Lennox EL280DFE Installation Instructions

Contents

• Unit Dimensions - inches (mm)
• EL280DFE Gas Furnace
• Shipping and Packing List
• Safety
• Use of Furnace as a Construction Heater
• General
• Combustion, Dilution, Ventilation Air
• Down Flow Installation
• Setting Equipment
• Filters
• Duct System
• Venting
• Gas Piping
• Electrical
• Integrated Control
• Unit Start-Up
• Gas Pressure Measurement
• Proper Combustion
• High Altitude
• Other Unit Adjustments
• Sequence of Operation
• Service
• Start-Up and Performance Checklist
• Blower Data

Unit Dimensions - inches (mm)

Diagram shows a furnace with dimensions labeled A, B, C, D. It includes views for FLUE OUTLET (Top), TOP VIEW, FRONT VIEW, and SIDE VIEW. The diagram indicates AIR FLOW direction.

EL280DFE Gas Furnace

The EL280DFE gas furnace is shipped ready for installation in the downflow position, fueled by natural gas. A conversion kit (ordered separately) is required for use in LP/Propane gas applications.

Shipping and Packing List

Package 1 of 1 contains:

• 1 - Assembled EL280DFE unit
• 1 - Bag assembly containing: 2 - Screws, 1 - Snap bushing, 1 - Snap plug, 1 - Wire tie, 1 - Vent warning label, 1 - Owner's manual and warranty card

Items that may be ordered separately:

• 1 - Thermostat
• 1 - LP/Propane changeover kit
• 1 - Combustible flooring base
• 1 - High altitude kit

Check equipment for shipping damage. If any damage is found, contact the last carrier immediately.

Safety

▲ DANGER

Danger of explosion. Odorant used with LP/propane gas can lose its scent. In case of a leak, LP/propane gas will settle close to the floor and may be difficult to smell. An LP/propane leak detector should be installed in all LP applications.

▲ WARNING

Improper installation, adjustment, alteration, service or maintenance can cause property damage, personal injury or loss of life. Installation and service must be performed by a licensed professional installer (or equivalent), service agency, or the gas supplier.

▲ CAUTION

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.

Certifications

EL280DFE units are CSA International certified. Installation must conform with local building codes or the current National Fuel Gas Code (ANSI-Z223.1). The National Fuel Gas Code is available from the American National Standards Institute, Inc., 11 West 42nd Street, New York, NY 10036.

Clearances

Adequate clearance must be provided around air openings for proper unit operation, combustion, and ventilation air supply, following the National Fuel Gas Code. Vent installations must be consistent with National Fuel Gas Code venting tables and local building codes. Installation clearances to combustible material are listed on the unit nameplate and in Figure 13. Accessibility and service clearances take precedence over fire protection clearances.

Installed Locations

For installation in a residential garage, the furnace must be located at least 18 inches (457 mm) above the floor, and protected from physical damage by vehicles. In public garages or buildings with hazardous atmospheres, follow recommended practices and the National Fuel Gas Code. The furnace must be adjusted for a temperature rise within the range specified on the nameplate to avoid erratic limit operation and premature heat exchanger failure. Electrical components must be protected from water.

Installed in Combination with a Cooling Coil

When used with cooling units, the furnace should be installed in parallel with or upstream of the cooling units to prevent condensation in the heating compartment. A damper must prevent chilled air from entering the furnace. If manually operated, the damper must prevent operation of either heating or cooling unless the unit is in the full HEAT or COOL setting.

Diagram: Airflow Arrangement with Cooling Coil

Figure 1 illustrates a typical setup for a furnace and air handler with dampers. Dampers are shown open during heating operation for the GAS UNIT and open during cooling operation for the AIR HANDLER. This diagram helps visualize airflow control in conjunction with a cooling unit.

Electrical Grounding and Codes

The furnace must be electrically grounded according to local codes and the current National Electric Code (ANSI/NFPA No. 70). The National Electric Code is available from the National Fire Protection Association, 1 Battery March Park, Quincy, MA 02269.

Operating Temperature Requirements

This furnace is designed for a minimum continuous return air temperature of 60°F (16°C) or intermittent operation down to 55°F (13°C) dry bulb for night setback thermostats. Return air temperature must not exceed 85°F (29°C) dry bulb.

Installation Locations

The EL280DFE furnace can be installed in alcoves, closets, attics, basements, garages, and utility rooms in the downflow position. This furnace design is not CSA International certified for installation in mobile homes, recreational vehicles, or outdoors.

Safety Considerations

Lennox does not recommend using the EL280DFE as a construction heater due to potential damage from low return air temperatures, harmful vapors, or clogged filters. If used for heating buildings under construction, the following conditions must be met:

• The vent system must be permanently installed per instructions.
• A room thermostat must control the furnace; fixed jumpers for continuous heating are not allowed.
• The return air duct must be provided and sealed to the furnace.
• Return air temperature must be maintained between 60°F (16°C) and 80°F (27°C).
• Air filters must be installed and maintained during construction.
• Filters must be replaced upon construction completion.
• Input rate and temperature rise must be set per the furnace rating plate.
• 100% outdoor air must be provided for combustion air requirements during construction, potentially via temporary ducting. Do not connect duct directly to the furnace.
• The heat exchanger, components, duct system, filters, and evaporator coils must be thoroughly cleaned after final construction.
• All operating conditions (ignition, input rate, temperature rise, venting) must be verified per installation instructions.

General Installation Recommendations

These instructions are a guide and do not supersede local codes. Consult authorities having jurisdiction before installation. Additional recommendations include:

• Place the furnace near the center of the air distribution system and close to the chimney/vent termination point.
• Avoid locations where drafts could blow directly into the furnace, causing improper combustion.
• Do not block combustion air openings with obstructions.
• Keep insulation away from the furnace when installed in an attic or insulated space.

