Lennox G26Q2-50, G26Q4/5-75, G26Q3/4-100, G26Q4/5-100, G26Q3-50 Unit Information

...

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LENNOXOEMPARTS.COM

Service Literature

G26 SERIES UNITS

G26series unitsarehigh-efficiencyupflowgas furnacesmanufactured with DuralokPlust aluminizedsteelclamshell-type heat exchangers. G26units are available in heating capacities of 50,000 to 125,000 Btuh and cooling applications upto5 tons. Refer toEngineeringHandbook for proper sizing.

Unitsare factoryequipped foruse with naturalgas. Akit isavailable forconversion to LPGoperation.G26-1 and -2model unitsuse electronic(intermittent pilot) ignition. G26-3, -4, -5 and -6 model units feature the Lennox SureLightT silicon nitrideignitionsystem.Each unitmeets theCalifornia Nitrogen Oxides (NOx) Standards and California Seasonal Efficiency requirements without modification. All units use a redundant gas valve to assure safety shut-off as required by A.G.A. or C.G.A.

Information containedin this manualis intendedforuse byqualifiedservice technicians only. All specifications are subject to change. Procedures outlinedin thismanual arepresented asa recommendationonly anddo notsupersede or replace local or state codes. In the absence of local or state codes,the guidelinesand proceduresoutlined inthis manual(except where noted) are recommended only.

G26

Corp. 9721-L11

Revised 07-2001

G26 FURNACEY

FIGURE 1

AG26 HEAT EXCHANGE ASSEMBLY

Combustion Process:

1. A call for heat starts the combustion air blower.

2. Outdoorairisdrawnthroughpipeintotheburner compartment where it mixes with gas in a conventional style inshot burner.

3. TheSureLightignitionsystemlightstheburners.

4. Combustion products are drawn downward through the heat exchanger. Heat is extracted as indoor air passes across theoutside surface of the metal.

5. Latent heat is removed from the combustion productsasairpassesthroughthecoil.Condensate (water) isformed as the combustion products cool.

6. As the combustion products exit the coil, condensate is collected and drained away.

7. Combustion products are pulled from the heat exchanger and forced into the flue.

Page 1

ã 1997 Lennox Industries Inc.

Litho U.S.A.

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LENNOXOEMPARTS.COM

SPECIFICATIONS

GasPipingSizeI.P.S.

Blowerwheelnomina

Nominalcoolin

Vent/IntakeAirRoo

15F74

(ringkit)

—

22G44

(closecouple)

—30G2

(WTKclosecouple

)

TerminationKit(optional)—ventsize

TwinningKit

Model No. G26Q2-50 G26Q3-50 G26Q3-75 G26Q4/5-75

Input Btuh(kW) 50,000 (14.7) 75,000 (22.0)

Output Btuh (kW) 46,000 (13.5) 47,000 (13.8) 70,000(20.5) 69,000 (20.2)

lA.F.U.E. 92% 92.4% 92.0% 92.0%

California Seasonal Efficiency 85.9% 86.5% 86.3% 83.8%

¡Exhaust pipe connection (PVC) diameter— in. (mm) 2 (51)

¡Intake pipe connection (PVC) diameter— in. (mm) 2 (51)

Condensate drain connection ( PVC)— in. (mm) 1/2 (12.7)

Temperature rise range — _F (_C) 40-70 (22-39) 30-60 (17-33) 40-70 (22-39) 20-50 (11-28)

High static certified by (A.G.A./C.G.A.) — in. wg. (Pa) .50 (125)

in. 1/2

Natural orLPG/propane

diameter x width

mm 12.7

in. 10 x 7 10 x 8 11-1/2 x 9

mm 254 x 178 254 x 203 292 x 229

Blower motor output — hp (W) 1/5 (149) 1/3 (249) 3/4 (560)

Tons 1 to2 2 to 3 3-1/2 to5

that can be added

Shipping weight — lbs. (kg) 1 package 150 (68) 157 (71) 157 (71) 182 (83)

Electrical characteristics 120 volts — 60 hertz — 1 phase (all models) (less than 12 amps)

kW 3.5 to 7.0 3.5 to 10.6 12.3 to 17.6

b Optional Accessories (Must Be Ordered Extra) b

LPG/Propane kit (optional) 65K27 (all models)

Filter and Filter Rack Kits }No. & sizeof filters - in. (mm)

Concentric Vent/Intake Air/Roof Termination Kit (optional) 60G77 — 1 1/2 inch (38 mm)

2 inch (51 mm) 15F75

Termination Kit (optional) — vent size

¡Vent/Intake Air Wall

3 inch (76 mm) 44J41

2 inch (51 mm)

Single (44J20) Ten Pack (66K61)

(1) 14 x 25 x 1 (356 x 635 x 25)

30G79 (WTKX close cou ple with extension riser)

Single (44J21)

Ten Pack (66K62)

(1) 20 x 25 x 1

(508 x 635 x 25)

3 inch (76 mm) 44J40 (close cou ple) or 81J20 (WTK close cou ple)

Non-continuous low speed 64H88 (all models)

(optional)

Continuous Low Speed Blower Switch (optional) 44J06 (-1and -2 models) N ot used with Twinning Kits

lAnnual Fuel Utilization Efficiency b ased on U.S. DOE test procedures and FT C labeling regulations. Isolated combu stion system rating for non-weatherized furnaces. }Polyurethane frame type filter. ¡Determine fromventingtables proper intake and exhaust pipe size andtermination kitrequired.

Continuous low speed 35J93 (all models)

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LENNOXOEMPARTS.COM

SPECIFICATIONS

GasPipingSizeI.P.S.

Blowerwheelnomina

Nominalcoolin

Vent/IntakeAirRoo

TerminationKit(optional)—ventsize

TwinningKit

Model No. G26Q3/4-100 G26Q4/5-100 G26Q3/4-125 G26Q4/5-125

Input Btuh (kW) 100,000 (29.3) 125,000 (36.6) Output Btuh (kW) 91,000 (26.7) 93,000 (27.2) 115,000 ( 33.7) 116,000 (34.0) lA.F.U.E. 92.0% 92.0% 91.0% 92.0% California Seasonal Efficiency 86.6% 85.8% 87.5% 87.0%

¡Exhaust pipe connection (PVC) diameter— in. (mm) 2 (51) ¡Intake pipe connection (PVC) diameter— in. (mm) 3 (76)

Condensate drain connection ( PVC)— in. (mm) 1/2 (12.7) Temperature rise range — _F (_C) 50-80 (28-44) 40-70 (22-39) 55-85 (31-47) 50-80 (28-44) High static certified by (A.G.A./C.G.A.) — in. wg. (Pa) .50 (125)

in. 1/2

Natural orLPG/propane

diameter x width

Blower motor output — hp (W) 1/2 (373) 3/4 (560) 1/2 (373) 3/4 (560)

that can be added

Shipping weight — lbs. (kg) 1 package 186 (84) 198 (90) 218 (99) 218 (99) Electrical characteristics 120 volts — 60 hertz — 1 phase (all models) (less than 12 amps)

LPG/Propane kit (optional) 65K27 (all models) Filter and Filter Rack Kits

}No. & sizeof filters - in. (mm) Concentric Vent/Intake Air/Roof Termination Kit (optional) 33K97 — 2 inch ( 51 mm)

Termination Kit (optional) — vent size

¡Vent/Intake Air Wall

Non-continuous low speed 64H88 (all models)

(optional)

Continuous Low Speed Blower Switch (optional) 44J06 (-1and -2 models) N ot used with Twinning Kits

NOTE - 2 inch x 3 inch (51 mm x 76 mm) adaptor is furnished with -100 and -125 furnaces for exhaust pipe connection.

Continuous low speed 35J93 (all models)

mm 12.7 in. 10 x 10 11-1/2 x 9 10 x 10 11-1 /2 x 9 mm 254 x 254 292 x 229 254 x 254 292 x 229

Tons 2 to4 3-1/2 to 5 2 to 4 3- 1/2 to 5 kW 7.0 to 14.1 12.3 to17.6 7.0 to14.1 12.3 to 17.6

b Optional Accessories (Must Be Ordered Extra) b

Single (44J21) Ten Pack (66K62)

(1) 20 x 25 x 1 (508 x 635 x 25)

2 inch (51 mm) 15F75 3 inch (76 mm) 44J41

2 inch (51 mm) 3 inch (76 mm) 44J40 (close couple) — 81J20 (WTK close couple)

15F74 (ring kit) — 22G44 (close couple) — 30G28 (WTK close couple)

30G79 (WTKX close cou ple with extension riser)

BLOWER PERFORMANCE DATA

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)

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LENNOXOEMPARTS.COM

BLOWER PERFORMANCE DATA

External Static

G26Q2Ć50 BLOWER PERFORMANCE

External Static

Pressure

in. w.g. Pa cfm L/s Watts cfm L/s Watts cfm L/s Watts

0 0 1115 525 495 885 415 360 720 340 280

.10 25 1095 515 475 880 415 350 700 330 265 .20 50 1065 505 465 855 405 340 680 320 260 .30 75 1035 490 445 830 390 325 660 310 250 .40 100 995 470 425 755 355 315 645 305 235 .50 125 950 450 405 755 355 300 625 295 225 .60 150 900 425 390 740 350 280 540 255 215 .70 175 815 385 365 660 310 255 530 250 205 .80 200 610 290 340 585 275 240 360 170 180 .90 225 590 280 315 390 185 215 Ć Ć Ć Ć Ć Ć Ć Ć Ć Ć Ć Ć

NOTE Ċ 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.

High Medium Low

G26Q3Ć50 BLOWER PERFORMANCE

External Static

Pressure

in. w.g. Pa cfm L/s Watts cfm L/s Watts cfm L/s Watts cfm L/s Watts

0 0 1485 700 590 1275 600 485 1045 495 390 840 395 310 .10 25 1445 680 565 1250 590 460 1030 485 375 830 390 300 .20 50 1390 655 545 1225 580 445 1010 475 365 815 385 290 .30 75 1345 635 520 1190 560 425 985 465 345 790 375 285 .40 100 1290 610 500 1150 545 405 955 450 335 780 370 275 .50 125 1225 580 480 1095 515 385 920 435 315 735 345 255 .60 150 1160 545 460 1030 485 365 875 415 300 700 330 240 .70 175 1075 505 440 950 450 345 855 405 280 600 285 220 .80 200 975 460 415 865 410 315 645 305 250 510 240 195 .90 225 845 400 385 615 290 265 545 255 225 375 175 180

NOTE Ċ 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.

High MediumĆHigh MediumĆLow Low

Air Volume and Motor Watts at Specific Blower Taps

G26Q3Ć75 BLOWER PERFORMANCE

External Static

Pressure

in. w.g. Pa cfm L/s Watts cfm L/s Watts cfm L/s Watts cfm L/s Watts

0 0 1490 705 650 1340 630 540 1060 500 440 870 410 360 .10 25 1435 675 625 1305 615 515 1050 495 425 865 410 350 .20 50 1385 655 605 1260 595 490 1025 485 405 850 400 335 .30 75 1330 630 580 1215 575 470 1000 470 385 835 395 325 .40 100 1260 595 560 1160 545 445 965 455 365 810 380 310 .50 125 1200 565 540 1100 520 420 920 435 345 770 365 290 .60 150 1125 530 515 1035 490 400 870 410 325 735 345 280 .70 175 1035 490 495 960 455 375 780 370 305 685 325 265 .80 200 935 440 475 865 410 345 725 340 285 Ć Ć Ć Ć Ć Ć Ć Ć Ć Ć Ć Ć .90 225 805 380 445 630 295 295 540 255 240 Ć Ć Ć Ć Ć Ć Ć Ć Ć Ć Ć Ć

NOTE Ċ 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.

High MediumĆHigh MediumĆLow Low

Air Volume and Motor Watts at Specific Blower Taps

G26Q4/5Ć75 BLOWER PERFORMANCE

External Static

Pressure

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 2415 1140 1240 2120 1000 1015 1875 885 855 1635 770 705 1430 675 585

.10 25 2330 1100 1200 2090 985 1005 1835 865 835 1615 760 700 1420 670 585 .20 50 2265 1070 1165 2045 965 990 1795 845 815 1580 745 690 1390 655 580 .30 75 2210 1045 1145 2000 945 970 1765 835 810 1545 730 675 1365 645 575 .40 100 2145 1010 111 0 1950 920 955 1720 810 795 1510 715 670 1340 630 570 .50 125 2075 980 1085 1885 890 930 1680 795 785 1475 695 665 1310 620 565 .60 150 2000 945 1060 1825 860 910 1630 770 770 1435 675 655 1270 600 555 .70 175 1935 915 1040 1775 840 895 1565 740 755 1395 660 645 1220 575 545 .80 200 1840 870 1005 1705 805 870 1515 715 745 1345 635 630 1165 550 535 .90 225 1760 830 980 1610 760 845 1455 685 725 1275 600 615 111 0 525 530

NOTE Ċ 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.

High MediumĆHigh Medium MediumĆLow Low

Air Volume and Motor Watts at Specific Blower Taps

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LENNOXOEMPARTS.COM

BLOWER PERFORMANCE DATA

External Static

G26Q3/4Ć100 BLOWER PERFORMANCE

External Static

Pressure

in. w.g. Pa cfm L/s Watts cfm L/s Watts cfm L/s Watts cfm L/s Watts

0 0 2065 975 920 1760 830 735 1570 740 655 1245 590 520 .10 25 2000 945 875 1730 815 705 1550 730 625 1240 585 490

.20 50 1925 910 845 1685 795 675 1515 715 590 1225 580 470 .30 75 1840 870 800 1625 765 630 1475 695 565 1210 570 455 .40 100 1740 820 760 1550 730 595 1415 670 535 1165 550 430 .50 125 1650 780 730 1460 690 560 1335 630 500 1110 525 405 .60 150 1545 730 700 1370 645 530 1260 595 475 1045 495 385 .70 175 1420 670 660 1250 590 495 1170 550 445 950 450 355 .80 200 1270 600 620 1110 525 445 1025 485 395 825 390 325 .90 225 1045 495 560 965 455 405 885 420 360 700 330 290

NOTE Ċ 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.

High MediumĆHigh MediumĆLow Low

G26Q4/5Ć100 BLOWER PERFORMANCE

External Static

Pressure

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 2400 1135 1255 2185 1030 1070 1940 915 905 1740 820 765 1570 740 665 .10 25 2350 111 0 1230 2150 1015 1055 1920 905 885 1710 805 755 1525 720 645 .20 50 2290 1080 1185 2105 995 1025 1875 885 865 1685 795 740 1505 710 640 .30 75 2225 1050 1170 2060 970 1005 1845 870 850 1655 780 730 1485 700 630 .40 100 2165 1020 1130 2010 950 985 1805 850 835 1620 765 720 1450 685 620 .50 125 2105 995 1115 1950 920 960 1755 830 810 1585 750 700 1415 670 605 .60 150 2040 965 1080 1895 895 940 1700 800 790 1540 725 690 1380 650 595 .70 175 1955 925 1045 1820 860 915 1640 775 775 1475 695 670 1340 630 590 .80 200 1850 875 1005 1730 815 885 1580 745 755 1430 675 660 1290 610 580 .90 225 1770 835 985 1650 780 855 1505 710 740 1370 645 645 1225 580 565

NOTE Ċ 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.

High MediumĆHigh Medium MediumĆLow Low

Air Volume and Motor Watts at Specific Blower Taps

G26Q3/4Ć125 BLOWER PERFORMANCE

External Static

Pressure

in. w.g. Pa cfm L/s Watts cfm L/s Watts cfm L/s Watts cfm L/s Watts

0 0 2070 975 920 1735 820 725 1555 735 640 1235 585 500 .10 25 2010 950 885 1710 805 700 1535 725 625 1225 580 490 .20 50 1950 920 850 1675 790 680 1500 710 600 1210 570 470 .30 75 1975 930 820 1620 765 645 1465 690 575 1185 560 455 .40 100 1785 840 775 1560 735 615 1415 670 545 1140 540 435 .50 125 1700 800 745 1475 695 575 1345 635 520 1090 515 415 .60 150 1585 750 705 1410 665 555 1275 600 490 1035 490 390 .70 175 1475 695 675 1310 620 515 1185 560 460 975 460 370 .80 200 1350 635 640 1200 565 485 1090 515 425 865 410 340 .90 225 1200 565 595 1080 510 445 965 455 385 715 335 300

NOTE Ċ 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.

High MediumĆHigh MediumĆLow Low

Air Volume and Motor Watts at Specific Blower Taps

G26Q4/5Ć125 BLOWER PERFORMANCE

External Static

Pressure

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 2400 1135 1210 2175 1025 1040 1965 925 895 1790 845 780 1610 760 670

.10 25 2315 1090 1175 2125 1005 1025 1930 910 875 1760 830 770 1580 745 660 .20 50 2255 1065 1150 2080 980 1000 1880 885 860 1740 820 755 1550 730 645 .30 75 2195 1035 1130 2030 960 975 1840 870 835 1710 805 750 1520 715 635 .40 100 2120 1000 1100 1970 930 960 1790 845 815 1665 785 730 1495 705 630 .50 125 2050 965 1080 1910 900 934 1745 825 800 1620 765 715 1460 690 620 .60 150 1985 935 1050 1840 870 905 1685 795 785 1565 740 705 1415 670 610 .70 175 1885 890 1020 1770 835 890 1635 765 775 1515 715 685 1370 645 595 .80 200 1815 855 1005 1690 800 860 1570 740 750 1450 685 670 1315 620 580 .90 225 1735 820 980 1615 760 835 1485 700 725 1385 655 655 1245 590 565

NOTE Ċ 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.

High MediumĆHigh Medium MediumĆLow Low

Air Volume and Motor Watts at Specific Blower Taps

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INTAKE and EXHAUST PIPE VENTING TABLE

Nominal

Internal

Vent Pipe

Maximum

Equivalent Length

50,000 Btuh (14.7 kW) 75,000 Btuh (22.0 kW) 100,000 Btuh (29.3 kW) 125,000 Btuh (36.6 kW)

Minimum Vent Pipe Diameter Required

Feet Meters in. mm in. mm in. mm in. mm

15 4.6 1Ć1/2 38 2 51 2 51 2 51

20 6.1 2 51 2 51 2 51 3 76

25 7.6 2 51 2 51 2 51 3 76

30 9.1 2 51 2 51 3 51 3 76

40 12.2 2 51 2 51 3 51 3 76

50 15.2 2 51 2 51 3 51 3 76

55 16.8 2 51 2 51 3 76 3 76

60 18.3 3 76 3 76 3 76 3 76

70 21.3 3 76 3 76 3 76 3 76

80 24.4 3 76 3 76 3 76 3 76

90 27.4 3 76 3 76 3 76 3 76

100 30.5 3 76 3 76 3 76 3 76

110 33.5 3 76 3 76 3 76 3 76

120 36.6 3 76 3 76 3 76 3 76

130 39.6 3 76 3 76 3 76 Ć Ć Ć Ć Ć Ć Ć Ć

MINIMUM PIPE LENGTHS FOR FURNACES Ċ G26Ć50 Ċ 5 feet (1.5 m) with two 90 elbows of 1Ć1/2 inch (38 mm) diameter pipe. (15 equivalent feet (4.6 m) total).

