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Service Literature
G21 and GSR21 units are condensing furnaces utilizing
the pulse combustion process. Initially, combustion
takes place in an enclosed chamber. Then, as combus
tion products pass through the heat exchanger system
into a coil, the latent heat of combustion is extracted and
water is condensed from the exhaust gas.
The unit uses a redundant gas valve to assure safety
shut off as required by A.G.A. The units are manufac
tured for natural gas application. L.P. kits for A.G.A. /
C.G.A. units are available for field changeover.
An electronic direct spark ignition control initiates com
bustion. The ignition control serves four functions: pre
purge, ignition, flame sensing and post purge. Controls
reset in the event of nuisance lockout. The control also
verifies loss of combustion during a cycle, closing the
gas valve. A differential pressure switch shuts down the
unit immediately if there are obstructions in the exhaust
outlet or air intake.
A purge blower clears the combustion chamber before and af
ter each heating cycle to ensure proper air mixture for start up.
All units feature direct drive multi speed blower motors.
V" series units feature an electronically controlled blower
motor (ICM1 or ICM2) controlled by a VSP control (VSP1 or
VSP2−1). The VSP controls blower CFM using either a
BACK PRESSURE IGNITION
COMBUSTION
4
OPEN CLOSED
1
G21/GSR21 SERIES UNITS
PULSE COMBUSTION PROCESS
EXHAUST
4
5
COMBUSTION
CHAMBER
3
AIR
3
GAS
PWM (pulse width modulation) signal or fixed 24 VAC or
VDC signal.
These signals are gener
ated by optional controls
such as the Harmony zone
control system, Efficiency
Plus
Humidity
(CCB1) or a thermostat. A
PWM signal is generated by
the Harmony zone control
system. A fixed DC signal is
generated by the Efficiency
Plus
Humidity
(CCB1) and a 24 VAC signal
is generated by a thermo
stat.
The Harmony zone control system produces a PWM signal
to regulate blower CFM. The CCB1 varies indoor blower
speed in response to indoor humidity demand. The CCB1
produces a DC signal.
When a two speed condensing unit is used with the Harmony
zone control system or CCB1, compressor speed as well as
indoor blower CFM are controlled more accurately than with
a conventional two stage thermostat.
All specifications in this manual are subject to change.
7
1 − Gas and air enter and mix in combustion
chamber
2 − To start the cycle a spark is used to ignite the
gas and air mixture (this is one "pulse").
3 − Positive pressure from combustion closes
flapper valves and forces exhaust gases down
the tailpipe.
4 − Exhaust gases leaving chamber create a
negative pressure. This opens the flapper valve
drawing in gas and air.
5 − At the same instant, part of the pulse is
reflected back from the tailpipe causing the
new gas and air mixture to ignite. No spark is
needed. (this is anotherpulse").
6 − Steps 4 and 5 repeat 60 to 70 times per second
forming consecutive pulses" of 1/4 to 1/2
2
Btuh each.
7 − Latent heat is removed from combustion
SENSOR
products and condensate (water) is formed in
SPARK
the condensate coil.
Page 1
G21/GSR21
Corp. 9815−L9
Revised 10−2001
ELECTRONICALLY CONTROLLED
MOTOR
Control
ICM1
Control
ICM2
1998 Lennox Industries Inc.
Litho U.S.A.
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Summary of Contents for Lennox G21Q3-40
- Page 1 pulses" of 1/4 to 1/2 Btuh each. 7 − Latent heat is removed from combustion SENSOR products and condensate (water) is formed in OPEN CLOSED SPARK the condensate coil. 1998 Lennox Industries Inc. Page 1 Litho U.S.A.
- Page 2 TABLE OF CONTENTS General Page 1 Electrical Checkout Page 59 Parts Arrangement Page 3 Gas, Air, Spark Check Page 60 Specifications Page 4−6 Electrical Testing Page 61 Blower Data Page 6−10 ICM2−VSP2 Page 62 Component Illustration Page 11 ICM1−VSP1 Page 63−65 I Application Page 12 Additional Charts...
- Page 3 PARTS ARRANGEMENT (G21 UPFLOW UNIT) HEAT EXCHANGER LIMIT ASSEMBLY CONTROL DIFFERENTIAL PRESSURE GAS VALVE SWITCH IGNITION CONTROL EXPANSION ICM1 BLOWER TANK MOTOR GAS FLAPPER VALVE & ORIFICE ASSEMBLY AIR INTAKE CONNECTION AIR VALVE AND AIR HOUSING LOW VOLTAGE TERMINAL STRIP CONTROL G21Q SERIES BLOWER MOTOR...
- Page 4 SPECIFICATIONS (units equipped with conventional multi speed blower motor) Model No. G21Q3 40 G21Q3 60 G21Q4 60 Input Btuh 40,000 60,000 60,000 Output Btuh 38,000 55,000 55,000 *A.F.U.E. 96.2% 94.1% 94.1% California Seasonal Efficiency 90.7% 89.9% 88.8% Temperature rise range (°F) High static certified by A.G.A.
