damage,
persona injury or death.
BEFORE LIGHTING smell all around the appliance area
for gas. Be sure to smell next to the floor because some gas
is heavier than air and will settle on the floor.

age 4
The gas valve on the G40DF(X) will be equipped with eiĆ
ther a gas control knob or lever. Use only your hand to turn
the gas control knob or push the gas lever. Never use
tools. If the knob or lever will not move by hand, do not try
to repair it. Call a qualified service technician. Force or atĆ
tempted repair may result in a fire or explosion.
P acing the G40DF(X) furnace into operation:
G40DF(X) units are equipped with a SureLightt ignition
system. Do not attempt to manually light burners on these
furnaces. Each time thermostat calls for heat, the burners
will automatically light. The ignitor does not get hot when
there is no call for heat on units with the SureLightt ignition
system.
Operating the Gas Va ve (Figures 3, 4 and 5)
1 - STOP! Read the safety information at the beginning of
this section.
2 - Set the thermostat to the lowest setting. See figure 2.
3 - Turn off all electrical power to the unit.
THERMOSTATS
FIGURE 2
4 - This furnace is equipped with an ignition device which
automatically lights the burners. Do not try to light the
burners by hand.
5 - Remove the lower access panel.
6 - White Rodgers 36E/36F Gas Valve - Switch gas
valve lever to OFF.
Honeywell VR8205 Gas Valve - Turn knob on gas
valve clockwise to OFF. Do not force. See figure
5.
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 instrucĆ
tions. If you do not smell gas go to next step.
8 - White Rodgers 36E/36F Gas Valve - Switch gas valve leĆ
ver to ON. See figure 3 for the White Rodgers 36E
valve and figure 4 for the White Rodgers 36F valve.
Honeywell VR8205 Gas Valve - Turn knob on gas valve
counterclockwise to ON. Do not force.
FIGURE 3
White Rodgers 36E Series Gas Va ve
GAS VALVE SHOWN IN OFF POSITION
Gas
Va ve
Lever
FIGURE 4
White Rodgers 36F Series Gas Va ve
GAS VALVE SHOWN IN OFF POSITION
Gas
Va ve
Lever
FIGURE 5
ON
OFF
Honeywe VR8205 Series Gas Va ve
GAS VALVE SHOWN IN OFF POSITION
Gas
Va ve Knob
9 - Replace the lower access panel.
10 - Turn on all electrical power to to the unit.
11 - Set the thermostat to desired setting.
OTE - When unit is initially started, steps 1 through 11
may need to be repeated to purge air from gas line.
12- If the appliance will not operate, follow the section
Turning Off Gas to the Unit" and call your service techĆ
nician or gas supplier.
Turning Off Gas to the Unit
1 - Set the thermostat to the lowest setting.
2 - Turn off all electrical power to the unit if service is to be
performed.
3 - Remove the lower access panel.