VENTING NOTES Ċ One 90elbow is equivalent to 5 feet (1.5 m) of straight vent pipe.

Two 45 elbows are equal to one 90 elbow. One 45 elbow is equivalent to 2.5 feet (.75 m) of straight vent pipe. One foot (305 mm) length of 2 in. (51 mm) diameter pipe is equivalent to 8 feet (2.4 m) of 3 in. (76 mm) diameter pipe. Intake and Exhaust pipes must 2 inch x 3 inch (51 mm x 76 mm) adaptor is furnished with Ć100 and Ć125 furnaces for exhaust pipe connection. Exhaust pipe must terminate with 1Ć1/2 inch (38 mm) diameter pipe for furnaces using1Ć1/2 (38 mm) or 2 inch (51 mm) diameter pipe runs. Exhaust pipe must terminate with 2 inch (51 mm) diameter pipe for furnaces using 3 inch (76 mm) diameter pipe runs. See pages 10 thru 12 for Termination Kits available.

G26Ć75 Ċ 5 feet (1.5 m) with two 90 elbows of 2 inch (51 mm) diameter pipe. (15 equivalent feet (4.6 m) total). G26Ć100 Ċ 5 feet (1.5 m) with two 90 elbows of 2 inch (51 mm) diameter pipe. (15 equivalent feet (4.6 m) total). G26Ć125 Ċ 5 feet (1.5 m) with two 90 elbows of 2 inch (51 mm) diameter pipe. (15 equivalent feet (4.6 m) total).

be the same diameter.

GAS PIPE CAPACITY - FT3/HR (kL/HR)

Nominal Internal

Iron Pipe Size

-Inches(mm)

1/4

(6.35)

3/8

(9.53)

1/2

(12.7)

3/4

(19.05)

(25.4)

1-1/4

(31.75)

1-1/2

(38.1)

(50.8)

2-1/2

(63.5)

(76.2)

(101.6)

Diameter

-Inches(mm)

.364

(9.246)

.493

(12.522)

.622

(17.799)

.824

(20.930)

1.049

(26.645)

1.380

(35.052)

1.610

(40.894)

2.067

(52.502)

2.469

(67.713)

3.068

(77.927)

4.026

(102.260)

(3.048)20(6.096)30(9.144)40(12.192)50(15.240)60(18.288)70(21.336)80(24.384)90(27.432)

(1.13)

(2.69)

175

(4.96)

360

(10.19)

680

(19.25)

1400

(39.64)

2100

(59.46)

3950

(111.85)

6300

(178.39)

11000

(311.48)

23000

(651.27)

(.82)

(1.84)

120

(3.40)

250

(7.08)

465

(13.17)

950

(26.90)

460

(41.34)

2750

(77.87)

4350

(123.17)

7700

(218.03)

15800

(447.39)

(.68)

(1.47)

(2.75)

200

(5.66)

375

(10.62)

770

(21.80)

1180

(33.41)

2200

(62.30)

3520

(99.67)

6250

(176.98)

12800

(362.44)

NOTE-Capacity given in cubic feet of gas per hour (kilo liters of gas per hour) and based on 0.60 specific gravity gas.

Length of Pipe-Feet(m)

(.57)

(1.27)

(2.32)

170

(4.81)

320

(9.06)

660

(18.69)

990

(28.03)

1900

(53.80)

3000

(84.95)

5300

(150.07)

10900

(308.64)

(.51)

(1.13)

(2.07)

151

(4.28)

285

(8.07)

580

(16.42)

900

(25.48)

1680

(47.57)

2650

(75.04)

4750

(134.50)

9700

(274.67)

(.45)

(1.02)

(1.87)

138

(3.91)

260

(7.36)

530

(15.01)

810

(22.94)

1520

(43.04)

2400

(67.96)

4300

(121.76)

8800

(249.18)

(.42)

(.73)

(1.73)

125

(3.54)

240

(6.80)

490

(13.87)

750

(21.24)

1400

(39.64)

2250

(63.71)

3900

(110.43)

8100

(229.36)

(.40)

(.88)

(1.61)

118

(3.34)

220

(6.23)

460

(13.03)

690

(19.54)

1300

(36.81)

2050

(58.05)

3700

(104.77)

7500

(212.37)

(.37)

(.82)

(1.50)

110

(3.11)

205

(5.80)

430

(12.18)

650

(18.41)

1220

(34.55)

1950

(55.22)

3450

(97.69)

7200

(203.88)

100

(30.480)

(.34)

(.76)

(1.42)

103

(2.92)

195

(5.52)

400

(11.33)

620

(17.56)

1150

(32.56)

1850

(52.38)

3250

(92.03)

6700

(189.72)

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LENNOXOEMPARTS.COM

GLASS FIBER GASKET

FRESH AIR

INTAKE FITTING

BURNER BOX

ASSEMBLY

PATCH

PLATE

G26-3 THROUGH -6 COMPONENTS

FLUE COLLAR

WARM

HEADER

(COLLECTOR)

BOX

PATCH PLATE WITH

BARBED FITTING

AND FLAME

ROLL-OUT SWITCH

DuralokPlus

HEAT EXCHANGER

ASSEMBLY

TOP CAP

CABINET

FLUE

TRANSITION

FLAME SIGHT

BURNER

BOX

COVER

GLASS

GAS VALVE AND

MANIFOLD

BURNER

ACCESS

PANEL

BLOWER ACCESS

DOOR

COMBUSTION AIR

BLOWER

COMBUSTION AIR

PROVE (PRESĆ

SURE) SWITCH

COMBUSTION AIR

ORIFICE

COLD HEADER

(COLLECTOR)

BOX

CONTROL TRANSFORMER

DOOR INTERLOCK

CONTROL BOX COVER

SUPPLY

AIR

BLOWER

PRIMARY LIMIT

(ALTERNATE STYLES)

CONDENSER COIL

CONTROL VOLTĆ

AGE

CIRCUIT BREAKER

SWITCH

FIGURE 1

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LENNOXOEMPARTS.COM

BURNER ACCESS

COVER

BURNER BOX

MANIFOLD

GAS VALVE

FRESH AIR INTAKE

FITTING

G26 HEAT EXCHANGER

CORBEL ORIFICE

CUPS

SURELIGHT IGNITOR LENNOX DURALOKPLUS

HEAT EXCHANGER ASĆ

SEMBLY

COMBUSTION AIR

BLOWER MOTOR

COMBUSTION

AIR BLOWER

BURNER

FLAME SIGHT GLASS

FLUE TRANSITION

DIFFERENTIAL

(COMBUSTION AIR)

PRESSURE SWITCH

BOX

COLD HEADER

(COLLECTOR )

BOX

FIGURE 2

G26 GENERAL PARTS ORIENTATION

WARM HEAD

(COLLECTOR)

BOX

CONDENSER COIL

SUPPLY AIR DUCT

FLANGE

UPPER VEST PANEL

GAS MANIFOLD

PRIMARY LIMIT

GAS VALVE

COMBUSTION AIR BLOWER

DOOR INTERLOCK

SWITCH

BLOWER HOUSING

BLOWER

COMPARTMENT

FIGURE 3

COLD HEADER BOX

HEADER BOX

CONDENSATE

TRAP

LOWER VEST PANEL

CONTROL BOX

CIRCUIT BREAKER

BLOWER MOTOR

BLOWER MOTOR CAPACITOR

Page 8

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LENNOXOEMPARTS.COM

OUTSIDE INSTALLATION

MAKEĆUP BOX

MAKEĆUP BOX INSTALLATION

Box may be installed inside or outside cabinet and may

be installed on left side or right side of cabinet

STAR WASHERS

MUST BREAK

PAINT ON UNIT

CABINET FOR

PROPER

GROUND.

UNIT

CABINET

INSIDE INSTALLATION

MAKEĆUP BOX

Line Voltage Enters Through

Knockout In MakeĆUp Box. J69

Passes Through Side Knockout

Into Side Of Unit.

JACK J69

BLOWER MULLION

PLUG P69

FIGURE 4

I-UNIT COMPONENTS

G26 unit components are shown in figure 1. General parts oriĆ entation is shown in figure 3. The gas valve, ignition control and burners can be accessed by removing the burner access panel. The blower and blower controls can be accessed by removing the blower access door.

G26 units are designed for bottom and side return air. The panels are designed to be knockedĆout (bottom return) or cutĆout (side return) as required for return air duct connecĆ tion.

A-MakeĆUp Box (Figure 5)

The line voltage makeĆup box is shown in figure 5. The box may be installed inside or outside the unit and may be installed on the unit left or right side (figure 4).

MAKEĆUP BOX

BOX

POWER ENTRY KNOCKOUT

120V LINE VOLTAGE

PIGTAIL CONNECTIONS

COVER

Line Voltage Enters MakeĆUp

Box Through Side Of Unit and

J69 Passes Through Bottom

Knockout in MakeĆUp Box.

BLOWER MULLION

An accessory (brown) output wire is provided with the makeĆ up box. The wire provides a 120V connection for optional acĆ cessories such as electronic air cleaner or humidifier. If used, the wire is field installed in J69 jack plug by inserting the pin of the brown wire into the open socket of the jack. See figure

6. 120V accessories rated up to 4 amps total may be conĆ nected to this wire. The neutral leg of the accessory is conĆ

INSTALLING BROWN

ACCESSORY WIRE TO J69

BROWN

WHITE

NEUTRAL

nected to the neutral white wire in the makeĆup box. The accessory terminal is enerĆ gized whenever the blower is in operation.

BLACK

J69

FIGURE 6

B-Control Box Components

G26 CONTROL BOX

TRANSFORMER

UNIT

GROUND

JACK J69

to blower deck

Box may be installed inside or outside unit. See Figure 4

TO BLOWER MULLION

FIGURE 5

Page 9

DOOR

INTERLOCK

SWITCH

SURELIGHT CONTROL

(-3 through -6 models )

FIGURE 7

CIRCUIT

BREAKER

Page 10

LENNOXOEMPARTS.COM

Electrical blower control components (A15), unit transformĆ er (T1) and 24V circuit breaker (CB8) are located in the conĆ trol box. In addition, a door interlock switch (S51) is located in the control box. Jackplugs and a snapĆoff" terminal strip allow the control box to be easily removed for blower serĆ vice.

1- Control Transformer (T1)

A transformer located in the control box provides power to the low voltage 24volt section of the unit. Transformers on all models are rated 40VA with a 120V primary and a 24V secondary.

2- Circuit Breaker (CB8)

A 24V circuit breaker is also located in the control box. The switch provides overcurrent protection to the transformer (T1). The breaker is rated 3A at 32V. If the current exceeds this limit the breaker will trip and all unit operation will shutĆ down. The breaker can be manually reset by pressing the button on the face.

3-Door Interlock Switch (S51)

A door interlock switch rated 14A at 125VAC is located on the control box. The switch is wired in series with line voltĆ age. When the blower door is removed the unit will shut down.

4-Flame Sensor (-3 through -6 models)

A flame sensor is located on the left side of the burner supĆ port. See figure 8. The sensor is mounted on a bracket in the burner support and the tip protrudes into the flame enĆ velope of the left-most burner. The sensor is fastened to burner supports and can be removed for service without removing any part of the burners. During operation, flame is sensed by current passed through the flame and sensĆ ing electrode. The SureLight control allows the gas valve to remain open as long as flame signal is sensed.

NORMAL FLAME SIGNAL u 0.7 MICROAMPS LOW FLAME SIGNAL v 0.7 MICROAMPS MINIMUM FLAME SIGNAL v 0.15 MICROAMPS

SENSOR

3/8"

FIGURE 8

NOTE - The G26 furnace contains electronic compoĆ nents that are polarity sensitive. Make sure that the furnace is wired correctly and is properly grounded.

IGNITOR

5/16"

5-Burners

All units use inshot burners (see figure 9). Burners are factory set and do not require adjustment. A sigh t gl as s is furĆ nished in the burner box assembly for flame viewing. AlĆ ways operate the unit with the burner box cover in place. Burners can be removed as an assembly for service. Burner maintenance and service is detailed in the MAINTENANCE section of this manual. Each burner uses an orifice which is precisely matched to the burner input (see nameplate for orifice size). The orifice is threaded into the burner manĆ ifold. The burner is supported by the orifice and will easily slide off for service. Each orifice and burner are sized speĆ cifically to the unit. Refer to Lennox Repair Parts Listing for correct sizing information. A flame retention ring in the end of each burner maintains correct flame length and shape and keeps the flame from lifting off the burner head. In addition, the burner entrance to each clamshell (Figure 2) is fitted with a corbel cup (orifice) used to direct the flow of combustion products.

TYPICAL BURNER ASSEMBLY

FIGURE 9

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.

6- SureLight Ignition System A3

(-3 through -6 models)

All G26-3 through -6 model units are equipped with the Lennox Sure - Light ignition system. The system consists of ignition control board (figure 10 with control terminal designations in table 1) and ignitor (figures 8 and 11). 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 (4) four amps. See table 2 for troubleshooting diagnostic codes. Table 3 and 4 show jack plug terminal designations. Units equipped with the SureLight board can be used with either electronic or electro-mechanical thermostats without modification. 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 temĆ perature which will successfully light the burner, thus inĆ creasing the life of the ignitor.

NOTE - Do not remove blower access panel to read SureLight LED lights. A sight glass is provided on the access panel for viewing.

Page 10

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SURELIGHT CONTROL BOARD

TABLE 1

SURELIGHT CONTROL TERMINAL DESIGNATIONS

ACB COOL ACB HEAT PARK ACB LOW ACC TX HOT HTG ACC NEUTRALS 24VAC HOT 24VAC RTN FLAME SENSE

Blower - Cooling Speed (Line Volt) Blower - Heating Speed (Line Volt) Alternate Blower Speeds (Dead) Continuous Low Speed Blower Accessory Terminal (Line Volt) 120VAC Hot to Transformer 120VAC Hot Input Heat Only Accessory (Line Volt) 120VAC Neutrals 24VAC Hot from Transformer 24VAC Return from Transformer Flame Sense Terminal

SURELIGHT IGNITOR

MEASUREMENT IS TO I.D.

5/8"

OF RETENTION RING

13/32'

FIGURE 10

FIGURE 11

TABLE 2

DIAGNOSTIC CODES

MAKE SURE TO ID LED'S CORRECTLY: REFER TO INSTALLATION INSTRUCTIONS FOR CONTROL BOARD LAYOUT.

LED #1 LED #2 DESCRIPTION

SIMULTANEOUS

SLOW FLASH

SIMULTANEOUS FAST

FLASH

SIMULTANEOUS

SLOW FLASH

SIMULTANEOUS FAST

FLASH

Also signaled during cooling and continues fan.

Normal operation - signaled when heating demand initiated at thermostat.

Primary or Secondary limit open. Units with board 63K8901 or 24L85: Limit must

SLOW FLASH ON

close within 5 trials for ignition or board goes into one hour limit Watchguard.

Units with board 56L83 or 97L48: Limit must close within 3 minutes or board

Pressure switch open or has opened 5 times during a single call for heat; OR:

OFF SLOW FLASH

Blocked inlet/exhaust vent; OR: Condensate line blocked; OR: Pressure switch

closed prior to activation of combustion air blower.

ALTERNATING SLOW

FLASH

SLOW FLASH OFF

ON SLOW FLASH

ON ON

OFF

FAST FLASH SLOW FLASH

SLOW FLASH FAST FLASH

ALTERNATING FAST

FLASH

NOTE - Slow flash equals 1 Hz (one flash per second). Fast flash equals 3 Hz (three flashes per second). Drop out flame sense current < 0.15 microAmps

ALTERNATING SLOW

FLASH

OFF

ALTERNATING FAST

FLASH

Flame sensed without gas valve energized.

Rollout switch open. OR: 9 pin connector improperly attached.

Circuit board failure or control wired incorrectly.

Main power polarity reversed. Switch line and neutral.

Low flame signal. Measures below .7 microAmps. Replace flame sense rod.

Improper main ground or line voltage below 75 volts; OR: Broken ignitor; OR:

Power - Normal operation

goes into one hour limit Watchguard.

Watchguard - burners fail to ignite.

Open ignitor circuit.

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TABLE 3

SureLight BOARD J156 (J2) TERMINAL

PIN # FUNCTION

1 Ignitor

DESIGNATIONS

Not Used

Ignitor Neutral

Combustion Air Blower Line Voltage

Not Used

Combustion Air Blower Neutral

TABLE 4

SureLight BOARD J58 (J1) TERMINAL

PIN # FUNCTION

1 Primary Limit In

DESIGNATIONS

Gas Valve Common

Roll Out Switch Out

Gas Valve 24V

Pressure Switch In

Pressure Switch and Primary Limit Out

Not Used

Roll Out Switch In

Ground

ELECTROSTATIC DISCHARGE (ESD)

Precautions and Procedures

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 disĆ charge by putting the furnace, the control and the technician at the same electrostatic potenĆ tial. Neutralize electrostatic charge by touching hand and all tools on an unpainted unit surface, such as the gas valve or blower deck, before perĆ forming any service procedure.

a-Electronic Ignition

On a call for heat the SureLight control monitors the comĆ bustion air blower pressure switch. The control will not beĆ gin the heating cycle if the pressure switch is closed (bypassed). Once the pressure switch is determined to be open, the combustion air blower is energized. When the differential in the pressure switch is great enough, the

pressure switch closes and a 15-second pre-purge beĆ gins. If the pressure switch is not proven within 2-1/2 minĆ utes, the control goes into Watchguard-Pressure Switch mode for a 5-minute re-set period. After the 15-second pre-purge period, the SureLight igniĆ tor warms up for 20 seconds after which the gas valve opens for a 4-second trial for ignition. G26 units with board 63K89, 24L85 or 56L83: the ignitor stays energized for the first second of the 4-second trial. Units with board 97L48: ignitor stays energized for the full 4-second ignition trial. If ignition is not proved during the 4-second period, the conĆ 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 SureLight control board has an added feature that prolongs the life of the ignitor. After a successful ignition, the SureLight control utilizes less power to energize the igĆ nitor 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 lowĆ est 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. Fan off time will affect comfort and is adjustable to satisfy individual applications. See figure 12.

FANĆOFF TIME ADJUSTMENT

60sec. 90sec. 120sec. 180sec.

To adjust fan-off timing, flip dip switch to desired setting.

FIGURE 12

7-Blower Motors and Capacitors

All G26 units use direct drive blower motors. All motors used are 120V permanent split capacitor motors to ensure maximum efficiency. See table 5 for ratings.

