Lennox G41UF?24B?045 Service manual

Page 1 2003 Lennox Industries Inc.
Litho U.S.A.
Corp. 0303−L2 G41UF
Service Literature
G41UF SERIES UNITS
G41UF series units are high−efficiency upflow gas fur
naces manufactured with Lennox DuralokPlustalumi
nized primary and stainless steel secondary clamshelltype
heat exchangers. G41UF units are available in heating
input capacities of 44,000 to 132,000 Btuh (12.9 to 38.6 kW)
and cooling applications from 2 through 5 tons (7.0 through
17.6 kW). Refer to Engineering Handbook for proper sizing.
Units are factory equipped for use with natural gas. A kit is
available for conversion to LPG operation. All G41UF
units are equipped with the Lennox SureLight® hot sur
face ignition system. The gas valve is redundant to as
sure safety shut−off as required by C.S.A.
The heat exchanger, burners and manifold assembly can be
removed for inspection and service. The maintenance section
gives a detailed description on how this is done.
Information contained in this manual is intended for use by
qualified service technicians only. All specifications are sub
ject to change. Procedures outlined in this manual are pre
sented as a recommendation only and do not supersede or
replace local or state codes.
Table of Contents
General 1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Specifications 2. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Blower Performance Data 3. . . . . . . . . . . . . . . . . . . . . .
I−Unit Components 8. . . . . . . . . . . . . . . . . . . . . . . . . . . .
II −Placement and Installation 16. . . . . . . . . . . . . . . . . . .
III−Start−Up 21. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
IV−Heating System Service Checks 22. . . . . . . . . . . . . .
V−Typical Operating Conditions 26. . . . . . . . . . . . . . . . .
VI−Maintenance 27. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
VII−Wiring and Sequence of Operation 30. . . . . . . . . . .
VIII−Troubleshooting 35. . . . . . . . . . . . . . . . . . . . . . . . . . .
CAUTION
As with any mechanical equipment, personal injury
can result from contact with sharp sheet metal
edges. Be careful when you handle this equipment.
WARNING
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.

Page 2
SPECIFICATIONS
Gas
Hti
ModelNo. G41UF−24B−045 G41UF−36B−045 G41UF−36B−070 G41UF−36C−090 G41UF−48C−090
Heating
Performance Input− Btuh (kW) 44,000 (12.9) 44,000 (12.9) 66,000 (19.3) 88,000 (25.8) 88,000 (25.8)
Performance
Output− Btuh (kW) 40,000 (11.7) 40,000 (11.7) 60,000 (17.6) 80,000 (23.4) 80,000 (23.4)
1AFUE 90.0% 90.0% 90.0% 90.0% 90.0%
Highstatic(CSA)− in.w.g. (Pa) 0.5 0.5 0.5 0.5 0.5
Temperature rise range − _F (_C) 35 − 65 (19 − 36) 25 − 55 (14 − 31) 35 − 65 (19 − 36) 50 − 80 (28 − 44) 45 − 75 (25 − 42)
Connections
in (mm)
Exhaust Pipe (PVC) 2 (51) 2 (51) 2 (51) 2 (51) 2 (51)