Massachusetts Specific Requirements

Gas furnaces must be installed by a licensed plumber or fitter. The gas cock must be a "T handle" type. Passageways and service areas around attic-installed furnaces must be floored.

Combustion, Dilution & Ventilation Air

Modern tight construction requires bringing in outdoor air for combustion. Exhaust fans and other appliances can remove air needed for combustion, potentially causing downdrafts and introducing combustion gases into the living space. Follow guidelines for combustion air and ventilation to ensure efficient and safe operation. This information is partially reprinted from the National Fuel Gas Code (ANSI-Z223.1).

▲ CAUTION

Do not install the furnace in a corrosive or contaminated atmosphere. Meet all combustion and ventilation air requirements and local codes.

Insufficient combustion air leads to inefficient and unsafe operation, potentially causing carbon monoxide. Fresh outdoor air dilutes indoor contaminants that can corrode furnace components.

▲ CAUTION

Insufficient combustion air can cause headaches, nausea, dizziness, or asphyxiation, and lead to excess water in the heat exchanger, causing rust and premature failure. Avoid exposure to substances like permanent wave solutions, chlorinated waxes, pool chemicals, water softeners, de-icing salts, carbon tetrachloride, halogen refrigerants, cleaning solvents, printing inks, paints, hydrochloric acid, cements, glues, antistatic fabric softeners, and masonry acid washing materials.

Confined vs. Unconfined Spaces

Air requirements depend on whether the furnace is in an unconfined or confined space.

• Unconfined Space: An area with a volume greater than 50 cubic feet (1.42 m³) per 1,000 Btu (.29 kW) of combined input rating of appliances. This includes adjacent rooms not separated by a door. Tight construction may necessitate bringing in outdoor air.
• Confined Space: An area with a volume less than 50 cubic feet (1.42 m³) per 1,000 Btu (.29 kW) of combined input rating. This includes furnace closets or small equipment rooms.

Diagram: Equipment in Confined Space - Air from Inside

Figure 2 illustrates equipment in a confined space where all air is drawn from inside the building. It shows a furnace and water heater, with openings to an adjacent room for air intake. The note specifies minimum opening size requirements per Btu input.

Air from Inside

If a confined space adjoins an unconfined space, two permanent openings are required between them. Each opening must have a minimum free area of 1 square inch (645 mm²) per 1,000 Btu (.29 kW) of total input rating for all gas-fired equipment in the confined space. Each opening must be at least 100 square inches (64516 mm²), with one near the top and one near the bottom (within 12 inches / 305 mm).

Air from Outside

For combustion and ventilation air from outside, the confined space needs two permanent openings, one near the top and one near the bottom. These openings must connect directly or via ducts to the outdoors or spaces communicating with the outdoors. Each opening requires a minimum free area of 1 square inch (645 mm²) per 4,000 Btu (1.17 kW) of total input rating for all equipment (or per 2,000 Btu for horizontal ducts). Louvers, grilles, or screens must be considered for free area calculations. If their design is unknown, assume wood louvers have 20-25% free area, and metal louvers/grilles have 60-75% free area. Louvers must be fixed open or interlocked with equipment operation.

Diagrams: Equipment in Confined Space - Air from Outside

Figure 3 shows equipment in a confined space with air from a crawlspace and outlet to a ventilated attic. Figure 4 shows air from an attic through ventilated louvers at each end. Figure 5 shows air from outside via ducts, with specific notes on opening sizes and connections.

Downflow Installation

Downflow units can be installed on non-combustible flooring, combustible flooring (with a base), or a reverse-flow cooling cabinet. Do not drag the unit.

Installation on Non-Combustible Flooring (FIGURE 6)

1. Cut floor opening considering clearances, gas, electrical, flue, and air intake connections. Refer to TABLE 1 for opening size.
2. Flange warm air plenum and lower into opening.
3. Set unit over plenum and seal.
4. Ensure seal is adequate.

Installation on Combustible Flooring (FIGURE 7)

A downflow combustible flooring base (ordered separately) is required between the furnace and the floor. Refer to TABLE 2 for opening size. After cutting the opening, set the base, check sealing strips, lower the supply air plenum, seal it to the base, set the furnace over the plenum, and ensure adequate seals.

Installation on Cooling Cabinet (FIGURE 8)

Follow reverse-flow coil installation instructions for the opening and cabinet. Secure the furnace to the cabinet and seal for air leaks. The downflow combustible flooring kit is not used.

Return Air Opening -- Downflow Units

Plenum installation steps:

1. Plenum bottom edge should be flanged with a hemmed edge (See FIGURE 9).
2. Use sealing strip.
3. Secure plenum to furnace top flanges with sheet metal screws.
4. For closet installations where external screws are difficult, use a removable front plenum and install screws from the inside (See FIGURE 10).
5. Ensure an adequate seal is made.

Setting Equipment

▲ WARNING

Do not install the furnace on its front, back, or horizontally. Do not connect return air ducts to the back of the furnace, as this affects safety controls and can cause injury or death. Install the EL280DFE furnace only in the downflow position.

Select a location allowing required clearances (from unit nameplate) and consider gas/electrical supply, vent connection, and service access (24 inches / 610 mm at unit front). The unit must be level.

Units with 1/2 and 3/4 hp blower motors have three flexible legs and one rigid leg. The rigid leg has a shipping bolt and washer that must be removed before operation. After removal, the rigid leg will not touch the blower housing.

▲ WARNING

The blower access panel must be securely in place when the blower and burners are operating. Gas fumes, which could contain carbon monoxide, can be drawn into the living space, resulting in personal injury or death.

Diagram: Furnace Orientations

Figure 12 shows the furnace in Front, Back, and Horizontal orientations, indicating that horizontal installation is not permitted.

