Lennox SL280DFV Series Unit Information
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Lennox SL280DFV Series Unit Information

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S e r v i c e L i t e r a t u r e
COMMUNICATING ENABLED SL280DFV SERIES UNITS
SL280DFV series units are 80% efficiency gas furnaces
used for downflow applications only, manufactured with
Lennox Duralok heat exchangers formed of aluminized
steel. Units are available in heating capacities of 66,000 to
110,000 Btuh and cooling applications up to 5 tons. Refer
to Engineering Handbook for proper sizing.
Units are factory equipped for use with natural gas. Kits
are available for conversion to LPG operation. SL280DFV
model units are equipped with a communicating enabled
SureLight
two-stage variable speed integrated control.
®
All units use a redundant gas valve to assure safety shut-
off as required by CSA.
All specifications in this manual are subject to change.
Procedures outlined in this manual are presented as a
recommendation only and do not supersede or replace lo-
cal or state codes. In the absence of local or state codes,
the guidelines and procedures outlined in this manual (ex-
cept where noted) are recommendations only and do not
constitute code.
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.

TABLE OF CONTENTS

Specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Page 2
Parts Identification . . . . . . . . . . . . . . . . . . . . . . . . . Page 7
I Unit Components . . . . . . . . . . . . . . . . . . . . . . . . Page 8
II Installation . . . . . . . . . . . . . . . . . . . . . . . . . . . . Page 36
III Start Up . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Page 36
VI Maintenance . . . . . . . . . . . . . . . . . . . . . . . . . . Page 41
VIII Program Unit Capacity Size Mode
IX Field Wiring and Jumper Settings
X Troubleshooting Flow Chart . . . . . . . . . . . . . . Page 62
UNIT INFORMATION
UNIT INFORMATION
Corp 1117-L4
Revised 03/2022
. . . . . . . . . Page 38
. . . . . . . . . Page 41
. . . . . . Page 44
. . . . . . Page 61
. . . . . . . . Page 47
Page 1
WARNING
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.
WARNING
Shock hazard. Disconnect power before
servicing. Integrated control is not field
repairable. If control is inoperable, simply
replace entire control. Can cause injury
or death. Unsafe operation will resul if
repair is attempted.
SL280DFV
adjustment,
alteration,
©2016 Lennox Industries, Inc.

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  • Page 1: Table Of Contents

    S e r v i c e L i t e r a t u r e Revised 03/2022 COMMUNICATING ENABLED SL280DFV SERIES UNITS SL280DFV series units are 80% efficiency gas furnaces used for downflow applications only, manufactured with Lennox Duralok heat exchangers formed of aluminized steel.

  • Page 2: Specifications

    SP ECIF ICATIONS Model No. SL280DF070V36A SL280DF090V48B SL280DF090V60C SL280DF110V60C Heating AFUE Performance High Input - Btuh 66,000 88,000 88,000 110,000 Fire Output - Btuh 52,000 69,000 70,000 87,000 Temperature rise range - °F 35-65 35-65 35-65 35-65 Gas Manifold Pressure (in. w.g.) 3.5 / 10.0 3.5 / 10.0 3.5 / 10.0...
  • Page 3 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 iHarmony Zoning System Applications - Minimum blower speed is 250 cfm.
  • Page 4 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 380 cfm. Lennox iHarmony Zoning System Applications - Minimum blower speed is 380 cfm.
  • Page 5 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 iHarmony Zoning System Applications - Minimum blower speed is 450 cfm.
  • Page 6 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 iHarmony Zoning System Applications - Minimum blower speed is 450 cfm.

  • Page 7: Parts Identification

    PARTS IDENTIFICATION BLOWER ASSEMBLY SECONDARY LIMIT GASKET FLUE CHASE CONTROL BOX (Includes two-stage integrated control, transformer and circuit breaker) INTERNAL FLUE PIPE ASSEMBLY DOOR INTERLOCK SWITCH PRIMARY LIMIT LOCATION ROLLOUT SWITCH HEAT EXCHANGER COMBUSTION AIR INDUCER PRESSURE SWITCHES COMBUSTION AIR INDUCER GAS VALVE INNER BLOWER ACCESS PANEL BURNER BOX ASSEMBLY...

