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© 2025 Lennox Industries Inc.
Dallas, Texas USA
THIS MANUAL MUST BE LEFT WITH THE HOME-
OWNER 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.
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 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
Parts Arrangement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
SL280UHVK Gas Furnace . . . . . . . . . . . . . . . . . . . . . . . . . 4
Shipping and Packing List . . . . . . . . . . . . . . . . . . . . . . . . 4
Safety Information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
Setting Equipment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
Filters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
Duct System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
Venting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
Gas Piping . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
the
refrigerant
detection
. . . . . . . . . . . 5
. . . . . . . . . . . . . . 6
INSTALLATION
INSTRUCTIONS
SL280UHVK
DAVE LENNOX SIGNATURE
GAS FURNACE UPFLOW / HORIZONTAL
AIR DISCHARGE
508553-01
01/2025
NOTICE
A thermostat is not included and must be ordered
separately.
• A Lennox communicating thermostat must be used in
communicating applications.
• In non-communicating applications, the Lennox
ComfortSense® 7500 thermostat may be used, as well
as other non-communicating thermostats.
In all cases, setup is critical to ensure proper system
operation.
Field
wiring
for
both
communicating applications is illustrated in diagrams,
which begin on Page 27.
IMPORTANT
DO NOT use the heat exchanger bracket to lift, drag
or pull the furnace to its installation location. Doing so
will loosen the bracket causing noise and or unsafe
operation.
Bracket
Electrical . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
Ignition Control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30
Low GWP Application . . . . . . . . . . . . . . . . . . . . . . . . . . . 41
Unit Start-Up . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44
Gas Pressure Adjustment . . . . . . . . . . . . . . . . . . . . . . . . 45
Proper Combustion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46
High Altitude . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46
Other Unit Adjustments . . . . . . . . . . . . . . . . . . . . . . . . . . 46
Heating Sequence of Operation . . . . . . . . . . . . . . . . . . . 47
Service . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49
Repair Parts List . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51
Blower Data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52
Program Unit Capacity/Size Mode . . . . . . . . . . . . . . . . . 55
Troubleshooting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56
Page 1
®
communicating
and
non-
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Related Manuals for Lennox SIGNATURE SL280UHVK
Summary of Contents for Lennox SIGNATURE SL280UHVK
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Page 1: Table Of Contents
01/2025 NOTICE A thermostat is not included and must be ordered separately. • A Lennox communicating thermostat must be used in communicating applications. • In non-communicating applications, the Lennox ComfortSense® 7500 thermostat may be used, as well as other non-communicating thermostats. -
Page 2: Unit Dimensions
Unit Dimensions - inches (mm) 3-1/8 (79) NOTE - 60C and 60D size units that require air volumes over 1800 cfm must have one of the following: 1. Single side return air and Optional Return Air Base with transition that must accommodate required SUPPLY AIR FLUE OUTLET 20 x 25 x 1 inch (508 x 635 x 25 mm) air filter to... -
Page 3: Parts Arrangement
Parts Arrangement Parts Arrangement HEAT EXCHANGER COMBUSTION AIR INDUCER COMBUSTION AIR INDUCER PRESSURE SWITCH GAS VALVE CABINET BURNER BOX INNER BLOWER PRIMARY LIMIT ACCESS PANEL SIGHT GLASS SECONDARY LIMITS (2 switches) ACCESS PANEL BLOWER ASSEMBLY CONTROL BOX (with blower drive in some units. -
Page 4: Sl280Uhvk Gas Furnace
CAUTION SL280UHVK Gas Furnace The SL280UHVK unit is shipped ready for installation As with any mechanical equipment, contact with sharp in the upflow or horizontal right position (for horizontal sheet metal edges can result in personal injury. Take left position the combustion air pressure switch must be care while handling this equipment and wear gloves and moved). -
Page 5: Use Of Furnace As A Construction Heater
Use of Furnace as Construction Heater When this furnace is used with cooling units, it shall be Lennox does not recommend the use of SL280UHVK installed in parallel with, or on the upstream side of, cool- units as a construction heater during any phase of con- ing units to avoid condensation in the heating compart- struction. -
Page 6: Combustion, Dilution & Ventilation Air
• Do not install the furnace where drafts might blow CAUTION directly into it. This could cause improper combus- Insufficient combustion air can cause headaches, tion and unsafe operation. nausea, dizziness or asphyxiation. It will also cause • Do not block the furnace combustion air openings excess water in the heat exchanger resulting in with clothing, boxes, doors, etc. -
Page 7: Confined Space
Though an area may appear to be confined, it might be Air from Inside necessary to bring in outdoor air for combustion if the If the confined space that houses the furnace adjoins a structure does not provide enough air by infiltration. If the space categorized as unconfined, air can be brought in by furnace is located in a building of tight construction with providing two permanent openings between the two spac-... - Page 8 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 9: Setting Equipment
Upflow Applications Setting Equipmet Allow for clearances to combustible materials as indicated WARNING on the unit nameplate. Minimum clearances for closet or alcove installations are shown in FIGURE 7. Do not install the furnace on its front or its back. Do Upflow Application Installation Clearances not connect the return air ducts to the back of the furnace. - Page 10 Return Air -- Upflow Applications Single Side Return Air Return air can be brought in through the bottom or either (with transition and filter) side of the furnace installed in an upflow application. If the furnace is installed on a platform with bottom return, make an airtight seal between the bottom of the furnace and the platform to ensure that the furnace operates properly and safely.