Downflow Application Clearances

Allow for clearances to combustible materials as indicated on the unit nameplate. Minimum clearances for closet or alcove installations are shown in FIGURE 13. The table details clearances for Type C and Type B1 vent connectors for Top, Front, Back, Sides, Vent, and Floor.

▲ WARNING

Improper installation can result in personal injury or death. Combustion and flue products must never enter the return air system or living space. Seal the return air system to the furnace using screws and joint tape. In platform installations with bottom return air, seal the furnace airtight to the return air plenum. A door must not be used as part of the return air duct system. The base must provide stable support and an airtight seal. Ensure no sagging, cracks, or gaps. Return and supply air ducts must not connect to other heating devices like fireplaces or stoves, as this can cause fire, explosion, carbon monoxide poisoning, injury, or property damage.

Filters

The unit does not include a filter or rack. A field-provided high-velocity filter is required for proper operation. TABLE 3 lists recommended filter sizes. A filter must be in place whenever the unit is operating.

Duct System

Size and install the supply and return air duct system according to industry-approved standards (e.g., ACCA or ASHRAE). See FIGURE 14 for proper duct installation to ensure a quiet, low-static system with uniform air distribution. Do not operate the furnace in heating mode with external static pressure exceeding 0.5 inches w.c., as this can cause erratic limit operation. Ensure seals between the supply air plenum, furnace, and return air plenum.

Return Air Plenum

Return air must not be drawn from rooms containing this furnace, other gas appliances (like water heaters), or carbon monoxide-producing devices (like fireplaces). Drawing return air from a room creates negative pressure, which can cause flue products to be pulled back down the vent pipe and into the room, leading to incomplete combustion and carbon monoxide distribution.

Diagram: Duct Installation - Down-Flow Unit

Figure 14 shows a diagram illustrating duct installation for a down-flow unit, indicating supply air and return air paths.

Venting

A 4-inch diameter flue transition is factory-installed. Modifying or removing it will cause unsafe operation and void certification. The vent connector requires no insulation.

IMPORTANT

Once the venting system is installed, attach the "Disconnected Vent" warning sticker (provided in the bag assembly) near the vent pipe. Order kit 66W04 for additional stickers.

▲ WARNING

Asphyxiation hazard. The exhaust vent must be securely connected to the furnace flue transition at all times.

Diagram: Vent Connection

Figure 15 shows the vent connection, including the flue transition collar and the "DISCONNECTED VENT" warning sticker.

Venting Procedures

Secure the vent pipe to the flue transition collar using self-drilling sheet metal screws (three recommended). Install the first vent connector elbow at least six inches (152 mm) from the furnace vent outlet. Masonry chimneys used for Category I furnaces must be tile-lined or have a listed metal lining system or dedicated gas vent. Unlined masonry chimneys are prohibited. See Figures 16 and 17 for common venting.

Venting Using a Masonry Chimney

For lined masonry chimneys, especially exterior ones (exposed on one or more sides), a B1 vent or listed insulated flexible metal vent liner is required if the chimney is not tile-lined. If the existing chimney cannot accommodate a liner, it must be rebuilt or an alternate venting method found.

Insulation for flexible vent pipe must be an encapsulated fiberglass sleeve.

Diagrams: Common Venting

Figure 16 illustrates common venting using a metal-lined masonry chimney, showing clearances and components. Figure 17 illustrates common venting using a tile-lined interior masonry chimney and combined vent connector, detailing minimum and maximum lengths and required sizing.

Venting Requirements

IMPORTANT

DO NOT insulate the space between the liner and the chimney wall with loose granular insulating material.

IMPORTANT

SINGLE appliance venting into a tile-lined masonry chimney (interior or outside wall) is PROHIBITED. The chimney must first be lined with type B1 vent or an insulated single wall flexible vent lining system, sized per tables and manufacturer instructions.

Common Venting into Existing Masonry Chimneys

A furnace can be commonly vented into an existing lined masonry chimney if:

• The chimney serves at least one draft-hood equipped appliance.
• Vent connectors and chimney are sized per provided tables.
• If type B1 double-wall vent is used, no other appliance can be vented into it.
• The outer wall of type B1 vent pipe must not be exposed to flue products.
• Type B1 vent or masonry chimney liner must terminate above the roof with a listed cap or assembly.

If an existing chimney is unsafe, it must be rebuilt, relined, or replaced. The chimney passageway must be checked periodically for obstructions.

Do not install manual dampers, barometric draft regulators, or flue restrictors between the furnace and chimney. Never connect a Category I appliance to a chimney serving a solid-fuel appliance. Fireplace openings must be permanently sealed if used for venting.

A type B or listed chimney lining system through an unused flue is not considered exposed to the outdoors.

General Venting Requirements

Vent all EL280DFE furnaces according to these instructions:

• Vent diameter recommendations and maximum piping runs are in the provided venting tables.
• Vent or vent connector diameter must not be less than specified in the tables.
• Minimum vent capacity must be less than the low fire input rating, and maximum vent capacity must be greater than the high fire input rating.
• Single appliance vents: If the vertical vent or chimney has a larger diameter/flow area than the connector, use the vertical vent diameter for minimum capacity and connector diameter for maximum capacity. Vertical vent flow area must not exceed 7 times the appliance's listed vent area, drafthood outlet area, or flue collar area, unless designed per engineering methods.
• Multiple appliance vents: The flow area of the largest vertical vent/chimney section must not exceed 7 times the smallest appliance's vent area, drafthood outlet area, or flue collar area, unless designed per engineering methods.
• The entire length of single wall metal vent connector must be accessible for inspection, cleaning, and replacement.
• Single appliance venting with zero lateral lengths (TABLE 5) assumes no elbows. Other configurations assume two 90° elbows. Each additional 90° elbow or equivalent reduces maximum capacity by 10% (0.90 x max capacity).
• Common venting tables (TABLES 6 & 7) use a maximum horizontal vent connector length of 1-1/2 feet (.46 m) per inch (25 mm) of connector diameter.
• If the common vertical vent is offset, reduce common vent capacity by 20% (0.80 x max capacity). The horizontal length of the offset must not exceed 1-1/2 feet (.46 m) per inch (25 mm) of common vent diameter.
• Vent pipe should be as short as possible with minimal elbows/angles. Route the vent connector via the shortest path.

