Lennox Merit Series User manual

Page 1
INSTALLATION
INSTRUCTIONS
ML180UHV
507945-01
01/2021
Superseds 08/2019
THIS MANUAL MUST BE LEFT WITH THE
HOMEOWNER FOR FUTURE REFERENCE
This is a safety alert symbol and should never be
ignored. When you see this symbol on labels or in man-
uals, be alert to the potential for personal injury or death.
IMPORTANT
DO NOT use the bracket securing the heat exchanger
to lift, drag or pull the furnace to its installation
location. Doing so will loosen the bracket causing
noise and or unsafe operation.
Bracket
© 2021 Lennox Industries Inc.
Dallas, Texas USA
MERIT® SERIES GAS FURNACE
HORIZONTAL AIR DISCHARGE
Contents
Unit Dimensions - inches (mm........................................2
ML180UHV Gas Furnace ...............................................3
Shipping and Packing List ..............................................3
Safety .............................................................................3
Use of Furnace as a Construction Heaterl .....................4
General...........................................................................4
Combustion, Dilution, Ventilation Air...............................5
Setting Equipment ..........................................................8
Filters............................................................................ 11
Duct System .................................................................12
Venting .........................................................................13
Gas Piping....................................................................20
Electrical.......................................................................22
Integrated Control.........................................................25
Unit Start-Up.................................................................29
Gas Pressure Measurement.........................................30
Proper Combustion.......................................................30
High Altitude .................................................................30
Other Unit Adjustments.................................................32
Service..........................................................................32
Blower Data..................................................................35
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.

Page 2
Unit Dimensions - inches (mm)
23
(584)
(19)
3/4
(19)
1Bottom Return
Air Opening
GAS PIPING INLET
(Either Side)
Side Return
Air Opening
(Either Side)
1
Bottom Return
Air Opening
FLUE OUTLET
(Top)
ELECTRICAL INLET
(Either Side)
SUPPLY AIR
OPENING
FRONT VIEW SIDE VIEW
TOP VIEW
A
B9/16 (14)
C
D
3/4
27-3/4
(705)
19-7/16
(494)
23-1/2
(597)
1-1/2
(38)
9-1/8 (232) Right
8-5/8 (219) Left
5-3/8 (137) Right
2-3/16 (56) Left
33
(838)
3-1/8 (79)
1-15/16 (49)
14
(356)
9/16
(14)
3 (76) Right
6-3/4 (171) Left
2
FLUE OUTLET
(Either Side)
3OPTIONAL
EXTERNAL
SIDE RETURN
AIR FILTER KIT
(Either Side)
16
(406)
14-3/4
(375)
3OPTIONAL
EXTERNAL
SIDE RETURN
AIR FILTER KIT
(Either Side)
2
Flue outlet may be horizontal but furnace must be
vented vertically
3
Optional External Side Return Air Filter Kit is not for use
with the optional Return Air Base.
1
NOTE - 60C size units that require air volumes over
1800 cfm must have one of the following:
1. Single side return air and Optional Return Air Base
with transition that must accommodate required
20 x 25 x 1 inch (508 x 635 x 25 mm) air filter to
maintain proper velocity.
2. Bottom return air.
3. Return air from both sides.
4. Bottom and one side return air.
See Blower Performance Tables for additional information.
3-1/4 (83)
5/8
(16)
1
3-1/4
(83)
23-3/4
(603)
25
(635)
3/4(19)
Front Panel
ELECTRICAL
INLET (Either Side)
ML180UHV
Model
A B C D
in mm in mm in mm in mm
030V36A
045V36A
070V36A
14-1/2 368 13-3/8 340 13 330 4-3/4 121
070V36B
070V48B
090V48B
17-1/2 446 16-3/8 416 16 406 6-1/4 159
110V60C 21 533 19-7/8 504 19-1/2 495 8 203

Page 3
ML180UHV Gas Furnace
The ML180UHV unit is shipped ready for installation in the
upow or horizontal right position (for horizontal left posi-
tion the combustion air pressure switch must be moved)
fueled by natural gas. A conversion kit (ordered separate-
ly) is required for use in LP/Propane gas applications. The
furnace is shipped with the bottom panel in place. The bot-
tom panel must be removed if the unit is to be installed in
a horizontal application. The panel may also be removed
in upow applications.
