Lennox G43UF User Manual

G A S F U R N A C E S

G43UF

MERIT® SERIES

Up−Flow

E N G I N E E R I N G D A T A Bulletin No. 210394

Supersedes December 2004

August 2005

MODEL NUMBER IDENTIFICATION

G 43 24−B− 045

Unit Type

G = Gas Furnace

Series

43 = 90% Minimum AFUE

Configuration

UF = Up−Flow

Nominal Add−On Cooling Capacity

24 = 2 tons (7.0 kW)

36 = 3 tons (10.5 kW)

48 = 4 tons (14.10 kW)

60 = 5 tons (17.5 kW)

UF

AFUE − up to 92.1%

Input − 44,000 to 132,000 Btuh

Nominal Add−on Cooling − 2 to 5 Tons

Nominal Gas Heat Input

045 = 44,000 Btuh (12.9 kW)
070 = 66,000 Btuh (19.3 kW)
090 = 88,000 Btuh (25.8 kW)
110 = 110,000 Btuh (32.2 kW)
135 = 132,000 Btuh (38.7 kW)

1

Cabinet Width

B = 17−1/2 in. (445 mm)
C = 21 in. (533 mm)
D = 24−1/2 in. (622 mm)

1

Indoor coils with the same letter designation

will physically match the furnace.

FEATURES

CONTENTS

Blower Data Pages 13−15. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Dimensions Pages 9−12. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Exhaust Pipe Venting Information Page 7. . . . . . . . . . . . . . . . . . .

Features and Options Pages 2−4. . . . . . . . . . . . . . . . . . . . . . . . . .

Filter Air Resistance Page 8. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

High Altitude Information Page 8. . . . . . . . . . . . . . . . . . . . . . . . . .

Installation Clearances Page 8. . . . . . . . . . . . . . . . . . . . . . . . . . . .

Model Number Identification Page 1. . . . . . . . . . . . . . . . . . . . . . .

Optional Accessories Selection table Page 6. . . . . . . . . . . . . . . .

Specifications Page 5. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

WARRANTY

Duralok Plus® Aluminized Steel Heat Exchanger − Twenty
years limited warranty.
All other covered components − Five years limited warranty.

Refer to Lennox Equipment Limited Warranty certificate
included with equipment for details.

APPROVALS

Units certified by CSA International and ratings are certified by
GAMA.
Units tested and rated according to US DOE test procedures and
FTC labeling regulations.
Blower data from unit tests conducted in Lennox Laboratory air
test chamber.
Approved by the California Energy Commission and meets
California Seasonal Efficiency requirements and California
Nitrogen Oxides (NOx) Standards.

NERGY STAR

E
help save money on utility bills, and help protect the
environment.
ISO 9001 Registered Manufacturing Quality System.

APPLICATIONS

Input capacities of 44,000, 66,000, 88,000, 110,000, and
132,000 Btuh (12.9, 19.3, 25.8, 32.2, and 38.7 kW).
Energy efficiency (AFUE) up to 92.1%.
Compact cabinet with either side or bottom return air entry.
Lennox add-on indoor coils, high−efficiency air cleaners and
humidifiers can easily be added to furnace.
Shipped factory assembled with all controls installed and wired.
Each unit factory test operated to ensure proper operation.

DIRECT VENT / NON−DIRECT VENT

Furnace can be installed in either Direct Vent or Non−Direct
applications. In Direct Vent applications, combustion air is
supplied from outdoors and flue gases are discharged outdoors.
In Non−Direct Vent applications, combustion air is supplied from
indoors and flue gases are discharged outdoors.

OPTIONS

Termination Kits

Facilitates installation of combustion air intake pipe and flue
exhaust pipe.
Refer to venting table in this bulletin to determine pipe size
needed and proper termination kit required.
See Specifications table and dimension drawings.

Termination Kit − Concentric − Direct Vent Applications
Only

1−1/2, 2, or 3 inch (38, 51, or 76 mm) kit contains concentric
termination assembly, reducer bushing and 45 degree elbow.
Kit requires single hole penetration of roof or wall for installation.
Roof Termination Flashing Kit is available for use with 1−1/2 and
2 inch Kits.
CSA certified.

