Lennox G61MP User Manual
Corp. 0308−L6
Service Literature
Revised 10−2004
G61MP SERIES UNITS
G61MP series units are high−efficiency multi−position (upflow, downflow, horizontal right and left) gas furnaces
manufactured with Lennox Duralok Plust heat exchangers formed of aluminized steel. G61MP units are available
in heating capacities of 44,000 to 132,000 Btuh (13.0.0 to
38.6 kW) and cooling applications from 2 to 5 tons (7.0 kW
to 17.5 kW)) up to 5 tons. Refer to Engineering Handbook
for proper sizing.
Units are factory equipped for use with natural gas. Kits are
available for conversion to LPG operation. G61MP model
units are equipped with the Two−Stage Integrated SureLight
control. All G61MP units meet the California Nitrogen Oxides (NO
quirements. All units use a redundant gas valve to assure
safety shut−off as required by C.S.A.
) Standards and California Seasonal Efficiency re-
x
G61MP
All specifications in this manual are subject to change. Procedures outlined in this manual are presented as a recommendation only and do not supersede or replace local or
state codes. In the absence of local or state codes, the
guidelines and procedures outlined in this manual (except
where noted) are recommendations only and do not constitute code.
TABLE OF CONTENTS
Introduction 1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Specifications 2. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Blower Data 4. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Parts Identification 7. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
I Unit Components 8. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
II Installation 16. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
III Start Up 30. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
IV Heating System Service Checks 31. . . . . . . . . . . . . .
V Typical Operating Characteristics 34. . . . . . . . . . . . . .
IMPORTANT
Improper installation, adjustment, alteration, service
or maintenance can cause property damage, personal injury or loss of life. Installation and service must
be performed by a qualified installer, service agency
or the gas supplier.
WARNING
Electric shock hazard. Can cause injury
or death. Before attempting to perform
any service or maintenance, turn the
electrical power to unit OFF at disconnect switch(es). Unit may have multiple
power supplies.
VI Maintenance 35. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
VII Wiring and Sequence of Operation 38. . . . . . . . . . . .
VIII Field Wiring and Jumper Setting 46. . . . . . . . . . . . .
IX Control Board Troubleshooting 48. . . . . . . . . . . . . . . .
Page 1
WARNING
Sharp edges.
Be careful when servicing unit to avoid sharp edges
which may result in personal injury.
© 2003 Lennox Industries Inc.
SPECIFICATIONS
g
Blower
p
p
Gas
Heating
Performance
High
Fire
ModelNo. G61MP−36B−045 G61MP−36B−070 G61MP−48C−090 G61MP−60C−090
Input− Btuh (kW) 44,000 (12.9) 66,000 (19.3) 88,000 (25.8) 88,000 (25.8)
Output− Btuh (kW) 41,000 (12.0) 62,000 (18.2) 83,000 (24.3) 84,000 (24.6)
Temperature rise range − _F (_C) 25 − 55 (14 − 31) 35 − 65 (21 − 39) 35 − 65 (21 − 39) 25 − 55 (14 − 31)
Low
Fire
Input− Btuh (kW) 30,000 (8.8) 45,000 (13.2) 60,000 (17.6) 60,000 (17.6)
Output− Btuh (kW) 28,000 (8.2) 43,000 (12.6) 57,000 (16.7) 58,000 (17.0)
Temperature rise range − _F (_C) 10 − 40 (6 − 24) 20 − 50 (12 − 30) 25 − 55 (14 − 31) 15 − 45 (9 − 27)
1
AFUE 94.1% 94.1% 94.1% 94.1%
California Seasonal Efficiency 83.5% 86.0% 87.3% 84.4%
Highstatic(CSA)− in.w.g. (Pa) 0.5 0.5 0.5 0.5
2
Connections
in.
Intake Pipe (PVC) 2 2 2 2
2
Exhaust Pipe (PVC) 2 2 2 2
Condensate Drain Trap (PVC pipe) −
i.d.
with field supplied (PVC coupling) − o.d. 3/4 3/4 3/4 3/4
hose with hose clamp − i.d. x o.d. 1−1/4 x 1 1−1/4 x 1 1−1/4 x 1 1−1/4 x 1
GaspipesizeIPS 1/2 1/2 1/2 1/2
Indoor
Blower
Wheel nominal diameter x width −in.
