Lennox LF24 User Manual
E N G I N E E R I N G D A T A
G A S U N I T H E A T E R S / D U C T F U R N A C E S
LF24
UNIT HEATERS
Horizontal − 60 HZ
Bulletin No. 210000
July 2007
Supersedes June 2007
Tubular Heat Exchanger
Front View Back View
MODEL NUMBER IDENTIFICATION
LF − Lennox Unit Heater
100 = 100,000 Btuh
115 = 115,000 Btuh
145 = 145,000 Btuh
175 = 175,000 Btuh
200 = 200,000 Btuh
Unit Type
Series
Nominal Gas Heat Input
230 = 230,000 Btuh
250 = 250,000 Btuh
300 = 300,000 Btuh
345 = 345,000 Btuh
400 = 390,000 Btuh
FEATURES
CONTENTS
Dimensions Pages 4−5. . . . . . . . . . . . . . . . . . . . . . . . . . .
Features Pages 1−2. . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Guide Specifications Pages 8−11. . . . . . . . . . . . . . . . . .
High Altitude Information Page 5. . . . . . . . . . . . . . . . . .
Installation Clearances Page 5. . . . . . . . . . . . . . . . . . . .
Model Number Identification Page 1. . . . . . . . . . . . . . .
Mounting Height Page 5. . . . . . . . . . . . . . . . . . . . . . . . . .
Optional Accessories Page 3−4. . . . . . . . . . . . . . . . . . .
Specifications Page 3−4. . . . . . . . . . . . . . . . . . . . . . . . . .
Throw Data Page 5. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Maximum Horizontal Vent Lengths Page 5. . . . . . . . . .
LF
Steady State Efficiency − up to 80.5%
Input − 100,000 to 400,000 Btuh
200−
A24
Heat Exchanger Type
A = Aluminized Steel Heat Exchanger
S = Stainless Steel Heat Exchanger
EQUIPMENT Warranty
Heat exchanger − stainless steel − fifteen year limited
warranty, aluminized steel − ten year limited warranty.
All other covered components − one year limited warranty.
Refer to Lennox Equipment Limited Warranty certificate
included with equipment for details.
FEATURES
Applications
Lennox LF24 gas−fired, horizontal unit heaters are
compact in design and easy to install.
Units feature steady−state heating efficiencies of up to
80.5%.
LF24 unit heaters are ideal for economical commercial
heating systems.
Units are shipped completely assembled with controls
factory installed and wired.
In addition, each unit is test operated at the factory to
ensure proper operation and dependability.
Installer has only to locate unit, make unit gas supply, flue,
electrical connections and mount thermostat to complete
the installation.
Units may be vented horizontally or vertically.
Approvals
Units certified by CSA International.
Listed by the California Energy Commission (CEC).
Units are certified for natural or LPG/Propane gas.
ISO 9001 Registered Manufacturing Quality System.
HEATING SYSTEM
24 volt redundant combination gas control valve
combines a manual main shutoff valve, pressure
regulation and automatic electric valve (dual) into one
compact combination control.
Solid−state electronic direct spark ignition control provides
positive and safe main burner ignition.
Spark is intermittent and occurs only when required.
Separate electronic flame sensor control assures safe
and reliable operation.
Should loss of flame occur, flame sensor controls will
initiate 3 attempts at re−ignition before locking out unit
operation.
Combustion air inducer prepurges heat exchanger and
safely vents flue products.
Pressure switch proves combustion air inducer operation
before allowing gas valve to open.
Combustion air inducer operates only during heating
cycle.
Tubular Aluminized or Stainless Steel Heat
Exchanger
Tubular heat exchanger is constructed of aluminized or
stainless steel for superior resistance to corrosion and
oxidation.
Curving design allows complete exposure of heating
surfaces to supply air stream.
Round surfaces create minimum air resistance and allow
air to surround all surfaces for excellent heat transfer.
Compact design reduces space requirements in unit
cabinet.
Heat exchanger has been laboratory life cycle tested.
Inshot Burners
Aluminized steel inshot burners provide efficient trouble
free operation.
Burner venturi mixes air and gas in correct proportion for
proper combustion.
Burner assembly is removeable from the unit as a single
component for ease of service. Each burner may be
removed individually.
Limit Control
Factory installed and accurately located.
Limit control has fixed temperature setting and protects
heating system from abnormal operating conditions.
LF24 − 100,000 to 400,000 Btuh / Page 2
Combustion Air Inducer
Combustion air inducer prepurges heat exchanger and
safely vents combustion products.
Blower motor has sleeve bearings and is thermally
protected.
Pressure switch prevents unit operation in case of
blockage of combustion air inlet or flue outlet.
Combustion air inducer on LF24−100, −115, −125, −145
units may be rotated 90_ to left or right of vertical to
facilitate installation.
Venting
Units may be vented horizontally or vertically.
LF24 units are approved for installation with single wall
and type B−1 double wall vent pipe.
OPTIONS
LPG/Propane Conversion Kit
Conversion kit is required for field changeover from
natural gas.
Kit is not furnished and must be ordered extra.
Controls
Includes: 24 volt main gas valve with 100% safety shutoff,
main shutoff valve, gas pressure regulation (natural &
LPG/propane gas models), limit control, transformer and
combination ignition/fan timer control board.
Combination Direct Spark Ignition/Fan Timer Control
Solid−state control board contains all necessary controls
and relays to operate unit.
Includes: Fan timer control − fan on 45 seconds (fixed), fan
off 150 seconds (fixed), terminal strip for thermostat
connections, diagnostic LED for troubleshooting,
continuous fan operation.
Transformer
120V/24V transformer furnished as standard.