Shipping and Packing List
Package 1 of 1 contains
1 - Assembled ML180UHV unit
1 - Bag assembly containing the following:
2 - Screws
1 - Snap bushing
1 - Snap plug
1 - Wire tie
1 -Vent warning label
1 - Owner’s manual and warranty card
The following items may be ordered separately:
1 - Thermostat
1 - Suspension kit (for horizontal installations)
1 - LP/Propane changeover kit
1 - Return air base
1 - High altitude kit
1 - Side lter kit
Check equipment for shipping damage. If you nd any
damage, immediately contact the last carrier.
Safety Information
DANGER
Danger of explosion.
There are circumstances in which odorant used with
LP/propane gas can lose its scent. In case of a leak,
LP/propane gas will settle close to the oor and may
be di󰀩cult to smell. An LP/propane leak detector
should be installed in all LP applications.
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.
Certications
ML180UHV units are CSA International certied to ANSI
Z21.47.
In the USA, installation of gas furnaces must conform with
local building codes. In the absence of local codes, units
must be installed according to the current National Fuel
Gas Code (ANSI-Z223.1). The National Fuel Gas Code is
available from the following address:
American National Standards Institute, Inc.
11 West 42nd Street
New York, NY 10036
Clearances
Adequate clearance must be made around the air open-
ings into the vestibule area. In order to ensure proper unit
operation, combustion and ventilation air supply must be
provided according to the current National Fuel Gas Code.
Vent installations must be consistent with the National Fu-
elGas Code venting tables (in this instruction) and appli
cable provisions of local building codes.
This furnace is CSA International certied for installation
clearances to combustible material as listed on the unit
nameplate and in the tables in gures 7 and 11. Accessi-
bility and service clearances must take precedence over
re protection clearances.
NOTE - For installation on combustible oors, the furnace
shall not be installed directly on carpeting, tile, or other
combustible material other than wood ooring.
Installed Locations
For installation in a residential garage, the furnace must
be installed so that the burner(s) and the ignition source
are located no less than 18 inches (457 mm) above the
oor. The furnace must be located or protected to avoid
physical damage by vehicles. When a furnace is installed
in a public garage, hangar, or other building that has a
hazardous atmosphere, the furnace must be installed ac-
cording to recommended good practice requirements and
current National Fuel Gas Code.
Temperature Rise
NOTE - Furnace must be adjusted to obtain a tempera-
ture rise within the range specied on the unit nameplate.
Failure to do so may cause erratic limit operation and may
result in premature heat exchanger failure.
This ML180UHV furnace must be installed so that its elec-
trical components are protected from water.
Installed in Combination with a Cooling Coil
When this furnace is used with cooling units, it shall be in-
stalled in parallel with, or on the upstream side of, cooling
units to avoid condensation in the heating compartment.
See gure 1.

Page 4
With a parallel ow arrangement, a damper (or other
means to control the ow of air) must adequately prePage
4 vent chilled air from entering the furnace. If the damper
is manually operated, it must be equipped to prevent op-
eration of either the heating or the cooling unit, unless it is
in the full HEAT or COOL setting. See gure 1.
Gas Unit
Heating Unit Installed Upstream of Cooling Unit
Gas Unit
Dampers
(open during heating operation only)
Dampers
(open during cooling operation only)
Heating Unit Installed Parallell to Air Handler Unit
Air Handler Unit
Evaporator
FIGURE 1
When installed, this furnace must be electrically grounded
according to local codes. In addition, in the United States,
installation must conform with the current National Elec-
tric Code, ANSI/NFPA No. 70. The National Electric Code
(ANSI/NFPA No. 70) is available from the following ad-
dress:
National Fire Protection Association
1 Battery March Park
Quincy, MA 02269
NOTE - This furnace is designed for a minimum continu-
ous return air temperature of 60°F (16°C) or an intermittent
operation down to 55°F (13°C) dry bulb for cases where a
night setback thermostat is used. Return air temperature
must not exceed 85°F (29°C) dry bulb.
The ML180UHV furnace may be installed in alcoves, clos-
ets, attics, basements, garages, crawl spaces and utility
rooms in the upow or horizontal position.
This furnace design has not been CSA International
certied for installation in mobile homes, recreational
vehicles, or outdoors.
Use of Furnace as Construction Heater
Lennox does not recommend the use of ML180UHV units
as a construction heater during any phase of construc-
tion. Very low return air temperatures, harmful vapors and
operation of the unit with clogged or misplaced lters will
damage the unit.
