Lennox 99W41 User manual

Page 1
INSTALLATION INSTRUCTIONS FOR HEAT EXCHANGER REPLACEMENT KIT
USED ON LG/KG/ZG 036, 048, 060, 072, 074 PACKAGED ROOFTOP UNITS
507095-03
12/2020
Supersedes 507095-02
©2020
HEAT EXCHANGE
R
REPLACEMENT KIT
PACKAGED UNITS KITS
AND ACCESSORIES
Shipping and Packing List
Package 1 of 1 contains:
1- Heat exchanger assembly
1- Bag assembly containing:
22-Screws
1-CAB gasket
6-Seals (mastic)
5-Wire ties
1-Foam PVC tape (17” length)
Check packaging for shipping damage. Contact the last
carrier immediately if any shipping damage is found.
Application
See table for usage.
Cat. No. / Ass'y No. Heat Output
KBtuh Material
99W41 / 610414-01 150 Aluminized
99W42 / 610414-02 105/108 Aluminized
99W43 / 610414-03 65/70 Aluminized
10M86 / 610414-04 65/70 Stainless Steel
13J82 / 610414-05 105/108 Stainless Steel
13J83 / 610414-06 150 Stainless Steel
13U10 / 610414-07 108K NOX
ZG only Aluminum
16G31 / 610414-08 150K 4 Stg. Stainless Steel
WARNING
Improper installation, adjustment, alteration, ser
vice or maintenance can cause property damage,
personal injury or loss of life. Installation and ser
vice must be performed by a licensed professional
HVAC installer or equivalent, service agency, or the
gas supplier
CAUTION
As with any mechanical equipment, contact with
sharp sheet metal edges can result in personal in
jury. Take care while handling this equipment and
wear gloves and protective clothing.
LG/KG-Before Removing Heat Exchanger
Note - Do not damage roofing surface during
replacement.
1- Disconnect all electrical power to unit and turn off
main gas valve.
2- Disconnect power at the main breaker if the external
disconnect is installed on the gas inlet mullion.
3- Disconnect gas inlet pipe at gas valve.
4- Open or remove heat and compressor access
panels. See figure 1.
REMOVE PANELS - LG/KG
FIGURE 1
HEAT ACCESS
PANEL
COMPRESSOR
ACCESS PANEL
GAS INLET
MULLION
5- Remove the gas inlet mullion. See figure 1. If conduit
is run to the mullion, move the mullion out of the way.
Disconnect wiring and remove conduit if necessary.
6- Disconnect P19 from J19. See figure 2.
7- Disconnect wiring to ignitor, flame sensor,
combustion air blower prove switch, and flame rollout
switch. On LGH/KG/ZG units, disconnect wiring to
the primary limit. See figure 2. On LGM150 units,
remove the primary limit.
Note - Wires are marked for identification during
reassembly.
8- Remove the two screws securing the combustion air
blower prove switch. Discard the switch if tabs are
broken. Retain the switch for reassembly if tabs are
intact. See figure 2.
9- Disconnect the air tubing to the fitting on the
vestibule. See figure 3.

Page 2
DISCONNECT WIRING - LG/KG/ZG
FIGURE 2
COMPRESSOR
SECTION
HEAT SECTION
S18
COMBUSTION
AIR BLOWER
PROVE SWITCH
E1
SPARK
IGNITOR
FS1
FLAME
SENSOR
S47
FLAME
ROLLOUT
SWITCH
J19
P19
S10
PRIMARY LIMIT
LGH/KG/ZG
S10
PRIMARY LIMIT
LGM
10- Remove the burner box assembly. Retain six screws
holding the assembly in place. See figure 3.
11- Remove the vent connector from the combustion air
inducer. See figure 3.
12- Remove the combustion air inducer. See figure 3.
REMOVE BURNER BOX - LG/KG
FIGURE 3
BURNER
BOX
Remove screws secur
ing burner box; 3 on the
top, 3 on the bottom.
VENT
CONNECTOR
COMBUSTION
AIR INDUCER
COLLECTOR
COVER
AIR TUBING
PRESSURE
FITTING
VESTIBULE
13- Remove J19 from the division panel between the
heat and compressor sections. See figure 2.
14- Remove 11 screws securing heat exchanger.
Remove Heat Exchanger - LG/KG
Downflow Air Discharge Applications:
1- Remove the horizontal supply air panel.
2- Lift the back end of heat exchanger over the top of the
supports and slide exchanger slightly toward the front
of the unit. See figure 4.
3- Remove the heat exchanger from the front of the unit.
SIDE VIEW OF HEAT EXCHANGER - LG/KG
FIGURE 4
LIft the back end of the
heat exchanger over
supports to remove.
HEAT
EXCHANGER
SUPPORT
HEAT
EXCHANGER