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Page 11: Horizontal Applications
Pivot the bottom cap down to release the bottom applications. Order horizontal suspension kit (51W10) panel. Once the bottom panel has been removed, reinstall from Lennox, or use equivalent suspension method. the bottom cap. See FIGURE 10. Allow for clearances to combustible materials as indicated on the unit nameplate. -
Page 12: Filters
Use screws and joint specifications provided by the filter manufacturer tape to seal the return air system to the furnace. against the data given in the appropriate Lennox In platform installations with bottom return air, the Product Specifications bulletin. -
Page 13: Duct System
Return Air Plenum Duct System NOTE - Return air must not be drawn from a room Use industry-approved standards (such as those pub- where this furnace, or any other gas-fueled appliance lished by Air Conditioning Contractors of America or Amer- (i.e., water heater), or carbon monoxide- producing ican Society of Heating, Refrigerating and Air Condition- device (i.e., wood fireplace) is installed. -
Page 14: Venting
If necessary reposition the combustion air inducer, pres- Venting sure switch and or make up box as needed per the follow- A 4-inch diameter flue transition is factory-installed on the ing steps and see FIGURE 17 through FIGURE 22. combustion air inducer outlet of all models. FIGURE 15 1 - Remove the four mounting screws which secure the shows the combustion air inducer as shipped from the combustion air inducer / pressure switch assembly... - Page 15 HORIZONTAL LEFT POSITION HORIZONTAL RIGHT POSITION Top Vent Discharge Top Vent Discharge vent pipe pressure switch vent pipe pressure switch flue transition flue cover plate transition FLOW FLOW collector box cover plate make-up box collector box Disconnect sure switch assembly. Remove pressure switch assembly (1 make-up box screw) and cut wire tie to free pressure switch wires.
- Page 16 The SL280UHVK series units are classified as fan-assist- Venting Using a Masonry Chimney ed Category I furnaces when vertically vented according The following additional requirements apply when a lined to the latest edition of National Fuel Gas Code (NFPA 54 masonry chimney is used to vent this furnace.
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Page 17: General Venting Requirements
When inspection reveals that an existing chimney is not Common Venting Using Metal-Lined Masonry Chimney safe for the intended purpose, it shall be rebuilt to conform to nationally recognized standards, lined or relined with SEALED suitable materials, or replaced with a gas vent or chimney MAX. - Page 18 Common Venting Using Tile-Lined Interior Masonry Chimney and Combined Vent Connector MINIMUM LENGTH = AS SHORT AS PRACTICAL. INTERIOR TILE-LINED FOR MAXIMUM LENGTH SEE NOTE TO LEFT MASONRY CHIMNEY NOTE- Refer to provided venting tables for installations. NOTE - the chimney must be properly sized per provided venting tables or lined with listed metal lining system.
- Page 19 16 - Vent connectors serving Category I appliances shall 20 - Do not install a manual damper, barometric draft not be connected to any portion of mechanical draft regulator or flue restrictor between the furnace and systems operating under positive pressure such as the chimney.
- Page 20 TABLE 4 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 5...
- Page 21 Removal of the Furnace from Common Vent 3 - Close all building doors and windows and all doors between the space in which the appliances In the event that an existing furnace is removed from a remaining connected to the common venting system venting system commonly run with separate gas applianc- are located and other spaces of the building.
