Lennox G23Q2-50 Installation and operation manual

Page 1 ã1998 LennoxIndustriesInc.
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Corp.9814-L8 G23(X)
Service LiteratureRevised 08-2001
G23(X)SERIES UNITS
G23(X)seriesunitsaremid-efficiency upflowgasfur-
nacesmanufactured withDuraloktaluminized steel
clamshell type heatexchangers.G23(X)unitsare avail-
ablein heating capacitiesof50,000 to 150,000 Btuh and
cooling applicationsup to6tons.RefertoEngineering
Handbookforpropersizing.
Unitsarefactoryequipped forusewith naturalgas.Akitis
availableforconversion to LPGoperation.G23(X)-1,-2,-3
and-4modelunitsuseelectronic(intermittentpilot)ignition.
G23(X)-5 and -6modelunitsfeaturethe LennoxSur-
eLightTsilicon nitride ignition system.All unitsmeet the
CaliforniaNitrogen Oxides(NOx)Standardsand California
SeasonalEfficiency requirementswiththe installation of
flame baffles.All unitsusearedundantgas valveto assure
safety shut-off asrequired byA.G.A.orC.G.A.
Informationcontained inthismanualisintended foruseby
qualified servicetechniciansonly.All specificationsare
subject tochange.Proceduresoutlined inthismanualare
presented asarecommendation onlyand do notsuper-
sede or replacelocalorstatecodes. Inthe absence oflo-
calorstatecodes, the guidelinesand proceduresoutlined
inthismanual(exceptwhere noted)arerecommended
only.SPECIFICATIONS
ModelNo.G23Q2(X)-50 G23Q3(X)-50 G23Q2/3(X)-75 G23Q4/5(X)-75 G23Q3(X)-100
InputBtuh (kW)50,000 (14.7)75,000 (22.0)100,000 (29.3)
OutputBtuh (kW)40,000 (11.7)61,000 (17.8)80,000 (23.4)
lA.F.U.E.80.7%80.8%80.4%80.1%
CaliforniaSeasonalEfficiency 75.5%75.6%76.9%74.2%76.6%
Flue sizeconnection diameter—in.(mm) round 3 (76)4(102)
Temperatureriserange —_F(_C)30-60 (17-33)35-65 (19-36)20-50 (11-28)45-75 (25-42)
High static certified byA.G.A.—inwg.(Pa).50 (125)
G
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P
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S
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I
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P
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.
in.1/2
G
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P
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S
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I
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P
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NaturalorLPG/propane mm 12.7
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in.10 x7 10 x8 11-1/2x9 10 x8
B
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a
l
diameterxwidthmm 254 x178 254 x203 292 x229 254 x203
Blowermotoroutput—hp (W)1/5(149)1/3(249)3/4(560)1/3(249)
N
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c
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Tons1to2 1to 3 3-1/2to5 1to 3
N
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a
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c
o
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g
thatcan be added kW3.5to 7.0 3.5to 10.6 12.3to 17.6 3.5to 10.6
Shipping weight—lbs.(kg)1 package 135 (61)140 (64)146 (66)186 (84)159 (72)
Electricalcharacteristics 120 volts—60 hertz—1 phase(all models) (less than 12 amps)
lAnnualFuel Utilization Efficiency based on U.S.DOEtestproceduresand FTC labeling regulations. Isolated combustion system rating fornon-weatherized furnaces.
}Cleanable polyurethane frametype filter.

3DJH 
SPECIFICATIONS
Model No. G23Q3/4(X)-10
0G23Q4/5(X)-10 0G23Q3/4(X)-12 5G23Q5/6(X)-125 G23Q5/6(X)-15 0
Input Btuh (kW) 100,000 (29.3) 125,000 (36.6) 150,000 (44.0)
Output Btuh (kW) 80,000 (23.4) 81,000 (23.7) 100,000 (29.3) 120,000 (35.2)
R A.F.U.E. 80.7% 80.1% 80.0% 80.4% 80.0%
California Seasonal Efficiency 77.3% 75.9% 76.3% 76.8% 76.8%
Flue size connection diameter in. (mm) round 4 (102) 5 (127)
Temperature rise range  E F( E C) 40-70 (22-39) 30-60 (17-33) 45-75 (25-42) 35-65 (19-36) 40-70 (22-39)
High static certified by A.G.A.  in wg. (Pa) .50 (125)
Gas Piping Size I.P.S. in. 1/2
Gas Piping Size I
.
P
.
S
.
Natural or LPG/propane mm 12.7
Blower wheel nominal in. 10x8 11-1/2 x 9 10x10 12x12
Blower wheel nominal
diameter x width mm 254 x 203 292 x 229 254 x 254 305 x 305
Blower motor output  hp (W) 1/2 (373) 3/4 (560) 1/2 (373) 3/4 (560)
Nominal cooling Tons 2to4 3-1/2 to 5 2to4 5 and 6
Nominal cooling
that can be added kW 7.0 to 14.1 12.3 to 17.6 7.0 to 14.1 17.6 and 21.1
Shipping weight  lbs. (kg) 1 package 143 (65) 167 (76) 195 (88) 218 (99) 223 (101)
Electrical characteristics 120 volts  60 hertz  1 phase (all models) (less than 12 amps)
R Annual Fuel Utilization Efficiency based on U.S. DOE test procedures and FTC labeling regulations. Isolated combustion system rating for non-weatherized fur-
naces.
c Cleanable polyurethane frame type filter.
G23Q2(X)-50 BLOWER PERFORMANCE
External Static
Air Volume and Motor Watts at Specific Blower Taps
External Static
Pressure High Medium Low
in. w.g. Pa cfm L/s Watts cfm L/s Watts cfm L/s Watts
0 0 1225 580 530 950 450 375 785 370 295
.10 25 1215 575 520 945 445 375 770 365 290
.20 50 1190 560 505 925 435 360 745 350 280
.30 75 1150 545 485 895 420 350 720 340 275
.40 100 1090 515 460 865 410 335 690 325 265
.50 125 1030 485 440 820 385 320 645 305 250
.60 150 960 455 415 760 360 300 595 280 235
.70 175 865 410 390 690 325 285 535 250 225
.80 200 760 360 365 600 285 260 445 210 200
.90 225 630 295 340 520 245 240 ---- ---- ----
NOTE  All air data is measured external to unit with 1 in. (25 mm) cleanable foam filter (not furnished) in place. Also see Filter Air Resistance table.
G23Q3(X)-50 BLOWER PERFORMANCE
External Static Air Volume and Motor Watts at Specific Blower Taps
External Static
Pressure High Medium-High Medium-Low Low
in. w.g. Pa cfm L/s Watts cfm L/s Watts cfm L/s Watts cfm L/s Watts
0 0 1620 765 630 1380 650 510 1110 525 405 875 415 310
.10 25 1575 745 605 1350 635 490 1090 515 390 870 410 305
.20 50 1520 715 580 1315 620 465 1080 510 375 860 405 295
.30 75 1455 685 550 1275 600 445 1050 495 355 840 395 285
.40 100 1390 655 525 1230 580 425 1015 480 340 815 385 275
.50 125 1320 625 505 1165 550 400 975 460 325 775 365 265
.60 150 1240 585 480 1100 520 375 920 435 310 715 335 245
.70 175 1160 545 460 1030 485 360 830 390 280 620 295 220
.80 200 1075 505 440 900 425 320 700 330 250 535 250 205
.90 225 900 425 395 720 340 285 600 285 230 ---- ---- ----
NOTE  All air data is measured external to unit with 1 in. (25 mm) cleanable foam filter (not furnished) in place. Also see Filter Air Resistance table.