in. (mm) Condensate Drain (PVCPipe) − i.d. 1/2 (13) 1/2 (13) 1/2 (13) 1/2 (13) 1/2 (13)
Condensate Drain (PVC Coupling) − o.d. 3/4 (19) 3/4 (19) 3/4 (19) 3/4 (19) 3/4 (19)
GaspipesizeIPS 1/2 (13) 1/2 (13) 1/2 (13) 1/2 (13) 1/2 (13)
Indoor
Blower
Wheel nominal diameter x width −in. (mm) 10 x 7
(254 x 178)
10 x 8
(254 x 203)
10 x 8
(254 x 203)
10 x 8
(254 x 203)
10 x 10
(254 x 254)
Motoroutput − hp (W) 1/5 (149) 1/3 (249) 1/3 (249) 1/3 (249) 1/2 (373)
Tons(kW) ofaddoncooling 1 − 2 (3.5 − 7.0) 1 − 3 (3.5 − 10.5) 1 − 3 (3.5 − 10.5) 1 − 3 (3.5 − 10.5) 2 − 4 (7.0 − 14.0)
Shippingweight − 1 package 128 lbs. (58 kg) 131 lbs. (59 kg) 141 lbs (64 kg) 160 lbs. (73 kg) 164 lbs. (74 kg)
Electricalcharacteristics 120 volts − 60 hertz − 1 phase (less than 12 amps)
OPTIONAL ACCESSORIES – MUST BE ORDERED EXTRA
4Side Return Air Filter & Rack Kit − Number & size of
filters Single 44J22 or Ten Pack 66K63 − (1) 16 x 25 x 1 in. (406 x 635 x 25 mm)
EZ Filter
Base
Catalog Number − Shipping Weight 73P56 − 7 lbs. (3 kg) 73P57 − 8 lbs. (4 kg)
Base Dimensions − H x W x D − in. (mm) 4 x 17−5/8 x 28−5/8 (102 x 448 x 727) 4 x 21−5/8 x 28−5/8 (102 x 549 x 727)
Number and size of field provided filter − in. (mm) 16 x 25 x 1 (406 x 635 x 25) 20 x 25 x 1 (508 x 635 x 25)
Condensate
Drain Heat
6 ft. (1.8 m) long 26K68 26K68 26K68 26K68 26K68
D
ra
i
n
H
eat
Cable 24 ft. (7.3 m) long 26K69 26K69 26K69 26K69 26K69
50 ft. (15.2 m) long 26K70 26K70 26K70 26K70 26K70
Heat Cable
Tape
Fiberglass − 1/2 in. (38 mm) x 66 ft. (20 m) 39G04 39G04 39G04 39G04 39G04
T
ape
Aluminum foil − 2 in. (25 mm) x 60 ft. (18 m) 39G03 39G03 39G03 39G03 39G03
6High Altitude Orifice Kit − Natural Gas 47M82 47M82 47M82 47M82 47M82
3High Altitude
Pressure Switch Kit
4501−7500 ft. (1372−2286 m) − − − − − − − − − 46M94 46M94
Pressure
S
witch Kit 7501−10,000 ft. (2286−3048 m) 46M94 46M94 46M94 46M94 46M94
LPG/Propane Kit 0−7500 ft. (0−2286 m) 47M83 47M83 47M83 47M83 47M83
7501−10,000 ft. (2286−3048 m) 47M81 47M81 47M81 47M81 47M81
5Termination
Kits
Roof − 2 inch (51 mm) 15F75 15F75 15F75 15F75 15F75
Ki
ts Roof − 3 inch (76 mm) 44J41 44J41 44J41 44J41 44J41
Wall Ring − 2 inch (51 mm) 15F74 15F74 15F74 15F74 15F74
Twinning Kit 15L38 15L38 15L38 15L38 15L38
1Annual Fuel Utilization Efficiency based on DOE test procedures and according to FTC labeling regulations. Isolated combustion system rating for nonweatherized
furnaces.
3Required for proper operation at altitudes over 4500 ft. (1370 m).
4Cleanable polyurethane frame type filter.
5Kits contain enough parts for two installations. Determine from venting tables proper exhaust pipe size and termination kit required.
6Required for proper operation at altitudes from 7501 to 10,000 ft. (2286 to 3048 m).
NOTE − Filters and provisions for mounting are not furnished and must be field provided.