Page 12

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LENNOXOEMPARTS.COM

TABLE 5

BLOWER MOTOR HP

G26Q2

G26Q3

G26Q3/4 G26Q4/5

G26 BLOWER RATINGS 120V 1PH

1/5

1/3 1/2

3/4 40MFD 370V

CAP

5MFD 370V

7.5MFD 370V

8-Combustion Air Blower (B6)

All G26 units use a combustion air blower to move air through the burners and heat exchanger during heating opĆ eration. The blower uses a PSC or shaded Pole 120VAC motor. PSC motors use run capacitors. The motor operates during all heating operation and is controlled by blower conĆ trol A15. The blower operates continuously while there is a call for heat. The ignition control is prevented from proceedĆ ing through the ignition sequence until combustion air blower operation is sensed by the prove switch. The pressure switch connected to the combustion air blower

housing is used to prove combustion air blower operation. The switch monitors air pressure in the blower housing. DurĆ ing normal operation, the pressure in the housing is negaĆ tive. 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.

9-Primary Limit Control (S10)

The primary limit (S10) on G26 units is located in the middle of the heating 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 de-energizes the gas valve. The limit automatiĆ cally resets when unit temperature returns to normal. The switch is factory set and cannot be adjusted. The switch may have a different setpoint for each unit model numĆ ber. However, the setpoint will be printed on the side of the limit.

SPADE CONNECTORS

G26 SERIES UNITS AND ALTERNATE STYLE

LIMIT CONTROL (S10) FOR

Units may be equipped with either style limit.

LIMIT

INSULATING COVER (s)

FIGURE 13

10-Rollout Switch (S47) -3 Through -6

Flame rollout switch S47 is a SPST N.C. high temperature limit located on the right side of the burner box assembly (see figure 14). S47 is wired to the burner ignition control A3. When S47 senses flame rollout (indicating a blockage in the combustion passages), the flame rollout switch trips, and the ignition control immediately closes the gas valve. Switch S47 in all G26 units is factory preset to open at 200F + 12F (93C + 6.7C) on a temperature rise. All flame rollout switches are manually reset. A kit (#65K60) is available for G26 -1 and -2 models.

FLAME ROLLOUT SWITCH (S47)

FLAME ROLLOUT

SWITCH (S47)

FIGURE 14

11- BCC2-3 Blower Control A15 (-1 and -2 models)

All G26-2 and -1 model units utilize the BCC2Ć3 blower conĆ trol manufactured by Heatcraft. The BCC2Ć3 is a printed cirĆ cuit board which controls the supply air blower and monitors primary limit and gas valve operation. The control has a nonĆadjustable, factory preset fanĆon" timing. Fan off" timĆ ing is adjustable. The board is divided into two sections, 120 and 24VAC. Line voltage comes into the board on the 120VAC side. See figure 16.

Fan Timings

Fan off" timing (time that the blower operates after the heat demand has been satisfied) is determined by the arrangeĆ ment of a jumper across pins on the BCC2Ć3 blower control board. See figure 15. To adjust fan off " timing, gently disĆ connect jumper and reposition across pins corresponding with new timing. Fan on" time is factory set at 45 seconds and is not adjustable.

NOTEĊIf fan off" time is set too low, residual heat in heat exchanger may cause primary limit S10 to trip reĆ sulting in frequent cycling of blower. If this occurs, adĆ just blower to longer time setting.

Figure 15 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 a heating demand but not after a blower or cooling demand (that is, when indoor therĆ mostat switch is changed from ON to AUTO and heating/ cooling demand is not present, the blower stops immediateĆ ly).

FANĆOFF TIME ADJUSTMENT

To adjust fanĆoff timing:

TIMING

JUMPER

270

150

Remove jumper from BCC2Ć3 and seĆ lect one of the other pin combinations

to achieve the desired time.

210

TIMING

PINS

(seconds)

Leave jumper off for

330 second fanĆoff timing.

FIGURE 15

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LENNOXOEMPARTS.COM

G26 BLOWER CONTROL Ć BCC2Ć3 (A15)

DETACHABLE

STRIP ON EARLY

BOARDS ONLY

Table 8 shows

terminal designations.

FIGURE 16

12-Ignition Control (-1 and -2 models)

G26 -1 and -2 model units use an intermittent pilot ignition manufactured by Johnson Controls. The ignition control is located 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 conĆ 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 continĆ ues to run until demand stops, flame sensor senses loss of flame, a limit opens or the prove switch opens. If any of these events occur during a thermostat demand, the gas valve closes.

The control will attempt ignition for 85 seconds. If ignition is not successful, the control will lockout (indicated by flashĆ ing LED). Within one hour the control will momentarily reĆ move then reapply the thermostat signal and the ignition sequence will begin again (Watchguard circuit). If pilot ignition is successful, but flame is lost when the main valve opens, the ignition sequence will retry up to 15 more times. If ignition is not successful after the 16th try, the control will shutĆdown and must be reset manually. Manual reset is accomplished by removing thermostat demand for at least 2 seconds then reapplying demand.

Table 8 shows

terminal designations.

IGNITION CONTROL A3

SPARK

OUTPUT

SEE TABLE 6

FOR TERMINAL

DESIGNATIONS

FIGURE 17

DANGER

Shock hazard. Spark related components contain high voltage. Disconnect power before servicing. Control is not field repairable. If control is inoperĆ able, simply replace entire control.

Can cause injury or death. Unsafe operation will result if repair is attempted.

TABLE 6

IGNITION CONTROL A3 TERMINAL DESIGNATIONS

Terminal Type Function

GROUND 1/4" Spade Cabinet Ground

THS 2 1/4" Spade

P. V. 1 1/4" Spade

M.V.3 1/4" Spade

SENSE 4 1/4" Spade Microamp Flame Sensing Input

Unmarked

Pin Type

Bare Wire

Safety Limit 24VAC Input

From Differential Switch

24VAC Output to Pilot Operator

24VAC Output to Main Operator

of Gas Valve

High Voltage Spark Output

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LENNOXOEMPARTS.COM

Diagnostic LED

The furnace control is equipped with a diagnostic LED used for troubleshooting the unit and the control. LED functions are shown in table 7.

TABLE 7

Furnace Control A3 Diagnostic LED

LED State Meaning Remedy

Steady On Normal Operation Ć Ć Ć Ć Slow Flash

(1 sec. on/ 5 sec. off)

Off

BLOWER CONTROL A15 TERMINAL DESIGNATIONS

Ter mi na l

(Designation

on Wiring

Diagram)

IBN (N) 1/4" Spade 120VAC Indoor Blower Common

N1 (N) 1/4" Spade

CABN (N) 1/4" Spade

XFMRN(N) 1/4" Spade 120VAC Transformer Common

HSIN (N) 1/4" Spade

CAB 1/4" Spade

L1 1/4" Spade 120VAC Line Voltage In

A 1/4" Spade

XFMR 1/4" Spade 24VAC In From Transformer

D 1/4" Spade

CF 1/4" Spade

H 1/4" Spade

ACC 1/4" Spade

24V (24)

LIMIT

(L)

W 1/4" Spade

VALV E

SENSE (V)

T 1/4" Spade

COM (C) 1/4" Spade 24VAC Common To Transformer

Control Retry

Period

Control Failure or

Power Failure or

Hard Lockout

Type Function

Detachable Screw Strip

1/4" Spade 24VAC Input From Transformer

1/4" Spade

3/16" Spade 24VAC Input From Gas Valve

Failed to Sense Flame. Ignition ConĆ

If Power and Gas Supply are OK, Try

Removing T'stat Demand For At Least

30 Seconds. If LED Remains Off

When Demand Is Returned, Replace

trol Will Retry

Before Locking Out.

Control.

TABLE 8

Cooling Demand

Blower Demand

24VAC to Thermostat

Heating Demand

24VAC Common

To Indoor Thermostat

120VAC Neutral

(L2 Line Voltage Neutral)

120VAC Combustion Air Blower ComĆ

120VAC Hot Surface Ignition

Combustion Air Blower

to Blower Cooling Tap

Dummy Connection for

Unused Blower Leads

Continuous Blower Tap

Switched 120VAC to Accessory (ElecĆ

tronic Air Cleaner, Humidifier, Etc.)

24VAC In From Primary Limit. Limit

Open: Closes Gas Valve and Turns On

Blower Limit Closed: Allows Ignition

24VAC Thermostat Demand Output

Through Differential Switch to THS"

Terminal of Ignition Control

24VAC Common From

Ignition Control and Gas Valve

mon

Common (Not Used) Switched 120VAC to

Switched 120VAC

Switched 120VAC to

Blower Heating Tap

Johnson G776 Ignition Control Operation

Th e infor ma tion in t his sec ti on is pro tected by a co py right iss ued by Johnson Controls, Inc., and is reproduced with permission.

On a call for heat from indoor thermostat, the ignition control energizes and ignition control LED lights (steady on). The combustion air blower is energized. After 15 second preĆ purge period, the control simultaneously opens pilot valve and sends spark to pilot electrode.

If pilot ignites within 85 seconds, flame sensor detects pilot flame and signals ignition control to energize the main valve. The main valve cannot be energized until sensor detects pilot flame. Spark continues until pilot flame is sensed or 85 seconds has elapsed.

When pilot flame is sensed, main valve is energized and spark turns off. The ignition control remains in run" mode until indoor thermostat is satisfied or flame lost.

If pilot flame is not sensed before the end of the 85 second trial for ignition, the control enters the 100% shutoff mode. The spark circuit and pilot valve deĆenergize and the ignition conĆ trol 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 seconds. After the delay period, another trial for ignition sequence starts, beginĆ ning with preĆpurge.

If pilot flame goes out while the indoor thermostat is calling for heat, both main and pilot valves deĆenergize within 0.8 seconds and remain deĆenergized for five seconds. After this delay, the spark and pilot valve energize until flame is sensed or the 85 second trial for ignition period ends. If this flameout" cycle repeats 16 times (pilot flame is estabĆ 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 2 seconds and then closed.

If flame is detected when the thermostat calls for heat, it must extinguish within 30 seconds for normal operation. If flame is still present after 30 seconds, the control goes into lockout and the LED goes off.

13-Pilot, Spark Electrode, Flame Sensor

(-1 and -2 models)

Figure 18 shows the arrangement of pilot, flame sensor, spark electrode and burners. The ignition control uses diĆ rect spark to ignite the pilot. The pilot ignites the burners and the burners crossĆlight. The flame sensor uses flame rectification to sense pilot ignition. The ignition control reĆ quires that pilot flame must be sensed before the main gas valve is allowed to open. Typically, a 2 to 4 second delay occurs between the pilot ignition and the main valve openĆ ing. Figure 19 shows the gap between the tip of the elecĆ trodes and the burner surface. It is important that the gap be maintained for consistent ignition of pilot flame.

Page 15

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LENNOXOEMPARTS.COM

TYPICAL BURNER PILOT/ELECTRODE ORIENTATION

FRESH AIR INTAKE

MANIFOLD

BURNER BOX

view looking at side of burners

GAP

BURNERS

FLAME SENSOR

SPA RK

ELECĆ

TRODE

PILOT

HOOD

FIGURE 18

Both pilot and main burner flame should be predominantly blue and strong in appearance. Pilot flame must surround the end of flame sensor for proper operation of pilot safety circuit.

PILOT HOOD

PILOT

1/8 (.125) Inch "1/32 (.031)

GAP

SPARK ELECTRODE

place when reading manifold pressure. An LPG changeover kit is available. The kit includes main and

pilot burner orifices (pilot orifice for -1 and -2 units only) and a regulator conversion kit. All L.P. orifices can be identified by a band around the orifice. Natural gas orifices do not have the band.

HONEYWELL VR8204 GAS VALVE

REGULATOR ADJUSTMENT SCREW LOCATION

PRESSURE

REGULATOR

ADJUSTING

SCREW

(White)

REGULATOR

COVER SCREW

(Black)

SPRING Tapered End

Down (Red)

INLET

PRESSURE

TAP

GAS INLET

WHITE RODGERS 36E GAS VALVE

REGULATOR ADJUSTMENT SCREW

LOCATION

REGULATOR

COVER SCREW

ADJUSTING SCREW

(White)

PILOT, SPARK ELECĆ

TRODE

FLAME SENSOR

SENSOR WIRE

AND FLAME SENSOR

SPARK WIRE

FIGURE 19

14-Gas Valve

The G26 uses a gas valve manufactured by Honeywell or White Rodgers. See figure 20. The valve is internally reĆ dundant to assure safety shutĆoff. 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 MV" termiĆ nals on the Honeywell or M/C or 1/2 terminals on the White Rodgers opens the main valve. Inlet and outlet pressure taps are located on the valve. A regulator adjustment screw (figure 20 ) is located on the valve. Regulator cover screw must be in

SPRING

FIGURE 20

100% Sealed Combustion

The burner box is completely sealed and operates under a negative pressure. A pressure hose is connected from the burner box to the gas valve regulator and differential presĆ sure switch. The gas valve senses the pressure in the burner box and changes gas valve output based on changes in burner box pressure. The intent is to compenĆ sate for different vent configurations which can greatly afĆ fect the rate of the unit.

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LENNOXOEMPARTS.COM

NORMAL OPERATION (Natural Gas Units)

3.5

3.4

OPERATION AT THIS EXTREME

MAY INDICATE A BLOCKED

OUTLET OR OTHER PROBLEM

3.3

3.2

3.1

3.0

2.9

2.8

GAS VALVE OUTPUT

2.7

2.6

MANIFOLD PRESSURE (positive inches water column)

2.5

Gray area indicates normal operating range + 10% of manifold pressure The purpose of this chart is to explain unit operation . Each unit may vary depending on installation, altitude, intake/exhaust configuration and other factors.

OPERATION AT THIS EXTREME

MAY INDICATE A BLOCKED

INLET OR OTHER PROBLEM

BURNER BOX PRESSURE

(Negative inches water gauge

measured on right side of burner box)

FIGURE 21

15-Differential Pressure Switch (S64)

(Combustion Air Prove Switch)

G26 series units are equipped with a differential pressure switch located on the vestibule panel. The switch is conĆ nected to the combustion air blower housing by means of a flexible silicon hose. A separate hose connects the presĆ sure switch to the burner box and the gas valve regulator. The switch monitors air pressure in the combustion air blower housing and burner box.

The switch is a singleĆpole singleĆthrow normally open pressure switch electrically connected in series with the ignition control. The purpose of the switch is to prevent burner operation if the combustion air blower is not operatĆ ing or if sufficient combustion air is not available,

On startĆup, the switch senses that the combustion air blowĆ er is operating. It closes a circuit to the ignition control when the difference in pressure across the pressure switch inĆ creases above 0.2 in. w.c. The pressure sensed by the

-1.0-0.20 -0.4 -0.6 -0.8

switch is relative to the pressure in the burner box. In order

for the furnace to operate, the larger negative must alĆ ways be on the combustion air blower side of the switch. If the flue or air inlet become obstructed during opĆ

eration, the switch senses a loss of pressure differential (drops below 0.20 in. negative w.c.) and opens the circuit to the ignition control.

NORMAL OPERATION (L.P. Gas Units)

7.0

6.9

OPERATION AT THIS EXTREME

MAY INDICATE A BLOCKED

OUTLET OR OTHER PROBLEM

6.8

6.7

6.6

6.5

6.4

6.3

GAS VALVE OUTPUT

6.2

6.1

MANIFOLD PRESSURE (positive inches water column)

6.0

OPERATION AT THIS EXTREME

MAY INDICATE A BLOCKED

INLET OR OTHER PROBLEM

-1.0-0.20 -0.4 -0.6 -0.8

BURNER BOX PRESSURE

(Negative inches water column

measured on right side of burner box)

FIGURE 22

Figures 21 and 22 show how gas valve output changes as burner box pressure changes. Generally, a lower burner box pressure produces a leaner gas/air mixture and a higher burner box pressure produces a richer mixture. A procedure showing how to check manifold pressure is shown on page 29.

DIFFERENTIAL PRESSURE SWITCH CIRCUITRY

BURNĆ

TEE

DIFFERENTIAL

PRESSURE

SWITCH

COMBUSTION

AIR PRESĆ

SURE SENSĆ

ING HOSE

COMBUSTION

AIR BLOWER

LEFT SIDE OF PRESSURE SWITCH = MORE NEGATIVE

RIGHT SIDE OF PRESSURE SWITCH = LESS NEGATIVE (Closer to Zero)

BOX

HOSE BARB

BURNER

BOX

SENSING

HOSE

GAS

VALV E

SENSING

HOSE

GAS

VALV E

PRESSURE

SWITCH

SENSING

HOSE

FIGURE 23

The switch is factory set and is not adjustable. It is a safety shutĆdown control and MUST not be bypassed.

Figure 24 shows the pressure differential required to obĆ tain unit operation. If the switch does not successfully sense the required differential, the switch cannot close and the furnace cannot operate.

When measuring the pressure differential, readings should be taken at the pressure switch.

Page 17

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LENNOXOEMPARTS.COM

-1.2

CHART REPESENTS NORMAL OPERATING

CHARACTERISTICS OF THE PRESSURE SWITCH ONLY

AND SHOULD NOT BE USED FOR TROUBLSHOOTING

-1.0

-0.8

-0.6

-0.4

-0.2

COMBUSTION AIR BLOWER STATIC PRESSURE

DIFFERENTIAL SWITCH CLOSED

-0.4 -0.6 -0.8 -1.2

BURNER BOX STATIC PRESSURE

FIGURE 24

Temporarily jumpering the pressure switch when troubleĆ shooting will determine if the pressure switch and furnace are operating properly. However, this may not indicate if the sealed combustion system is operating properly. If the unit cannot attain 0.2 inches differential, the unit will not operate. Be sure to remove jumper when finished. See Warning this page.

WARNING

Safety Hazard. Turn off gas supply before jumpĆ ering switch or testing switch differential. If switch is operating properly and sealed comĆ bustion system is operating improperly, a poĆ tentially lethal situation will be created when switch is bypassed. DO NOT ALLOW UNIT TO OPERATE WITH SAFETY SYSTEMS BYPASSED.

Checks of pressure differential can be made as an aid in trouĆ bleshooting. It is important to remember that the switch must see" 0.2 inches differential in order for the furnace to operate. Lack of differential usually indicates problems in the intake or exhaust piping but may indicate problems in the heat exĆ changer, condenser coil, header boxes, combustion blower or other components. Generally, if both readings are closer to zero (figure 24) the unit may have a restricted flue outlet or other problem. If both readings are farther from zero (figure

24) the unit may have a restricted flue inlet or other problem.

DIFFERENTIAL SWITCH OPEN

(Furnace will not operate)

-1.0-0.20

Measuring pressure differential

The differential pressure is the difference in pressure meaĆ sured on either side of the pressure switch:

1 - Remove thermostat demand and allow to cycle off. 2 - Disconnect hose from left side of pressure switch and

install Tee as shown in figure 25.

TEE AND 1/4"i.d. RUBBER HOSE FIELD

PROVIDED

USED FOR MEASURING PRESĆ SURE ACROSS BURNER BOX

AND COMBUSTION AIR BLOWER

TO PRESSURE

SWITCH

TO PRESSURE

SENSING HOSE

TO DRAFT GAUGE

FIGURE 25

3 - Install draft gauge to open end of Tee. 4 - Operate unit and observe draft gauge reading. ReadĆ

ings will change as heat exchanger warms.

a. Take one reading immediately after startup. b. Take a second reading after unit has reached

steady state (approximately 5 minutes). 5 - Remove thermostat demand and allow to cycle off. 6 - Remove draft gauge and Tee. Reinstall combustion air

sensing hose to left side of pressure switch. 7 - Disconnect hose from right side of pressure switch

and install Tee as shown in figure 25. 8 - Install draft gauge to open end of Tee.