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Page 22: Gas Piping
2 - When connecting the gas supply piping, consider Gas Piping factors such as length of run, number of fittings, and Gas supply piping should not allow more than 0.5”W.C. furnace rating to avoid excessive pressure drop. drop in pressure between gas meter and unit. Supply gas TABLE 6 lists recommended pipe sizes for typical pipe must not be smaller than unit gas connection. -
Page 23: Horizontal Application
Left Side Piping MANUAL (Standard) MAIN SHUT-OFF AUTOMATIC MANUAL VALVE GAS VALVE MAIN SHUT-OFF (With 1/8 in. NPT AUTOMATIC VALVE Plugged Tap GAS VALVE (With 1/8 in. NPT Shown) Plugged Tap Shown) GROUND JOINT UNION GROUND JOINT UNION DRIP LEG Right Side Piping FIELD (Alternate) -
Page 24: Electrical
Leak Check IMPORTANT After gas piping is completed, carefully check all field-in- When matching this gas furnace with zoning, stalled piping connections for gas leaks. Use a commer- defrost tempering stat or other 24V accessories, cially available leak detecting solution specifically manu- It is recommended to replace the factory installed factured for leak detection. - Page 25 TWOSTAGE mode using a conventional thermostat. servicing. For optimal performance in non-communicating applica- 4 - Before connecting the thermostat or the power wiring, tions, Lennox recommends use of a ComfortSense 7000 ® check to make sure the wires will be long enough for high quality electronic digital thermostat or any other with servicing at a later date.
- Page 26 Indoor Blower Speeds Generator Use - Voltage Requirements The following requirements must be kept in mind when Non-Communicating 1 - When the thermostat is set to “FAN ON,” the indoor specifying a generator for use with this equipment: blower will run continuously at a field selectable •...
- Page 27 Communicating Enabled Furnace and Non- Communicating Enabled Furnace and Communicating Outdoor Unit Communicating Enabled Outdoor Unit COMMUNICATING FURNACE COMMUNICATING FURNACE OPTIONAL DISCHARGE AIR SENSOR OPTIONAL DISCHARGE AIR SENSOR OPTIONAL OUTDOOR OPTIONAL COMMUNICATING AIR SENSOR OUTDOOR THERMOSTAT AIR SENSOR COMMUNICATING THERMOSTAT DOOR AIR CONDITIONING OR HEAT PUMP UNIT NON-COMMUNICATING...
- Page 28 Optional Accessories for use with any Communicating System NOTE: ICOMMUNICATING THERMOSTAT SENSES HUMIDITY & CONTROLS HUM CONTACTS TO CYCLE HUMIDIFIER BASED 120V CONNECTIONS QUIRED. “HUM” CONTACT IS CLOSED ANYTIME HUMIDITY DEMAND IS PRESENT TIONS. BUILT INTO ALL COMMUNICATING ENABLED OUT DOOR UNITS).
- Page 29 LENNOX COMMUNICATING OUTDOOR UNIT INDOOR UNIT (1 OR 2 STAGE) FLOAT SWITCH LENNOX COMMUNICATING OUTDOOR UNIT LENNOX COMMUNICATING FURNACE EL297VK, SL280VK, SL280VNK, SL297VK, SLP99VK cutting DS to R will not cause communication interuption or error code CUT* R-DS W914 FIGURE 32...
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Page 30: Ignition Control
Ignition Control FIGURE 33 TABLE 10 THERMOSTAT INPUT TERMINALS TABLE 8 LOW STAGE HEAT 1/4”QUICK CONNECT TERMINALS HIGH STAGE HEAT 120 VAC OUTPUT TO HUMIDIFIER XMFR 120 VAC OUTPUT TO TRANSFORMER LOW STAGE COOL 120 VAC INPUT TO CONTROL HIGH STAGE COOL24 CIRC 120 VAC OUTPUT TO CIRCULATING THERMOSTAT COMMON / GROUND... - Page 31 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 32 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...
- Page 33 TABLE12 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. STRIP Single Stage Heat Pump CUT ON-BOARD LINK...
- Page 34 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.
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Page 35: Wiring Diagram
Wiring Diagram COMBUSTION AIR BLOWER MOTOR DOOR IGNITOR INTERLOCK CIRC FLAME FLAME SENSE WHT/PINK SENSOR 120V BLUE BLUE MV COM PINK PINK S102 HIGH HEAT PRESSURE SWITCH PURPLE PURPLE S128 LOW HEAT PRESSURE SWITCH BLUE BLUE BRN W / YEL RO(OUT) STRIPE GRN/YEL... -
Page 36: Ignition Control Diagnostic Codes
Ignition Control Diagnostic 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 37 Ignition Control Diagnostic Codes (continued) SOFT LOCKOUT FAULTS (60 MINUTES) UNABLE TO COMMUNICATE WITH CIRCULAR MOTOR E201 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 38 TABLE 13 Ignition Control DIP Switch Settings - Blower Off Delay Conventional Thermostat (non-communicating) Switch 3 Switch 4 Seconds SL280UHVK units are equipped with a two-stage, vari- able speed integrated control. This control manages igni- 90 (factory) tion timing, heating mode fan off delays and indoor blower speeds based on selections made using the control dip switches and jumpers.
