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Lennox G17Q2-50, Unit Information

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Lennox G17Q2-50 Unit Information Download Page 13

Page 13

CHECK:

1-UNIT POWER

2-INTERLOCK SWITCH

3-TRANSFORMER

4-LIMIT SWITCH

START

IS

24VAC ACROSS

R & T?

YES

JUMPER ACROSS

SCREWS R & G

YES

DOES UNIT

OPERATE?

NO

NO

IS

BLOWER

RUNNING ON HIGH

SPEED?

NO

IS

120VAC ACROSS

N1 & A?

REPLACE

BCC2-1

NO

YES

YES

CHECK BLOWER

WIRING AND

BLOWER

IS

120VAC ACROSS

N1 & ACC?

NO

REPLACE

BCC2-1

YES

JUMPER ACROSS

 R &W

(REMOVE R & G JUMPER)

IS

DAMPER MOTOR

ON?

NO

REPLACE

BCC2-1

NO

IS

120VAC ACROSS

N1 & CAB?

CHECK

DAMPER MOTOR

WIRING AND

DAMPER MOTOR

YES

YES

ARE

BURNERS

 LIT?

NO

CHECK:

1-DAMPER MOTOR

2-IGNITION CONTROL

3-GAS VALVE

4-IGNITOR

5-LIMIT SWITCHES

6-PROVE SWITCH

YES

IS BLOWER 

RUNNING ON LOW

SPEED, 45 SEC.

AFTER FURNACE

LIGHTS?

NO

IS

120VAC ACROSS

N1 & H?

YES

IS

24VAC ACROSS

T & V?

REPLACE

BCC2-1

NO

NO

CHECK

WIRING

YES

IS

120VAC ACROSS

N1 & ACC?

YES

REMOVE

R & W JUMPER

AFTER

THE SELECTED

TIME, DOES THE

BLOWER TURN

OFF?

YES

NO

YES

REPLACE

BCC2-1

END OF TEST

BCC2-1

TROUBLESHOOTING

FLOWCHART

NO

REPLACE

BCC2-1

CHECK BLOWER

WIRING AND

BLOWER

FIGURE 15

Summary of Contents for G17Q2-50

Page 1: ...ines and procedures outlined in this manual except where noted are recommended only and do not constitute code Model No Input Btuh Output Btuh A F U E Flue connection in diameter round Temperature rise range F High static certified by A G A in wg Gas Piping Size I P S inches Natural LPG Blower wheel nominal diameter x width in Blower motor hp Number and size of filters in Electrical characteristic...

Page 2: ...E PILOT ELECTRODE ASSEMBLY LIMIT W R W Y T G 90 150 270 210 24V TCOM VALVE SENSE G17 CONTROL BOX BCC2 BLOWER CONTROL CENTER INB N1 CABN XFMRN N CAB L1 A XFMR D D H ACC FIGURE 2 NEUTRAL TERMINALS ACCESSORY TERMINAL THERMOSTAT CONNECTIONS BLOWER TIME ADJUSTMENT JUMPER HEATING SPEED TAP TERMINAL COOLING SPEED TAP TERMINAL DUMMY TERMINALS GROUND SCREW DOOR INTERLOCK SWITCH 120VAC 24VAC TRANSFORMER NOT...

Page 3: ...ich controls the blower and monitors primary limit and gas valve operation The control has a non adjustable factory preset on fan timĆ ing Fan off timings are adjustable The board is divided into two sections 120 and 24VAC Line voltage comes into the board on the 120VAC side See figure 2 CAB and XFMR send 120VAC to the damper motor and transformer respectively The active cooling and heating blower...

Page 4: ...ted in series with the ignition control A3 When S47 senses rollout the ignition control immediately stops ignition and closes the gas valve If unit is running and flame rollout is detected the gas valve will close and ignition conĆ trol will be disabled Rollout can be caused by a reverse draft blocked flue or lack of combustion air The switch is factory set and cannot be adjusted See table 2 The s...