®

certified units are designed to use less energy,

B

D

E

N

K

F

C

G

P

O

H

L

J

I

M

Termination Kits − Wall Assembly

Close Couple − Direct Vent Applications Only

2 or 3 inch (51 or 76 mm) kit consists of close-couple,
side-by-side PVC piping with galvanized steel wall cover plate
for sealing and isolating piping penetration of the wall.
Piping spacing and length is sized for proper wall installations.
CSA certified.

Close Couple WTK − Direct Vent Applications Only

2 or 3 inch (51 or 76 mm) kit contains one insulated faceplate,
one insulated exhaust pipe, elbow and fittings.

Wall Ring − Direct or Non−Direct Vent

2 inch (51 mm) kit contains 2 stainless steel outside seal caps, 2
galvanized steel inside seal caps, 4 seal rings for the caps and
18 inch (457 mm) insulation sleeve for sealing and isolating
intake and exhaust piping penetration of wall.
Maintain a maximum of 6 inches (152 mm) between the inlet
and outlet openings in the installation of the pipes.

Roof Termination Flashing Kit − Direct or Non−Direct Vent

2 or 3 inch (51 or 76 mm) kit contains two neoprene rubber roof
flashings for vertical venting through a roof.
Vent pipe and insulation not furnished. Each kit contains
enough parts for two non−direct vent installations.
Also available for use with 1−1/2 inch (use 2 inch flashing) and 2
inch (use 3 inch flashing) Concentric Vent Termination Kits used
in vertical venting rooftop applications.

G43UF / Page 2

FEATURES

HEATING SYSTEM

B

Lennox Duralok Plus

Lennox developed heat exchanger assembly consists of primary
heat exchanger and secondary condenser coil assembly.
Main 3-pass clamshell type heat exchanger constructed of
heavy−gauge, aluminized steel.
Designed for normal expansion and contraction.
Crimped seam design and construction provides maximum
efficiency and minimum resistance to airflow.
Secondary heat exchanger condenser coil constructed of

C

aluminum fins fitted to stainless steel tubes.
Coil is factory tested for leaks.
Condensate drain header box assembly located on front of coil.
Compact size of complete heat exchanger assembly permits low
overall design of furnace cabinet.
All components mounted in a heavy−gauge steel frame.
Heat exchanger assembly has been laboratory life cycle tested.

Lennox Designed Header Box

Header box on end of condenser coil collects flue condensate for
disposal through condensate collars.
Hose connects the header box drains to the condensate collars.
The condensate collars are located on each side of the cabinet
for easy field installation of condensate drain trap. Only one
collar is used, the other is plugged.
Condensate drain trap is included with the unit for field installation.

Lennox Designed Flue Condensate Trap Assembly

Condensate trap assembly is mounted outside the conditioned
air stream.
Assembly can be mounted on either side of cabinet. See
Installation Instructions.
Connection can be made with field provided 1/2 in. PVC pipe, 3/4 in.
PVC coupling, or 1−1/4 in. OD x 1 in. ID vinyl tubing with hose clamp.
Easy to clean and winterize.

Inshot Burners

D

Aluminized steel inshot burners provide efficient, trouble−free
operation.
Burner venturi mixes air and gas in correct proportion for proper
combustion.
Burner assembly is removable from the unit as a single
component for ease of service.

Hot Surface Mini−Nitride Ignitor

Unique, non−porous, high strength proprietary ceramic material
provides long life and trouble−free maintenance.
Low mass element provides fast heat−up and consistent igniter
temperature with low power usage.
Cemented to alumina block for positive mounting and protection
against current leakage.
High temperature Teflon
dependable operation.

Gas Control Valve

E

24 volt redundant combination gas control valve combines
manual shut off valve (On−Off), automatic electric valve (dual)
and gas pressure regulation into a compact combination control.