3DJH 
G23Q2/3(X)-75 BLOWER PERFORMANCE
External Static Air Volume and Motor Watts at Specific Blower Taps
External Static
Pressure High Medium-High Medium-Low Low
in. w.g. Pa cfm L/s Watts cfm L/s Watts cfm L/s Watts cfm L/s Watts
0 0 1600 755 620 1355 640 510 1080 510 395 865 410 310
.10 25 1545 730 595 1320 625 485 1060 500 385 855 405 305
.20 50 1490 705 570 1275 600 465 1035 490 370 830 390 295
.30 75 1425 670 550 1240 585 445 1010 475 360 810 380 285
.40 100 1370 645 530 1185 560 425 975 460 345 780 370 275
.50 125 1300 615 500 1135 535 405 940 445 330 735 345 260
.60 150 1240 585 485 1075 505 380 890 420 310 700 330 250
.70 175 1155 545 465 1000 470 360 830 390 290 625 295 230
.80 200 1045 495 430 905 425 330 720 340 265 555 260 215
.90 225 930 440 405 810 380 305 640 300 245 ---- ---- ----
NOTE  All air data is measured external to unit with 1 in. (25 mm) cleanable foam filter (not furnished) in place. Also see Filter Air Resistance table.
G23Q4/5(X)-75 BLOWER PERFORMANCE
External Static Air Volume and Motor Watts at Specific Blower Taps
External Static
Pressure High Medium-High Medium Medium-Low Low
in. w.g. Pa cfm L/s Watts cfm L/s Watts cfm L/s Watts cfm L/s Watts cfm L/s Watts
0 0 2365 1115 1360 2130 1005 1180 1850 875 995 1600 755 840 1360 640 710
.10 25 2360 1115 1355 2105 995 1175 1830 865 995 1575 745 835 1350 635 710
.20 50 2290 1080 1325 2055 970 1155 1800 850 985 1560 735 830 1325 625 705
.30 75 2235 1055 1310 2010 950 1135 1780 840 970 1530 720 820 1310 620 700
.40 100 2175 1025 1275 1970 930 1115 1735 820 945 1500 710 910 1290 610 690
.50 125 2110 995 1250 1910 900 1085 1700 800 930 1480 700 800 1265 610 685
.60 150 2030 960 1215 1855 875 1060 1650 780 910 1450 685 790 1250 590 675
.70 175 1955 925 1185 1765 835 1030 1610 760 895 1410 665 775 1220 575 670
.80 200 1890 890 1165 1695 800 1005 1550 730 875 1370 645 760 1190 560 655
.90 225 1800 850 1145 1600 755 980 1490 705 850 1340 630 730 1160 545 625
NOTE  All air data is measured external to unit with 1 in. (25 mm) cleanable foam filter (not furnished) in place. Also see Filter Air Resistance table.
G23Q3(X)-100 BLOWER PERFORMANCE
External Static
Air Volume and Motor Watts at Specific Blower Taps
External Static
Pressure High Medium Low
in. w.g. Pa cfm L/s Watts cfm L/s Watts cfm L/s Watts
0 0 1615 760 630 1300 615 500 1030 485 400
.10 25 1585 750 615 1290 610 490 1015 480 395
.20 50 1530 720 595 1255 590 475 1000 470 380
.30 75 1470 695 570 1220 575 455 975 460 365
.40 100 1400 660 545 1175 555 435 950 450 350
.50 125 1330 630 510 1125 530 415 910 430 340
.60 150 1250 590 485 1065 505 390 870 410 320
.70 175 1155 545 455 995 470 365 810 380 300
.80 200 1055 500 425 915 430 345 735 345 275
.90 225 950 450 400 820 385 320 650 305 250
NOTE  All air data is measured external to unit with 1 in. (25 mm) cleanable foam filter (not furnished) in place. Also see Filter Air Resistance table.

3DJH 
G23Q3/4(X)-100 BLOWER PERFORMANCE
External Static
Air Volume and Motor Watts at Specific Blower Taps
External Static
Pressure High Medium-High Medium-Low Low
in. w.g. Pa cfm L/s Watts cfm L/s Watts cfm L/s Watts cfm L/s Watts
0 0 1970 930 925 1675 790 750 1500 710 655 1180 555 505
.10 25 1895 895 880 1635 770 710 1480 700 635 1175 555 495
.20 50 1850 875 855 1600 755 680 1450 685 605 1170 550 485
.30 75 1790 845 825 1560 735 655 1420 670 580 1155 545 465
.40 100 1710 805 790 1515 715 630 1370 645 550 1130 535 450
.50 125 1635 770 760 1460 690 600 1315 620 520 1100 520 425
.60 150 1555 735 725 1390 655 565 1270 600 495 1060 500 410
.70 175 1470 695 690 1300 615 525 1195 565 470 1015 480 385
.80 200 1370 645 660 1225 580 500 1110 525 435 970 460 370
.90 225 1265 595 625 1115 525 455 1025 485 400 895 420 340
NOTE  All air data is measured external to unit with 1 in. (25 mm) cleanable foam filter (not furnished) in place. Also see Filter Air Resistance table.
G23Q4/5(X)-100 BLOWER PERFORMANCE
External Static Air Volume and Motor Watts at Specific Blower Taps
External Static
Pressure High Medium-High Medium Medium-Low Low
in. w.g. Pa cfm L/s Watts cfm L/s Watts cfm L/s Watts cfm L/s Watts cfm L/s Watts
0 0 2465 1165 1305 2230 1050 1115 1985 935 940 1735 820 770 1530 720 650
.10 25 2425 1145 1295 2170 1025 1085 1950 920 930 1700 800 765 1500 710 645
.20 50 2375 1120 1265 2130 1005 1065 1920 905 915 1670 790 750 1470 695 635
.30 75 2315 1090 1235 2090 985 1050 1880 885 895 1645 775 745 1440 680 630
.40 100 2255 1065 1210 2045 965 1040 1840 870 890 1610 760 735 1420 670 625
.50 125 2195 1035 1185 1995 940 1010 1815 855 880 1575 745 725 1390 655 615
.60 150 2135 1010 1155 1950 920 1000 1770 835 870 1530 720 715 1350 635 600
.70 175 2075 980 1145 1890 890 985 1710 805 850 1490 705 700 1295 610 595
.80 200 1985 935 1105 1825 860 960 1650 780 830 1435 675 690 1245 590 585
.90 225 1895 895 1080 1745 825 925 1585 750 810 1365 645 675 1170 550 570
NOTE  All air data is measured external to unit with 1 in. (25 mm) cleanable foam filter (not furnished) in place. Also see Filter Air Resistance table.
G23Q3/4(X)-125 BLOWER PERFORMANCE
External Static Air Volume and Motor Watts at Specific Blower Taps
External Static
Pressure High Medium-High Medium-Low Low
in. w.g. Pa cfm L/s Watts cfm L/s Watts cfm L/s Watts cfm L/s Watts
0 0 1980 935 800 1690 800 700 1470 695 610 1165 550 465
.10 25 1905 900 770 1670 790 680 1465 690 595 1160 545 455
.20 50 1850 875 740 1630 770 650 1430 675 570 1125 530 445
.30 75 1780 840 705 1580 745 620 1410 665 545 1120 530 430
.40 100 1695 800 670 1530 720 590 1375 650 520 1095 515 410
.50 125 1605 755 640 1455 685 550 1310 620 485 1065 505 390
.60 150 1525 720 605 1380 650 520 1245 590 455 1015 480 370
.70 175 1405 665 565 1280 605 485 1165 550 425 950 450 345
.80 200 1275 600 525 1160 545 440 1030 485 385 860 405 315
.90 225 1120 530 480 1000 470 390 915 430 355 780 370 295
NOTE  All air data is measured external to unit with 1 in. (25 mm) cleanable foam filter (not furnished) in place. Also see Filter Air Resistance table.