- Page 39 TABLE 16 Ramping Option D Cooling Mode Blower Speed Ramping • Motor runs at 100% until demand is satisfied. • Once demand is met, motor ramps down to stop. Ramping Switch 9 Switch 10 A (Factory) 100% CFM COMPRESSOR DEMAND Switches 11, 12 and 13 -- Heating Mode Blower Speed The switches are factory set to the OFF position which provides factory default heat speed.
- Page 40 On-Board Link W915 2 Stage Compr (Y1 to Y2) On-Board Links On-board link W915 is a clippable connection between Note: In a communication system with a conventional terminals Y1 and Y2 on the integrated control. W915 must outdoor unit (non-communicating), the on-board clippable be cut if two-stage cooling will be used.
- Page 41 TABLE 19 OPERATING SEQUENCE SL280UHVK, Non-Communicating Thermostat with Humidity Control Feature and Single-Speed Outdoor Unit OPERATING SEQUENCE SYSTEM DEMAND SYSTEM RESPONSE Thermostat Demand Relative Humidity Blower System Compre Step Comments ssor Condition Status (cool) NO CALL FOR DEHUMIDIFICATION Compressor and Normal Operation Acceptable High...
- Page 42 TABLE 20 OPERATING SEQUENCE SL280UHVK, Non-Communicating Thermostat with Humidity Control Feature and Two-Speed Outdoor Unit OPERATING SYSTEM DEMAND SYSTEM RESPONSE SEQUENCE Thermostat Demand Relative Humidity Blower System Compre Step Comments ssor Condition Status (cool) NO CALL FOR DEHUMIDIFICATION Normal Operation Acceptable 70%* Compressor and indoor...
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Page 43: Low Gwp Application
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 37 and follow steps below: 1 - Route sensor wire #1 through provided grommet. - Page 44 FURNACE CONTROL BOARD LOW GWP MODES OF 2. The furnace control board activates the blower (high OPERATION speed). The blower purges refrigerant from the cabinet, plenum, and ductwork. The modes of operation for the furnace control board are Initializing, Normal, Leak Detected, and Fault. 3.
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Page 45: 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 46: Unit Start-Up
2 - Set the thermostat to the lowest setting. Unit Start-Up 3 - Turn off all electrical power to the unit. FOR YOUR SAFETY READ BEFORE LIGHTING 4 - This furnace is equipped with an ignition device WARNING which automatically lights the burners. Do not try to light the burners by hand. -
Page 47: Gas Pressure Adjustment
NOTE - Pressure test adapter kit (10L34) is available from unit for blockages. Lennox to facilitate manifold pressure measurement. 10 - Is pressure switch closed? Obstructed flue will 1 - Connect test gauge to manifold pressure tap on gas cause unit to shut off at pressure switch. -
Page 48: Proper Combustion
TABLE 26 Proper Combustion Gas Valve Conversion Kits Furnace should operate minimum 15 minutes with correct manifold pressure and gas flow rate before checking com- High Altitude bustion. TABLE 25 shows acceptable combustion for ALL Natural Gas to LP/ Propane Natural Gas EL280UHEK models. -
Page 49: Other Unit Adjustments
Other Unit Adjustments Heating Sequence of Operation Primary and Secondary Limits Applications Using Two-Stage Thermostat See FIGURE 39 for ignition control sequence The primary limit is located on the heating compartment A - Heating Sequence Integrated Control Thermostat vestibule panel. The secondary limits (if equipped) are lo- Selection DIP Switch 1 OFF in “Two-Stage”Position cated in the blower compartment, attached to the back (Factory Setting) - Page 50 Applications Using Single-Stage Thermostat 4 - After the 20-second warm-up period has ended, the See FIGURE 40 for ignition control sequence gas valve is energized on low fire (first stage) and ignition occurs. At the same time, the control module B - Heating Sequence -- Integrated Control Thermostat sends a signal to begin an indoor blower 30-second Selection DIP Switch 1 ON in “Single-Stage”...
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Page 51: Service
1 - Check the operation of the ignition system, inspect At the beginning of each heating season, and to comply and clean flame sensor. Check microamps before with the Lennox Limited Warranty, your system should be and after. Check controls and safety devices (gas checked as follows: valve, flame sensor, temperature limits). - Page 52 Cleaning the Burners 4 - To clean burners, run a vacuum cleaner with a soft brush attachment over the face of burners. Visually NOTE - Use papers or protective covering in front of the inspect inside the burners and crossovers for any furnace during cleaning.
