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Lennox G24M SERIES, Unit Information, Page: 28 / 36

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Page 28

NORMAL HEATING MODE

ABNORMAL HEATING MODE

FLAME RECTIFICATION CURRENT

CHECK. CAN FLAME BE PROVEN WITHIN

4 SECONDS AFTER GAS VALVE OPENS?

(

>

0.15 microamps)

FLAME PRESENT?

INDOOR BLOWER ON DELAY BEGINS

(45 seconds.)

PRIMARY AND SECONDARY LIMIT

SWITCHES CLOSED?

COMBUSTION AIR PRESSURE

SWITCH CLOSED?

LOW FLAME SIGNAL

(Does not affect operation of control)

LED #1 -- SLOW FLASH

LED #2 -- FAST FLASH

GAS VALVE DE-ENERGIZED.
COMBUSTION AIR INDUCER

DE-ENERGIZED.INDOOR BLOWER

ON UNTIL SWITCH CLOSES.LED #1

-- SLOW FLASH. LED #2 -- ON.

IS LIMIT SWITCH CLOSED?

GAS VALVE DE-ENERGIZED.

COMBUSTION AIR INDUCER ON.

INDOOR BLOWER OFF WITH DELAY

LED #1 -- OFF. LED #2 -- SLOW FLASH.

HAS CAB SWITCH CLOSED IN 2.5 MINUTES?

15-SECOND COMBUSTION AIR INDUCER PREPURGE

INITIATED BY CLOSED PRESSURE SWITCH.

YES

IGNITOR WARM-UP -- 20 SECONDS.

YES

4-SECOND TRIAL FOR IGNITION. GAS VALVE OPENS.

IGNITOR ENERGIZED FOR 1 SECOND AFTER VALVE

OPENS. NO FLAME SENSED DURING THIS PERIOD.

BOARD 97L48: IGNITOR ENERGIZED DURING TRIAL OR

UNTIL FLAME SENSED.

YES

FLAME STABILIZATION PERIOD.

GAS VALVE OFF. COMBUSTION AIR INDUCER ON.

INDOOR BLOWER OFF.

HAS CONTROL FAILED TO SENSE FLAME FOR

FIVE CONSECUTIVE TRIES DURING A SINGLE

HEAT DEMAND?

IGNITION WATCHGUARD MODE. GAS VALVE OFF.

COMBUSTION AIR INDUCER OFF.

INDOOR BLOWER OFF WITH DELAY

LED 1 ALT. SLOW FLASH LED 2 ALT SLOW FLASH

IS 60-MINUTE RESET PERIOD COMPLETE?

YES

4 SECONDS

YES

HAS CONTROL RESET IGNITION

SEQUENCE FOUR TIMES?

FLAME SIGNAL ABOVE 0.7 MICROAMPS?

YES

YES

HAS PRIMARY/SECONDARY LIMIT RESET.

(See table 2 DIAGNOSTIC CODES for limit reset operation)

YES

ROLLOUT SWITCH CLOSED?

GAS VALVE POWER OFF.

COMBUSTION AIR INDUCER POWER OFF.

INDOOR BLOWER OFF WITH DELAY

LED #1 -- ON. LED #2 -- SLOW FLASH.

SEQUENCE HOLDS UNTIL ROLLOUT SWITCH IS RESET

YES

THERMOSTAT DEMAND SATISFIED.

LED #1 & #2 SIMULTANEOUS SLOW FLASHES.

YES

NO

5-MINUTE PRESSURE SWITCH

WATCHGUARD MODE.

YES

IS THERE A PROPER GROUND?

IS VOLTAGE ABOVE 75 VOLTS?

IS IGNITOR INTACT AND CONNECTED?

LEDS SIGNAL
ALTERNATING

FAST FLASH

NO

YES

YES

YES

YES

YES

NO

NO

NO

NO

NO

NO

NO

NO

YES

YES

NO

NO

NO

NO

YES

YES

LIMIT SWITCH WATCH GUARD
MODE. GAS VALVE OFF.
COMB. AIR INDUCER OFF. IN-
DOOR BLOWER OFF WITH
DELAY. LED#1-SLOW FLASH
LED#2- ON. IS 60MINUTE RE-
SET PERIOD COMPLETE.?

YES

YES

COMB. AIR INDUCER CONTINUES 5-SECOND POST PURGE

AFTER T’STAT DEMAND IS SATISFIED. INDOOR AIR BLOWER

COMPLETES SELECTED “OFF” DELAY BEFORE SHUTTING OFF.

ACB.HEAT SPEED, HTG ACC TERM. AND ACC TERM. OFF.

