Lennox G40UHX Series Installation and operation manual

Page 1 ©2000 Lennox Industries Inc.
G40UH(X)
Service Literature
Corp. 0006−L3
Revised 09−2006
G40UH(X) series units are mid−efficiency gas furnaces
used for upflow or horizontal applications only, manufac-
tured with Lennox Duralok Plus heat exchangers formed of
aluminized steel. G40UH(X) units are available in heating
capacities of 44,000 to 154,000 Btuh and cooling applica-
tions up to 5 tons. Refer to Engineering Handbook for prop-
er sizing.
Units are factory equipped for use with natural gas. Kits are
available for conversion to LPG operation. G40UH(X) model
units are equipped with a hot surface ignition system. The
G40UH(X) unit meets the California Nitrogen Oxides (NOx)
Standards and California Seasonal Efficiency requirements.
All units use a redundant gas valve to assure safety shut−off
as required by C.S.A.
All specifications in this manual are subject to change. Pro-
cedures outlined in this manual are presented as a recom-
mendation only and do not supersede or replace local or
state codes. In the absence of local or state codes, the
guidelines and procedures outlined in this manual (except
where noted) are recommended only and do not constitute
code.
TABLE OF CONTENTS
Specifications Page 2. . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Blower Data Page 4. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
High Altitude Page 13. . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Parts Identification Page 14. . . . . . . . . . . . . . . . . . . . . . . .
I Unit Components Page 16. . . . . . . . . . . . . . . . . . . . . . .
II Installation Page 24. . . . . . . . . . . . . . . . . . . . . . . . . . . . .
III Start Up Page 24. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
IV Heating System Service Checks Page 24. . . . . . . . .
V Typical Operating Characteristics Page 28. . . . . . . . .
VI Maintenance Page 28. . . . . . . . . . . . . . . . . . . . . . . . . .
VII Wiring and Sequence of Operation Page 30. . . . . .
VIII SureLight Troubleshooting Guide Page 41. . . . . . .
IMPORTANT
Improper installation, adjustment, alteration, service
or maintenance can cause property damage, person-
al injury or loss of life. Installation and service must
be performed by a qualified installer, service agency
or the gas supplier.
WARNING
Electric shock hazard. Can cause injury
or death. Before attempting to perform
any service or maintenance, turn the
electrical power to unit OFF at discon-
nect switch(es). Unit may have multiple
power supplies.
WARNING
Sharp edges.
Be careful when servicing unit to avoid sharp edges
which may result in personal injury.

Page 2
SPECIFICATIONS
ModelNo. G40UH
−24A−045
G40UH
−36A−045
1G40UH
−24A−070
G40UH
−36A−070
G40UH
−48B−070
G40UH
−36B−090
G40UH
−48B−090
Low NOxModel No. −24A−045X − − − − − − −36A−070X − − − − − − −48B−090X
Gas
Heating
Input− Btuh 44,000 44,000 66,000 66,000 66,000 88,000 88,000
Heating
Performance Output− Btuh 36,000 35,900 54,100 54,100 54,000 72,100 72,100
2AFUE 80.0% 80.0% 80.0% 80.0% 80.0% 80.0% 80.0%
Highstatic(CSA)− in.w.g. .50 .50 .50 .50 .50 .50 .50
Temperature rise range − _F 35 − 65 25 − 55 40 − 70 40 − 70 25 − 55 40 − 70 40 − 70
Connections Flue − in. (round) 4 4 4 4 4 4 4
GaspipesizeIPS− in. 1/2 1/2 1/2 1/2 1/2 1/2 1/2
Indoor
Blower
Wheelnom.dia. xwidth −in. 10 x 7 10 x 8 10 x 7 10 x 8 10 x 10 10 x 8 10 x 10
Blower
Motoroutput − hp 1/5 1/3 1/5 1/3 1/2 1/3 1/2
Tons ofadd-oncooling 1.5 − 2 2 − 3 1.5 − 2 2 − 3 2 − 4 2 − 3 3 − 4
ShippingData lbs. − 1 package 121 126 127 132 139 146 153
Electricalcharacteristics 120 volts − 60 hertz − 1 phase (less than 12 amps)
Gas
Heating
Pf
ModelNo. 1G40UH
−36C−110
G40UH
−48C−110
G40UH
−60C−110
G40UH
−48C−135
G40UH
−60D−135
G40UH
−60D−155
g
Performance Low NOxModel No. − − − − − − −60C−110X − − − − − − − − −
Input− Btuh 110,000 110,000 110,000 132,000 132,000 154,000
Output− Btuh 90,200 88,500 89,400 106,900 106,900 124,700
2AFUE 80.0% 80.0% 80.0% 80.0% 80.0% 80.0%
Highstatic(CSA)− in.w.g. .50 .50 .50 .50 .50 .50
Temperature rise range − _F 50 − 80 40 − 70 30 − 60 50 − 80 45 − 75 50 − 80
Connections Flue − in. (round) 4 4 4 343434
GaspipesizeIPS− in. 1/2 1/2 1/2 1/2 1/2 1/2
Indoor
Blower
Wheelnom.dia. xwidth −in. 10 x 8 10 x 10 11−1/2 x 10 10 x 10 11−1/2 x 10 11−1/2 x 10
Blower
Motoroutput − hp 1/3 1/2 1 1/2 1 1
Tons ofadd-oncooling 2 − 3 3 − 4 4 − 5 2.5 − 4 4 − 5 4 − 5
ShippingData lbs. − 1 package 166 169 175 178 195 204
Electricalcharacteristics 120 volts − 60 hertz − 1 phase (less than 12 amps)
NOTE − Filters and provisions for mounting are not furnished and must be field provided.
1Canada Only
2Annual Fuel Utilization Efficiency based on DOE test procedures and according to FTC labeling regulations. Isolated combustion system rating for non-weatherized furnaces.
3Flue connection on the unit is 4 in. diameter. Most applications will require 5 in. venting and field supplied 4 x 5 in. adaptor. See Venting Tables in the Installation Instructions for
detailed information.

