Lennox EL280UH070P24A, EL280UH070P36A, EL280UH070XP36A, EL280UH110P48C, EL280UH110XP60C Installation Instructions Manual

© 2017 Lennox Industries Inc.

OFF

ON

C

C

HI

I
I

LO

HI

UPFLOW

HORIZONTAL LEFT HORIZONTAL RIGHT

AIR FLOW

AIR FLOWAIR FLOW

Dallas, Texas USA

INSTALLATION
INSTRUCTIONS
EL280UH

ELITE ® SERIES GAS FURNACE
UPFL0W / HORIZONTAL AIR DISCHARGE

507333-01
11/2017
Supersedes 05/2016

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 man­uals, be alert to the potential for personal injury or death

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.

Contents

Unit Dimensions .............................................................2

EL280UH Gas Furnace ..................................................3

Shipping and Packing List ..............................................3

Safety Information ..........................................................3

Use of Furnace as Construction Heater .........................4

General ........................................................................... 4

Combustion, Dilution & Ventilation Air ............................5

Setting Equipment .........................................................8

Filters ............................................................................ 11

Duct System .................................................................12

Venting..........................................................................13

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.

Gas Piping .................................................................... 21

Electrical ....................................................................... 23

Integrated Control ......................................................... 28

Unit Start Up ................................................................. 29

Gas Pressure Adjustment ............................................. 30

Proper Combustion.......................................................31

High Altitude .................................................................31

Other Unit Adjustments................................................. 32

Sequence of Operation.................................................32

Service..........................................................................34

Repair Parts List ........................................................... 36

Start-Up & Performance Checl List ..............................37

Page 1

Unit Dimensions - inches (mm)

AIR FLOW

23

(584)

(19)

3/4

(19)

1

Bottom 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

B

9/16 (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
7 (178) Left

2

FLUE OUTLET

(Either Side)

3

OPTIONAL

EXTERNAL

SIDE RETURN

AIR FILTER KIT

(Either Side)

16

(406)

14-3/4

(375)

3

OPTIONAL

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 and 60D size units that require second stage
air volumes over 1800 cfm (850 L/s) must have one
of the following:

1. Single side return air with transition, to accommodate
20 x 25 x 1 in. (508 x 635 x 25 mm) cleanable air
filter. Required to maintain proper air velocity.

2. Single side return air with optional Return Air Base

3. Bottom return air.

4. Return air from both sides.

5. Bottom and

one side return air.

See Blower Performance Ta bles for additional information.

3-1/4 (83)

5/8

(16)

1

3-1/4

(83)

23-3/4

(603)

25

(635)

1-1/2 (38)

Front Panel

EL280UH Model

070P24A
070(X)P36A

090P36A
090(X)P48B

110P48C
110(X)P60C

14-1/2 368 13-3/8 340 13 330 4-3/4 121

17-1/2 446 16-3/8 416 16 406 6-1/4 159

A B C D

in mm in mm in mm in mm

21 533 19-7/8 504 19-1/2 495 8 203

135P60D 24-1/2 622 23-3/8 546 23 584 9-3/4 248

Page 2

EL280UH Gas Furnace

The EL280UH unit is shipped ready for installation in the
upow or horizontal right position (for horizontal left posi­tion the combustion air pressure switch must be moved).
The furnace is shipped with the bottom panel in place.
The bottom panel must be removed if the unit is to be in-

stalled 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 EL280UH 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 - Propane/LP 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
difcult to smell. An LP/propane leak detector should be

installed in all LP applications.

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 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 injury. Take
care while handling this equipment and wear gloves and
protective clothing.

Certications

EL280UH 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 open­ings 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 vent­ing tables (in this instruction) and applicable 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. Accessi­bility 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 ac­cording to recommended good practice requirements and
current National Fuel Gas Code.

Temperature Rise

NOTE - Furnace must be adjusted to obtain a tempera­ture 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 EL280UH furnace must be installed so that its electri­cal components are protected from water.

Page 3

Installed in Combination with a Cooling Coil

When this furnace is used with cooling units, it shall be in­stalled in parallel with, or on the upstream side of, cooling
units to avoid condensation in the heating compartment.

See gure 1. With a parallel ow arrangement, a damper
(or other means to control the ow of air) must adequately

prevent chilled air from entering the furnace. If the damper
is manually operated, it must be equipped to prevent op­eration of either the heating or the cooling unit, unless it is
in the full HEAT or COOL setting. See gure 1.

Heating Unit Installed Parallell to Air Handler Unit

Dampers

(open during heating operation only)

Gas Unit

Air Handler Unit

Dampers

(open during cooling operation only)

Use of Furnace as Construction Heater

Lennox does not recommend the use of EL280UH units
as a construction heater during any phase of construc­tion. Very low return air temperatures, harmful vapors and

operation of the unit with clogged or misplaced lters will

damage the unit.
EL280UH 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.

Heating Unit Installed Upstream of Cooling Unit

Gas 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 Elec­tric Code, ANSI/NFPA No. 70. The National Electric Code
(ANSI/NFPA No. 70) is available from the following ad­dress:

National Fire Protection Association
1 Battery March Park
Quincy, MA 02269

NOTE - This furnace is designed for a minimum continu­ous 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 EL280UH furnace may be installed in alcoves, clos­ets, 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.

• 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 out­door air to the furnace. Do not connect duct direct-

ly 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 author­ities having jurisdiction before installation.

In addition to the requirements outlined previously, the
following general recommendations must be considered
when installing a EL280UH 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 termi­nation point.

Page 4

• Do not install the furnace where drafts might blow
directly into it. This could cause improper combus­tion 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 fur­nace.

• Please consult the manufacturer of your evaporator
coil for their recommendations on distance required
between the heat exchanger and their drain pan.
Adequate space must be provided between the
drain pan and the furnace heat exchanger.

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.

WARNING

This product contains a chemical known to the State
of California to cause cancer, birth defects, or other
reproductive harm.

Combustion, Dilution & Ventilation Air

In the past, there was no problem in bringing in suf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. Un­less 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 oc­cur in the furnace vent pipe or chimney. As a result, com­bustion gases enter the living space creating a potentially
dangerous situation.

In the absence of local codes concerning air for combus­tion and ventilation, use the guidelines and procedures in
this section to install EL280UH furnaces to ensure ef­cient and safe operation. You must consider combustion
air needs and requirements for exhaust vents and gas
piping. A portion of this information has been reprinted
with permission from the National Fuel Gas Code (AN­SI-Z223.1). This reprinted material is not the complete

and ofcial position of the ANSI on the referenced subject,

which is represented only by the standard in its entirety.

CAUTION

Insuf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

All gas-red appliances require air for the combustion
process. If sufcient combustion air is not available, the
furnace or other appliances will operate inefciently and

unsafely. Enough air must be provided to meet the needs
of all fuel-burning appliances and appliances such as ex­haust fans which force air out of the house. When re­places, exhaust fans, or clothes dryers are used at the
same time as the furnace, much more air is necessary
to ensure proper combustion and to prevent a downdraft.

Insufcient air causes incomplete combustion which can

result in carbon monoxide.
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 com­ponents.

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 com­bined 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

un con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 5

Conned Space

Air from Inside

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 plat-

form or at the return air duct connection can cause a po­tentially dangerous negative pressure condition. Air for
combustion and ventilation can be brought into the con-

ned space either from inside the building or from outside

.

EQUIPMENT IN CONFINED

CHIMNEY

OR GAS

VENT

FURNACE

AIR FLOW

NOTE - Each opening shall have a free area of at least one square
inch (645 mm
ing of all equipment in the enclosure, but not less than 100 square
inches (64516 mm

2

2

).

SPACE ALL AIR FROM INSIDE

WATER

HEATER

OPENINGS

(To Adjacent

Room)

If 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 input 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 ventila­tion, the conned space must have two permanent open­ings. 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 communi­cate directly or by ducts with the outdoors or spaces (crawl
or attic) that freely communicate with the outdoors or in­directly 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 communi­cating 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-sec­tional 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 effect 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.

FIGURE 2

Page 6

CHIMNEY OR

EQUIPMENT IN

CONFINED SPACE

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 mm

2

) 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 mm

2

)
per 4,000 Btu (1.17 kW) per hour of the total input rating of all
other equipment in the enclosure.

FURNACE

AIR FLOW

GAS VENT

FURNACE

(Inlet Air from Crawlspace and Outlet Air to Ventilated Attic)

VENTILATION LOUVERS

(Each end of attic)

EQUIPMENT IN CONFINED SPACE

ALL AIR FROM OUTSIDE

OUTLET

AIR

WATER

HEATER

CHIMNEY

OR GAS

VENT

FURNACE

VENTILATION

LOUVERS

(For unheated crawl space)

AIR FLOW

NOTE-The inlet and outlet air openings shall each have a free area of at least one square inch (645

2

mm

) per 4,000 Btu (1.17 kW) per hour of the total input rating of all equipment in the enclosure.

INLET

AIR

FIGURE 3

EQUIPMENT IN CONFINED SPACE

ALL AIR FROM OUTSIDE

(All Air Through Ventilated Attic)

VENTILATION LOUVERS

(Each end of attic)

OUTLET

AIR

INLET AIR

(Ends 12 in.

above bottom)

WATER

HEATER

AIR FLOW

NOTE-The inlet and outlet air openings shall each have a
free area of at least one square inch (645 mm

ment in the enclosure.

FIGURE 4

2

) per 4,000

FIGURE 5

Page 7

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 affect the operation of the safety
control devices, which could result in personal injury or
death.