Page 18

Page 19

LENNOXOEMPARTS.COM

9 - Operate unit and observe draft gauge reading. ReadĆ

ings will change as heat exchanger warms.

a. Take one reading immediately after startup. b. Take a second reading after unit has reached steady state (approximately 5 minutes). Both readings should fall above the line shown in figure 24.

10- Compare readings to figure 24. Be sure to compare

only like readings (compare startup reading to startup reading, then compare steady state reading to steady state reading). Subtract the absolute steady state readings from one another. This will be the pressure differential. In order for the furnace to operate, the

larger negative must always be on the combustion air blower side of the switch

Example - one side of the pressure switch reads .60" and the other side of the pressure switch reads .10". Pressure differential is .60" - .10"= .50"

The pressure differential should be greater than 0.20" W.C. (49.72Pa).

11- When test is complete, remove thermostat demand

and allow unit to cycle off. 12- Remove draft gauge and Tee. Reinstall pressure

switch sensing hose to left side of pressure switch. If pressure switch does not close at start up or differential is less than .20" the following should be checked. 1 - Restriction in exhaust and or intake vent. 2 - Pressure switch lines are routed correctly and for

damage. 3 - Condensate in pressure switch lines. 4 - Wiring of pressure switch to furnace. 5 - Blocked heat exchanger or leak in heat exchanger.

II-PLACEMENT AND INSTALLATION

Make sure unit is installed in accordance with installation instructions and applicable codes.

A-PVC Joint Cementing Procedure

6 - Promptly apply solvent cement to end of pipe and inĆ

side socket surface of fitting. Cement should be apĆ plied lightly but uniformly to inside of socket. Take care to keep excess cement out of socket. Apply secĆ ond coat to end of pipe.

NOTE-Time is critical at this stage. Do not allow primer to dry before applying cement.

7 - Immediately after applying last coat of cement to pipe,

and while both inside socket surface and end of pipe are wet with cement, forcefully insert end of pipe into socket until it bottoms out. Turn pipe 1/4 turn during assembly (but not after pipe is fully inserted) to distribĆ ute cement evenly. Once joint is made, PVC may swell. Hold joint together until bonded (approximately 20 seconds).

NOTE-Assembly should be completed within 20 secĆ onds after last application of cement. Hammer blows should not be used when inserting pipe.

8 - After assembly, wipe excess cement from pipe at end

of fitting socket. A properly made joint will show a bead around its entire perimeter. Any gaps may indiĆ cate a defective assembly due to insufficient solvent.

9 - Handle joints carefully and support properly until comĆ

pletely set.

B-Venting Considerations

The thickness of construction through which vent/air intake pipes may be installed is 24" (610mm) maximum and 3" (76mm) minimum. If a G26 furnace replaces a furnace which was commonly vented with another gas appliance, the size of the existing vent pipe for that gas appliance must be checked. Without the heat of the original furnace flue prodĆ ucts, the existing vent pipe may be oversized for the single water heater or other appliance. The vent should be checked for proper draw with the remaining appliance.

CAUTION

WARNING

DANGER OF EXPLOSION! Fumes from PVC glue may ignite during system check. Remove spark plug wire from ignition control before 120V power is applied. Reconnect wire after two minutes.

1 - Measure and cut vent pipe to desired length. 2 - Debur and chamfer end of pipe, removing any ridges

or rough edges. If end is not chamfered, edge of pipe

may remove cement from fitting socket and result in a

leaking joint. 3 - Clean and dry surfaces to be joined. 4 - Test fit joint and mark depth of fitting on outside of

pipe. 5 - Uniformly apply liberal coat of PVC primer for PVC or

ABS cleaner for ABS for at least 5 to 15 seconds to inĆ

side socket surface of fitting and male end of pipe to

depth of fitting socket. Remove puddles of primer before

applying cement.

Page 19

Insufficient combustion air can cause headaches, nausea, dizziness or asphyxiation. Excessive exĆ posure to contaminated combustion air will result in safety and performance related problems. Avoid exposure to 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.

Page 20

LENNOXOEMPARTS.COM

Intake Piping

1 - Cement intake piping in slip connector located at top

of unit.

2 - Route piping to outside of structure. Continue with

installation following instructions given in exhaust and intake piping termination section.

Exhaust Piping

1 - Cement exhaust piping into flue collar socket located

on the left side of the top cap.

2 - All horizontal runs of exhaust pipe must slope back toĆ

ward unit. A minimum of 1/4" (6mm) drop for each 12" (305mm) of horizontal run is mandatory for drainage. Horizontal runs of exhaust piping must be supported every 5 ft. (1.52m) using hangers for schedule 40 pipe. All other pipe must be supported every 3 ft. (.91m).

NOTE - Exhaust piping should be checked carefully to

make sure there are no sags or low spots.

NOTE - Exhaust piping must be insulated with 1/2"

(13mm) Armaflex or equivalent when run through unĆ

heated space. Do not leave any area of exhaust pipe

open to outside air; exterior exhaust must be insulated

with 1/2" (13mm) Armaflex or equivalent.

CAUTION

Do not discharge exhaust into an existing stack or stack that also serves another gas appliance. If vertical discharge through an existing unused stack is required, insert PVC pipe inside the stack until the end is beyond the top or outlet end of the metal stack.

CAUTION

The exhaust vent pipe operates under positive pressure and must be completely sealed to preĆ vent leakage of combustion products into the livĆ ing space.

Removal of Unit from Common Venting System

In the event that an existing furnace is removed from a venting system commonly run with separate gas apĆ pliances, the venting system may be too large to properly vent the remaining attached appliances. The following test should be conducted while all appliances (both in operaĆ tion and those not in operation) are connected to the comĆ mon venting system. If the venting system has been installed improperly, corrections must be made as outlined in the previous section.

1 - Seal any unused openings in the common venting sysĆ

tem.

2 - Visually inspect the venting system from proper size

and horizontal pitch and determine there is no blockĆ age or restriction, leakage, corrosion and other defiĆ ciencies which could cause an unsafe condition.

3 - Insofar as is practical, close all building doors and winĆ

dows and all doors between the space in which the apĆ pliances remaining connected to the common venting system are located and other spaces of the building. Turn on clothes dryers and any appliances not conĆ nected to the common venting system. Turn on any exĆ haust fans, such as range hoods and bathroom exĆ hausts, so they will operate at maximum speed. Do not operate a summer exhaust fan. Close fireplace dampĆ ers.

4 - Follow the lighting instruction. Place the appliance

being inspected in operation. Adjust thermostat so appliance will operate continuously.

5 - Test for spillage at the draft hood relief opening after 5

minutes of main burner operation. Use the flame of match or candle, or smoke from a cigarette, cigar.

6 - After it has been determined that each appliance reĆ

maining connected to the common venting system properly vents when tested as outlined above, return doors, windows, exhaust fans, fireplace dampers and any other gasĆburning appliance to their previous condition of use.

7 - If improper venting is observed during any of the

above tests, the common venting system must be corrected. The common venting system should be resized to approach the minimum size as determined by using the appropriate tables in appendix G in the curĆ rent standards of the National Fuel Gas Code ANSI Z223-1 in the U.S.A., and the appropriate Category 1 Natural Gas and Propane appliances venting sizing tables in the current standards of the CAN/ CGA-B149.1 and .2 in the Natural Gas and Propane Installation Code in Canada.

Intake and Exhaust Piping Terminations

Intake and exhaust pipes may be routed either horizontally through an outside wall or vertically through the roof. In atĆ tic or closet installations, vertical termination through the roof is preferred. Figures 26 through 38 show typical terĆ minations.

1 - Use recommended piping materials for both intake

and exhaust piping.

2 - Secure all joints, including drain leg, gas tight using

approved primer and cement.

Page 20

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LENNOXOEMPARTS.COM

3 - Piping diameters should be determined according to

length of pipe run. See vent pipe specifications on page 6. Locate intake piping upwind (prevailing wind) from exhaust piping. To avoid re-circulation of exĆ haust gas on roof terminations, end of exhaust pipe must be higher than intake pipe.

Exhaust and intake exits must be in same pressure zone. Do not exit one through the roof and one on the side. Also, do not exit the intake on one side and the exhaust on another side of the house or structure.

4 - Intake and exhaust pipes should be placed as close

together as possible at termination end (refer to ilĆ lustrations). Maximum separation is 3" (76mm) on roof terminations and 6" (152mm) on side wall terĆ minations.

5 - Exhaust piping must terminate straight out or up as

shown. In rooftop applications, a 2" X 1-1/2" reducer for 2" venting, 3" x 2" reducer for 3" venting must be used on the exhaust piping after it exits the structure to imĆ prove the velocity of exhaust away from the intake pipĆ ing.

On roof terminations, the intake piping should termiĆ

nate straight down using two 90 elbows (See figure

26).

Inches(mm)

3(76) MAX.

3 x 2 (76 x 51) OR 2 x 1-1/2 (51 x 38)

PVC REDUCER

NOTE - If winter design temperature is below 32 F (0C), exĆ haust piping must be insulated with 1/2" (13mm), Armaflex or equivalent when run through unheated space. Do not leave any surface area of exhaust pipe open to outside air; exterior exhaust pipe must be insulated with 1/2" (13mm) Armaflex or equivalent. In extreme cold climate areas, 3/4" (19mm) ArĆ maflex or equivalent is recommended. Insulation on outside runs of exhaust pipe must be painted or wrapped to protect insulation from deterioration.

NOTE - During extremely cold temperatures, below approximately 20F (6.67C), units with long runs of vent pipe through unconditioned space, even when insulated, may form ice in the exhaust termination that prevents the unit from operating properly. Longer run times of at least 5 minutes will alleviate most icing problems. Also, a heating cable may be installed on exhaust piping and termination to prevent freeze-ups. Heating cable installation kit is available from Lennox. See Condensate Piping section for part numbers.

NOTE - Care must be taken to avoid re-circulation of exĆ haust back into intake pipe.

6 - On field supplied terminations for side wall exits, exĆ

haust piping should extend a minimum of 12" (305mm) beyond the outside wall. Intake piping should be as short as possible. See figure 27.

1/2 (13) ARMAFLEX

INSULATION IN

UNCONDITIONED SPACE

12 (305) MIN.

2 X 1-1/2

(51 x 38)

PVC REDUCER

8 (203) MIN

12 (305) ABOVE

AVERAGE SNOW

ACCUMULATION

3 (76) OR

2 (51) PVC

PROVIDE SUPPORT

FOR INTAKE AND

EXHAUST LINES

(15F75) LB-49107CC for 2 (51) Venting

(44J41) LB-65678A for 3 (76) Venting

ROOF TERMINATION KIT

1/2 (13) FOAM

INSULATION IN

UNCONDITIONED

SPACE

UNCONDITIONED

ATTIC SPACE

FIGURE 26

IMPORTANT

Do not use screens or perforated metal in intake and exhaust terminations. Doing so will cause freeze-ups and may block the terminations.

2 (51) PVC 1-1/2 (38) PVC

1/2 (13) ARMAFLEX

Inches (mm)

(15J74) LB-49107CB for 2 (50.8) Venting

INSULATION

OUTSIDE

WALL

TOP VIEW

WALL RING KIT

6 (152)

MAXIMUM

8 (203)

MINIMUM

2 (51) PVC

COUPLING

FIGURE 27

7 - On field supplied terminations, a minimum separation

distance between the end of the exhaust pipe and the end of the intake pipe is 8" (203mm).

Page 21

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LENNOXOEMPARTS.COM

8 - If intake and exhaust piping must be run up a side wall

to position above snow accumulation or other obĆ structions, piping must be supported every 3 ft. (.91m) as shown in figure 33. Refer to figures 31 and 32 for proper piping method. WTK wall termination kit must be extended for use in this application. See figure 36 or use kit WTKX shown in figure 37. When exhaust and intake piping must be run up an outside wall, the exhaust piping is reduced to 1-1/2" (38mm) after the final elbow. The intake piping may be equipped with a 90 elbow turndown. Using turndown will add 5ft. (1.5m) to the equivalent length of the pipe.

1/2 (12.7) FOAM INSULATION

IN UNCONDITIONED SPACE

Inches(mm)

EXHAUST

TERMINATION

EXHAUST

INTAKE

TERMINATION

INTAKE

Inches (mm)

CONCENTRIC WALL TERMINATION

(60G77) LB-49107CE for G26-50 & -75 Units Only

(33K97) LB-87942 for G26-100 & -125 Units Only

12 (305) Min.

above grade.

FIGURE 30

OUTSIDE WALL

Optional Turndown

Shown

TOP VIEW

WALL TERMINATION

(22G44) LB-49107CD for 2 (50.8) Venting

(44J40) LB-65701A for 3 (76.2) Venting

(Intake Only)

FIGURE 28

EXHAUST

TERMINATION

INTAKE

TERMINATION

EXHAUST

CONCENTRIC ROOFTOP TERMINATION

(60G77) LB-49107CE for G26-50 & -75 Units Only

(33K97) LB-87942 for G26-100 & -125 Units Only

12 (305) ABOVE

AVERAGE SNOW

ACCUMULATION

INTAKE

Inches (mm)

FIGURE 29

IMPORTANT

For Canadian Installations Only: In accordance to CAN/CGA-B149.1 and .2, the minimum allowed distance between the combusĆ tion air intake inlet and the exhaust outlet of other appliances shall not be less than 12" (305mm).

Inches(mm)

UNCONDITIONED

SPACE

OUTSIDE WALL

PROVIDE SUPPORT

FOR INTAKE AND

EXHAUST LINES EVERY

36 (914)

1/2 (13) FOAM

INSULATION IN

UNCONDITIONED

SPACE

WALL RING TERMINATION

*This reducer is not necessary for G26-50 units using 1-1/2" venting.

See venting table on page 6 for maximum venting lengths with this

(15F74) LB-49107CB for 2" (51) Venting

SIDE VIEW

arrangement.

12 (305) MIN. for 2 (51)

20 (508) MAX. for 3 (76)

8 (203)

MIN.

12 (305) ABOVE

AVERAGE SNOW

ACCUMULATION

1/2 (13) FOAM

INSULATION

FIGURE 31

9 - Position termination ends so they are free from any obĆ

structions and above the level of snow accumulation (where applicable). Termination ends must be a miniĆ mum of 12" (305mm) above grade level. Do not point into window wells, stairwells, alcoves, courtyard areas or other recessed areas. Do not position termination ends closer than 12" below roof eaves or above a walkĆ way. Since the G26 is a certified direct vent, Category IV gas furnace, the location of the termination is limited by building codes. In the absence of local codes, refer to the current National Fuel Gas Code ANSI Z223-1 in U.S.A., and current standards CAN/CGA-B149.1 /.2 of the Natural Gas and Propane Installation Instructions in Canada for details. The termination should be at least 12" (305mm) from any opening through which flue products could enter the building.

Page 22

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LENNOXOEMPARTS.COM

When horizontally vented, minimum clearance for termination from electric meters, gas meters, regulaĆ tors and relief equipment is 4 ft. (1.2m) for US installaĆ tions. Refer to the current CAN/CGA-B149.1 and .2 for installations in Canada or with authorities having local jurisdiction.

At vent termination, care must be taken to maintain protective coatings over building materials (proĆ longed exposure to exhaust condensate can destroy protective coatings). It is recommended that the exĆ haust outlet not be located within 6 feet (1.8m) of a condensing unit because the condensate can damĆ age the painted coating.

IMPORTANT

Combustion air intake inlet and exhaust outlet should not be located within 6 ft. (1.8m) of dryer vent or combustion air inlet or outlet of another apĆ pliance. Piping should not exit less than 3 ft. (.91m) from opening into another building.

10- Suspend piping using hangers at a minimum of every

5 feet (1.52m) for schedule 40 PVC and every 3 feet (.91m) for ABS-DWV, PVC-DWV, SPR-21 PVC, and SDR-26 PVC piping. A suitable hanger can be fabriĆ cated by using metal or plastic strapping or a large wire tie.

11- In areas where piping penetrates joists or interior

walls, hole must be large enough to allow clearance on all sides of pipe through center of hole using a hanger.

12- Isolate piping at the point where it exits the outside

wall or roof.

13- When furnace is installed in a residence where unit is

shut down for an extended period of time, such as a vacation home, make provisions for draining condenĆ sate collection trap and lines.

14- Based on the recommendation of the manufacturer, a

multiple furnace installation may use a group of up to four termination kits WTK assembled together horizonĆ tally, as shown in figure 35.

Inches(mm)

INSULATION

3 (76) OR

2 (51) 90 ELBOW

Optional TurnĆ

down

(Not Shown)

May Be Used on

Intake Only

(22G44) LB-49107CD for 2(51) Venting

(44J40) LB-65701A for 3(76) Venting

METAL OR PLASTIC

STRAPĆ

PING

OR LARGE

WIRE TIES

1/2 (13)

FOAM

FRONT VIEW

WALL TERMINATION

REDUCER BUSHING LOCAĆ

FOR OFFSET TERMINATION

FIGURE 32

3 x 2 (76 x 51) OR 2 x 1-1/2 (51 x 38)

TION

3 (76) OR

2 (51) 90 ELBOW

Inches (mm)

Front View

INTAKE

VENT

1/2 (13) Foam

Insulation in

Unconditioned Space

Inches (mm)

WALL TERMINATION KIT (30G28) WTK

(305)

(127)

Side View

EXHAUST VENT

VENT TERMINATIONS

FIGURE 34

EXHAUST VENT

INTAKE VENT

OUTSIDE WALL

FIGURE 33

Page 23

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LENNOXOEMPARTS.COM

Front View

INTAKE VENT

EXHAUST

VENT

18 MAX.

(457)

(127)

5-1/2 (140)

(305)

Front View

(864)

(229)

INTAKE

VENT

EXHAUST

VENT

NOTE-Enclosed exhaust pipe is insulated with 1/2" (13mm) foam insulation. If intake and exhaust pipes are reversed, slit and remove foam insulation and reapply to other vent. ExĆ haust vent must be insulated.

