2000 Lennox Industries Inc.
Dallas, Texas, USA
504,121M
5/2000
G50UH(X)
SERIES
GAS FURNACE
Litho U.S.A.
WARNING
If the information in this manual is not followed
exactly, a fire or explosion may result causing
property damage, personal injury or loss of
life.
WHAT TO DO IF YOU SMELL GAS:
Do not store or use gasoline or other flam-
mable vapors and liquids in the vicinity of
this or any other appliance.
Do not try to light any appliance.
Extinguish any open flames.
Do not touch any electrical switch; do not use any
phone in your building.
Installation and service must be performed by
a qualified installer, service agency or the gas
supplier.
Immediately call your gas supplier from a neighbor’s
phone. Follow the gas supplier’s instructions.
If you cannot reach your gas supplier, call the fire de-
partment.
05/00
504,121M
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Your furnace is a gas appliance. It is critical that the gas
supplied to the unit be completely burned to avoid the pro-
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
Do not use this furnace if any part has been under
water. Immediately call a qualified service technician
to inspect the furnace and to replace any part of the
control system and any gas control which has been
under water.
WARNING
IMPORTANT
Carbon monoxide gas is invisible, odorless, and
toxic.
Any additions, changes, or conversions required in
order for the appliance to satisfactorily meet the ap-
plication needs must be made by a Lennox service
technician using factory specified and approved
parts.
Exposure to carbon monoxide gas can cause personal inju-
ry and even death to all occupants, including pets. Any item
that is powered by, or gives off heat from, a combustion pro-
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 monox-
ide detector in your home, even if you do not own gas
appliances. Reliable detectors are available at reasonable
retail prices. Contact your Lennox dealer for more details
about this investment in your safety.
WARNING
Improper installation, adjustment, alteration, service
or maintenancecan cause property damage, person-
al injury or loss of life. Installation and service must
be performed by a qualified installer, service agency
or the gas supplier.
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 ma-
terial may be combustible.
Your furnace is designed to meet standards set by nation-
al agencies. It should operate safely when properly
installed and maintained. However, the unit’s perfor-
mance can be greatly impacted by the individual installa-
tion and the operating environment. It is your responsibil-
ity to ensure that this appliance is maintained. Proper
maintenance is critical for your safety and the satisfactory
operation of the product. Lennox strongly recommends
annual inspection and maintenance of this appliance.
Contact your Lennox dealer for an inspection by a quali-
fied service technician.
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 fur-
nace, or any other gas appliance (ie., a water heat-
er), is installed. When return air is drawn from a room,
a negative pressure is created in the room. If a gas ap-
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.
Lighting Information & Operation
WARNING
If you do not follow these instructions exactly, a fire
or explosion may result causing property damage,
personal injury or death.
WARNING
The blower door must be securely in place when the
blower and burners are operating. Gas fumes, which
could contain carbon monoxide, can be drawn into
the living space resulting in personal 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.
Page 3
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The gas valve on the G50UH(X) is equipped with either 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 attempted
repair may result in a fire or explosion.
White Rodgers 36E Series Gas Valve
MANIFOLD
PRESSURE
ADJUSTMENT
SCREW
MANIFOLD
PRESSURE
OUTLET
Placing the G50UH(X) furnace into operation:
G50UH(X) units are equipped with a SureLight ignition
system. Do not attempt to manually light burners on these
furnaces. Each time the thermostat calls for heat, the burn-
ers will automatically light. The ignitor does not get hot
when there is no call for heat on units with the SureLight
ignition system.
GAS VALVE SHOWN IN OFF POSITION
FIGURE 3
White Rodgers 36F Series Gas Valve
MANIFOLD
Operating the Gas Valve (Figures 3, 4 and 5)
PRESSURE
ADJUSTMENT
SCREW
1 - STOP! Read the safety information at the beginning of
this section.
MANIFOLD
PRESSURE
OUTLET
2 - Set the thermostat to the lowest setting. See figure 2.
3 - Turn off all electrical power to the unit.
THERMOSTATS
GAS VALVE SHOWN IN OFF POSITION
FIGURE 4
Honeywell VR8205 Series Gas Valve
MANIFOLD
MANIFOLD
PRESSURE
OUTLET
PRESSURE
ADJUSTMENT
SCREW
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.
ON
OFF
5 - Remove the upper access panel.
