Lennox F8AUH Series Guide

11999
45,000 to 120,000 Btuh (13.2 to 35.2 kW) Heating Capacity
1 through 5 Tons (3.5 to 17.6 kW) Add-On Cooling
F8AUH
Gas Furnaces – Up-Flow / Horizontal
User’s Information Manual
RETAIN THESE INSTRUCTIONS
FOR FUTURE REFERENCE
503,995M
06/99
Supersedes 05/99
Table of Contents
Important Directions 2. . . . . . . . . . . . . . . . . . . . . . . . . . . Venting System Inspection 5. . . . . . . . . . . . . . . . . . . . .
Lig ting Information and Operation 3. . . . . . . . . . . . . . Flame Rollout Safety Switc es 5. . . . . . . . . . . . . . . . . .
Filters 4. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Safety Reminder 5. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Blower 5. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Safety Precautions 5. . . . . . . . . . . . . . . . . . . . . . . . . . . .
Burner Flame 5. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Planned Service 6. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Model Number Identification
Additive Cooling (Nominal)
18 - 1.5 Ton ( kW)
24 - 2 Ton ( kW)
30 - 2.5 Ton ( kW)
36 - 3 Ton ( kW)
42 - 3.5 Ton ( kW)
48 - 4 Ton ( kW)
60 - 5 Ton ( kW)
Generation
AFUE
8 - 80%
9 - 90%
Furnace
Cabinet Color
L - Beige
G - Gray
B - Brown
R - Green
S - Silver
Door Color
L - Beige
G - Gray
B - Brown
R - Green
S - Silver
Btuh Input ( W)
045 - 45,000 (13.2)
060 - 60,000 (17.6)
075 - 75,000 (22.0)
100 - 100,000 (29.3)
120 - 120,000 (35.1)
NOTE - Shaded area denotes part of
model no. referenced in publication.
Gas Valve
2 - Two Stage Valve
Blank Ć Single Stage Valve
Blower Motor
V - Variable Speed Motor
Blank - MultiĆSpeed Motor
Options
X - Low NOx
P - LPG/Propane Gas
S - Stainless Steel Heat Exc anger
Z - Stainless Steel Heat Exc anger/Low NOx
Blank - No options
Configuration
UF - Up-Flow
DF - Down-Flow
HZ - Horizontal
MP- Multi-Position
DH- Downflow/Horizontal
UH- Up-Flow/Horizontal
V–24*F A8 *UH X–045 2
WHAT TO DO IF YOU SMELL GAS:
If the information in this manual is not
followed exactly, a fire or explosion
may result causing property damage,
personal injury or death.
WARNING
Do not store or use gasoline or othĆ
er flammable vapors and liquids in
the vicinity of this or any other apĆ
pliance.
Installation and service must be
performed by a qualified installer,
service 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 suppliĆ
er's instructions.
If you cannot reach your gas supplier, call
the fire department.
Extinguish any open flames.
FBR 113270

2
PARTS IDENTIFICATION
2
3
1 - COMBUSTION AIR
BLOWER
2 - PRESSURE SWITCH
3 - BURNERS
4 - HEAT EXCHANGER
5 - GAS VALVE
6 - CONTROL BOARD
7 - BLOWER
7
1
5
6
4
WARNING
Product contains fiberglass wool.Disturbing the
insulation in this product during installation,
maintenance, or repair will expose you to fiberĆ
glass wool. Breathing this may cause lung canĆ
cer. (Fiberglass wool is nown to the State of
California to cause cancer.)Fiberglass wool may
also cause respiratory, s in, 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
P.O. Box 799900
Dallas, TX 75379-9900
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.
WARNING
Do not use this furnace if any part has been underĆ
water. Immediately call a qualified service techniĆ
cian to inspect the furnace and to replace any part
of the control system and any gas control which
has been under water.
CAUTION
Before attempting to perform any service or mainteĆ
nance, turn the electrical power to unit OFF at disĆ
connect switch.
IMPORTANT
Any additions, changes, or conversions required in
order for the appliance to satisfactorily meet the apĆ
plication needs must be made by a qualified service
technician using factory specified and approved
parts.
Important Directions
1 - Keep t e furnace area clear and free of combustible
material, gasoline, and ot er 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, p ysically sound, and wit out
oles, corrosion, or blockage. Inspect furnace return
air duct connection to ensure duct is sealed to t e furĆ
nace and terminates outside t e space containing t e
furnace. Inspect t e p ysical support of t e furnace to
guarantee t at it is sound wit out sagging, cracks or
gaps around base and it maintains seal between base
and support.