Page 3
SPECIFICATIONS
ModelNo. G40UH−60C−110
−1, −2, −3 units
G40UH−60D−135
−1, −2, −3 units
G40UH−60D−155
−1, −2, −3 units
Gas
Heating
Input− Btuh (kW) 110,000 (32.2) 132,000 (38.7) 154,000 (45.1)
Heating
Performance Output− Btuh (kW) 90,200 (26.4) 106,900 (31.3) 124,700 (36.5)
lAFUE 80.0% 80.0% 80.0%
California Seasonal Efficiency 75.7% 75.0% 75.6%
Highstatic(AGA/CGA)− in.w.g. (Pa) .50 (124) .50 (124) .50 (124)
Flue connection − in. (mm) round 4 (102) 4 (102) 4 (102)
GaspipesizeIPS− in. (mm) 1/2 (12.7) 1/2 (12.7) 1/2 (12.7)
Temperature rise range − _F (_C) 35 − 65 (19 − 36) 45 − 75 (25 − 42) 50 − 80 (28 − 44)
Indoor
Blower
Wheelnominaldiameter xwidth −in. (mm) 11−1/2 x 10 (292 x 254) 11−1/2 x 10 (292 x 254) 11−1/2 x 10 (292 x 254)
Blower Motoroutput − hp (W) 3/4 (560) 3/4 (560) 3/4 (560)
Tons(kW) ofadd-oncooling 5 (17.6) 5 (17.6) 5 (17.6)
Shippingweight − 1 package 172 lbs. (78 kg) 192 lbs. (87 kg) 201 lbs. (91 kg)
Matching Coils
Up−flow cased
C33−36C−2F,
C33−48C−2F,
C33−50/60C−2F,
C33−60D−2F, C33−62D−2F
Horizontal
CH33−36C−2F,
CH33−48C−2F,
CH33−50/60C−2F
CH33−60D−2F, CH33−62D−2F
Electricalcharacteristics 120 volts − 60 hertz − 1 phase (less than 12 amps)
OPTIONAL ACCESSORIES − MUST BE ORDERED EXTRA
A" Width Models B" Width Models C" Width Models D" Width Models
FILTER KITS
1Air Filter
and Rack Kit
Horizontal
(end)
Catalog No. 87L95 87L96 87L97 87L98
and Rack Kit (end) Size of filter −
in.
14 x 25 x 1 18 x 25 x 1 20 x 25 x 1 25x25 x 1
Side Return Single 44J22 44J22 44J22 44J22
Ten Pack 66K63 66K63 66K63 66K63
Size of filter − in. 16 x 25 x 1 16 x 25 x 1 16 x 25 x 1 16 x 25 x 1
EZ Filter
Base
Catalog No. − Ship. Wt. − lbs. 73P55 − 7 73P56 − 7 73P57 − 8 73P58 − 10
Base
Up−Flow
Only Size of field provided filter − in. 14 x 25 x 1 16 x 25 x 1 20 x 25 x 1 24 x 24 x 1
CABINET ACCESSORIES
Horizontal Support Frame Kit − Horizontal
Only
56J18 56J18 56J18 56J18
Return Air Base − Up−Flow Only − − − 98M60 98M58 98M59
CONTROLS
Twinning Kit 15L38 15L38 15L38 15L38
VENTING
Vent Adaptor − 6 in. connection size
up−flow applications only
18M79 18M79 18M79 18M79
LPG/Propane Kits See Page 13
1Cleanable polyurethane frame type filter.

Page 4
BLOWER DATA
G40UH−24A−045 PERFORMANCE
External Static Air Volume / Watts at Various Blower Speeds
External
Static
Pressure High Medium Low
in. w.g. Pa cfm L/s Watts cfm L/s Watts cfm L/s Watts
0.00 0 1090 515 460 905 425 390 725 340 300
0.05 12 1080 510 450 900 425 390 720 340 300
0.10 25 1065 505 445 895 420 385 710 335 295
0.15 37 1050 495 435 895 420 380 700 330 290
0.20 50 1030 485 425 890 420 375 690 325 290
0.25 62 1015 480 415 875 415 370 680 320 285
0.30 75 995 470 410 860 405 365 665 315 280
0.40 100 960 455 395 840 395 350 650 305 270
0.50 125 910 430 380 795 375 335 610 290 260
0.60 150 840 395 355 750 355 315 540 255 245
0.70 175 770 365 340 665 315 295 490 230 235
0.80 200 660 310 315 555 260 275 420 200 225
0.90 225 560 265 295 480 225 260 355 170 210
NOTE − All air data is measured external to unit with 1 in. (25 mm) cleanable filter (not furnished − field provided) in place. Also see Filter Air Resistance table.
G40UH−24A−070 PERFORMANCE
External Static Air Volume / Watts at Various Blower Speeds
External
Static
Pressure High Medium Low
in. w.g. Pa cfm L/s Watts cfm L/s Watts cfm L/s Watts
0.00 0 1075 505 445 905 425 375 730 345 290
0.05 12 1070 505 445 900 425 375 725 340 290
0.10 25 1065 505 440 895 420 370 720 340 285
0.15 37 1060 500 435 890 420 365 715 335 285
0.20 50 1055 500 430 885 420 360 710 335 280
0.25 62 1045 495 425 880 415 360 700 330 280
0.30 75 1030 485 415 875 415 355 690 325 270
0.40 100 1010 475 400 860 405 350 675 320 270
0.50 125 975 460 390 840 395 340 660 310 265
0.60 150 940 445 375 805 380 325 640 300 255
0.70 175 890 420 360 755 355 305 605 285 240
0.80 200 830 390 340 700 330 285 565 265 225
0.90 225 765 360 305 640 300 265 515 245 205
NOTE − All air data is measured external to unit with 1 in. (25 mm) cleanable filter (not furnished − field provided) in place. Also see Filter Air Resistance table.

Page 5
BLOWER DATA
G40UH−36A−045 PERFORMANCE
External Static Air Volume / Watts at Various Blower Speeds
External
Static
Pressure High Medium−High Medium−Low Low
in. w.g. cfm Watts cfm Watts cfm Watts cfm Watts
0.00 1480 615 1300 545 1100 460 930 385
0.05 1465 605 1290 530 1100 450 930 380
0.10 1445 585 1280 520 1100 445 930 370
0.15 1440 585 1275 505 1095 435 935 365
0.20 1415 570 1260 495 1090 425 935 360
0.25 1400 560 1250 485 1090 420 930 355
0.30 1375 545 1235 470 1075 410 930 350
0.40 1320 520 1195 450 1060 390 915 330
0.50 1265 495 1160 430 1020 375 890 320
0.60 1210 475 1105 410 975 350 840 295
0.70 1135 450 1045 380 910 325 775 280
0.80 1025 415 915 345 810 300 720 265
0.90 885 380 815 320 725 270 640 240
NOTE − All air data is measured external to unit with 1 in. cleanable filter (not furnished − field provided) in place. Also see Filter Air Resistance table.
G40UH−36A−070 PERFORMANCE
External Static Air Volume / Watts at Various Blower Speeds
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
0.00 0 1500 710 705 1290 610 565 985 465 455 830 390 375
0.05 12 1475 695 695 1275 600 555 980 465 445 820 385 365
0.10 25 1450 685 680 1255 590 545 970 460 440 810 380 360
0.15 37 1425 675 670 1240 585 535 965 455 430 805 380 355
0.20 50 1400 660 655 1225 580 525 955 450 425 795 375 350
0.25 62 1370 645 645 1205 570 510 945 445 415 790 375 345
0.30 75 1340 630 630 1180 555 500 930 440 405 780 370 335
0.40 100 1285 605 610 1140 540 475 900 425 390 745 350 325
0.50 125 1215 575 580 1080 510 450 865 410 375 705 335 310
0.60 150 1150 545 560 1015 480 430 810 380 355 655 310 290
0.70 175 1060 500 535 940 445 405 730 345 330 585 275 270
0.80 200 955 450 515 800 375 370 655 310 305 480 225 260
0.90 225 785 370 475 605 285 325 585 275 270 410 195 255
NOTE − All air data is measured external to unit with 1 in. (25 mm) cleanable filter (not furnished − field provided) in place. Also see Filter Air Resistance table.
G40UH−36B−090 PERFORMANCE
External Static Air Volume / Watts at Various Blower Speeds
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
0.00 0 1500 710 720 1255 590 595 1040 490 460 900 425 370
0.05 12 1485 700 705 1250 590 580 1040 490 450 895 420 365
0.10 25 1465 690 685 1240 585 570 1035 490 445 890 420 360
0.15 37 1450 685 675 1235 585 555 1035 490 440 885 420 355
0.20 50 1435 675 660 1225 580 545 1030 485 435 880 415 350
0.25 62 1420 670 645 1215 575 530 1025 485 425 875 415 345
0.30 75 1400 660 630 1200 565 520 1020 480 415 870 410 340
0.40 100 1345 635 595 1170 550 495 1000 470 400 855 405 330
0.50 125 1300 615 575 1135 535 475 965 455 380 830 390 300
0.60 150 1235 585 545 1080 510 445 930 440 360 780 370 290
0.70 175 1165 550 510 1020 480 415 870 410 340 740 350 280
0.80 200 1080 510 480 940 445 385 800 380 315 670 315 260
0.90 225 985 465 445 840 395 355 710 335 290 600 285 245
NOTE − All air data is measured external to unit with 1 in. (25 mm) cleanable filter (not furnished − field provided) in place. Also see Filter Air Resistance table.