- Page 5 SPECIFICATIONS (contd.) SPECIFICATIONS (units equipped with conventional multi speed blower motor) GSR21Q4 5 GSR21Q3 8 Model No. GSR21Q3 50 GSR21Q4/5 80 GSR21Q4/5 100 Input Btuh 50,000 50,000 80,000 80,000 100,000 Output Btuh 47,000 47,000 71,000 72,000 92,000 *A.F.U.E. 94.8% 95.3% 91.7% 94.1% 92.0%...
- Page 6 SPECIFICATIONS (contd.) SPECIFICATIONS (units equipped with electronically controlled blower motor) Model No. GSR21V3 80 GSR21V5 80 GSR21V5 100 Input Btuh 80,000 80,000 100,000 Output Btuh 71,000 72,000 92,000 *A.F.U.E. 94.5% 94.6% 92.0% California Seasonal Efficiency 92.5% 92.1% 89.7% Temperature rise range (°F) High static certified by A.G.A.
- Page 7 BLOWER DATA (contd.) (units equipped with conventional multi speed blower motor) G21Q4 60 AND G21Q4 80 G21Q3 100 BLOWER PERFORMANCE BLOWER PERFORMANCE External Static Air Volume @ Various Speeds External Static Air Volume @ Various Speeds Pressure High Medium (in. wg) Pressure High Medium...
- Page 8 BLOWER DATA (contd.) (units equipped with conventional multi speed blower motor) GSR21Q4 50 BLOWER PERFORMANCE GSR21Q4/5 80 BLOWER PERFORMANCE External Static Air Volume (cfm) @ Various Speeds External Static Air Volume (cfm) @ Various Speeds Pressure Pressure High Med High Med Low High Med High...
- Page 9 (units equipped with an electronically controlled blower motor ICM2) BLOWER DATA (contd.) G21V5−80/100 BLOWER MOTOR PERFORMANCE (For Static Pressure 0.0" to 0.8" w.g.) LOW SPEED HIGH (COOL) SPEED HEAT SPEED ADJUST ADJUST JUMPER VSP2−1 JUMPER POSITION VSP2−1 JUMPER POSITION VSP2−1 JUMPER POSITION SETTING SETTING 1050...
- Page 10 Units Equipped With an Electronically Controlled Blower Motor ICM1 G21V3 60, G21V3 80 BLOWER PERFORMANCE FACTORY BLOWER SPEED SETTINGS G21V3 60 G21V3 80 Low Speed Heat/Cool tap 2 Low Speed Heat/Cool tap 2 High Speed Cooling tap 11 High Speed Cooling tap 11 High Speed Heat tap 6...
- Page 11 UNIT COMPONENTS UPFLOW Q" UNITS LIMIT CONTROL AIR INTAKE PVC CONNECTION DIFFERENTIAL PRESSURE SWITCH GAS VALVE PURGE BLOWER IGNITION CONTROL EXPANSION TANK AIR FLAPPER VALVE GAS FLAPPER VALVE INSULATION & ORIFICE ASSEMBLY HEATING COMPARTMENT SPARK PLUG & SENSOR ACCESS PANEL CONTROL BOX TERMINAL STRIP DOOR INTERLOCK SAFETY SWITCH...
- Page 12 I − APPLICATION G21Q CONTROL BOX G21/GSR21 unit input range covers 40,000 through 100,000 Btuh. See specifications table. G21/GSR21 models use the same cabinet size as the ex isting G14/GSR14 furnace line. All units in the G21/GSR21 series use direct drive blowers and accept cooling coils in nominal tonnages up to 5 tons for the 80, 100.
- Page 13 3 − Low Voltage Terminal Strip TB1 DS" This is the speed regulation input that switches the blower from LOW to HIGH speed, in cooling A low voltage terminal strip (TB1) with thermostat markings is mode. DS is the PWM (pulse width modulation) in located outside the control box.
- Page 14 If a two speed condensing unit is used and Harmony or CCB1 6 − Watchguard Control Board (A18) is not used jumper DS to Y2. The blower will operate on the GC1 Control Only low speed heat/cool tap during first stage cooling (low speed The watchguard control board is illustrated in figure 7.
- Page 15 8 − K9 Isolation (Heat) Relay 2− Senses limit trip condition and turns on the blower. Q" Models Only 3− Controls the accessory relay. 4− Interfaces the 24VAC thermostat with the blower. Fan timing control (A28) with part number 79J65 con tains a single pole, single throw isolation relay (K9).