  • Page 8: I Unit Components

    I-UNIT COMPONENTS CIRCUIT BREAKER CB8 Unit components are shown in FIGURE 1. The gas valve, combustion air inducer and burners can be accessed by removing the access panel. Electrical components are in PRESS TO RESET the control box (FIGURE 2) found in the blower section. ELECTROSTATIC DISCHARGE (ESD) FIGURE 3 Precautions and Procedures...
  • Page 9 Once the first stage prove switch is determined to be open, TABLE 1 the combustion air inducer is energized on low (first stage) SureLight Control 5 Pin Terminal Designation ® heat speed. When the differential in the prove switch is PIN# Function great enough, the prove switch closes and a 15-second...
  • Page 10 IGNITION CONTROL 103130-XX HS/ CAI LINE 1 NEUTRAL 7 SEGMENT LED FLAME SENSE INDOOR BLOWER DIAGNOSTIC CONNECTOR PUSH BUTTON DIP SWITCHES 12 PIN LOW OUTDOOR AIR VOLTAGE SENSOR CONNECTOR TERMINALS DISCHARGE AIR W915 Y1 TO Y2 SENSOR 2 STAGE COMPR TERMINALS W951 R TO O HEAT PUMP...
  • Page 11 IGNITION CONTROL 107045-XX RS-BUS LINK (TB82, future use) THERMOSTAT CONNECTIONS (TB1) DS = DEHUMIDIFICATION SIGNAL I+ = DATA HIGH CONNECTION I - = DATA LOW CONNECTION W2 = HEAT DEMAND FROM 2ND STAGE T/STAT W1 = HEAT DEMAND FROM 1ST STAGE T/STAT R = 24VAC I + = DATA HIGH CONNECTION R = CLASS 2 VOLTAGE TO THERMOSTAT...
  • Page 12 INTEGRATED CONTROL CONFIGURATION GUIDE CLG BLOWER SPEED ADJUSTMENT 2ND STAGE HEAT ON DELAY DEFAULT 7 MIN CONTINUOUS FAN MODE BLOWER SPEED UPSTAGE THERMOSTAT SELECTION DELAY + 10% MEDIUM−LOW SPEED TWO STAGE (38%) THERMOSTAT 12 MIN − 10% UPSTAGE MEDIUM−HIGH DELAY SPEED 1−STAGE (70%)
  • Page 13 Ignition Control 103130-XX Diagnostic Modes Display Action (when button is released) No change (idle)* Remain in idle mode Solid “E” Enter diagnostic recall mode Solid “D” Discharge Air Installed Solid “F” Enter flame signal mode Solid “F” (variable speed only) Program unit capacity size (Unit Code) Two horizontal lines soft disable...
  • Page 14 TABLE 4 Ignition Control 103130-XX Diagnostic Codes Code Diagnostic Codes/Status of Equipment Action Required to Clear and Recover Idle mode (Decimal blinks at 1 Hertz -- 0.5 second ON, 0.5 second OFF). Cubic feet per minute (cfm) setting for indoor blower (1 second ON, 0.5 second OFF) / cfm setting for current mode displayed.
  • Page 15 Ignition Control 103130-XX Diagnostic Codes Continued Code Diagnostic Codes/Status of Equipment Action Required to Clear and Recover E124 Active communicating thermostat signal Equipment lost communication with the thermostat. Check missing for more than 3 minutes. four wiring connections, ohm wires and cycle power at the thermostat.
  • Page 16 Ignition Control 103130-XX Diagnostic Codes Continued Code Diagnostic Codes/Status of Equipment Action Required to Clear and Recover E206 Gas valve second-stage relay failure Furnace will operate on 1st stage for remainder of the heating demand. Will clear after fault recovered. If un- able to operate 2nd stage, replace control.
  • Page 17 Ignition Control 103130-XX Diagnostic Codes Continued Code Diagnostic Codes/Status of Equipment Action Required to Clear and Recover E271 Soft lockout - Exceeded maximum number of re- Check pressure (inches w.c.) of low pressure switch clos- tries. Last retry failed due to the pressure switch ing on heat call.
  • Page 18 Ignition Control 103130-XX Diagnostic Codes Continued Code Diagnostic Codes/Status of Equipment Action Required to Clear and Recover E312 Restricted air flow in cooling or continu- Warning Only. Restricted airflow - Indoor blower is running at a re- ous fan mode is lower than cfm setting. duced CFM (Cutback Mode - The variable speed motor has pre-set speed and torque limiters to protect the motor from damage caused by operating outside of design parameters (0 to 0.8”...
  • Page 19 Ignition Control 103130-XX Diagnostic Codes Continued Code Diagnostic Codes/Status of Equipment Action Required to Clear and Recover E406 LSOM - Compressor open start circuit. Required amount of current is not passing through Start cur- rent transformer. Clears the error after current is sensed in START sensor, or after power reset.
  • Page 20 TABLE 5 Ignition Control 107045-XX Diagnostic Codes Code Diagnostic Codes/Status of Equipment Action Required to Clear and Recover Idle mode (Decimal blinks at 1 Hertz -- 0.5 second ON, 0.5 second OFF). Cubic feet per minute (cfm) setting for indoor blower (1 second ON, 0.5 second OFF) / cfm setting for current mode displayed.