The EL280UH 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 1/3HP and 1/2HP blower motors are
equipped with three exible legs and one shipping leg. See
gure 6. In some units with 1/3HP blower motor, the ship­ping leg is exible with rubber mounting grommets similar
to the other three mounting legs and require no modica­tion. The rest of the units with 1/3HP and 1/2HP blower
motors (these blower motor housings will be tagged) have
a rigid shipping leg equipped with a shipping bolt and at
white plastic washer. The bolt and washer must be re-
moved before the furnace is placed into operation. Af­ter the bolt and washer have been removed, the rigid leg
will not touch the blower housing.

Blower motor with three exible legs and one
rigid shipping leg. Blower motor housings
will be tagged for shipping bolt removal

RIGID LEG

(Remove shipping bolt

and washer)

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

Left Side

AIR FLOW

Bottom

Type of Vent

Connector

Top 1 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.
** 3-1/4 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
inch
nets.

Type C Type B1

Right Side

FIGURE 6

FIGURE 7

Page 8

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 cab­inet for installations that require side return air. Cut the
furnace cabinet at the maximum dimensions shown on
page 2.

NOTE - 60C and 60D units that require air volumes
over 1800 cfm (850 L/s) must have one of the follow­ing:

1 - Single side return air with transition to accommodate

20 x 25 x 1 in. (508 x 635 x 25 mm) cleanable air

lter. (Required to maintain proper air velocity.) See
gure 8.

2 - 2 - Single side return air with optional return

airbase. See gure 9.

3 - 3 - Bottom return air.
4 - 4 - Return air from both sides.
5 - 5 - Bottom and one side return air.

Refer to Engineering Handbook for additional information.

Single Side Return Air

(with transition and filter)

20” X 25” X 1”

(508mm X635mm X 25mm)

Cleanable Filter

Return Air

Plenum

AIR FLOW

Transition

FIGURE 8

Optional Return Air Base

(Upflow Applications Only -- For use with A, B, C and D cabinets)

FURNACE

FRONT

IF BASE
IS USED

WITHOUT

INDOOR AIR

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)

NOTE- Optional Side Return Air Filter Kits are not for use with Optional Return Air Base.

1

Both 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.

2

To minimize pressure drop, the largest opening height possible (up to 14 inches) is preferred.

OPTIONAL

RETURN AIR BASE

IAQ CABINET,

A SINGLE

RETURN AIR

PLENUM

MUST

COVER BOTH

UNIT AND

RETURN

AIR BASE

OPENINGS

3−1/4

(83)

7−1/4
(184)

1

23 (584)

Overall

(Maximum)

1

Unit side return air

Opening

5−5/8

(143)

SIDE RETURN

AIR OPENINGS

(Either Side)

26−7/8

(683)

SIDE VIEW

23

(584)

1

Minimum

11 (279)

2

Maximum

14 (356)

1

22−7/16

(570)

Overall

(Maximum)

3/4

(19)

FIGURE 9

Page 9

Removing the Bottom Panel

Removing the Bottom Panel

Hori

zontal Application

Horizontal Applications

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.

Screw

Bottom Cap

The EL280UH furnace can be installed in horizontal ap­plications. 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 crawl­space. 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

Metal Strap

Bottom Cap

3/16 inch

Air Flow

Bottom Panel

FIGURE 10

Installation Clearances

Left
End

Vent Connector

Type

Top 0 0

*Front 2-1/4 in. (57 mm)** 2-14 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.
** 3-1/4 in. if single wall 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.

Top

Right

AIR FLOW

End

Bottom

Type C Type B1

FIGURE 12

NOTE - Heavy-gauge perforated sheet metal straps may
be used to suspend the unit from roof rafters or ceiling
oists. 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 pip­ing 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.

CAUTION

If this unit is being installed in a space serviced by an
exhaust fan, power exhaust fan, or other device which
may create a negative pressure in the space, take care

when sizing the inlet air opening. The inlet air opening
must be sized to accommodate the maximum volume

of exhausted air as well as the maximum volume of
combustion air required for all gas appliances serviced
by this space.

FIGURE 11

Page 10

Horizontal Application

Unit Installed on Platform

Line contact is permissible

See the unit nameplate for
clearances.

GAS

ENTRY

SERVICE PLATFORM

VENT

PIPE

FIGURE 13

WARNING

Improper installation of the furnace can result in personal

injury or death. Combustion and ue products must

never be allowed to enter the return air system or the
living space. Use screws and joint tape to seal the return
air system to the furnace.

In platform installations with bottom return air, the furnace
should be sealed airtight to the return air plenum. A
door must never be used as a portion of the return air
duct system. The base must provide a stable support
and an airtight seal to the furnace. Allow absolutely no
sagging, cracks, gaps, etc. The return and supply air
duct systems must never be connected to or from other

heating devices such as a replace or stove, etc. Fire,

explosion, carbon monoxide poisoning, personal injury
and/or property damage could result.

WARNING

The blower access panel must be securely in place when
the blower and burners are operating. Gas fumes, which
could contain carbon monoxide, can be drawn into living
space resulting in personal injury or death.

Filters

This unit is not equipped with a lter or rack. A eld-pro­vided high-velocity lter is required for the unit to operate
properly. Table 1 lists recommended lter sizes.

A lter must be in place any time the unit is operating.

IMPORTANT

If a highefciency lter is being installed as part of this
system to ensure better indoor air quality, the lter must
be properly sized. Highefciency lters have a higher
static pressure drop than standardefciency glass/foam
lters. If the pressure drop is too great, system capacity

and performance may be reduced. The pressure drop
may also cause the limit to trip more frequently during

the winter and the indoor coil to freeze in the summer,

resulting in an increase in the number of service calls.

Before using any lter with this system, check the
specications provided by the lter manufacturer against

the data given in the appropriate Lennox Product

Specications bulletin. Additional information is provided

in Service and Application Note ACC002 (August 2000).

TABLE 1

Furnace Cabinet

Width

14-1/2” 16 X 25 X 1 (1) 14 X 25 X 1 (1)

17-1/2” 16 X 25 X 1 (1) 16 X 25 X 1 (1)

21” 16 X 25 X 1 (1) 20 X 25 X 1 (1)

24-1/2” 16 X 25 X 1 (2) 24 X 25 X 1 (1)

Side Return Bottom Return

Filter Size

Page 11

Duct

Use industry-approved standards (such as those pub­lished by Air Conditioning Contractors of America or Amer­ican Society of Heating, Refrigerating and Air Condition-

ing Engineers) to size and install the supply and return

air duct system. This will result in a quiet and low-static
system that has uniform air distribution.

NOTE - Do not operate the furnace in the heating mode
with an external static pressure that exceeds 0.5 inches
w.c. Higher external static pressures may cause erratic
limit operation.

Supply Air Plenum

If the furnace is installed without a cooling coil, a remov­able access panel must be installed in the supply air duct.
The access panel should be large enough to permit in-

spection (either by smoke or reected light) of the heat

exchanger for leaks after the furnace is installed. The
furnace access panel must always be in place when the
furnace is operating and it must not allow leaks into the
supply air duct system.

Return Air Plenum

NOTE - Return air must not be drawn from a roomwhere
this furnace, or any other gas-fueled appliance (i.e., water
heater), or carbon monoxide producing device (i.e., wood
replace) is installed.

When return air is drawn from a room, a negative pressure
is created in the room. If a gas appliance is operating in

a room with negative pressure, the ue products can be

pulled back down the vent pipe and into the room. This
reverse ow of the ue gas may result in incomplete com­bustion and the formation of carbon monoxide gas. This
toxic gas might then be distributed throughout the house
by the furnace duct system.

In upow applications, the return air can be brought in

through the bottom or either side of the furnace. If a fur­nace with bottom return air is installed on a platform, make
an airtight seal between the bottom of the furnace and
the platform to ensure that the unit operates properly and
safely. Use berglass sealing strips, caulking, or equiva­lent sealing method between the plenum and the furnace

cabinet to ensure a tight seal. If a lter is installed, size the
return air duct to t the lter frame.

Page 12

Venting

UPFLOW POSITION

A 4-inch diameter ue transition is factory-installed on

the combustion air inducer outlet of all models. Figure 15
shows the combustion air inducer as shipped from the fac­tory.

Mounting Screws Location

Mounting Screws

FIGURE 14

UPFLOW POSITION

Top Vent Discharge

Vent Pipe

Flue

Transition

Pressure

Switch

Make -Up

Box

Collector Box

If necessary reposition the combustion air inducer, pres­sure switch and or make up box as needed per the follow-

ing steps and see gures 16 through 21.

1 - Remove the four mounting screws which secure the

combustion air inducer / pressure switch assembly

to the orice plate. See gure 14. Lift and rotate

the assembly 90 degrees clockwise or counter
clockwise to either the 3 o’clock position or to 9
o’clock position and re-secure with four screws.
Gasket should be left in place.

2 - 2 - Use tin snips to cut preferred opening

on the cabinet for repositioning the ue

outlet. Use the cut out piece

Left Side Vent Discharge

xoB rotcelloCetalP revoC

Pressure

Switch

Vent Pipe

Flue

Transition

Gas supply piping must be brought into the unit from the right

side in order to accommodate the flue pipe.

Remove make-up box assembly (2 screws) and cut wire tie to
free make-up box wires. Re-install make-up box on other side
of cabinet.

Re-secure make-up box wires, either pulling excess wires
through the blower compartment and securing with supplied
wire tie, or coil excess wire and secure to the gas manifold.

Make-Up

Box

AIR

FLOW

FLOW

AIR

FIGURE 15

IMPORTANT

The unit will not vent properly with the ue transition

pointed down in the 6 o’clock position. The combustion
air inducer may be rotated clockwise or counterclockwise
by 90° to allow for top or side vent discharge in all

applications. When the unit is installed, the ue transition

must be in the 9 o’clock, 12 o’clock or 3 o’clock position.

FIGURE 16

UPFLOW POSITION

Right Side Vent Discharge

Cover Plate

Pressure

Switch

Collector

Box

Make-Up

Box

FLOW

AIR

Pressure switch tubing may be too long. Cut to

fit , then re-attach to barbed fitting on pressure
switch. Tubing must not be allowed to sag.