age 5
4 - White Rodgers 36E/36F Gas Valve - Switch gas
valve lever to OFF.
Honeywell VR8205 Gas Valve - Turn knob on gas
valve clockwise to OFF. Do not force.
5 - Replace the lower access panel.
Fi ters
This unit is not equipped with a filter or rack. A field-proĆ
vided high-velocity filter is required for the unit to operate
properly.
A filter must be in place whenever the unit is operating.
Seasona Inspections
A qualified service technician should inspect the complete
system each season (heating and cooling). The following
maintenance procedures should only be conducted by a
qualified service technician. Do not attempt to service
the unit in any way.
Venting System
WARNING
Asphyxiation Hazard
The exhaust vent for this furnace must be secure y
connected to the furnace f ue co ar at a times.
For your safety and to fu fi the terms of the imited
warranty, a qua ified service technician must annua Ć
y inspect this furnace and its vent system.
Annually (before heating season) inspect furnace venting
system, vent cap, heat exchanger, and burners for corroĆ
sion, deterioration, or deposits of debris. Remove any obĆ
structions.
Inspect the furnace venting system to make sure it is in
place, physically sound, and without holes, corrosion, or
blockage. Vent connector must be in correct position,
sloped upward and be physically sound without holes or
excessive corrosion.
Inspect the furnace return air duct connection to ensure
duct is sealed to the furnace and terminates outside the
space containing the furnace.
Inspect the physical support of the furnace to guarantee
that it is sound without sagging, cracks or gaps around
base and it maintains seal between base and support.
During a seasonal check the service technician will inspect
the indoor blower and the burner flames along with the
venting system.
B ower
Check blower wheel for any debris and clean, if necessary.
Blower motor is pre-lubricated for extended bearing life. No
further lubrication is needed.
Burner F ame
CAUTION
To ensure proper operation, a qua ified technician
shou d annua y check the burner f ame.
Service Reminder
Call your Lennox service technician if the unit will not operĆ
ate. Before calling, always check the following to be sure
service is required:
1 - Check that electrical disconnect switches are ON.
2 - Check room thermostat for proper setting.
3 - Replace any blown fuses or reset circuit breakers.
4 - Gas valve should be ON.
5 - Air filter should not be plugged, which will limit air flow.
6 - Is gas turned on at meter?
7 - Is manual main shut-off valve open?
Record the model and serial number of the furnace. These
numbers are on the unit nameplate, which is located below
the burners.
Serial Number __________________
Model Number __________________
Safety Precautions
If you discover any of the fo owing, shut down your
unit, and contact a Lennox dea er for an inspection by
a qua ified technician.
DIf you repeatedly hear any new or unfamiliar sounds
while your unit is operating, there may be a problem. For
example, poorly performing burners can produce unfaĆ
miliar noises.
DIf you smell any unusual odors, your unit may be operatĆ
ing improperly. For example, units can give off unfamilĆ
iar odors if components are required to operate in abĆ
normal conditions.
DLook for visible signs of a malfunctioning unit. Examples
include unusual amounts of condensate on windows inĆ
side your house, visibly burnt components or unusual
dirt or rust accumulations on the vent pipe or in the unit.
DIf you experience headache, nausea, fatigue, or dizziĆ
ness, the cause could be exposure to carbon monoxide
gas. This is often misdiagnosed as the flu because
symptoms are similar. If you suffer from flu-like sympĆ
toms that are exaggerated at home, but seem to subĆ
side while you are away from the house, exposure to
carbon monoxide could be the cause.
Your vigilance may pay off in early detection of a problem
before either personal injury or property damage occurs.
Do not hesitate to contact a qualified service technician as
an investment in your well being.

age 6
P anned Service
You should expect a service technician to check the followĆ
ing items during an annual inspection. ower to the unit
must be shut off for the service technician's safety.
Fresh air gri es and ouvers (on the unit and in the room
where the furnace is installed) - Must be open and unobĆ
structed to provide combustion air.
Burners - Must be inspected for rust, dirt, or signs of water.
Vent pipe - Must be inspected for signs of water, damaged
or sagging pipe, or disconnected joints.
Unit appearance - Must be inspected for rust, dirt, signs
of water, burnt or damaged wires, or components.
B ower access door - Must be properly in place and proĆ
vide a seal between the return air and the room where the
furnace is installed.
F ue chase - Must be properly installed and sealed beĆ
tween the top cap and blower deck during unit operation.
Return air duct - Must be properly attached and provide
an air seal to the unit.
Operating performance - Unit must be observed during
operation to monitor proper performance of the unit and the
vent system.
Combustion gases - Flue products must be analyzed and
compared to the unit specifications.
roblems detected during the inspection may make it necĆ
essary to temporarily shut down the furnace until the items
can be repaired or replaced.
Pay attention to your furnace. Situations can arise beĆ
tween annual furnace inspections 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 carĆ
bon monoxide gas.