Page 3
Horizontal Air Discharge - Direct Drive Blower:
1- LGH/KG Units -
Unplug the motor harness and remove 6 screws on
the base of the blower housing. See figure 6. Lift the
back side of the housing and remove from unit.
2- LGM Units -
Unplug the power and control harnesses to the motor.
Disconnect wiring to the pressure sensor located on
the blower housing. Remove four screws and slide
blower out of unit. See figure 5.
3- Remove the heat exchanger as shown in figure 4.
DIRECT DRIVE BLOWER REMOVAL - LGM
FIGURE 5
REMOVE TWO SCREWS
ON EACH SIDE TO SLIDE
BLOWER OUT OF UNIT
DIRECT DRIVE BLOWER REMOVAL - LGH/KG
FIGURE 6
REMOVE THREE
SCREWS ON EACH SIDE
TO SLIDE BLOWER OUT
OF UNIT
Horizontal Air Discharge - Belt Drive Blower:
1- Remove the belt.
2- Remove the motor mounting plate; do not remove the
motor from the mounting plate. See figure 7.
3- Remove six screws securing blower housing in place.
See figure 7. Pull the housing forward and tip the back
upward to remove from unit.
4- Lift the back side of the housing and remove from
unit.
5- Remove the heat exchanger as shown in figure 4.
BELT DRIVE BLOWER REMOVAL - LGH/KG
FIGURE 7
REMOVE SCREWS TO REMOVE
BLOWER MOTOR MOUNTING PLATE;
BLOWER REMAINS ATTACHED TO
THE MOUNTING PLATE
REMOVE TWO SCREWS ON EACH
SIDE TO REMOVE BLOWER HOUSING
BLOWER
HOUSING
BLOWER
MOTOR

Page 4
LG/KG - Install New Heat Exchanger
1- Install replacement heat exchanger. Lift the back of
the heat exchanger over the supports and push
toward the back of the unit. Make sure tubes are
secure in the support and the vestibule panel is tight
against the opening frame. Secure with 11 retained
screws.
2- Install the combustion air inducer gasket, provided in
this kit, and the previously removed combustion air
blower.
3- Reinstall vent connector.
4- LGH/KG Units -
Remove the two screws and patch plate covering the
primary limit opening and discard.
LGM Units -
Do NOT remove the patch plate. This plate must
be left in place.
5- Reinstall combustion air blower prove switch with
retained screws. If damaged, install a new
field-provided switch. Reinstall combustion air
inducer air tubing.
6- Reinstall burner box assembly.
7- Reinstall J19 in division panel and connect P19.
8- Reconnect all wires and secure away from other
components with wire ties. Reconnect all piping and
mullions.
9- Check for gas leaks at gas connections.
10- Start unit blower according to unit installation
instructions. Check for air leaks out of the gas heat
area. Use high temperature RTV or mastic seals to
seal any air leaking out of the gas heat compartment.
11- Start heating according to unit installation
instructions. Check for proper operation of gas heat
using lighting sequence provided in the unit
installation instructions or lighting instruction label
provided on unit.
12- In downflow applications remove the horizontal
return air panel. This will prevent a slight amount of
smoke from entering the building due to the residual
manufacturing process lubrication on the surface of
the heat exchanger. In horizontal airflow applications,
inform building occupants there may be a slight
amount of smoke entering the building.
13- Dispose of packing materials and replaced heat
exchanger properly.