Flue Transition

FIGURE 17

Vent Pipe

Page 13

HORIZONTAL LEFT POSITION

tie or coil excess wire and secure to the gas manifold.

HORIZONTAL LEFT POSITION

wire tie, or coil excess wire and secure to the gas manifold.

HORIZONTAL RIGHT POSITION

wire tie, or coil excess wire and secure to the gas manifold.

Top Vent Discharge

Vent Pipe

Pressure Switch

Vent Pipe

Flue Transition

Top Vent Discharge

Pressure Switch

Flue

Transition

FLOW

Cover Plate

Make-Up Box

Disconnect
sure switch assembly. Remove pressure switch assembly (1
screw) and cut wire tie to free pressure switch wires. Re-install
pressure switch on the other side of orifice plate and re-connect
pressure switch hose.

Re-secure pressure switch wires by either pulling excess wires
through the blower compartment and securing with supplied wire

Collector Box

FIGURE 18

Side Vent Discharge

Pressure Switch

AIR

Cover Plate

AIR

FLOW

Collector Box

Make-Up Box

Gas supply piping must be brought into the unit from the bottom

in order to accommodate the flue pipe.
Remove make-up box assembly (2 screws) and cut wire tie to

free make-up box wires. Re-install make-up box on other side
of cabinet.

Re-secure make-up box wires by either pulling excess wires
through the blower compartment and securing with supplied

FIGURE 20

HORIZONTAL RIGHT POSITION

Side Vent Discharge

Pressure Switch

AIR

Flue Transition

Make-Up Box

Disconnect pressure switch hose from barbed fitting on the

pressure switch assembly. Remove pressure switch assembly
(1 screw) and cut wire tie to free pressure switch wires. Re­install pressure switch on the other side of orifice plate and re­connect pressure switch hose.

Re-secure pressure switch wires by either pulling excess wires
through the blower compartment and securing with supplied

Collector Box

FLOW

AIR

FLOW

Flue

Transition

Collector Box

make up box

FIGURE 21

FIGURE 19

Page 14

The EL280UH series units are classied as fan-assisted

Category I furnaces when vertically vented according to
the latest edition of National Fuel Gas Code (NFPA 54 /
ANSI Z223.1) in the USA. A fan-assisted Category I fur­nace is an appliance equipped with an integral mechan­ical means to either draw or force combustion products
through the combustion chamber and/or heat exchang-

er. The EL280UH is not approved for use with horizontal

venting.

NOTE - Use these instructions as a guide. They do not
supersede local codes. This furnace must be vented ac­cording to all local codes these installation instructions,
and the provided venting tables in these instructions

The venting tables in this manual were extracted from the
National Fuel Gas Code (NFPA 54 / ANSI Z223.1) and are
provided as a guide for proper vent installation. Proper
application, termination, construction and location of vents
must conform to local codes having jurisdiction. In the ab-

sence of local codes, the NFGC serves as the dening

document.
Refer to the tables and the venting information contained

in these instructions to properly size and install the venting

system.
Use self-drilling sheet metal screws or a mechanical fas-

tener to rmly secure the vent pipe to the round collar of
the ue transition. If self-drilling screws are used to attach

the vent pipe, it is recommended that three be used. Drive
one self-drilling screw through the front and one through

each side of the vent pipe and collar. See gure 22.
Install the rst vent connector elbow at a minimum of six

inches (152 mm) from the furnace vent outlet. See gure

22.

Venting Using a Masonry Chimney

The following additional requirements apply when a lined
masonry chimney is used to vent this furnace.Masonry
chimneys used to vent Category I central furnaces must
be either tile-lined or lined with a listed metal lining sys­tem or dedicated gas vent. Unlined masonry chimneys are

prohibited. See gures 23 and 24 for common venting.

A chimney with one or more sides exposed to the outside
of the structure is considered to be an exterior chimney.

An exterior masonry chimney that is not tile-lined must be

lined with B1 vent or a listed insulated exible metal vent.

An exterior tile-lined chimney that is sealed and capped

may be lined with a listed uninsulated exible metal vent.

If the existing chimney will not accommodate a listed met­al liner, either the chimney must be rebuilt to accommo­date one of these liners or an alternate approved venting
method must be found.

Insulation for the exible vent pipe must be an encapsulat­ed berglass sleeve recommende

IMPORTANT

Once the venting system is installed, attach the
“Disconnected Vent” warning sticker to a visible area

of the plenum near the vent pipe. See gure 22. The

warning sticker is provided in the bag assembly. Order
kit 66W04 for additional stickers..

WARNING

Asphyxiation hazard. The exhaust vent for this furnace
must be securely connected to the furnace uetransition

at all times.

VENT CONNECTION UPFLOW AND HORIZONTAL POSITION

“DISCONNECTED VENT”

WARNING

VENT PIPE

(min. 6” length)

FLUE TRANSITION

COLLAR

STICKER

“DISCONNECTED VENT”

FIGURE 22

Page 15

WARNING

STICKER

VENT PIPE

(min. 6” length)

FLUE

TRANSITION

COLLAR

Common Venting Using Metal-Lined Masonry Chimney

4 in. (102 mm)

minimum

MIN. LENGTH -- AS

SHORT AS PRACTICAL

MAX. LENGTH

-- SEE NOTE 1
BELOW.

SEALED

PERMANENTLY

SEALED FIREPLACE

OPENING

EXTERIOR

CHIMNEY WITH

METAL

LINER

VENT CONNECTOR

NOTE 1 - Refer to the provided venting tables for installations. Refer
to the capacity requirements shown in the provided venting tables.

OTHER

APPLIANCE

FURNACE

5 ft. (1.5 m)

minimum

AIR FLOW

FIGURE 23

DO NOT insulate the space between the liner and
the chimney wall with puffed mica or any other loose
granular insulating material.

IMPORTANT

SINGLE appliance venting of a fan-assisted furnace into
a tile-lined masonry chimney (interior or outside wall)

is PROHIBITED. The chimney must rst be lined with
either type B1 vent or an insulated single wall exible
vent lining system which has been sized according to the

provided venting tables and the vent pipe manufacturer’s
instructions.

A fan-assisted furnace may be commonly vented into an
existing lined masonry chimney if the following conditions

are met:

• The chimney is currently serving at least one draft­hoodequipped appliance;

• The vent connectors and chimney are sized accord-
ing to the provided venting tables.

If type B1 double-wall vent is used inside a chimney, no
otherappliance can be vented into the chimney. The out-

er wallof type B1 vent pipe must not be exposed to ue

products.

A type B1 vent or masonry chimney liner shall terminate
above the roof surface with a listed cap or a listed roof as­sembly according to the terms of their respective listings
and the vent manufacturer’s instructions.

When inspection reveals that an existing chimney is not
safe for the intended purpose, it shall be rebuilt to conform

to nationally recognized standards, lined or relined with

suitable materials, or replaced with a gas vent or chimney
suitable for venting EL280UH series units. The chimney
passageway must be checked periodically to ensure that
it is clear and free of obstructions.

Do not install a manual damper, barometric draft regulator,

or ue restrictor between the furnace and the chimney.

Never connect a Category I appliance to a chimney that is

servicing a solid-fuel appliance. If a replace chimney ue
is used to vent this appliance, the replace opening must

be permanently sealed.
A type B or listed chimney lining system that passes

through an unused masonry chimney ue is not consid­ered to be exposed to the outdoors.

General Venting Requirements

Vent all EL280UH furnaces according to these instruc­tions:

1 - Vent diameter recommendations and maximum

allowable piping runs are found in the provided
venting tables.

2 - In no case should the vent or vent connector

diameter be less than the diameter specied in the

provided venting tables.

3 - The minimum vent capacity determined by the sizing

tables must be less than the low re input rating and

the maximum vent capacity must be greater than

the high re input rating.

4 - Single appliance vents - If the vertical vent or tile-

lined chimney has a larger diameter or ow area

than the vent connector, use the vertical vent
diameter to determine the minimum vent capacity

and the vent connector diameter to determine
the maximum vent capacity. The ow area of the
vertical vent, however, shall not exceed 7 times

the ow area of the listed appliance categorized
vent area, drafthood outlet area or ue collar area

unless designed according to approved engineering
methods.

5 - Multiple appliance vents - The ow area of the

largest section of vertical vent or chimney shall
not exceed 7 times the smallest listed appliance

categorized vent area, drafthood outlet area or ue

collar area unless designed

Page 16

Common Venting Using Tile-Lined Interior Masonry Chimney and Combined Vent Connector

MINIMUM LENGTH = AS SHORT AS PRACTICAL.
FOR MAXIMUM LENGTH SEE NOTE TO LEFT

NOTE- Refer to provided venting tables
for installations.

OTHER

APPLIANCE

AIR FLOW

FIGURE 24

6 - The entire length of single wall metal vent connector

shall be readily accessible for inspection, cleaning,
and replacement.

7 - Single appliance venting congurations with

zero lateral lengths (table 3) is assumed to have

no elbows in the vent system. For all other vent

congurations, the vent system is assumed to have

two 90° elbows. For each additional 90° elbow or
equivalent (for example two 45° elbows equal one
90° elbow) beyond two, the maximum capacity
listed in the venting table should be reduced by 10%
(0.90 x maximum listed capacity).

8 - The common venting tables (4 and 5) were generated

using a maximum horizontal vent connector length

of 1-1/2 feet (.46 m) for

TABLE 2

Connector Diameter inches (mm)

3 (76) 4-1/2 (1.37)

4 (102) 6 (1.83)

5 (127) 7-1/2 (2.29)

6 (152) 10-1/2 (3.20)

7 (178) 10-1/2 (3.20)

Maximum Horizontal Connector

Length feet (m)

9 - If the common vertical vent is offset, the maximum

common vent capacity listed in the common venting
tables should be reduced by 20%, the equivalent
of two 90° elbows (0.80 x maximum common vent

capacity).The horizontal length of the offset shall

not exceed1-1/2 feet (.46 m) for each inch (25 mm)
of common vent diameter.