Page 6
BLOWER DATA
G40UH−36C−110 PERFORMANCE
External Static Air Volume / Watts at Various Blower Speeds
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
0.00 0 1555 735 715 1335 630 575 1085 510 460 925 435 365
0.05 12 1540 725 705 1330 630 555 1080 510 450 920 435 360
0.10 25 1525 720 690 1320 625 545 1075 505 440 915 430 355
0.15 37 1510 715 680 1310 620 535 1070 505 430 910 430 350
0.20 50 1490 705 670 1295 610 525 1065 505 420 900 425 340
0.25 62 1465 690 655 1280 605 510 1060 500 415 890 420 335
0.30 75 1440 680 645 1260 595 495 1050 495 405 880 415 330
0.40 100 1385 655 615 1230 580 485 1030 485 390 865 410 320
0.50 125 1320 625 590 1190 560 460 995 470 375 835 395 300
0.60 150 1260 595 570 1135 535 430 960 455 355 815 385 295
0.70 175 1190 560 545 1075 505 410 915 430 345 775 365 285
0.80 200 1090 515 515 970 460 385 860 405 325 760 360 280
0.90 225 975 460 485 880 415 360 790 375 305 705 335 275
NOTE − All air data is measured external to unit with 1 in. (25 mm) cleanable filter (not furnished − field provided) in place. Also see Filter Air Resistance table.
G40UH−48B−070 PERFORMANCE
External Static Air Volume / Watts at Different Blower Speeds
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
.00 0 2080 980 846 1810 855 764 1535 725 634 1295 610 519
.10 25 2030 955 810 1790 845 714 1520 715 600 1285 605 492
.20 50 1955 920 767 1760 830 675 1515 715 566 1275 600 477
.30 75 1885 890 732 1710 805 640 1505 710 555 1265 595 459
.40 100 1820 860 699 1670 790 611 1470 695 525 1255 590 443
.50 125 1740 820 664 1600 755 575 1420 670 496 1215 575 414
.60 150 1635 770 624 1530 720 544 1350 635 464 1175 555 400
.70 175 1545 730 597 1420 670 501 1270 600 432 1080 510 368
.80 200 1400 660 554 1295 610 462 1135 535 392 990 465 343
.90 225 1250 590 512 1125 530 419 1050 495 372 875 410 310
NOTES − All air data is measured external to unit with 1 in. (25 mm) cleanable filter (not furnished − field provided) in place. Also see Filter Air Resistance table.
Air volume based on bottom air return air. Actual air volume may vary on side return air applications.
G40UH−48B−090 PERFORMANCE
External Static Air Volume / Watts at Various Blower Speeds
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
0.00 0 1970 930 790 1810 855 735 1585 750 670 1340 630 565
0.05 12 1940 915 780 1785 840 715 1580 745 650 1335 630 555
0.10 25 1915 905 765 1760 830 695 1570 740 630 1325 625 540
0.15 37 1880 885 745 1730 815 660 1560 735 615 1325 625 530
0.20 50 1840 870 730 1700 800 620 1545 730 600 1320 625 520
0.25 62 1805 850 715 1670 790 625 1520 715 585 1310 620 510
0.30 75 1765 835 695 1640 775 625 1490 705 565 1295 610 500
0.40 100 1695 800 670 1570 740 595 1440 680 540 1260 595 480
0.50 125 1600 755 635 1490 705 560 1360 640 505 1195 565 450
0.60 150 1505 710 600 1400 660 530 1285 605 480 1140 540 425
0.70 175 1395 660 565 1265 595 485 1170 550 440 990 465 380
0.80 200 1250 590 520 1100 520 445 975 460 390 905 425 355
0.90 225 1005 475 460 870 410 385 900 425 365 810 380 325
NOTE − All air data is measured external to unit with 1 in. (25 mm) cleanable filter (not furnished − field provided) in place. Also see Filter Air Resistance table.

Page 7
BLOWER DATA
G40UH−48C−110 PERFORMANCE
External Static Air Volume / Watts at Various Blower Speeds
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
0.00 0 2015 950 895 1620 765 780 1340 630 640 1150 545 525
0.05 12 1990 940 870 1615 760 760 1340 630 640 1150 545 525
0.10 25 1965 925 850 1610 760 745 1340 630 640 1150 545 525
0.15 37 1930 910 825 1605 755 725 1335 630 630 1150 545 525
0.20 50 1895 895 805 1600 755 710 1335 630 615 1150 545 525
0.25 62 1860 880 785 1590 750 695 1330 630 605 1150 545 520
0.30 75 1820 860 765 1580 745 675 1330 630 590 1145 540 515
0.40 100 1740 820 725 1530 720 635 1320 625 560 1140 540 490
0.50 125 1665 785 695 1475 695 600 1285 605 525 1120 530 470
0.60 150 1575 745 650 1405 665 555 1230 580 490 1075 505 445
0.70 175 1475 695 610 1310 620 515 1165 550 470 1015 480 415
0.80 200 1350 635 560 1210 570 485 1080 510 430 930 440 380
0.90 225 1210 570 520 1070 505 430 870 410 365 740 350 325
NOTE − All air data is measured external to unit with 1 in. (25 mm) cleanable filter (not furnished − field provided) in place. Also see Filter Air Resistance table.
G40UH−48C−135 PERFORMANCE
External Static Air Volume / Watts at Various Blower Speeds
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
0.00 0 2075 980 820 1800 850 710 1425 675 570 1115 525 435
0.05 12 2035 960 805 1785 840 695 1425 670 560 1120 530 435
0.10 25 1990 940 790 1765 835 675 1420 670 545 1125 530 430
0.15 37 1950 920 765 1740 820 660 1410 665 535 1125 530 425
0.20 50 1905 900 745 1715 810 645 1405 665 525 1120 530 420
0.25 62 1865 880 730 1680 795 625 1390 655 515 1115 525 410
0.30 75 1825 860 715 1650 780 610 1375 650 505 1105 520 405
0.40 100 1740 820 680 1585 745 580 1355 640 485 1090 515 390
0.50 125 1640 775 645 1495 705 545 1300 615 455 1050 495 370
0.60 150 1540 730 615 1420 670 515 1225 580 430 1000 470 355
0.70 175 1420 670 575 1310 615 475 1140 535 400 935 440 330
0.80 200 1260 595 520 1155 545 425 1025 485 365 865 410 315
0.90 225 1125 530 495 1010 475 385 880 415 330 750 355 285
NOTE − All air data is measured external to unit with 1 in. (25 mm) cleanable filter (not furnished − field provided) in place. Also see Filter Air Resistance table.