ML180UHV units may be used for heating of buildings or
structures under construction, if the following conditions
are met:
• The vent system must be permanently installed per
these installation instructions.
• A room thermostat must control the furnace. The
use of xed jumpers that will provide continuous
heating is not allowed.
• The return air duct must be provided and sealed to
the furnace.
• Return air temperature range between 60°F (16°C)
and 80°F (27°C) must be maintained.
• Air lters must be installed in the system and must
be maintained during construction.
• Air lters must be replaced upon construction com-
pletion.
• The input rate and temperature rise must be set per
the furnace rating plate.
• One hundred percent (100%) outdoor air must be
provided for combustion air requirements during
construction. Temporary ducting may supply out-
door air to the furnace. Do not connect duct directly
to the furnace. Size the temporary duct following
these instructions in section for Combustion, Dilu-
tion and Ventilation Air in a conned space with air
from outside.
• The furnace heat exchanger, components, duct
system, air lters and evaporator coils must be
thoroughly cleaned following nal construction
clean-up.
• All furnace operating conditions (including ignition,
input rate, temperature rise and venting) must be
veried according to these installation instructions.
General
These instructions are intended as a general guide and
do not supersede local codes in any way. Consult author-
ities having jurisdiction before installation. In addition to
the requirements outlined previously, the following general
recommendations must be considered when installing a
ML180UHV furnace:
• Place the furnace as close to the center of the air
distribution system as possible. The furnace should
also be located close to the chimney or vent termi-
nation point.

Page 5
• Do not install the furnace where drafts might blow
directly into it. This could cause improper combus-
tion and unsafe operation.
• Do not block the furnace combustion air openings
with clothing, boxes, doors, etc. Air is needed for
proper combustion and safe unit operation.
• When the furnace is installed in an attic or other
insulated space, keep insulation away from the fur-
nace.
NOTE - The Commonwealth of Massachusetts
stipulates these additional requirements:
• Gas furnaces shall be installed by a licensed
plumber or tter only.
• The gas cock must be “T handle” type.
• When a furnace is installed in an attic, the pas-
sageway to and service area surrounding the
equipment shall be oored.
Combustion, Dilution & Ventilation Air
In the past, there was no problem in bringing in su󰀩cient
outdoor air for combustion. Inltration provided all the air
that was needed. In today’s homes, tight construction
practices make it necessary to bring in air from outside for
combustion. Take into account that exhaust fans, appli-
ance vents, chimneys, and replaces force additional air
that could be used for combustion out of the house. Un-
less outside air is brought into the house for combustion,
negative pressure (outside pressure is greater than inside
pressure) will build to the point that a downdraft can oc-
cur in the furnace vent pipe or chimney. As a result, com-
bustion gases enter the living space creating a potentially
dangerous situation.
In the absence of local codes concerning air for combus-
tion and ventilation, use the guidelines and procedures in
this section to install ML180UHE furnaces to ensure e󰀩-
cient and safe operation. You must consider combustion
air needs and requirements for exhaust vents. A portion of
this information has been reprinted with permission from
the National Fuel Gas Code (ANSI-Z223.1). This reprint-
ed material is not the complete and o󰀩cial position of the
ANSI on the referenced subject, which is represented only
by the standard in its entirety.
CAUTION
Do not install the furnace in a corrosive or
contaminated atmosphere. Meet all combustion
and ventilation air requirements, as well as all local
codes.
CAUTION
Insu󰀩cient combustion air can cause headaches,
nausea, dizziness or asphyxiation. It will also cause
excess water in the heat exchanger resulting in
rusting and premature heat exchanger failure.
Excessive exposure to contaminated combustion
air will result in safety and performance related
problems. Avoid exposure to the following
substances in the combustion air supply:
Permanent wave solutions
Chlorinated waxes and cleaners
Chlorine base swimming pool chemicals
Water softening chemicals
De-icing salts or chemicals
Carbon tetrachloride
Halogen type refrigerants
Cleaning solvents (such as perchloroethylene)
Printing inks, paint removers, varnishes, etc.
Hydrochloric acid
Cements and glues
Antistatic fabric softeners for clothes dryers
Masonry acid washing materials
In addition to providing combustion air, fresh outdoor air
dilutes contaminants in the indoor air. These contaminants
may include bleaches, adhesives, detergents, solvents
and other contaminants which can corrode furnace com-
ponents.
