Lennox LGH 036 Guide

See unit nameplate for manufacturer
and address.
507246-02
6/2019
Supersedes 7/2018
WARNING
FIRE OR EXPLOSION HAZARD
Failure to follow safety warnings
exactly could result in serious
injury, death, or property damage.
Do not store or use gasoline or other
ammable vapors and liquids in the
vicinity of this or any other appliance.
Installation and service must be per-
formed by a qualied installer, service
agency or the gas supplier.
• Do not try to light any appliance.
• Extinguish any open ames.
• Do not touch any electrical switch; do not use
any phone in your building.
• Leave the building immediatly
• Immediately call your gas supplier from a
neighbor’s phone. Follow the gas supplier’s in-
structions.
• If you cannot reach your gas supplier, call the
re department.
WHAT TO DO IF YOU SMELL GAS:
LGH036, 048, 060, 072, 074
(3, 4, 5 and 6 Tons)
LGH092, 094, 120, 122, 150, 152
(7-1/2, 8-1/2, 10 and 12-1/2 Tons)
LGH156, 180, 210, 240, 300S/U
(13, 15, 17-1/2, 20 and 25 Tons)
LGH242, 300H, 360
(20, 25 and 30 Tons)
ROOFTOP UNITS
USER’S INFORMATION MANUAL
FBR113270 READ ALL INSTRUCTIONS IN THIS MANUAL
AND RETAIN FOR FUTURE REFERENCE
©2019
Safety
1 - Keep unit area clear and free of combustible
materials, gasoline and other ammable vapors and
liquids.
2 - Do not obstruct air ow to unit. Unit must receive an
unobstructed ow of combustion and ventilating air.
WARNING
Danger of explosion and re. Failure to
follow safety warnings exactly could result in
dangerous operation, serious injury, death or
property damage.
CAUTION
As with any mechanical equipment, contact with sharp
sheet metal edges can result in personal injury. Take
care while handling this equipment and wear gloves and
protective clothing.
WARNING
Improper installation, adjustment, alteration, service
or maintenance can cause property damage, personal
injury or loss of life. Installation and service must be
performed by a licensed professional HVAC installer or
equivalent, service agency, or the gas supplier.
WARNING
Danger of electrical shock, explosion and
re. Improper servicing could result in
dangerous operation, serious inujry, death
or property damage.

Page 2507246-02 7/2018
LGH036, 048, 060S, H & 072, 074H Parts Arrangement
LGH092, 094, 102, 120, 122, 150 & 152 Parts Arrangement
EVAPORATOR
COIL
CONDENSER
FAN
CONDENSER
COIL
COMPRESSOR
CONDENSATE
DRAIN
FILTERS (4)
036, 048:16 X 20 X 2”
060, 072, 074: 20 X 20 X 2”
ECONOMIZER
(OPTIONAL)
GAS VALVE
BURNERS
COMBUSTION
AIR INDUCER
BLOWER
MOTOR
(BELT DRIVE SHOWN)
TXV
UNIT
CONTROLLER
REHEAT COIL
(OPTIONAL)
BLOWER
COIL
GUARDS
(OPTIONAL)
UNIT
CONTROLLER
EVAPORATOR
COIL
CONDENSER FANS
(2 ON 092, 102, 120, 150
UNITS; 3 ON 094, 122,
152 UNITS)CONDENSER
COILS
COMPRESSORS
CONDENSATE
DRAIN
FILTERS
(FOUR - 20 X 25 X 2”)
ECONOMIZER
(OPTIONAL)
BLOWER
BLOWER
MOTOR (BELT
DRIVE SHOWN)
GAS VALVE
BURNERS
COMBUSTION
AIR INDUCER
REHEAT COIL
(OPTIONAL)
DISCONNECT /
CIRCUIT BREAKER
(FACTORY OR FIELD
INSTALLED OPTION)
33
33
LL
EE
NN
OO
XX
NN
LL
EE
NN
OO
XX
NN
BLOWER

Page 3 507246-02 6/2019
LGH156, 180, 210, 240, 300S/U Parts Arrangement
LGH242, 300H, 360 Parts Arrangement
BLOWERS
EVAPORATOR
COIL
COMBUSTION
AIR INDUCER
CONDENSER FANS
(3 FANS ON 156 UNITS;
6 FANS ON 180U, 210,
240, & 300S/U UNITS
CONDENSER
COILS (RIGHT COIL
IS VERTICAL ON
156 UNITS)
COMPRESSORS
(4 ON 180U, 240 & 300S/U UNITS)
GAS VALVEBURNERS
BLOWER
MOTOR
CONDENSATE
DRAIN
FILTERS
(SIX - 24 X 24 X 2”)
ECONOMIZER
DAMPERS (OPTIONAL)
UNIT
CONTROLLER
DISCONNECT
(Factory-installed option)
BURNERS COMPRESSORS
COMBUSTION
AIR INDUCER
EVAPORATOR
COIL
BLOWER MOTOR
CONDENSER FANS
(6)
CONDENSER
COILS
HEAT
EXCHANGER TUBES
BLOWERS
CONDENSATE
DRAIN
FILTERS
(TWELVE - 20 X 20 X 2”)
ECONOMIZER
DAMPERS (OPTIONAL)
CONTROL BOX
115V GFCI OUTLET
(Factory-installed option)
DISCONNECT
(Factory-installed option)

