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© 2025 Lennox Industries Inc.
Dallas, Texas USA
WARNING
This furnace is equipped with an ignition control
factory enabled for use with Lennox A2L refrigerant
systems.
Disabling
functionality on A2L system is prohibited by safety
codes. Refer to furnace installation instructions for
non-A2L and non-Lennox refrigerant system setup.
Contents
Unit Dimensions - inches (mm) ......................................2
EL280DFEK Gas Furnace ..............................................3
Shipping and Packing List ..............................................3
Safety .............................................................................3
Use of Furnace as a Construction Heater ......................4
General ...........................................................................4
Combustion, Dilution, Ventilation Air...............................5
Down Flow Installation....................................................8
Setting Equipment ..........................................................9
Filters ............................................................................10
Duct System ................................................................. 11
Venting ......................................................................... 11
C C C C
I I I I
HI
HI
the
refrigerant
detection
INSTALLATION
INSTRUCTIONS
EL280DFEK
ELITE
SERIES GAS FURNACE
®
DOWNFLOW AIR DISCHARGE
508551-01
01/2025
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 man-
uals, be alert to the potential for personal injury or death.
Improper
installation,
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.
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.
Gas Piping ....................................................................17
Electrical .......................................................................19
Ignition Control .............................................................21
Low GWP .....................................................................30
Unit Start-Up .................................................................33
Gas Pressure Measurement.........................................34
Proper Combustion.......................................................35
High Altitude .................................................................35
Other Unit Adjustments.................................................36
Sequence of Operation.................................................36
Service..........................................................................37
Start-Up and Performance Checklist ............................41
Page 1
WARNING
adjustment,
alteration,
CAUTION
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Table of Contents
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Summary of Contents for Lennox ELITE EL280DFEK
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Page 1: Table Of Contents
Take care while handling this equipment and This furnace is equipped with an ignition control wear gloves and protective clothing. factory enabled for use with Lennox A2L refrigerant systems. Disabling refrigerant... -
Page 2: Unit Dimensions - Inches (Mm)
Unit Dimensions - inches (mm) 3-1/8 9/16 (79) (14) RETURN AIR OPENING FLUE OUTLET 19-7/16 9/16 (Top) (494) (14) 9/16 (14) TOP VIEW 27-3/4 1-1/2 (38) (705) Front Panel 9/16 19-7/16 9/16 (14) (494) (14) AIR FLOW ELECTRICAL INLET (Either Side) (838) 5-3/8 (137) Right GAS PIPING INLET... -
Page 3: El280Dfek Gas Furnace
Certifications EL280DFEK Gas Furnace EL280DFEK units are CSA International certified. The EL280DFEK gas furnace is shipped ready for instal- In the USA, installation of gas furnaces must conform with lation in the downflow position fueled by natural gas. A local building codes. In the absence of local codes, units conversion kit (ordered separately) is required for use in must be installed according to the current National Fuel LP/ Propane gas applications. -
Page 4: Use Of Furnace As A Construction Heater
Place the furnace as close to the center of the air distribution system as possible. The furnace should Safety also be located close to the chimney or vent termi- Lennox does not recommend the use of EL280DFEK nation point. units as a construction heater during any phase of con- •... -
Page 5: Combustion, Dilution, Ventilation Air
CAUTION Combustion, Dilution & Ventilation Air In the past, there was no problem in bringing in sufficient Insufficient combustion air can cause headaches, outdoor air for combustion. Infiltration provided all the air nausea, dizziness or asphyxiation. It will also cause that was needed. - Page 6 When the furnace is installed so that supply ducts carry Each opening must be at least 100 square inches (64516 air circulated by the furnace to areas outside the space mm2). One opening shall be within 12 inches (305 mm) of containing the furnace, the return air must be handled by the top of the enclosure and one opening within 12 inches ducts which are sealed to the furnace casing and which...
- Page 7 EQUIPMENT IN CONFINED SPACE ALL AIR FROM OUTSIDE (Inlet Air from Crawlspace and Outlet Air to Ventilated Attic) CHIMNEY OR GAS VENT VENTILATION LOUVERS (Each end of attic) OUTLET WATER FURNACE HEATER INLET 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 ) per 4,000 Btu (1.17 kW) per hour of the total input rating of all equipment in the enclosure.