The requirements for providing air for combustion and
ventilation depend largely on whether the furnace is in-
stalled in an unconned or a conned space
Unconned Space
An unconned space is an area such as a basement or
large equipment room with a volume greater than 50 cubic
feet (1.42 m3) per 1,000 Btu (.29 kW) per hour of the com-
bined input rating of all appliances installed in that space.
This space also includes adjacent rooms which are not
separated by a door. Though an area may appear to be
unconned, it might be necessary to bring in outdoor air
for combustion if the structure does not provide enough air
by inltration. If the furnace is located in a building of tight
construction with weather stripping and caulking around
the windows and doors, follow the procedures in the air
from outside section.

Page 6
Conned Space
A conned space is an area with a volume less than 50
cubic feet (1.42 m3) per 1,000 Btu (.29 kW) per hour of
the combined input rating of all appliances installed in that
space. This denition includes furnace closets or small
equipment rooms.
When the furnace is installed so that supply ducts carry
air circulated by the furnace to areas outside the space
containing the furnace, the return air must be handled by
ducts which are sealed to the furnace casing and which
terminate outside the space containing the furnace.
This is especially important when the furnace is mounted
on a platform in a conned space such as a closet or small
equipment room. Even a small leak around the base of
the unit at the platform or at the return air duct connection
can cause a potentially dangerous negative pressure con-
dition. Air for combustion and ventilation can be brought
into the conned space either from inside the building or
from outside.
EQUIPMENT IN CONFINED
SP
ACE ALL AIR FROM INSIDE
CHIMNEY
OR GAS
VENT
FURNACE
WATER
HEATER
OPENINGS
(To Adjacent
Room)
NOTE - Each opening shall have a free area of at least one square
inch (645 mm2
ing of all equipment in the enclosure, but not less than 100 square
inches (64516 mm2).
AIR FLOW
FIGURE 2
Air from Inside
f the conned space that houses the furnace adjoins a
space categorized as unconned, air can be brought in
by providing two permanent openings between the two
spaces.
Each opening must have a minimum free area of 1 square
inch (645 mm2) per 1,000 Btu (.29 kW) per hour of total in-
put rating of all gas-red equipment in the conned space.
Each opening must be at least 100 square inches (64516
mm2). One opening shall be within 12 inches (305 mm) of
the top of the enclosure and one opening within 12 inches
(305 mm) of the bottom. See gure 2.
Air from Outside
If air from outside is brought in for combustion and ventila-
tion, the conned space must have two permanent open-
ings. One opening shall be within 12 inches (305 mm) of
the top of the enclosure and one opening within 12 inches
(305 mm) of the bottom. These openings must communi-
cate directly or by ducts with the outdoors or spaces (crawl
or attic) that freely communicate with the outdoors or in-
directly through vertical ducts. Each opening shall have a
minimum free area of 1 square inch (645 mm2) per 4,000
Btu (1.17 kW) per hour of total input rating of all equipment
in the enclosure. See gures 3 and 4. When communi-
cating with the outdoors through horizontal ducts, each
opening shall have a minimum free area of 1 square inch
(645 mm2) per 2,000 Btu (.56 kW) per total input rating of
all equipment in the enclosure. See gure 5.
When ducts are used, they shall be of the same cross-sec-
tional area as the free area of the openings to which they
connect. The minimum dimension of rectangular air ducts
shall be no less than 3 inches (75 mm). In calculating free
area, the blocking e󰀨ect of louvers, grilles, or screens
must be considered. If the design and free area of protec-
tive covering is not known for calculating the size opening
required, it may be assumed that wood louvers will have
20 to 25 percent free area and metal louvers and grilles
will have 60 to 75 percent free area. Louvers and grilles
must be xed in the open position or interlocked with the
equipment so that they are opened automatically during
equipment operation

Page 7
EQUIPMENT IN CONFINED SPACE
ALL AIR FROM OUTSIDE
(Inlet Air from Crawlspace and Outlet Air to Ventilated Attic)
NOTE-The inlet and outlet air openings shall each have a free area of at least one square inch (645
mm
2
)per 4,000 Btu (1.17 kW) per hour of the total input rating of all equipment in the enclosure.