- Page 16 VSP1 provides an interface between the 24VAC indoor IMPORTANT thermostat signal and the direct current digital signal to the blower motor. The control is responsible for energizing the 24 VAC half wave rectified (DC pulse), when mea blower motor in response to thermostat demand and for sured with a meter, may appear as a lower or high converting thermostat demand from 24VAC to 24VAC half er voltage depending on the make of the meter.
- Page 17 B − VSP2 Blower Control Board (A24) VSP2 BLOWER CONTROL BOARD (A24) V" Models Only G21V−5 to −8 & GSR21V −10 to −15 (Figure 13) HIGH ADJUST HEAT IMPORTANT TEST − If fan off time is too low, residual heat in heat ex NORM changer may cause primary limit S10 to trip result HTG.
- Page 18 Jumper Settings IMPORTANT IMPORTANT 24 VAC half wave rectified (DC pulse), when mea sured with a meter, may appear as a lower or high Before changing jumper setting, make sure the er voltage depending on the make of the meter. motor has completely stopped.
- Page 19 b−HEATING BLOWER" WARNING − MAKE SURE TO DISCONNECT POWER BEFORE CHANGING FAN OFF" TIMINGS. Place the HEATING BLOWER jumper across the first and second pins for single−stage heating operation (position FAN OFF TIME ADJUSTMENT #1). For two−stage operation, place the jumper across the TIMING second and third pins (position #2).
- Page 20 TABLE 5 TABLE 6 FAN/LIMIT CONTROL Q" MODELS MODULATION CONTROL S78 V" MODELS UNIT LIMIT SETTING MODULATION SETTING UNIT 200° G21Q3 40 OPEN CLOSE 160° G21Q3/4 60 140°F 110°F G21V3 60 210° G21Q3 80 145°F 115°F G21V3 80 G21Q4/5 80 200°...
- Page 21 G21/GSR21 units. See figures 18 and 19. G21 and GSR21 series may be factory AUXILIARY equipped with Lennox GC 1, Lennox GC 3, or Johnson FAN CONTROL G891 ignition control modules. Ignition controls are inter 2 MOUNTING changeable.
- Page 22 2 − Lennox GC 3 Ignition Control (Figure 19) Watchguard The Lennox built GC 3 ignition control (A3) has a white or a All G21 / GSR21 units are equipped with a watchguard circuit. green plastic cover, and is illustrated in figure 19. The unit...
- Page 23 4 − Ignition Control Functions For GC 1, GC 3, A ceramic resistor spark plug must be used with and G891 (Figures 21 and 22) Lennox ignition controls. The ignition control (A3) provides four main functions: pre purge, ignition, flame sensing and post purge. The ignition at 3 −...
- Page 24 GC 1, GC 3, and G891 NORMAL IGNITION SEQUENCE (Timings Nominal) É É É É É É É É É É É É É É É É É É É É É PRE PURGE 30 SEC. POST PURGE 30 SEC ONDS THERMOSTAT DEMAND É...
- Page 25 VALVE ASSEMBLY quired components for field conversion to LP gas. An optional LP gas changeover kit is available from Lennox Repair Parts. G21 (upflow) units are not shipped with the required compo nents for field conversion to LP gas. An optional LP change SPRING over kit is available from Lennox Repair Parts.
- Page 26 H − Differential Pressure Switch (Figure 26) 1 − Gas Intake Flapper Valve & Assembly A union at the bottom of the expansion tank provides for re The differential pressure switch is mounted in the heating moval of gas flapper valve assembly and orifice access. compartment [see unit components illustration (page 10) The flapper moves freely over a spacer and is opened for exact location].
- Page 27 Exchanger maintenance. Removal of the plug/sensor is aided by a Lennox spark plug/sensor removal tool. See figure 29. It is Figures 30 and 31 identify all of the components of the ba available from Lennox Repair Parts, part no. 20H43.
- Page 28 G21 COMBUSTION COMPONENTS EXHAUST DECOUPLER TAILPIPE GAS VALVE RESONATOR EXPANSION TANK COMBUSTION CHAMBER ORIFICE (INSIDE) SENSOR PRESSURE TAP SPARK PLUG ELBOW GAS INTAKE MANIFOLD & FLAPPER VALVE ASSEMBLY RUBBER ISOLATION MOUNTS (4) VALVE BODY & AIR FLAPPER VALVE ASSEMBLY EXHAUST OUTLET MANIFOLD AIR INTAKE MANIFOLD RUBBER ISOLATION MOUNTS (4) CONDENSER COIL...
- Page 29 O − Blower Motors and Capacitors To Change Blower Speed Q" Units With Leadless Motors Only: (Q" Units) 1 − Turn off electric power to furnace. All G21/GSR21 Q" TABLE 8 2 − Lift left side filter over left support angle. For easy han units use direct drive G21Q/GSR21Q BLOWER RATINGS dling, hold filter at center bottom.