Page 3
SPECIFICATIONS
Gas
Hti
ModelNo. G41UF−60C−090 G41UF−48C−110 G41UF−60C−110 G41UF−60D−135
Heating
Performance Input− Btuh (kW) 88,000 (25.8) 110,000 (32.2) 110,000 (32.2) 132,000 (38.7)
Performance
Output− Btuh (kW) 80,000 (23.4) 100,000 (29.3) 100,000 (29.3) 120,000 (35.1)
1AFUE 90.0% 90.0% 90.0% 90.0%
Highstatic(CSA)− in.w.g. (Pa) 0.5 0.5 0.5 0.5
Temperature rise range − _F (_C) 25 − 55 (14 − 31) 50 − 80 (28 − 44) 40 − 70 (22 − 39) 45 − 75 (25 − 42)
Connections
in (mm)
Exhaust Pipe (PVC) 2 (51) 2 (51) 2 (51) 2 (51)
in. (mm) Condensate Drain (PVC Pipe) − i.d. 1/2 (13) 1/2 (13) 1/2 (13) 1/2 (13)
Condensate Drain (PVC Coupling) − o.d. 3/4 (19) 3/4 (19) 3/4 (19) 3/4 (19)
GaspipesizeIPS 1/2 (13) 1/2 (13) 1/2 (13) 1/2 (13)
Indoor
Blower Wheelnominaldiameter xwidth −in. (mm) 11−1/2 x 10 (292 x 229) 10 x 10 (254 x
254)
11−1/2 x 10 (292 x
229)
11−1/2 x 10 (292 x
229)
Motoroutput − hp (W) 3/4 (560) 1/2 (373) 3/4 (560) 3/4 (560)
Tons(kW) ofaddoncooling 4 − 5 (14.0 − 17.5) 2 − 4 (7.0 − 14.0) 4 − 5 (14.0 − 17.5) 4 − 5 (14.0 − 17.5)
Shippingweight − 1 package 168 lbs. (76 kg) 173 lbs. (78 kg) 177 lbs. (80 kg) 194 lbs. (88 kg)
Electricalcharacteristics 120 volts − 60 hertz − 1 phase (less than 12 amps)
OPTIONAL ACCESSORIES – MUST BE ORDERED EXTRA
4,6Air Filter and Rack Kit − Number & size of filters Single 44J22 or Ten Pack 66K63 − (1) 16 x 25 x 1 (406 x 635 x 25)
EZ Filter
Base
Catalog Number − Shipping Weight 73P57 − 8 lbs. (4 kg) 73P58 − 10 lbs. (5 kg)
Base Dimensions − H x W x D 4 x 21−5/8 x 28−5/8 in. (102 x 549 x 727 mm) 4 x 24−5/8 x 28−5/8 in. (102 x 625 x 727 mm)
Number and size of field provided filter 20 x 25 x 1 in. (508 x 635 x 25 mm) 24 x 24 x 1 in. (610 x 610 x 25 mm)
Condensate
Drain Heat
6 ft. (1.8 m) long 26K68 26K68 26K68 26K68
D
ra
i
n
H
eat
Cable 24 ft. (7.3 m) long 26K69 26K69 26K69 26K69
50 ft. (15.2 m) long 26K70 26K70 26K70 26K70
Heat Cable
Tape
Fiberglass − 1/2 in. (38 mm) x 66 ft. (20 m) 39G04 39G04 39G04 39G04
T
ape
Aluminum foil − 2 in. (25 mm) x 60 ft. (18 m) 39G03 39G03 39G03 39G03
7High Altitude Orifice Kit − Natural Gas Only 47M82 47M82 47M82 47M82
3High Altitude
Pressure Switch Kit
4501−7500 ft. (1372−2286 m) 46M94 46M94 46M94 − − −
Pressure
S
witch Kit 7501−10,000 ft. (2286−3048m) 46M94 46M94 46M94 46M95
RAB Return Air Base RAB60C (12M71)− − − − RAB60D (12M72)RAB60D (12M72)
LPG/Propane Kit 0−7500 ft. (0−2286 m) 47M83 47M83 47M83 47M83
7501−10,000ft. (2286−3048m) 47M81 47M81 47M81 47M81
5Termination
Kits
Roof − 2 inch (51 mm) 15F75 15F75 15F75 15F75
Ki
ts Roof − 3 inch (76 mm) 44J41 44J41 44J41 44J41
Wall Ring − 2 inch (51 mm) 15F74 15F74 15F74 15F74
Twinning Kit 15L38 15L38 15L38 15L38
1Annual Fuel Utilization Efficiency based on DOE test procedures and according to FTC labeling regulations. Isolated combustion system rating for nonweatherized
furnaces.