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Page 8: Downflow Installation
IMPORTANT Downflow Installation Downflow unit installs in three ways: on non-combustible The furnace and downflow combustible flooring flooring, on combustible flooring using a downflow com- base shall not be installed directly on carpeting, bustible flooring base, or on a reverse-flow cooling cabi- tile, or other combustible material other than wood net. -
Page 9: Cooling Coil
Setting Equipment WARNING UNIT Do not install the furnace on its front, back or in the horizontal position. See FIGURE 12 . 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 COOLING COIL injury or death. -
Page 10: Filters
Horizontal Front Back FIGURE 12 Downflow Application WARNING Allow for clearances to combustible materials as indicated Improper installation of the furnace can result in on the unit nameplate. Minimum clearances for closet or personal injury or death. Combustion and flue alcove installations are shown in FIGURE 13. -
Page 11: Duct System
The EL280DFEK series units are classified as fan-assist- Duct System ed Category I furnaces when vertically vented according Use industry-approved standards (such as those pub- to the latest edition of National Fuel Gas Code (NFPA 54 lished by Air Conditioning Contractors of America or Amer- / ANSI Z223.1). - Page 12 Use self-drilling sheet metal screws or a mechanical fas- Insulation for the flexible vent pipe must be an encapsu- tener to firmly secure the vent pipe to the round collar of lated fiberglass sleeve recommended by the flexible vent the flue transition. If self-drilling screws are used to attach pipe manufacturer.
- Page 13 DO NOT insulate the space between the liner and 3 - The minimum vent capacity determined by the sizing the chimney wall with puffed mica or any other loose tables must be less than the low fire input rating and granular insulating material.
- Page 14 11 - A vent connector shall be supported without any 16 - Vent connectors serving Category I appliances shall dips or sags and shall slope a minimum of 1/4 inch not be connected to any portion of mechanical draft (6.4 mm) per linear foot (305 mm) of connector, systems operating under positive pressure such as back toward the appliance.
- Page 15 TABLE 5 Capacity of Type B Double-Wall Vents with Type B Double-Wall Connectors Serving a Single Category I Appliance Vent and Connector Diameter - D (inches) Height Lateral 3 inch 4 inch 5 inch 6 inch Appliance Input Rating in Thousands of Btu Per Hour (feet) (feet) NOTE - Single appliance venting configurations with zero lateral lengths are assumed to have no elbows in the vent system.
- Page 16 TABLE 6 Vent Connector Capacity Type B Double-Wall Vents with Type B Double-Wall Connectors Serving Two or More Category I Appliances Vent and Connector Diameter - D (inches) Height Lateral 3 inch 4 inch 5 inch 6 inch Appliance Input Rating in Thousands of Btu Per Hour (feet) (feet) TABLE 7...
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Page 17: Gas Piping
Removal of the Furnace from Common Vent Gas Piping In the event that an existing furnace is removed from a Gas supply piping should not allow more than 0.5”W.C. venting system commonly run with separate gas ap- drop in pressure between gas meter and unit. Supply gas pliances, the venting system is likely to be too large pipe must not be smaller than unit gas connection. - Page 18 TABLE 8 Gas Pipe Capacity - ft3/hr (m3/hr) Nominal Internal Length of Pipe - feet (m) Iron Pipe Diameter Size Inches inches (3.048) (6.096) (9,144) (12,192) (15.240) (18.288) (21.336) (24.384) (27.432) (30,480) (mm) (mm) .622 (12.7) (17.799) (4.87) (3.34) (2.69) (2.29) (2.03) (1.84)
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Page 19: Electrical
Leak Check The unit is equipped with a field make-up box on the left hand side of the cabinet. The make-up box may be moved After gas piping is completed, carefully check all field-in- to the right side of the furnace to facilitate installation. If stalled piping connections for gas leaks. - Page 20 Before connecting the thermostat, check to make sure If a humidifier rated at greater than one amp is connected to this terminal, it is necessary to use an external relay. the wires will be long enough for servicing at a later date. Make sure that thermostat wire is long enough to facilitate One 24V ”H”...