CONNECTOR

FURNACE

INTERIOR TILE-LINED
MASONRY CHIMNEY

NOTE - the chimney must be properly
sized per provided venting tables or
lined with listed metal lining system.

VENT

PERMANENTLY
SEALED FIREPLACE
OPENING

10 - The vent pipe should be as short as possible with

the least number of elbows and angles required to
complete the job. Route the vent connector to the
vent using the shortest possible route.

11 - A vent connector shall be supported without any

dips or sags and shall slope a minimum of 1/4 inch
(6.4 mm) per linear foot (305 mm) of connector,
back toward the appliance.

12 - Vent connectors shall be rmly attached to the

furnace ue collar by self-drilling screws or other

approved means, except vent connectors of listed
type B vent material which shall be assembled
according to the manufacturer’s instructions. Joints
between sections of single wall connector piping
shall be fastened by screws or other approved
means.

13 - When the vent connector used for Category I

appliances must be located in or pass through a
crawlspace, attic or other areas which may be cold,
that portion of the vent connector shall be constructed
of listed double-wall type B vent material or material
having equivalent insulation qualities.

14 - All venting pipe passing through oors, walls, and

ceilings must be installed with the listed clearance

to combustible materials and be re stopped

according to local codes. In absence of local codes,
refer to NFGC (Z223.1).

15 - No portion of the venting system can extend into,

or pass through any circulation air duct or plenum.

Page 17

16 - Vent connectors serving Category I appliances shall

not be connected to any portion of mechanical draft
systems operating under positive pressure such as
Category III or IV venting systems.

17 - If vent connectors are combined prior to entering

the common vent, the maximum common vent
capacity listed in the common venting tables must
be reduced by 10%, the equivalent of one 90° elbow
(0.90 x maximum common vent capacity).

18 - The common vent diameter must always be at least

20 - Do not install a manual damper, barometric draft

regulator or ue restrictor between the furnace and

the chimney.

21 - When connecting this appliance to an existing

dedicated or common venting system, you must
inspect the venting system’s general condition
and look for signs of corrosion. The existing vent

pipe size must conform to these instructions and

the provided venting tables. If the existing venting
system does

as large as the largest vent connector diameter.

19 - In no case, shall the vent connector be sized more

than two consecutive table size diameters over the
size of the draft hood outlet or ue collar outlet.

TABLE 3

Capacity of Type B Double-Wall Vents with Type B Double-Wall Connectors

Serving a Single Category I Appliance

Height

H

(feet)

6

8

10

15

20

30

NOTE - Single appliance venting congurations with zero lateral lengths are assumed to have no elbows in the vent system. For
all other vent congurations, the vent system is assumed to have two 90° elbows. For each additional 90° elbow or equivalent (for
example two 45° elbows equal one 90° elbow) beyond two, the maximum capacity listed in the venting table should be reduced by
10 percent (0.90 x maximum listed capacity).

Lateral

L

(feet)

0 0 78 0 152 0 251 0 375
2 13 51 18 97 27 157 32 232
4 21 49 30 94 39 153 50 227
6 25 46 36 91 47 149 59 223
0 0 84 0 165 0 276 0 415
2 12 57 16 109 25 178 28 263
5 23 53 32 103 42 171 53 255
8 28 49 39 98 51 164 64 247
0 0 88 0 175 0 295 0 447
2 12 61 17 118 23 194 26 289
5 23 57 32 113 41 187 52 280

10 30 51 41 104 54 176 67 267

0 0 94 0 191 0 327 0 502
2 11 69 15 136 20 226 22 339

5 22 65 30 130 39 219 49 330
10 29 59 40 121 51 206 64 315
15 35 53 48 112 61 195 76 301

0 0 97 0 202 0 349 0 540

2 10 75 14 149 18 250 20 377

5 21 71 29 143 38 242 47 367

10 28 64 38 133 50 229 62 351
15 34 58 46 124 59 217 73 337
20 48 52 55 116 69 206 84 322

0 0 100 0 213 0 374 0 587

2 9 81 13 166 14 283 18 432

5 21 77 28 160 36 275 45 421
10 27 70 37 150 48 262 59 405
15 33 64 44 141 57 249 70 389
20 56 58 53 132 66 237 80 374
30 NA NA 73 11 3 88 214 104 346

3 inch 4 inch 5 inch 6 inch

Min Max Min Max Min Max Min Max

Vent and Connector Diameter - D (inches)

Appliance Input Rating in Thousands of Btu Per Hour

Page 18

Height

H

(feet)

6

8

10

15

20

30

TABLE 4

Vent Connector Capacity

Type B Double-Wall Vents with Type B Double-Wall Connectors

Serving Two or More Category I Appliances

Lateral

L

(feet)

1 22 37 35 66 46 106 58 164

2 23 41 37 75 48 121 60 183

3 24 44 38 81 49 132 62 199

1 22 40 35 72 49 11 4 64 176

2 23 44 36 80 51 128 66 195

3 24 47 37 87 53 139 67 210

1 22 43 34 78 49 123 65 189

2 23 47 36 86 51 136 67 206

3 24 50 37 92 52 146 69 220

1 21 50 33 89 47 142 64 220

2 22 53 35 96 49 153 66 235

3 24 55 36 102 51 163 68 248

1 21 54 33 99 46 157 62 246

2 2 57 34 105 48 167 64 259

3 23 60 35 11 0 50 176 66 271

1 20 62 31 11 3 45 181 60 288

2 21 64 33 11 8 47 190 62 299

3 22 66 34 123 48 198 64 309

3 inch 4 inch 5 inch 6 inch

Min Max Min Max Min Max Min Max

Vent and Connector Diameter - D (inches)

Appliance Input Rating in Thousands of Btu Per Hour

TABLE 5

Common Vent Capacity

Type B Double-Wall Vents with Type B Double-Wall Connectors

Serving Two or More Category I Appliances

Vent

Height

H

(feet)

6 92 81 140 116 204 161 309 248

8 101 90 155 129 224 178 339 275

10 110 97 169 141 243 194 367 299

15 125 112 195 164 283 228 427 352

20 136 123 215 183 314 255 475 394

30 152 138 244 210 361 297 547 459

FAN + FAN FAN + NAT FAN + FAN FAN + NAT FAN + FAN FAN + NAT FAN + FAN FAN + NAT

4 inch 5 inch 7 inch 7 inch

Vent and Connector Diameter - D (inches)

Appliance Input Rating in Thousands of Btu Per Hour

Page 19

Removal of the Furnace from Common Vent

In the event that an existing furnace is removed from a
venting system commonly run with separate gas applianc­es, the venting system is likely to be too large to properly
vent the remaining attached appliances.

Conduct the following test while each appliance is oper­ating and the other appliances (which are not operating)
remain connected to the common venting system. If the
venting system has been installed improperly, you must
correct the system as indicated in the general venting re­quirements section.

WARNING

CARBON MONOXIDE POISONING HAZARD
Failure to follow the steps outlined below for each

appliance connected to the venting system being placed
into operation could result in carbon monoxide poisoning
or death.

The following steps shall be followed for each appliance
connected to the venting system being placed into
operation, while all other appliances connected to the
venting system are not in operation:

1 - Seal any unused openings in the common venting

system.

2 - Inspect the venting system for proper size and

horizontal pitch. Determine that there is no blockage,
restriction, leakage, corrosion, or other deciencies

which could cause an unsafe condition.

3 - Close all building doors and windows and all

doors between the space in which the appliances
remaining connected to the common venting system
are located and other spaces of the building. Turn
on clothes dryers and any appliances not connected
to the common venting system. Turn on any exhaust
fans, such as range hoods and bathroom exhausts,
so they will operate at maximum speed. Do not

operate a summer exhaust fan. Close replace

dampers.

4 - Follow the lighting instructions. Turn on the appliance

that is being inspected. Adjust the thermostat so
that the appliance operates continuously.

5 - After the burner have operated for 5 minutes, test for

leaks of ue gases at the draft hood relief opening.
Use the ame of a match or candle.

6 - After determining that each appliance connected

to the common venting system is venting properly,
(step 3) return all doors, widows, exhaust fans,

replace dampers, and any other gas-burning

appliances to their previous mode of operation.

7 - If a venting problem is found during any of the

preceding tests, the common venting system must

be modied to correct the problem.

Resize the common venting system to the minimum
vent pipe size determined by using the appropriate

tables in Appendix G. (These are in the current stan­dards of the National Fuel Gas Code ANSI Z223.1.

Page 20

Gas Piping

Gas supply piping should not allow more than 0.5”W.C.
drop in pressure between gas meter and unit. Supply gas
pipe must not be smaller than unit gas connection

CAUTION

If a exible gas connector is required or allowed by the

authority that has jurisdiction, black iron pipe shall be
installed at the gas valve and extend outside the furnace

cabinet. The exible connector can then be added

between the black iron pipe and the gas supply line.

Gas Supply

WARNING

Do not over torque (800 in-lbs) or under torque (350 in­lbs) when attaching the gas piping to the gas valve.

1 - This unit is shipped standard for left or right side

installation of gas piping (or top entry in horizontal

applications). Connect the gas supply piping into
the gas valve. The maximum torque is 800 in lbs
and minimum torque is 350 in lbs when attaching
the gas piping to the gas valve.

2 - When connecting the gas supply piping, consider

factors such as length of run, number of ttings, and

furnace rating to avoid excessive pressure drop.

Table 6 lists recommended pipe sizes for typical

applications.