Combustion Air Inducer

F

Shaded pole heavy−duty blower prepurges heat exchanger and
safely vents flue products.
Pressure switch proves blower operation before allowing gas

G

valve to open.
Operates only during heating cycle.

Limit Control

Automatic reset, primary limit is accurately located.
Factory installed on vestibule panel on all units.

Flame Rollout Switch

Manual reset switches are factory installed on burner box.
Switch provides protection from abnormal operating conditions.

®

Heat Exchanger Assembly

®

insulated ignition lead wires for

OPTIONS

High Altitude Orifice Kit − Natural Gas Only

Required for all natural gas models for proper unit operation at
altitudes of 7501 to 10,000 feet (2286 to 3048 m).
Proper orifice for LPG/Propane models is included with
LPG/Propane Conversion Kit.

High Altitude Pressure Switch Kit

Required on certain units for proper unit operation on
installations above 4,500 ft. (1372 m).

LPG/Propane Conversion Kit

Required for field changeover from natural gas to LPG/Propane.

CONTROLS

Integrated Furnace Control Board

H

Solid−state board contains all necessary controls and relays to
operate furnace.
Combustion air inducer is controlled by board. Prior to ignition, a
pre−purge cycle for 15 seconds is initiated. After the main
burners are turned off, a post−purge cycle for 5 seconds is run.
Ignition control board continuously monitors line voltage and
maintains the igniter power at a constant level to provide
consistent lighting and maximum igniter life.
Electronic flame sensor control assures safe and reliable operation.
Should loss of flame occur, flame sensor controls will initiate 4
attempts at re−ignition before locking out unit operation for 60
minutes.
Watchguard type circuit automatically resets ignition controls
after one hour of continuous thermostat demand after unit
lockout, eliminating nuisance calls for service.
Fan control consists of adjustable blower timed−off delay (60, 90,
120, 180 seconds − factory setting 90 seconds) and fixed blower
timed−on delay (45 seconds).
For air−conditioning applications, blower is automatically
energized on thermostat demand for cooling.
Two accessory terminals furnished for additional power supply

I

requirements for 120 volt (less than 1 amp) power humidifiers and
powered air cleaners.
Ignition control has two LED’s to indicate status and as an aid in
troubleshooting.

24 Volt Transformer

J

Furnished and factory installed in control box.
40VA transformer has fuse wired in series.

Field Wiring Make-up Box

K

Furnished for line voltage wiring.
Factory installed internally on left side of furnace.
Box may be installed internally or externally on either side of
furnace.

OPTIONS

Thermostat

See Thermostat bulletins in Controls section and Lennox Price
Book for a complete list of thermostats.

Twinning Kit

Required to operate two furnaces simultaneously.
Kit consists of twinning control and two fan sensors.

BLOWER

Multi-speed, direct drive blower.

L

Statically and dynamically balanced.
Resiliently mounted.

Blower assembly slides out of unit for servicing.

M

Blower speeds are easily changed on the integrated furnace
control board. See blower performance tables.

G43UF / Page 3

FEATURES

FILTER (NOT FURNISHED)

Filter and provisions for external mounting must be field
provided.

OPTIONS

Air Filter and Rack Kit for Side Return Air Applications
(Not for use with RAB Return Air Base)

Washable or vacuum cleanable polyurethane frame type filter
and external side return air rack available for field installation.
Available in single and ten pack kits.
Rack has filter door for easy filter servicing.
Flanges on rack allow easy duct connection.
Field installs on either side of unit cabinet.
See dimension drawing.

EZ Filter Base for Bottom Return Air Applications

Hinged door with thumbscrew for easy filter access.
Uses standard size filters (field provided).

CABINET

Low−profile, narrow width cabinet allows easy installation.
Heavy−gauge, cold rolled steel construction.
Pre−painted cabinet finish.
Flanges provided on supply air opening for ease of plenum
connection or alignment with indoor coil.
Cabinet is insulated with foil faced insulation on sides and back

N

of heating compartment.
Complete service access.