VENTILATION LOUVERS
(Each end of attic)
OUTLET
AIR WATER
HEATER
INLET
AIR
CHIMNEY OR
GAS VENT
FURNACE
VENTILATION
LOUVERS
(For unheated crawl space)
AIR FLOW
FIGURE 3
EQUIPMENT IN CONFINED SPACE
ALL AIR FROM OUTSIDE
(All Air Through Ventilated Attic)
NOTE-The inlet and outlet air openings shall each have a
free area of at least one square inch (645 mm2) per 4,000
ment in the enclosure.
CHIMNEY
OR GAS
VENT
WATER
HEATER
OUTLET
AIR
VENTILATION LOUVER
S
(Each end of attic)
INLET AIR
(Ends 12 in.
above bottom)
FURNACE
AIR FLOW
FIGURE 4
EQUIPMENT IN
CONFINED SP
ACE
ALL AIR FROM
OUTSIDE
OUTLET AIR
INLET AIR
WATER
HEATER
CHIMNEY
OR GAS
VENT
NOTE - Each air duct opening shall have a free area of at least
one square inch (645 mm2) per 2,000 Btu (.59 kW) per hour of
the total input rating of all equipment in the enclosure. If the
equipment room is located against an outside wall and the air
openings
ing shall have a free area of at least one square inch (645 mm2)
per 4,000 Btu (1.17 kW) per hour of the total input rating of all
other equipment in the enclosure.
FURNACE
AIR FLOW
FIGURE 5

Page 8
Setting Equipment
WARNING
Do not install the furnace on its front or its back. Do
not connect the return air ducts to the back of the
furnace. Doing so will adversely a󰀨ect the operation
of the safety control devices, which could result in
personal injury or death.
The ML180UHV gas furnace can be installed as shipped
in either the upow position or the horizontal position.
Select a location that allows for the required clearances
that are listed on the unit nameplate. Also consider gas
supply connections, electrical supply, vent connection,
and installation and service clearances [24 inches (610
mm) at unit front]. The unit must be level.
NOTE - Units with 1/2 hp blower motors are equipped with
three exible legs and one rigid leg. See gure 6. The rigid
leg is equipped with a shipping bolt and a at white plastic
washer (rather than the rubber mounting grommet used
with a exible mounting leg). The bolt and washer must
be removed before the furnace is placed into opera-
tion. After the bolt and washer have been removed, the
rigid leg will not touch the blower housing.
RIGID LEG
remove shipping bolt and washe
Units with 1/2 or 3/4 HP Blower Motor
FIGURE 6
Upow Applications
Allow for clearances to combustible materials as indicated
on the unit nameplate. Minimum clearances for closet or
alcove installations are shown in gure 7.
Upflow Application Installation Clearances
Top
Bottom
Left Side Right Side
Type of Vent
Connector Type CType B1
Top1 in. (25 mm)1 in. (25 mm)
*Front 2-1/4 in. (57 mm)** 2-1/4 in. (57 mm)
Back 0 0
Sides 0†0
Vent 6 in. (152 mm)1 in. (25 mm)
Floor 0‡0‡
*Front clearance in alcove installation must be 24 in. (610 mm).
Maintain a minimum of 24 in. (610 mm) for front service access.
** 4-1/2 in. if single wall vent pipe is used.
‡For installation on a combustible floor, do not install the furnace
directly on carpeting, tile or other combustible materials other
than wood flooring.
†Left side requires 3 inches if a single wall vent is used on 14-1/2
in. cabinets, or 2inches if a single wall vent pipe is used on 17-1/2
in. cabinets.
FIGURE 7

Page 9
Return Air -- Upow Applications
Return air can be brought in through the bottom or either
side of the furnace installed in an upow application. If the
furnace is installed on a platform with bottom return, make
an airtight seal between the bottom of the furnace and the
platform to ensure that the furnace operates properly and
safely. The furnace is equipped with a removable bottom
panel to facilitate installation.
Markings are provided on both sides of the furnace cab-
inet for installations that require side return air. Cut the
furnace cabinet at the maximum dimensions shown on
page 2.
NOTE - 60C units that require air volumes over 1800 cfm
(850 L/s) must have one of the following:
1 - Single side return air and Optional Return Air Base
with transition that must accommodate required
20 x 25 x 1 inch (508 x 635 x 25 mm) air lter to
maintain proper velocity.
2 - Bottom return air
3 - Return air from both sides.
4 - Bottom and one side return air.
Refer to Engineering Handbook for additional information.
