Lennox International Inc Furnace G27M User Manual

PRODUCT LITERATURE  
1999 Lennox Industries Inc.  
Dallas, Texas  
503,589M  
7/99  
Supersedes 9/98  
G27M  
SERIES  
GAS FURNACE  
RETAIN THESE INSTRUCTIONS  
FOR FUTURE REFERENCE  
Litho USA  
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 try to light any appliance.  
Extinguish any open flames.  
Do not store or use gasoline or other  
flammable vapors and liquids in the  
vicinity of this or any other appliance.  
Do not touch any electrical switch; do not  
use any phone in your building.  
Immediately call your gas supplier from a  
neighbor's phone. Follow the gas supplier's  
instructions.  
Installation and service must be perĆ  
formed by a qualified installer, serĆ  
vice agency or the gas supplier.  
If you cannot reach your gas supplier, call  
the fire department.  
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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  
critical for your safety and the satisfactory operation of the  
product. Lennox strongly recommends annual inĆ  
spection and maintenance of this appliance. Contact  
your independent Lennox dealer for an inspection by a  
qualified service technician.  
Important Directions  
1 - Keep the furnace area clear and free of combustible  
material, gasoline, and other flammable vapors and liqĆ  
uids. If installed in an insulated area, furnace must be  
kept free of insulating material. Insulating material may  
be combustible. Inspect furnace venting system to  
make sure it is in place, physically sound, and without  
holes, corrosion, or blockage. Inspect furnace return  
air duct connection to ensure duct is sealed to the furĆ  
nace 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.  
Lighting Information and Operation  
2 - DO NOT obstruct air flow to unit. Unit must receive an  
unobstructed flow of combustion and ventilating air.  
WARNING  
If you do not follow these instructions exactly, a fire  
or explosion may result causing property damage,  
personal injury or loss of life.  
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  
furnace, or any other gas appliance (ie., a water  
heater), is installed. When return air is drawn from a  
room, a negative pressure 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 combustion and  
the formation of carbon monoxide gas. This toxic gas  
might then be distributed throughout the house by  
the furnace duct system.  
BEFORE OPERATING 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.  
Use only your hand to turn the gas control knob. Never use  
tools. If the knob will not turn by hand, do not try to repair it,  
call a qualified service technician. Force or attempted repair  
may result in a fire or explosion.  
Placing Furnace Into Operation  
G27M furnaces are equipped with an electronic ignition  
system. Do not attempt to manually light burners on these  
furnaces. Each time the thermostat calls for heat, the  
burners will automatically light.  
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 presĆ  
sure and gas flow rate, adequate combustion air, and  
proper venting.  
Gas Valve Operation (Figure 2)  
1 - STOP! Read the safety information at the beginning  
of this section.  
2 - Set the thermostat to the lowest setting. See figure 1.  
THERMOSTATS  
WARNING  
Carbon monoxide gas is invisible, odorless, and  
toxic.  
Exposure to this gas can cause personal injury and even  
death to all occupants, including pets. Any item that is powĆ  
ered by or gives off heat from a combustion process (inĆ  
cluding 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 reasonĆ  
able retail prices. Contact your independent Lennox dealer  
for more details about this investment in your safety.  
FIGURE 1  
3 - Turn off all electrical power to the unit.  
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 access panel.  
Page 3  
 
6 - White Rodgers 36E Gas Valve - Turn knob on gas  
valve 180° either way to OFF. See figure 1.  
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 instructions.  
If you do not smell gas go to next step.  
When a single-stage thermostat is being used to control  
the operation of the G27M furnace, the unit can either opĆ  
erate on high fire (second stage) at all times or the unit can  
be made to start on low fire (first stage) and automatically  
switch to high fire (second stage) after a time delay, if the  
demand is not satisfied on low fire (first stage).  
WHITE RODGERS 36E SERIES GAS VALVE  
NOTE – For more details on available options and for unit  
adjustment, contact the Lennox Technical Support De-  
partment.  
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HI  
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Filters  
G27M series units are equipped with external filters  
which should be inspected monthly and replaced when  
necessary to assure proper furnace operation. See  
table 1 for filter sizes. Replacement filters used with  
G27M-60/75 units must have a minimum velocity ratĆ  
ing of 400 FPM. Replacement filters used with  
G27M-100/120 units requireaminimum velocity rating  
of 625 FPM. Figures 3, 4, and 5 show possible filter  
locations.  
GAS VALVE SHOWN IN OFF POSITION  
FIGURE 2  
8 - White Rodgers 36E Gas Valve - Turn knob on gas  
valve 180° either way to ON.  
9 - Replace the access panel.  
TABLE 1  
10 - Turn on all electrical power to to the unit.  
11 - Set the thermostat to desired setting.  
FILTER SIZE  
NOTE – When unit is initially started, steps 1 through 11  
may need to be repeated to purge air from gas line.  
UPFLOW  
DOWNFLOW  
MODEL NUMBER  
1 FILTER  
2 FILTERS  
12 - If the appliance will not operate, follow the instrucĆ  
tions Turning Off Gas to Unit" and call your service  
technician or gas supplier.  
G27M-45/60/75  
16 in. X 20 in. X 1 in. 16 in. X 20 in. X 1 in.  
G27M-100/120/140 20 in. X 20 in. X 1 in. 16 in. X 20 in. X 1 in.  
Turning Off Gas to Unit  
1 - Set the thermostat to the lowest setting.  
UPFLOW FURNACE BOTTOM RETURN AIR  
2 - Turn off all electrical power to the unit if service is to  
be performed.  
3 - Remove the access panel.  
4 - White Rodgers 36E Gas Valve - Turn knob on gas  
valve 180° either way to ON.  
5 - Replace access panel.  
Two–Stage Operation  
The G27M is a two-stage gas-fired furnace, which can be  
controlled by either a two-stage or single-stage room  
thermostat.  
The two-stage thermostat monitors the room temperature  
and sends a signal to the G27M furnace when the temperĆ  
ature falls below the desired setpoint. The furnace is then  
turned on at low fire (first stage). If the room temperatures  
continues to fall, the thermostat sends a signal to turn on  
the unit at high fire (second stage).  
FIGURE 3  
Page 4  
 