- Page 30 P − ICM1 and ICM2 BLOWER MOTOR The controller is primarily an a.c. to d.c. converter. Con verted d.c. power is used to drive the motor. The control (G21V/GSR21V Units) ler contains a microprocessor which monitors varying G21V/GSR21V units use a three phase, electronically con conditions inside the motor (such as motor workload).
- Page 31 The motor controller is driven by the VSP. The VSP re The DC filter capacitors inside the controller are connected electrically to the speed tap wires. The capacitors take ceives its demand (PWM signal or fixed 24 VAC or VDC sig approximately 5 minutes to discharge when the disconnect nal) from optional controls such as the Harmony zone con is opened.
- Page 32 MOTOR SPEED CONTROL WITH D.C. PULSE WIDTH MODULATION Motor speed is determined by the size of the electrical pulse sent to the motor windings. The longer the pulse, the faster the motor. OUTPUT FROM CONTROLLER TO MOTOR WINDINGS WINDINGS TURNED OFF WINDINGS TURNED ON Ç...
- Page 33 1 − External Operation ICM1 TABLE 12 FACTORY BLOWER SPEED TAP SELECTION (Speed Tap Priority) LOW SPEED HIGH SPEED HIGH SPEED MODEL NUMBER HEAT/COOL COOLING HEATING Figure 37 shows the two quick connect jacks (J48 and G21V3−60 J49) which connect the motor to the G21V/GSR21V. Jack G21V3−80 J48 is the power plug and jack J49 connects the unit con GSR21V3−80...
- Page 34 gether. This forces the blower to run on the high BLOWER B3 SPEED TAPS LOW SPEED HEAT/COOL WHITE CON speed cool tap. DS1 and DS3 LEDs are lit to in NECTOR HIGH SPEED HEAT dicate blower operation on the high speed cool RED CONNECTOR ing tap.
- Page 35 2 − External Operation ICM2 3 − Precautions ICM1 and ICM2 (Speed Tap Priority) If the G21V/GSR21V or its electronically controlled blower mo tor is improperly or inadequately grounded, it may cause tele Figure 40 shows the two quick connect jacks (J48 and vision interference (commonly known as RFI or radio frequen J49) which connect the motor to the G21V/GSR21V.
- Page 36 TABLE 13 VSP2−1 OPERATION HEATING MODE COOLING MODE UNITS WITH UNITS WITH UNITS WITH UNITS WITH SINGLE−SPEED TWO−SPEED SINGLE−STAGE HEATING TWO−STAGE HEATING COMPRESSOR COMPRESSOR NON−ZONED NON−ZONED NON−ZONED NON−ZONED APPLICATIONS APPLICATIONS APPLICATIONS APPLICATIONS With the HTG. BLOWER jumper in With the HTG. BLOWER jumper in The terminals DS"...
- Page 37 TYPICAL GSR21 HORIZONTAL INSTALLATION* When viewing unit from front, circu lating air blower compartment must WASHER AND 2 NUTS be located to the right. RAFTERS BRACED FOR INTAKE PIPE SUPPORT (2" PVC) EXHAUST PIPE (2" PVC) MUFFLER** SUPPORT MANUAL MAIN SHUT OFF VALVE SCREW MUFFLER** REDUCER...
- Page 38 TYPICAL G21 INSTALLATION* INTAKE PIPE (2" PVC) FLEXIBLE BOOT IN DUCT OR PLENUM (SUPPLY AIR) SUPPLY AIR RETURN MUFFLER** FLEXIBLE BOOT IN SUPPLY AIR PLENUM DUCT OR PLENUM 1.5 TO 3 LB. DENSITY, MATTE FACE, (RETURN AIR) 1 INCH THICK INSULATION INSULATED PAST FIRST ELBOW MANUAL MAIN SHUT OFF VALVE...
- Page 39 TYPICAL GSR21 DOWNFLOW INSTALLATION* FLEXIBLE BOOT IN DUCT (RETURN AIR) RETURN AIR PLENUM 1.5 TO 3 LB. DENSITY, MATTE FACE, 1 INCH THICK INSULATION INSULATED PAST FIRST ELBOW FLEXIBLE BOOT IN EXHAUST PIPE DUCT (RETURN AIR) (2" PVC) RETURN MUFFLER** INTAKE PIPE (2"...
- Page 40 H − Gas Supply Piping Centered In Inlet Hole (Figure 46) Use only Lennox heat cable kits which are approved for use with PVC pipe. The gas supply pipe should not rest on the unit cabinet. See J −...
- Page 41 ELBOW (Must be left open.) (Factory Installed) the unit is installed on a combustible floor (downflow installa CONDENSATE tions). It is available from Lennox Repair Parts. CONNECTION P − Drain Pan (Rotate to proper drain position before A drain pan should be used in all applications where surround PVC PIPE cementing.)
