Heating System - Lennox LF24 Manual

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
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.
LED for troubleshooting,