3 - The gas piping must not run in or through air ducts,

clothes chutes, gas vents or chimneys, dumb
waiters, or elevator shafts.

4 - The piping should be sloped 1/4 inch (6.4 mm) per

15 feet (4.57 m) upward toward the meter from the
furnace. The piping must be supported at proper
intervals [every 8 to 10 feet (2.44 to 3.01 m)] with
suitable hangers or straps. Install a drip leg in
vertical pipe runs to the unit.

5 - A 1/8” N.P.T. plugged tap or pressure post is located

on the gas valve to facilitate test gauge connection.

See gure 31.

6 - In some localities, codes may require the installation

of a manual main shut-off valve and union (furnished
by the installer) external to the unit. The union must
be of the ground joint type.

IMPORTANT

Compounds used on threaded joints of gas piping must

be resistant to the actions of liquied petroleum gases.

NOTE - If emergency shutoff is necessary, shut off the
main manual gas valve and disconnect main power to the
furnace. The installer should properly label these devices.

TABLE 6

Gas Pipe Capacity - ft3/hr (m3/hr)

Nominal

Iron Pipe

Size Inches

(mm)

1/2

(12.7)

3/4

(19.05)

1

(25.4)

1-1/4

(31.75)

1-1/2

(38.1)

2

(50.8)

2-1/2

(63.5)

3

(76.2)

Internal

Diameter

inches

(mm)

.622

(17.799)

.824

(20.930)

1.049

(26.645)

1.380

(35.052)

1.610

(40.894)

2.067

(52.502)

2.469

(67.713)

3.068

(77.927)

10

(3.048)

172

(4.87)

360

(10.19)

678

(19.19)

1350

(38.22)

2090

(59.18)

4020

(113.83)

6400

(181.22)

11300

(319.98)

20

(6.096)

118

(3.34)

247

(7.000)

466

(13.19)

957

(27.09)

1430

(40.49)

2760

(78.15)

4400

(124.59)

7780

(220.30)

30

(9,144)

95

(2.69)

199

(5.63)

374

(10.59)

768

(22.25)

1150

(32.56)

2220

(62.86)

3530

(99.95)

6250

(176.98)

40

(12,192)

81

(2.29)

170

(4.81)

320

(9.06)

657

(18.60)

985

(27.89)

1900

(53.80)

3020

(85.51)

5350

(151.49)

Length of Pipe - feet (m)

50

(15.240)

72

(2.03)

151

(4.23)

284

(8.04)

583

(16.50)

873

(24.72)

1680

(47.57)

2680

(75.88)

4740

(134.22)

60

(18.288)

65

(1.84)

137

(3.87)

257

(7.27)

528

(14.95)

791

(22.39)

1520

(43.04)

2480

(70.22)

4290

(121.47)

70

(21.336)

60

(1.69)

126

(3.56)

237

(6.71)

486

(13.76)

728

(20.61)

1400

(39.64)

2230

(63.14)

3950

(111.85)

80

(24.384)

56

(1.58)

117

(3.31)

220

(6.23)

452

(12.79)

677

(19.17)

1300

(36.81)

2080

(58.89)

3670

(103.92)

NOTE - Capacity given in cubic feet (m3 ) of gas per hour and based on 0.60 specic gravity gas.

90

(27.432)

52

(1.47)

110

(3.11)

207

(5.86)

424

(12.00)

635

(17.98)

1220

(34.55)

1950

(55.22)

3450

(97.69)

100

(30,480)

50

(1.42)

104

(2.94)

195

(5.52)

400

(11.33)

600

(17.00)

1160

(32.844)

1840

(52.10)

3260

(92.31)

Page 21

MANUAL

MAIN SHUT-OFF

VALV E

(With 1/8 in. NPT

Plugged Ta p Shown)

GROUND

JOINT

UNION

Left Side Piping

(Standard)

AUTOMATIC

GAS VALV E

AUTOMATIC

GAS VALV E

MANUAL

MAIN SHUT-OFF

VALV E

(With 1/8 in. NPT

Plugged Ta p

Shown)

GROUND

JOINT

UNION

DRIP LEG

MANUAL

MAIN SHUT-OFF

VALV E

GROUND

JOINT

UNION

DRIP LEG

DRIP LEG

FIELD

PROVIDED

AND INSTALLED

NOTE - BLACK IRON PIPE ONLY TO BE ROUTED INSIDE OF CABINET

FIGURE 25

Horizontal Applications

Possible Gas Piping Configurations

MANUAL

MAIN SHUT-OFF

VALV E

GROUND

JOINT

UNION

DRIP LEG

Right Side Piping

(Alternate)

Horizontal Application

Left-Side Air Discharge

Horizontal Application

Right-Side Air Discharge

FIELD

PROVIDED

AND

INSTALLED

NOTE - BLACK IRON PIPE ONLY TO BE ROUTED INSIDE OF CABINET

FIGURE 26

Page 22

MANUAL

MAIN SHUT-OFF

VALV E

GROUND

JOINT

UNION

DRIP LEG

Leak Check

MANUAL MAIN

SHUT-OFF VALV E

WILL NOT HOLD

NORMAL TEST

PRESSURE

CAP

ISOLATE

GAS VALV E

FURNACE

1/8 NPT PLUG

After gas piping is completed, carefully check all piping

connections (factory- and eld-installed) for gas leaks.

Use a leak detecting solution or other preferred means.

NOTE - If emergency shutoff is necessary, shut off the
main manual gas valve and disconnect the main power
to the furnace. The installer should properly label these
devices.

CAUTION

Some soaps used for leak detection are corrosive to
certain metals. Carefully rinse piping thoroughly after
leak test has been completed. Do not use matches,

candles, ame or other sources of ignition to check for

gas leaks.

The furnace must be isolated by closing its individual man­ual shut-off valve and disconnecting from from the gas
supply system the during any pressure testing of the gas
supply system at pressures greater than 1/2 psig (3.48
kPa, 14 inches w.c.).

WARNING

Fire Hazard. Use of aluminum wire with this product may
result in a re, causing property damage, severe injury

or death. Use copper wire only with this product.

CAUTION

Failure to use properly sized wiring and circuit breaker
may result in property damage. Size wiring and circuit
breaker(s) per Product Specications bulletin (EHB) and

unit rating plate.

The unit is equipped with a eld make-up box on the left

hand side of the cabinet. The make-up box may be moved
to the right side of the furnace to facilitate installation. If
the make-up box is moved to the right side, clip the wire
ties that bundle the wires together. The excess wire must
be pulled into the blower compartment. Secure the excess
wire to the existing harness to protect it from damage.

INTERIOR MAKE-UP BOX INSTALLATION

When testing pressure of gas lines, gas valve must be

disconnected and isolated. See gure 27. Gas valves

can be damaged if subjected to pressures greater than
1/2 psig (3.48 kPa, 14 inches w.c.).

Electrical

IMPORTANT

FIGURE 27

ELECTROSTATIC DISCHARGE (ESD)

Precautions and Procedures

CAUTION

Electrostatic discharge can affect electronic

components. Take precautions to neutralize

electrostatic charge by touching your hand
and tools to metal prior to handling the
control.

WARNING

Electric Shock Hazard. Can cause injury or

death. Unit must be properly grounded in
accordance with national and local codes.

Right Side

BOX

FIGURE 28

Refer to gure 29 for schematic wiring diagram and trou­bleshooting and table 7 and gure 29 for eld wiring.

The power supply wiring must meet Class I restrictions.
Protected by either a fuse or circuit breaker, select circuit

protection and wire size according to unit nameplate.

NOTE - Unit nameplate states maximum current draw.
Maximum over-current protection allowed is 15 AMP.

Holes are on both sides of the furnace cabinet to facilitate
wiring.

Install a separate (properly sized) disconnect switch near

the furnace so that power can be turned off for servicing.
Before connecting the thermostat, check to make sure
the wires will be long enough for servicing at a later date.
Make sure that thermostat wire is long enough to facilitate
future removal of blower for service.

Page 23

Complete the wiring connections to the equipment. Use

the provided unit wiring diagram and the eld wiring dia­gramshown in gure 29. Use 18-gauge wire or larger that

is suitable for Class II rating for thermostat connections.
Electrically ground the unit according to local codes or, in

the absence of local codes, according to the current Na­tional Electric Code (ANSI/NFPA No. 70). A green ground

wire is provided in the eld make-up box.

NOTE - The EL280UH furnace contains electronic com­ponents that are polarity sensitive. Make sure that the fur­nace is wired correctly and is properly grounded.

Accessory Terminals

One line voltage “EAC” 1/4” spade terminal is provided on

the furnace integrated control. See gure 30 for integrated
control conguration. This terminal is energized when the

indoor blower is operating. Any accessory rated up to one
amp can be connected to this terminal with the neutral leg
of the circuit being connected to one of the provided neu­tral terminals. If an accessory rated at greater than one
amp is connected to this terminal, it is necessary to use
an external relay.

One line voltage “HUM” 1/4” spade terminal is provided on

the furnace integrated control. See gure 30 for integrated

control conguration. This terminal is energized in the

heating mode when the combustion air inducer is operat-

ing. Any humidier rated up to one amp can be connected

to this terminal with the neutral leg of the circuit being con­nected to one of the provided neutral terminals.If a hu-

midier rated at greater than one amp is connected to this

terminal, it is necessary to use an external relay relay.

Generator Use - Voltage Requirements

The following requirements must be kept in mind when
specifying a generator for use with this equipment:

• The furnace requires 120 volts + 10% (Range: 108
volts to 132 volts).

• The furnace operates at 60 Hz + 5% (Range: 57 Hz

to 63 Hz).

• The furnace integrated control requires both po­larity and proper ground. Both polarity and proper
grounding should be checked before attempting to
operate the furnace on either permanent or tempo­rary power.