3DJH 
G23Q5/6(X)-125 BLOWER PERFORMANCE
External Static Air Volume and Motor Watts at Specific Blower Taps
External Static
Pressure High Medium-High Medium Medium-Low Low
in. w.g. Pa cfm L/s Watts cfm L/s Watts cfm L/s Watts cfm L/s Watts cfm L/s Watts
0 0 2460 1160 1295 2220 1050 1050 2000 945 900 1775 840 755 1595 755 645
.10 25 2455 1160 1285 2210 1045 1050 1990 940 900 1755 830 760 1570 740 645
.20 50 2450 1155 1280 2180 1030 1040 1965 925 895 1720 810 755 1535 725 645
.30 75 2445 1155 1270 2155 1015 1035 1930 910 885 1690 800 745 1500 710 645
.40 100 2440 1150 1265 2125 1005 1025 1890 890 875 1660 785 750 1470 695 640
.50 125 2430 1145 1255 2090 985 1020 1860 880 870 1620 765 745 1435 675 635
.60 150 2350 1110 1235 2040 965 1000 1810 855 855 1585 750 735 1395 660 635
.70 175 2300 1085 1210 1990 940 990 1770 835 845 1540 725 725 1345 635 620
.80 200 2220 1050 1185 1925 910 970 1715 810 830 1490 705 715 1270 600 605
.90 225 2120 1000 1140 1850 875 950 1640 775 800 1420 670 690 1200 565 590
NOTE  All air data is measured external to unit with 1 in. (25 mm) cleanable foam filter (not furnished) in place. Also see Filter Air Resistance table.
G23Q5/6(X)-150 BLOWER PERFORMANCE
External Static Air Volume and Motor Watts at Specific Blower Taps
External Static
Pressure High Medium-High Medium Medium-Low Low
in. w.g. Pa cfm L/s Watts cfm L/s Watts cfm L/s Watts cfm L/s Watts cfm L/s Watts
0 0 2565 1210 1430 2300 1085 1160 2055 970 970 1840 870 825 1620 765 680
.10 25 2560 1210 1420 2265 1070 1155 2020 955 960 1810 855 825 1590 750 680
.20 50 2555 1205 1410 2225 1050 1140 1980 935 955 1770 835 810 1555 735 680
.30 75 2550 1205 1400 2185 1030 1130 1935 915 945 1740 820 805 1515 715 675
.40 100 2500 1180 1380 2150 1015 1115 1900 440 935 1700 800 800 1470 695 670
.50 125 2440 1150 1365 2100 990 1105 1860 435 925 1645 775 790 1430 675 665
.60 150 2370 1120 1335 2045 965 1085 1790 430 910 1585 750 780 1380 650 660
.70 175 2300 1085 1310 1960 925 1055 1730 815 895 1530 720 770 1315 620 645
.80 200 2210 1045 1270 1920 905 1035 1640 415 875 1470 695 755 1210 570 635
.90 225 2110 995 1240 1855 875 1030 1550 730 855 1345 635 725 1100 520 625
NOTE  All air data is measured external to unit with 1 in. (25 mm) cleanable foam filter (not furnished) in place. Also see Filter Air Resistance table.
FILTER AIR RESISTANCE
CFM (L/S) in. w.g. (Pa)
0 (0) 0.00 (0)
200 (95) 0.01 (0)
400 (190) 0.03 (5)
600 (285) 0.04 (10)
800 (380) 0.06 (15)
1000 (470) 0.09 (20)
1200 (565) 0.12 (30)
1400 (660) 0.15 (35)
1600 (755) 0.19 (45)
1800 (850) 0.23 (55)
2000 (945) 0.27 (65)
2200 (1040) 0.33 (80)
2400 (1130) 0.38 (95)
2600 (1225) 0.44 (110)

3DJH 
OPTIONAL ACCESSORIES (Must be Ordered Extra)
Model No. G23Q3/4(X)-10
0G23Q4/5(X)-10 0G23Q3/4(X)-12 5G23Q5/6(X)-125 G23Q5/6(X)-15 0
LPG
/
Pro
p
ane kit
Standard
models
71K82
LPG/Propane kit
X models
15K03 15K04 15K05
Filter and Filter Rack Kits
c No. & size of filters - in. (mm) Single
(44J21) Ten Pack (66K62)
(1) 20 x 25 x 1 (508 x 635 x 25)
Horizontal Power Venter Kit
79J15 (all models)
Twinning Kits
Non-continuous low speed
64H88 (all models)
Twinning Kits Continuous low speed
35J93 (all models)
Continuous Low Speed Blower Switch (option-
al)
44J06 (all models) Not used with Twinning Kits
OPTIONAL ACCESSORIES (Must be Ordered Extra)
Model No. G23Q2(X)-50 G23Q3(X)-50 G23Q2/3(X)-75 G23Q4/5(X)-75 G23Q3(X)-100
LPG
/
Pro
p
ane kit
Standard
models
71K82
LPG/Propane kit
X models
15K01 15K02 15K03
Filter and Filter Rack Kits
c No. & size of filters - in. (mm) Single
(44J20) Ten Pack (66K61)
(1) 14 x 25 x 1 (356 x 635 x 25)
Single (44J21)
Ten Pack (66K62)
(1) 20 x 25 x 1
(508 x 635 x 25)
Single (44J22)
Ten Pack
(66K63)
(1)16x25x1
(406 x 635 x 25)
Horizontal Power Venter Kit
79J15 (all models)
Twinning Kits
Non-continuous low speed
64H88 (all models)
Twinning Kits Continuous low speed
35J93 (all models)
Continuous Low Speed Blower Switch
44J06 (all models) Not used with Twinning Kits
HIGH ALTITUDE
Pressure regulator adjustment may be required depending on alti-
tude. See table below for proper pressure regulator setting.
Manifold Absolute Pressure (Outlet) in. w.g. (kPa)
ALTITUDE ft. (m)
FUEL
0-4500
(0-1372) 4501-5500 (1373-1676) 5501-6500 (1677-1981) 6501-7500 (1982-2286)
Natural Gas 3.5 (.87) 3.3 (.82) 3.1 (.77) 3.0 (.75)
LPG/Propane 10.0 (2.49)
Pressure switch is factory set. No adjustment necessary. G23(X)-50/75 units use the
factory pressure switch from 0-7500 feet (0-2286 m). G23(X)-100/125 and G23(X)-150
units require a High Altitude Pressure Switch for units installed above 5000 feet (1524
m). Order ( 97J50 ) for G23(X)-100/125 and ( 18J35 ) for G23(X)-150.

3DJH 
FIGURE 1
G23(X) ORIENTATION
TOP PANEL
BURNER ACCESS PANEL
BLOWER ACCESS
DOOR SureLight Control
(-5 and -6 models only)
MAKE-UP BOX ASSEMBLY
SUPPLY AIR OPENING
HEATING COMPARTMENT
BLOWER COMPARTMENT
FIGURE 2
G23(X) GENERAL PARTS ORIENTATION
COMBUSTION AIR BLOWER
COMBUSTION AIR BLOWER
PROVE (PRESSURE)
SWITCH
GAS VALVE
PRIMARY LIMIT
MANIFOLD
BURNERS
SUPPLY AIR BLOWER
BLOWER CAPACITOR
CONTROL BOX
BLOWER COMPARTMENT
HEATING COMPARTMENT
FLUE TRANSITION
BLOWER DOOR
INTERLOCK SWITCH
IGNITION CONTROL
(-1 through -4 models only)
SUPPLY AIR DUCT FLANGE
ROLLOUT SWITCH
CIRCUIT BREAKER