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Page 53: Repair Parts List
Heating Parts Repair Parts Flame Sensor The following repair parts are available through indepen- Heat exchanger assembly dent Lennox dealers. When ordering parts, include the complete Gas manifold furnace model number listed on the CSA International Two-speed combustion air inducer nameplate -- Example: SL280UH070V36AK. -
Page 54: Blower Data
First stage COOL (two-stage air conditioning units only) is approximately 70% of the same second stage COOL speed position. Continuous Fan Only speed is selectable at 28% and 38% of the selected second stage cooling speed - minimum 250 cfm. Lennox Smart Zoning System Applications - Minimum blower speed is 250 cfm. - Page 55 Continuous Fan Only speed is selectable at 28% and 38% of the selected second stage cooling speed - min 380 cfm 090V48B, min 450 cfm 090V60C. Lennox Smart Zoning System Applications - Minimum blower speed is 380 cfm 090v48C, 450 cfm. 090V60C ®...
- Page 56 First stage COOL (two-stage air conditioning units only) is approximately 70% of the same second stage COOL speed position. Continuous Fan Only speed is selectable at 28% and 38% of the selected second stage cooling speed - minimum 450 cfm. Lennox Smart Zoning System Applications - Minimum blower speed is 450 cfm.
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Page 57: Program Unit Capacity/Size Mode
Program Unit Capacity / Size Mode − − Power-Up - Number displayed represents by integrated control unit size code (furnace model − and capacity). If three horizontal bars are displayed followed by continuous E203, furnace control does not recognize unit size code. Configure per the following: Furnace control in IDLE mode No heating, cooling or indoor fan operation) -
Page 58: Troubleshooting
Troubleshooting CALL FOR FIRST-STAGE HEAT CALL FOR 1ST STAGE HEAT (LOW FIRE) INDOOR BLOWER OFF AFTER HEAT FAN OFF DELAY (LOW HEAT SPEED) INDOOR LIMIT BLOWER OFF HIGH ERROR SWITCH INDOOR WATCHGUARD − AFTER HEAT FAN LIMIT SWITCH CODE BLOWER CLOSED WITHIN 3 ERROR CODE OFF DELAY (LOW... - Page 59 Troubleshooting CALL FOR SECOND-STAGE HEAT CALL FOR 2ND STAGE HEAT (HIGH FIRE) SINGLE STAGE 2 STAGE THERMOSTAT THERMOSTAT 2ND STAGE RECOGNITION DELAY ON DELAY (30 SECONDS) EXPIRED? EXPIRED? ONLY FOR 1ST REQUEST FOR 2ND STAGE HEAT INDUCER SWITCHED TO HIGH SPEED HIGH PRESSURE SWITCH INDUCER SWITCHED...
- Page 60 Troubleshooting CALL FOR HEAT SATISFIED FIRST-STAGE HEAT SECOND-STAGE HEAT RUN MODE: 1ST OR 2ND STAGE CALL FOR HEAT. ALL INPUTS MONITORED (LIMIT, PRESSURE, CALL FOR HEAT/COOL, FLAME LEVEL) 2ND STAGE HEAT 2ND STAGE CALL FOR HEAT SATISFIED? DE−ENERGIZE 2ND STAGE GAS VALVE INDUCER SPEED SWITCHED TO LOW SPEED...
- Page 61 Troubleshooting CALL FOR COOLING 1ST STAGE COOLING REQUEST RECEIVED WAIT FOR COMPRESSOR TIMED OFF DELAY TO EXPIRE ENERGIZE 1ST STAGE COOLING CONTACTOR (COMPRESSOR & FAN) INDOOR BLOWER 2 SECOND ON DELAY ENERGIZE INDOOR BLOWER (LOW COOLING MODE) MAINTAIN INDOOR BLOWER (LOW COOLING MODE) 1ST STAGE 2ND STAGE...
- Page 62 Troubleshooting CALL FOR FAN CALL FOR FAN INDOOR BLOWER ON CONTINUOUS FAN SPEED CALL FOR FAN MAINTAIN INDOOR BLOWER AT REMOVED? CONTINUOUS FAN REQUEST MAINTAIN INDOOR FOR COOLING GO TO CALL FOR COOLING BLOWER AT RECEIVED? CONTINUOUS FAN REQUEST INDOOR BLOWER OFF FOR HEAT GO TO CALL FOR 1ST STAGE HEAT RECEIVED?
- Page 63 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 64 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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