Summary of Contents for G24M SERIES

Page 1: ...of local or state codes the guidelines and procedures outlined in this manual except where noted are recommended only and do not constitute code SPECIFICATIONS Model No G24M2 X 45 G24M2 60 G24M3 X 60...

Page 2: ...characteristics 120 volts 60 hertz 1 phase less than 12 amps All models H Optional Accessories Must Be Ordered Extra H LPG propane kit LB 69845L 38K84 LB 69845K 81J14 Twinning Kit 96J69 5 lbs 2 kg Up...

Page 3: ...6 x 20 x 1 Filter Rack No Size of Filters mm 2 406 x 508 x 25 Down flow Combustible Floor Base LB 79239B 67J92 10 lbs 4 kg LB 79239C 67J93 12 lbs 5 kg Sidewall Power Venting Kit 79J15 25 lbs 11 kg Han...

Page 4: ...e Also see Filter Air Resistance table G24M4 75 G24M3 4 100 AND G24M3 4 120 BLOWER PERFORMANCE External Static Air Volume at Various Blower Speeds External Static Pressure High Medium High Medium Medi...

Page 5: ...0 1125 2105 995 1930 910 1675 790 1480 700 30 75 2360 1115 2090 985 1915 905 1670 790 1470 695 40 100 2310 1090 2050 965 1870 880 1650 780 1440 680 50 125 2260 1065 2000 945 1810 855 1610 760 1410 665...

Page 6: ...RY LIMITS FRONT LOUVERED PANEL DOOR INTERLOCK SWITCH CONTROL BOARD TRANSFORMER PRESSURE SWITCH NOx TURBULATOR LOW PRESSURE SWITCH Propane Only PRIMARY LIMIT FIGURE 2 HEATING COMPONENTS shown in horizo...

Page 7: ...PRIMARY LIMIT ROLLOUT SWITCHES SURELIGHT IGNITOR FIGURE 4 To Access Blower 1 Turn off power to unit and disconnect L1 and L2 line voltage power 2 Disconnect thermostat wiring connec tions from furnac...

Page 8: ...Shock hazard Disconnect power before servicing Control is not field repairable If control is inoperable simply replace entire control Can cause injury or death Unsafe operation will result if repair...

Page 9: ...ration signaled when heating demand initiated at thermostat SLOW FLASH ON Primary or Secondary limit open Units with board 63K8901 or 24L85 Limit must close within 5 trials for ignition or board goes...

Page 10: ...20 seconds after which the gas valve opens for a 4 second trial for ignition The ignitor stays en ergized for the first second of the 4 second trial G24M units with 63K89 24L85 or 56L83 the ignitor s...

Page 11: ...e After a demand the combustion air blower continues to operate for 5 seconds post purge before stopping Post purge allows the heat exchanger to be cleared of combustion products Ignition Control The...

Page 12: ...he indoor blower starts after a 45 second delay Gas valve remains open and blower continues to run until demand stops flame sensor senses loss of flame a limit opens or the prove switch opens If any o...

Page 13: ...C Out T o Rollout Switches RO IN J20 P20 Pin 15 24VAC In From Rollout Switches SPARK ELECTRODE Male Spark Plug Type High Voltage Out T o Spark Electrode FS J20 P20 Pin 12 Flame Microamp Sensing FIGURE...

Page 14: ...ly reset a tripped switch push the reset button located on the control FIGURE 12 ROLLOUT SWITCH S47 MANUAL RESET BUTTON E Primary Limit Control S10 FIGURE 13 G24M SERIES UNITS LIMIT CONTROL FOR THIS T...

Page 15: ...ition control 24V applied to the terminals energizes the valve Inlet and outlet pressure taps are located on the valve A regulator adjustment screw is located on the valve Refer to figure 17 or 18 for...

Page 16: ...y and Seasonal Checks 1 Inspect electrical wiring both field and factory installed for loose connections Tighten as required 2 Check voltage at disconnect switch Voltage must be within range listed on...

Page 17: ...ent dam age to gas valve or overfire For natural gas units op erating pressure at unit gas connection must be be tween 5 0 W C and 13 0 W C For L P gas units operating pressure at unit gas connection...

Page 18: ...itudes Refer to table 12 for pressure switch replacement for models at elevations of 4500 feet 1372m and greater TABLE 11 ALTITUDE feet m GAS FUEL MANIFOLD PRESSURE in W C kPa 0 4500 Natural 3 5 0 87...

Page 19: ...unit rating plate To Measure Temperature Rise 1 Place plenum thermometers in the supply and return air plenums Locate supply air thermometer in the first horizontal run of the plenum where it will no...