Page 5
ZG - Remove Heat Exchanger
1- Turn main manual shut-off valve off and turn off
electrical supply to unit.
2- Open access panels as shown in figure 8.
IMPORTANT - Remove and retain the speed nut that
holds the heat exchanger bracket to the panel. The speed
nut will be used when replacing the bracket and panel.
3- Remove the gas manifold. See figure 9.
4- Remove the burner box assembly. Retain six screws
holding the assembly in place.See figure 9.
5- Disconnect wiring to the ignitor, flame sensor,
combustion air prove switch, flame roll-out switch and
primary limit. See figures 9 and 10.
6- Remove the primary limit. See figure 10.
7- Remove the vent connector from the combustion air
inducer. See figure 10.
8- Remove the combustion air inducer. See figure 10.
9- Remove screws securing heat exchanger to unit.
Rotate two parts on the front side of the frame and
remove heat exchanger. See figure 11.
Note - Take care not to tear insulation when removing or
installing heat exchanger.
FIGURE 8
REMOVE
PANEL
REMOVE
PANELS
SPEED
NUT
REMOVE PANELS - ZG
FIGURE 9
BURNER BOX ASSEMBLY - ZG
ORIFICES
(3, 5, OR 7)
Remove and retain two
screws on each side;
remove manifold.
GAS
VALVE
GAS
MANIFOLD
BURNERS
FLAME
SENSOR
IGNITOR
Remove screws securing
burner box; three on the
top, three on the bottom.

Page 6
ZG - Replace Heat Exchanger
1- Install the combustion air inducer gasket, provided in
this kit, and the previously removed combustion air
blower.
2- Set replacement heat exchanger in unit, rotate frame
front pieces in place and secure heat exchanger with
screws.
Note - Use an awl to line up screw holes. Install screws on
the back side of the assembly before the front side.
Tighten screws only after all screws are in place; this
allows a small amount of movement to assist starting all
screws.
3- Replace the burner box and secure in place with
screws.
Note - To make installation easier, start the screw on the
back, lower side of frame. Cut a slit in the back, lower
screw hole on the burner box. Set the burner box in place,
push down to force the slit over the partially-engaged
screw and tighten screw.
4- Replace gas manifold.
5- Reinstall vent connector.
6- Remove the two screws and patch plate covering the
primary limit opening and discard. Reinstall primary
limit.
7- Connect wiring to primary limit, ignitor and flame
sensor, gas valve, flame roll-out switch and
combustion air inducer.
8- Connect combustion air prove switch plastic tubing to
pressure port on heat exchanger vestibule.
9- Install heat exchanger support bracket and align hole
in panel with end of bracket. Fit panel in place and
secure bracket to the panel with retained speed nut.
10- Replace other panels and refer to unit installation
instructions to start unit.
11- Start unit blower according to unit installation
instructions. Check for air leaks out of the gas heat
exchanger compartment. Use high temperature RTV
or the mastic seals to seal any air leaking out of the
gas heat compartment.
12- Start unit in heating mode according to unit
installation instructions. Check for proper operation
of gas heat using lighting sequence provided in the
unit installation instructions or lighting instruction
label provided on unit.
13- On initial start-up, a slight amount of smoke may
enter the building due to the residual manufacturing
process lubrication on the surface of the heat
exchanger. In down flow applications, remove the
horizontal supply air panel to dilute the smoke. In
horizontal airflow applications, inform building
occupants there may be a slight amount of smoke
entering the building on initial start up.
14- Dispose of packing materials and replaced heat
exchanger properly.
FIGURE 10
BURNER
COMBUSTION
AIR INDUCER VENT
CONNECTOR
GAS VALVE PRIMARY LIMIT
LOCATION
COMBUSTION
AIR PROVE
SWITCH
PRESSURE
PORT
PLASTIC
TUBING
COLLECTOR
COVER
COMBUSTION AIR BLOWER ASSEMBLY - ZG

Page 7
ROTATE TWO PARTS OF THE FRAME
OUT OF THE WAY BEFORE REMOVING
OR INSTALLING HEAT EXCHANGER
FIGURE 11
HEAT SECTION - ZG