OPTIONS
Thermostat
See Thermostat bulletins in Controls section and Lennox
Price Book for a complete list of thermostats.
Direct Drive Fan
All models are equipped with efficient and quiet operating
direct drive fan.
Cabinet
Constructed of heavy gauge painted steel.
Inside cabinet insulation keeps outer cabinet surface
temperatures low.
Adjustable louvers are furnished on cabinet for control of
air flow direction.
Wiring junction box is conveniently located on outside of
cabinet for easy access. Box contains all electrical and
safety controls.
Terminal strip provided for thermostat connections.
3/8 x 16 rivetnuts are located on the top of cabinet for
suspending unit. See dimension drawing.
OPTIONS
Discharge Nozzles
To direct discharge air from unit heater.
Available in 30_, 45_, 60_ and 90_ style.
Fully assembled from heavy−gauge steel.
Paint finish matches unit heater.
See Dimension Drawings.
Hanging Bracket Kit
Used to suspend unit heaters on two pipe hangers.
Kit contains two brackets and all necessary hardware.
Pipe hangers (3/4 in.) are not furnished and must be field
provided.
SPECIFICATIONS − LF24−100 to LF24−200
Gas
Heating
Performance
Model No. − Stainless Steel LF24−100S
Model No. − Aluminized Steel LF24−100A LF24−115A LF24−145A LF24−175A LF24−200A
Heating Capacity Input − Btuh 100,000 115,000 145,000 172,500 195,000
Output − Natural − Btuh 80,500 92,000 116,000 138,000 156,000
Steady State Efficiency − Natural 80.5% 80.0% 80.0% 80.0% 80.0%
Connections
Flue size − in. (round)
1
4
Gas Piping Size 1/2 1/2 1/2 1/2 1/2
Fan Data
Air Volume − cfm 1900 1900 1900 2200 2200
Number of Fans 1 1 1 1 1
Diameter − in. 16 16 16 16 16
Number of blades 4 4 5 5 5
Number of Motors 1 1 1 1 1
Motor Output − hp 1/8 1/8 1/8 1/8 1/8
RPM 1075 1075 1075 1075 1075
Weight Data
Net Weight − lbs. 125 125 130 145 145
Shipping Weight − lbs. 140 140 150 165 165
ELECTRICAL DATA
Line voltage data − 60hz 115 volts − 1 phase
Motor amps 2.1 2.1 2.1 2.1 2.1
Total unit amps 6.0 6.0 6.0 6.0 6.0
Optional Accessories − Must Be Ordered Extra
Discharge
Nozzle
Hanging Bracket Kit 87277 S S S S S
3
High Altitude
Pressure Switch Kit
LPG/Propane Kit
1
2−1/8 x 4 in. diameter adaptor is furnished with unit for flue connection.
2
2−1/4 x 2−3/4 in. rectangular to 5 in. round adaptor is furnished with unit for flue connection.
3
Required for proper unit operation at altitudes over 5501 feet above sea level.
30_ − 94K94 S
94K95 S S
94K96
45_ − 95K98 S S S
95K99 S S
95K00
60_ − 16L28 S S S
16L29 S S
16L30
90_ − 15L96 S S S
15L97 S S
15L98
10K73 S S S S − − −
45L85 S
63J56 S S S
20L07 S
63J57
LF24−115S LF24−145S LF24−175S LF24−200S
1
4
1
4
2
5
S S
2
5
LF24 − 100,000 to 400,000 Btuh / Page 3
SPECIFICATIONS − LF24−230 to LF24−400
Gas
Heating
Performance
Connections
Model No. − Stainless Steel LF24−230S
Model No. − Aluminized Steel LF24−230A LF24−250A LF24−300A LF24−345A LF24−400A
Heating Capacity Input − Btuh 230,000 250,000 300,000 345,000 390,000
Output − Natural − Btuh 184,000 201,250 241,500 276,000 312,000
Steady State Efficiency − Natural 80.0% 80.5% 80.5% 80.0% 80.0%
Flue size − in. (round)
Gas Piping Size 3/4 3/4 3/4 3/4 3/4
LF24−250S LF24−300S LF24−345S LF24−400S
1
5
1
5
1
5
2
6
2
6
Fan Data
Air Volume − cfm 4400 4400 4400 4400 4400
Number of Fans 2 2 2 2 2
Diameter − in. 16 16 16 16 16
Number of blades 5 5 5 5 5
Number of Motors 2 2 2 2 2
Motor Output − hp 1/8 1/8 1/8 1/8 1/8
RPM 1075 1075 1075 1075 1075
Net Weight − lbs. 225 270 280 285 285
Weight Data
Shipping Weight − lbs. 270 285 305 310 310
ELECTRICAL DATA
Line voltage data − 60hz 115 volts − 1 phase
Motor amps 2.1 (4.2) 2.1 (4.2) 2.1 (4.2) 2.1 (4.2) 2.1 (4.2)
Total unit amps 9.0 9.0 9.0 9.0 9.0
Optional Accessories − Must Be Ordered Extra
Discharge
Nozzle
30_ − 94K96 S S S S S
45_ − 95K00 S S S S S
60_ − 16L30 S S S S S
90_ − 15L98 S S S S S
Hanging Bracket Kit 87277 S S S S S
LPG/Propane Kit
45L88 S S
63J57 S S
20L06 S
1
2−1/4 x 2−3/4 in. rectangular to 5 in. round adaptor is furnished with unit for flue connection.
2
2−1/4 x 2−3/4 in. rectangular to 6 in. round adaptor is furnished with unit for flue connection.
LF24 − 100,000 to 400,000 Btuh / Page 4
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