Page 8
FIGURE3
G23(X)HEATEXCHANGEASSEMBLY
-5 and -6G23XModels
FLAME SENSE ASSEMBLY
MANIFOLDAND GAS VALVE
ORIFICE
HEATEXCHANGER
(HeatTrain
Assembly)
CLAMSHELL
(EachSegment)
BURNERASSEMBLY
FLUECOLLECTOR
BOX
FLUE BOX
GLASS FIBERGASKET
ORIFICE PLATE
(FLUETRANSITIONASSEMBLY)
FLUEOUTLET
GLASS FIBERGASKET
UPPERVEST
PANEL
FLAME BAFFLES (NOxUNITSONLY)
RIGHTMANIFOLDBRACKET
ROLLOUTBRACKET
MIDVESTPANEL
PRIMARYLIMIT
PRIMARYLIMIT
ALTERNATE STYLE
MANIFOLDEND PLUG
ROLLOUTSWITCH
LEFT MANIFOLDBRACKET
COMBUSTIONAIRBLOWER
TOPCAP
GLASS FIBER
GASKET
COMBUSTIONBLOWER
GLASS FIBERGASKET
F
I
G
U
R
E
4
CONTROLBOX
(-1through -4G23Xmodels)
BCC CONTROL
TRANSFORMER
DOORINTERLOCK
SWITCH
LOWVOLTAGE STRIP
CIRCUITBREAKER
F
I
G
U
R
E
5
CONTROLBOX
(-5 and -6G23Xmodels))
DOORINTERLOCK
SWITCH TRANSFORMER
LOWVOLTAGE STRIP
CIRCUITBREAKER
SURELIGHTCONTROL

3DJH 
I-UNIT COMPONENTS (Figures 1 and 2)
G23(X)unitcomponentsareshowninfigures1and2.The
gasvalve,ignitioncontrolandburnerscanbeaccessedby
removing the burner access panel. The blower, blower
control and SureLight control can be accessed by remov-
ing the blower access door.
G23(X) units are factory equipped with bottom and side return
air panels in place. The panels are designed to be field re-
moved as required for bottom air return or side air return.
A-Make-Up Box (Figure 6)
Thelinevoltagemake-upboxisshowninfigure6.Thebox
may be installed inside or outside the unit and may be
installed on the unit left or right side (figure 8).
FIGURE 6
MAKE-UP BOX
BOX
COVER
JACK J69
TO BLOWER MULLION
POWER ENTRY KNOCKOUT
120V LINE VOLTAGE
PIGTAIL CONNECTIONS
UNIT
GROUND
Box may be installed inside or outside unit. See Figure 8.
B-Control Box Components (Figures 4 & 5)
SureLight control (A3), Electrical blower control compo-
nents (A15), unit transformer (T1) and 24V circuit breaker
(CB8) are located in the control box. In addition, a door in-
terlockswitch(S51)islocatedinthecontrolbox.Jackplugs
allow the control box to be easily removed for blower ser-
vice.
1. Control Transformer (T1)
A transformer located inthe control box provides power to
the low voltage24volt section of the unit.Transformers on
all models are rated 40VA with a 120Vprimary and a 24V
secondary.
2. Circuit Breaker (CB8)
A24V circuitbreaker isalsolocatedinthecontrolbox.
The switch provides overcurrent protection to the
transformer (T1).Thebreakerisrated3A at32V.Ifthe
currentexceedsthislimitthebreakerwilltripandallunit
operation willshutdown.Thebreakercanbemanually
reset by pressing the button on the face. See figure 7.
FIGURE 7
CIRCUIT BREAKER CB8
PRESS TO RESET
3.Door Interlock Switch (S51)
A door interlock switch rated 14A at 125VAC is located on
the blower access door. The switch is wired in series with
linevoltage.Whentheblowerdooris removed theunit will
shut down.
FIGURE 8
MAKE-UP BOX INSTALLATION
MAKE-UP BOX
MAKE-UP BOX
UNIT
CABINET
Box may be installed inside or outside cabinet and may
be installed on left side or right side of cabinet
JACK J69
PLUG P69
BLOWER MULLION
BLOWER MULLION
OUTSIDE INSTALLATION INSIDE INSTALLATION
Line Voltage Enters Make-Up
Box Through Side Of Unit and
J69 Passes Through Bottom
Knockout in Make-Up Box.
Line Voltage Enters Through
Knockout In Make-Up Box. J69
Passes Through Side Knockout
Into Side Of Unit.
STAR WASHERS
MUST BREAK
PAINT ON UNIT
CABINET FOR
PROPER
GROUND.

3DJH 
4. BCC Blower Control (A15)
-1 Through -4 Models
G23(X)-1, -2, -3 and -4 model units utilize the BCC blower
controlmanufacturedbyHeatcraft.Seefigure10.TheBCC
is a printed circuit board which controls the supply air blow-
er and monitors primary limit and gas valve operation. The
BCC is equipped with a jumper for electronic (isolation
relay) or electro-mechanical thermostat selection.The con-
trolhasanon-adjustable,factorypresetfan“on”timing.Fan
“off” timing is adjustable. The board is divided into two sec-
tions, 120 and 24VAC. Line voltage comes into the board
on the 120VAC side. See table 1 for terminal designations.
Fan Timings
Fan“off”timing (timethatthebloweroperates aftertheheat
demand has been satisfied) is determined by the arrange-
ment of a jumper across pins on the BCC blower control
board.Seefigure9.Toadjustfan“off”timing,gentlydiscon-
nect jumper and reposition across pins corresponding with
newtiming.Fan“on”timeisfactorysetat45seconds andis
not adjustable.
NOTE—If fan “off” time is set too low, residual heat in
heat exchanger may cause primary limit S10 to trip re-
sulting in frequent cycling of blower. If this occurs, ad-
just blower to longer time setting.
Figure 9 shows the various fan “off” timings and how jumper
should be positioned. Unit is shipped with a factory fan “off”
setting of 90 seconds. Fan “off” time will affect comfort and
efficiency and is adjustable to satisfy individual applications.
The fan“off” timing is initiated after aheating demandbut not
after a blower or cooling demand (that is, when indoor ther-
mostat switch is changed from ON to AUTO and heating/
cooling demand is not present, the blower stops immediate-
ly).
FIGURE 9
FAN-OFF TIME ADJUSTMENT
 
 
To adjust fan-off timing:
Remove jumper from BCC and select
one of the other pin combinations to
achieve the desired time.
TIMING
JUMPER
TIMING PINS
(seconds)
Leave jumper off for
330 second fan-off timing.
SHOCK HAZARD. MAKE SURE TO DISCONNECT
POWER BEFORE CHANGING FAN OFF TIMING.
CAUTION
Electrostatic discharge can affect electronic
components. Take precautions during furnace
installation and service to protect the furnace’s
electroniccontrols.Precautionswillhelptoavoid
control exposure to electrostatic discharge by
putting the furnace, the control and the techni-
cian at the same electrostatic potential. Neutral-
ize electrostatic charge by touching hand and all
tools on an unpainted unit surface, such as the
gas valve or blower deck, before performing any
service procedure.
ELECTROSTATIC DISCHARGE (ESD)
Precautions and Procedures
G23(X)-1, -2 ,-3 and -4 MODELS
BLOWER CONTROL - BCC
(A15)
FIGURE 10
NEUTRAL
TERMINALS ACCESSORY
TERMINAL
THERMOSTAT TERMINAL STRIP
(DETACHABLE ON EARLY BOARDS ONLY))
BLOWER TIME
ADJUSTMENT
JUMPER
HEATING
SPEED TAP
TERMINAL
COOLING
SPEED TAP
TERMINAL DUMMY
TERMINALS
CONTINUOUS FAN
TERMINAL
MECH
ELECT
THERMOSTAT JUMPER
(Electronic or Mechanical)
Heat Anticipator Settings
Beginning with the BCC3-2 series, a 3 pin jumper
has been installed on the board next to the remov-
able 24V terminal strip to account for both program-
mable and electromechanical thermostat usage in
the field. For electromechanical thermostat, position
the jumper over the middle and bottom pin labeled
”MECH.” Set the heat anticipator setting to 0.65
amps for Honeywell valves or 0.50 amps for White
Rodgers valves. For programmable (electronic) ther-
mostats, position the jumper over the middle and
top pin labeled ”ELECT.” Set the heat anticipator
setting to 0.1 amps.

