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FEATURES
HEATING SYSTEM
Lennox Duralok Plus® Heat Exchanger Assembly
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
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
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® insulated ignition lead wires for
dependable operation.
Gas Control Valve
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
Shaded pole heavy−duty blower prepurges heat exchanger and
safely vents flue products.
Pressure switch proves blower operation before allowing gas
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.
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
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
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
Furnished and factory installed in control box.
40VA transformer has fuse wired in series.
Field Wiring Make-up Box
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.
Statically and dynamically balanced.
Resiliently mounted.
Blower assembly slides out of unit for servicing.
Blower speeds are easily changed on the integrated furnace
control board. See blower performance tables.
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