  • Page 21 Ignition Control 107045-XX Diagnostic Codes Continued Code Diagnostic Codes/Status of Equipment Action Required to Clear and Recover E124 Active communicating thermostat signal Equipment lost communication with the thermostat. Check missing for more than 3 minutes. four wiring connections, ohm wires and cycle power at the thermostat.
  • Page 22 Ignition Control 107045-XX Diagnostic Codes Continued Code Diagnostic Codes/Status of Equipment Action Required to Clear and Recover E206 Gas valve second-stage relay failure Furnace will operate on 1st stage for remainder of the heating demand. Will clear after fault recovered. If un- able to operate 2nd stage, replace control.
  • Page 23 Ignition Control 107045-XX Diagnostic Codes Continued Code Diagnostic Codes/Status of Equipment Action Required to Clear and Recover E271 Soft lockout - Exceeded maximum number of re- Check pressure (inches w.c.) of low pressure switch clos- tries. Last retry failed due to the pressure switch ing on heat call.
  • Page 24 Ignition Control 107045-XX Diagnostic Codes Continued Code Diagnostic Codes/Status of Equipment Action Required to Clear and Recover E312 Restricted air flow in cooling or continu- Warning Only. Restricted airflow - Indoor blower is running at a re- ous fan mode is lower than cfm setting. duced CFM (Cutback Mode - The variable speed motor has pre-set speed and torque limiters to protect the motor from damage caused by operating outside of design parameters (0 to 0.8”...
  • Page 25 DIP Switch Settings Indoor Blower Operation DIP Switch Settings Switches 5 and 6 -- Cooling Mode Blower Speed -- NOTE - All communicating settings are set at the commu- The unit is shipped from the factory with the dip switch- nicating thermostat.
  • Page 26 Ramping Option A (Factory Selection) Switches 11, 12 and 13 -- Heating Mode Blower Speed The switches are factory set to the OFF position which • Motor runs at 50% for 30 seconds. provides factory default heat speed. Refer to TABLE 10 for •...
  • Page 27 On-Board Link W951 Heat Pump (R to O) On-Board Link W915 2 Stage Compr (Y1 to Y2) On-board link W951 is a clippable connection between On-board link W915 is a clippable connection between terminals R and O on the integrated control. W951 must terminals Y1 and Y2 on the integrated control.
  • Page 28 TABLE 13 OPERATING SEQUENCE SL280DFV, 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...
  • Page 29 Initial Power Up IMPORTANT When line voltage is applied to B3, there will be a large Earlier ECM motors used on other Lennox furnace inrush of power lasting less than 1/4 second. This inrush models are not interchangeable with motors used charges a bank of DC filter capacitors inside the controller.
  • Page 30 Motor Start-Up Troubleshooting Motor Operation When B3 begins start-up, the motor gently vibrates back To verify motor operation see steps below: and forth for a moment. This is normal. During this time 1 - Remove J48 (5 pin power plug) from P48 on the the electronic controller is determining the exact position motor.
  • Page 31 BLOWER B3 HARNESS CONNECTORS BLOWER B3 HARNESS CONNECTORS P48 5 Pin P49 4 Pin P48 5 Pin SHAFT SHAFT MOTOR with INTEGRATED CONTROLLER P49 4 Pin MOTOR with INTEGRATED CONTROLLER P48 5 Pin J48 5 Pin P49 4 Pin J49 4 Pin J49 4 Pin Control Connector J48 Connector 120v...
  • Page 32 Troubleshooting Motor Windings TEST A Measure the resistance between each of the three motor Ensure that motor windings are not damaged by perform- leads (3-pin plug) and the unpainted part of the end shield. ing the following tests: If the winding resistance to ground is <100k ohms, NOTE - If your ohm meter is not an auto-ranging type, set replace the motor and control module.
  • Page 33 The limit automatically resets LPG change over kits are available from Lennox. Kits in- when unit temperature returns to normal. The switch must clude burner orifices and a gas valve.
  • Page 34 HEATING COMPONENTS Rollout Switch (alternate location) Ignitor Burners Rollout Switch Sensor Gas Valve and Manifold Assembly Sight Glass FIGURE 14 Page 34...
  • Page 35 Ignitor Check Out Multi−Meter (set to ohms) Test 1 Test 1 Integrated Control Board Detail Remove 5-pin plug from control Check ohms reading across terminals 1and 5 Ohm value should be between 39 - 70. Multi−Meter (set to ohms) Test 2 Seperate the 2-pin jack plug near the manifold and check resistance of the ignitor.