Side View

Inches (mm)

OPTIONAL VENT TERMINATION FOR

Front View

INTAKE

AIR

(127)

EXHAUST VENT

INTAKE

MULTIPLE UNIT INSTALLATION

WALL TERMINATION KIT WTK

FIGURE 35

(305)

5Ć1/2 (140)

EXHAUST

AIR

COVER EXHAUST

EXHAUST

GRADE

Side View

VENT

VENT WITH

1/2 (13)

FOAM

INSULATION

AIR

12 MIN.

(305)

Above Grade

Side View

(102)

(305)

GRADE

EXHAUST VENT

8 MIN.

(203)

INTAKE

VENT

OUTSIDE WALL

GRADE

VENT TERMINATIONS

MODEL WTKX (30G79)

EXTENSION RISER FOR GRADE CLEARANCE

FIGURE 37

G26 VENTING IN EXISTING CHIMNEY

3" - 8"

8" - 12"

(203mm - 305mm)

(76mm-

203mm)

INTAKE

AIR

8 (203)

Minimum

Inches (mm)

12 (305)

Minimum

ABOVE GRADE

GRAD

VENT TERMINATIONS

MODEL WTK WALL TERMINATION KIT (30G28)

EXTENDED VENT FOR GRADE CLEARANCE

FIGURE 36

Page 24

3" - 8"

(76mm-

203mm)

NOTE-Do not discharge exhaust gases directly into any chimney or vent stack. If vertiĆ cal discharge through an existing unused chimney or stack is required, insert piping inside chimney until the pipe open end is above top of chimney and terminate as illusĆ trated. In any exterior portion of chimney, the exhaust vent must be insulated. An alterĆ nate method is to fill the chimney with vermiculite or equal to take advantage of its acoustic and thermal properties.

FIGURE 38

Page 25

LENNOXOEMPARTS.COM

Condensate Piping

This unit is designed for either rightĆ or leftĆside exit of conĆ densate piping. Condensate drain line should be routed only within the conditioned space to avoid freezing of conĆ densate and blockage of drain line. An electric heat cable should be used where condensate drain is exposed to unĆ conditioned areas. The following procedure is for all G26 units.

1 - Determine which side condensate will exit the unit.

2 - Connect 1/2" (13mm) plastic pipe plug (provided) in

the unused end of the condensate trap. Install plug so that it is sealed water tight yet able to be removed. Do not permanently seal the connection. Teflon tape is recommended to seal joint. See figure 40.

FLUE TRAP

UNIT CABINET

Y" CONNECTOR

HOSE BARB

ASSEMBLY

G26-1 and -2

Models

3 - Use the provided adapter (1/2" PVC x 1/2" MPT) and

the nipple (1/2" PVC) to carry drainage outside the cabinet. If a field substitute is needed, 1/2" CPVC x 1/2" MPT adapter and 1/2" CPVC is acceptable for use.

4 - Glue nipple to the adapter using the procedures outĆ

lined in the Joint Cementing Procedures" section. The nipple/adapter assembly should be connected in a nonĆpermanent manner and must be water tight. Teflon tape is recommended to seal the joint.

For RightĆHand Side Condensate Exit:

Install the nipple/adapter assembly from the outside of the cabinet and insert the adapter into the threaded opening in the condensate trap.

For LeftĆHand Side Condensate Exit:

Insert nipple/adapter assembly from the left hand side of the cabinet and through the combustion air blower mounting structure into the threaded openĆ ing in the condensate trap.

5 - Connect field supplied plumbing to nipple and route to

open drain. Plumbing should be vented to a point higher than the condensing coil. See figure 41.

DETAIL OF FLUE TRAP

BOOT OR CAP

RUBBER CONNECTOR

HOSE CLAMPS

FIGURE 39

CONDENSATE ASSEMBLY

(For left or right installation)

COMBUSTION AIR

BLOWER BRACKĆ

NIPPLE

ADAPTER

PLUG

FIGURE 40

CAUTION

Do not use copper tubing or existing copper condensate lines for drain line.

CONDENSATE PLUMBING

(Plumbing must be vented higher than coil.)

COLD HEADĆ

BOX

NIPPLE

ADAPTER

CONDENSATE TRAP

BOOT OR CAP

FIGURE 41

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LENNOXOEMPARTS.COM

DETAIL OF

FLUE TRAP

FLUE TRAP

HOSE BARB

G26 -3 THROUGH -6 MODEL CONDENSATE

REMOVAL PROCESS

COLD

HEADER

BOX

VENT

FLUE

DRAIN

HOSE

COMBUSTION

AIR BLOWER

HEADER BOX

CONDENSATE TRAP

Condensate Removal Process:

1- Condensate mixed with flue products

exits the coil and enters the cold headĆ er box.

2- Condensate and flue products are sepaĆ

rated. Flue products are drawn into the combustion air blower while condensate is drained into the header box condenĆ sate trap.

3- Flue products are expelled into the flue.

As flue products travel up and out, they cool and more condensate is produced.

4- Condensate travels down the walls of

the flue pipe and into drain hose.

5- Water drains down through the flue

drain hose and is emptied into the header box condensate trap.

6- When the cold header box condensate

trap is full, water begins draining out the condensate drain pipe.

7- An external condensate trap is not reĆ

quired, but a vent is required. The vent must extend above the height of the conĆ denser coil (approx. 1 inch above the top of the cold header box).

DETAIL OF COLD HEADER CONDENSATE TRAP

CONDENSATE

FROM COIL

COLD HEADER BOX

SIDE DETAIL OF

HEADER BOX

CONDENSATION

TRAP

6 - Connect condensate drain line (1/2" [13mm] SDR 11

plastic pipe or tubing) to condensate connection on drip leg assembly and route to open drain. CondenĆ sate line must be sloped downward away from drip leg to drain. If drain level is above drip leg, condenĆ sate pump must be used to condensate line. CondenĆ sate drain line should be routed within the conditioned space to avoid freezing of condensate and blockage of drain line. If this is not possible, a heat cable kit may

HOSE BARB

COIL OPENING BEHIND

COLD HEADER BOX

1/2"MPT PLUG

RUBBER BOOT OR CAP

FLUE DRAIN HOSE

FIGURE 42

1/2"PVC

1/2"MPT TO FEMALE

PVC PIPE ADAPTER

FRONT DETAIL OF

HEADER BOX

CONDENSATION

TRAP

be used on the condensate drip leg and line. Heating cable kit is available from Lennox in various lengths; 6ft. (1.8m) - kit no. 18K48; 24ft. (7.3m) - kit no. 18K49; and 50ft. (15.2m) - kit no. 18K50.

III-STARTĆUP A-Preliminary and Seasonal Checks

1 - Inspect electrical wiring, both field and factory installed

for loose connections. Tighten as required.

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2 - Check voltage at disconnect switch. Voltage must be

within range listed on the nameplate. If not, consult the

power company and have voltage condition corrected

before starting unit. 3 - Inspect condition of condensate traps and drain asĆ

sembly. Disassemble and clean seasonally.

B-Heating StartĆUp

FOR YOUR SAFETY READ BEFORE LIGHTING

CAUTION

Shock and burn hazard. G26 units are equipped with the SureLight ignition system. Do not attempt to light manually.

WARNING

Do not use this furnace if any part has been underĆ water. Inspect the furnace and replace any part of the control system and any gas control which has been under water.

How To Operate Gas Valve (Figure 43)

WARNING

If you do not follow these instructions exactly, a fire or explosion may result causing property damage, personal injury or loss of life.

1 - STOP! Read the safety information at the beginning of

this section. 2 - Set thermostat to lowest setting. 3 - Turn off all electrical power to furnace. 4 - This appliance is equipped with an ignition device

which automatically lights the burner. Do not try to

light the burner by hand. 5 - Remove unit access panel. 6 - On Honeywell VR8204 gas valves, turn knob on gas

valve clockwise

gas valves, move switch to OFF. Do not force. See figĆ

ure 43.

HONEYWELL VR8204 SERIES GAS VALVE

to OFF. For White Rodgers 36E

WARNING

If overheating occurs or if gas supply fails to shut off, shut off the manual gas valve to the appliance before shutting off electrical supply.

CAUTION

Before attempting to perform any service or mainĆ tenance, turn the electrical power to unit OFF at disconnect switch.

BEFORE LIGHTING smell all around the appliance area for gas. Be sure to smell next to the floor because some gas is heavier than air and will settle on the floor.

Use only your hand to push in or turn the gas control knob. Never use tools. If the knob will not push in or turn by hand, do not try to repair it, call a qualified service technician. Force or attempted repair may result in a fire or explosion.

G26 units are equipped with the SureLight ignition system. DO NOT attempt to manually light burners on this furnace. Each time thermostat calls for heat, burners will be automatiĆ cally lit. The ignitor does not get hot when there is no call for heat on units with SureLight ignition system.

OFF

GAS VALVE SHOWN IN OFF POSITION

WHITE RODGERS

36E GAS VALVE

GAS VALVE

SHOWN

IN OFF

POSITION

7 - Wait five (5) minutes to clear out any gas. If you then

smell gas, STOP! Immediately call your gas supplier

from a neighbor's phone. Follow the gas supplier's inĆ

structions. If you do not smell gas go to next step. 8 - For Honeywell VR8204 gas valves, turn knob on

valve counterclockwise to ON. For White

Rodgers 36E gas valves, move switch to ON. 9 - Replace unit access panel. 10- Turn on all electrical power to unit. 11- Set thermostat to desired setting.

NOTE-When unit is initially started, steps 1 through 11 may need to be repeated to purge air from pilot line.

NOTE-On initial start-ups and when condensate trap is dry, unit may turn itself off and on to allow condensate trap to fill. This is normal operation.

FIGURE 43

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LENNOXOEMPARTS.COM

12- If the furnace will not operate, follow the instructions

To Turn Off Gas To Unit" and call your service techniĆ cian or gas supplier.

To Turn Off Gas To Unit

1 - Set thermostat to lowest setting. 2 - Turn off all electrical power to unit if service is to be

performed. 3 - Remove heat section access panel. 4 - On Honeywell VR8204 gas valves, turn knob on gas

valve clockwise to OFF. For White Rodgers 36E

gas valves, move switch to OFF. Do not force. 5 - Replace unit access panel.

C-Safety or Emergency Shutdown

Turn off unit power. Close manual and main gas valves.

D-Extended Period Shutdown

Turn off thermostat or set to UNOCCUPIED" mode. Close all gas valves (both internal and external to unit) to guaranĆ tee no gas leak into combustion chamber. Turn off power to unit. All access panels, covers and vent caps must be in place and secured.

Refer to Maintenance" section of this manual for instrucĆ tions on how to prepare condensate assembly for exĆ tended period shutdown.

IV-HEATING SYSTEM SERVICE CHECKS

A-A.G.A./C.G.A. Certification

All units are A.G.A. and C.G.A. design certified without modifications. Refer to the G26 Operation and Installation Instruction Manual Information.

B-Exhaust CO2 and CO content

Carbon Dioxide is a colorless and odorless gas produced in small amounts by all furnaces, including the G26, during combustion process. When the unit is properly installed and operating normally, the CO2 content of the exhaust is between 6.0% and 8.0% for natural gas and between

7.5% and 9.5% for L.P. gases. CO content will be less than

0.04% regardless of the gas used. If unit appears to be opĆ erating normally at or beyond the upper limit of the CO range, the unit should be checked for abnormally high CO.

Testing for abnormally high CO

One method for testing the CO ach CO2 test with the Fyrite CO2 indicator. Other methods of testing CO2/CO are available. Closely follow the instrucĆ tions included in the test kit you choose. Follow the proceĆ dure below in order to check CO2/CO on the G26 furnace. 1 - Drill size "R" or 11/32 in. on the exhaust vent, just exitĆ

ing the cabinet and tap 1/8-27 NPT. This hole will be

used to draw your CO2/CO sample. 2 - Install a hose barb connector into test hole. 3 - Attach end of Fyrite sampling tube to hose barb. 4 - Set thermostat to highest setting and allow unit to run

15 minutes. 5 - When CO2/CO testing is complete, turn off unit, reĆ

move hose barb from exhaust vent and use a1/8"

plastic plug to close off port.

/CO content is the BacharĆ

and CO.

C-Gas Piping

Gas supply piping should not allow more than 0.5"W.C. drop in pressure between gas meter and unit. Supply gas pipe must not be smaller than unit gas connection. See gas pipe capacity table on page 6 of this manual.

Compounds used on gas piping threaded joints should be resistant to action of liquefied petroleum gas.

D-Testing Gas Piping

When pressure testing gas lines, the gas valve must be disconnected and isolated. Gas valves can be damaged if subjected to more than 0.5psig (14" W.C.). See figure 44. If the pressure is equal to or less than 0.5psig (14"W.C.), use the manual shut-off valve before pressure testing to isoĆ late furnace from gas supply.

GAS PIPING TEST PROCEDURE (TYPICAL)

MANUAL MAIN SHUT-OFF

VALVE WILL NOT HOLD

NORMAL TEST PRESSURE

FURNACE

ISOLATE

GAS VALVE

Page 28

CAP

GAS VALVE WILL NOT HOLD TEST PRESSURE IN

EXCESS OF 0.5 PSIG (14"W.C.)

FIGURE 44

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LENNOXOEMPARTS.COM

LEFT SIDE PIPING

MANUAL MAIN

SHUT-OFF

VALV E

GAS VALVE

RIGHT SIDE PIPING

FIGURE 45

GAS VALVE

(STANDARD)

Do not use matches, candles, flame or any other source of ignition to check for gas leaks.

E-Testing Gas Supply Pressure

When testing supply gas pressure, connect test gauge to inlet pressure tap (field provided). See figure 44. Check gas line pressure with unit firing at maximum rate. Low pressure may result in erratic operation or underfire. High pressure can result in permanent damage to gas valve or overfire. For natural gas units, operating pressure at unit gas connection must be between 4.5" W.C. and 13.0" W.C. For L.P. gas units, operating pressure at unit gas connecĆ tion must be between 8.0" and 13.0" W.C.

On multiple unit installations, each unit should be checked separately, with and without units operating. Supply presĆ sure must fall within range listed in previous paragraph.

F-Check Manifold Pressure

Manifold Operating Pressure is the manifold pressure measured during normal operation (sensing burner box pressure). Manifold Absolute Pressure is the manifold pressure measured when the gas valve regulator is operĆ ating at factory preset level (sensing atmospheric presĆ sure).

After line pressure has been checked and adjusted, check manifold absolute pressure. Move pressure gauge to outĆ let pressure tap located on unit gas valve (GV1). Checks of manifold absolute pressure are made as verification of propĆ er regulator adjustment.

Manifold operating pressure for the G26 can be measured at any time the gas valve is open and is supplying gas to the unit. Normal manifold operating pressure for natural gas units is 2.5 to 3.5 in. w.c (see figure 21). For LP/propane gas the correct manifold operating pressure is 7.5 in. w.c. (see figure 22).

IMPORTANT

For safety, connect a shutĆoff valve between the manometer and the gas tap to permit shut off of gas pressure to the manometer.

IMPORTANT

In case emergency shutdown is required, turn off the main shutĆoff valve and disconnect the main power to unit. These controls should be properly labeled by the installer.

When checking piping connections for gas leaks, use preĆ ferred means. Kitchen detergents can cause harmful corroĆ sion on various metals used in gas piping. Use of a specialty Gas Leak Detector is strongly recommended. It is available through Lennox under part number 31B2001. See Corp. 8411-L10, for further details.

Page 29

The gas valve is factory set and should not require adjustĆ ment. See table 9. Also, gas valve regulation varies with burner box pressure (figures 21 and 22).

*Manifold Absolute Pressure Measurement and AdjustĆ ment

1 - Connect test gauge to outlet tap on gas valve. 2 - Disconnect pressure sensing hose from gas valve

and plug hose. Leave hose barb on valve open to atĆ

mosphere. See figure 46. 3 - Start unit and allow 5 minutes for unit to reach steady

state.

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MANIFOLD CHECK

G26 Unit

GAS

VALV E

SENSING

HOSE

GAS

VALV E

TOP VIEW GAS VALVE DETAIL

HOSE

BARG

OUTLET

PRESSURE

TAP

GAS

PIPING

FIGURE 46

4 - While waiting for the unit to stabilize, notice the flame.

Flame should be stable and should not lift from burner. Natural gas should burn blue. L.P. gas should burn mostly blue with some orange streaks.

5 - After allowing unit to stabilize for 5 minutes, record

manifold pressure and compare to values given in table 9. Regulator cap must be installed when reading pressures.

TABLE 9

GAS VALVE REGULATION*

Unit (Fuel)

Natural L.P.

Absolute Pressure (outlet) in. W.C.

3.5 +0.3

7.5 +0.7

NOTE-Shut unit off and remove manometer as soon as an accurate reading has been obtained. Take care to replace pressure tap plug.

NOTE-During this test procedure, the unit will be overfiring:

 Operate unit only long enough to obtain accurate readĆ

ing to prevent overheating heat exchanger.

 Attempts to clock gas valve during this procedure

will be inaccurate. Measure gas flow rate only during normal unit operation.

6 - When test is complete remove obstruction from hose

and return hose to gas valve barb.

WARNING

Fire and explosion hazard. These instructions MUST be followed exactly. Can cause a fire or explosion resulting in property

damage, personal injury or loss of life.

G- Proper Gas Flow (Approximate)

Furnace should operate at least 5 minutes before checkĆ ing gas flow. Determine time in seconds for two revoluĆ tions of gas through the meter. (Two revolutions assures a more accurate time.) Divide by two and compare to time in table 10 below. Adjust manifold pressure on gas valve to match time needed.

NOTE- To obtain accurate reading, shut off all other gas appliances connected to meter.

TABLE 10

GAS METER CLOCKING CHART

Seconds for One Revolution Natural LP

1 cu ft

Dial

2 cu ft

Dial

1 cu ft

Dial

2 cu ft

DIAL

-50 72 144 180 360

-75 48 96 120 240

-100 36 72 90 180

-125 29 58 72 144

Natural-1000 btu/cu ft LP-2500 btu/cu ft

H-High Altitude Derate

Units are selfĆcompensating for altitude and do not require kits or adjustment when installed below 7500 ft. elevation. Manifold pressure should remain the same for both natural and propane. If unit is installed at an altitude higher than 7500 feet (2248 m), refer to local codes.

NOTE-This is the only permissible field derate for this appliance.

IMPORTANT

For safety, shut unit off and remove manometer as soon as an accurate reading has been obtained. Take care to replace pressure tap plug.

I-Flame Signal

A 20 microamp DC meter is needed to check the flame sigĆ nal on the SureLight and Johnson G776 ignition control. Use a flame signal transducer (part number 78H5401) available from Lennox to measure the flame signal.

Flame (microamp) signal is an electrical current which passes from the ignition control through the sensor elecĆ trode during unit operation. Current passes from the senĆ sor through the flame to ground to complete a safety cirĆ cuit.

To Measure Flame Signal:

1 - Set the volt meter to the DC voltage scale. Insert transĆ

ducer into the VDC and common inputs. Observe corĆ

rect polarities. Failure to do so results in negative (-)

values. 2 - Turn off supply voltage to control. 3 - Disconnect flame sensor lead from terminal of ignition

control.

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LENNOXOEMPARTS.COM

4 - Connect (+) lead of transducer to ignition control senĆ

G26 1 and 2

and -6 models

sor connection. See figure 47.

5 - Connect (-) lead of the transducer to sensor wire. See

figure 47.

6 - Turn supply voltage on and close thermostat contacts

to cycle system.

7 - When unit lights, read voltage on meter display. ReĆ

member 1 DC volt = 1 DC microamp.