TABLE 5: Capacity of Type B Double-Wall Vents with Type B Double-Wall Connectors Serving a Single Category I Appliance

This table provides appliance input ratings (Btu/hr) based on vent height, lateral length, and vent/connector diameter for single appliance venting.

NOTE: Single appliance venting configurations with zero lateral lengths are assumed to have no elbows. For other configurations, two 90° elbows are assumed. Each additional 90° elbow or equivalent reduces maximum capacity by 10% (0.90 x maximum listed capacity).

TABLE 6: Vent Connector Capacity Type B Double-Wall Vents with Type B Double-Wall Connectors Serving Two or More Category I Appliances

This table provides appliance input ratings (Btu/hr) based on vent height, lateral length, and vent/connector diameter for common venting of two or more Category I appliances.

TABLE 7: Common Vent Capacity Type B Double-Wall Vents with Type B Double-Wall Connectors Serving Two or More Category I Appliances

This table provides appliance input ratings (Btu/hr) for common venting, considering FAN+FAN and FAN+NAT conditions for various vent sizes and heights.

Removal of the Furnace from Common Vent

If an existing furnace is removed from a common venting system, the system may be too large for remaining appliances. Test the system by operating one appliance at a time while others are off. If improperly installed, correct as per general venting requirements.

▲ WARNING

CARBON MONOXIDE POISONING HAZARD: Failure to follow steps can result in carbon monoxide poisoning or death. Follow these steps for each appliance being placed into operation while others are not:

1. Seal unused openings in the common venting system.
2. Inspect venting system for proper size, pitch, blockages, restrictions, leaks, or corrosion.
3. Close all building doors and windows. Turn on exhaust fans (dryers, hoods, etc.) to maximum speed. Do not operate summer exhaust fans. Close fireplace dampers.
4. Turn on the appliance being inspected and set the thermostat for continuous operation.
5. After 5 minutes of burner operation, test for flue gas leaks at the draft hood relief opening using a match, candle, or smoke.
6. After confirming proper venting, return all doors, fans, and dampers to their previous state.
7. If a venting problem is found, resize the common venting system to the minimum vent pipe size determined by appropriate tables (e.g., National Fuel Gas Code ANSI Z223.1 Appendix G).

Gas Piping

Gas supply piping should not cause more than a 0.5" W.C. pressure drop between the meter and the unit. The supply pipe must not be smaller than the unit's gas connection.

▲ CAUTION

If a flexible gas connector is required, black iron pipe must be installed at the gas valve and extend outside the furnace cabinet. The flexible connector is then added between the black iron pipe and the gas supply line.

▲ WARNING

Do not over-torque (800 in-lbs) or under-torque (350 in-lbs) when attaching gas piping to the gas valve.

1. The unit is shipped for left or right side gas piping installation. Connect gas supply to the piping assembly. Torque: 800 in-lbs (max), 350 in-lbs (min).
2. Consider run length, fittings, and furnace rating to avoid excessive pressure drop. TABLE 8 lists recommended pipe sizes.
3. Gas piping must not run in or through air ducts, clothes chutes, gas vents, chimneys, dumbwaiters, or elevator shafts.
4. Piping should slope 1/4 inch (6.4 mm) per 15 feet (4.57 m) upward toward the meter. Support piping at proper intervals [8-10 feet (2.44-3.01 m)] with hangers or straps. Install a drip leg inside vertical pipe runs.
5. A 1/8" N.P.T. plugged tap or pressure post on the gas valve facilitates test gauge connection (See Figure 23).
6. Local codes may require a manual shut-off valve and union (ground joint type) external to the unit.

IMPORTANT

Compounds used on threaded joints of gas piping must be resistant to liquified petroleum gases.

NOTE: For emergency shutoff, turn off the main manual gas valve and disconnect main power. Label these devices.

TABLE 8: Gas Pipe Capacity - ft³/hr (m³/hr)

This table provides gas pipe capacity based on nominal iron pipe size, length of pipe, and gas type (Natural/LP).

NOTE: Capacity given in cubic feet (m³) of gas per hour and based on 0.60 specific gravity gas.

Diagram: Gas Piping Configurations

Figure 18 illustrates standard left-side and alternate right-side gas piping configurations, showing manual shut-off valves, automatic gas valves, ground joint unions, and drip legs. It notes that black iron pipe is only to be routed inside the cabinet.

Leak Check

After gas piping is complete, check all field-installed connections for leaks using a commercially available leak detecting solution. Never use an open flame.

NOTE: For emergency shutoff, turn off the main manual gas valve and disconnect main power. Label these devices.

▲ CAUTION

Some soaps used for leak detection can be corrosive to metals. Rinse piping thoroughly after testing. Do not use matches, candles, or flames for leak testing.

The furnace must be isolated from the gas supply system by closing the manual shut-off valve if system pressure exceeds 12 psig (3.48 kPa, 14 inches w.c.). The furnace and its components are certified to applicable ANSI/CSA standards; a leak check of the furnace and its components is not required.

IMPORTANT

When testing gas lines, the gas valve must be disconnected and isolated. Gas valves can be damaged if subjected to pressures greater than 1/2 psig (3.48 kPa, 14 inches w.c.).

Diagram: Gas Valve Isolation

Figure 19 shows a diagram for isolating the gas valve during pressure testing, indicating the manual main shut-off valve, gas valve, and furnace.

Electrical

ELECTROSTATIC DISCHARGE (ESD) Precautions and Procedures

▲ CAUTION

Electrostatic discharge can affect electronic components. Take precautions to neutralize static charge by touching your hand and tools to metal before handling controls.