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Page 21: Ignition Control
Ignition Control TWO STAGE CONSTANT TORQUE, NON-COMMUNICATING 107897-01 FIGURE 21 TABLE 10 TABLE 9 THERMOSTAT INPUT TERMINALS 1/4” QUICK CONNECT TERMINALS LOW STAGE HEAT 120V HUM POWER FOR HUMIDIFIER (120 VAC HIGH STAGE HEAT LINE INCOMING POWER LINE (120 VAC) XFMR TRANSFORMER PRIMARY (120 VAC) LOW STAGE COOL (when W915 is clipped) - Page 22 TABLE 12 Field Wiring Applications With Conventional Thermostat DIP Switch Settings and On-Board Links DIP Switch 1 On Board Links Must Be Cut To Select Thermostat Thermostat Wiring Connections System Options Heating Stages 1 Heat / 1 Cool FURNACE OUTDOOR T'STAT TERM.
- Page 23 TABLE 12 Field Wiring Applications With Conventional Thermostat (Continued) DIP Switch Settings and On-Board Links DIP Switch 1 On Board Links Must Be Cut To Select Thermostat Thermostat Wiring Connections System Options Heating Stages 2 Heat / 2 Cool FURNACE OUTDOOR (M30 T-stat) T'STAT...
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Page 24: Wiring Connections
TABLE 12 Field Wiring Applications With Conventional Thermostat (Continued) DIP Switch Settings and On-Board Links DIP Switch 1 Wiring Connections Thermostat On Board Links Must Be Cut To Select Thermostat Heating System Options Stages Dual Fuel FURNACE HEAT PUMP T'STAT TERM. - Page 25 TABLE 12 Field Wiring Applications With Conventional Thermostat (Continued) DIP Switch Settings and On-Board Links DIP Switch 1 Wiring Connections Thermostat On Board Links Must Be Cut To Select Thermostat Heating System Options Stages Dual Fuel FURNACE HEAT PUMP T'STAT TERM.
- Page 26 Wiring Diagram FIGURE 22 Page 26...
- Page 27 Ignition Control Diagnostics Codes DIAGNOSTIC CODES / STATUS OF FURNACE CODE IDLE MODE (DECIMALBLINKS AT 1 HERTZ -- 0.5 SECONDS ON, 0.5 SECONDS OFF INDOOR BLOWER OPERATION: CONTINUOUS FAN MODE (COSTANT TORQUE ONLY) INDOOR BLOWER OPERATION: FOLLOWED BY CFM SETTING FOR INDOOR BLOWER (1 SECOND ON, 0.5 SECOND OFF) / CFM SETTING FOR MODE DISPLAYED (VARIALBE SPEED ONLY) COOLING STAGE (1 SECOND ON, 0.5 SECOND OFF) 1 OR 2 DISPLAYED / PAUSE / REPEAT CODES.
- Page 28 Ignition Control Diagnostic Codes (continued) SOFT LOCKOUT FAULTS (60 MINUTES) GAS VALVE RELAY (1ST OR 2ND STAGE) CONTACT SHORTED E205 HOT SURFACE IGNITOR (HSI) SENSED OPEN E207 SOFT LOCKOUT-FLAME FAILURE ON IGNITION, IGNITION RETRY>MAX, LAST FAILED RETRY DUE TO FLAME E270 FAILURE SOFT LOCKOUT-PRESSURE SWITCH OPEN, IGNITION RETRY>MAX, LAST FAILED RETRY DUE TO LPSW OPEN...
- Page 29 Switches 3 and 4 -- Heating Mode Blower-Off Delay -- On-Board Links and Diagnostic Push Button The blower-on delay of 30 seconds is not adjustable. The WARNING blower-off delay (time that the blower operates after the heating demand has been satisfied) can be adjusted by Carefully review configuration...
