Lennox G20 Series Guide

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PRODUCT LITERATURE
Litho U.S.A.
502,754M
9/98
Supersedes 4/95
¤ 1992 Lennox Industries Inc.
Dallas, Texas
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Installation and service must be per-
formed by a qualified installer, ser-
vice agency or the gas supplier.
-Do not try to light any 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.
-If you cannot reach your gas supplier, call
the fire department.
-Extinguish any open flames.
Do not store or use gasoline or other
flammable vapors and liquids in the
vicinityofthis orany other appliance.
If the information in this manual is not
followed exactly, a fire or explosion
may result causing property damage,
personal injury, or death.
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G20E / G20X PARTS IDENTIFICATION
HEAT
EXCHANGER
DRAFT
HOOD
UPPER ACCESS
PANEL
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BURNER
BOX
IGNITION
CONTROL
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GAS
MANIFOLD
BURNER BOX
DAMPER ASSEMBLY
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TOP STRIP
LIMIT
CONTROL
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ROLL-OUT
SWITCH
BLOCKED VENT
SHUT-OFF
SWITCH
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PILOT/ELECTRODE
ASSEMBLY
REMOVABLE
BURNER
BOX TOP

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WARNING
Product contains fiberglass wool.
Disturbing the insulation in this product during
installation, maintenance, orrepairwill expose you
to fiberglass wool. Breathing this may cause lung
cancer. (Fiberglass wool is known to the State of
California to cause cancer.)
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
WARNING
Do not use this furnace if any part has been under
water. Immediately call a qualified service techni-
cian to inspect the furnace and to replace any part
of the control system and any gas control which
has been under water.
WARNING
If overheating occurs or if gas supply fails to shut
off, shut off the manual gas valve to the appliance
before shutting off electrical supply.
IMPORTANT
Any additions, changes, or conversions required
in order for the appliance to satisfactory meet the
application needs must be made by a Lennox ser-
vice technician using factory specified and ap-
proved parts.
CAUTION
Before attempting to perform any service or main-
tenance, turn the electrical power to unit OFF at
disconnect switch.
IMPORTANT DIRECTIONS
1- Keep the furnace area clear and free of combustible
material, gasoline, andother flammable vapors andliq-
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 fur-
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.
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
furnace, or any other gas appliance (ie., a water
heater), is installed. When return air is drawn from
a room, anegative pressure is created inthe 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
andtheformationofcarbonmonoxidegas.Thistoxic
gas might then be distributed throughout the house
by the furnace duct system.
Yourfurnace isagasappliance. Itis critical that thegas
suppliedtotheunitbecompletely burnedtoavoidthepro-
duction of carbon monoxide gas. Complete combustion
of the gas requires, but is not limited to, correct gas pres-
sure and gas flow rate, adequate combustion, air, and
proper venting.
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 powered by or gives off heat from a combustion
process(includinglawnmowers,automobiles,andfire-
places) has the potential to produce carbon monoxide
gas. Because of this, Lennox recommends the use
of a carbon monoxide detector in your home, even
if you do not own gas appliances. Reliabledetectors
are available at reasonable retail prices. Contact your
independent Lennox dealer for more details about this
investment in your safety.
Your furnace isdesignedtomeet standardsset bynation-
alagencies,andtooperate safelywhenproperlyinstalled
and maintained. However, the unit’s performance can be
greatly impacted by the individual installation and the op-
erating environment. It is your responsibility to ensure
that this appliance is maintained. Proper maintenance is
criticalforyoursafety andthesatisfactoryoperationofthe

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product. Lennox strongly recommends annual in-
spection and maintenance of this appliance. Contact
your independent Lennox dealer for an inspection by a
qualified service technician.
LIGHTING INFORMATION AND OPERATION
WARNING
Ifyou donot follow theseinstructions exactly,afire
or explosion may result causing property damage,
personal injury or death.
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 onlyyour handto pushinor turn thegas control knob
or lever. Never use tools. If the knob or lever will not push
inorturnbyhand,donottry torepair it, calla qualifiedser-
vice technician. Force or attempted repair may result in a
fire or explosion.
To place G20E or G20X furnace into operation:
G20E or G20X units are equipped withan intermittent pi-
lot ignition system. Do not attempt to manually light pilots
on these furnaces. Each time thermostat calls for heat,
the pilot will automatically light. The pilot does not burn
when there is no call for heat on units with electronic igni-
tions.
Gas Valve Operation (Figures 3 and 4)
1- STOP! Read the safety information at the beginning
of this section.
2- Set thermostat to lowest setting. See figure 2.
THERMOSTATS
FIGURE 2
3- Turn off all electrical power to appliance.
4- This appliance is equipped with an ignition device
which automatically lights the pilot. Do not try tolight
the pilot by hand.
5- Remove control access panel.
6-
Honeywell VR8204 Gas Valve -Turnthe knobonthe
gas valve clockwise to OFF. See figure 3.
Robertshaw 7200 Gas Valve -Depress theleverand
move to OFF position. Do not force. See figure 4.
ON
OFF
FIGURE 3
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GAS VALVE SHOWN IN OFF POSITION
GAS VALVE
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ARM
IN OFF
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7- Wait five (5) minutes to clear out any gas. If youthen
smell gas, STOP! Immediately callyour gas supplier
from a neighbor’s phone. Follow the gas supplier’s
instructions. If you do not smell gas go to next step.
8-
Honeywell VR8204 Gas Valves - Turn the knob on
the gas valve counterclockwise to ON.
Robertshaw 7200 Gas Valve -Depress theleverand
move to ON position. Do not force.
9- Replace control access panel.
10- Turn on all electrical power to unit.
11- Set thermostat to desired setting.
NOTE-When unit is initially started, steps 1 through 11
may need to be repeated to purge air from pilot line.
12- If the furnace still will not operate, follow the instruc-
tions “To Turn Off Gas To Unit” and call your service
technician or gas supplier.
To Turn Off Gas To Unit
1- Set thermostat to lowest setting.
2- Turn off all electrical power to unit if service is to be
performed.
3- Remove control access panel.
4-
Honeywell VR8204 Gas Valves - Turn the knob on the
gas valve clockwise to OFF.
Robertshaw 7200 Gas Valve -D e press the lever and
move to OFF position. Do not force.
5- Replace control access panel.