- Page 42 4 − Remove float cap, float, seat, and o ring and visually EXHAUST PIPING INTAKE inspect for cuts or breakdown of material. If seat, float CONNECTION or o ring are worn, a G21/GSR21 Condensate Trap Parts Replacement Kit is available from Lennox Repair BARBED FITTING COMPRESSION (Point toward COUPLING Parts.
- Page 43 TABLE 14 WARNING MINIMUM DIAMETER FOR G21/GSR21 VENTING Number of 90° Elbows Pipe Length (Max. Feet) After reassemble, double check all connections to prevent exhaust products from entering living space. 2−1/2 2−1/2 2−1/2 S − Concentric Termination 2−1/2 2−1/2 2−1/2 (Figures 55, 56 and 57 ) 2−1/2 2−1/2...
- Page 44 WALL TERMINATION KIT SIDE VIEW WALL TERMINATION 12" MAX. UNCONDITIONED GASKET SPACE REDUCE TO 1−1/2" 1−1/2" PVC 8" EXHAUST PIPE OUTSIDE WALL MIN. INTAKE PIPE KIT IS DESIGNED TO PENETRATE 12"INCHES INTO WALL. IF NECESSARY ADD COUPLINGS FOR MORE DEPTH. FIGURE 58 PROVIDE SUPPORT FOR INTAKE AND EXHAUST...
- Page 45 Filter Handicoater is RP Products 2 − Check for correct voltage. coating no. 418 and is available from Lennox Repair 3 − Select fuse and wire size according to blower motor Parts (No. P 8 5069).
- Page 46 G − Cleaning Heat Exchanger Assembly 16− Disconnect blower motor wires from control box. 17−Disconnect spark plug and sensor wires from plugs in IMPORTANT combustion chamber. (Access plate is provided.) 18− Remove vest panel. Use papers or protective covering in front of fur 19−...
- Page 47 B − External Static Pressure 5 − If the unit is not operational SEE CAUTIONS AND WARNINGS BELOW. Check the manifold pressure 1 − Measure tap locations as shown in figure 62. immediately after the gas valve fully opens. EXTERNAL STATIC PRESSURE TEST 6 −...
- Page 48 3 − Connect (+) end of transducer lead to TRANSDUCER GC 3 sensor terminal. #78H5401 avail (PART #78H5401) 4 − Connect (−) end to sensor wire. able from Lennox SET DIAL TO MEASURE Repair Parts) is re quired to measure TRANSDUCER flame signal PART no.
- Page 49 F − Exhaust CO (Carbon Dioxide) Content /CO SAMPLING PROCEDURE (GSR21 SHOWN) Carbon Dioxide is a colorless and odorless gas produced in small amounts by all furnaces during the combustion process. When the unit is properly installed and operating TEST EQUIPMENT normally CO content of the exhaust gas is within 8.0 10.0 1/8"...
- Page 50 K − Condensate pH Range For new units, approximate input measurements may be ob tained after allowing unit to run continuously for 15 minutes. If Unit condensate is mildly acidic and can be measured with accurate input measurements are required, the following pro pH indicators.
- Page 51 (frayed) edges, the material must N − Checking Air Intake and Flapper Valve be replaced. A flapper material is available from Lennox Figures 70, 71 and 72 Repair Parts. Flapper should be replaced every four 1 −...
- Page 52 Special screws are used in the air flapper valve. VALVE BODY THERMOPLASTIC Replacement screws are available in kit form from STAMPS IN SAME THERMOPLASTIC BUSHING Lennox Repair Parts. Do not use Loctite or similar QUADRANT AND ELASTOMER FACING AWAY thread seizing compounds to secure screws. FROM UNIT GASKET...
- Page 53 ERS ON THE FLAPPER VALVE THREADS. 40, 50, 60, 80 AIR FLAPPER VALVE CLEARANCE P − Checking Gas Orifice CLEARANCES ARE SUBJECT TO CHANGE. REFER TO LENNOX REPAIR PARTS OR SERVICE AND APPLICATION NOTES HEATING TAB FOR LATEST INFORMATION. 1 − With gas flapper valve assembly removed, use a flash CLEARANCE light to check for blockage of the orifice in the manifold.
- Page 54 VI − TROUBLESHOOTING When troubleshooting a unit, be sure that all basic checks are covered carefully. Double check your diagnosis before replacing components. DO AS LITTLE DISASSEMBLY AS IMPORTANT POSSIBLE during troubleshooting to prevent introducing additional problems such as gas or air leaks or damage to Normal set up conditions of a new unit installation re quire running the unit through several tries for igni components.
- Page 55 ICM2 CHECK−OUT 1 2 3 4 A kit is available from the Lennox parts center to use in testing the variable speed motor. The kit 70J11 includes a test plug harness to facilitate ICM2 check−out. Follow testing procedures outlined in the instructions provided with the kit.