3Required for proper operation at altitudes over 4500 ft. (1370 m).
4Cleanable polyurethane frame type filter.
5Kits contain enough parts for two installations. Determine from venting tables proper exhaust pipe size and termination kit required.
6Not for use with RAB Return Air Base or with 60C and 60D size units with air flow requirements of 1800 cfm (850 L/s) or greater. See Blower Performance
tables for additional information.
7Required for proper operation at altitudes from 7501 to 10,000 ft. (2286 to 3048 m).
NOTE − Filters and provisions for mounting are not furnished and must be field provided.

Page 4
BLOWER PERFORMANCE
G41UF−24B−045 PERFORMANCE
External Static Air Volume / Watts at Different 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 1225 580 485 1000 470 365 820 385 290
0.10 25 1190 560 455 990 470 355 815 385 275
0.20 50 1160 545 435 970 460 340 805 380 265
0.30 75 1120 530 415 945 445 325 780 365 260
0.40 100 1070 505 395 910 430 305 755 355 245
0.50 125 1015 480 375 865 405 295 740 350 240
0.60 150 955 450 355 835 395 285 695 325 225
0.70 175 885 415 335 750 355 260 640 300 210
0.80 200 825 390 320 695 330 245 545 255 185
0.90 225 715 335 3000 600 285 220 435 205 170
NOTES − All air data is measured external to unit without filter (not furnished − field provided).
Air volume based on bottom air return air. Actual air volume may vary on side return air applications.
G41UF−36B−045 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
0.00 25 1555 735 630 1410 665 585 1190 560 520 1030 485 435
0.10 25 1515 715 605 1385 655 555 1190 560 485 1020 480 415
0.20 50 1470 695 580 1345 635 520 1170 550 455 1010 475 400
0.30 75 1410 665 555 1310 620 495 1155 545 440 1000 470 385
0.40 100 1350 640 535 1250 590 465 1120 530 410 980 465 360
0.50 125 1290 610 505 1205 570 450 1080 510 390 950 450 345
0.60 150 1220 575 485 1145 540 420 1020 480 365 905 430 320
0.70 175 1145 540 460 1080 510 400 975 460 345 860 405 300
0.80 200 1050 495 425 985 465 365 870 410 320 785 370 285
0.90 225 945 445 410 900 425 345 825 390 305 730 345 270
NOTES − All air data is measured external to unit without filter (not furnished − field provided).
Air volume based on bottom air return air. Actual air volume may vary on side return air applications.
G41UF−36B−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
0.00 0 1640 775 660 1415 665 575 1160 545 485 1005 475 410
0.10 25 1600 755 635 1395 660 550 1160 545 460 1000 470 385
0.20 50 1540 725 605 1370 650 525 1160 545 445 995 470 375
0.30 75 1495 705 580 1345 635 505 1145 540 425 990 465 365
0.40 100 1420 670 545 1275 605 480 1125 530 395 965 455 345
0.50 125 1360 640 525 1245 590 450 1080 510 375 945 445 325
0.60 150 1275 600 490 1165 550 410 1025 485 350 900 425 305
0.70 175 1170 555 465 1085 515 385 965 430 335 860 405 295
0.80 200 1080 510 440 1010 475 360 865 410 310 775 365 270
0.90 225 945 445 400 840 395 320 765 360 275 710 335 245
NOTES − All air data is measured external to unit without filter (not furnished − field provided).
Air volume based on bottom air return air. Actual air volume may vary on side return air applications.