Make-Up Box Installation

The unit has a field make-up box on the left side of the cabinet, which can be moved to the right side. If moved, clip wire ties bundling wires and secure excess wire to the existing harness.

Diagram: Interior Make-Up Box Installation

Figure 20 illustrates the interior make-up box installation, showing how to extend power wires for right-side installation.

Wiring and Power Supply

Refer to Figures 21 or 23 for wiring diagrams and TABLE 9 for field wiring. Power supply wiring must meet Class I restrictions. Use a fuse or circuit breaker sized per the unit's nameplate.

▲ WARNING

Fire Hazard. Use of aluminum wire with this product can cause fire, property damage, severe injury, or death. Use only copper wire.

▲ CAUTION

Failure to use properly sized wiring and circuit breaker may result in property damage. Size wiring and breaker(s) per the Product Specifications bulletin (EHB) and unit rating plate. The unit nameplate indicates maximum current draw; maximum over-current protection is 15 AMP.

Holes are provided on both sides of the furnace cabinet for wiring. Install a separate, properly sized disconnect switch near the furnace for servicing.

Thermostat Wiring

Ensure thermostat wires are long enough for future servicing. Use 18-gauge wire or larger suitable for Class II rating. Electrically ground the unit per local codes or the National Electric Code (ANSI/NFPA No. 70). A green ground wire is provided. The EL280DFE furnace contains polarity-sensitive electronic components; ensure correct wiring and grounding.

▲ WARNING

Electric Shock Hazard. Can cause injury or death. Unit must be properly grounded in accordance with national and local codes.

Accessory Terminals

The integrated control has 1/4" spade terminals for accessories:

• EAC (1/4" spade): Line voltage, energized when the indoor blower operates. For accessories up to 1 amp. Connect neutral leg to a provided neutral terminal. For accessories over 1 amp, use an external relay.
• HUM (1/4" spade): Line voltage, energized in heating mode when the combustion air inducer operates. For humidifiers up to 1 amp. Connect neutral leg to a provided neutral terminal. For humidifiers over 1 amp, use an external relay.
• H (24V, 1/4" spade): Energized in heating mode when the combustion air inducer operates and the pressure switch is closed. For humidifiers up to 0.5 amp. Connect ground leg to ground or the "C" terminal.

Generator Use - Voltage Requirements

When specifying a generator:

• Furnace requires 120 volts + 10% (108-132 volts).
• Operates at 60 Hz + 5% (57-63 Hz).
• Requires proper polarity and ground. Check before operating.
• Generator should have waveform distortion less than 5% total harmonic distortion (THC).

Thermostat Installation

Install the thermostat per its instructions. Refer to TABLE 9 for thermostat designations. For heat pump applications, consult specific dual fuel thermostat instructions.

Indoor Blower Speeds

Blower operation depends on thermostat settings:

• FAN ON: Blower runs continuously on low heat speed when no heating/cooling demand. See TABLE 18 for allowable speeds.
• Heating Mode: Blower runs at corresponding heating speed (high-fire or low-fire).
• Cooling Mode: Blower runs at corresponding cooling speed (low or high cool).

TABLE 9: Field Wiring Applications With Conventional Thermostat

This table details DIP switch settings and on-board link configurations for various thermostat types (1 Heat/1 Cool, 1 Heat/2 Cool, 2 Heat/2 Cool, Dual Fuel) and their corresponding wiring connections to the thermostat, furnace terminal strip, and outdoor unit.

NOTE: * Not required on all units.

NOTE: Connect W1 to W1 ONLY if using defrost tempering kit 67M41. Do NOT make a wire connection between the room thermostat L terminal and the L terminal of the furnace integrated control.

Wiring Diagram With Integrated Control

Figures 21 and 23 provide schematic wiring diagrams for the EL280DFE furnace, showing connections for the integrated control, blower motor, gas valve, ignitor, sensors, and thermostat. Figure 22 and 24 detail the Integrated Control board, its terminals, and thermostat connection definitions.

Integrated Control DIP Switch Settings

The EL280DFE uses a two-stage integrated control for ignition timing, fan off delays, and blower speeds. An internal watchguard resets the ignition control after lockout. The control can relight the furnace after one hour of continuous heat demand.

Heating Operation DIP Switch Settings

• NOTE: Switch 8 is not powered and not used.
• Switch 1 (Thermostat Selection): Set for single-stage (ON) or two-stage (OFF) thermostat operation. Factory setting is OFF (two-stage).
• Switch 2 (Second Stage Delay): Used only with single-stage thermostats. OFF provides a 7-minute delay; ON provides a 12-minute delay before second-stage heat. Factory setting is OFF.

Indoor Blower Operation DIP Switch Settings

• Switches 3 & 4 (Heating Mode Blower-Off Delay): Adjusts blower-off delay (time blower runs after heating demand is met) to achieve desired supply air temperature. Factory setting is 90 seconds (OFF, OFF). Other settings: 60s (On, Off), 120s (Off, On), 180s (On, On).
• Switch 5 (Cooling Mode Blower-Off Delay): Factory setting is OFF for a 45-second delay. ON provides a 2-second delay.
• Switches 6 & 7 (Continuous Fan Mode): Control continuous fan speed. Factory setting for Low Heat Speed is Off, Off.

▲ WARNING

Carefully review all configuration information. Improperly set DIP switches, jumpers, and on-board links can result in improper operation.

On-Board Link Functions

• W914 Dehum: Cut if thermostat has humidity control. If not cut, terminal "DS" remains energized, preventing low cool speed for dehumidification.
• W951 Heat Pump (R to O): Cut if a heat pump unit and dual fuel thermostat are used. If intact, terminal "O" remains energized, eliminating HEAT MODE in heat pump.
• W915 2 Stage Compr (Y1 to Y2): Cut if two-stage cooling is used. If not cut, outdoor unit operates in second-stage cooling only.

