Lennox International Inc Furnace G50UHi User Manual

E 2003 Lennox Industries Inc.  
Dallas, Texas, USA  
504,650M  
07/03  
G50UHi  
SERIES  
GAS FURNACE  
Litho U.S.A.  
WARNING  
FIRE OR EXPLOSION HAZARD.  
Failure to follow safety warnings exactĆ  
ly could result in serious injury, death,  
or property damage.  
WHAT TO DO IF YOU SMELL GAS:  
Do not store or use gasoline or other  
flammable vapors and liquids in the  
vicinity of this or any other apĆ  
pliance.  
D Do not try to light any appliance.  
D Do not touch any electrical switch; do not  
use any phone in your building.  
D Leave the building immediately.  
D Immediately call your gas supplier from a  
neighbor's phone. Follow the gas supplier's  
instructions.  
Installation and service must be  
performed by a qualified installer,  
service agency or the gas supplier.  
D If you cannot reach your gas supplier, call  
the fire department.  
07/03  
504,650M  
*P504650M*  
*2P0703*  
 
WARNING  
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.  
Do not use this furnace if any part has been underĆ  
water. A flood-damaged furnace is extremely danĆ  
gerous. Attempts to use the furnace can result in  
fire or explosion. Immediately call a qualified serĆ  
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.  
Your furnace is a gas appliance. 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.  
IMPORTANT  
Any additions, changes, or conversions required in  
order for the appliance to satisfactorily meet the apĆ  
plication needs must be made by a Lennox service  
technician using factory specified and approved  
parts.  
WARNING  
Carbon monoxide gas is invisible, odorless 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  
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 maintenance can cause property damage, personĆ  
al injury or loss of life. Installation and service must  
be performed by a qualified installer, service agency  
or the gas supplier.  
Safety Instructions  
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.  
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. Proper maintenance is critiĆ  
cal for your safety and the satisfactory operation of the  
product. Lennox strongly recommends annual inĆ  
spection and maintenance of this appliance. Contact  
your Lennox dealer for an inspection by a qualified service  
technician.  
2 - DO NOT obstruct air flow to unit. Unit must receive an  
unobstructed flow of combustion and ventilating air.  
DO NOT block or obstruct air openings on the furnace  
or air openings to the area in which the furnace is  
installed. Take care to maintain established clearĆ  
ances surrounding the furnace.  
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 appliance (ie., a water heatĆ  
er), is installed. 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.  
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.  
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  
 
The gas valve on the G50UHi will be 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 G50UHi furnace into operation:  
®
G50UHi units are equipped with a SureLight ignition sysĆ  
tem. Do not attempt to manually light burners on these furĆ  
naces. Each time thermostat calls for heat, the burners will  
automatically light. The ignitor does not get hot when there  
GAS VALVE SHOWN IN OFF POSITION  
FIGURE 3  
®
White Rodgers 36F Series Gas Valve  
is no call for heat on units with the SureLight ignition sysĆ  
tem.  
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.  
GAS VALVE SHOWN IN OFF POSITION  
THERMOSTATS  
FIGURE 4  
Honeywell VR8205 Series Gas Valve  
MANIFOLD  
MANIFOLD  
PRESSURE  
OUTLET  
PRESSURE  
ADJUSTMENT  
SCREW  
FIGURE 2  
ON  
4 - This furnace is equipped with an ignition device which  
automatically lights the burners. Do not try to light the  
burners by hand.  
OFF  
GAS VALVE SHOWN IN OFF POSITION  
5 - Remove the upper access panel.  
FIGURE 5  
9 - Replace the upper access panel.  
6 - White Rodgers 36E/36F Gas Valve - Switch gas  
valve lever to OFF.  
Honeywell VR8205 Gas Valve - Turn knob on gas  
10 - Turn on all electrical power to to the unit.  
11 - Set the thermostat to desired setting.  
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 instrucĆ  
tions. If you do not smell gas go to next step.  
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  
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.  
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  
 