G41UF−36C−090 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
0.00 0 1705 805 730 1395 660 605 1195 555 495 1010 475 410
0.10 25 1680 795 700 1390 650 585 1185 560 480 1005 475 395
0.20 50 1645 775 675 1380 650 560 1175 555 465 1000 470 390
0.30 75 1600 755 635 1365 645 535 1165 550 445 995 470 375
0.40 100 1560 735 615 1345 635 515 1155 545 425 990 465 360
0.50 125 1495 705 580 1305 615 500 1125 530 400 970 460 345
0.60 150 1415 665 540 1270 600 475 1080 510 375 940 445 320
0.70 175 1330 630 505 1205 570 435 1035 490 360 890 420 300
0.80 200 1255 590 485 1120 530 400 955 450 330 840 395 280
0.90 225 1135 535 450 1020 480 365 830 390 300 760 360 260
NOTES − All air data is measured external to unit without filter (not furnished − field provided).
Air volume based on bottom air return air. Actual air volume may vary on side return air applications.

Page 5
BLOWER PERFORMANCE
G41UF−48C−090 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
0.00 0 2180 1030 930 1835 865 790 1520 715 630 1280 605 510
0.10 25 2135 1005 885 1825 860 750 1510 710 610 1275 600 495
0.20 50 2085 985 840 1810 855 720 1505 710 580 1270 600 475
0.30 75 2030 955 800 1775 835 685 1500 705 565 1265 595 460
0.40 100 1940 915 760 1735 820 650 1480 700 535 1250 590 440
0.50 125 1865 880 725 1660 785 600 1430 675 505 1215 575 425
0.60 150 1740 820 670 1590 750 575 1380 650 475 1175 555 410
0.70 175 1645 775 640 1475 695 520 1290 610 450 1105 520 375
0.80 200 1540 725 600 1340 630 465 1175 555 405 1020 480 355
0.90 225 1335 630 540 1170 555 440 1070 505 375 950 450 330
NOTES − All air data is measured external to unit without filter (not furnished − field provided).
Air volume based on bottom air return air. Actual air volume may vary on side return air applications.
G41UF−60C−090 PERFORMANCE − Single Side Return Air − Air volumes in bold require field fabricated transition to ac
commodate 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
0.00 02510 1185 1160 2350 1110 990 2145 1010 850 1785 845 670
0.10 25 2460 1160 1145 2310 1090 970 2095 990 825 1780 840 660
0.20 50 2395 1130 1125 2240 1060 940 2060 970 805 1760 830 650
0.30 75 2325 1095 1090 2175 1025 910 2015 950 775 1735 820 630
0.40 100 2225 1050 1050 2110 995 880 1950 920 745 1720 810 620
0.50 125 2135 1010 1015 2050 965 855 1900 895 725 1665 785 600
0.60 150 2025 955 975 1950 920 820 1820 860 700 1600 755 575
0.70 175 1950 920 950 1865 880 790 1750 825 675 1535 725 555
0.80 200 1845 870 915 1760 830 755 1640 775 650 1450 685 530
0.90 225 1730 815 885 1640 775 720 1555 735 625 1340 630 510
NOTES − All air data is measured external to unit without filter (not furnished − field provided).
G41UF−60C−090 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
0.00 0 2575 1215 1235 2360 1115 1030 2050 965 875 1790 845 720
0.10 25 2525 1195 1210 2320 1095 1010 2040 960 855 1775 835 710
0.20 50 2450 1155 1170 2270 1070 985 2025 955 840 1755 830 695
0.30 75 2375 1120 1140 2215 1045 955 1995 940 815 1740 820 680
0.40 100 2300 1085 1125 2155 1020 930 1970 930 800 1720 815 665
0.50 125 2210 1045 1075 2090 985 900 1915 905 775 1700 800 650
0.60 150 2140 1010 1030 2055 970 895 1875 885 755 1665 785 635
0.70 175 2080 980 1035 1975 935 865 1805 855 730 1610 760 615
0.80 200 2000 945 1010 1890 890 830 1730 815 705 1565 740 595
0.90 225 1905 900 970 1785 845 800 1640 775 675 1495 705 570
NOTES − All air data is measured external to unit without filter (not furnished − field provided).