- Page 56 D − Blower Runs Continuously Q" Motor G − Abnormal Sounds Corrective action is required if abnormal hissing 1 − Is thermostat blower switch set to ON?" If so, sounds around the air decoupler are heard. This switch to AUTO." problem may be caused by: 2 −...
- Page 57 VII − TROUBLESHOOTING FLOWCHARTS IGNITION CONTROL CHECKOUT GC1 START HERE IS RED DIAGNOSTIC LED LIT? CONTROL SHOULD OPERATE PROPERLY PROCEED TO UNIT WILL NOT RUN"−GAS CHECKS AND SPARK CHECKS TO RULE OUT OTHER POSSIBILITIES. TURN OFF UNIT POWER AT DISCONNECT FOR AT LEAST 3 SECONDS, THEN TURN POWER BACK ON.
- Page 58 IGNITION CONTROL CHECKOUT GC3 START HERE IS GREEN DIAGNOSTIC LED LIT? NOT LIT FLASHING Control should operate properly. Pro Turn off unit power at disconnect for at least 3 ceed to UNIT WILL NOT RUN"−GAS seconds. Then turn power back on. Allow 3 sec CHECKS AND SPARK CHECKS to onds for control to power−up.
- Page 59 ELECTRICAL CHECKOUT NOTE− Numbered steps refer to illustrations on page 61. IS THERMOSTAT PROPERLY SET? SYSTEM MAY BE LOCKED OUT. TURN THERMOSTAT HEATING DEMAND SET FOR HEAT DEMAND OFF AND ON AGAIN. NOTE CONTINUE THROUGH TROUBLESHOOTING FLOW CHART TO LOCATE REASON FOR LOCKOUT. CHECK FOR 120VAC POWER TO UNIT &...
- Page 60 GAS, AIR and SPARK CHECKS NOTE− Numbered steps refer to illustrations on page 61. CONTINUED FORM UNIT WILL NOT RUN CHECKS CHECK FOR LEAKS IN UNIT MANIFOLD PIPING. FLOW CHART ON PREVIOUS PAGE IS GAS SUPPLY NATURAL OR L.P.? LEAKS NO LEAKS L.P.
- Page 61 ELECTRICAL TESTING CHECK VOLTAGE AT TERMINAL AND CHECKING VOLTAGE AT PRIMARY CONTROL CHECKING THERMOSTAT DEMAND 24VAC? PRIMARY CONTROL LOW VOLTAGE TERMINAL STRIP WITH 3 AMP FUSE WIRING HARNESS PLUG (JP1) LOCATED ON CONTROL BOX 24VAC 24VAC POWER? WITH DEMAND? 24VAC? CHECKING VOLTAGE AT GAS VALVE 24VAC DURING LOW VOLTAGE TERMINAL...
- Page 62 "V" BLOWER ICM2 MOTOR AND VSP2−1 BLOWER CONTROL BOARD TROUBLESHOOTING FLOW CHART DOES UNIT OPERATE? CHECK: 1−UNIT POWER IS 24VAC ACROSS 2−INTERLOCK SWITCH R AND C? 3−TRANSFORMER COOLING MODE 4−LIMIT SWITCH PLACE JUMPER ACROSS R AND G. IS BLOWER ON LOW SPEED AND IS ON/OFF"...
- Page 63 V" BLOWER AND VSP1 BLOWER CONTROL BOARD HEATING MODE CHECKOUT START HERE DOES UNIT OPERATE? CHECK OUT ELECTRONICALLY CONTROLLED BLOWER MOTOR AND VSP1 SEE SECTION VIII NEW UNIT START UP CHECK: 1−UNIT POWER IS 24VAC ACROSS 2−INTERLOCK SWITCH VSP1 PIN 8 AND 1 3−TRANSFORMER OF VSP1? 4−TRANSFORMER FUSE...
- Page 64 V" BLOWER AND VSP1 BLOWER CONTROL BOARD HEATING MODE CHECKOUT (contd.) START HERE IN ADDITION TO R AND W1, JUMPER HB AND W2. HEATING MODE DOES BLOWER SHIFT TO DS3 DS2 DS1 (contd.) HIGH HEAT SPEED AND CHECK UNIT WIRING AND IF CORRECT ARE DS1 AND DS2 LIT? REPLACE THE VSP1.
- Page 65 V" BLOWER AND VSP1 BLOWER CONTROL BOARD COOLING MODE CHECKOUT START HERE DOES UNIT OPERATE? CHECK OUT ELECTRONICALLY CONTROLLED BLOWER MOTOR AND VSP1 SEE SECTION VIII NEW UNIT START UP CHECK: 1−UNIT POWER IS 24VAC ACROSS J73 2−INTERLOCK SWITCH PIN 8 AND 1 3−TRANSFORMER OF VSP1? 4−TRANSFORMER FUSE...
