Lennox G21Q Series Unit Information

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NO YES
NO YES
REFER TO INSTALLATION INSTRUCTIONS: ARE IN
TAKE & EXHAUST LINES PROPERLY SIZED & AP
PLIED WITHIN LENGTH, DIAMETER & ELBOW LIMITS?
YES NO
NO YES
YES NO
NO YES
IS GAS SUPPLY NATURAL OR L.P.?
L.P. NATURAL
HAS L.P. CONVERSION KIT
BEEN INSTALLED?
IF NOT, INSTALL KIT.
IS GAS SUPPLY ON?
1. CHECK SUPPLY VALVE.
2. CHECK STOP VALVE AT UNIT.
3. CHECK MANUAL KNOB ON
GAS VALVE IN UNIT.
CHECK FOR LEAKS IN GAS SUPPLY
PIPING & REPAIR IF NEEDED.
AIR IN GAS PIPING?
BLEED AIR BY RUNNING UNIT THROUGH SEVERAL
TRIES FOR IGNITION. BREAK & REMAKE THERMOSTAT
DEMAND TO RESTART IGNITION SEQUENCE AT 2 TO 3
MINUTE INTERVALS.
CAUTIONDO NOT USE MATCH OR FLAME
TO CHECK FOR GAS LEAKS.
GAS
CHECKS
CHECK FOR LEAKS IN UNIT MANIFOLD PIPING.
LEAKS NO LEAKS
VISUALLY CHECK OUTSIDE TERMINATIONS OF
INTAKE & EXHAUST PVC PIPING FOR OBSTRUCTIONS.
VISUALLY CHECK CONDENSATE DRAIN FOR OBSTRUCTIONS.
CORRECT PIPING
ERRORS & RETEST.
TURN OFF GAS TO UNIT.
CHECK PURGE BLOWER FOR BINDING
OR MECHANICAL DAMAGE.
BREAK & REMAKE THERMOSTAT DEMAND
TO INITIATE CONTROL SEQUENCE.
IS120VAC PRESENT ACROSS PURGE
BLOWER MOTOR TERMINALS?
NO YES
IS 120VAC PRESENT BETWEEN
JP72−6 AND COMMON?
DOES PURGE BLOWER RUN?
REPLACE
PURGE BLOWER.
REPLACE
PRIMARY CONTROL.
CHECKOUT
WIRING
CONNECTIONS
& REPAIR.
IS DIFFERENTIAL PRESSURE SWITCH CUTTING OUT?
IF NO BLOCKAGE EXISTS
REPLACE DIFFERENTIAL PRESSURE
SWITCH.
3. REPLACE SENSOR IF
CRACKED?
2. ARE CRACKS PRESENT IN PORCELAIN?
1. WAS PLUG TIGHT WHEN REMOVED?
IS GAS VALVE ACTUALLY OPENING?
DETERMINE BY CHECKING FOR MANIFOLD
PRESSURE DURING TRIALS FOR IGNITION.
REPLACE GAS VALVE.
CORRECT
GAS PRES
SURE.
AIR
CHECKS
REMOVE AIR INTAKE CHAMBER COVER
(USE CARE TO PREVENT DAMAGE TO COVER GASKET).
8
9
REPAIR LEAKS
& RETEST.
UNIT SPUTTER STARTS AND DIES
MAKE OHM METER CHECK ACROSS
TERMINALS IMMEDIATELY AFTER
UNIT SHUTS OFF. METER READS
INFINITE( )OHMS WHEN SWITCH
CUTS UNIT OUT.
8
CHECK FOR PARTIAL BLOCKAGE
OF ALL PVC PIPING & CONDENSATE
LINE.
IS FLAME SIGNAL PRESENT AND COR
RECT?
CHECK WITH MICROAMP METER
NO YES
CHECK SENSOR WIRE
REPLACE IF DETERI
ORATED
& RETEST UNIT
IS AIR FLAPPER VALVE OPERATING NORMALLY?
(LACK OF AIR?) REFER TO
CHECKING AIR INTAKE FLAPPER VALVE"
REPLACE ORIFICE
IF
NECESSARY
IS GAS ORIFICE CORRECT?
REFER TO CHECKING GAS ORIFICE"
NOYES
IS GAS FLAPPER OPERATING NORMALLY?
REFER TO CHECKING GAS FLAPPER VALVE
YES
REPLACE GAS FLAPPER VALVE
NO
REPLACE AIR FLAPPER VALVE OR MATERIAL
IS 120VAC PRESENT
BETWEEN
JP72−6 AND JP72−5?
YES NO
REMOVE & CHECK SPARK PLUG (USE LENNOX
PART #20H43 OR 3/4" SPARK PLUG SOCKET).
START HERE

Lennox G21Q Series Specifications

General

Brand	Lennox
Model	G21Q Series
Category	Industrial Equipment
Language	English