Page 8
BLOWER DATA
G40UH−60C−110−1, −2, −3 with 3/4 hp motor PERFORMANCE − Bottom Return Air, Side Return Air with Optional RAB Return
Air Base, Return Air from Both Sides or Return Air from Bottom and One Side.
External Static Air Volume / Watts at Various Blower Speeds
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
0.00 0 2450 1155 1220 2300 1085 1060 2056 970 905 1725 815 735
0.05 12 2410 1135 1205 2265 1070 1045 2040 965 895 1715 810 725
0.10 25 2370 1120 1195 2230 1050 1030 2020 955 890 1710 810 720
0.15 37 2325 1095 1175 2200 1040 1015 1995 940 875 1700 800 715
0.20 50 2280 1075 1165 2170 1025 1005 1975 935 870 1695 800 710
0.25 62 2245 1060 1150 2130 1005 990 1950 920 855 1680 795 705
0.30 75 2205 1040 1135 2095 990 975 1925 910 845 1665 785 700
0.40 100 2115 995 1105 2010 950 940 1860 875 820 1625 770 685
0.50 125 2025 955 1060 1945 920 920 1810 855 805 1605 755 675
0.60 150 1910 900 1015 1850 875 885 1715 810 780 1540 730 670
0.70 175 1835 865 1005 1775 840 865 1655 780 765 1495 705 655
0.80 200 1745 825 975 1655 780 835 1540 725 730 1400 660 635
0.90 225 1610 760 945 1540 725 805 1475 695 715 1310 620 615
NOTE − All air data is measured external to unit with 1 in. (25 mm) cleanable filter (not furnished − field provided) in place. Also see Filter Air Resistance table.
G40UH−60C−110−1, −2, −3 with 3/4 hp motor PERFORMANCE − Single Side Return Air − Air volumes in bold require field fab-
ricated transition to accommodate 20 x 25 x 1 in. (508 x 635 x25 mm) cleanable air filter in order to maintain proper air
velocity.
External Static Air Volume / Watts at Various Blower Speeds
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
0.00 0 2395 1130 1230 2260 1065 1085 2015 950 920 1730 815 750
0.05 12 2365 1115 1220 2230 1050 1070 1985 935 905 1720 810 745
0.10 25 2330 1100 1205 2200 1040 1060 1960 925 890 1705 805 750
0.15 37 2285 1080 1190 2170 1025 1045 1030 485 880 1695 800 740
0.20 50 2245 1060 1170 2135 1010 1030 1905 900 870 1675 790 735
0.25 62 2200 1040 1160 2100 990 1020 1890 890 860 1665 785 730
0.30 75 2170 1025 1145 2070 980 1005 1870 880 850 1655 780 720
0.40 100 2085 985 1110 1990 940 975 1825 860 835 1610 760 705
0.50 125 1980 935 1075 1910 900 945 1755 830 810 1555 735 690
0.60 150 1890 890 1045 1835 865 915 1670 790 780 1515 715 680
0.70 175 1800 850 1020 1725 815 885 1615 760 770 1445 685 655
0.80 200 1700 805 995 1645 775 855 1525 720 745 1380 650 645
0.90 225 1590 750 980 1520 720 820 1410 665 710 1300 615 625
NOTE − All air data is measured external to unit with 1 in. (25 mm) cleanable filter (not furnished − field provided) in place. Also see Filter Air Resistance table.

Page 9
BLOWER DATA
G40UH−60C−110 with 1 hp motor PERFORMANCE − Bottom Return Air, Side Return Air with Optional RAB Return Air
Base, Return Air from Both Sides or Return Air from Bottom and One Side.
External Static Air Volume / Watts at Different Blower Speeds
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
.00 0 2655 1250 1407 2370 1120 1063 2085 985 894 1665 785 679
.10 25 2580 1215 1376 2350 1110 1043 2065 975 875 1650 780 667
.20 50 2500 1180 1346 2305 1085 1012 2045 965 849 1645 775 662
.30 75 2410 1135 1305 2230 1050 978 2010 950 820 1640 775 649
.40 100 2320 1095 1270 2165 1020 947 1940 915 786 1625 765 634
.50 125 2225 1050 1235 2090 985 914 1895 895 763 1610 760 622
.60 150 2130 1005 1205 2000 945 880 1840 870 740 1570 740 603
.70 175 2030 955 1155 1915 905 851 1760 830 709 1535 725 590
.80 200 1925 910 1123 1820 860 823 1670 790 681 1475 695 566
.90 225 1795 845 1078 1690 795 788 1560 735 655 1395 660 537
NOTE − All air data is measured external to unit with 1 in. (25 mm) cleanable filter (not furnished − field provided) in place. Also see Filter Air Resistance table.
G40UH−60C−110 with 1 hp motor PERFORMANCE − Single Side Return Air − Air volumes in bold require field fabricated
transition to accommodate 20 x 25 x 1 in. (508 x 635 x 25 mm) cleanable air filter in order to maintain proper air velocity.
External Static Air Volume / Watts at Different Blower Speeds
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
.00 0 2430 1145 1309 2245 1060 1006 1910 900 843 1635 770 686
.10 25 2355 1110 1277 2190 1035 978 1905 900 817 1620 765 677
.20 50 2280 1075 1242 2140 1010 950 1885 890 797 1610 760 667
.30 75 2205 1040 1218 2075 980 924 1860 875 782 1605 755 655
.40 100 2130 1005 1189 2005 945 905 1815 855 752 1595 750 636
.50 125 2045 965 1159 1920 905 864 1750 825 726 1565 740 619
.60 150 1955 920 1132 1850 875 840 1700 800 705 1525 720 605
.70 175 1860 875 1105 1760 830 817 1610 760 674 1475 700 582
.80 200 1755 830 1067 1670 790 789 1540 725 654 1395 660 560
.90 225 1645 775 1033 1575 745 763 1445 680 627 1325 625 540
NOTE − All air data is measured external to unit with 1 in. (25 mm) cleanable filter (not furnished − field provided) in place. Also see Filter Air Resistance table.