- Page 66 TERMINALS IMMEDIATELY AFTER & RETEST UNIT UNIT SHUTS OFF. METER READS INFINITE( )OHMS WHEN SWITCH REMOVE & CHECK SPARK PLUG (USE LENNOX CUTS UNIT OUT. PART #20H43 OR 3/4" SPARK PLUG SOCKET). 1. WAS PLUG TIGHT WHEN REMOVED? 2. ARE CRACKS PRESENT IN PORCELAIN? 3.
- Page 67 & RETEST UNIT IF RECIRCULATION IS NOT PRESENT, CHECK FOR ADEQUATE GROUNDING OF UNIT AND PRIMARY CONTROL. IF OK, CHECK REMOVE & CHECK SPARK PLUG (USE LENNOX PRIMARY CONTROL TIMING: PART #20H43 OR 3/4" SPARK PLUG SOCKET). MONITOR MANIFOLD PRESSURE OR GAS VALVE COIL, PURGE BLOWER (120 VAC), 1.
- Page 68 UNIT RUNS BUT SHUTS OFF BEFORE THERMOSTAT IS SATISFIED−INSUFFICIENT HEAT START HERE ARE LIMITS CUTTING OUT UNIT? CHECK FOR OPEN LIMIT IMMEDIATELY FOLLOWING UNIT CUTOUT. SHUT OFF POWER AND MAKE OHM METER CHECK. MAKE OHM METER CHECK ACROSS TERMINALS IMMEDIATELY AFTER UNIT SHUTS OFF.
- Page 69 Typical G21Q Diagram (−9 model shown) 21 22...
- Page 70 9− Combustion air blower B6 is de energized .5 seconds after ignition is sensed or after 8.0 seconds if ignition is not sensed. (Early GC 3, in later versions The following is an explanation of Lennox’ model number designa and G891 the combustion air blower B6 is de energized after 8 seconds).
- Page 71 TYPICAL GSR21Q DIAGRAM (−11 MODEL SHOWN)
- Page 72 Sequence of Operation GSR21Q C−APPLICATION OF GSR21Q WITH GC3 IGNITION CONTROL End of Heating Demand: This flowchart is used to show the step by step sequence that takes 12−Heating demand is satisfied. place when thermostat demand is sent to the GSR21Q. The se 13−Ignition control A3 is de energized.
- Page 73 G21V...
- Page 74 Sequence of Operation G21V D−OPERATION SEQUENCE G21V WITH GC3 IGNITION CONTROL Heating Two Stage (APPLICATIONS WITH A TWO STAGE THERMOSTAT / NM CAN NOT BE This flowchart is used to show the step by step sequence that takes place when thermostat demand USED WITH TWO STAGE) −...
- Page 75 GSR21V...
- Page 76 Sequence of Operation GSR21V E−OPERATION SEQUENCE GSR21V WITH GC3 IGNITION CONTROL Heating Two Stage (APPLICATIONS WITH A TWO STAGE THERMOSTAT / NM CAN NOT BE USED WITH TWO−STAGE) − Heating Blower jumper in position # 2. This flowchart is used to show the step by step sequence that takes place when thermostat demand is sent to the GSR21V.
- Page 77 G21Q with GC3 Ignition Control...
- Page 78 Sequence of Operation G21Q with GC3 Ignition Control F−EXPLANATION OF LENNOX’ MODEL NUMBER DESIGNATIONS: End of Heating Demand: The following is an explanation of Lennox’ model number designations: 12− Heating demand is satisfied. 13− Ignition control A3 is de energized.
- Page 79 G21Q with GC1 Ignition Control 30 29 16 17...
- Page 80 Sequence of Operation G21Q with GC1 Ignition Control H−APPLICATION OF G21Q WITH GC1 IGNITION CONTROL End of Heating Demand: 12− Heating demand is satisfied. This flowchart is used to show the step by step sequence that takes place when thermostat demand 13−...
- Page 81 GSR21Q with GC3 Ignition Control...
- Page 82 Sequence of Operation GSR21Q with GC3 Ignition Control I−APPLICATION OF GSR21Q WITH GC3 IGNITION CONTROL End of Heating Demand: 12− Heating demand is satisfied. This flowchart is used to show the step by step sequence that takes place when thermostat demand 13−...
- Page 83 GSR21Q with GC1 Ignition Control...
- Page 84 Sequence of Operation GSR21Q with GC1 Ignition Control J−APPLICATION OF GSR21Q WITH GC1 IGNITION CONTROL End of Heating Demand: 11− Heating demand is satisfied. This flowchart is used to show the step by step sequence that takes place when thermostat demand 12−...
- Page 85 G21V with GC1 Ignition Control...
- Page 86 Sequence of Operation G21V With GC1 Ignition Control K−OPERATION SEQUENCE G21V WITH GC1 IGNITION CONTROL Heating Two Stage This flowchart is used to show the step by step sequence that takes place when thermostat demand (APPLICATIONS WITH A TWO STAGE THERMOSTAT) is sent to the G21V.