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Page 30: Low Gwp
Low GWP Application WARNING For use with Lennox approved evaporator coil and LGWP sensors only. Use original manufacturer recommended LGWP sensors if using non Lennox approved evaporator coil. CONNECTING THE FURNACE CONTROL BOARD SENSOR. See FIGURE 25 and follow steps below: 1 - Route sensor wire #1 through provided grommet. - Page 31 FURNACE CONTROL BOARD LOW GWP MODES OF NOTE - The HVAC system may not maintain a cooling or heating setpoint if a significant leak exists. Any refrigerant OPERATION leaks that remain unaddressed for an extended time may The modes of operation for the furnace control board are cause the HVAC system to shut down on a low refrigerant Initializing, Normal, Leak Detected, and Fault.
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Page 32: Start-Up Procedure
LGWP TEST BUTTON FUNCTIONALITY External Alarm (For applications with external alarms wired directly to the The furnace control board is equipped with a Test/Reset furnace control board) push button. The Test button can be used to perform sev- The furnace control board triggers the external alarm sys- eral functions, depending on the mode of operation of the tem when it enters Leak Detected mode. -
Page 33: Unit Start-Up
Unit Start-Up Resideo Two-Stage Gs Valve FOR YOUR SAFETY READ BEFORE LIGHTING HIGH FIRE ADJUSTING SCREW WARNING (under cap) Do not use this furnace if any part has been underwater. A flood-damaged furnace is extremely dangerous. Attempts to use the furnace can result in fire or explosion. -
Page 34: Supply Pressure Measurement
NOTE - Pressure test adapter kit (10L34) is available from 10 - Is pressure switch closed? Obstructed flue will Lennox to facilitate manifold pressure measurement. cause unit to shut off at pressure switch. Check flue 1 - Connect test gauge to manifold pressure tap on the and outlet for blockages. -
Page 35: Proper Combustion
Proper Combustion High Altitude Furnace should operate minimum 15 minutes with correct The manifold pressure may require adjustment and com- manifold pressure and gas flow rate before checking com- bustion air pressure switch may need replacing to ensure bustion. TABLE 20 shows acceptable combustion for ALL proper combustion at higher altitudes. -
Page 36: Other Unit Adjustments
Electronic Ignition Other Unit Adjustments The integrated control has an added feature of an internal Primary and Secondary Limits Watchguard control. The feature serves as an automat- The primary limit is located on the heating compartment ic reset device for integrated control lockout caused by vestibule panel. -
Page 37: Service
At the beginning of each heating season, and to comply tion the unit will switch to low fire. with the Lennox Limited Warranty, your system should 3 - After the pre-purge is complete, a 20-second initial be checked by a licensed professional technician (or ignitor warm-up period begins. - Page 38 6- Check the cleanliness of blower assembly and 3 - Clock gas meter to ensure that the unit is operating at the specified firing rate. Check the supply clean the housing, blower wheel and blower motor pressure and the manifold pressure. On two-stage if necessary .
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Page 39: Burner Removal
Ignitor BURNER REMOVAL Retention Rings Rollout Switches Sensor Cross Over Manifold And Gas Valve FIGURE 28 Page 39... - Page 40 Repair Parts List Heating Parts The following repair parts are available through indepen- dent Lennox dealers. When ordering parts, include the Flame Sensor complete furnace model number listed on the CSA Inter- Heat exchanger assembly national nameplate -- Example: EL280DF070E36AK.
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Page 41: Start-Up And Performance Checklist
Start-Up & Performance Check List UNIT SET UP (typical) Unit Model Number_______________ Serial Number___________________ SUPPLY Line Voltage upflow furnace shown Gas Supply Pressure Filter RETURN RETURN DUCT SYSTEM GAS SUPPLY SUPPLY AIR DUCT LP/Propane Gas Natural Gas Sealed Piping Connections Tight Insulated (if necessary) Leak Tested Registers Open and Unobstructed... - Page 42 UNIT OPERATION (typical) Combustion CO SUPPLY Thermostat Gas Manifold Pressure Temperatures upflow furnace shown Filter Blower Motor Amps Duct Static RETURN RETURN COOLING MODE HEATING MODE INDOOR BLOWER AMPS______ GAS MANIFOLD PRESSURE “W.C._____ TEMPERATURE DROP COMBUSTION SAMPLE CO CO PPM_______ ______ Return Duct Temperature _________ Supply Duct Temperature...
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