3DJH 
TABLE 1
BLOWER CONTROL A15 TERMINAL DESIGNATIONS
Terminal
(Designa-
tion on Wir-
ing
Diagram)
Type Function
YDetachable
or Screw
Strip Cooling Demand
GDetachable
or Screw
Strip Blower Demand
RDetachable
or Screw
Strip 24VAC to Thermostat
WDetachable
or Screw
Strip Heating Demand
TDetachable
or Screw
Strip
24VAC Common
To Indoor Thermostat
IBN (N) 1/4
Spade 120VAC Indoor Blower Common
N1 (N) 1/4
Spade 120VAC Neutral (L2 Line Voltage Neutral)
CABN (N) 1/4 Spade 120VAC Combustion Air Blower
Common
XFMRN (N) 1/4 Spade 120VAC Transformer Common
HSIN (N) 1/4 Spade 120VAC Hot Surface Ignition
Common (Not Used)
CAB 1/4 Spade Switched 120VAC to
Combustion Air Blower
L1 1/4 Spade 120VAC Line Voltage In
A 1/4 Spade Switched 120VAC
to Blower Cooling Tap
XFMR 1/4 Spade 24VAC In From Transformer
D 1/4 Spade Dummy Connection for
Unused Blower Leads
CF 1/4 Spade Switched 120VAC to
Continuous Blower Tap
H 1/4 Spade Switched 120VAC to
Blower Heating Tap
ACC 1/4 Spade Switched 120VAC to Accessory
(Electronic Air Cleaner, Humidifier,
Etc.)
24V
(24) 3/16 or 1/4 Spade 24VAC Input From Transformer
LIMIT
(L) 1/4 Spade
24VAC In From Primary Limit. Limit
Open: Closes Gas Valve and Turns
On Blower Limit Closed: Allows
Ignition
W 1/4 Spade
24VAC Thermostat Demand Output
Through Rollout and Prove Switch
to TH Terminal of Ignition Con-
trol
VALVE
SENSE (V) 3/16 or 1/4 Spade 24VAC Input From Gas Valve
T 1/4 Spade 24VAC Common From
Ignition Control and Gas Valve
COM (C) 1/4 Spade 24VAC Common To Transformer
C-Ignition Control (-1 Through -4 Models)
G23(X) -1, -2, -3 and -4 model units use an intermittent pilot
ignitioncontrolmanufacturedbyJohnsonControls. Theigni-
tion control is located on a bracket on the upper vest panel.
Unit Operation
When there is a call for heat, the control is prevented from
beginning an ignition sequence until the pressure switch
proves combustion air blower operation. When the pressure
switch closes, the control generates a spark and opens the
pilot valve to ignite the pilot. When flame is sensed, the con-
trol opens the main gas valve and the pilot ignites the main
burners. The indoor blower starts after a 45 second delay.
Gas valve remains open and combustion air blower contin-
ues to run until demand stops, flame sensor senses loss of
flame,alimitopensor theproveswitchopens.Ifany ofthese
events occur during a thermostat demand, the gas valve
closes.
Thecontrolwillattemptignitionfor85seconds.Ifignitionis
not successful, the control will lockout (indicated by flash-
ing LED). Within one hour the control will momentarily re-
move then reapply the thermostat signal and the ignition
sequence will begin again (Watchguard circuit). If pilot
ignitionissuccessful,butflameislostwhenthemainvalve
opens,theignitionsequencewillretryupto15moretimes.
Ifignitionisnotsuccessfulafterthe16thtry,thecontrolwill
shut-down and must be reset manually. Manual reset is
accomplished by removing then reapplying thermostat
demand for at least 30 seconds.
FIGURE 11
IGNITION CONTROL A3
SPARK
OUTPUT SEE TABLE 2
FOR TERMINAL
DESIGNATIONS
DANGER
Shock hazard.
Spark related components contain high voltage.
Disconnect power before servicing. Control is
not field repairable. If control is inoperable, sim-
ply replace entire control.
Can cause injury or death. Unsafe operation will
result if repair is attempted.

3DJH 
TABLE 2
IGNITION CONTROL A3 TERMINAL DESIGNATIONS
Terminal Type Function
GROUND 1/4 Spade Cabinet Ground
THS 2 1/4 Spade Safety Limit 24VAC Input
From Rollout and Prove Switch
P.V.1 1/4 or
3/16Spade 24VAC Output to Pilot Operator of Gas Valve
M.V.3 1/4 or 3/16
Spade 24VAC Output to Main Operator of Gas Valve
SENSE 4 1/4 Spade Microamp Flame Sensing Input
Unmarked Pin Type
Bare Wire High Voltage Spark Output
Diagnostic LED
The furnace ignition control is equipped with a diagnostic
LEDusedfortroubleshootingtheunitandthecontrol.LED
functions are shown in table 3.
TABLE 3
Furnace Control A3 Diagnostic LED
LED Stat
eMeaning Remedy
Steady On Normal Opera-
tion ----
Slow Flash
(1 sec. on/
5 sec. off)
Control Retry
Period
Failed to Sense Flame. Ignition
Control Will Retry
Before Locking Out.
Off
Control Failure
or Power Fail-
ure or Hard
Lockout
If Power and Gas Supply are OK,
Try Removing Tstat Demand For
At Least 30 Seconds. If LED Re-
mains Off When Demand Is Re-
turned, Replace Control.
Johnson G776 Ignition Control Operation
The information in this section is protected by a copyright issued by
Johnson Controls, Inc., and is reproduced with permission.
On a call for heat from the indoor thermostat, the ignition
control energizes and the ignition control LED lights
(steady on).Thecombustionairbloweris energized.After
a 15 second pre-purge period, the control simultaneously
opens the pilot valve and sends spark to the pilot elec-
trode.
If the pilot ignites within 85 seconds, the flame sensor de-
tects pilot flame and signals the ignition control to to ener-
gize the main valve. The main valve cannot be energized
until the sensor detects pilot flame. Spark continues until
pilotflameissensedor 85secondshaselapsed,whichev-
er happens first.
When pilot flame is sensed, the main valve is energized
and the spark turns off. The ignition control remains in
“run” mode until the indoor thermostat is satisfied or flame
is lost.
Ifpilotflameisnotsensedbeforetheend ofthe85second
trial for ignition, thecontrol enters the 100% shutoff mode.
The spark circuit and pilot valve de-energize and the igni-
tion control automatically begins the 60 minute retry delay
period. During the 60 minute delay the diagnostic LED
continually flashes on for one second and off for five se-
conds. After the delay period, another trial for ignition se-
quence starts, beginning with pre-purge.
Ifpilotflamegoesoutwhiletheindoorthermostatis calling
for heat, both mainand pilot valves de-energize within 0.8
seconds and remain de-energized for five seconds. After
this delay, the spark and pilot valve energize until flame is
sensedorthe85secondtrialforignitionperiodends.Ifthis
“flameout” cycle repeats 16 times (pilot flame is estab-
lished and then lost), the control locks out and the LED
goes off. A new trial for ignition sequence begins after the
thermostat contacts are opened for 30 seconds and then
closed.
If flame is detected when the thermostat calls for heat, it
must extinguish within 30 seconds for normal operation.If
flameisstillpresentafter30seconds,thecontrolgoesinto
lockout and the LED goes off.
D-Combustion Air Blower (B6)
All G23(X) units use a combustion air blower to move air
through the burners and heat exchanger during heating op-
eration. The blower uses a shaded pole 120VAC motor.
Shaded pole motors do not use run capacitors. The motor
operates during all heating operation and is controlled by
blower control A15. The blower operates continuously while
there is a call for heat. The ignition control is prevented from
proceeding through the ignition sequence until combustion
air blower operation is sensed by the prove switch.
The pressure switch connected to the upper vest panel is
used to prove combustion air blower operation. The switch
monitors air pressure in the blower housing. During normal
operation, the pressure in the housing is negative. If the
pressure drops (becomes more positive), the pressure
switch opens. When the pressure switch opens, the ignition
control (A3) immediately closes the gas valve to prevent
burner operation.