- Page 87 G21V with GC3 Ignition Control...
- Page 88 Sequence of Operation G21V With GC3 Ignition Control L−OPERATION SEQUENCE G21V WITH GC3 IGNITION CONTROL 15− Internal circuitry of the VSP1 forces the blower to run on high speed heat tap when HB and W2 are jumpered together via the field installed jumper. Blower operates on high speed heat tap. This flowchart is used to show the step by step sequence that takes place when thermostat demand is sent to the G21V.
- Page 89 GSR21V with GC1 Ignition Control...
- Page 90 Sequence of Operation GSR21V With GC1 Ignition Control M−OPERATION SEQUENCE GSR21V WITH GC1 IGNITION CONTROL 16− Internal circuitry of the VSP1 forces the blower to run on high speed heat tap when HB and W2 are jumpered together via the field installed jumper. Blower operates on high speed heat tap. This flowchart is used to show the step by step sequence that takes place when thermostat demand is sent to the GSR21V.
- Page 91 GSR21V with GC3 Ignition Control...
- Page 92 Sequence of Operation GSR21V With GC3 Ignition Control N−OPERATION SEQUENCE GSR21V WITH GC3 IGNITION CONTROL 15− Internal circuitry of the VSP1 forces the blower to run on high speed heat tap when HB and W2 are jumpered together via the field installed jumper. Blower operates on high speed heat tap. This flowchart is used to show the step by step sequence that takes place when thermostat demand 16−...
- Page 93 TABLE 18 G21V/GSR21V OPERATION SEQUENCE AND JUMPERS SUMMARY WITH VSP2−1 (HEATING) MATCH UP JUMPER COMMENTS OR SEQUENCE WIRING CONNECTIONS If no modulation FOR COOLING JUMPERS Blower operates on heating is desired, wire SEE TABLE 19 speed. Modulation control S78 Heating Blower heat demand may not cycle the unit.
- Page 94 TABLE 19 G21V/GSR21V OPERATION SEQUENCE AND JUMPERS SUMMARY WITH VSP2−1 (COOLING) MATCH UP JUMPER COMMENTS OR SEQUENCE WIRING CONNECTIONS FOR HEATING JUMPERS SEE TABLE 18 THERMOSTAT Blower operates on high Single Speed Compressor, DS" to G" speed cool tap during cooling. no CCB1, no Harmony OUTDOOR UNIT...
- Page 95 TABLE 19 (contd.) (continued from previous page) G21V/GSR21V OPERATION SEQUENCE AND JUMPERS SUMMARY WITH VSP2−1 (COOLING) MATCH UP JUMPER COMMENTS OR SEQUENCE WIRING CONNECTIONS FOR HEATING JUMPERS SEE TABLE 18 Blower speed is controlled by THERMOSTAT the DC signal from CCB1. Blower operates on low speed heat/cool tap during dehumidi CCB1 with Two Speed...
- Page 96 TABLE 20 G21Q/GSR21Q OPERATION SEQUENCE AND JUMPERS SUMMARY WITH VSP1 OR VSP2−1 (OPTIONAL COOLING ACCESSORIES) MATCH UP JUMPER COMMENTS OR SEQUENCE WIRING CONNECTIONS No Jumpers EBR1 Additional Wiring Re Blower operates on a lower EBR1 With CCB1 And quired inside speed tap during dehumidifi Single Speed Unit.
- Page 97 TABLE 21 G21V/GSR21V OPERATION SEQUENCE AND JUMPERS SUMMARY WITH VSP1 (HEATING) MATCH UP JUMPER COMMENTS OR SEQUENCE WIRING CONNECTIONS FOR COOLING JUMPERS SEE TABLE 22 THERMOSTAT Blower operates on the high Single Stage Heating HB" to W2" speed heat tap during the heat ing mode.
- Page 98 TABLE 22 G21V/GSR21V OPERATION SEQUENCE AND JUMPERS SUMMARY WITH VSP1 (COOLING) MATCH UP JUMPER COMMENTS OR SEQUENCE WIRING CONNECTIONS FOR HEATING JUMPERS SEE TABLE 21 THERMOSTAT OUTDOOR UNIT Single Speed Compres Blower operates on high sor, no CCB1, no Har DS"...
- Page 99 TABLE 22 (contd.) (continued from previous page) G21V/GSR21V OPERATION SEQUENCE AND JUMPERS SUMMARY WITH VSP1 (COOLING) MATCH UP JUMPER COMMENTS OR SEQUENCE WIRING CONNECTIONS FOR HEATING JUMPERS OUTDOOR SEE TABLE 21 Blower speed is controlled by UNIT THERMOSTAT the DC signal from CCB1. Blower operates on low speed heat/cool tap during dehumidi CCB1 with Two Speed...
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