  • Page 36: Installation

    If switch is closed NOTE - Each furnace model uses a unique CAI. Refer to or by-passed, the control will not initiate ignition at start up. Lennox Repair Parts listing for correct inducer for replace- ment. COMBUSTION AIR PRESSURE SWITCH A pressure switch connected to the combustion air induc- er orifice plate is used to prove inducer operation.
  • Page 37 B-Heating Start-Up 9 - Turn switch on gas valve to ON. Do not force. See FIGURE 17 or FIGURE 18. WARNING 10 - Replace the upper access panel. 11 - Turn on all electrical power to to the unit. Shock and burn hazard. SL280DFV units are equipped with a hot surface 12 - Set the thermostat to desired setting.

  • Page 38: Heating System Service Checks

    Use of a specialty Gas Leak Detector is strongly recommended. It All units are CSA design certified without modifications. is available through Lennox under part number 31B2001. Refer to the SL280DFV Installation Instruction. See Corp. 8411-L10, for further details.
  • Page 39 F- Proper Gas Flow (Approximate) G- Proper Combustion Furnace should operate at least 5 minutes before check- Furnace should operate minimum 15 minutes with correct ing gas flow. Determine time in seconds for two revolu- manifold pressure and gas flow rate before checking com- tions of gas through the meter.
  • Page 40 TABLE 20 Manifold Pressure Settings Manifold Manifold Manifold Pressure Supply Line Pressure in. wg. Pressure in. wg. in. wg. 7500 - Pressure Unit Orifice Size Orifice Size 0 - 4500 ft 4500 - 7500 ft 10,000 ft in. w.g. Input 0 - 7500 ft.

  • Page 41: Typical Operating Characteristics

    V-TYPICAL OPERATING CHARACTERISTICS EXTERNAL STATIC PRESSURE Supply Duct Static Return Duct Static + A-Blower Operation and Adjustment Total Duct Static = (dry coil) When the thermostat is set to “FAN ON,” the indoor blow- er will run continuously at approximately 38% of the sec- Return ond-stage cooling speed when there is no cooling or heat- ing demand.
  • Page 42 AHRI heat exchanger At the beginning of each heating season, and to comply inspection procedure. This procedure can be with the Lennox Limited Warranty, your system should viewed at www.ahrinet.org. be checked by a licensed professional technician (or...
  • Page 43 A-Heat Exchanger and Burners 5 - Remove the collector box located behind the combustion air inducer. Be careful with the collector Cleaning the Heat Exchanger and Burners box gasket. If the gasket is damaged, it must be replaced to prevent leakage. NOTE - Use papers or protective covering in front of the furnace during cleaning.