3
2 - DO NOT obstruct air flow to unit. Unit must receive an
unobstructed flow of combustion and ventilating air.
3 - DO NOT store c lorine or fluorine products near unit or
introduce t ese products into t e combustion air.
T ese 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. W en return air is drawn from a
room, a negative pressure is created in t e room. If a
gas appliance is operating in a room wit negative
pressure, t e flue products can be pulled back down
t e vent pipe and into t e room. T is reverse flow of
t e flue gas may result in incomplete combustion and
t e formation of carbon monoxide gas. T is toxic gas
mig t t en be distributed t roug out t e ouse by
t e furnace duct system.
Your furnace is a gas appliance. It is critical t at t e gas
supplied to t e unit be completely burned to avoid t e proĆ
duction of carbon monoxide gas. Complete combustion
of t e gas requires, but is not limited to, correct gas presĆ
sure and gas flow rate, adequate combustion air, and
proper venting.
WARNING
Carbon monoxide gas is invisible, odorless, and
toxic.
Exposure to t is gas can cause personal injury and even
deat to all occupants, including pets. Any item t at is
powered by or gives off eat from a combustion process
(including lawn mowers, automobiles, and fireplaces) as
t e potential to produce carbon monoxide gas. Because
of t is, the use of a carbon monoxide detector in your
home is recommended, even if you do not own gas
appliances. Reliable detectors are available at reasonĆ
able retail prices. Contact your dealer for more details
about t is investment in your safety.
Your furnace is designed to meet standards set by nationĆ
al agencies, and to operate safely w en properly installed
and maintained. However, t e unit's performance can be
greatly impacted by t e individual installation and t e opĆ
erating environment. It is your responsibility to ensure
t at t is appliance is maintained. Proper maintenance is
critical for your safety and t e satisfactory operation of t e
product. Annual inspection and maintenance of this
appliance is strongly recommended. Contact your
dealer for an inspection by a qualified service tec nician.
Your furnace is designed to meet standards set by nationĆ
al agencies, and to operate safely w en properly installed
and maintained. However, t e unit's performance can be
greatly impacted by t e individual installation and t e opĆ
erating environment. It is your responsibility to ensure
t at t is appliance is maintained. Proper maintenance is
critical for your safety and t e satisfactory operation of t e
product. Annual inspection and maintenance of this
appliance is strongly recommended. Contact your
dealer for an inspection by a qualified service tec nician.
Lighting Information and Operation
WARNING
If you do not follow these instructions exactly, a fire
or explosion may result causing property damage,
personal injury or loss of life.
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
Use only your hand to push in or turn the gas control
knob Never use tools If the knob will not push in or 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:
F8AUH units are equipped with an electronic ignition
system Do not attempt to manually light burners on
these furnaces Each time thermostat calls for heat, the
burner will automatically light
Gas Valve Operation (See figures 2 and 3)
1 - STOP! Read t e safety information at t e beginning
of t is section.
2 - Set t ermostat to lowest setting. See figure 1.
THERMOSTATS
FIGURE 1
3 - Turn off all electrical power to appliance.
4 - T is appliance Is equipped wit an ignition device
w ic automatically lig ts t e burner. Do not try to
lig t t e burner by and.
5 - Remove control access panel.

4
6 - White Rodgers 36E Gas Valve - Switc gas valve lever
to OFF. do not force. See figure 2.
Honeywell VR8205 Gas Valve - Turn knob on gas valve
clockwise to OFF. Do not force. See figure 3.
WHITE RODGERS 36E SERIES GAS VALVE
GAS VALVE SHOWN IN OFF POSITION
FIGURE 2
ON
OFF
HONEYWELL VR8205 SERIES GAS VALVE
GAS VALVE SHOWN IN OFF POSITION
FIGURE 3
7 - Wait five (5) minutes to clear out any gas. If you t en
smell gas, STOP! Immediately call your gas supplier
from a neig bor's p one. Follow t e gas supplier's
instructions. If you do not smell gas go to next step.
8 - White Rodgers 36E Gas Valve - Switc gas valve lever
to ON. Do not force.
Honeywell VR8205 Gas Valve - Turn knob on gas
valve counterclockwise to ON. Do not force.
9 - Replace control access panel.
10 - Turn on all electrical power to unit.
11 - Set t ermostat to desired setting.
NOTE – When unit is initially started, steps 1 through 11
may need to be repeated to purge air from gas line.
12 - If t e appliance still will not operate, follow t e
instructions To Turn Off Gas To Unit" and call your
service tec nician or gas supplier.
To Turn Off Gas To Unit
1 - Set t ermostat to lowest setting.
2 - Turn off all electrical power to unit if service is to be
performed.
3 - Remove control access panel.
4 - Switc lever on W ite Rodgers gas valve to OFF; turn
knob on Honeywell valve clockwise to OFF. Do not
force.
5 - Replace control access panel.
Filters
All F8AUH filters must be installed external to t e unit.
T ey can be ordered as an optional accessory item.
Filters s ould be inspected mont ly. Clean or replace
t e filters w en necessary to ensure proper furnace
operation. See table 1 for filter sizes. Replacement filĆ
ters for F8AUH-045/060/075 units must ave a miniĆ
mum velocity rating of 400 FPM. Replacement filters
for F8AUH-100/120 units require a minimum velocity
rating of 625 FPM. Figures 4 and 5 show possible filter
locations
TABLE 1
Model Number Filter Size - inches (mm)
F8AUH-045/060/075 16 X 20 X 1 (406 X 508 X 25)
F8AUH-100/120 20 X 20 X 1 (508 X 508 X 25)
UPFLOW FURNACE
BOTTOM RETURN AIR
FIGURE 4