TABLE 11

FLAME SIGNAL MICROAMPS

G26 -1 and -2

models

Normal 0.25

Minimum 0.15

Normal u0.7

G26 -3, -4, -5

Low v0.7

Minimum 0.15

FLAME SIGNAL TEST

DIGITAL

METER

SENSOR

WIRE

TRANSDUCER

(+)

(-)

FLAME SENSOR

SENSE" TERMINAL

IGNITION

CONTROL

(G776 SHOWN)

FIGURE47

V-TYPICAL OPERATING CHARACTERISTICS A-Blower Operation and Adjustment

NOTE- The following is a generalized procedure and does not apply to all thermostat controls.

1 - Blower operation is dependent on thermostat control

system.

2 - Generally, blower operation is set at thermostat subĆ

base fan switch. With fan switch in ON position, blower operates continuously. With fan switch in AUTO posiĆ tion, blower cycles with demand or runs continuously while heating or cooling circuit cycles.

3 - In all cases, blower and entire unit will be off when the

system switch is in OFF position.

B-Temperature Rise

Temperature rise for G26 units depends on unit input, blower speed, blower horsepower and static pressure as marked on the unit rating plate. The blower speed must be set for unit operation within the range of AIR TEMP. RISE

°F" listed on the unit rating plate.

To Measure Temperature Rise:

1 - Place plenum thermometers in the supply and return

air plenums. Locate supply air thermometer in the first horizontal run of the plenum where it will not pick up raĆ diant heat from the heat exchanger.

2 - Set thermostat to highest setting.

3 - After plenum thermometers have reached their highĆ

est and steadiest readings, subtract the two readings.

The difference should be in the range listed on the unit

rating plate. If the temperature is too low, decrease

blower speed. If temperature is too high, first check

the firing rate. Provided the firing rate is acceptable, inĆ

crease blower speed to reduce temperature. To

change blower speed taps see the Blower Speed Taps

section in this manual.

C-External Static Pressure

1 - Measure tap locations as shown in figure 48.

2 - Punch a 1/4" diameter hole

in supply upstream of evapĆ

orator and return air pleĆ

STATIC PRESSURE

TEST

MANOMETER

nums. Insert manometer

hose flush with inside edge

of hole or insulation. Seal

around the hose with perĆ

magum. Connect the zero

G26 UNIT

FIGURE 48

end of the manometer to the discharge (supply) side

of the system. On ducted systems, connect the other

end of manometer to the return duct as above. For

systems with non-ducted returns, leave the other end

of the manometer open to the atmosphere. 3 - With only the blower motor running and the evaporator

coil dry, observe the manometer reading. Adjust blowĆ

er motor speed to deliver the air desired according to

the job requirements.

4 - Pressure drop must not exceed 0.5" W.C.

5 - Seal around the hole when the check is complete.

D-Blower Speed Taps Leadless Motors

-1, -2, -3 and -4 Models

Blower speed tap selection on unleaded motors is accomĆ plished by changing the taps at the blower motor harness connector. Disconnect harness connector from motor to exĆ pose speed selectors. Blower speed selections are listed on table 12.

To Change Blower Speed Uleaded Motors

1 - Turn off electric power to furnace. 2 - Remove blower access door. 3 - Disconnect blower motor harness from motor. 4 - Pull harness connector and wires through blower acĆ

cess panel opening. 5 - Select desired speeds for heating and cooling. (Red =

heating, Black = cooling, White = common). 6 - Depress harness connector tab to release wire termiĆ

nal. Select connector location for new speed (refer to

unit wiring diagram). Insert wire terminal until it is seĆ

curely in place. See figure 50. 7 - Replace harness connector to motor .

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To Remove Blower:

1- Turn off line voltage power. Unplug

J69 from P69 located on blower deck.

2- Disconnect thermostat wiring conĆ

nections by removing low voltage terminal strip.

3- Disconnect J58/P58 located on blowĆ

er deck.

4- Disconnect J43/P43 from blower

motor.

5- Loosen screws (2) and remove conĆ

trol box from unit. Holes are slotted so screws do not need to be removed.

6- Remove screws (2) and remove

blower from unit.

FIGURE 49

BLOWER SPEED TAP SELECTION

HARNESS

CONNECTOR

DEPRESS TAB TO RELEASE WIRE TERMINAL. SELECT CONNECTOR LOCATION FOR NEW SPEED (REFER TO UNIT WIRING DIAGRAM). INSERT WIRE UNTIL IT IS SECURELY IN PLACE.

FIGURE 50

TABLE 12

MOTOR

E-Blower Speed Taps Leaded Motors

-5 and -6 Models

Blower speed tap changes are made on the SureLight control board. See figure 10. Unused taps must be seĆ cured on dummy terminals "PARK M1" and or "PARK M2" on the SureLight board. The heating tap is connected to the "ACB HEAT " terminal and the cooling tap is connected to the "ACB COOL" terminal. The continuous blower tap is connected to the "ACB LOW" terminal. To change existing heat tap, turn off power then switch out speed tap on "ACB HEAT" with tap connected to "PARK M1" or "PARK M2". See table 13 for blower motor tap colĆ ors for each speed.

VI-MAINTENANCE

Retainers for factory supplied return air filter are shown in figure 51.

BOTTOM RETURN FILTER

REAR FILTER CLIP

SIDE FILTER CLIPS (2)

RETURN AIR

OPENING

FURNACE

BACK

TABLE 13

Page 32

FURNACE

FRONT

FURNACE

BASE BOTTOM

FIGURE 51

A-Filters

At the beginning of each heating season, the system should be checked as follows: 1 - Filters should be inspected monthly and must be

cleaned or replaced when dirty to ensure proper furĆ

nace operation.

Page 33

LENNOXOEMPARTS.COM

2 - Reusable foam filters used with the G26 can be

washedwith waterand milddetergent. Whendry,they should be sprayed withfilterhandicoater prior to reinstallation. Filter handicoater is RP Products coating no. 418andis available as Lennoxpart no. P-8-5069.

3 - If replacement is necessary, order Lennox part no.

31J81 for 14” x 25” (356 x 635mm) filter for G26-50 and -75 units and P-8-7831 for 20” x 25” (508 x 635mm) filter for G26Q4/5-75,G26-100 and -125 units.

B-Cleaning Heat Exchanger and Burners

Ifcleaning theheatexchanger becomesnecessary,follow the below procedures and refer to figure 1 when disassemblingunit. Usepapers orprotective coveringin frontof furnace while removing heat exchanger assembly.

1 - Turnoff electrical and gaspowersupplies to furnace. 2 - Remove upper and lower furnace access panels. 3 - Remove four (4) screws around air intake fitting and

lift intake pipe up and away.

4 - Loosen hose clamp securing top of flue transition to

bottomof fluecollar. Removescrew securingfluecollar to top cap and lift exhaust pipe and flue collar up and away.

5 - If electrical field make-up box is located inside the

unit, it must be removed. 6 - Remove gas supply line connected to gas valve. 7 - Mark all gas valve wires and disconnect them from

valve. Mark and remove wires from flame roll-out

switch. 8 - Remove top cap of unit. 9 - For -1 and -2 units, mark and disconnect spark and

sensorwirefrom ignitioncontrol. For -3units, remove

sensor wire from SureLightcontrol.Disconnect2-pin

plug from the ignitor.

10- Mark and disconnect pressure switch tubing from

both sides of the pressure switch.

11- Loosen two (2) screws holding gas manifold support

at vestibule panel.

12- Remove four (4) burner box screws at the vestibule

panelandremove burnerbox andgasvalve/manifold

assembly with bracket.

13- Drain condensate trap. Disconnect condensate line

from the outside of unit. Remove condensate line

from condensate trap by turning the adapter fitting

counterclockwise. Thefittinghas standard righthand

threads.

14- Disconnect the drain hose from the flue transition to

the elbow on the cold header (collector) box trap. On

-1and -2units removetwo(2)screwfrom flue”Y” trap

at cabinet from door flange.

15- Disconnect the 2-pin plug from the combustion air

blower at the blower deck. Remove four (4) screws fromcombustionairblowerandremovefluetransition and blower assembly from cabinet. Take care not to lose the combustion air orifice.

16- Disconnect 9-pin plug from the blower compartment

at the blower deck. 17- Remove 9-pin plug above the blower deck. 18- Remove the limitswitch andthe pressure switchfrom

the vestibule panel. 19- Remove two (2) screws from the front cabinet flange

attheblowerdeck.Remove frontscrewsfrom cabinet

at blower deck on left and right sides. Cabinet sides

must be slightly spread to clear heat exchanger pas-

sage. 20- Remove screws along vestibule sides and bottom

which secure vestibule panel and heatexchanger as-

sembly to cabinet. Remove heat exchanger then re-

movecold endheaderbox. Removebafflesfrom con-

denser tubes. 21- Back wash heatexchangerwith soapy watersolution

or steam. If steam is used it must be below 275_F

(135_C) .

22- Thoroughly rinse anddrain theheat exchanger.Soap

solution can be corrosive so take care that entire as-

sembly is completely rinsed. 23- Re-install heat exchanger into cabinet making sure

that the clamshells of the heat exchanger assembly

areresting inthe notchesof thesupport locatedat the

rear of the cabinet. This can be viewed by removing

the indoor blower and examining through the blower

opening. 24- Re-secure the supporting screwsalongthe vestibule

sides and bottom to the cabinet. 25- Re-install cabinetscrewson sides and front flangeat

blower deck. 26- Re-install the limit switch and pressure switch on the

vestibule panel. 27- Re-install 9-pin plug to blower deck and connect it to

the 9-pin plug from below the blower deck. 28- Re-install the combustion air blower. Be careful that

theplastic orificeontheblowerinlet hasnot fallenout.

Seefigure 1.Reconnectthe2-pinplug tothe wirehar-

ness. Re-install the flue transition in the cabinet and

re-attach the drain tube. Route the drain tube below

the combustion air blower housing and to the elbow

on thecold header (collector)box trap. Seefigure 23. 29- Re-install condensate line with adapter to conden-

sate trap. Use freshTeflon tape to ensurealeak-free

joint. Re-connect to condensate line outside of the

unit.

Page 33

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BURNER ACCESS/REMOVAL

BURNER MOUNTING

BRACKET

PATCH PLATE

Simplified Burner Removal:

1- Remove cover by loosening

bottom screws (2) and reĆ moving cover front screws (5).

2- Remove pilot tube, spark

wire and sensor wire. ReĆ move gas valve and manifold assembly.

3- Remove burner assembly.

30- ReĆinstall the burner box. Tighten the screws holding

the support bracket. It is important that the glass fiber gasket not be damaged so it will provide a continuous seal between the burner box and the vestibule panel.

31- With the pressure switch oriented on the right, reconĆ

nect pressure switch tubing by connecting the tubing from the burner box to the barb on the bottom and the tubing from the combustion air blower to the barb on

the top. See figure 23. 32- Reconnect the sensor and ignitor wires. 33- ReĆinstall top cap to unit. 34- ReĆinstall electrical connections to gas valve. Orange

wire to M1 and yellow wire to C2. Reconnect wires to

flame rollĆout switch.

NOTE - Unit is polarityĆsensitive. 120V supply wiring

must be installed correctly.

35- Reconnect main gas line to gas valve. 36- ReĆinstall field makeĆup box if removed. 37- ReĆinstall exhaust pipe/flue collar and secure flue colĆ

lar to the unit top cap using existing screw. Insert the

bottom of the flue collar into the top of the flue transiĆ

tion and tighten hose clamp. 38- ReĆinstall intake pipe fitting to burner box with screws. 39- Replace both upper and lower access panels. 40- Refer to instruction on verifying gas and electrical conĆ

nections when reĆestablishing supply. 41- Following lighting instructions from installation manuĆ

al, light and run unit for 5 minutes to ensure heat exĆ

changer is clean, dry and operating safely.

BARBED PRESSURE

SWITCH ORIFICE

FIGURE 52

PATCH PLATE

Cleaning the Burner Assembly

1 - Turn off electrical and gas power supplies to furnace.

Remove upper and lower furnace access panels.

2 - Disconnect the gas supply line to gas valve. DependĆ

ing on gas plumbing installation, the gas manifold may move aside enough that breaking the union may not be necessary.

3 - Remove five (5) screws from edges of burner box

cover. G26-50 units have only four (4) screws.

4 - Loosen two (2) screws on bottom of burner box front.

The cover is key holed at these screw point so screws do not need to be removed. Pull off cover and set aside.

6 - On -1 and -2 units disconnect pilot line at the gas

valve. On all units mark all gas valve wires and disĆ connect them from valve.

7 - ON -1 and -2 units mark and disconnect spark and

sensor wire from the burner box at the ignition control. On -3 mark and disconnect sensor wires from the burner box at the SureLight control. Disconnect 2Ćpin plug from the ignitor at the burner box.

8 - Loosen two (2) screws at the gas manifold support

bracket.

9 - Pull on the left side of the gas manifold and follow with

tension to the right side. The manifold support bracket will be free of the mounting screws on the vestibule panel. Set the gas manifold/gas valve assembly aside. Take care not to damage foam gaskets on each end of the gas manifold.

10- Using a 1/4" nut driver, remove the burner mounting

screws from underneath the burners.

UNIT VEST PANEL

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11- While supporting pilot, ignitor and sensor wires (-1,-2

units) or ignitor and sensor lines (-3 units) at the gromĆ

met, grasp burners and simultaneously pull burners

and grommet out of the burner box.

12- Remove ignitor and sensor or pilot bracket assemĆ

blies from burners using a 1/4" nut driver to remove

two screws from each bracket.

13- Clean burner by running a vacuum with a soft brush atĆ

tachment over face of burners. Visually inspect inside of

burners and crossovers for any blockage caused by forĆ

eign matter. Remove any blockage.

14- ReĆinstall ignitor and sensor bracket assemblies on

burners.

NOTE - Ignitor or pilot must be installed on the opposite side of the burner from the metal button protrusions. Screws which attached the ignitor bracket must be installed from the same side as the ignitor and through the bracket to engage in the smaller holes located in the burner. The correc t burn er ori entation is with met al butĆ ton protrusions always pointing up.

15- Replace burner ignitor assembly back into burner box

so that grommet groove fits back into sheet metal

notch and makes a good seal. The burners sit on top

of the burner box flanges. Make certain that the

screws from underneath the box pass through the

larger holes in the flange and engage in the smaller

holes in the burner. ReĆinstall the two screws.

16- ReĆinstall the gas manifold/gas valve assembly by first

inserting the right hand side of the gas manifold into the

burner box. Swing left side of manifold into box while

engaging support bracket to vestibule panel screws.

Check that foam gaskets are providing a seal around

each end of the gas manifold. All gas orifices should be

engaged. If at this point the burners were mounted in

the wrong holes, this needs to be corrected. The saddle

brackets on the gas manifold should be flush with the

front surfaces on the burner box sides.

17- Inspect the dual layered metal pieces at the front lip of

the cover. These pieces must sandwich around the

metal. ReĆinstall burner box cover.

18- ReĆinstall the screws to secure the burner box cover.

Make sure screws are tight to ensure a leak tight burnĆ

er box. Tighten the two screws underneath the box.

Again, inspect the grommet to ensure a tight seal.

19- Tighten the two screws holding the manifold bracket

to the vestibule panel.

20- ReĆinstall the electrical connections to the gas valve.

Orange wire to M1 and yellow wire to C2.

21- On -1 and -2 units re-install the spark wire (larger of

the two) to the barbed connector at the ignition conĆ trol. Re-install the sensor wire to the spade connector on the ignition control. On -3 units reĆinstall the 2Ćpin ignitor plug at the burner box. ReĆinstall sensor line to ignition control spade connector.

22- Reconnect gas line to gas valve. On -1 and -2 units

reconnect pilot line to gas valve. 23- Replace lower access panel. 24- Following lighting instructions and gas line connecĆ

tion test procedures from installation manual. 25- Replace upper access panel.

C-Supply Air Blower

1 - Check and clean blower housing and blower wheel. 2 - Motors are prelubricated for extended life; no further

lubrication is required.

D-Electrical

1 - Check all wiring for loose connections. 2 - Check circuit breaker located in unit control box. 3 - Check for correct voltage at unit (unit operating). 4 - Check ampĆdraw on blower motor.

Motor Nameplate_________Actual_________

5 - Check to see that heat (if applicable) is operating.

E-Intake and Exhaust Lines

Check intake and exhaust lines and all connections for tightness and make sure there is no blockage. Also check condensate line for free flow during operation.

F-Insulation

Outdoor piping insulation should be inspected yearly for deteĆ rioration. If necessary, replace with same materials.

G-Winterizing and Condensate Trap Care

1 - Turn off power to unit. 2 - Have a shallow pan ready to empty condensate water.

Avoid spilling water into the control box.

3 - Remove clamp from flue assembly and remove boot or

cap. Empty water from cap. Visually inspect bottom of flue assembly. Replace boot and clamp.

4 - Remove boot from condensate trap and empty water.

Inspect trap then replace boot.

Page 35

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VII-WIRING DIAGRAM, SEQUENCE OF OPERATION &TROUBLESHOOTING A-Field Wiring, Thermostat Connections

FUSED DISCONNECT SWITCH

TYPICAL G26-3 through -6 MODELS

(FURNISHED BY INSTALLER)

FIELD WIRING DIAGRAM

L1 N

GND

THERMOSTAT

GWRY

TO COMPRESSOR

CONTACTOR

FLAME

ROLLOUT

SWITCH

COMBUSTION

AIR PROVE

SWITCH

LIMIT

IGNITION

CONTROL

FIELD

MAKE-UP

BOX

GAS

VALV E

COMBUSTION

AIR BLOWER

TRANSFORMER

CONTROL

BOX

GWYCR

SURELIGHT CONTROL

DOOR

INTERLOCK

SWITCH

FIELD INSTALLED CLASS II 24V VOLTAGE FIELD INSTALLED LINE VOLTAGE

FIGURE 53

G26 and CONDENSING UNIT

THERMOSTAT DESIGNATIONS

(Refer to specific thermostat and outdoor unit.)

J69

BLACK

WHITE

BROWN

TO ACCESSORY IF USED.

(ELECTRONIC AIR CLEANER)

IF NOT NEEDED, DO NOT INSTALL

ACCESSORY WIRE IN J69.

G26

Condensing UnitThermostat

Furnace

HS UNIT

COOLING

COMPRESSORā

COMPRESSOR

INDOOR BLOWER

HEAT

POWER

COMMON

HS UNIT

COMMON

FIGURE 54

Page 36

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LENNOXOEMPARTS.COM

B-Wiring Diagram G26 (-3 & -4 Shown)

Page 37

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LENNOXOEMPARTS.COM

HEATING SEQUENCE OF OPERATION

SURELIGHT CONTROL

NORMAL HEATING MODE ABNORMAL HEATING MODE

COMBUSTION AIR BLOWER ON FOR 1 SECOND.

SIGNAL IMPROPER

GROUND AT LED.

SIGNAL HOLDS

UNTIL UNIT IS

PROPERLY

GROUNDED.

POWER ON

CONTROL SELF-CHECK OKAY?

TURN INDUCER ON FOR 1 SECOND.

IS POLARITY REVERSED?

ROLLOUT SWITCH CLOSED?