UPFLOW FURNACE SIDE RETURN AIR  
Burner Flame  
The G27M burner flame is not adjustable; however, the  
flame should be inspected at the beginning of each heatĆ  
ing season and burners should be cleaned, if necessary.  
Burner flame should be blue when burning natural gas.  
BURNER FLAME  
FLAME  
FLAME APPEARS BLUE IF  
BURNING NAT. GAS.  
HEAT  
EXCHANGER  
TUBE  
BURNER  
VEST  
PANEL  
FIGURE 4  
FIGURE 6  
DOWNFLOW FURNACE  
FILTERS IN PLENUM RACK  
Venting System Inspection  
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.  
Contact your Lennox dealer for a periodic unit inspection  
by a qualified service technician.  
Flame Rollout Safety Switches  
Your Lennox furnace is equipped with two flame roll-out  
safety switches which shut off the gas supply to the furĆ  
nace in case of heat exchanger blockage. If the furnace  
fails to operate due to the functioning of these safety  
switches, DO NOT attempt to place the furnace into opĆ  
eration. Contact a qualified service technician.  
Service Reminder  
FIGURE 5  
Call your Lennox service technician if unit is inoperative.  
Before calling, always check the following to be sure serĆ  
vice is required.  
Blower  
1 - Check that electrical disconnect switches are ON.  
2 - Are access panels securely in place?  
3 - Check room thermostat for proper setting.  
4 - Replace any blown fuses or reset circuit breakers.  
5 - Gas valve should be ON.  
Check and clean blower wheel for any debris. Blower moĆ  
tor is prelubricated for extended bearing life. No further luĆ  
brication is needed.  
6 - Air filter should not be plugged limiting air flow.  
7 - Is gas turned on at meter?  
WARNING  
8 - Is manual main shutĆoff valve open?  
Blower door 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.  
To keep your Lennox gas heating system in peak opĆ  
erating condition year after year, contact your indeĆ  
pendent Lennox dealer about a planned service proĆ  
gram.  
Page 5  
 
Safety Precautions  
Planned Service  
If you discover any of the following, shut down your  
unit, and contact an independent Lennox dealer for  
an inspection by a qualified technician.  
You should expect a service technician to check the folĆ  
lowing items during an annual inspection. Power to the  
unit must be shut off for the service technician's safety.  
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.  
S 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  
unfamiliar noises.  
Burners- Must be inspected for rust, dirt, or signs of waĆ  
ter.  
S If you smell any unusual odors, your unit may be operĆ  
ating improperly. For example, units can give off unfaĆ  
miliar odors if components are required to operate in  
abnormal conditions.  
Vent pipe - Must be inspected for signs of water, damĆ  
aged or sagging pipe, or disconnected joints.  
Unit appearance - Must be inspected for rust, dirt, signs  
of water, burnt or damaged wires, or components.  
Fan access door - Must be properly in place and provide  
a seal between the return air and the room where the furĆ  
nace is installed.  
S Look for visible signs of a malfunctioning unit. ExamĆ  
ples include unusual amounts of condensate on winĆ  
dows inside your house, visibly burnt components or  
unusual dirt or rust accumulations on the vent pipe or  
in the unit.  
S If you experience headache, nausea, fatigue, or dizziĆ  
ness, the cause could be exposure to carbon monoxĆ  
ide 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.  
Return air duct - Must be properly attached and provide  
an air seal to 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.  
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.  
Problems detected during the inspection may make it  
necessary 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 unĆ  
safe operation. For instance, items innocently stored next  
to the furnace may obstruct the combustion air supply.  
This could cause incomplete combustion and the producĆ  
tion of carbon monoxide gas.  
Page 6  
 

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