• Generator should have a wave form distortion of
less than 5% total harmonic distortion (THD).

Thermostat

Install the room thermostat according to the instructions
provided with the thermostat. See table 7 for thermostat
designations. If the furnace is being matched with a heat
pump, refer to the FM21 installation instruction or appro­priate dual fuel thermostat instructions.

Indoor Blower Speeds

1 - When the thermostat is set to “FAN ON,” the indoor

blower will run continuously on the low speed when
there is no cooling or heating demand.

2 - When the EL280UH is operating in the high-re or

lowre heating mode, the indoor blower will run on

the corresponding heating speed.

3 - When the EL280UH is operating in the low cool or

the high cool cooling mode, the indoor blower will
run on the corresponding cooling speed.

Page 24

Thermostat

TABLE 7

Field Wiring Applicatuions

DIP Switch Settings and On-Board Links (See figure 30)

W915

DIP Switch 1

Two-Stage

Cooling

W951

Heat Pumps

Wiring Connections

1 Heat / 1 Cool

NOTE - Use DIP

ond-stage heat ON
delay.
OFF10 minutes.
ON-15 minutes.

1 Heat / 2 Cool

NOTE - Use DIP

ond-stage heat ON
delay.
OFF-10 minutes.
ON-15 minutes.

ON Intact Intact

ON Cut Intact

S1

T'STAT

S1

T'STAT

CONTROL

TERM. STRIP

CONTROL

TERM. STRIP

OUTDOOR

UNIT

OUTDOOR

UNIT

Page 25

Thermostat

TABLE 7

Field Wiring Applicatuions

DIP Switch Settings and On-Board Links (See figure 30)

W915

DIP Switch 1

Two-Stage

Cooling

W951

Heat Pumps

Wiring Connections

2 Heat / 2 Cool OFF Cut Intact

2 Heat / 1 Cool OFF Intact Intact

S1

T'STAT

S1

T'STAT

CONTROL

TERM. STRIP

CONTROL

TERM. STRIP

OUTDOOR

UNIT

OUTDOOR

UNIT

Page 26

EL280UH Schematic Wiring Diagram

FIGURE 29

Page 27

DIAGNOSTIC

LEDs

DIP

SWITCHES

TWO-STAGE INTEGRATED CONTROL

1/4” QUICK CONNECT TERMINALS

SENSE = 120 VAC OUTPUT TO FLAME SENSOR

NEUTRALS= 120 VAC NEUTRAL

PARK = DEAD TERMINAL FOR UNUSED BLOWER LEAD
HEAT LOW = 120 VA C OUTPUT TO CIRC BLWR -- LOW HT SPEED

W915

W951

HEAT HIGH/ COOL LOW = 120 VAC OUTPUT TO CIRC BLWR --

COOL HIGH = 120 VAC OUTPUT TO CIRC BLWR -- HIGH COOL SPEED

THERMOSTAT CONNECTIONS (TB1)

ON-BOARD

LINKS

1= ERROR CODE RECALL
H= 24V HUMIDIFIER OUTPUT
L= LENNOX SYSTEM OPERATION MONITOR

1 -- 2 Stage T'stat Selects t/stat type (single or two-stage)

2 -- 2nd Stage Delay Second stage ON delay (single-stage t'stat)

3 & 4 -- Heat Off DelayHeating fan OFF delay

5 -- Cool Off Delay Cooling fan OFF delay

HIGH HEAT AND LOW COOL SPEED

DIP SWITCH FUNCTIONS

NOITCNUF)SE(HCTIWS PID

FIGURE 30

Integrated Contol

EL280UH units are equipped with a two-stage integrated
control. This control manages ignition timing and fan off
delays based on selections made using the control DIP
switches. The control includes an internal watchguard
feature which automatically resets the integrated control
when it has been locked out. After one hour of continuous
thermostat demand for heat, the watchguard will break
and remake thermostat demand to the furnace and auto­matically reset the control to relight the furnace.

DIP Switch Settings

Switch 1 -- Thermostat Selection -- This unit may be

used with either a single-stage or two-stage thermostat.
The thermostat selection is made using a DIP switch
which must be properly positioned for the particular appli­cation. The DIP switch is factory-positioned for use with a
twostage thermostat. If a single-stage thermostat is to be
used, the DIP switch must be repositioned.

a. Select “OFF” for two-stage heating operation controlled by a

two-stage heating thermostat (factory setting);

b. Select “ON” for two-stage heating operation controlled by

a single-stage heating thermostat. This setting provides a
timed delay before second-stage heat is initiated.

Switch 2 -- Second Stage Delay (Used with Single­Stage Thermostat Only) -- This switch is used to de-

termine the second stage on delay when a single-stage
thermostat is being used. The switch is factory-set in the
OFF position, which provides a 10-minute delay before
secondstage heat is initiated. If the switch is toggled to
the ON position, it will provide a 15-minute delay before
secondstage heat is initiated. This switch is only activated
when the thermostat selector jumper is positioned for SIN­GLEstage thermostat use.

Switches 3 and 4 -- Heating Blower-Off Delay -- The
heating blower-on delay of 30 seconds is not adjustable.
The heating blower-off delay (time that the blower oper-

ates after the heating demand has been satised) can be

adjusted by moving switches 3 and 4 on the integrated
control. The unit is shipped from the factory with a heat­ing blower-off delay of 90 seconds. The heating blower
off delay affects comfort and is adjustable to satisfy indi­vidual applications. Adjust the blower off delay to achieve
a supply air temperature between 90° and 110°F at the

exact moment that the blower is de-energized. Longer

off delay settings provide lower supply air temperatures;
shorter settings provide higher supply air temperatures.
Table 8 provides the blower off timings that will result from
different switch settings.

Page 28

TABLE 8

Heating Blower-Off Delay Switch Settings

Blower Off Delay

(Seconds)

60 Off On

90

factory setting

120 On Off

180 On On

Switch 5 -- Cooling Blower-Off Delay -- The cooling
blower-off delay (time that the blower operates after the

cooling demand has been satised) can be adjusted by

moving switch 5 on the integrated control. The switch is
factory- set in the OFF position, which provides a cooling
blower- off delay of 45 seconds. If the switch is toggled to
the ON position, it will provide a 2-second cooling blow­er-off delay

On-Board Link W951 Heat Pump (R to O)

On-board link W951 is a clippable connection between
terminals R and O on the integrated control. W951 must
be cut when the furnace is installed in applications which
include a heat pump unit and a thermostat which features
dual fuel use. If the link is left intact, terminal “O” will re-

main energized eliminating the HEAT MODE in the heat

pump.

On-Board Link W915 2 Stage Compr (Y1 to Y2)

On-board link W915 is a clippable connection between
terminals Y1 and Y2 on the integrated control. W915 must
be cut if two-stage cooling will be used. If the link is not cut
the outdoor unit will operate in second-stage cooling only
and the indoor blower will operate on high cool speed only.

Unit Start-Up

FOR YOUR SAFETY READ BEFORE LIGHTING

Switch 3 Switch 4

Off Off

WARNING

Do not use this furnace if any part has been underwater.

A ood-damaged furnace is extremely dangerous.
Attempts to use the furnace can result in re or explosion.
Immediately call a qualied service technician to inspect

the furnace and to replace all gas controls, control
system parts, and electrical parts that have been wet or
to replace the furnace, if deemed necessary.

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.

CAUTION

Before attempting to perform any service or maintenance,
turn the electrical power to unit OFF at disconnect switch.

BEFORE LIGHTING smell all around the appliance area

for gas. Be sure to smell next to the oor because some
gas is heavier than air and will settle on the oor.

The gas valve on the EL280UH unit will be equipped with
a gas control switch. Use only your hand to move the
switch. Never use tools. If the switch will not turn or if the
control switch will not move by hand, do not try to repair it.

Placing the furnace into operation:

EL280UH units are equipped with an automatic ignition
system. Do not attempt to manually light burners on these
furnaces. Each time the thermostat calls for heat, the
burners will automatically light. The ignitor does not get
hot when there is

WARNING

If you do not follow these instructions exactly, a re or

explosion may result causing property damage, personal
injury or death.

Gas Valve Operation (Figure 31)

1 - STOP! Read the safety information at the beginning

of this section.
2 - Set the thermostat to the lowest setting.
3 - Turn off all electrical power to the unit.
4 - This furnace is equipped with an ignition device

which automatically lights the burners. Do not try to

light the burners by hand.
5 - Remove the upper access panel.
6 - Move switch on gas valve to OFF. Do not force. See

gure 31.

7 - Wait ve 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 next step

Page 29

WHITE RODGERS GAS VALVE

INLET PRESSURE POST

GAS VALV E SHOWN IN ON POSITION

MANIFOLD

PRESSURE TAP

HIGH FIRE ADJUSTMENT

SCREW

(under cap)

FIGURE 31

8 - Move switch on gas valve to ON. Do not force. See

gure 31.

9 - Replace the upper access panel.
10 - Turn on all electrical power to to the unit.
11 - Set the thermostat 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 the appliance will not operate, follow the

instructions “Turning Off Gas to Unit” and call your
service technician or gas supplier.

Turning Off Gas to Unit

1 - Set the thermostat to the lowest setting.
2 - Turn off all electrical power to the unit if service is to

be performed.
3 - Remove the upper access panel.
4 - Move switch on gas valve to OFF. Do not force.
5 - Replace the upper access panel.

Failure To Operate

If the unit fails to operate, check the following:

1 - Is the thermostat calling for heat?
2 - Are access panels securely in place?
3 - Is the main disconnect switch closed?
4 - Is there a blown fuse or tripped circuit breaker?
5 - Is the lter dirty or plugged? Dirty or plugged lters

will cause the limit control to shut the unit off.
6 - Is gas turned on at the meter?
7 - Is the manual main shut-off valve open?
8 - Is the gas valve ON/OFF switch in the ON position?
9 - Is the unit ignition system in lock out? If the unit locks

out again, call the service technician to inspect the

unit for blockages.
10 - Is pressure switch closed? Obstructed ue will

cause unit to shut off at pressure switch. Check ue

and outlet for blockages.
11 - Are ame rollout switches tripped? If ame rollout

switches are tripped, call the service technician for

inspection.