(mm)
Motoroutput − hp (W) 1/3 (249) 1/3 (249) 1/2 (373) 1 (746)
Tons(kW) ofadd-oncooling 2.5 − 3 (8.8 − 10.5) 2.5 − 3.5 (8.8 − 12.3) 3 − 4 (10.5 − 14.0) 4 − 5 (14.0 − 17.5)
ShippingData lbs. (kg) − 1 package 136 (62) 146 (66) 168 (76) 176 (80)
Electricalcharacteristics 120 volts − 60 hertz − 1 phase (less than 12 amps)
OPTIONAL ACCESSORIES − MUST BE ORDERED EXTRA
3
Air Filter and Rack Kit
Size of filter
Condensate Drain Heat
Cable
Heat Cable Tape Fiberglass − 1/2 in. (38 mm) x 66 ft. (20 m)
Aluminum foil − 2 in. (25 mm) x 60 ft. (18
EZ Filter Base
Catalog Number − Ship. Weight − lbs.
Dimensions − H x W x D − in. (mm) 4 x 17−5/8 x 28−5/8
Size of field provided filter − in. (mm) 16 x 25 x 1
Down−Flow Additive Base 11M 60 11M 60 11M 61 11M 61
4
High Altitude Orifice Kit − Natural Gas 59M16 59M16 59M16 59M16
4
High Altitude Pressure Switch Kit − Order two each
7501−10,000ft. (2286−3048m
Horizontal Support Frame Kit − Ship. Weight − lbs. (kg) 56J18 − 18 (8) 56J18 − 18 (8) 56J18 − 18 (8) 56J18 − 18 (8)
LPG/Propane Kit
7501−10,000 ft. (2286−3048 m) 59M14 59M14 59M14 59M14
Natural to LPG/Propane Kit 59M87 59M87 59M87 59M87
RAB Return Air Base − − − − − − − − − RAB60C (12M71)
5
Termination Kits
Direct Vent
Concentric
Applications Only
Wall
Close Couple − 2 inch (51 mm) 22G44 22G44 − − − − − −
Close Couple WTK − 2 inch (51 mm) 30G28 30G28 − − − − − −
5,6
Termination Kits
Roof
Direct Vent or
Non−Direct Vent
NOTE − Filters and provisions for mounting are not furnished and must be field provided.
1
Annual Fuel Utilization Efficiency based on DOE test procedures and according to FTC labeling regulations. Isolated combustion system rating for non-weatherized furnaces.
2
Determine from venting tables proper exhaust pipe size and termination kit required.
3
Cleanable polyurethane frame type filter.
4
Required for proper operation at altitudes from 7501 to 10,000 ft. (2286 to 3048 m).
5
See Installation Instructions for specific venting information.
6
Kits contain enough parts for two, non−direct vent installations.
Wall Wall Ring Kit 2 inch (51 mm) 15F74 15F74 15F74 15F74
Horizontal (end) 87L96 − 18 x 25 x 1 in.
Side Return Single 44J22 or Ten Pack 66K63 − (1) 16 x 25 x 1 in. (406 x 635 x 25 mm)
6 ft. (1.8 m) 26K68 26K68 26K68 26K68
24 ft. (7.3 m) 26K69 26K69 26K69 26K69
50 ft. (15.2 m) 26K70 26K70 26K70 26K70
(kg)
0−7500 ft. (0−2286 m) 59M13 59M13 59M13 59M13
1−1/2 inch (38 mm) 60G77 60G77 − − − − − −
2 inch (51 mm) − − − − − − 33K97 33K97
3 inch (76 mm) − − − − − − 60L46 60L46
3 inch (76 mm) 44J40 44J40 44J40 44J40
2 inch (51 mm) 15F75 15F75 15F75 15F75
3 inch (76 mm) 44J41 44J41 44J41 44J41
1/2 1/2 1/2 1/2
10 x 8 (254 x 203) 10 x 8 (254 x 203) 10 x 10 (254 x 254) 11−1/2 x 10 (292 x 229)
(457 x 635 x 25 mm)
87L97 − 20 x 25 x 1 in.