Diagnostic Push Button

Adjacent to the diagnostic LED, this button enables Error Code Recall (“E” mode) and Flame Signal (“F” mode). Press and hold to cycle through options; each new item displays every five seconds. Releasing the button selects the item.

Unit Start-Up

▲ WARNING

Do not use a furnace that has been underwater; it is extremely dangerous and can cause fire or explosion. Call a qualified service technician immediately.

▲ WARNING

If overheating occurs or gas supply fails to shut off, shut off the manual gas valve before shutting off electrical supply.

▲ CAUTION

Before any service or maintenance, turn off electrical power at the disconnect switch.

Smell around the appliance area for gas before lighting. Some gases are heavier than air and settle on the floor.

The gas valve has a control switch; use only your hand to move it. Do not use tools.

Placing the Furnace into Operation

EL280DFE units have an automatic ignition system; do not attempt to light burners manually. Burners light automatically when the thermostat calls for heat. The ignitor does not get hot when there is no call for heat.

▲ WARNING

Failure to follow these instructions exactly may result in fire or explosion, causing property damage, personal injury, or death.

Gas Valve Operation (FIGURE 25 & 26)

1. Read safety information.
2. Set thermostat to lowest setting.
3. Turn off all electrical power.
4. The furnace has an automatic ignition device; do not light burners by hand.
5. Remove the upper access panel.
6. Move the gas valve switch to OFF (do not force).
7. Wait five minutes to clear out any gas. If gas is smelled, STOP and call the gas supplier. If no gas is smelled, proceed.
8. Move the gas valve switch to ON (do not force).
9. Replace the upper access panel.
10. Turn on all electrical power.
11. Set the thermostat to the desired setting.

NOTE: Steps 1-11 may need repeating to purge air from the gas line on initial start-up.

If the appliance does not operate, follow "Turning Off Gas to Unit" instructions and call a service technician or gas supplier.

Turning Off Gas to Unit

1. Set thermostat to lowest setting.
2. Turn off all electrical power if service is to be performed.
3. Remove upper access panel.
4. Move gas valve switch to OFF (do not force).
5. Replace upper access panel.

Failure To Operate

Check the following if the unit fails to operate:

• Is the thermostat calling for heat?
• Are access panels securely in place?
• Is the main disconnect switch closed?
• Is there a blown fuse or tripped circuit breaker?
• Is the filter dirty or plugged? (This can cause the limit control to shut off the unit.)
• Is gas turned on at the meter?
• Is the manual main shut-off valve open?
• Is the internal manual shut-off valve open?
• Is the unit ignition system in lockout? If it locks out again, call a service technician.
• Is the pressure switch closed? (Obstructed flue can cause shutoff at the pressure switch.) Check flue and outlet for blockages.
• Are flame rollout switches tripped? If so, call a service technician.

Diagrams: Gas Valve Operation

Figures 25 and 26 show the White Rodgers and Resideo gas valves, illustrating the ON/OFF switch, inlet pressure post, manifold pressure tap, and high/low fire adjustment screws.

Gas Pressure Adjustment

Gas Flow (Approximate)

Operate furnace for at least 5 minutes before checking gas flow. Determine time in seconds for two meter revolutions (for accuracy). Divide by two and compare to TABLE 13. If manifold pressure matches TABLE 15 but rate is incorrect, check gas orifices for proper size and restriction.

NOTE: Shut off all other gas appliances connected to the meter for accurate reading. Remove temporary gas meter if installed.

Supply Pressure Measurement

An inlet post on the gas valve provides access to supply pressure. Back out the 3/32" hex screw one turn, connect 5/16" tubing to a manometer to measure supply pressure. See TABLE 15 for supply line pressure.

Manifold Pressure

A manifold pressure tap on the gas valve provides access to manifold pressure. Back out the 3/32" hex screw one turn, connect 5/16" tubing to a manometer. NOTE: Pressure test adapter kit (10L34) is available from Lennox.

1. Connect test gauge to manifold pressure tap.
2. Ignite unit on low fire; let run for 5 minutes to stabilize.
3. Record manifold pressure and compare to TABLE 15. Make adjustments if necessary (see Figure 25 for adjustment screw locations).
4. Repeat steps 2-4 for high fire.
5. Shut unit off, remove manometer, and replace pressure tap plug.
6. Start unit and perform leak check. Seal leaks if found.

Proper Combustion

Operate furnace for minimum 15 minutes with correct manifold pressure and gas flow before checking combustion. TABLE 14 shows acceptable combustion for all EL280DFE models. Maximum carbon monoxide reading should not exceed 100 ppm.

High Altitude

Manifold pressure and combustion air pressure switch may require adjustment for proper combustion at higher altitudes. Refer to TABLE 15 for manifold pressure and TABLE 16 for pressure switch and gas conversion kits.

IMPORTANT

For safety, shut unit off and remove manometer as soon as an accurate reading has been obtained. Take care to replace pressure tap plug.

¹ This is the only permissible derate for these units.

² Natural gas high altitude orifice kit required.

³ A natural to L.P. propane gas changeover kit is necessary to convert this unit. Refer to the changeover kit installation instruction for the conversion procedure.

NOTE - Units may be installed at altitudes up to 4500 ft. above sea level without modifications.

NOTE - A natural to L.P. propane gas changeover kit is necessary to convert this unit. Refer to the changeover kit installation instruction for the conversion procedure.

Other Unit Adjustments

Primary and Secondary Limits

The primary limit is in the heating compartment vestibule panel. Secondary limits (if equipped) are in the blower compartment. These auto-reset limits are factory-set and require no adjustment.

Flame Rollout Switches

The manual reset switch is on the front of the burner box.