Gas Pressure Adjustment

Gas Flow (Approximate)

TABLE 9

GAS METERING CLOCKING CHART

EL280

Unit

-045 80 160 200 400

-070 55 110 136 272

-090 41 82 102 204

-110 33 66 82 164

-135 27 54 68 136

Natural 1000 btu/cu ft LP 2500 btu cu/cu ft

Seconds For One Revolution

1 cu ft dial 2 cu fr dial 1 cu ft Dial 2 cu ft Dial

Furnace should operate at least 5 minutes before check­ing gas ow. Determine time in seconds for two revolu­tions of gas through the meter. (Two revolutions assures
a more accurate time.) Divide by two and compare to time
in table 9 below. If manifold pressure matches table 11

and rate is incorrect, check gas orices for proper size and

restriction. Remove temporary gas meter if installed.

NOTE - To obtain accurate reading, shut off all other gas
appliances connected to meter.

Supply Pressure Measurement

An inlet post located on the gas valve provides access

to the supply pressure. See gure 31. Back out the 3/32”

hex screw one turn, connect a piece of 5/16” tubing and
connect to a manometer to measure supply pressure. See
table 11 for supply line pressure.

Manifold Pressure

A manifold pressure post located on the gas valve pro­vides access to the manifold pressure. See gure 31.
Back out the 3/32 hex screw one turn, connect a piece
of 5/16” tubing and connect to a manometer to measure
manifold pressure.

NOTE - Pressure test adapter kit (10L34) is available from
Lennox to facilitate manifold pressure measurement.

1 - Connect test gauge to manifold pressure post

(gure 31) gas valve.

2 - Ignite unit on high re and let run for 5 minutes to

allow for steady state conditions.

3 - After allowing unit to stabilize for 5 minutes, record

manifold pressure and compare to value given in table

11.

4 - If necessary, make adjustments. Figure 31 shows

location of high re adjustment screw.

5 - If an adjustment is made on high re, re-check

manifold pressure on low re. Do not adjust low re
manifold pressure. If low re manifold pressure is
more than 1/2” above or below value specied in

table 11, replace valve.

6 - soon as an accurate reading has been obtained.

Turn the supply and manifold 3/32” hex screw one
revolution back into the gas valve.

7 - Start unit and perform leak check. Seal leaks if

found.

Page 30

Proper Combustion

Furnace should operate minimum 15 minutes with correct
manifold pressure and gas ow rate before checking com­bustion. Table 10 shows acceptable combustion for ALL
EL280UH models. The maximum carbon monoxide

reading should not exceed 100 ppm

High Altitude

The manifold pressure may require adjustment and com­bustion air pressure switch may need replacing to ensure
proper combustion at higher altitudes. Refer to table 11
for manifold pressure and table 12 for pressure switch
change and gas conversion kits.

TABLE 10

Firing Rate

High Fire 6.0 - 7.5 7.0 - 8.5

Low Fire 5.0 - 6.5 5.8 - 7.3

CO2% Nat CO2% LP

TABLE 11

Manifold Pressure Settings

Supply Line

Pressure

in. w.g.

Unit

Input

Gas

Manifold Pressure in.

wg. 0 - 4500 ft

Manifold Pressure in.

wg. 4500 - 7500 ft

Manifold Pressure in. wg.

7500 - 10,000 ft

2

Low Firer High Fire Low Fire High Fire Low Fire High Fire Min Max

070

090

110

135

1

This is the only permissible derate for these units.

2

Natural gas high altitude orice kit required.

3

A natural to L.P. propane gas changeover kit is necessary to convert this unit. Refer to the changeover kit installation instruction for the conversion

procedure.

NOTE - Units may be installed at altitudes up to 4500 ft. above sea level without modications.

Natural 1.7 3.5 1.6 3.4 1.7 3.5 4.5 13.0

LP/propane

3

4.9 10.0 4.9 10.0 4.9 10.5 11.0 13.0

Natuarl 1.7 3.5 1.5 3.2 1.7 3.5 4.5 13.0

LP/propane

3

4.9 10.0 4.9 10.0 4.9 10.0 11.0 13.0

Natural 1.7 3.5 1.5 2.8 1.7 3.5 4.5 13.0

LP/propane

Natural

LP/propane

3

4.9 10.0 4.9 10.0 4.9 10.0 11.0 13.0

1.7 3.5 1.5 2.8 1.7 3.5 4.5 13.0

3

4.9 10.0 4.9 10.0 4.9 10.0 11.0 13.0

TABLE 12

Pressure Switch and Gas Conversion Kits at all Altitudes

High Altitude Pressure Switch Kit

Unit Input

0-4500 ft 4501- 7500 ft 7501-10,000 ft 7501-10,000 ft 0-7500 ft

070

090 91W53 73W35

110 91W53 73W35

135 73W33 73W34

NOTE - A natural to L.P. propane gas changeover kit is necessary to convert this unit. Refer to the changeover kit installation instruc­tion for the conversion procedure.

No Change

91W53 73W35

High Altitude

Natural Gas Kit

73W37 11K51 11K46 77W09

LP/Propane Gas Kit

7501 - 10,000

ft

LP/Propane to

Natural Kit

0 -7500 ft

Page 31

Other Unit Adjustments

Primary and Secondary Limits

The primary limit is located on the heating compartment
vestibule panel. The secondary limits (if equipped) are lo­cated in the blower compartment, attached to the back
side of the blower. These auto reset limits are factory-set
and require no adjustment.

Flame Rollout Switches

Electrical

1 - Check all wiring for loose connections.
2 - Check for the correct voltage at the furnace (furnace

operating). Correct voltage is 120VAC + 10%.

3 - Check amp-draw on the blower motor with inner

blower panel in place.

Unit Nameplate__________Actual__________

Blower Speeds

This manually reset switches are located on the bafe

plate in the burner assembly.

Pressure Switch

The pressure switch is located in the heating compartment
adjacent to the combustion air inducer. The switch checks
for proper combustion air inducer operation before allow­ing ignition trial. The switch is factory-set and requires no

adjustment.

Temperature Rise

After the furnace has been started, and supply and return

air temperatures have been allowed to stabilize, check the

temperature rise. If necessary, adjust the blower speed
to maintain the temperature rise within the range shown
on the unit nameplate. Increase the blower speed to de­crease the temperature. Decrease the blower speed to
increase the temperature rise. Failure to adjust the tem­perature rise may cause erratic limit operation.

Fan Control

The fan-on time of 30 seconds is not adjustable. The heat
fan-off delay (amount of time that the blower operates af-

ter the heat demand has been satised) may be adjusted
by changing DIP switches 3 and 4. See gure 32 and table

8. The unit is shipped with a factory fan-off delay setting
of 90 seconds. The fan-off delay affects comfort and is
adjustable to satisfy individual applications. Adjust the fan­off delay to achieve a supply air temperature between 90°

and 110°F at the moment that the blower is de-energized.

Longer off delay settings provide lower return air tempera­tures; shorter settings provide higher return air tempera­tures.

NOTE - Do not secure the electrical conduit directly to the
air ducts or structure.

HEAT FAN‐OFF TIME IN SECONDS

60sec.

12345 12345

90sec.

Follow the steps below to change the blower speeds.

1 - Turn off electrical power to furnace.
2 - Remove blower access panel.
3 - Disconnect existing speed tap at integrated control

speed terminal.

NOTE - Termination of any unused motor leads must be

insulated.

4 - Place unused blower speed tap on integrated

control “PARK” terminal or insulate.

5 - Refer to blower speed selection chart on unit wiring

diagram for desired heating or cooling speed. See
Blower performance data beginning on the next
page.

6 - Connect selected speed tap at integrated control

speed terminal.
7 - Resecure blower access panel.
8 - Turn on electrical power to furnace.
9 - Recheck temperature rise.

Electronic Ignition

The integrated control has an added feature of an internal
Watchguard control. The feature serves as an automat­ic reset device for integrated control lockout caused by
ignition failure. This type of lockout is usually due to low
gas line pressure. After one hour of continuous thermostat
demand for heat, the Watchguard will break and remake
thermostat demand to the furnace and automatically reset
the integrated control to begin the ignition sequence.

Heating Sequence of Operation

When there is a call for heat, the integrated control runs a
self check. The control checks for S10 primary limit, S21
secondary limit (s) and S47 rollout switch normally closed
contacts. The control also checks for S102 high heat and
S128 low heat prove switch normally open contacts. Once
self check is complete and all safety switches are opera­tional, heat call can continue.

Two-Stage Thermostat, Two Stage Heat. Dip Switch
set at “TWO”.

120sec.

12345 12345

To adjust fan-off timing, flip dip switch to desired setting.

180sec.

FIGURE 32

1 - SureLight® control energizes combustion air inducer

B6 on low heat speed. Combustion air inducer runs

until S128 low heat prove switch contacts close

(switch must close within 2 1/2 minutes or control

goes into Watchguard Pressure Switch mode.

High heat prove switch S102 may also close). A 15

second pre-purge follows once S128 closes.

Page 32

NOTE - If the low re pressure switch does not close the
combustion air inducer will switch to high re. After a 15
second pre-purge the high re pressure switch will close
and the unit will begin operation on high re. After 10 to
20 seconds of high re operation the unit will switch to low
re.

NOTE - If the furnace is operating on continuous fan mode
(terminal “R” and “G” are energized), the combustion air
inducer will energize on high speed, the gas valve will en­ergize on second-stage heat and the furnace will operate
on high re. Furnace will stay on high re for 60 seconds
then switch to low re.