3DJH 
FIGURE 12
G23(X) UPPER VEST PANEL
FLUE COLLECTOR BOX
FLUE BOX
GLASS FIBER GASKET
ORIFICE PLATE
(FLUE TRANSITION ASSEMBLY)
UPPER VEST
PANEL
IGNITION CONTROL
BRACKET
COMBUSTION AIR BLOWER
FLUE OUT-
LET
GLASS FIBER
GASKET
COMBUSTION AIR BLOWER MOTOR
IGNITION CONTROL
(-1 through -4 model units)
COMBUSTION AIR BLOWER
PROVE (PRESSURE)
SWITCH
COMBUSTION AIR BLOWER
GLASS FIBER GASKET
NOTE-ALL components located behind up-
per vest panel including combustion air blow-
er are exposed to supply air stream.
E-Blower Motors and Capacitors
All G23(X) units use direct drive blower motors. All motors
used are 120V permanent split capacitor motors to ensure
maximum efficiency. See table 4 for ratings.
TABLE 4
G23(X) BLOWER RATINGS 120V 1PH
BLOWER MOTOR HP
G23Q2/3(X)
G23Q3(X)
CAP
1/3 5MFD 370V
G23Q5/6(X)
G23Q4/5(X) 3/4 40MFD 370V
3/4 40MFD 370V
1/3 5MFD 370V
G23Q2(X) 1/5 5MFD 370V
G23Q3/4(X)
1/2
7MF 370V
F-Flame Rollout Switch (S47)
Flame rollout switch is a high temperature limit located on
rollout switch bracket (over burner assembly). The limit is a
N.C. SPST manual-reset limit connected in series with the
ignition control (A3). When S47 senses rollout, the ignition
controlimmediatelystops ignitionandcloses thegasvalve.
If unit is running andflame rollout is detected, the gas valve
will close and ignition control will be disabled. Rollout can
be caused by a reverse draft, blocked flue or lack of com-
bustion air. The switch is factory set and cannot be ad-
justed. The switch may have different setpoints for each
unitmodelnumber.However, the setpointwillbeprinted on
the side of the limit. The switch can be manually reset. To
manually reset a tripped switch, push the reset button lo-
cated on the control (see figure 13).
FIGURE 13
ROLLOUT SWITCH (S47)
MANUAL
RESET BUTTON
G-Primary Limit Control (S10)
Primary limit (S10) on G23(X) units is located in the middle of
the vestibule panel. When excess heat is sensed in the heat
exchanger, the limit will open. If the limit is tripped, the furnace
control energizes the supply air blower and closes the gas
valve. The limit automatically resets when temperature re-
turns to normal. The switch is factory set and cannot be ad-
justed. The switch may have different setpoints for each
unitmodelnumber.However,thesetpoint will beprintedon
the side of the limit.
FIGURE 14
INSULATING COVER (s)
LIMIT CONTROL (S10) FOR
G23(X) SERIES UNITS AND ALTERNATE STYLE
SPADE CONNECTORS
LIMIT
Units may be equipped with
either style limit.

Page 14
Unitsmaybe equipped with eitherflushstyle orextended
(masted)limit(figure14).Masted limitsmaybe installed
withlimit facing blowerorawayfromblower.Thisorienta-
tioncannotbechanged.Whenremovinglimitfromunit,pay
carefulattention toitsorientation and makesurelimitisre-
installed facing same direction.
H-Pilot,SparkElectrode,FlameSensor
and Burners(-1Through -4Models)
Figure17showsthe arrangementofpilot, flamesensor,
sparkelectrode and burners.The ignition controlusesdi-
rectsparktoignitethe pilot. The pilotignitesthe burners
and the burners cross-light. The flamesensorusesflame
rectification tosenseignition.The ignition controlrequires
thatpilot flamemustbe sensed beforethe main gas valve
isallowed to open.Typically,a2to 4 second delayoccurs
between the pilotignition and the mainvalve opening.
Figure16showsthe gap between tip of the electrodesand
the burnersurface.Itisimportant that the gap be main-
tained forconsistentignition ofpilot flame.
Aflameretention ring inthe end ofeach burnerisused to
maintaincorrect flamelength and shape and tokeep the
flamefromlifting offthe burnerhead. In addition, the burn-
erentranceto eachclamshell (Figure 3)isfitted with a
flamebaffleorcorbelto enhancethecombustionprocess.
FIGURE15
TYPICALBURNER ASSEMBLY
FIGURE16
PILOT,SPARK ELECTRODEAND FLAME SENSOR
1/8(.125)Inch+”1/32 (.031)
SPARK ELECTRODE
FLAME SENSOR
PILOT
PILOTHOODGAP
SPARKWIRE
SENSE WIRE
FIGURE17
G23(X)-1,-2,-3AND -4MODELSBURNERPILOT/ELECTRODE
ORIENTATION
viewlooking atsideofburners
ORIFICE
RETAINERPRIMARY AIRINLETBURNERPILOTMOUNTING
BRACKET
FLAME SENSOR
SPARK
ELECTRODE
PILOTHOOD

3DJH 
127(   7KH *; IXUQDFH FRQWDLQ V HOHFWURQLF FRP
SRQHQWV WKDW DUH SRODULW\ VHQVLWLYH 0DNH VXUH WKDW WKH
IXUQDFH LV ZLUHG FRUUHFWO\ DQG LV SURSHUO\ JURXQGHG
DANGER
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 is attempted.
I- SureLight Ignition System A3
(-5 and -6 models)
All G23(X)-5 and -6 model units are equipped with the
Lennox SureLight ignition system. The system consists
of ignition control board (figure 21 with control terminal
designationsintable5)andignitor(figures18,19and20.
The board and ignitor work in combination to ensure fur-
nace ignition and ignitor durability. The SureLight inte-
grated board controls all major furnace operations. The
board also features two LED lights for troubleshooting
and two accessory terminals rated at (4) four amps. See
table 6 for troubleshooting diagnostic codes. Table 7 and
8 show jack plug terminal designations. Units equipped
withtheSureLightboardcanbeusedwitheitherelectron-
ic or electro-mechanical thermostats without modifica-
tion. The SureLight ignitor is made of durable silicon-ni-
tride. Ignitor longevity is also enhanced by voltage ramp-
ing by the control board. The board finds the lowest igni-
tor temperature which will successfully light the burner,
thus increasing the life of the ignitor.
)ODPH 6HQVRU
Aflamesensorislocatedontheleftsideoftheburnersup-
port. Seefigures18,19and20.Thesensorismountedon
a bracket in the burner support and the tip protrudes into
the flame envelope of the left-most burner. The sensor is
fastened to burner supports and can be removed for ser-
vice without removing any part of the burners. During op-
eration, flame is sensed by current passed through the
flameandsensingelectrode.TheSureLightcontrolallows
the gas valve to remain open as long as flame signal is
sensed.
FIGURE 18
NORMAL FLAME SIGNAL  0.7 MICROAMPS
LOW FLAME SIGNAL $ 0.7 MICROAMPS
MINIMUM FLAME SIGNAL $ 0.15 MICROAMPS
3/8”
1/4”
19/64”
SENSOR
IGNITOR
FIGURE 19
IGNITOR
SENSOR
NOTE - Do not remove blower access panel to read
SureLight LED lights. A sight glass is provided on
the access panel for viewing.
FIGURE 20
SURELIGHT IGNITOR (I) AND SENSOR (S)
LOCATION