Pressure Switch

Located in the heating compartment adjacent to the combustion air inducer. It checks for proper inducer operation before allowing ignition trial. Factory-set and requires no adjustment.

Temperature Rise

After starting and stabilizing temperatures, check temperature rise. Adjust blower speed to maintain the range shown on the unit nameplate (TABLE 17). Increasing blower speed decreases temperature rise; decreasing speed increases it. Failure to adjust may cause erratic limit operation.

Input Voltage Requirements

The circuit is designed for AC voltage. 12 to 33VAC is required to energize the motor. Expected current draw is less than 20mA.

Blower Speeds

To change blower speeds:

1. Turn off electrical power.
2. Remove blower access panel.
3. Disconnect existing speed tap at integrated control speed terminal. (Insulate unused motor leads.)
4. Place unused speed tap on integrated control "PARK" terminal or insulate.
5. Refer to blower speed selection chart (wiring diagram) and Blower performance data (TABLE 17) for desired speed.
6. Connect selected speed tap to integrated control speed terminal.
7. Re-secure blower access panel.
8. Turn on electrical power.
9. Recheck temperature rise.

Electronic Ignition

The integrated control features an internal Watchguard control that acts as an automatic reset device for ignition control lockout caused by ignition failure (often due to low gas pressure). After one hour of continuous thermostat demand for heat, the Watchguard breaks and remakes thermostat demand to reset the control for ignition.

Heating Sequence of Operation

The EL280DFE's integrated control has a Watchguard feature for automatic reset of ignition control lockout. After one hour of continuous heat demand, it resets the control for ignition. The ignition control thermostat selection DIP switch is factory-set to "TWO-STAGE".

Applications Using a Two-Stage Thermostat

A - Heating Sequence (DIP Switch 1 OFF - "Two-Stage" Factory Setting):

1. On a heat call, thermostat first-stage contacts close. Control performs diagnostics, checks limit and pressure switches. Combustion air inducer energizes at low speed.
2. When low pressure switch closes, inducer starts a 15-second low-speed pre-purge. (If low fire pressure switch doesn't close, inducer switches to high fire. High fire pressure switch closes, unit operates on high fire for 10-20 seconds, then switches to low fire.)
3. After pre-purge, a 20-second ignitor warm-up period begins; inducer continues at low speed.
4. After warm-up, gas valve energizes on low fire (first stage), ignition occurs. Indoor blower starts a 30-second ON-delay. When delay ends, blower energizes on low fire heating speed, HUM contacts close (energizing humidifier and 120V ACC terminal). Furnace continues as long as first-stage heat demand exists.
5. If second-stage heat is required, thermostat second-stage contacts close. Control initiates a 30-second second-stage recognition delay.
6. After recognition delay, control energizes inducer at high speed. Checks high fire pressure switch. High fire gas valve energizes, and blower operates at high fire heating speed.
7. When high-stage heat demand is satisfied, inducer switches to low-speed, high-fire gas valve de-energizes. Low-fire gas valve continues. Blower switches to low-fire heating speed.
8. When low-fire heat demand is satisfied, gas valve de-energizes. Indoor blower off delay begins. Inducer starts a 5-second post-purge.
9. After post-purge, inducer and HUM contacts de-energize. Blower de-energizes at end of off delay, as do ACC terminals.

Applications Using a Single-Stage Thermostat

B - Heating Sequence (DIP Switch 1 ON - "Single-Stage" Position):

NOTE: Two-stage heat will initiate if heating demand is not satisfied after the field adjustable period (7 or 12 minutes).

1. On a heat call, thermostat first-stage contacts close. Control performs diagnostics, checks limit and pressure switches. Combustion air inducer energizes at low speed.
2. When low pressure switch closes, inducer starts a 15-second low-speed pre-purge. (If low fire pressure switch doesn't close, inducer switches to high fire. High fire pressure switch closes, unit operates on high fire for 10-20 seconds, then switches to low fire.)
3. After pre-purge, a 20-second ignitor warm-up period begins; inducer continues at low speed.
4. After warm-up, gas valve energizes on low fire (first stage), ignition occurs. Indoor blower starts a 30-second ON-delay. When delay ends, blower energizes on low fire heating speed, HUM contacts close. Control initiates a second-stage on delay (factory-set 7 min, adjustable to 12 min).
5. If heating demand continues beyond the second-stage on delay, control energizes inducer at high speed. Checks high fire pressure switch. High fire gas valve energizes, and blower operates at high fire heating speed.
6. When heating demand is satisfied, inducer begins a 5-second low-speed post-purge. Indoor blower off delay begins. Blower operates at low-fire heating speed.
7. After post-purge, inducer and HUM contacts de-energize. Blower de-energizes at end of off delay, as do ACC terminals.

Service

▲ WARNING

ELECTRICAL SHOCK, FIRE, OR EXPLOSION HAZARD. Failure to follow safety warnings exactly could result in dangerous operation, serious injury, death, or property damage. Improper servicing could result in dangerous operation, serious injury, death, or property damage. Before servicing, disconnect all electrical power to furnace. When servicing controls, label all wires prior to disconnecting. Reconnect wires correctly. Verify proper operation after servicing.

▲ WARNING

The blower access panel must be securely in place when the blower and burners are operating. Gas fumes, which could contain carbon monoxide, can be drawn into living space, resulting in personal injury or death.