Page 10
BLOWER DATA
G40UH−60D−135−1, −2, −3 with 3/4 hp motor PERFORMANCE − Bottom Return Air, Side Return Air with Optional RAB Re-
turn Air Base, Return Air from Both Sides or Return Air from Bottom and One Side.
External Static Air Volume / Watts at Various Blower Speeds
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
0.00 0 2465 1165 1205 2325 1100 1060 2155 1015 930 1895 895 780
0.05 12 2430 1145 1195 2295 1085 1050 2125 1000 920 1875 885 770
0.10 25 2395 1130 1180 2265 1070 1040 2095 990 910 1855 875 765
0.15 37 2350 1110 1165 2230 1050 1025 2070 975 900 1830 865 755
0.20 50 2310 1090 1150 2195 1035 1010 2045 965 890 1805 850 745
0.25 62 2265 1070 1135 2155 1015 995 2010 950 875 1785 840 735
0.30 75 2220 1050 1120 2115 1000 980 1975 930 865 1765 830 730
0.40 100 2120 1000 1080 2035 960 950 1915 905 845 1715 810 720
0.50 125 2050 970 1055 1955 925 925 1830 865 815 1645 775 700
0.60 150 1930 910 1015 1860 880 895 1745 825 795 1585 745 680
0.70 175 1835 865 985 1775 840 870 1655 780 770 1530 720 670
0.80 200 1720 810 955 1645 775 830 1560 735 745 1445 685 650
0.90 225 1595 755 925 1535 725 800 1455 685 720 1310 620 620
NOTE − All air data is measured external to unit with 1 in. (25 mm) cleanable filter (not furnished − field provided) in place. Also see Filter Air Resistance table.
G40UH−60D−135−1, −2, −3 with 3/4 hp motor PERFORMANCE − Single Side Return Air − Air volumes in bold require field fab-
ricated transition to accommodate 20 x 25 x 1 in. (508 x 635 x25 mm) cleanable air filter in order to maintain proper air
velocity.
External Static Air Volume / Watts at Various Blower Speeds
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
0.00 0 2350 1110 1180 2225 1050 1035 2055 970 905 1855 875 775
0.05 12 2310 1090 1170 2195 1035 1025 2035 960 895 1835 865 765
0.10 25 2275 1075 1155 2165 1020 1010 2010 950 885 1815 855 760
0.15 37 2235 1055 1140 2130 1005 1000 1980 935 875 1795 845 755
0.20 50 2195 1035 1130 2100 990 985 1945 920 865 1775 835 750
0.25 62 2155 1020 1115 2055 970 970 1915 905 855 1750 825 740
0.30 75 2115 1000 1100 2010 950 950 1885 890 845 1725 815 735
0.40 100 2010 950 1055 1940 915 930 1830 865 830 1665 785 720
0.50 125 1930 910 1035 1860 880 905 1745 825 805 1600 755 705
0.60 150 1830 865 1005 1770 835 880 1655 780 775 1530 720 685
0.70 175 1735 820 985 1655 780 845 1595 755 765 1480 700 675
0.80 200 1645 775 955 1545 730 815 1480 700 735 1375 650 650
0.90 225 1515 715 925 1435 675 785 1385 655 710 1290 610 630
NOTE − All air data is measured external to unit with 1 in. (25 mm) cleanable filter (not furnished − field provided) in place. Also see Filter Air Resistance table.

Page 11
BLOWER DATA
G40UH−60D−135 with 1 hp motor PERFORMANCE − Bottom Return Air, Side Return Air with Optional RAB Return Air Base,
Return Air from Both Sides or Return Air from Bottom and One Side.
External Static Air Volume / Watts at Different Blower Speeds
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
.00 0 2715 1280 1407 2255 1065 1070 1910 900 850 1660 785 674
.10 25 2640 1245 1403 2250 1060 1030 1900 895 834 1645 775 668
.20 50 2540 1200 1355 2245 1060 1006 1890 890 821 1630 770 665
.30 75 2480 1170 1319 2200 1040 975 1890 890 781 1625 765 656
.40 100 2390 1125 1282 2155 1015 940 1885 890 775 1615 760 642
.50 125 2320 1095 1251 2085 985 904 1860 875 758 1605 755 631
.60 150 2205 1040 1210 2020 955 876 1815 855 731 1595 750 611
.70 175 2080 980 1161 1935 915 839 1760 830 707 1545 730 588
.80 200 2010 950 1122 1855 875 810 1690 795 679 1495 705 568
.90 225 1880 885 1071 1755 830 781 1585 745 646 1430 675 545
NOTE − All air data is measured external to unit with 1 in. (25 mm) cleanable filter (not furnished − field provided) in place. Also see Filter Air Resistance table.
G40UH−60D−135 with 1 hp motor PERFORMANCE − Single Side Return Air − Air volumes in bold require field fabricated
transition to accommodate 20 x 25 x 1 in. (508 x 635 x 25 mm) cleanable air filter in order to maintain proper air velocity.
External Static Air Volume / Watts at Different Blower Speeds
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
.00 0 2455 1160 1336 2170 1025 1019 1850 875 829 1555 735 673
.10 25 2380 1125 1299 2140 1010 974 1840 870 812 1550 730 664
.20 50 2305 1085 1266 2105 995 947 1830 865 791 1545 730 656
.30 75 2235 1055 1234 2045 965 914 1820 860 774 1540 725 642
.40 100 2160 1020 1240 1985 935 886 1800 850 755 1540 725 628
.50 125 2065 975 1170 1925 910 863 1745 825 726 1535 725 614
.60 150 1990 940 1146 1870 880 844 1700 800 706 1505 710 599
.70 175 1895 895 1111 1775 835 808 1655 780 689 1465 690 573
.80 200 1805 850 1074 1680 790 779 1565 740 656 1425 670 562
.90 225 1695 800 1042 1590 750 752 1480 700 630 1335 630 533
NOTE − All air data is measured external to unit with 1 in. (25 mm) cleanable filter (not furnished − field provided) in place. Also see Filter Air Resistance table.
G40UH−60D−155−1, −2, −3 with 3/4 hp motor PERFORMANCE − Bottom Return Air, Side Return Air with Optional RAB Re-
turn Air Base, Return Air from Both Sides or Return Air from Bottom and One Side.
External Static Air Volume / Watts at Various Blower Speeds
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
0.00 0 2380 1120 1135 2235 1055 1000 2060 970 875 1875 885 750
0.05 12 2340 1105 1130 2205 1040 990 2035 960 865 1840 870 745
0.10 25 2305 1090 1125 2180 1030 975 2015 950 855 1810 855 735
0.15 37 2265 1070 1105 2145 1010 960 1990 940 845 1790 845 725
0.20 50 2220 1045 1090 2105 995 945 1960 925 835 1765 835 720
0.25 62 2180 1030 1075 2080 980 935 1935 910 825 1740 820 710
0.30 75 2145 1010 1065 2050 965 925 1905 900 815 1715 810 700
0.40 100 2060 970 1040 1975 930 900 1845 870 795 1655 780 685
0.50 125 1955 925 1005 1890 890 870 1765 835 770 1610 760 670
0.60 150 1885 890 975 1795 850 840 1695 800 750 1560 735 655
0.70 175 1800 850 955 1730 815 815 1605 760 720 1480 700 635
0.80 200 1700 805 930 1630 770 785 1520 715 695 1405 660 615
0.90 225 1575 745 895 1525 720 760 1395 660 660 1285 605 585
NOTE − All air data is measured external to unit with 1 in. (25 mm) cleanable filter (not furnished − field provided) in place. Also see Filter Air Resistance table.