G41UF−48C−110 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
0.00 0 2160 1020 880 1880 890 755 1490 705 602 1235 580 485
0.10 25 2100 990 850 1855 875 730 1480 700 585 1230 580 475
0.20 50 2035 960 805 1815 860 690 1475 695 560 1225 580 460
0.30 75 1965 925 750 1755 830 650 1475 695 545 1220 575 445
0.40 100 1885 890 725 1715 810 625 1465 690 510 1215 575 430
0.50 125 1780 840 680 1630 770 580 1420 670 490 1150 540 400
0.60 150 1690 800 660 1550 735 550 1360 640 460 1110 525 380
0.70 175 1575 745 620 1410 665 505 1210 570 405 1035 490 350
0.80 200 1375 650 550 1230 580 450 1125 530 380 970 460 325
0.90 225 1225 580 520 1120 530 415 1050 495 365 885 420 310
NOTES − All air data is measured external to unit without filter (not furnished − field provided).
Air volume based on bottom air return air. Actual air volume may vary on side return air applications.

Page 6
BLOWER PERFORMANCE
G41UF−60C−110 PERFORMANCE − Single Side Return Air − Air volumes in bold require field fabricated transition to ac
commodate 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
0.00 02550 1205 1300 2345 1105 1080 2055 970 895 1740 820 715
0.10 25 2500 1180 1270 2280 1075 1050 2025 950 855 1730 815 720
0.20 50 2410 1140 1225 2220 1050 1000 2000 945 840 1715 810 695
0.30 75 2350 1110 1190 2175 1025 965 1945 920 805 1690 795 670
0.40 100 2280 1075 1170 2115 995 940 1910 900 790 1675 790 680
0.50 125 2195 1035 1115 2035 960 910 1840 870 760 1630 770 650
0.60 150 2075 980 1065 1955 925 875 1785 845 735 1585 750 630
0.70 175 1980 935 1030 1860 880 845 1705 805 700 1540 725 605
0.80 200 1895 895 1005 1770 835 810 1615 765 675 1475 695 580
0.90 225 1770 835 975 1640 775 770 1535 725 645 1415 670 565
NOTES − All air data is measured external to unit without filter (not furnished − field provided).
G41UF−60C−110 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
0.00 0 2580 1215 1340 2330 1100 1100 2045 965 950 1760 830 745
0.10 25 2515 1190 1295 2295 1085 1075 2040 960 880 1740 820 745
0.20 50 2450 1155 1255 2255 1065 1040 2005 945 855 1735 820 730
0.30 75 2375 1120 1225 2200 1040 1015 1965 925 835 1715 810 710
0.40 100 2310 1090 1190 2145 1010 975 1925 910 815 1690 800 695
0.50 125 2200 1040 1135 2085 985 955 1870 880 780 1660 785 670
0.60 150 2130 1005 1105 2025 955 930 1825 860 770 1600 755 650
0.70 175 2045 965 1065 1930 910 890 1750 825 730 1575 745 625
0.80 200 1930 910 1025 1825 860 850 1650 780 695 1500 710 600
0.90 225 1820 860 980 1730 815 815 1555 735 660 1430 675 580
NOTES − All air data is measured external to unit without filter (not furnished − field provided).
G41UF−60D−135 PERFORMANCE − Single Side Return Air − Air volumes in bold require field fabricated transition to ac
commodate 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
0.00 02550 1205 1340 2330 1100 1145 2035 960 955 1725 815 775
0.10 25 2490 1175 1305 2275 1075 1100 2025 955 900 1720 810 755
0.20 50 2430 1145 1285 2230 1050 1065 1990 940 890 1715 810 740
0.30 75 2355 1110 1235 2180 1030 1035 1955 920 855 1700 800 715
0.40 100 2285 1080 1210 2140 1010 1010 1910 900 830 1680 790 700
0.50 125 2200 1040 1160 2070 975 980 1865 880 805 1645 775 675
0.60 150 2100 990 1110 1985 935 935 1815 855 780 1600 755 660
0.70 175 2010 950 1075 1915 905 910 1740 820 740 1545 730 630
0.80 200 1910 900 1050 1845 870 875 1670 790 720 1490 705 605
0.90 225 1815 855 1005 1735 820 835 1605 755 690 1420 670 580
NOTES − All air data is measured external to unit without filter (not furnished − field provided).