O

Safety interlock switch automatically shuts off power to unit
when blower compartment access door is removed.
Gas piping and electrical inlets are provided in both sides of cabinet.

P

Return Air Entry:

For bottom return−air entry, remove furnished bottom seal panel
from cabinet.
For side return−air entry, corners are marked on either side of
cabinet for return air cut−outs. On furnaces with side return air
and condensate trap on the same side of the cabinet, a field
fabricated transition or RAB is required to use an IAQ product
higher than 14−3/16 in. (360 mm) when installed next to the unit
and serviced from the front. IAQ products higher than 20 in. (508
mm) require a field fabricated transition. See dimension
drawings.

NOTE − 60C and 60D size 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 filter, required to
maintain proper air velocity.

2. Single side return air with optional RAB Return Air Base.

3. Bottom return air.

4. Return air from both sides.

5. Bottom and
See Blower Performance Tables for additional information.

Coil Match−up

All furnaces exactly match C33 and CX34 cased up−flow indoor
coils with same letter designation in model number. No adaptor
required. Engaging holes furnished on cabinet for alignment.
C33 uncased coils match furnaces without any overhang but
require an optional adaptor base or field fabricated transition to
match furnace opening. See C33 coil bulletin for additional
information.

one side return air.

OPTIONS

Condensate Drain Heat Cable Kits

Self-limiting wattage heat cable prevents condensate drain from
freezing in unconditioned areas.
Available in 6, 24 or 50 ft. (1.8, 7.3, or 15.2 m) lengths.
Heat Cable Tape:

66 ft. (20 m) length, 1/2 in. (13 mm) wide fiberglass.
60 ft. (18 m) length, 2 in. (51 mm) wide aluminum foil.

Condensate Trap Alternate Location Kit

Allows condensate drain to be installed on the opposite side of
the furnace from the exhaust venting (up−flow applications only).

RAB Return Air Base

On furnaces with side return air and condensate trap on the
same side of the cabinet, a field fabricated transition or RAB is
required when installing an IAQ product higher than 14−3/16 in.
(360 mm) when installed next to the unit and serviced from the
front. IAQ products higher than 20 in. (508 mm) require a field
fabricated transition.
Must be used for 60C and 60D models with air volumes over
1800 cfm (850 L/s) in up−flow applications when only one side
return is required.
Cabinet is pre−painted steel to match the furnace.
See Dimension Drawing.

G43UF / Page 4

SPECIFICATIONS

Gas
Heating

ModelNo. G43UF

−24B−045

Performance

Input− Btuh (kW) 44,000 (12.9) 66,000 (19.3) 66,000 (19.3) 88,000 (25.8) 88,000 (25.8)

Output− Btuh (kW) 40,300 (11.8) 61,000 (17.9) 62,000 (18.2) 82,000 (24.0) 81,000 (23.7)

Temperature rise range − F (C) 30 − 60

(18 − 36)

1

AFUE 92.1% 90.0% 92.1% 92.1% 90.0%

Highstatic(CSA)− in.w.g. (Pa) .50 (124) .50 (124) .50 (124) .50 (124) .50 (124)

Connections
in.

Condensate Drain Trap (PVC pipe) − i.d. 1/2 1/2 1/2 1/2 1/2

Intake / Exhaust Pipe (PVC) 2 / 2 2 / 2 2 / 2 2 / 2 2 / 2

with field supplied (PVC coupling) − o.d. 3/4 3/4 3/4 3/4 3/4

hose with hose clamp − i.d. x o.d. 1−1/4 x 1 1−1/4 x 1 1−1/4 x 1 1−1/4 x 1 1−1/4 x 1

GaspipesizeIPS 1/2 1/2 1/2 1/2 1/2

Indoor
Blower

Wheel nominal diameter x width −in.