Page 4507246-02 7/2018
CAUTION
Label all wires prior to disconnection when servicing
controls. Wiring errors can cause improper and
dangerous operation. Verify proper operation after
servicing.
WARNING
Electric shock hazard. Can cause injury or
death. Before attempting to perform any
service or maintenance, turn the electrical
power to unit OFF at disconnect switch(es).
Unit may have multiple power supplies.
WARNING
Do not use this furnace if any part has been under water.
A ood-damaged furnace is extremely dangerous.
Attempts to use the furnace can result in re or explosion.
A qualied service agency should be contacted to
inspect the furnace and to replace all gas controls,
control system parts, electrical parts that have been wet
or the furnace if deemed necessary.
WARNING
Danger of explosion. Can cause injury or
product or property damage. 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.
Unit Operation
FOR YOUR SAFETY READ BEFORE LIGHTING
BEFORE LIGHTING smell all around the furnace area for
gas. Be sure to smell next to the roof because some gas
is heavier than air and will settle on the roof.
The gas valve may be equipped with either a gas control
lever or gas control knob. Use only your hand to push the
lever or turn the gas control knob. Never use tools. If the
the lever will not move or the knob will not push in or turn
by hand, do not try to repair it. Call a qualied service
technician. Force or attempted repair may result in a re
or explosion.
The unit is equipped with an automatic spark ignition sys-
tem. There is no pilot. In case of a safety shutdown, move
thermostat switch to OFF and return the thermostat switch
to HEAT. For logic units and units with electronic tempera-
ture controls, shut off the main disconnect and then turn it
on to reset the ignition control.
Placing Unit Into Operation
WARNING
Danger of explosion and re. Can cause
injury or product or property damage. You
must follow these instructions exactly.
Gas Valve Operation
1 - Set thermostat to lowest setting.
2 - Turn off all electrical power to appliance.
3 - This appliance is equipped with an ignition device
which automatically lights the burner. Do not try to
light the burner by hand.
4 - Open the heat section access panel.
5 - Turn gas valve switch to OFF. See Figure 1, Figure
2, or Figure 3. On Honeywell VR8305Q gas valves,
turn knob on gas valve clockwise to OFF. Do
not force. See Figure 4.
6 - Wait ve (5) 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 the next step.
MANIFOLD
PRESSURE
OUTLET
GAS VALVE SWITCH SHOWN IN ON POSITION.
INLET
PRESSURE
PORT
MANIFOLD
PRESSURE
ADJUSTMENT
SCREW
HONEYWELL VR8215S GAS VALVE
Single-Stage
FIGURE 1

Page 5 507246-02 6/2019
WHITE RODGERS 36J54 GAS VALVE
Two-Stage
GAS VALVE SWITCH SHOWN IN OFF POSITION.
LOW FIRE
ADJUSTMENT
HIGH FIRE
ADJUSTMENT
INLET
PRESSURE
TAP
MANIFOLD
PRESSURE TAP
FIGURE 2
WHITE RODGERS 36H54 GAS VALVE
Two-Stage
LOW FIRE
ADJUSTMENT
HIGH FIRE
ADJUSTMENT
INLET
PRESSURE
TAP
MANIFOLD
PRESSURE
TAP
GAS VALVE SWITCH SHOWN IN ON POSITION.
FIGURE 3
HONEYWELL VR8305Q SERIES GAS VALVE
GAS VALVE KNOB IS SHOWN IN OFF POSITION.
LOW FIRE
ADJUSTMENT
HIGH FIRE
ADJUSTMENT
INLET
PRESSURE
TAP
MANIFOLD
PRESSURE
TAP
FIGURE 4
7 - Turn gas valve switch to ON. See Figure 1, Figure
2, or Figure 3. On Honeywell VR8305Q gas valves,
turn knob on gas valve counterclockwise to ON.
Do not force. See Figure 4.
8 - Close or replace the heat section access panel.
9 - Turn on all electrical power to appliance.
10 - Set thermostat to desired setting.
NOTE - When unit is initially started, steps 1 through 9
may need to be repeated to purge air from gas line.
11 - The ignition sequence will start.
12 - If the appliance does not light the rst time (gas
line not fully purged), it will attempt up to two more
ignitions before locking out.
13 - If lockout occurs, repeat steps 1 through 10.
14 - If the appliance will not operate, follow the
instructions “Turning Off Gas to Appliance” and call
your service technician or gas supplier.
Turning Off Gas to Unit
1 - If using an electromechanical thermostat, set to the
lowest setting.
2 - Before performing any service, turn off all electrical
power to the appliance.
3 - Open or remove the heat section access panel.
4 - Turn gas valve switch to OFF. On Honeywell
VR8305Q gas valves, turn knob on gas valve
clockwise to OFF. Do not force.
5 - Close or replace the heat section access panel.
WARNING
Danger of explosion. Can cause injury or
death. Do not attempt to light manually. Unit
has a direct spark ignition system.
Burner Flame
WARNING
Danger of explosion and re. Can cause
injury or product or property damage.
Periodically inspect burner ame to ensure
proper unit operation.
The primary air is permanently set for normal operation.
The ame will be basically blue with some clear yellow
streaking in the end of the ame. Inspect the burner ame
periodically during the heating season using the inspec-
tion port provided on the burner access panel.