(CONTINUOUS FLAME CHECK)

IS THERE

PROPER GROUND?

YES

BURNER OFF?

YES

NORMAL OPERATION:

LED #1 -- SLOW FLASH LED #2 -- SLOW FLASH

YES

IS VOLTAGE

ABOVE 75 VOLTS?

YES

GAS VALVE OFF. COMBUSTION AIR BLOWER ON.

GAS VALVE OFF. COMBUSTION AIR BLOWER OFF.

(RESET CONTROL BY TURNING MAIN POWER OFF.)

GAS VALVE OFF. COMBUSTION AIR BLOWER OFF.

SEQUENCE HOLDS UNTIL ROLLOUT SWITCH CLOSES.

GAS VALVE OFF. COMBUSTION AIR BLOWER ON.

INDOOR BLOWER ON.

LED #1 ALTERNATING FAST FLASH

LED#2 ALTERNATING FAST FLASH CHECK FOR BROKEN IGNITOR OR

OPEN IGNITOR CIRCUIT

INDOOR BLOWER DELAY OFF.

LED #1 ON LED #2 ON

POLARITY REVERSED.

LED #1 -- FAST FLASH

LED #2 -- SLOW FLASH

LOW VOLTAGE SIGNAL AT LED HOLDS

UNTIL VOLTAGE RISES ABOVE 75 VOLTS.

INDOOR BLOWER OFF WITH DELAY.

LED #1 -- ON. LED #2 -- SLOW FLASH.

INDOOR BLOWER ON HEATING SPEED.

LED #1 -- SLOW FLASH

LED #2 -- OFF

THERMOSTAT CALLS FOR HEAT:

LED #1 -- FAST FLASH LED #2 -- FAST FLASH

YES

IS COMBUSTION AIR

PRESSURE SWITCH OPEN?

YES

IS COMBUSTION AIR BLOWER ENERGIZED?

(HTG ACC TERMINAL IS ENERGIZED WITH C.A.B.)

YES

HAS COMBUSTION AIR PRESSURE

SWITCH CLOSED IN 2.5 MINUTES?

YES

15ĆSECOND COMBUSTION AIR BLOWER PREPURGE

INITIATED BY CLOSED PRESSURE SWITCH.

YES

CONTINUED NEXT PAGE

PRESSURE SWITCH IS IN WATCHGUARD MODE.

GAS VALVE OFF. COMBUSTION AIR BLOWER OFF.

IS 5ĆMINUTE RESET PERIOD COMPLETE?

COMBUSTION AIR BLOWER OFF.

INDOOR BLOWER OFF WITH DELAY.

(Sequence holds until pressure switch

closes or thermostat resets control.)

INDOOR BLOWER OFF WITH DELAY.

LED #1 -- OFF. LED #2 -- SLOW FLASH.

GAS VALVE OFF.

LED #1 OFF

LED #2 SLOW FLASH

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LENNOXOEMPARTS.COM

HEATING SEQUENCE CONTINUED

NORMAL HEATING MODE ABNORMAL HEATING MODE

15ĆSECOND COMBUSTION AIR BLOWER PREPURGE

INITIATED BY CLOSED PRESSURE SWITCH.

YES

IGNITOR WARMĆUP -- 20 SECONDS.

YES

4ĆSECOND TRIAL FOR IGNITION. GAS VALVE

OPENS. IGNITOR ENERGIZED FOR 1 SECOND

AFTER VALVE OPENS. BOARD 97L48 ONLY: IGNITOR

ENERGIZED FOR FULL 4-SECOND IGNITION TRIAL.

YES

FLAME STABILIZATION PERIOD.

4 SECONDS

FLAME RECTIFICATION CURRENT CHECK

CAN FLAME BE PROVEN WITHIN 4

SECONDS AFTER GAS VALVE OPENS?

(u0.15 microamps)

GAS VALVE OFF. COMBUSTION AIR BLOWER ON.

HAS CONTROL FAILED TO SENSE FLAME FOR

FIVE CONSECUTIVE TRIES DURING A SINGLE

WATCHGUARD MODE. GAS VALVE OFF.

LEDs SIGNAL WATCHGUARD FAILURE CODE.

IS 60ĆMINUTE RESET PERIOD COMPLETE?

INDOOR BLOWER OFF.

HEAT DEMAND?

YES

COMBUSTION AIR BLOWER OFF.

INDOOR BLOWER OFF WITH DELAY

YES

FLAME PRESENT?

YES

FLAME SIGNAL ABOVE 0.7 MICROAMPS?

YES

INDOOR BLOWER ON DELAY BEGINS. AFTER 45

SECOND DELAY, ACB HEAT SPEED AND ACC

TERMINAL IS ENERGIZED.

YES

PRIMARY AND SECONDARY LIMIT

SWITCHES CLOSED?

YES

ROLLOUT SWITCH CLOSED?

YES

COMBUSTION AIR PRESSURE

SWITCH CLOSED?

YES

THERMOSTAT DEMAND SATISFIED.

YES

LED #1 & #2 SIMULTANEOUS SLOW FLASHES.

YES

COMB. AIR BLOWER CONTINUES 5ĆSECOND POST

PURGE AFTER T'STAT DEMAND IS SATISFIED. INĆ

DOOR AIR BLOWER COMPLETES SELECTED OFF"

DELAY BEFORE SHUTTING OFF. ACB HEAT, HTG

ACC AND ACC TERMINALS DE-ENERGIZED.

COMBUSTION AIR BLOWER DE-ENERGIZED.

INDOOR BLOWER ON UNTIL SWITCH CLOSES.

HAS PRIMARY/SECONDARY LIMIT RESET?

(See table 2 DIAGNOSTIC CODES for limit reset operation)

GAS VALVE OFF. COMBUSTION AIR BLOWER OFF.

SEQUENCE HOLDS UNTIL ROLLOUT SWITCH CLOSES.

HAS CAB SWITCH CLOSED IN 2.5 MINUTES?

HAS CONTROL RESET IGNITION

SEQUENCE FOUR TIMES?

LOW FLAME SIGNAL

(Does not affect operation of control)

LED #1 -- SLOW FLASH

LED #2 -- FAST FLASH

GAS VALVE DE-ENERGIZED.

LED #1 -- SLOW FLASH. LED #2 -- ON.

IS LIMIT SWITCH CLOSED?

YES

INDOOR BLOWER OFF WITH DELAY.

LED #1 -- ON. LED #2 -- SLOW FLASH.

GAS VALVE DE-ENERGIZED.

COMBUSTION AIR BLOWER ON.

INDOOR BLOWER OFF WITH DELAY

LED #1 -- OFF. LED #2 -- SLOW FLASH.

5ĆMINUTE PRESSURE SWITCH

WATCHGUARD MODE.

YES

Page 39

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LENNOXOEMPARTS.COM

COOLING SEQUENCE OF OPERATION

SURELIGHT CONTROL

NORMAL COOLING MODE ABNORMAL COOLING MODE

POWER ON

IGNITION CONTROL MAIN POWER ON.

SIGNAL IMPROPER

GROUND AT LED.

SIGNAL HOLDS

UNTIL UNIT IS

PROPERLY

GROUNDED.

ROLLOUT SWITCH MONITORED CONTINUOUSLY.

CHECK FOR MAIN BURNER FLAME SENSE.

LED: SLOW FLASH RATE REMAINS UNCHANGED

CONTROL SELF DIAGNOSTIC CHECK.

IS CONTROL OPERATING NORMALLY?

YES

TURN INDUCER ON FOR 1 SECOND.

IS POLARITY REVERSED?

IS ROLLOUT SWITCH CLOSED?

IS MAIN BURNER FLAME OFF?

THROUGHOUT COOLING CYCLE.

THERMOSTAT CALLS FOR COOLING.

IS THERE

PROPER GROUND?

YES

IS VOLTAGE

ABOVE 75 VOLTS?

GAS VALVE OFF. COMBUSTION AIR BLOWER OFF.

INDOOR BLOWER OFF WITH NORMAL DELAY.

SIGNAL CIRCUIT BOARD FAILURE AT LED.

INTERRUPT MAIN POWER TO RESET CONTROL.

SIGNAL POLARITY REVERSED AT LED.

GAS VALVE OFF. COMBUSTION AIR BLOWER OFF.

INDOOR BLOWER OFF WITH NORMAL DELAY.

SIGNAL CIRCUIT BOARD FAILURE AT LED.

SEQUENCE HOLDS UNTIL ROLLOUT SWITCH CLOSES.

GAS VALVE OFF. COMBUSTION AIR BLOWER OFF.

INDOOR BLOWER OFF WITH NORMAL DELAY.

SIGNAL CIRCUIT BOARD FAILURE AT LED.

SEQUENCE HOLDS UNTIL FLAME IS NOT SENSED.

LOW VOLTAGE SIGNAL AT LET HOLDS

UNTIL VOLTAGE RISES ABOVE 75 VOLTS.

COMPRESSOR CONTACTOR AND SYSTEM FAN

ENERGIZED WITH 0ĆSECOND DELAY. ACB COOL

SPEED AND ACC. TERMINAL IS ENERGIZED.

THERMOSTAT OPENS.

COMPRESSOR OFF.

SYSTEM FAN AND ACC. TERM. OFF

WITH 0ĆSECOND DELAY.

Page 40

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LENNOXOEMPARTS.COM

CONTINUOUS LOW SPEED FAN SEQUENCE OF OPERATION

SURELIGHT CONTROL

LED: SLOW FLASH RATE REMAINS

UNCHANGED THROUGHOUT SEQUENCE.

MANUAL FAN SELECTION MADE AT THERMOSTAT.

CONTROL (G) ENERGIZES SYSTEM FAN AT ACB

LOW SPEED. ACC. TERMINAL IS ENERGIZED.

THERMOSTAT CALLS FOR HEAT (W).

NO YES

THERMOSTAT CALLS FOR COOLING.

YES

SYSTEM FAN SWITCHED TO ACB COOL

SPEED. ACC. TERM. REMAINS ON.

THERMOSTAT OPENS.

HTG ACC. TERM. ENERGIZES

WITH COMB. AIR BLOWER.

BOARD NO. 63K8901

SYSTEM FAN DE-ENERGIZED. SYSTEM FAN

ENERGIZES ON ACB HEAT SPEED AFTER

NORMAL DELAY.

BOARD NO. 24L85, 56L83, 97L48

SYSTEM FAN SWITCHES TO ACB HEAT SPEED

AFTER NORMAL DELAY (fan remains energized)

THERMOSTAT OPENS. COMBUSTION AIR

AND HTG ACC TERMINAL DE-ENERGIZE.

BOARD 63K89: SYSTEM FAN OFF. ACC. TERM.

OFF. (AFTER OFF DELAY COMPLETED).

BOARDS 24L85, 56L83 AND 97L48:

SYSTEM FAN SWITCHES TO

LOW SPEED AFTER NORMAL DELAY.

(fan remains energized)

MANUAL FAN SELECTION MADE AT THERMOSTAT.

CONTROL (G) ENERGIZES SYSTEM FAN AT ACB

LOW SPEED. ACC. TERM. ENERGIZED.

C-Heating Sequence of Operation

1 - When there is a call for heat, W1 of the thermostat enĆ

ergizes W of the furnace control with 24VAC.

2 - S10 primary limit switch and S47 rollout switch are

closed. Call for heat can continue.

3 - Surelight control energizes combustion air blower B6.

Combustion air blower runs until S18 combustion air prove switch closes (switch must close within 2-1/2 minutes or control goes into 5 minute Watchguard Pressure Switch delay). Once S18 closes, a 15-secĆ ond pre-purge follows.

4 - Surelight control energizes ignitor. A 20-second

warm-up period begins.

5 - Gas valve opens for a 4-second trial for ignition.

6 - Flame is sensed, gas valve remains open for the heat

call.

7 - After 45-second delay, Surelight control energizes inĆ

door blower B3.

8 - When heat demand is satisfied, W1 of the indoor therĆ

mostat de-energizes W of the Surelight control which

de-energizes the gas valve. Combustion air blower

B6 continues a 5-second post-purge period, and inĆ

door blower B3 completes a selected OFF time delay.

Page 41

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LENNOXOEMPARTS.COM

D- SureLight Control Trouble Shooting Guide

code LED#2 Slow Flash

ACTION 1

blower does not energize

120V field connection.

on operation

UPON INITIAL POWER UP, REMOVE ALL THERMOSTAT DEMANDS TO THE UNIT

PROBLEM: 1 UNIT FAILS TO OPERATE IN THE COOLING, HEATING, OR CONTINUOUS FAN MODE

Condition Possible Cause Corrective Action / Comments

1.1

- Both diagnostic lights fail to light up.

LED#1-Off LED#2-Off

1.2

- Diagnostic lights flash the roll-out

code.

LED#1-On, LED#2-Slow Flash

1.3

- On initial power-up the comb. air .

- Diagnostic lights flash the reverse

polarity code.

Main voltage 120V not supplied to unit.

Miswiring of furnace or improper connections.

Circuit breaker tripped or fails to close.

Door interlock switch failure.

Transformer Failure.

Failed control board.

Roll-out switch open.

Roll-out switch failure.

Miswiring or improper connections at roll-out switch.

Nine pin connector failure

120V main power polarity reversed.

1.1.1

1.1.2

1.1.3

1.1.4

1.1.5

1.1.6

1.2.1

1.2.2

1.2.3

1.2.4

1.3.1

ACTION 1 - Check 120V main voltage.

Determine cause of main power failure.

ACTION 1 - Check for correct wiring of 120V to power make up box and transformer.

ACTION 2 - Check 24V wiring to control board.

ACTION 1 - Replace circuit breaker if it is reset

but does not have continuity. ACTION 2 - If circuit breaker still trips, check for short.

ACTION 1 - Check that door switch is activated when door is closed. ACTION 2 - Check wire connections to switch, reĆ place loose connectors. ACTION 3 - Check continuity of switch in closed position. Replace if malfunctioning

ACTION 1 - Check that transformer output is 24V. Replace if malfunctioning

ACTION 1 - If all the above items have been checked, replace board.

ACTION 1 - Manually reset the roll-out switch by pushing the top button. ACTION 2 - Determine the cause of the roll-out switch activation before leaving furnace.

ACTION 1 - Check continuity across roll-out switch. Replace roll-out switch if switch is reset but does not have continuity.

- Check wiring connections to switch.

ACTION 1 - Check 9-pin connector for proper

connection to control board. ACTION 2 - Check continuity of the multi plug pin.

ACTION 1 - Check the 120V has line and neutral correctly input into control. ACTION 2 - Reverse the line and neutral at the 120V field connection.

LED#1-Fast Flash, LED#2-Slow Flash.

1.4

- On initial power up the combustion

air blower does not energize.

- Diagnostic lights flash normal power

on operation.

LED#1-Slow Flash

Open combustion air blower motor circuit.

Failed combustion air blower motor.

LED#2-Slow Flash

Page 42

1.4.1

1.4.2

ACTION 1 - Check for 120V to combustion air

blower. If no power, check wire and connecĆ tions.

ACTION 1 - If power is present at blower, replace blower.

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LENNOXOEMPARTS.COM

PROBLEM 1: UNIT FAILS TO OPERATE IN THE COOLING, HEATING, OR CONTINUOUS FAN MODE

Diagnostic lights flash the pressure

Condition Possible Cause Corrective Action / Comments

1.5

- On initial power-up the combustion

air blower remains energized.

- Diagnostic lights flash the improper

main ground.

LED#1-Alternating Fast Flash LED#2-Alternating Fast Flash

1.5.1

Improper ground to the unit.

1.5.2

6-Pin connector is improperly atĆ

tached to the circuit board.

1.5.3

Line voltage is below 75V.

ACTION 1 - Check that the unit is properly ground. ACTION 2 - Install a proper main ground to the unit

ACTION 1 - Check 6-pin connector for proper installation. Correctly insert connector into conĆ trol.

ACTION 1 - Check that the line voltage is above 75V. Determine cause of voltage drop and supĆ ply correct voltage to the control.

PROBLEM 2: UNIT FAILS TO OPERATE IN THE COOLING OR HEATING MODE, BUT COMBUSĆ TION AIR BLOWER OPERATES CONTINUOUS. UNITS WITH CONTROL BOARDS DATE CODED

AFTER NOV.1 1997, WILL OPERATE IN COOLING BUT NOT IN THE HEATING MODE, WITH COMĆ

BUSTION AIR BLOWER CYCLING 5 SECONDS ON 55 SECONDS OFF.

Condition Possible Cause Corrective Action / Comments

2.1

- On initial power-up the combustion

air blower remains energized.

- Diagnostic lights flash the improper

main ground.

- Units with control boards date

coded after Nov.1 1997; combustion air blower will cycle 5 seconds on 55 seconds off.

LED#1-Alternating Fast Flash LED#2-Alternating Fast Flash

2.1.1

Open ignitor circuit.

2.1.2

Broken or failed ignitor.

ACTION 1 - Check for correct wiring and loose connections in the ignitor circuit. Check multplug connections for correct installation.

ACTION 1 - Unplug ignitor and read resistance across ignitor. If resistance does not read beĆ tween 10.9 and 19.7 ohms, replace the ignitor.

PROBLEM 3: UNIT FAILS TO FIRE IN THE HEATING MODE, COMBUSTION AIR BLOWER DOES

Condition Possible Cause Corrective Action / Comments

3.1

- Unit operates with a cooling or conĆ

tinuous fan demand.

- Combustion air blower will not start

with a Heating demand.

- Diagnostic lights flash the limit failure

mode.

LED#1-Slow Flash, LED#2-On

3.2

- Unit operates with a cooling and conĆ

tinuous fan demand.

- Combustion air blower will not start

with a Heating demand.

- Diagnostic lights flash the pressure

switch failure code.

LED#1-Off, LED#2-Slow Flash

NOT ENERGIZE

3.1.1

Primary or secondary (if equipped)

limit open.

3.1.2

Miswiring of furnace or improper conĆ

nections at limit switch(es).

3.2.1

Miswiring of furnace or improper conĆ

nections to combustion air blower.

3.2.2

Pressure switch stuck closed.

ACTION 1 - Check continuity across switch(es). Switches reset automatically upon cool down. ACTION 2 - Check for restrictions on blower inlet air (including filter) and outlet air. Determine cause for limit activation before placing unit back in operation.

ACTION 1 - Check for correct wiring and loose connections. Correct wiring and/or replace any loose connections.

ACTION 1 - Check that the pressure switch is open without the combustion air blower operatĆ ing. Replace if malfunctioning

Page 43

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LENNOXOEMPARTS.COM

PROBLEM 3: UNIT FAILS TO FIRE IN THE HEATING MODE, COMBUSTION AIR BLOWER DOES

LED#1 Off

NOT ENERGIZE (CONT.).

Condition Possible Cause Corrective Action/Comments

3.3

- Unit operates with a cooling and conĆ

tinuous fan demand.

- Combustion air blower will not start

with a Heating demand.

Miswiring of furnace or improper conĆ

nections to combustion air blower.

3.3.1

ACTION 1 - Check for correct wiring and loose

connections. Correct wiring and/or replace any loose connections.