Page 16
SURELIGHTCONTROLBOARD
FIGURE21
SURELIGHTCONTROL TERMINALDESIGNATIONS
ACBCOOL
ACBHEAT
PARK
ACBLOW
ACC
TX
HOT
HTGACC
NEUTRALS
24VAC HOT
24VAC RTN
FLAME SENSE
Blower - Cooling Speed (Line Volt)
Blower - Heating Speed (Line Volt)
AlternateBlowerSpeeds(Dead)
ContinuousLowSpeed Blower
AccessoryTerminal(Line Volt)
120VAC Hot toTransformer
120VAC Hot Input
HeatOnlyAccessory(Line Volt)
120VAC Neutrals
24VAC Hot fromTransformer
24VAC ReturnfromTransformer
FlameSenseTerminal
TABLE5
TABLE6
DIAGNOSTIC CODES
MAKE SURETO IDLED’SCORRECTLY:REFERTO INSTALLATIONINSTRUCTIONSFOR CONTROLBOARD LAYOUT.
LED#1 LED#2 DESCRIPTION
SIMULTANEOUS
SLOWFLASHSIMULTANEOUS SLOWFLASHPower - Normaloperation
Alsosignaled during cooling and continuesfan.
SIMULTANEOUSFAST
FLASHSIMULTANEOUSFAST FLASHNormaloperation -signaled when heating demand initiated at thermostat.
SLOWFLASHON
PrimaryorSecondarylimitopen.Unitswith board 63K8901 or24L85:Limitmust
closewithin5trialsforignition orboard goesinto one hourlimitWatchguard.
Unitswith board 56L83 or97L48:Limitmustclosewithin3minutesorboard
goesinto one hourlimitWatchguard.
OFF SLOWFLASHPressureswitch open orhasopened 5 timesduringasinglecall forheat; OR:
Blocked inlet/exhaustvent; OR:Condensateline blocked;OR:Pressureswitch
closed priorto activation ofcombustion airblower.
ALTERNATINGSLOW
FLASHALTERNATINGSLOW FLASHWatchguard-burnersfail toignite.
SLOWFLASHOFF Flamesensed withoutgas valve energized.
ONSLOWFLASHRolloutswitch open.OR:9 pinconnectorimproperlyattached.
ON
ON
OFF
ON
OFF
ONCircuitboardfailure orcontrolwired incorrectly.
FAST FLASHSLOWFLASHMain powerpolarityreversed.Switchline and neutral.
SLOWFLASHFAST FLASHLowflamesignal.Measuresbelow.7microAmps.Replaceflamesenserod.
ALTERNATINGFAST
FLASHALTERNATINGFAST FLASHImpropermain ground orline voltage below75 volts;OR:Broken ignitor;OR:
Open ignitorcircuit.
NOTE-Slowflash equals1Hz(one flash persecond).Fast flash equals3Hz(three flashespersecond).Drop out flamesensecurrent<0.15 microAmps

Page 17
TABLE7
SureLightBOARD J156 (J2)TERMINAL
DESIGNATIONS
PIN#FUNCTION
1Ignitor
2NotUsed
3IgnitorNeutral
4Combustion AirBlowerLine Voltage
5NotUsed
6Combustion AirBlowerNeutral
TABLE8
SureLightBOARD J58 (J1)TERMINAL
DESIGNATIONS
PIN#FUNCTION
1PrimaryLimit In
2GasValveCommon
3Roll OutSwitchOut
4GasValve 24V
5PressureSwitchIn
6PressureSwitch and PrimaryLimitOut
7NotUsed
8Roll OutSwitchIn
9Ground
CAUTION
Electrostaticdischarge canaffectelectronic
components.Take precautionsduring furnace
installation and service to protect thefurnace’s
electronic controls.Precautionswill helpto
avoidcontrolexposuretoelectrostaticdis-
chargebyputting thefurnace,the controland
thetechnicianat the same electrostaticpoten-
tial. Neutralize electrostatic chargebytouching
hand and all toolson an unpainted unitsurface,
suchas thegas valve orblowerdeck,beforeper-
forming any service procedure.
ELECTROSTATIC DISCHARGE(ESD)
Precautions and Procedures
a-ElectronicIgnition
Onacall forheat the SureLightcontrolmonitorsthe com-
bustionairblowerpressureswitch.The controlwill notbe-
ginthe heating cycleif the pressureswitchis closed (by-
passed).Oncethe pressureswitchisdetermined to be
open, the combustion airblowerisenergized.When the
differential inthe pressureswitchisgreatenough, the
pressureswitchclosesand a 15-second pre-purge be-
gins. If the pressureswitchisnotproven within 2-1/2min-
utes, the controlgoesintoWatchguard-PressureSwitch
mode fora 5-minutere-setperiod.
Afterthe 15-second pre-purge period, the SureLightigni-
torwarmsup for20 secondsafterwhichthe gas valve
opensfora 4-second trialforignition.G23Xunits
equipped with board 24L85,56L83 or63K89: the ignitor
stays energized forthe firstsecond of the 4-second trial.
Unitsequipped with board 97L48:ignitorstays energized
duringthetrialuntilflameissensed.Ifignitionisnotproved
during the 4-second period, the controlwill tryfourmore
timeswithaninterpurge and warm-up time between trials
of35 seconds.Afteratotalof fivetrialsforignition (includ-
ing the initialtrial), the controlgoesintoWatchguard-
FlameFailuremode.Aftera 60-minuteresetperiod, the
controlwill beginthe ignition sequence again.
The SureLightcontrolboard hasan added featurethat
prolongsthe life of the ignitor.Afterasuccessful ignition,
theSureLightcontrolutilizeslesspowertoenergizetheig-
nitoronsuccessivecallsforheat.The controlcontinuesto
rampdownthevoltage totheignitoruntilit findsthelowest
amountofpowerthatwill provideasuccessful ignition. It
findsthisbyramping down until the ignitorwill notlight,
then stepsup the amountofpowerbythree times.This
amountofpowerisused for255 cycles.Onthe 256thcall
forheat, the controlwill againramp down until the lowest
powerisdetermined and the cycle beginsagain.
b-Fan TimeControl
The fan on time of45 secondsisnotadjustable.Fan off
time(timethat the bloweroperatesafterthe heatdemand
hasbeen satisfied)can be adjusted byflipping the dip
switcheslocated on the SureLightintegrated control.The
unitis shipped withafactoryfan off setting of90 seconds.
Fan off timewill affectcomfortand isadjustabletosatisfy
individualapplications.See figure 22.
FIGURE22
FAN-OFF TIMEADJUSTMENT
To adjust fan-off timing, flip dipswitchto desired setting.
60sec.90sec.120sec.180sec.

3DJH 
J-Gas Valve
TheG23(X) usesa gasvalvemanufacturedbyHoneywell
or White Rodgers. See figure 23. The valve is internally
redundant to assure safety shut-off. If the gas valve must
be replaced, the same type valve must be used.
24VAC terminals and gas control knob are located on top of
the valve. All terminals on the gas valve are connected to
wires from the ignition control. 24V applied to the “PV” termi-
nals opens the pilot (-1 through -4 models) and 24V applied to
the “MV” terminals opens the valve on G23X. Inlet and outlet
pressure taps are located on the valve. A regulator adjust-
ment screw (figure 24) is located on the valve.
An LPG changeover kit is available from Lennox. The kit in-
cludes main and pilot burner orifices, burner corbel plate (Nox
only), and regulator conversion kit.
K-Combustion Air Blower Prove
(Pressure) Switch (S64)
G23(X) series units are equipped with a combustion air
(pressure) switch located on the vestibule panel. The switch
is connected to the combustion air blowerhousing by means
of a flexible silicon hose. It monitors air pressure in the com-
bustion air blower housing. The other side of the pressure
switch is open to atmosphere.
The switch is a single-pole single-throw pressure switch
electrically connectedinserieswiththeignitioncontrol.The
purpose of the switch is to prevent burner operation if the
combustion air blower is not operating.
On start-up, the switch senses that the combustion air blow-
er is operating. It closes a circuit to the ignition control when
pressure inside the combustion air blower increases above
the setpoint. The setpoint is measured in negative inches
water gauge. The pressure sensed by the switch is relative
to atmospheric pressure. If the flue becomes obstructed dur-
ing operation, the switch senses a loss of negative pressure
(drops below setpoint) and opens the circuit to the ignition
control.
The switch setpoint varies with unit model number. Look
for the setpoint printed on the side of the switch.
The switch is factory set and is not field adjustable. It is a
safety shut-down control in the furnace and must not be
bypassed for any reason.
FIGURE 23
21
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HONEYWELL VR8204 SERIES GAS VALVE
GAS VALVE SHOWN IN OFF POSITION
WHITE RODGERS
36E GAS VA LVE
GAS VALVE
SHOWN
IN OFF
POSITION
INLET
INLET
FIGURE 24
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HONEYWELL VR8204 GAS VALVE
REGULATOR ADJUSTMENT SCREW LOCATION
WHITE RODGERS 36E GAS VALVE
REGULATOR ADJUSTMENT SCREW LOCATION