G41UF−60D−135 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
0.00 0 2585 1220 1370 2355 1110 1160 2075 980 985 1730 820 765
0.10 25 2530 1195 1335 2330 1100 1120 2075 980 945 1730 820 750
0.20 50 2475 1170 1300 2295 1085 1090 2050 970 920 1730 815 745
0.30 75 2410 1135 1260 2230 1050 1060 2010 950 890 1715 810 725
0.40 100 2355 1110 1230 2185 1030 1040 1975 930 865 1680 795 695
0.50 125 2275 1075 1190 2120 1000 995 1915 905 830 1650 780 685
0.60 150 2190 1035 1155 2045 965 960 1850 875 805 1615 765 660
0.70 175 2100 990 1125 1955 925 930 1785 840 780 1550 730 635
0.80 200 1995 945 1080 1855 875 890 1715 810 745 1500 710 615
0.90 225 1860 880 1020 1750 825 835 1635 770 720 1425 670 580
NOTES − All air data is measured external to unit without filter (not furnished − field provided).

Page 7
G41UF PARTS IDENTIFICATION
FIGURE 1
TOP CAP
CABINET
BURNER BOX
ASSEMBLY
GAS VALVE AND
MANIFOLD
SIGHT
GLASS
DuralokPlusTM
HEAT EXCHANGER
ASSEMBLY
CONDENSER COIL
CONTROL BOX
DOOR
INTERLOCK
SWITCH
COLD HEADER
(COLLECTOR)
BOX
COMBUSTION AIR
INDUCER
BLOWER
ACCESS
DOOR
BURNER
ACCESS
PANEL
FLUE
COLLAR
COMBUSTION AIR
PROVE
(PRESSURE)
SWITCH
PRIMARY LIMIT
WARM HEADER
(COLLECTOR)
BOX

Page 8
I−UNIT COMPONENTS
G41UF unit components are shown in figure 1. The com
bustion air inducer, gas valve and burners can be accessed
by removing the burner access panel. The blower and con
trol box can be accessed by removing the blower access
door. G41UF units are designed for bottom and side re
turn air.
A−MakeUp Box (Figure 2)
A field makeup box is provided for line voltage wiring. Line
voltage wiring to unit is routed from the make up box. The
hot" wire is connected to the door switch and then from the
switch to the SureLight board. The make−up box may be
installed inside or outside the unit and on the unit left or right
side (right side shown figure 2).
FIGURE 2
INTERIOR MAKE−UP BOX INSTALLATION
MAKE−UP
BOX
Right Side
CLAMP LOCATION
B−Control Box Components (Figure 3)
Unit transformer (T1) and SureLight control (A92) are lo
cated in the control box. In addition, a door interlock switch
(S51) is located in the control box.
FIGURE 3
DOOR INTERLOCK
SWITCH (S51)
SURELIGHT
CONTROL
BOARD
(A92)
TRANSFORMER
(T1)
1. Control Transformer (T1)
A transformer located in the control box provides power to
the low voltage 24 volt section of the unit. Transformers on
all models are rated 40VA with a 120V primary and a 24V
secondary.
2. Door Interlock Switch (S51)
A door interlock switch rated 14A at 120VAC is located on
the control box. The switch is wired in series with line volt
age. When the blower door is removed the unit will shut
down.