Page 12
BLOWER DATA
G40UH−60D−155−1, −2, −3 with 3/4 hp motor PERFORMANCE − Single Side Return Air − Air volumes in bold require field fab-
ricated transition to accommodate 20 x 25 x 1 in. (508 x 635 x25 mm) cleanable air filter in order to maintain proper air
velocity.
External Static Air Volume / Watts at Various Blower Speeds
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
0.00 0 2230 1050 1080 2130 1005 945 1995 940 840 1830 865 745
0.05 12 2200 1035 1070 2105 990 935 1970 930 830 1810 855 735
0.10 25 2165 1025 1060 2075 980 930 1950 920 820 1795 845 725
0.15 37 2135 1005 1050 2040 965 915 1920 905 815 1765 835 720
0.20 50 2100 990 1035 2005 945 905 1890 895 805 1735 820 710
0.25 62 2050 965 1015 1975 930 895 1855 875 795 1705 805 700
0.30 75 2000 945 995 1940 915 880 1820 860 780 1675 790 690
0.40 100 1905 900 965 1860 875 850 1755 825 770 1630 770 680
0.50 125 1825 860 945 1780 840 830 1700 800 750 1555 735 660
0.60 150 1745 825 920 1690 795 805 1595 750 715 1495 705 645
0.70 175 1650 780 905 1610 760 785 1515 715 705 1430 675 625
0.80 200 1565 740 880 1520 715 755 1445 680 680 1330 630 605
0.90 225 1445 685 845 1385 655 720 1300 610 640 1225 580 575
NOTE − All air data is measured external to unit with 1 in. (25 mm) cleanable filter (not furnished − field provided) in place. Also see Filter Air Resistance table.
G40UH−60D−155 with 1 hp motor PERFORMANCE − Bottom Return Air, Side Return Air with Optional RAB Return Air Base,
Return Air from Both Sides or Return Air from Bottom and One Side.
External Static Air Volume / Watts at Different Blower Speeds
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
.00 0 2670 1260 1386 2325 1095 1048 1970 930 857 1700 800 706
.10 25 2580 1215 1342 2320 1095 1045 1965 925 842 1690 795 696
.20 50 2510 1185 1311 2255 1065 985 1960 925 817 1640 775 662
.30 75 2425 1145 1277 2210 1040 953 1955 920 803 1635 770 649
.40 100 2345 1105 1246 2150 1015 922 1925 910 778 1630 770 633
.50 125 2255 1065 1217 2095 990 897 1890 890 752 1615 760 618
.60 150 2170 1025 1182 2010 950 863 1840 870 733 1590 750 605
.70 175 2090 985 1139 1925 910 833 1785 840 708 1550 730 588
.80 200 1895 895 1106 1840 870 806 1710 805 683 1500 705 571
.90 225 1855 875 1064 1740 820 776 1620 765 655 1430 675 551
NOTE − All air data is measured external to unit with 1 in. (25 mm) cleanable filter (not furnished − field provided) in place. Also see Filter Air Resistance table.
G40UH−60D−155 with 1 hp motor PERFORMANCE − Single Side Return Air − Air volumes in bold require field fabricated
transition to accommodate 20 x 25 x 1 in. (508 x 635 x 25 mm) cleanable air filter in order to maintain proper air velocity.
External Static Air Volume / Watts at Different Blower Speeds
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
.00 0 2410 1135 1282 2175 1025 987 1870 880 833 1620 765 675
.10 25 2335 1100 1257 2140 1010 956 1860 875 810 1610 760 667
.20 50 2255 1065 1225 2085 985 918 1855 875 788 1605 755 658
.30 75 2205 1040 1200 2025 955 896 1830 865 764 1600 755 647
.40 100 2120 1000 1164 1975 930 874 1795 845 742 1595 750 628
.50 125 2040 960 1131 1905 900 847 1745 825 731 1575 745 618
.60 150 1955 920 1103 1835 865 820 1695 800 698 1540 725 601
.70 175 1870 880 1069 1760 830 792 1635 770 673 1465 690 568
.80 200 1770 835 1041 1670 790 763 1560 735 646 1415 665 548
.90 225 1660 785 1006 1585 745 740 1480 700 629 1345 635 527
NOTE − All air data is measured external to unit with 1 in. (25 mm) cleanable filter (not furnished − field provided) in place. Also see Filter Air Resistance table.

Page 13
FILTER AIR RESITANCE
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)
HIGH ALTITUDE
All −1 to −14 models − Pressure regulator adjustment may be
required depending on altitude. See below for proper pressure
regulator setting.
Manifold 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) 3.2 (.80) 3.1 (.77)
LPG/Propane 10.0 (2.49)
All −15 and later models − Pressure regulator adjustment is
not rquired. See below for proper pressure regulator setting.
Manifold Pressure (Outlet) in. w.g. (kPa)
FUEL
ALTITUDE ft. (m)
FUEL
0 − 10,000 (0 − 3048)
Natural Gas 3.5 (.87)
LPG/Propane 10.0 (2.49)
HIGH ALTITUDE
G40UH−1
1High Altitude
Orifice Kit
Natural Gas Only
High Altitude Prove
Switch Kit
LPG/Propane Kit
G40UH−1
to −14 Natural Gas Only 4501−7500 ft.
(1373− 2236m)
7501−10,000 ft.
(2287 − 3048m)
0−7500 ft.
(0 − 2286m)
7501−10,000 ft.
(2286 − 3048m)
−045−
−070
47M82 56L32 56L32 45L60 47M81
−090 47M82 49L90 15M22 45L60 47M81
−110 47M82 49L90 15M22 45L60 47M81
−135 47M82 49L90 15M22 45L60 47M81
−155 47M82 49L90 15M22 45L60 47M81
G40UH−15
1High Altitude
Orifice Kit
Natural Gas Only
High Altitude Pressure
Switch Kit
LPG/Propane Kit
G40UH−15
and later Natural Gas Only 4501−7500 ft.
(1373 − 2286m)
7501−10,000 ft.
(2287 − 3048m)
0−7500 ft.
(0 − 2286m)
7501−10,000 ft.
(2286 − 3048m)
all models 59M17 NO CHANGE 56L32 25W20 25W21
1Required for proper operation at altitudes from 7501 to 10,000 ft.

Page 14
Flue Transition
Combustion Air Inducer
Combustion Air Orifice
Combustion Air
Prove Switch
Flue Collector Box
Heat Exchanger
Flame Sensor
Gas Valve
Burners
Ignitor
NOxInsert
Primary Limit
Blower Assembly
Capacitor
Gasket
Flue Box Gasket
Flame Rollout Switches*
Flame Rollout Bracket
Gas Orifices
Ignitor Bracket
Burner Bottom Shield
Limit Shield
Secondary Limit
(as required)
(NOxUnits Only)
G40UH(X) PARTS ARRANGEMENT
FIGURE 1
Gas Manifold
*135 and 155 kBtuh units only −−
Flame rollout switches are located
on brackets on the inner sides (one
on the left and one on the right) of
the burner box.
Air Deflector
G40UH−48C−135,
G40UH−36C−110,
G40UH−60D−155 &
G40UH−60C−110−1, −2, −3
Units Only
SureLight Control
Transformer
DoorInterlock Switch
Pressure Port Location
For −1 to −14 Units
Pressure
Port

Page 15
FIGURE 2
G40UH(X) PARTS IDENTIFICATION
(HORIZONTAL POSITION)
BLOWER
ACCESS PANEL
HEAT EXCHANGER ASSEMBLY
BURNER
ASSEMBLY
COMBUSTION AIR
INDUCER
CONTROL
BOARD
PROVE
SWITCH
GAS VALVE
BURNER
ACCESS PANEL
BLOWER ASSEMBLY
PRIMARY LIMIT
SECONDARY LIMIT
FIGURE 3
G40UH(X) HEATING COMPONENTS
COMBUSTION AIR INDUCER
PROVE SWITCH
PRIMARY LIMIT
PRIMARY LIMIT SHIELD
GAS VALVE
ROLLOUT SWITCHES*
MANIFOLD/BURNER
ASSEMBLY
NOxInsert
(NOxUnits Only)
HEAT EXCHANGER
FLUE COLLECTOR BOX
*135 and 155 kBtuh units only −−
Flame rollout switches are located
on brackets on the inner sides (one
on the left and one on the right) of
the burner box.
Air Deflector
G40UH−48C−135,
G40UH−36C−110,
G40UH−60D−155 &
G40UH−60C−110−1,
−2, −3 Units Only