Page 20: ...SE CURELY IN PLACE E Blower Speed Taps Leaded Motors Blower speed tap changes are made on the SureLight control board See figure 6 Unused taps must be secured on dummy terminals PARK M1 and or PARK M...

Page 21: ...tial for gas leaks fire or explosion Some soaps used for leak detection are corrosive to certain metals Carefully clean piping thor oughly after leak detection has been completed Can cause damage to p...

Page 22: ...92 7 7 3 0 5 1 5 0 1 851 6 167 5 75 16 250 5 225 17 5 2 6 7 20 867 21 5 2 5 35 6685 6 7 1 7 5 35 0 5 0 7 0 52 287 6 7 6 85 COMPRESSOR COMMON POWER HEAT INDOOR BLOWER COMMON HS UNIT COMMON HS UNIT COMP...

Page 23: ...lower nears full speed combustion air prove switch S18 closes 5 When S18 closes assuming the flame rollout switch S47 primary limit S10 and secondary limits S21 are closed the furnace control begins a...

Page 24: ...N RESET THERMOSTAT LED 5 flash if flame sensed with valve off LED Steady on if control board failure NO NO CHECK TO SEE IF MAIN VALVE IS OFF SEQUENCE HOLDS UNTIL HI LIMIT CLOSES LED 4 flashes NO CHECK...

Page 25: ...e REMAINS UNCHANGED THROUGHOUT SEQUENCE THERMOSTAT CALLS FOR COOLING SYSTEM FAN SWITCHES TO HEATING SPEED AFTER SELECTED DELAY ACC TERM REMAINS ENERGIZED SYSTEM FAN SWITCHED TO COOLING SPEED ACC TERMI...

Page 26: ...Pressure Switch delay Once S18 closes a 15 second pre purge follows 4 SureLight control energizes ignitor A 20 second warm up period begins 5 Gas valve opens for a 4 second trial for ignition Ignitor...

Page 27: ...G SPEED LED 1 SLOW FLASH LED 2 OFF GAS VALVE OFF COMBUSTION AIR BLOWER OFF INDOOR BLOWER OFF WITH DELAY LED 1 OFF LED 2 SLOW FLASH Sequence holds until pressure switch closes or thermostat resets cont...

Page 28: ...TO SENSE FLAME FOR FIVE CONSECUTIVE TRIES DURING A SINGLE HEAT DEMAND IGNITION WATCHGUARD MODE GAS VALVE OFF COMBUSTION AIR INDUCER OFF INDOOR BLOWER OFF WITH DELAY LED 1 ALT SLOW FLASH LED 2 ALT SLO...

Page 29: ...CHANGED THROUGHOUT COOLING CYCLE THERMOSTAT CALLS FOR COOLING COMPRESSOR CONTACTOR AND SYSTEM FAN ENERGIZED WITH 0 SECOND DELAY ACB COOL SPEED AND ACC TERM ENERGIZED COMPRESSOR OFF THERMOSTAT OPENS AC...

Page 30: ...Y THERMOSTAT OPENS COMBUSTION AIR AND HTG ACC TERMINAL DE ENERGIZE SYSTEM FAN SWITCHED TO ACB COOL SPEED ACC TERM REMAINS ON THERMOSTAT OPENS BOARD 63K89 SYSTEM FAN OFF ACC TERM OFF AFTER OFF DELAY CO...

Page 31: ...ch open ACTION 1 Manually reset the roll out switch by pushing the top button ACTION 2 Determine the cause of the roll out switch activation before leaving furnace out code LED 1 O 1 2 2 Roll out swit...

Page 32: ...ternating Fast Flash 2 1 2 Broken or failed ignitor ACTION 1 Unplug ignitor and read resis tance across ignitor If resistance does not read between 10 9 and 19 7 ohms replace the ignitor PROBLEM 3 UNI...

Page 33: ...with a heating demand Diagnostic lights flash the pres sure switch failure code 2 5 min utes after heating demand 4 1 2 Pressure switch does not close due to obstructions in the pressure lines ACTION...

Page 34: ...atisfying T stat demand Diagnostic lights flash the pres sure switch code LED 1 Off LED 2 Slow Flash 6 1 1 Low pressure differential at the pressure switch ACTION 1 Check for restricted vent inlet or...

Page 35: ...rsootingdepositsoroth er restrictions in the heat exchanger assem bly Cleanassemblyasoutlinedininstruction manual ACTION 2 ForG24Mgasfurnaces checkfor proper combustion and flow CO2 should measurebetw...

Page 36: ...ated ACTION 1 Check sense rod for contamina tion or coated surface Clean the sense rod with steel wool or replace sensor DO NOT USE SAND PAPER TO CLEAN ROD SAND PAPER WILL CONTRIBUTE TO THE CON TAMINA...

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