Page 5: ...t and outlet pressure taps are located on the valve A pilot adjusting screw and regulator adjustment screw figĆ ures 7 and 9 are located on the valve Refer to figure 8 for exact location of valve features FIGURE 7 Robertshaw 7200 gas valve shown GAS VALVE SELECTOR ARM IN OFF POSITION REGULATOR COVER SCREW ADJUSTING SCREW SPRING TYPICAL ACCESS TO REGULATOR FOR ADJUSTMENT AND L P CHANGEOVER An LPG c...

Page 6: ...pped for service to the damper door or burner box The spring must be removed in order to remove the damper door After service is complete the spring must rest snugly in notch for damper prove switch to function properly Do not force door open damage to the spring and motor may ocĆ cur Take care to open damper door slowly DAMPER PROVE SWITCH SPRING SPRING FITS SNUGLY IN NOTCH FIGURE 11 AXLE DAMPER ...

Page 7: ...gas supply FIGURE 13 MANUAL MAIN SHUT OFF VALVE WILL NOT HOLD TEST PRESSURE IN EXCESS OF 0 5 PSIG 14 W C GAS VALVE CAP GAS PIPING TEST PROCEDURE FIELD PROVIDED LINE PRESSURE TAP When checking piping connections for gas leaks use preĆ ferred means Kitchen detergents can cause harmful corroĆ sion on various metals used in gas piping Use of a specialty Gas Leak Detector is strongly recommended It is ...

Page 8: ...tion of 2 000 ft 610 m or more above sea level Tables 5 and 6 show the derated manifold pressure for high altitude operation with both natural and LP Propane gas Operating this appliance at the manifold pressure specified on the tables will ensure proper unit heat input at high altitude Consult your gas utility for the local natural gas heating value 2 25 wc Altitude Heating Value Btu Ft Ft 900 95...

Page 9: ...emperature is too low decrease blower speed If temperature is too high first check the firing rate Provided the firing rate is acceptable inĆ crease blower speed to reduce temperature To change blower speed taps see the Blower Speed Taps section in this manual C External Static Pressure 1 Measure tap locations as shown in figure 15 2 Punch a 1 4 diameter hole in supply and return air pleĆ nums Ins...

Page 10: ...m filter applications for use on G17Q5 6 100 and G17Q5 6 125 reĆ quire an optional kit available from Lennox G17X models are factory equipped for use with bottom return air only If side reĆ turn air is desired an optional kit is available See figure 17 Filters must be cleaned or replaced when dirty to assure proper unit operation Replace with same hogshair type filter material cut to specific meas...

Page 11: ...h burner with a bottle cleaning brush See figĆ ure 21 6 Replace burners making sure to fully engage in rear receiving slot in heat exchanger See figure 22 ReseĆ cure gas manifold and supply piping 7 Resecure damper assembly damper prove switch cover and burner box top Carefully open damper by hand to ensure that the damper spring closes damper correctly and that the damper prove switch is engaged ...

Page 12: ...loses assuming the flame rollout switch S47 and blocked vent shutoff switch S62 are closed 24VAC is supplied to the TH terminal of the electronic control A3 7 Through the electronic control the pilot valve P of the gas valve opens The spark electrode ignites the pilot and the flame sensor senses the pilot 8 When flame is sensed the main gas valve opens and supplies the burners with gas 9 Terminal ...

Page 13: ...EPLACE BCC2 1 NO IS 120VAC ACROSS N1 CAB CHECK DAMPER MOTOR WIRING AND DAMPER MOTOR YES YES ARE BURNERS LIT NO CHECK 1 DAMPER MOTOR 2 IGNITION CONTROL 3 GAS VALVE 4 IGNITOR 5 LIMIT SWITCHES 6 PROVE SWITCH YES IS BLOWER RUNNING ON LOW SPEED 45 SEC AFTER FURNACE LIGHTS NO IS 120VAC ACROSS N1 H YES IS 24VAC ACROSS T V REPLACE BCC2 1 NO NO CHECK WIRING YES IS 120VAC ACROSS N1 ACC YES REMOVE R W JUMPER...

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