Page 16
I−UNIT COMPONENTS
G40UH(X) unit components are shown in figures 1, 2, 3
and 4. The gas valve, combustion air inducer and burners
can be accessed by removing the burner access panel.
Electrical components are in the control box (figure 4)
found in the blower section.
G40UH(X) units are factory equipped with a bottom return air
panel in place. The panel is designed to be field removed as
required for bottom air return. Markings are provided for side
return air and may be cut out in the field.
CAUTION
Electrostatic discharge can affect electronic
components. Take precautions during furnace
installation and service to protect the furnace’s
electronic controls. Precautions will help to
avoid control exposure to electrostatic dis-
charge by putting the furnace, the control and
the technician at the same electrostatic poten-
tial. Neutralize electrostatic charge by touching
hand and all tools on an unpainted unit surface,
such as the gas valve or blower deck, before per-
forming any service procedure.
ELECTROSTATIC DISCHARGE (ESD)
Precautions and Procedures
1. Control Transformer (T1)
A transformer located in the control box provides power to
the low voltage section of the unit. Transformers on all
models are rated 40VA with a 120V primary and a 24V sec-
ondary.
2.Door Interlock Switch (S51)
A door interlock switch rated 14A at 125VAC is wired in se-
ries with line voltage. When the blower door is removed the
unit will shut down.
FIGURE 4
CONTROL BOX
G40UH(X)
SureLight Control
Transformer
DoorInterlock Switch
WARNING
Shock hazard.
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.
3. SureLight Integrated Ignition Control
(A92) 10M93 & 56L84
The Lennox SureLight ignition system consists of ignition
control (figure 5 with control terminal designations in table
1), sensor (figure 10) and ignitor (figure 11). The ignition
control and ignitor work in combination to ensure furnace
ignition and ignitor durability. The ignition control, controls
all major furnace operations. The ignition control also fea-
tures two LED lights for troubleshooting and two accesso-
ry terminals rated at (1) one amp. Tables 2 and 3 show jack
plug terminal designations. See table 4 for troubleshooting
diagnostic codes. Units equipped with the SureLight sys-
tem can be used with either electronic or electro−mechani-
cal thermostats without modification. The SureLight igni-
tor is made of durable silicon−nitride. Ignitor longevity is
also enhanced by voltage ramping by the ignition control .
The ignition control finds the lowest ignitor temperature
which will successfully light the burner, thus increasing
the life of the ignitor.
TABLE 1
SURELIGHT CONTROL TERMINAL DESIGNATIONS
COOL Blower − Cooling Speed (120V)
HEAT Blower − Heating Speed (120V)
PARK Unused Blower Lead (not energized)
FAN Continuous Low Blower Speed
EAC Accessory Terminal (120V)
XFMR Transformer (120V)
LINE Input (120V)
HUM Heat Only Accessory (120V)
5 Terminals 120V Neutral
FS Flamer Sensor
TABLE 2
SURELIGHT CONTROL J156 (J2) TERMINAL
DESIGNATIONS
PIN # FUNCTION
1Combustion Air Inducer Line
2Ignitor Line
3Combustion Air Inducer Neutral
4Ignitor Neutral

Page 17
SURELIGHT INTEGRATED CONTROL BOARD
FIGURE 5
J156
FLAME SENSE
J58
XFMR−N
TABLE 3
SUERLIGHT CONTROL J58 (J1) TERMINAL
DESIGNATIONS
PIN # FUNCTION
1Secondary Limit
2Not Used
324V
4Not Used
5Rollout Switch In
624V
7Primary Limit
8Ground
9Gas Valve In
10 Pressure Switch Out
11 Rollout Switch Out
12 Gas Valve Out
a−Electronic Ignition (See Figure 7)
On a call for heat the SureLight control monitors the com-
bustion air inducer prove switch. The control will not begin
the heating cycle if the prove switch is closed (by−passed).
Once the proving switch is determined to be open, the com-
bustion air inducer is energized. When the differential in the
prove switch is great enough, the prove switch closes and a
15−second pre−purge begins. If the prove switch is not
proven within 2−1/2 minutes, the control goes into Watch-
guard−Pressure Switch mode for a 5−minute re−set period.
After the 15−second pre−purge period, the SureLight ignitor
warms up for 20 seconds during which the gas valve opens
at 19 seconds for a 4−second trial for ignition. Units with
control 56L84: the ignitor stays energized for the first sec-
ond of the 4−second trial. Units with control 10M93: ignitor
stays energized the full 4 second trial. If ignition is not
proved during the 4−second period, the control (56L84 or
10M93) will try four more times with an inter purge and
warm−up time between trials of 35 seconds. After a total of
five trials for ignition (including the initial trial), the control
goes into Watchguard−Flame Failure mode. After a 60−min-
ute reset period, the control will begin the ignition sequence
again.
The SureLight control board has an added feature that pro-
longs the life of the ignitor. After a successful ignition, the
SureLight control utilizes less power to energize the ignitor
on successive calls for heat. The control continues to ramp
down the voltage to the ignitor until it finds the lowest
amount of power that will provide a successful ignition. This
amount of power is used for 255 cycles. On the 256th call
for heat, the control will again ramp down until the lowest
power is determined and the cycle begins again.
b−Fan Time Control
The fan on time of 45 seconds is not adjustable. Fan off
time (time that the blower operates after the heat demand
has been satisfied) can be adjusted by flipping the dip
switches located on the SureLight integrated control. The
unit is shipped with a factory fan off setting of 90 seconds.
For customized comfort, monitor the supply air tempera-
ture once the heat demand is satisfied. Note the supply air
temperature at the instant the blower is de−energized. Ad-
just the fan−off delay to achieve a supply air temperature
between 90° − 110° at the instant the blower is de−ener-
gized. (Longer delay times allow for lower air temperature,
shorter delay times allow for higher air temperature). See
figure 6.
FIGURE 6
FAN-OFF TIME ADJUSTMENT
To adjust fan−off timing, flip dip switch to desired setting.
60sec. 90sec. 120sec. 180sec.