Page 6507246-02 7/2018
Flue Passage and Vent Inspection
Annually, before heating season, inspect the combustion
air louvers, vent cap, heat exchanger, burners and com-
bustion air inducer for corrosion, deterioration or deposits
of debris. Remove any obstructions or blockage. See Fig-
ure 5, Figure 6, or Figure 7.
HEAT EXCHANGER ASSEMBLY
036-074 UNITS - Single- and Two-Stage Shown
BURNER
COMBUSTION
AIR INDUCER
VENT
CONNECTOR
GAS VALVE
HEAT
EXCHANGER
TUBE
PRIMARY
LIMIT
ROLLOUT
SWITCH
FLUE BOX
COVER
FIGURE 5
HEAT EXCHANGER ASSEMBLY
092-152 UNITS
BURNER
COMBUSTION
AIR INDUCER
VENT
CONNECTOR
GAS VALVE
HEAT
EXCHANGER
TUBE
FIGURE 6
HEAT EXCHANGER ASSEMBLY
156-360 UNITS
BURNER
COMBUSTION
AIR INDUCER
VENT
CONNECTOR
GAS VALVE
HEAT
EXCHANGER
TUBE
FIGURE 7
Service
To maintain efciency and longevity, your equipment
must be serviced yearly by a qualied service technician.
Failure to provide proof of service can void warranty.
CAUTION
Label all wires prior to disconnection when servicing
controls. Wiring errors can cause improper and dangerous
operation. Verify proper operation after servicing.
Servicing Filter
Units are equipped with lters as shown in Table 1.
Filters should be checked monthly and replaced when
necessary. Take note of air ow direction marking on
lter frame when reinstalling lters. See Figure 8.
NOTE - Replace factory-installed lters within 30 days
of initial unit start-up. Refer to local codes or appropriate
jurisdiction for approved lters.
WARNING
Units are shipped from the factory with temporary lters.
Replace lters before building is occupied. Damage to
unit could result if lters are not replaced with approved
lters. Refer to appropriate codes.
REMOVE FILTERS
PULL TO REMOVE
FILTERS
FIGURE 8

Page 7 507246-02 6/2019
to the unit and use the inspection port in the access
panel to check the ame.
BURNER BOX ASSEMBLY
036-074 UNITS - ONE- & TWO-STAGE
GAS
VALVE
GAS
MANIFOLD
FLAME
SENSOR
BURNERS
NOX INSERT
FIGURE 9
BURNER BOX ASSEMBLY
036-074U UNITS - FOUR-STAGE
GV1
GAS VALVE
GV3
GAS VALVE
GAS
MANIFOLD
BURNERS
FIGURE 10
BURNER BOX ASSEMBLY - 092-360 UNITS
GAS
MANIFOLD
GAS
VALVE
BURNERS
FIGURE 11
TABLE 1
UNIT FILTERS
Unit Qty Filter Size - inches (mm)
036, 048 4 16 X 20 X 2 (406 X 508 X 51)
060, 072, 074 4 20 X 20 X 2 (508 X 508 X 51)
092, 094, 102, 120,
122, 150, 152 420 X 25 X 2 (508 X 635 X 51)
156 - 300S/U 624 X 24 X 2 (610 X 610 X 51)
242, 300H, 360 12 20 X 20 X 2 (508 X 508 X 51)
NOTE - Filters must be ULC approved or equivalent for use in Canada.
Lubrication
All motors are lubricated at the factory. No further
lubrication is required.
156-360 Units -
Blower shaft bearings are prelubricated. For extended
bearing life, relubricate at least once every two years
with a lithium base grease, such as Alvania 3 (Shell Oil),
Chevron BRB2 (Standard Oil) or Regal AFB2 (Texas Oil).
Use a hand grease gun for relubrication. Add only enough
grease to purge through the bearings so that a bead of
grease appears at the seal lip contacts.
Manifold Pressures
Manifold pressures are shown in table 2. Refer to Figure 1,
Figure 2, or Figure 3, or Figure 4 to locate pressure ports.
TABLE 2
MANIFOLD PRESSURES in w.g.
Unit
Natural Gas Propane (LP) Gas
1st
Stage
± 0.2
2nd
Stage
± 0.3
1st
Stage
± 0.2
2nd
Stage
± 0.3
036, 048, 060, 072,
074 Std./High Heat NA 3.5 (0.87) NA 10.5 (2.61)
036, 048, 060, 072,
074 Dual Heat
2.0
(0.47)
3.5
(0.87)
5.9
(1.47)
10.5
(2.61)
092-360 1.6
(0.40)
3.7
(0.92)
5.5
(1.47)
10.5
(2.61)
Burners
Clean the burners as follows:
1 - Turn off the electrical power and the gas supply to
the unit.
2 - Remove the burner compartment access panel.
3 - Remove top burner box panel. See Figure 9, Figure
10, or “Figure 10” on page 7
4 - Remove screws securing burners to burner
support and lift the entire burner assembly from the
orices. Clean as necessary. Spark gap on ignition
electrode must be properly set. Refer to the Heating
Adjustment section in the installation instructions.
5 - Replace burners and screws securing burner.
Replace the top burner box panel.
6 - Turn on the electrical power and the gas supply to
the unit. Follow the operating instructions attached