2 - SureLight control begins 20 second ignitor warm up

period.

3 - Gas valve opens on rst stage for a 4 second trial

for ignition. Ignitor stays energized during the trial or
until ame sensed.

4 - Flame is sensed, gas valve remains on rst stage

heat, ignitor de-energizes.

5 - After 30 second delay, indoor blower B3 is energized

on low heat speed.

The furnace will stay in this mode until rst stage
demand is satised OR a second stage heat
demand is initiated.

6 - Second stage heat demand initiated. A 30 second

second stage recognition period begins.

7 - The combustion air inducer ramps up to high heat

speed.

8 - S102 high heat prove switch closes and the gas

valve energizes second stage heat.

9 - B3 indoor blower switches to high heat speed.

Single-Stage Thermostat, Two Stage Heat. Dip
Switch set at “SINGLE”

1 - SureLight control energizes combustion air inducer

B6 on low heat speed.

Combustion air inducer runs until S128 low heat prove
switch contacts close (switch must close within 2 1/2
minutes or control goes into Watchguard Pressure
Switch mode. High heat prove switch S102 may also
close). A 15 second pre-purge follows once S128 clos­es.

NOTE - If the low re pressure switch does not close the
combustion air inducer will switch to high re. After a 15
second pre-purge the high re pressure switch will close
and the unit will begin operation on high re. After 10 to
20 seconds of high re operation the unit will switch to low
re.

NOTE - If the furnace is operating on continuous fan mode
(terminal “R” and “G” are energized), the combustion air
inducer will energize on high speed, the gas valve will en­ergize on second-stage heat and the furnace will operate
on high re. Furnace will stay on high re for 60 seconds
then switch to low re.

2 - SureLight control begins 20 second ignitor warm up

period.
3 - Gas valve opens on rst stage for a 4 second trial

for ignition. Ignitor stays energized during the trial or

until ame sensed.
4 - Flame is sensed, gas valve remains on rst stage

heat, ignitor de-energizes.

5 - After 30 second delay, indoor blower B3 is energized

on low heat speed.
6 - A 10 minute (factory set) or 15 minute (eld set)

second stage heat delay period begins.
7 - After the delay the combustion air inducer ramps up

to high heat speed.
8 - S102 high heat prove switch closes and the gas

valve energizes second stage heat.

9 - B3 indoor blower switches to high heat speed.

Page 33

Service

WARNING

ELECTRICAL SHOCK, FIRE,

OR EXPLOSION HAZARD.

Failure to follow safety warnings exactly could result in
dangerous operation, serious injury, death or property
damage.

Improper servicing could result in dangerous operation,
serious injury, death, or property damage. Before
servicing, disconnect all electrical power to furnace.

When servicing controls, label all wires prior to
disconnecting. Take care to reconnect wires correctly.

Verify proper operation after servicing.

WARNING

The blower access panel must be securely in place when
the blower and burners are operating. Gas fumes, which
could contain carbon monoxide, can be drawn into living
space resulting in personal injury or death.

Annual Furnace Maintenance

At the beginning of each heating season, and to comply
with the Lennox Limited Warranty, your system should
be checked as follows:

1 - Check wiring for loose connections, voltage at

indoor unit and amperage of indoor motor.

2 - Check the condition of the belt and shaft bearings

if applicable.
3 - Inspect all gas pipe and connections for leaks.
4 - Check the cleanliness of lters and change if

necessary (monthly).
5 - Check the condition and cleanliness of burners and

heat exchanger and clean if necessary.
6 - Check the cleanliness of blower assembly and

clean the housing, blower wheel and blower motor

if necessary
7 - Inspect the combustion air inducer and clean if

necessary.
8 - Evaluate the heat exchanger integrity by inspecting

the heat exchanger per the AHRI heat exchanger
inspection procedure. This procedure can be
viewed at www.ahrinet.org

9 - Ensure sufcient combustion air is available to the

furnace. Fresh air grilles and louvers (on the unit
and in the room where the furnace is installed)

must be properly sized, open and unobstructed to

provide combustion air.

10 - Inspect the furnace venting system to make sure

it is in place, structurally sound, and without holes,
corrosion, or blockage. Vent system must be free
and clear of obstructions and must slope upward
away from the furnace . Vent system should be
installed per the National Fuel Gas Code.

11 - Inspect the furnace return air duct connection to

ensure the duct is sealed to the furnace. Check for
air leaks on supply and return ducts and seal where
necessary.

12 - Check the condition of the furnace cabinet insulation

and repair if necessary.

13 - Perform a complete combustion analysis during the

furnace inspection to ensure proper combustion
and operation. Consult Service Literature for proper
combustion values.

14 - Verify operation of CO detectors and replace

batteries as required.

Perform a general system test. Turn on the furnace to
check operating functions such as the start-up and shut­off operation.

1 - Check the operation of the ignition system, inspect

and clean ame sensor. Check microamps before

and after. Check controls and safety devices (gas

valve, ame sensor, temperature limits). Consult

Service Manual for proper operating range. Thermal

Limits should be checked by restricting airow and

not disconnecting the indoor blower. For additional
details, please see Service and Application Note
H049.

2 - Verify that system total static pressure and airow

settings are within specic operating parameters.

3 - Clock gas meter to ensure that the unit is operating

at the specied ring rate. Check the supply

pressure and the manifold pressure. On two-stage
gas furnaces check the manifold pressure on high

re and low re. If manifold pressure adjustment is

necessary, consult the Service Literature for unit

specic information on adjusting gas pressure.

Not all gas valves are adjustable. Verify correct
temperature rise.

Page 34

Cleaning the Burners

NOTE - Use papers or protective covering in front of the
furnace during cleaning.

1 - Turn off both electrical and gas power supplies to

furnace.
2 - Label the wires from gas valve, rollout switches,

primary limit switch and make-up box then

disconnect them.
3 - Disconnect gas supply piping. Remove the screw

securing the burner box cover and remove cover.

Remove the four screws securing the burner

manifold assembly to the vestibule panel and

remove the assembly from the unit.

4 - To clean burners, run a vacuum cleaner with a soft

brush attachment over the face of burners. Visually
inspect inside the burners and crossovers for any
blockage caused by foreign matter. Remove any
blockage. Figure 33 shows burner detail.

5 - Reinstall burner box, manifold assembly and burner

box cover.

6 - Re-install gas supply and turn on electrical pwer to

furnace.

Rollout

Switches

Sensor

Ignitor

BURNER REMOVAL

Retention Rings

Cross Over

Manifold And Gas Valve

FIGURE 33

Page 35

Repair Parts List

The following repair parts are available through independent Lennox dealers. When ordering parts, include the complete
furnace model number listed on the CSA International nameplate -- Example: EL280UH045P24A-01. All service must be
performed by a licensed professional HVAC installer (or equivalent), service agency, or gas

supplier.

Cabinet Parts

Main access panel
Blower panel
Top cap

Control Panel Parts

Transformer
Integrated control
Door interlock switch
Circuit breaker

Blower Parts

Blower wheel
Blower housing
Motor
Motor mounting frame
Motor capacitor
Blower housing cutoff plate

Heating Parts

Flame sensor
Heat exchanger assembly
Gas manifold
Combustion air inducer
Gas valve
Main burner cluster

Main burner orices

Pressure switch
Ignitor
Primary limit control
Flame rollout switch (s)
Secondary limit

Page 36

Start-Up & Performance Check List

Unit Model Number_______________

UNIT SET UP

(typical)

2

2

1

GAS SUPPLY

1

Natural Gas

Piping Connections Tight

Leak Tested

Serial Number___________________

Line Voltage

5

Gas Supply Pressure

1

LP/Propane Gas

SUPPLY

AIR

upflow furnace shown

3

Filter

RETURN

RETURN

AIR

4

3

DUCT SYSTEM

AIR

SUPPLY AIR DUCT

Sealed

Insulated (if necessary)

Supply Line Pressure “ W.C.________

Registers Open and Unobstructed

RETURN DUCT

VENT / EXHAUST PIPE

2

Secure to Unit

Elbows Secured to Pipe

Roof Flashing (water tight)

Sealed

Filter Installed and Clean

Grilles Unobstructed

INTEGRATED CONTROL

4

Vent Pipe Supported

DIP Switches Set (if applicable)

Appropriate Links in Place (if applicable)

5

VOLTAGE CHECK

Supply Voltage _____

Electrical Connections Tight

Page 37

UNIT OPERATION

(typical)

Combustion CO

2

Gas Manifold Pressure

1

Blower Motor Amps

3

7

2

Thermostat

HEATING MODE

GAS MANIFOLD PRESSURE “W.C._____

1

2

COMBUSTION SAMPLE CO

INDOOR BLOWER AMPS______

3

2%______

CO PPM_______

SUPPLY

AIR

6

upflow furnace shown

RETURN

RETURN

AIR

AIR

INDOOR BLOWER AMPS______

3

TEMPERATURE DROP

4

Return Duct Temperature _________
Supply Duct Temperature

Temperatures

4

Filter

Duct Static

5

COOLING MODE

_

_______

Temperature Drop = _________

TEMPERATURE RISE

4

Supply Duct Temperature ________
Return Duct Temperature

Temperature Rise = ________

TOTAL EXTERNAL STATIC (dry coil)

5

Supply External Static _______

_

_____

TOTAL EXTERNAL STATIC (dry coil)

5

Supply External Static _______

Return External Static + ______

Total External Static = _______

DRAIN LINE

6

Leak Free

Return External Static + ______

7

Total External Static = _______

THERMOSTAT

Adjusted and Programmed

Operation Explained to Owner

Contractor's: Name_________________________Telephone_____________Checklist Completed____________________

Job Address_____-________________________________Technician's Name___________________________________

Page 38