4 - White Rodgers 36E/36F Gas Valve - Switch gas  
valve lever to OFF.  
Honeywell VR8205 Gas Valve - Turn knob on gas  
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.  
valve clockwise  
to OFF. Do not force.  
5 - Replace the upper access panel.  
Inspect the furnace for obvious signs of deterioration.  
Filters  
Inspect the furnace venting system to make sure it is in  
place, physically sound, and without holes, corrosion, or  
blockage.  
All G50UHi filters are installed external to the unit. Filters  
should be inspected monthly. Clean or replace the filters  
when necessary to ensure proper furnace operation. ReĆ  
placement filters must be rated for high velocity airflow.  
Table 1 lists recommended filter sizes.  
Vent pipe must be clear and free of obstructions and must  
slope upward away from the furnace.  
Inspect the furnace return air duct connection to ensure  
duct is sealed to the furnace and terminates outside the  
space containing the furnace.  
A filter must be in place whenever the unit is operating.  
TABLE 1  
Filter Size  
Furnace  
Cabinet Size  
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.  
Side Return  
Bottom Return  
16 X 25 X 1 (1)  
20 X 25 X 1 (1)  
24 X 25 X 1 (1)  
17-1/2"  
21"  
16 X 25 X 1 (1)  
16 X 25 X 1 (1)  
16 X 25 X 1 (2)  
Inspect and clean the condensate trap and drain.  
24-1/2"  
During a seasonal check the service technician will inspect  
the indoor blower, burner flames and electrical connections  
along with the venting system.  
Maintenance  
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.  
Blower  
Check the blower wheel for debris and clean if necessary.  
The blower motors are prelubricated for extended bearing  
life. No further lubrication is needed.  
WARNING  
ELECTRICAL SHOCK, FIRE,  
OR EXPLOSION HAZARD.  
WARNING  
Failure to follow safety warnings exactly could result  
in dangerous operation, serious injury, death or  
property damage.  
Improper servicing could result in dangerous operaĆ  
tion, serious injury, death, or property damage.  
Before servicing, disconnect all electrical power to  
furnace.  
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 injuĆ  
ry or death.  
Burner Flame  
When servicing controls, label all wires prior to disĆ  
connecting. Take care to reconnect wires correctly.  
Verify proper operation after servicing.  
CAUTION  
To ensure proper operation, a qualified technician  
should annually check the burner flame.  
Venting System  
WARNING  
Electrical  
Asphyxiation Hazard  
1 - Check all wiring for loose connections.  
The exhaust vent for this furnace must be securely  
connected to the furnace flue collar at all times.  
2 - Check for the correct voltage at the furnace (furnace  
operating).  
For your safety and to fulfill the terms of the limited  
warranty, a qualified service technician must annualĆ  
ly inspect this furnace and its vent system.  
3 - Check amp-draw on the blower motor.  
Motor Nameplate__________Actual__________  
Page 5  
 
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.  
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:  
Planned Service  
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.  
You should expect a service technician to check the followĆ  
ing items during an annual inspection. Power to the unit  
must be shut off for the service technician's safety.  
5 - Air filter should not be plugged, which will limit air flow.  
6 - Is gas turned on at meter?  
Fresh air grilles and louvers (on the unit and in the room  
where the furnace is installed) - Must be open and unobĆ  
structed to provide combustion air.  
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 on the  
blower deck below the combustion air inducer.  
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.  
Serial Number __________________  
Model Number __________________  
Unit appearance - Must be inspected for rust, dirt, signs  
of water, burnt or damaged wires, or components.  
Safety Precautions  
Blower access door - Must be properly in place and proĆ  
vide a seal between the return air and the room where the  
furnace is installed.  
If you discover any of the following, shut down your  
unit, and contact a Lennox dealer for an inspection by  
a qualified technician.  
Return air duct - Must be properly attached and provide  
D 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 unfaĆ  
miliar noises.  
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.  
D If 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.  
Combustion gases - Flue products must be analyzed and  
compared to the unit specifications.  
D Look 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.  
Problems detected during the inspection may make it necĆ  
essary to temporarily shut down the furnace until the items  
can be repaired or replaced.  
D If 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.  
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.  
Page 6  
 
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: G50UHi-36A-070-1.  
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  
®
SureLight ignition board  
Main burner cluster  
Main burner orifices  
Pressure switch  
Ignitor  
Door interlock switch  
Circuit Breaker  
Blower Parts  
Blower control module  
Blower wheel  
Primary limit control  
Secondary limit  
Motor  
Flame rollout switch  
Motor mounting frame  
Motor capacitor  
Blower housing cutoff plate  
Page 7  
 

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