Page 8507246-02 7/2018
Repair Parts Listing
When ordering repair parts, include the complete model number and serial number listed on the ETL/CSA rating plate -
e.g. LGH120H4BH1Y.
Gas Heat Section Parts
Heat Exchanger
Combustion Air Assembly
Combustion Air Proving Switch
Burner Assembly
Burner Manifold Assembly
Main Burner Orices
Flame Roll-out Switches
Auxiliary Limit Controls
Ignition Electrode Assembly
Ignition Lead
Ignition Sensor Assembly
Sensor Lead
Combination Gas Valve
Limit Controls
Cooling Parts
Compressors
Condenser Fan Motors
Condenser Fan Blades
Condenser Fan Run Capacitors
Freezestats
Condenser Fan Mounting Bracket
Fan Grille
Indoor Blower Motors
Blower Wheel
Expansion Valve
Distributor
Exhaust Fans (Opt.)
Electrical Control Parts
Unit Controller
Compressor Contactors
Circuit Breakers (Opt.)
Transformer (Control)
Transformer (Contactor)
Blower Contactor
Limit, Blower Relay
Heat Relays
Condenser Fan Relays
Capacitor CAB
Relay CAB
Disconnect Switch (Opt.)
Combustion Air Inducer
A combustion air inducer proving switch checks combus-
tion air inducer operation before allowing power to the gas
controller. The gas controller will not operate if the inducer
is obstructed.
Under normal operating conditions, the combustion
air inducer wheel should be checked and cleaned prior
to the heating season. However, it should be examined
periodically during the heating season to establish an
ideal cleaning schedule.
Clean the combustion air inducer as follows:
1 - Turn off the electrical power and the gas supply to
the unit.
2 - On 092-152 units, remove the tube bracket support
from the mullion on the right side of the heat section.
On 156-360 units, remove the mullion on the right
side of the heat section.
3 - Disconnect the pressure switch air tubing from the
combustion air inducer port.
4 - Remove and retain the screws securing the
combustion air inducer to the ue box.
5 - Remove and retain two screws from the bracket
supporting the vent connector before removing vent
connector. 024-152 units do not have a support
bracket. See Figure 7.
6 - Clean the inducer wheel blades with a small brush
and wipe off any dust from the housing. Clean
accumulated dust from the front of the ue box cover.
7 - Return the combustion air inducer motor and the
vent connector to their original location. Secure
with retained screws. It is recommended that the
combustion air inducer gasket be replaced during
reassembly.
8 - On 092-152 units, replace the tube bracket support.
On 156-360 units, replace mullion.
9 - Use a small brush to clean the combustion air inlet
louvers on the heat access panel.
Flue Passageway and Flue Box
1 - Remove the combustion air inducer assembly as
described in the Combustion Air Inducer subsection.
2 - Remove the ue box cover. Clean the ue box with
a wire brush as required.
3 - Clean the tubes with a wire brush.
4 - Reassemble the unit. The ue box cover gasket
and combustion air inducer gasket should also be
replaced during reassembly.
Service Reminder
Call a qualied service technician if the unit is inopera-
tive. Before calling, always check the following to be sure
service is required:
1 - Be sure 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 lters should not be plugged, limiting air ow.
6 - Make sure all access panels are in place.