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. Furnace Control (A92)
All G41UF model units are equipped with the Lennox Sur
eLight ignition system. The system consists of ignition
control board (figure 5 with control terminal designations
in table 3), ignitor (figure 6) and sensor (figure 7). The
board and ignitor work in combination to ensure furnace
ignition and ignitor durability. The SureLight integrated
board controls all major furnace operations. The board
also features two LED lights for troubleshooting and two
accessory terminals rated at (1) one amp. Tables 1 and 2
show jack plug terminal designations. See table 4 for trou
bleshooting diagnostic codes. The SureLight ignitor is
made of durable silicon−nitride. Ignitor longevity is also
enhanced by voltage ramping by the control board. The
board finds the lowest ignitor temperature which will suc
cessfully light the burner, thus increasing the life of the ig
nitor.
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 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

Page 9
TABLE 1
SureLight BOARD J156 (J2) TERMINAL
DESIGNATIONS
PIN # FUNCTION
1Combustion Air Inducer Line
2Ignitor Line
3Combustion Air Inducer Neutral
4Ignitor Neutral
TABLE 2
SureLight BOARD J58 (J1) TERMINAL
DESIGNATIONS
PIN # FUNCTION
1High Limit Output
2Not Used
324V Line
4Not Used
5Rollout Switch In
624V Neutral
7High Limit Input
8Ground
9Gas Valve In
10 Pressure Switch Out
11 Rollout Switch Out
12 Gas Valve Out
a−Electronic Ignition (See Figure 8)
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 prove 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. The ignitor
stays energized during the 4 second trial until flame is
sensed. If ignition is not proved during the 4−second period,
the control 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. Each time
120V is removed and then re−applied, the control re−starts
the learning process.
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 setting 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 4.
FANOFF TIME ADJUSTMENT
To adjust fan−off timing, flip dip switch to desired setting.
60sec. 90sec. 120sec. 180sec.
(Black square indicates switch position)
OFF OFFOFF OFF ON
ON
ON
ON
OFF
OFF
OFF
OFF
2
2
2 2
1
1
1
1
FIGURE 4

Page 10
SURELIGHT INTEGRATED CONTROL BOARD
FIGURE 5
J156
J58
XFMR–N
TABLE 3
TERMINAL DESIGNATIONS
COOL−H 120V HOT Blower Cooling Speed (120VAC)
HEAT−H Blower Heating Speed−(120VAC)
EAC−H Electronic Air Cleaner (120VAC)
HUM−H Humidifier (120VAC)
XFMR−H Transformer (120VAC)
LINE−H Input (120VAC)
LINE−N 120V NEUT Input (Neutral)
HUM−N Humidifier (Neutral)
EAC−N Electronic Air Cleaner (Neutral)
XFMR−N Transformer (Neutral)
CIR−N Blower (Neutral)
PARK Alternate Blower Speeds (dead)
(FLAME SENSE) Flame Sensor
4. Ignitor (Figure 6)
The SureLight ignitor is made of durable silicon nitride. Ig
nitor longevity is enhanced by controlling voltage to the ig
nitor. The board finds the lowest ignitor temperature which
will successfully light the burner, thus increasing the life of
the ignitor. Due to this feature of the board, voltage cannot
be measured so ignitor must be ohmed. Ohm value should
be 10.9 to 19.7
FIGURE 6
13/32’
5/8"
SureLight Ignitor Location
BURNERS FRONT VIEW
MEASUREMENT IS TO I.D.
OF RETENTION RING
IGNITOR
BRACKET
5. Flame Sensor (Figure 7)
A flame sensor is located on the left side of the burner sup
port. The sensor is mounted on the bottom burner box plate
and the tip protrudes into the flame envelope of the left−
most burner. The sensor can be removed for service with
out removing any part of the burners. During operation,
flame is sensed by current passed through the flame and
sensing electrode. The SureLight control allows the gas
valve to remain open as long as flame signal is sensed.
NOTE − The G41UF furnace contains electronic com
ponents that are polarity sensitive. Make sure that the
furnace is wired correctly and is properly grounded.
FIGURE 7
NORMAL FLAME SIGNAL > 0.18 MICROAMPS
LOW FLAME SIGNAL < 0.17 MICROAMPS
DROP OUT SIGNAL = 0.15 MICROAMPS
5/16"