Page 18
The ignition control is equipped with two LED lights for troubleshooting. The diagnostic codes are listed below in table 4.
TABLE 4
DIAGNOSTIC CODES
Make sure to Identify LED’S Correctly.
Refer to figures 5 and 8 for control board layout.
LED #1
DS #1
AN #1
LED #2
DS #2
AN #2
DESCRIPTION
SIMULTANEOUS
SLOW FLASH
SIMULTANEOUS
SLOW FLASH
Power on − Normal operation.
Also signaled during cooling and continuous fan.
SIMULTANEOUS
FAST FLASH
SIMULTANEOUS
FAST FLASH Normal operation − signaled when heating demand initiated at thermostat.
SLOW FLASH ON Primary or secondary limit switch open. Limit must close within 3 minutes or unit
goes into 1 hour Watchguard.
OFF SLOW FLASH
Prove switch open.
OR: Blocked inlet/exhaust vent;
OR: Prove switch closed prior to activation of combustion air inducer.
ALTERNATING
SLOW FLASH
ALTERNATING
SLOW FLASH Watchguard −− burners failed to ignite.
SLOW FLASH OFF Flame sensed without gas valve energized.
ON SLOW FLASH Rollout switch open. OR: 24V pin connector improperly attached.
ON ON
ON OFF Circuit board failure or control wired incorrectly.
OFF ON
y
FAST FLASH SLOW FLASH Main power polarity reversed. Switch line and neutral.
SLOW FLASH FAST FLASH Low flame signal. See Table 15 for flame sense.
ALTERNATING
FAST FLASH
ALTERNATING
FAST FLASH
The following conditions are sensed
Improper main ground (Control 10M93, 57L84) during ignitor warm up period
ONLY, improper main ground continuously (Control 78M47 & 100973−01)
OR: Broken ignitor (Control 10M93, 57L84)
OR: Open ignitor circuit (Control 78M47 & 100973−01)
OR: Line voltage below 75V (Control 10M93, 57L84) 90V (Control 78M47 &
100973−01)
NOTE − Slow flash rate equals 1 Hz (one flash per second). Fast flash rate equals 3 Hz (three flashes per second).
FIGURE 7
ÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉ
ÉÉÉÉÉÉÉÉÉÉÉÉÉ
ÉÉ
ÉÉ
DEMAND
CAI
GAS VALVE
15
ON
OFF
ÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉ
ÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉ
ÉÉ
38
ÉÉÉÉÉÉÉÉÉÉ
ÉÉÉÉÉÉÉÉÉÉ
IGNITOR
34
1
Pre −Purge Ignitor Warm−up Trial for
Ignition Post
Purge
5 SEC80
*Blower on time will be 45 seconds after gas valve is energized. Blower off time will depend on OFF TIME" Setting.
INDOOR BLOWER
ÉÉÉÉÉÉÉÉÉ
ÉÉÉÉÉÉÉÉÉ
Blower On"
Delay
IGNITION CONTROL 10M93 & 56L84** & 78M47*** & 100973−01
**Ignitor on control 57L84 will energize for the first second ONLY of the 4 second ignition trial
***ignitor on control 78M47 & 100973−01 will energize the first three seconds ONLY of the 4 second ignition trial

Page 19
4. Integrated Ignition Control (A92)
78M47 & 100973−01
WARNING
Shock hazard.
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.
The hot surface ignition control system consisting of an in-
tegrated control board (figure 8 with control terminal des-
ignations in table 7), sensor (figure 10) and ignitor (figure
11). The ignition control board and ignitor work in com-
bination to ensure furnace ignition and ignitor durability.
The ignition control, controls all major furnace operations.
The ignition control also features two LED lights (AN1 red
and AN2 green) for troubleshooting and two accessory
terminals rated at (1) one amp. The ignition control also
features a (3) amp fuse for overcurrent protection. Tables 5
and 6 show jack plug terminal designations. See table 4 for
troubleshooting diagnostic codes. The mini−nitride ignitor
is made from a non−porous, high strength proprietary ce-
ramic material that provides long life and trouble free
maintenance. The ignition control continuously monitors
line voltage and maintains the ignitor power at a consis-
tent level to provide proper lighting and maximum ignitor
life.
TABLE 5
4−Pin Terminal Designation
PIN # FUNCTION
1Combustion Air Inducer Line
2Ignitor Line
3Combustion Air Inducer Neutral
4Ignitor Neutral
TABLE 6
12−Pin Terminal Designations
PIN # FUNCTION
1High Limit Output
2Not Used
324V Line
4Not Used
5Rollout Switch Out
624V Neutral
7High Limit Input
8 Ground
9Gas Valve Common
10 Prove Switch In
11 Rollout Switch In
12 Gas Valve Out
INTEGRATED IGNITION CONTROL
FIGURE 8
AN2
GREEN
AN1
RED
TABLE 7
TERMINAL DESIGNATIONS
120 Volt Hot
COOL Cool Speed
HEAT Heat Speed
PARK Park
PARK Park
EAC Electronic Air Cleaner
XFMR Transformer
LINE Line
HUM Humidifier
120 Volt Neutral
CIRC Blower
XMFR Transformer
HUM Humidifier
LINE Line
Flame FS Flame Signal

Page 20
Electronic Ignition (See Figure 7)
On a call for heat the ignition board monitors the combus-
tion air inducer prove switch. The control board will not be-
gin the heating cycle if the prove switch is closed (by−
passed). Once the prove switch is determined to be open,
the combustion air inducer is energized. When the differen-
tial in the prove switch is great enough, the prove switch
closes and a 15−second pre−purge begins. If the prove
switch is not proven within 2−1/2 minutes, the control board
goes into Watchguard−Pressure Switch mode for a 5−min-
ute re−set period.
After the 15−second pre−purge period, the ignitor warms up
for 20 seconds during which the gas valve opens at 19 sec-
onds for a 4−second trial for ignition. The ignitor remains
energized for the first 3 seconds during the 4 second trial. If
ignition is not proved during the 4−second period, the con-
trol will try four more times with an inter purge and warm−up
time between trials of 35 seconds. After a total of five trials
for ignition (including the initial trial), the control goes into
Watchguard−Flame Failure mode. After a 60−minute reset
period, the control will begin the ignition sequence again.
The control board has an added feature of ignitor power
regulation to maintain consistent lighting and longer ignitor
life under all line voltage conditions.
Fan Time Control
The fan on time of 45 seconds is not adjustable. Fan off
time (time that the blower operates after the heat demand
has been satisfied) can be adjusted by moving the jumper
to a different setting. The unit is shipped with a factory fan
off setting of 90 seconds. For customized comfort, monitor
the supply air temperature once the heat demand is satis-
fied. Note the supply air temperature at the instant the
blower is de−energized.
Adjust the fan−off delay to achieve a supply air temperature
between 90° − 110° at the instant the blower is de−ener-
gized. (Longer delay times allow for lower air temperature,
shorter delay times allow for higher air temperature). See
figure 9.
Board 100973−01 only has a 45 second fan off delay after
cooling demand has been met. This delay is factory set and
not adjustable.
FAN-OFF TIME ADJUSTMENT
To adjust fan−off timing, reposition jumper across pins to
achieve desired setting.
FIGURE 9
5.Flame Sensor (Figure 10)
A flame sensor is located on the left side of the burner sup-
port. See figure 10. The sensor is mounted on the flame rol-
lout plate and the tip protrudes into the flame envelope of
the left−most burner. The sensor can be removed for ser-
vice without removing any part of the burners. During op-
eration, flame is sensed by current passed through the
flame and sensing electrode. The ignition control allows
the gas valve to remain open as long as flame signal is
sensed.
6. Ignitor (Figure 11)
The SureLight ignitor used on G40UH units, is made of du-
rable silicon nitride. The board finds the lowest ignitor tem-
perature which will successfully light the burner, thus in-
creasing the life of the ignitor. Due to this feature of the
board, voltage cannot be measured. The check ignitor,
measure its resistance. A value of 10.9 to 19.7 ohms indi-
cates a good ignitor.
The mini−nitride ignitor used on G40UH units (equipped
with control 78M47 or 100973−01) is made from a propri-
etary ceramic material. Ignitor longevity is enhanced by
controlling the voltage to the ignitor. The check ignitor,
measure its resistance. A value of 50 to 450 ohms indicates
a good ignitor.
NOTE − The G40UH(X) furnace contains electronic
components that are polarity sensitive. Make sure that
the furnace is wired correctly and is properly grounded.
FIGURE 10
5/16"