Return Air
Plenum
Transition
20” X 25” X 1”
(508mm X 635mm X 25mm)
Cleanable Filter
AIR FLOW
Single Side Return Air
(with transition and filter)
FIGURE 8
Optional Return Air Base
(Upflow Applications Only -- For use with A, B, C and D cabinets)
NOTE- Optional Side Return Air Filter Kits are not for use with Optional Return Air Base.
1Both the unit return air opening and the base return air opening must be covered by a single plenum or IAQ cabinet.
Minimum unit side return air opening dimensions for units requiring 1800 cfm or more of air (W x H): 23 x 11 in. (584 x 279 mm).
The opening can be cut as needed to accommodate plenum or IAQ cabinet while maintaining dimensions shown.
Side return air openings must be cut in the field. There are cutting guides stenciled on the cabinet for the side return air
opening. The size of the opening must not extend beyond the markings on the furnace cabinet.
2To minimize pressure drop, the largest opening height possible (up to 14 inches 356 mm) is preferred.
FURNACE
FRONT
AIR FLOW
14−1/2 (368) A Width (65W75)
17−1/2 (446) B Width (50W98)
21 (533) C Width (50W99)
24−1/2 (622) D Width (51W00)
1Unit side return air
Opening
SIDE VIEW
3−1/4
(83)
1
23 (584)
Overall
(Maximum)
(584)
23
3/4
(19)
122−7/16
(570)
Overall
(Maximum)
SIDE RETURN
AIR OPENINGS
(Either Side)
5−5/8
(143)
1Minimum
11 (279)
2Maximum
14 (356)
(683)
26−7/8
7−1/4
(184)
IF BASE
IS USED
WITHOUT
IAQ CABINET,
A SINGLE
RETURN AIR
PLENUM
MUST
COVER BOTH
UNIT AND
RETURN
AIR BASE
OPENINGS
INDOOR AIR
QUALITY
CABINET
(PCO, Filter
Cabinet, etc.)
AIR BASE
OPTIONAL
RETURN
FIGURE 9

Page 10
Removing the Bottom Panel
Remove the two screws that secure the bottom cap to the
furnace. Pivot the bottom cap down to release the bottom
panel. Once the bottom panel has been removed, reinstall
the bottom cap. See gure 10.
Removing the Bottom Panel
Screw
Bottom Panel
Bottom Cap
FIGURE 10
Horizontal Application
Installation Clearances
Top
Bottom
Left
End
Right
End
AIR FLOW
Vent Connector
Type Type CType B1
Top 0 0
*Front 2-1/4 in. (57 mm)**2-1/4 in. (57 mm)
Back 0 0
Ends 2 in. (51 mm)2 in. (51 mm)
Vent 6 in. (152 mm) 1 in. (25 mm)
Floor 0‡0‡
*Front clearance in alcove installation must be 24 in. (610 mm).
Maintain a minimum of 24 in. (610 mm) for front service access.
** 4-1/2 in. if singlewall vent pipe is used.
‡For installations on a combustible floor, do not install the furnace
directly on carpeting, tile or other combustible materials other
than wood flooring.
FIGURE 11
Horizontal Applications
The ML180UHV furnace can be installed in horizontal ap-
plications. Order horizontal suspension kit (51W10) from
Lennox, or use equivalent suspension method.
Allow for clearances to combustible materials as indicated
on the unit nameplate. Minimum clearances for closet or
alcove installations are shown in gure 11.
This furnace may be installed in either an attic or a crawl-
space. Either suspend the furnace from roof rafters or
oor joists, as shown in gure 12, or install the furnace on
a platform, as shown in gure 13.
Typical Horizontal Application
Unit Suspended in Attic or Crawlspace
Bracket
Bottom Cap
Metal Strap
3/16 inch
Air Flow
FIGURE 12
NOTE - Heavy-gauge perforated sheet metal straps may
be used to suspend the unit from roof rafters or ceiling
joists. When straps are used to suspend the unit in this
way, support must be provided for both the ends. The
straps must not interfere with the plenum or exhaust pip-
ing installation. Cooling coils and supply and return air
plenums must be supported separately.
NOTE - When the furnace is installed on a platform in a
crawlspace, it must be elevated enough to avoid water
damage and to allow the evaporator coil to drain.
Return Air -- Horizontal Applications
Return air must be brought in through the end of a fur-
nace installed in a horizontal application. The furnace is
equipped with a removable bottom panel to facilitate in-
stallation. See gure 10.