- Diagnostic lights flash the pressure

switch failure code 2.5 minutes after heating demand.

ACTION 1 - If there is 120V to combustion air blower and it does not operate, replace combusĆ tion air blower.

LED#1-Off,

3.3.2

Combustion air blower failure.

LED#2-Slow Flash

PROBLEM 4: UNIT FAILS TO FIRE IN THE HEATING MODE, COMBUSTION AIR BLOWER

ENERGIZES, IGNITOR IS NOT ENERGIZED.

Condition Possible Cause Corrective Action/Comments

4.1

- Unit operates with a cooling and

continuous fan demand.

- Combustion air blower energizes

with a heating demand.

- Diagnostic lights flash the pressure

switch failure code 2.5 minutes after heating demand.

LED#1-Off LED#2-Slow Flash

Pressure switch does not close due

to incorrect routing of the pressure

Pressure switch does not close due

to obstructions in the pressure lines.

Pressure switch lines damaged

Condensate in pressure switch line.

Pressure switch does not close due to a low differential pressure across

the pressure switch.

Wrong pressure switch installed in

the unit, or pressure switch is out of

Miswiring of furnace or improper conĆ

nections at pressure switch.

Pressure switch failure.

4.1.1

switch lines.

4.1.2

4.1.3

4.1.4

4.1.5

4.1.6

calibration.

4.1.7

4.1.8

ACTION 1 - Check that the pressure switch lines

are correctly routed. Correctly route pressure switch lines.

ACTION 1 - Remove any obstructions from the the pressure lines and/or taps.

ACTION 1 - Check pressure switch lines for leaks. Replace any broken lines.

ACTION 1 - Check pressure switch lines for conĆ densate. Remove condensate from lines. Check that the condensate lines are located correctly.

ACTION 1 - Check the differential pressure across the pressure switch. This pressure should exceed the set point listed on the switch. ACTION 2 - Check for restricted inlet and exĆ haust vent. Remove all blockage. ACTION 3 - Check for proper vent sizing and run length. See installation instructions.

ACTION 1 - Check that the proper pressure switch is installed in the unit. Replace pressure switch if necessary.

ACTION 1 - Check for correct wiring and loose connections. Correct wiring and/or replace any loose connections.

ACTION 1 - If all the above modes of failure have been checked, the pressure switch may have failed. Replace pressure switch and determine if unit will operate.

Page 44

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LENNOXOEMPARTS.COM

PROBLEM 5: UNIT FAILS TO FIRE IN THE HEATING MODE, COMBUSTION AIR BLOWER

ignite code.

ENERGIZES, IGNITOR IS ENERGIZED. (CONT.)

Condition Possible Cause Corrective Action/Comments

5.1

- Unit operates with a cooling and

continuous fan demand.

- Combustion air blower energizes

with Heating demand.

- Ignitor is energized but unit fails to

light.

LED#1-Alternating Slow Flash LED#2-Alternating Slow Flash

5.1.1

Check that gas is being supplied to

the unit.

5.1.2

Miswiring of gas valve or loose conĆ

nections at multi-pin control amp

plugs or valve.

5.1.3

Malfunctioning gas valve or ignition

control.

ACTION 1 - Check line pressure at the gas valve. Pressure should not exceed 13" WC for both natural and propane. Line pressure should read a minimum 4.5" WC for natural and 8.0"WC for propane.

ACTION 1 - Check for correct wiring and loose connections. Correct wiring and/or replace any loose connections.

ACTION 1 - Check that 24V is supplied to the gas valve approximately 35 seconds after heat demand is initiated. ACTION 2 - Replace the valve if 24V is supplied but valve does not open (check for excessive gas line pressure before replacing gas valve). ACTION 3 - Replace the control board if 24V is not supplied to valve.

PROBLEM 6: BURNERS LIGHT WITH A HEATING DEMAND BUT UNIT SHUTS DOWN

PREMATURELY

Condition Possible Cause Corrective Action/Comments

6.1

- Burners fire with a heating deĆ

mand.

- Burners light but unit shuts off prior

to satisfying T-stat demand.

- Diagnostic lights flash the pressure

switch code.

LED#1-Off LED#2-Slow Flash

6.2

- Combustion air blower energizes

with a heating demand.

- Burners light but fail to stay lit.

- After 5 tries the control diagnostics

flash the watchguard burners failed to ignite code.

LED#1-Alternating Slow Flash LED#2-Alternating Slow Flash

6.1.1

Wrong concentric vent kit used for

terminating the unit.

6.1.2

Condensate drain line is not draining

properly.

6.1.3

Low pressure differential at the presĆ

sure switch.

6.2.1

Sensor or sense wire is improperly

installed.

6.2.2

Sensor or sense wire is broken.

6.2.3

Sensor or sensor wire is grounded to

the unit.

6.2.4

Control does not sense flame.

ACTION 1 - Check vent termination kit installed. 1-1/2" dia. concentric vent (kit60G77) for 50 and 75 inputs and 2" dia. concentric vent (kit 33K97) for 100 &125 inputs.

ACTION 1 - Check condensate line for proper vent slope, and any blockage. Condensate should flow freely during operation of furnace. Repair or replace any improperly installed conĆ densate lines.

ACTION 1 - Check for restricted vent inlet or exĆ haust. Remove all blockage. ACTION 2: Check for proper vent sizing. See installation instructions.

ACTION 1 - Check that sensor is properly loĆ cated (page 10) and that the sense wire is properly attached to both the sensor and the control.

ACTION 1 - Check for a broken sensor. ACTION 2 - Test continuity across the sense

wire. If wire or sensor are damaged replace the component.

ACTION 1 - Check for resistance between the sensor rod and the unit ground. ACTION 2 - Check for resistance between the sensor wire and the unit ground.

ACTION 3 - Correct any shorts found in circuit.

ACTION 1 - Check the microamp signal from

the burner flame. If the microamp signal is beĆ low 0.70 microamps, check the sense rod for proper location or contamination. ACTION 2 - Replace, clean, or relocate flame sense rod. If rod is to be cleaned, use steel wool or replace sensor. DO NOT CLEAN ROD WITH SAND PAPER. SAND PAPER WILL CONTRIBUTE TO THE CONTAMINATION PROBLEM. NOTE: Do not attempt to bend sense rod.

Page 45

Page 46

LENNOXOEMPARTS.COM

PROBLEM 6: BURNERS LIGHT WITH HEATING DEMAND BUT UNIT SHUTS DOWN

ure.

flame failure

Condition Possible Cause Corrective Action/Comments

6.3

- Combustion air blower energizes

with a heating demand.

- Burners light.

- Roll-out switch trips during the

heating demand.

- Diagnostic lights flash roll-out failĆ

ure.

LED#1-On LED#2-Slow Flash

6.4

- Combustion air blower energizes

with a heating demand.

- Burners light roughly and the unit

fails to stay lit.

- Diagnostic lights flash watchguard

flame failure.

PREMATURELY (CONT.)

6.3.1

Unit is firing above 100% of the

nameplate input.

6.3.2

Gas orifices leak at the manifold conĆ

nection.

6.3.3

Air leakage at the connections beĆ

tween the primary heat exchanger,

secondary heat exchanger, and comĆ

bustion air blower.

6.3.4

Insufficient flow through the heat exĆ

changer caused by a sooted or reĆ

stricted heat exchanger.

6.3.5

Burners are not properly located in

the burner box.

6.4.1

Recirculation of flue gases. This conĆ

dition causes rough ignitions and opĆ

eration. Problem is characterized by

nuisance flame failures.

ACTION 1 - Check that the manifold pressure matches value listed on nameplate. See installaĆ tion instructions for proper procedure. ACTION 2 - Verify that the installed orifice size match the size listed on the nameplate or instalĆ lation instructions. ACTION 3 - Check gas valve sensing hose to inĆ sure no leaks are present. ACTION 4 - Check the input rate to verify rate matches value listed on nameplate.

ACTION 1 - Tighten orifice until leak is sealed. NOTE: Be careful not to strip orifice threads. ACĆ TION 2 - Check for gas leakage at the threaded

orifice connection. Use approved method for leak detection (see unit instructions).

ACTION 1 - Check for air leakage at all joints in the heat exchanger assembly. Condition will cause high CO2 with high CO. ACTION 2 - Seal leakage if possible (high temĆ perature silicon is recommended), replace heat exchanger if necessary, tag and return heat exĆ changer to proper Lennox personnel.

ACTION 1 - Check for sooting deposits or other restrictions in the heat exchanger assembly. Clean assembly as outlined in instruction manuĆ al. ACTION 2 - For G26 gas furnaces, check for proper combustion and flow. CO2 should meaĆ sure between 6.0% and 8.0% for NG and beĆ tween 7.5% and 9.5% for LP. CO should meaĆ sure below .04% (400PPM) in an air-free sample of flue gases for either NG or LP.

ACTION 1 - Check that the burners are firing into the center of the heat exchanger openings. CorĆ rect the location of the burners if necessary.

ACTION 1 - Check for proper flow of exhaust gases away from intake vent. Remove any obĆ stacles in front of the intake and exhaust vent which would cause recirculation. ACTION 2 - Check for correct intake and exĆ haust vent installation. See instructions

LED#1-Alternating Slow Flash LED#2-Alternating Slow Flash

Improper burner cross-overs

Page 46

6.4.2

ACTION 1 - Remove burner and inspect the

cross-overs for burrs, or any restriction or if crossover is warped. Remove restriction or reĆ place burners.

Page 47

LENNOXOEMPARTS.COM

PROBLEM 6: BURNERS LIGHT WITH HEATING DEMAND BUT UNIT SHUTS DOWN

sense code

6.5

- Combustion air blower energizes

with a heating demand.

- Burners light.

- Diagnostic lights flash watch guard

flame failure.

- NOTE" Unit might go into 60 minĆ

ute Watchguard mode depending on intermittent nature of sensor signal.

LED#1-Alternating Slow Flash LED#2-Alternating Slow Flash

PROBLEM 7: CONTROL SIGNALS LOW FLAME SENSE DURING HEATING MODE

Condition Possible Cause Corrective Action/Comments

7.0

- Unit operates correctly but the

diagnostic lights flash low flame

LED#1-Slow Flash LED#2-Fast Flash

PREMATURELY (CONT.)

6.5.1

Loose sensor wire connection

causes intermittent loss of flame sigĆ

nal.

7.1.1

Sense rod is improperly located on

the burner.

7.1.2

Sense rod is contaminated.

ACTION 1 - Check that the sensor is properly loĆ cated. ACTION 2 - Check that the sense wire is properĆ ly attached to both the sensor and the control. Pay extra attention to the pin connectors.

ACTION 1 - Check the sense rod for proper locaĆ tion on the burner. Properly locate the sense rod or replace if rod cannot be located correctly.

ACTION 1 - Check sense rod for contamination or coated surface. Clean the sense rod with steel wool or replace sensor. DO NOT USE SAND PAĆ PER TO CLEAN ROD. SAND PAPER WILL CONTRIBUTE TO THE CONTAMINATION PROBLEM.

PROBLEM 8: INDOOR BLOWER FAILS TO OPERATE IN COOLING, HEATING, OR CONTINUOUS

FAN MODE

Condition Possible Cause Corrective Action/Comments

8.0

- Indoor blower fails to operate in

continuous fan, cooling, or heating mode.

Miswiring of furnace or improper conĆ

nections at control or indoor blower

120V is not being supplied to the inĆ

door air blower or blower motor failĆ

Defective control board

8.1.1

motor.

8.1.2

ure.

8.1.3

ACTION 1- Correct wiring and/or replace any

loose connections. Check for correct wiring and loose connections.

ACTION 1 - Check for 120V at the various calls for indoor blower by energizing "Y", "G", and "W" individually on the low voltage terminal strip. Note that when "W' is energized, the blower is delayed 45 seconds. If there is 120V to each moĆ tor tap but the blower does not operate, replace the motor.

ACTION 1 - If there is not 120V when "Y", "G", or "W" is energized, replace the control.

PROBLEM 9: RF STATIC DURING TIME FOR IGNITION

Condition Possible Cause Corrective Action/Comments

-AM radio interference Ignitor operation

ACTION 1- Call Technical Support, Dallas

Page 47

Page 48

LENNOXOEMPARTS.COM

7 8

E- G26 -1 and -2 Models

1Ć When disconnect is closed, 120V is routed through

door interlock switch (S51) to feed the line voltage side of the blower control (A3) and transformer T1 priĆ mary. Door interlock switch must be closed for A3 and T1 to receive voltage.

2Ć T1 supplies 24VAC to terminal 24VAC" on A3. In turn,

terminal R" of A3 supplies 24VAC to terminal RC" of the indoor thermostat (not shown).

3Ć When there is a call for heat, W1 of the thermostat enĆ

ergizes W of the furnace control with 24VAC.

4Ć CAB of the blower control energizes the combustion

air blower (B6). When the combustion air blower nears full speed, combustion air prove switch (S18) closes.

Page 48

5Ć When S18 closes, assuming primary limit (S10) is

closed, the ignition control opens the pilot valve and begins spark.

6Ć When flame is sensed, spark stops and main valve

opens to light main burners.

7Ć After 45 seconds, blower control (A3) energizes the inĆ

door blower.

8Ć When heat demand is satisfied, W1 of the thermostat

deĆenergizes W of the furnace control and the furnace control immediately deĆenergizes the gas valve. The combustion air blower immediately stops. Also, the inĆ door blower runs for a designated period (90-330 secĆ onds) as set by jumper on blower control.

Page 49

LENNOXOEMPARTS.COM

F-BCC2 Blower Control -1 and -2 Models

BCC2

TROUBLESHOOTING

FLOWCHART

YES

STA RT

DOES UNIT OPERATE?

CHECK CIRCUIT

BREAKER. RESET IF

NECESSARY.

24VAC ACROSS

R & T?

YES

JUMPER ACROSS

SCREWS R & G

CHECK:

1-UNIT POWER

2-INTERLOCK SWITCH

3-TRANSFORMER

4-LIMIT SWITCH

REPLACE

BCC2

REPLACE

BCC2

120VAC ACROSS

N1 & CAB?

REPLACE

BCC2

120VAC ACROSS

N1 & ACC?

YES

JUMPER ACROSS

R &W

(REMOVE R & G JUMPER)

COMB. AIR BLOWER

ON?

YES

120VAC ACROSS

N1 & ACC?

YES

COMBUSTION

AIR BLOWER

YES

CHECK

YES

ARE BURNERS

RUNNING ON LOW

SPEED, 45 SEC.

AFTER FURNACE

BLOWER

RUNNING ON HIGH

SPEED?

LIT?

YES

IS BLOWER

LIGHTS?

120VAC ACROSS

N1 & A?

YES

CHECK BLOWER

WIRING AND

BLOWER

120VAC ACROSS

N1 & H?

REPLACE

1-COMBUSTION AIR BLOWER

2-IGNITION CONTROL

3-GAS VALVE

4-IGNITOR

5-LIMIT SWITCHES

6-PROVE SWITCH

CHECK BLOWER

CHECK:

YES

WIRING AND

BLOWER

BCC2

REMOVE

R & W

JUMPER

AFTER

END OF TEST

YES

THE SELECTED

TIME, DOES THE

BLOWER TURN

OFF?

REPLACE

FIGURE 55

Page 49

BCC2

24VAC ACROSS

T & V?

CHECK

WIRING

YES

REPLACE

BCC2

Page 50

LENNOXOEMPARTS.COM

G-G77 Ignition Control -1 and -2 Models

G776 IGNITION CONTROL TROUBLESHOOTING

Spark is present but pilot will not light



1993 Johnson Controls, Inc. Reprinted with permission.

STA RT

Are pilot valve

connections correct

and secure?

Is 24VAC

between terminals 1

and ground?

Is inlet

gas pressure per

manufacturer's specifications?

WARNING

Explosion Hazard. Do not use match to test for gas pressure.

YES

Securely connect at

terminal 1 and

ground.

Replace

Control.

Correct gas

pressure.

Correct or replace

pilot burner.

Check for clean orifice.

Is gas at pilot

burner?

YES

Is spark

gap 0.1 inch and

located in pilot

stream?

YES

Shield from drafts.

YES

END

FIGURE 56

Make sure pilot line

is not kinked or

obstructed. Check

for clean orifice.

If OK, replace

pilot valve.

Page 50

Page 51

LENNOXOEMPARTS.COM

G776 IGNITION CONTROL TROUBLESHOOTING

-1 and -2 MODELS

No spark and system will not work

1993 Johnson Controls, Inc. Reprinted with permission.

STA RT

Is 24VAC

between THS 2

and ground?

YES

Open thermostat contacts for

30 seconds. Close contacts

and wait 2 seconds longer

than prepurge (17 sec. total).

Is spark

present now?

Did pilot remain lit

from previous

cycle?

YES

Check the following:

1) 120VAC Supply

2) Transformer

3) Thermostat

System was is lockout. Determine the Cause:

Replace gas

valve.

1) Flameout cycling.

2) Internal malfunction.

3) Flame present when it should not be.

Turn OFF

supply voltage

Is high voltage

cable securely conĆ

nected to spark

transformer?

YES

Is high voltage

cable brittle, burnt

or cracked?

Is spark electrode ceramic cracked?

Is spark gap 0.1

inch and located in

pilot gas stream?

YES

Replace

control.

YES

Connect securely then

turn ON

supply voltage.

Replace cable.

Replace pilot

burner.

Correct or Replace piĆ

lot burner. Turn ON

supply voltage.

END

FIGURE 57

Page 51

Page 52

LENNOXOEMPARTS.COM

G776 IGNITION CONTROL TROUBLESHOOTING

-1 and -2 MODELS

Pilot lights but main valve will not come on

1993 Johnson Controls, Inc. Reprinted with permission.

Connect securely.

Replace

sensor.

STA RT

YES

Does spark

stay on for more than

5 seconds after pilot

lights?

YES

Make sure sensor cable

and high voltage cable

are separated and not

wrapped around any

pipe or accessories.

Is main

valve wiring securely

connected to terminals

4 and ground?

YES

Is sensor

ceramic cracked?

Is 24VAC

between terminals

3 and ground?

YES

Is inlet

gas pressure per

manufacturer's specĆ

ifications?

YES

Is main

valve wiring securely

connected to terminals

3 and ground?

YES

Replace main

valve.

Replace

control.

Correct

gas

pressure.

Correct

wiring.

Correct.

YES

Is sensor cable

grounded out?

Is sensor

or sensor connector

shorted to a metal

surface?

If system still fails, clean pilot

assembly, or replace flame

sensor, orifice, or control.

Does sensor cable

lack continuity

or good insulation?

Disconnect main valve lead from

terminal 3 and sensor cable from

terminal 4. Observing correct polarity,

connect DC microammeter between

terminal of sensor cable and terminal 4.

Is DC current

0.15 microamps or greater?

FIGURE 58

YES

Replace

control.

END

Replace

cable.

Page 52

Lennox G26Q2-50, G26Q4/5-75, G26Q3/4-100, G26Q4/5-100, G26Q3-50 Unit Information

Specifications and Main Features

Frequently Asked Questions

User Manual