(mm)

10 x 7

(254 x 178)

Motoroutput − hp (W) 1/5 (149) 1/5 (149) 1/3 (249) 1/3 (249) 1/3 (249)

Tons(kW) ofadd−oncooling 1.5 − 2

(5.3 − 7.0)

Air Volume Range − cfm (L/s) 465 − 1125

(220 − 530)

ShippingData − lbs. (kg) − 1 package 132 (60) 141 (64) 146 (66) 162 (74) 162 (74)

Electricalcharacteristics 120 volts − 60 hertz − 1 phase (less than 12 amps)

G43UF

−24B−070

50 − 80

(28 − 44)

10 x 7

(254 x 178)

1.5 − 2

(5.3 − 7.0)

425 − 1020
(200 − 480)

G43UF

−36B−070

40 − 70

(22 − 39)

10 x 8

(254 x 203)

2 − 3

(8.8 − 10.5)

710 − 1640
(335 − 775)

G43UF

−36C−090

40 − 70

(22 − 39)

10 x 8

(254 x 203)

2 − 3

(7.0 − 10.5)

730 − 1630
(345 − 770)

G43UF

−36C−090H

Canada Only

50 − 80

(28 − 44)

10 x 8

(254 x 203)

2 − 3

(7.0 − 10.5)

730 − 1630
(345 − 770)

SPECIFICATIONS

Gas
Heating

ModelNo.

G43UF

−48C−090

Performance

Input− Btuh (kW) 88,000 (25.8) 110,000 (32.2) 110,000 (32.2) 110,000 (32.2) 132,000 (38.7)

Output− Btuh (kW) 82,000 (24.0) 103,000 (30.2) 101,000 (29.6) 103,000 (30.2) 123,000 (36.0)

Temperature rise range − F (C) 40 − 70

(22 − 39)

1

AFUE 92.1% 92.1% 90.0% 92.1% 92.1%

Highstatic(CSA)− in.w.g. (Pa) .50 (124) .50 (124) .50 (124) .50 (124) .50 (124)

Connections
in.

Condensate Drain Trap (PVC pipe) − i.d.

Intake / Exhaust Pipe (PVC) 2 / 2 2 / 2 2 / 2 2 / 2 3 / 3

1/2 1/2 1/2 1/2 1/2

with field supplied (PVC coupling) − o.d. 3/4 3/4 3/4 3/4 3/4

hose with hose clamp − i.d. x o.d. 1−1/4 x 1 1−1/4 x 1 1−1/4 x 1 1−1/4 x 1 1−1/4 x 1

GaspipesizeIPS 1/2 1/2 1/2 1/2 1/2

Indoor
Blower

Wheelnominaldiameter xwidth −in.

(mm)

10 x 10

(254 x 254)

Motoroutput − hp (W) 1/2 (373) 1/2 (373) 1/2 (373) 1 (746) 1 (746)

Tons(kW) ofadd−oncooling 3 − 4

(10.5 − 14.0)

Air Volume Range − cfm (L/s) 950 − 2180

(450 − 1030)

ShippingData − lbs. (kg) − 1 package 168 (76) 178 (81) 178 (81) 186 (84) 203 (92)

Electricalcharacteristics 120 volts − 60 hertz − 1 phase (less than 12 amps)

NOTE − Filters and provisions for mounting are not furnished and must be field provided.

1

Annual Fuel Utilization Efficiency based on DOE test procedures and according to FTC labeling regulations. Isolated combustion system rating for non−weatherized furnaces

G43UF

−48C−110

45 − 75

(27 − 45)

10 x 10

(254 x 254)

3 − 4

(10.5 − 14.0)

885 − 2160

(420 − 1020)

G43UF

−48C−110H

Canada Only

50 − 80

(28 − 44)

10 x 10

(254 x 254)

3 − 4

(10.5 − 14.0)

885 − 2160

(420 − 1020)

G43UF

−60C−110

40 − 70

(22 − 39)

11−1/2 x 10

(292 x 229)

4 − 5

(14.0 − 17.5)

1470 − 2720
(695 − 1285)

G43UF

−60D−135

45 − 75

(27 − 45)

11−1/2 x 10

(292 x 229)

4 − 5

(14.0 − 17.5)

1440 − 2730

(680 − 1290)

G43UF / Page 5