5
UPFLOW FURNACE
SIDE RETURN AIR
FIGURE 5
Blower
Check and clean blower wheel for any debris Blower
motor is prelubricated for extended bearing life No
further lubrication is needed
WARNING
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.
Burner Flame
The burner flame is not adjustable; however, the
flame should be inspected at the beginning of each
heating season and burners should be cleaned, if necĆ
essary Burner flame should be blue when burning
natural gas, blue/yellow when burning propane gas
BURNER FLAME
BURNER
FLAME
HEAT
EXCHANGER
TUBE
VEST
PANEL
FLAME APPEARS BLUE IF
BURNING NAT. GAS; BLUE/
YELLOW FOR PROPANE.
FIGURE 6
Venting System Inspection
Annually (before heating season) inspect furnace
venting system, vent cap, heat exchanger and burnĆ
ers for corrosion, deterioration, or deposits of debris
Remove any obstructions
Contact your dealer for a periodic unit inspection by a
qualified service technician
Flame Rollout Safety Switches
Your furnace is equipped with two flame roll-out safeĆ
ty switches which shut off the gas supply to the furĆ
nace in case of heat exchanger blockage If the furĆ
nace fails to operate due to the functioning of these
safety switches, DO NOT attempt to place the furnace
into operation Contact a qualified service technician
Safety Reminder
Call a qualified service technician if unit is inoperaĆ
tive Before calling, always check the following to be
sure service is required
1 - C eck t at electrical disconnect switc es are ON.
2 - Are access panels securely in place?
3 - C eck room t ermostat for proper setting.
4 - Replace any blown fuses or reset circuit breakers.
5 - Gas valve s ould be ON.
6 - Air filter s ould not be plugged limiting air flow.
7 - Is gas turned on at meter?
8 - Is manual main s utĆoff valve open?
To keep your gas heating system in peak operating
condition year after year, contact your dealer about a
planned service program
Safety Precautions
If you discover any of the following, shut down your
unit, and contact your dealer for an inspection by a
qualified technician.
SIf you repeatedly ear any new or unfamiliar sounds
w ile your unit is operating, t ere may be a problem.
For example, poorly performing burners can produce
unfamiliar noises.
SIf 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.
SLook for visible signs of a malfunctioning unit. ExamĆ
ples include unusual amounts of condensate on winĆ
dows inside your ouse, visibly burnt components or
unusual dirt or rust accumulations on t e vent pipe or
in t e unit.

6
SIf you experience eadac e, nausea, fatigue, or dizziĆ
ness, t e cause could be exposure to carbon monoxĆ
ide gas. T is is often misdiagnosed as t e flu because
symptoms are similar. If you suffer from flu-like sympĆ
toms t at are exaggerated at ome, but seem to subĆ
side w ile you are away from t e ouse, exposure to
carbon monoxide could be t e cause.
Your vigilance may pay off in early detection of a problem
before eit er personal injury or property damage occurs.
Do not esitate to contact a qualified service tec nician as
an investment in your well being.
Planned Service
You s ould expect a service tec nician to c eck t e folĆ
lowing items during an annual inspection. Power to t e
unit must be s ut off for t e service tec nician's safety.
Fresh air grilles and louvers (on t e unit and in t e room
w ere t e furnace is installed) - Must be open and unobĆ
structed to provide combustion air.
Burners- Must be inspected for rust, dirt, or signs of waĆ
ter.
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 t e return air and t e room w ere t e furĆ
nace is installed.
Return air duct - Must be properly attac ed and provide
an air seal to unit.
Operating performance - Unit must be observed during
operation to monitor proper performance of t e unit and
t e vent system.
Combustion gases - Flue products must be analyzed
and compared to t e unit specifications.
Problems detected during t e inspection may make it
necessary to temporarily s ut down t e furnace until t e
items can be repaired or replaced.
Pay attention to your furnace. Situations can arise beĆ
tween annual furnace inspections t at may result in unĆ
safe operation. For instance, items innocently stored next
to t e furnace may obstruct t e combustion air supply.
T is could cause incomplete combustion and t e producĆ
tion of carbon monoxide gas.