Annual Furnace Maintenance

At the beginning of each heating season, and to comply with the Lennox Limited Warranty, have your system checked by a licensed professional technician:

1. Check wiring for loose connections, voltage, and motor amperage.
2. Check belt and shaft bearings condition.
3. Inspect all gas pipe and connections for leaks.
4. Check filter cleanliness and change monthly if necessary.
5. Check burner and heat exchanger condition and cleanliness; clean if necessary.
6. Check blower assembly cleanliness; clean housing, wheel, and motor if needed. Motors are prelubricated for extended bearing life.
7. Inspect and clean combustion air inducer if necessary.
8. Evaluate heat exchanger integrity per AHRI procedure (www.ahrinet.org).
9. Ensure sufficient combustion air is available. Fresh air grilles/louvers must be properly sized, open, and unobstructed.
10. Inspect venting system for proper installation, structural soundness, absence of holes, corrosion, or blockage. Vent system must be free of obstructions and slope upward away from the furnace, installed per National Fuel Gas Code.
11. Inspect furnace return air duct connection for seal and air leaks; seal where necessary.
12. Check furnace cabinet insulation condition and repair if needed.
13. Perform complete combustion analysis to ensure proper combustion and operation. Consult Service Literature for values.
14. Verify CO detector operation and replace batteries as required.

Perform a general system test, checking start-up and shut-off operations:

1. Check ignition system, clean flame sensor, check microamps. Check controls and safety devices (gas valve, flame sensor, temperature limits). Consult Service Manual for proper operating range. Thermal limits should be checked by restricting airflow (not disconnecting blower). See Service and Application Note H049.
2. Verify system total static pressure and airflow settings are within parameters.
3. Clock gas meter to ensure specified firing rate. Check supply and manifold pressures. For two-stage furnaces, check manifold pressure on high and low fire. Adjust gas pressure if necessary, consulting Service Literature. Not all gas valves are adjustable. Verify correct temperature rise.

Cleaning the Burners

NOTE: Use protective covering in front of the furnace during cleaning.

1. Turn off electrical and gas power supplies.
2. Label and disconnect wires from gas valve, rollout switches, primary limit switch, and make-up box.
3. Disconnect gas supply piping. Remove four screws securing the burner manifold assembly to the vestibule panel and remove it.
4. Remove four screws securing the burner box and remove it.
5. Clean burners using a vacuum cleaner with a soft brush attachment. Inspect inside burners and crossovers for foreign matter blockage. Remove any blockage (Figure 26 shows burner detail).
6. Reinstall burner box, manifold assembly, and burner box cover.
7. Reconnect all wires.
8. Reconnect gas supply piping.
9. Turn on power and gas supply.
10. Set thermostat and check for proper operation.
11. Check all piping connections for gas leaks using a leak detecting solution or other preferred means.

▲ CAUTION

Some soaps used for leak detection are corrosive to certain metals. Rinse piping thoroughly after leak test. Do not use matches, candles, flame, or other ignition sources for leak checks.

If a leak is detected, shut off gas and electricity and repair the leak. Repeat steps until no leaks are detected. Replace access panel.

Diagram: Burner Removal

Figure 27 illustrates the burner removal process, showing the ignitor, rollout switches, sensor, manifold and gas valve, retention rings, and crossover.

Repair Parts List

Repair parts are available through independent Lennox dealers. When ordering, include the complete furnace model number (e.g., EL280DF070E36A). All service must be performed by a licensed professional installer, service agency, or gas supplier.

Cabinet Parts

• Main access panel
• Blower access panel
• Top cap

Control Panel Parts

• Transformer
• Integrated control
• Door interlock switch
• Circuit breaker

Blower Parts

• Blower wheel
• Blower housing
• Motor
• Motor mounting frame
• Blower housing cutoff plate

Heating Parts

• Flame Sensor
• Heat exchanger assembly
• Gas manifold
• Combustion air inducer
• Gas valve
• Main burner cluster
• Main burner orifices
• Pressure switches
• Ignitor
• Primary limit control
• Flame rollout switch
• Secondary limit

Start-Up & Performance Check List

UNIT SET UP (typical)

Unit Model Number: ________________________ Serial Number: ________________________

Diagram shows numbered steps for checks:

1. GAS SUPPLY: Natural Gas / LP/Propane Gas, Piping Connections Tight, Leak Tested, Supply Line Pressure " W.C.________
2. VENT / EXHAUST PIPE: Secure to Unit, Elbows Secured to Pipe, Roof Flashing (water tight), Vent Pipe Supported
3. DUCT SYSTEM: SUPPLY AIR DUCT - Sealed, Insulated (if necessary), Registers Open and Unobstructed. RETURN DUCT - Sealed, Filter Installed and Clean, Grilles Unobstructed.
4. INTEGRATED CONTROL: DIP Switches Set (if applicable), Appropriate Links in Place (if applicable).
5. VOLTAGE CHECK: Supply Voltage _________, Electrical Connections Tight.

UNIT OPERATION (typical)

Diagram shows measurement points:

HEATING MODE

1. GAS MANIFOLD PRESSURE "W.C._____
2. COMBUSTION SAMPLE CO2%_____ CO PPM_______
3. INDOOR BLOWER AMPS______
4. TEMPERATURE RISE: Supply Duct Temperature ______, Return Duct Temperature ______, Temperature Rise = ______
5. TOTAL EXTERNAL STATIC (dry coil): Supply External Static ______, Return External Static + ______, Total External Static = ______

COOLING MODE

1. INDOOR BLOWER AMPS______
2. TEMPERATURE DROP: Return Duct Temperature ______, Supply Duct Temperature ______, Temperature Drop = ______
3. TOTAL EXTERNAL STATIC (dry coil): Supply External Static ______, Return External Static + ______, Total External Static = ______
4. DRAIN LINE: Leak Free
5. THERMOSTAT: Adjusted and Programmed, Operation Explained to Owner

Contractor's Name: _________________________ Telephone: _________________________ Checklist Completed: ____________________

Job Address: _________________________________ Technician's Name: _________________________________

Blower Data

EL280DF070E36A PERFORMANCE (Less Filter)

Table shows Air Volume / Watts at Various Blower Speeds based on External Static Pressure.

EL280DF090E48B PERFORMANCE (Less Filter)

Table shows Air Volume / Watts at Various Blower Speeds based on External Static Pressure.