3DJH 
II-PLACEMENT AND INSTALLATION
Make sure unit is installed in accordance with installation
instructions and applicable codes.
A-Fresh Air Requirements
Until recently, there was no problem in bringing in sufficient
amounts of outdoor air for combustion -- infiltration provided
all the air that was needed and then some. In today’s homes
built with energy conservation in mind, tight construction prac-
tices make it necessary to bring in air from outside for com-
bustion. Consideration must also be given to the use of ex-
haust fans, appliance vents, chimneys and fireplaces be-
cause they draw additional air that could beused for combus-
tion out of the house. Unless outside air is brought into the
home for combustion, negative pressure (pressure outside is
greater than inside pressure) will build to the point that a down
draft can occur in the furnace vent pipe or chimney. Combus-
tion gases can enter the living space creating a potentially
dangerous situation.
Theimportanceofthepreviousparagraphcannotbeover-
stated. Users may inadvertently block fresh air intakes af-
ter installation.
In the absence of local codes concerning air for combustion
and ventilation, the following section outlines guidelines and
recommends procedures for operating G23(X) furnaces in a
manner that ensures efficient and safe operation. Special
consideration must be given to combustion air needs as well
as requirements for exhaust vents and gas piping. A portion
of this information has been reprinted with permission from
the National Fuel Gas Code (ANSI-Z223.1). This reprinted
material is not the complete and official position of the ANSI
on the referenced subject, which is represented only by the
standard in its entirety.
In Canada, refer to the standard CAN/CGA-B149.1 and -
B149.2 installation codes.
Combustion Air Requirements
&$87,21
Insufficient combustion air can cause headaches,
nausea, dizziness or asphyxiation. Excessive ex-
posure to contaminated combustion airwill result
in safety and performance related problems.
Avoid exposureto the following substances in the
combustion air supply:
Permanent wave solutions;
Chlorinated waxes and cleaners;
Chlorine base swimming pool chemicals;
Water softening chemicals;
De-icing salts or chemicals;
Carbon tetrachloride;
Halogen type refrigerants;
Cleaning solvents (such as perchloroethylene);
Printing inks, paint removers, varnishes, etc.;
Hydrochloric acid;
Cements and glues;
Antistatic fabric softeners for clothes dryers; and
Masonry acid washing materials.
All gas-fired appliances require air to be used for the com-
bustion process. If sufficient amounts of combustion air are
not available, the furnace or other appliance will operate in
an inefficient and unsafe manner. Enough air must be pro-
vided to meet the needs of all fuel-burning appliances, as
well as appliances such as exhaust fans which force air out
of the home. When fireplaces, exhaust fans, or clothes dry-
ers are used at the same time as the furnace, much more air
is required to ensure proper combustion and to prevent a
down-draft situation. Insufficient amounts of air also cause
incomplete combustion which can result in carbon monox-
ide. The requirements for providing air for combustion and
ventilation depend largely onwhether the furnace is installed
in an unconfined or confined space.
Unconfined Space
An unconfined space is an area such as a basement or
largeequipmentroomwithavolumegreaterthan50cubic
feet per 1,000Btu per hour of the combined input rating of
all appliances installed in that space. This space also in-
cludes adjacent rooms which arenot separated by adoor.
Though an area may appearto be unconfined, it might be
necessary to bring in outdoor air for combustion if the
structure does not provide enough air by infiltration. If the
furnace is located in a building of tight construction with
weather stripping and caulking around the windows and
doors,followtheproceduresoutlinedfor usingairfromthe
outside for combustion and ventilation.
Confined Space
A confined space is an area with volume less than 50 cubic
feet per 1,000Btu per hour of the combinedinput rating ofall
appliances installed in that space. This definition includes
furnace closets or small equipment rooms.

3DJH 
Whenthefurnaceisinstalledsothatsupplyductscarryair
circulated by the furnace to areas outside the space con-
tainingthefurnace,thereturnairmustbehandledbyducts
which are sealed to the furnace casing and which termi-
nate outside the space containing the furnace. This is es-
pecially important when the furnace is mounted on a plat-
form in a confined space such as a closet or small equip-
ment room. Even a small leak around the base of the unit
at the platform or at the return air duct connection can
cause a potentially dangerous negative pressure condi-
tion.Airforcombustionandventilationcanbebroughtinto
the confined space either from inside the building or from
outside.
Air from Inside
If the confined space housing the furnace adjoins space
categorizedasunconfined,aircanbebroughtinbyprovid-
ing two permanent openings between the two spaces.
Eachopeningmusthaveaminimumfreeareaof 1square
inch per 1,000 Btu per hour of the total input rating of all
gas-fired equipment in the confined space. Each opening
must be at least 100 square inches. One opening shall be
within 12 inches of the top ofthe enclosure and one open-
ing within 12 inches of the bottom (See figure 25).
EQUIPMENT IN CONFINED SPACE
ALL AIR FROM INSIDE
FIGURE 25
NOTE-Each opening shall have a free area of at least one square
inch per 1,000 Btu per hour of the total input rating of all equip-
ment in the enclosure, but not less than 100 square inches.
CHIMNEY OR
GAS VENT
WATER
HEATER
OPENINGS
(To Adjacent
Room)
G23(X)
FURNACE
Air from Outside
If air fromoutside is brought infor combustion and ventila-
tion,theconfinedspaceshallbeprovidedwithtwoperma-
nent openings. One opening shall be within 12 inches of
the top of the enclosure and one within 12 inches of the
bottom. These openings must communicate directly or by
ductswiththeoutdoorsorspaces(crawlorattic)thatfreely
communicate with the outdoors or indirectly through verti-
calducts.Eachopeningshallhaveaminimumfreeareaof
1squareinchper 4,000Btu perhourof totalinput ratingof
all equipment in the enclosure (See figures 26 and 27).
When communicating with the outdoors through horizon-
tal ducts, each openingshall have a minimumfree area of
1 square inch per 2,000 Btu per total input rating of all
equipment in the enclosure (See figure 28).
EQUIPMENT IN CONFINED SPACE
ALL AIR FROM OUTSIDE
(Inlet Air from Crawl Space and
Outlet Air to Ventilated Attic)
NOTE-The inlet and outlet air openings shall each have a free
area of at least one square inch per 4,000 Btu per hour of the
total input rating of all equipment in the enclosure.
VENTILATION LOUVERS
(Each end of attic)
OUTLET
AIR WATER
HEATER
INLET
AIR
CHIMNEY
OR GAS
VENT
VENTILATION
LOUVERS
(For unheated
crawl space)
FIGURE 26
G23
FURNACE
EQUIPMENT IN CONFINED SPACE
ALL AIR FROM OUTSIDE
(All Air Through Ventilated Attic)
NOTE-The inlet and outlet air openings shall each have a free
area of at least one square inch per 4,000 Btu per hour of the
total input rating of all equipment in the enclosure.
CHIMNEY
OR GAS
VENT
WATER
HEATER
OUTLET
AIR
VENTILATION LOUVERS
(Each end of attic)
INLET AIR
(Ends 12 above
bottom)
FIGURE 27
G23(X)
FURNACE