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Filters
G20E and G20X series units are equipped with reusable
filters which should be inspected monthly and cleaned
when necessary to assure proper furnace operation. See
table 1 for filter sizes. Use the following procedure to
clean filter.
1- Turn off electric power to furnace.
2- Remove blower access panel. Wait for blower to stop.
3- Remove filter by sliding up and out of filter brackets.
4- Wash filter with water and a mild detergent. For in-
creased efficiency, filter media should be sprayed
withfilter Handicoater whendry.Filter Handicoateris
RP products no. 418 and is available as Lennox part
no. P-8-5069.
NOTE-If filter media must be replaced, order Lennox
part no.P-9-7831 for 20”x 25” filter, P-8-7822 for 16”
x 25” filter, 97H0601 for 18” x 25” filter, 97H0701 for
25” x25” filter, and 97H0801 for 24” x 30” filter.
5- Reinstall filter. Slide filter into top bracket and drop
into lower bracket.
NOTE-Do not replace reusable foam filters with
throw-away filters.
6- Replace blower access panel.
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Blower
Checkandcleanblowerwheelforanydebris. Blowermo-
torisprelubricatedforextendedbearin
g
life.Nofurtherlu-
brication is needed.
Pilot and Burner Flame
CAUTION
Check pilot flame and burner flame periodically to
ensure proper operation.
1-
Pilot Flame
-- Pilot flame must surround the end of
flame sensor for proper operation of pilot safety cir-
cuit. See fi
g
ure 7.
PILOT FLAME
(Side View)
BURNER
PILOT GAS
LINE ELECTRODE
(G20E & G20X)
FIGURE 7
FLAME SENSOR
2-
Burner Flame
-- Start burnerand allow to operate for
a few minutes to establish normal burnin
g
condi-
tions. Check burner flame by observation. Flame
should be predominantly blue in color, stron
g
in ap-
pearance and should rise directly from the burner
ports in the heat exchan
g
er. Check to see that flame
is burnin
g
from all continuous ribbon ports and that
flame does not impin
g
e on the sides of the heat ex-
chan
g
er. See fi
g
ure 8.
BURNER FLAME
FIGURE 8
NOTE-VIEW BURNER FLAME
THROUGH OBSERVATION PORT ON
BURNER BOX OR DAMPER OPENING
(Not Shown)
VENTING SYSTEM INSPECTION
Annually (before heatin
g
season)inspectfurnaceventin
g
system, draft hood, vent cap, heat exchan
g
er, burners
and pilot for corrosion, deterioration, or deposits of de-
bris. Remove any obstructions.
Contact your Lennox dealer for a periodic unit inspection
by a qualified service technician.
BLOCKED VENT SHUT-OFF SYSTEM
Your Lennox furnace is equipped with a blocked vent
shut-off switch and a flame roll-out switch. The blocked
ventshut-offswitchshutsoffthe
g
assupplytothefurnace
in the event of flue or vent blocka
g
e. The flame roll-out
switch shuts off the
g
as supply to the furnace if there is a

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blockage of the heat exchanger. If the furnace fails to op-
erate due to the functioning of either of these switches,
DONOT attempt toplacethefurnaceintooperation.Con-
tact a qualified service person.
SERVICE REMINDER
Call your Lennox service technician if unit is inoperative.
Before calling, always check the following to be sure ser-
vice is required.
1- Check to see 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 limiting air flow.
6- Is gas turned on at meter?
7- Is manual main shut-off valve open?
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To keep yourLennox gas heating system in peakoperat-
ing condition year after year, contact your independent
Lennox dealer about a planned service program.
If you discover any of the following, shut down your
unit, and contact an independent Lennox dealer for
an inspection by a qualified technician.
-
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.
-
If yousmell any unusual odors, your unit may beoper-
ating improperly. For example, units can give off unfa-
miliar odors if components are required to operate in
abnormal conditions.
-
Look for visible signs of a malfunctioning unit. Exam-
ples include unusual amounts of condensate on win-
dows inside your house, visibly burnt components or
unusual dirt or rust accumulations on the vent pipe or
in the unit.
-
If you experience headache, nausea, fatigue, or dizzi-
ness, the cause could be exposure to carbon monox-
idegas. This is oftenmisdiagnosed as the flubecause
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.
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.
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You should expect a service technician to check the fol-
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
unobstructed to provide combustion air.
Burners- Must be inspected for rust, dirt, or signs of water.
Vent pipe - Must be inspected for signs of water, dam-
aged or sagging pipe, or disconnected joints.
Unit appearance - Must be inspected for rust, dirt, signs
of water, burnt or damaged wires, or components.
Blower accessdoor - Must be properly inplace andpro-
videa sealbetween the return airandthe room wherethe
furnace is installed.
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.
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 be-
tween annual furnace inspections that may result in un-
safe operation.Forinstance, items innocently stored next
to the furnace may obstruct the combustion air supply.
This could causeincomplete combustion and theproduc-
tion of carbon monoxide gas.