  • Page 44: Wiring And Sequence Of Operation

    10 - Back wash using steam. Begin from the burner 22 - If a leak is detected, shut gas and electricity off and opening on each clam. Steam must not exceed repair leak. 275°F. 23 - Repeat steps 21 and 23 until no leaks are detected. 11 - To clean burners, run a vacuum cleaner with a soft 24 - Replace access panel brush attachment over the face of burners.
  • Page 45 VII- Wiring and Sequence of Operation Wiring Diagram With Ignition Control 103130-XX SL280DFV Schematic Wiring Diagram Page 45...
  • Page 46 Wiring Diagram With Ignition Control 107045-XX Page 46...
  • Page 47 Applications Using a Two-Stage Thermostat 9 - When the combustion air post-purge period is complete, the inducer, the HUM contacts as well A - Heating Sequence -- Integrated Control Thermo- as the 120V ACC terminals are de-energized. The stat Selection DIP Switch 1 OFF in “Two-Stage” Posi- indoor blower is de-energized at the end of the off tion (Factory Setting) delay.
  • Page 48 VIII- Field Wiring With Conventional and Communicating Enabled Thermostat With Ignition Ignition Control 103130-XX 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...
  • Page 49 Ignition Control 103130-XX 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 50 LENNOX COMMUNICATING OUTDOOR UNIT INDOOR UNIT (1 OR 2 STAGE) FLOAT SWITCH LENNOX COMMUNICATING OUTDOOR UNIT LENNOX COMMUNICATING FURNACE EL296V, SL280V, SL280VN, SL297V, SLP99V cutting DS to R will not cause communication interuption or error code CUT* R-DS W914 Page 50...
  • Page 51 Ignition Control 103130-XX DIP Switch Settings and On-Board Links With a 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...
  • Page 52 Ignition Control 103130-XX DIP Switch Settings and On-Board Links With a 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 2 Heat / 2 Cool FURNACE OUTDOOR T'STAT...
  • Page 53 Ignition Control 103130-XX DIP Switch Settings and On-Board Links With a Conventional Thermostat 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...
  • Page 54 Ignition Control 103130-XX DIP Switch Settings and On-Board Links With a Conventional Thermostat 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...
  • Page 55 Ignition Control 107045-XX 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...
  • Page 56 Ignition Control 107045-XX Optional Accessories for use with Communicating System NOTE: COMMUNICATING THERMOSTAT SENSES HUMIDITY 120V CONNECTIONS & CONTROLS HUM CONTACTS TO CYCLE HUMIDIFIER BASED ON DEMAND. NO OTHER CONTROL OR HUMIDISTAT REQUIRED. “HUM” CONTACT IS CLOSED ANYTIME OPTIONAL OUTDOOR AIR SENSOR FOR USE WITH HUMIDI− HUMIDITY DEMAND FIER (IF NOT ALREADY IN THE SYSTEM FOR OTHER FUNC−...
  • Page 57 LENNOX COMMUNICATING OUTDOOR UNIT INDOOR UNIT (1 OR 2 STAGE) FLOAT SWITCH LENNOX COMMUNICATING OUTDOOR UNIT LENNOX COMMUNICATING FURNACE EL296V, SL280V, SL280VN, SL297V, SLP99V cutting DS to R will not cause communication interuption or error code CUT* R−DS W914 FIGURE 2...
  • Page 58 Ignition Control 107045-XX DIP Switch Settings and On-Board Links With a 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...
  • Page 59 Ignition Control 107045-XX DIP Switch Settings and On-Board Links With a 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 2 Heat / 2 Cool FURNACE OUTDOOR T'STAT...
  • Page 60 Ignition Control 107045-XX DIP Switch Settings and On-Board Links With a Conventional Thermostat 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 L7742U...
  • Page 61 Ignition Control 107045-XX DIP Switch Settings and On-Board Links With a Conventional Thermostat 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 L7742U...
  • Page 62 IX- 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 63 X- 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 INDOOR SWITCH WATCHGUARD − AFTER HEAT FAN LIMIT SWITCH CODE BLOWER CLOSED WITHIN 3 ERROR CODE...
  • Page 64 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 65 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 INDOOR BLOWER SWITCHED...
  • Page 66 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 COOLING REQUEST...
  • Page 67 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?

This manual is also suitable for:

Sl280df070v36aSl280df090v48bSl280df090v60cSl280df110v60c

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