GAS VALVE SHOWN IN OFF POSITION
6 - White Rodgers 36E/36F Gas Valve - Switch gas
valve lever to OFF. See figure 3 for the White Rodg-
ers 36E valve and figure 4 for the White Rodgers
36F valve.
FIGURE 5
9 - Replace the upper access panel.
10 - Turn on all electrical power to to the unit.
11 - Set the thermostat to desired setting.
Honeywell VR8205 Gas Valve - Turn knob on gas
valve clockwise
5.
to OFF. Do not force. See figure
NOTE - When unit is initially started, steps 1 through 11
may need to be repeated to purge air from gas line.
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.
12 - If the appliance will not operate, follow the instructions
“Turning Off Gas to the Unit” and call your service tech-
nician or gas supplier.
Turning Off Gas to the Unit
8 - White Rodgers 36E/36F Gas Valve - Switch gas valve le-
ver to ON. See figure 3 for the White Rodgers 36E
valve and figure 4 for the White Rodgers 36F valve.
1 - Set the thermostat to the lowest setting.
2 - Turn off all electrical power to the unit if service is to be
performed.
Honeywell VR8205 Gas Valve - Turn knob on gas valve
counterclockwise
to ON. Do not force.
3 - Remove the upper access panel.
Page 4
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4 - White Rodgers 36E/36F Gas Valve - Switch gas
valve lever to OFF.
Burner Flame
Honeywell VR8205 Gas Valve - Turn knob on gas
CAUTION
To ensure proper operation, a qualified technician
should annually check the burner flame.
valve clockwise
to OFF. Do not force.
5 - Replace the upper access panel.
Filters
Service Reminder
This unit is not equipped with a filter or rack. A field-pro-
vided, high-velocity filter is required to ensure proper unit
operation.
Call your Lennox service technician if the unit will not oper-
ate. Before calling, always check the following to be sure
service is required.
A filter must be in place any time the unit is operating.
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.
Seasonal 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.
5 - Air filter should not be plugged, which wil 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.
Venting System
WARNING
Asphyxiation Hazard
Serial Number ________________________________
Model Number ________________________________
The exhaust vent for this furnace must be securely
connected to the furnace flue collar at all times.
For your safety and to fulfill the terms of the limited
warranty, a qualified service technician must annual-
ly inspect this furnace and its vent system.
Safety Precautions
If you discover any of the following, shut down your
unit and contact a Lennox dealer for an inspection by a
qualified technician.
Annually (before heating season) inspect furnace venting
system, vent cap, heat exchanger and burners for corro-
sion, deterioration, or deposits of debris. Remove any ob-
structions.
If 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 unfa-
miliar noises.
Inspect thefurnace venting system to make sure it is in
place, physically sound and without holes, corrosion, or
blockage. The vent connector must be correctly posi-
tioned and sloped upward. The vent connector must be
physically sound, without holes or excessive corrosion.
If you smell any unusual odors, your unit may be operat-
ing improperly. For example, units can give off unfamil-
iar odors if components are required to operate in ab-
normal conditions.
Inspect the furnace return air duct connection. The duct
must be sealed to the furnace and it must terminate outside
the space containing the furnace.
Look for visible signs of a malfunctioning unit. Examples
include unusual amounts of condensate on windows in-
side your house, visibly burnt components or unusual
dirt or rust accumulations on the vent pipe or in the unit.
Inspect the physical support of the furnace to guarantee
that it is sound. The support must not sag and must not
have cracks or gaps around the base of the furnace. There
must be a seal between the furnace base and the support.
If you experience headache, nausea, fatigue, or dizzi-
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 symp-
toms that are exaggerated at home, but seem to sub-
side while you are away from the house, exposure to
carbon monoxide could be the cause.
During a seasonal check, the service technician will in-
spect the indoor blower and the burner flames along with
the venting system.
Blower
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.
Check blower wheel for any debris and clean it, if neces-
sary. The blower motor is pre-lubricated for extended bear-
ing life. No further lubrication is needed.
Page 5
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Return air duct - Must be properly attached and provide
Planned Service
an air seal to the unit.
You should expect a service technician to check the follow-
ing items during an annual inspection. Power to the unit
must be shut off for the service technician’s 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, damaged
or sagging pipe, or disconnected joints.
Pay attention to your furnace. Situations can arise be-
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 car-
bon 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.
Page 6
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