(508 x 635 x 25 mm)
39G04 39G04 39G04 39G04
m)
39G03 39G03 39G03 39G03
73P56 − 7 (3) 73P56 − 7 (3) 73P57 − 8 (4) 73P57 − 8 (4)
(102 x 448 x 727)
(406 x 635 x 25)
4 x 17−5/8 x 28−5/8
(102 x 448 x 727)
16 x 25 x 1
(406 x 635 x 25)
4 x 21−5/8 x 28−5/8
(102 x 549 x 727)
20 x 25 x 1
(508 x 635 x 25)
4 x 21−5/8 x 28−5/8
(102 x 549 x 727)
20 x 25 x 1
(508 x 635 x 25)
− − − 56M06 − − − − − −
Page 2
SPECIFICATIONS
Perf
g
p
Applications
Direct Ven t
Gas
Heating
ormance
High Fire
Temperature rise range − _F (_C) 45 − 75 (25 − 42) 35 − 65 (21 − 39) 40 − 70 (24 − 42)
Low Fire
Temperature rise range − _F (_C) 30 − 60 (18 − 36) 25 − 55 (14 − 31) 30 − 60 (18 − 36)
California Seasonal Efficiency 88.4% 87.0% 87.7%
Highstatic(CSA)− in.w.g. (Pa) 0.5 0.5 0.5
Connections
in.
2
2
Exhaust Pipe (PVC) 2 2 3
Condensate Drain Trap (PVC pipe) − i.d. 1/2 1/2 1/2
with field supplied (PVC coupling) − o.d. 3/4 3/4 3/4
hose with hose clamp − i.d. x o.d. 1−1/4 x 1 1−1/4 x 1 1−1/4 x 1
Indoor
Blower
Wheelnominaldiameter xwidth −in. (mm) 10 x 10 (254 x 254) 11−1/2 x 10 (292 x 229) 11−1/2 x 10 (292 x 229)
Motoroutput − hp (W) 1/2 (373) 1 (746) 1 (746)
Tons(kW) ofadd-oncooling 3 − 4 (10.5 − 14.0) 4 − 5 (14.0 − 17.5) 4 − 5 (14.0 − 17.5)
ShippingData lbs. (kg) − 1 package 178 (81) 186 (84) 206 (93)
Electricalcharacteristics 120 volts − 60 hertz − 1 phase (less than 12 amps)
ModelNo. G61MP−48C−110 G61MP−60C−110 G61MP−60D−135
Input− Btuh (kW) 110,000 (32.2) 110,000 (32.2) 132,000 (38.7)
Output− Btuh (kW) 104,000 (30.5) 104,000 (30.5) 124,000 (36.3)
Input− Btuh (kW) 75,000 (22.0) 75,000 (22.0) 90,000 (26.4)
Output− Btuh (kW) 72,000 (21.1) 72,000 (21.1) 86,000 (25.2)
1
AFUE 94.1% 94.1% 94.1%
Intake Pipe (PVC) 2 2 3
GaspipesizeIPS 1/2 1/2 1/2
OPTIONAL ACCESSORIES − MUST BE ORDERED EXTRA
3, 4
Air Filter and Rack Kit −
Size of filter
Condensate Drain Heat
Cable
Heat Cable Tape
Fiberglass − 1/2 in. (38 mm) x 66 ft. (20 m)
Aluminum foil − 2 in. (25 mm) x 60 ft. (18 m)
4
EZ Filter Base
Catalog Number − Shipping Weight 73P57 − 8 lbs. (4 kg) 73P58 − 10 lbs. (5 kg) 73P58 − 10 lbs. (5 kg)
Dimensions − H x W x D − in. (mm) 4 x 21−5/8 x 28−5/8
Size of field provided filter − in. (mm) 20 x 25 x 1
Down−Flow Additive Base 11M 61 11M 61 11M 62
5
High Altitude Orifice Kit − Natural Gas Only 59M16 59M16 59M16
6
High Altitude Pressure Switch Kit − Order two each
4501−10,000 ft. (1372−3048 m)
Horizontal Support Frame Kit − Ship. Weight − lbs. (kg) 56J18 − 18 (8) 56J18 − 18 (8) 56J18 − 18 (8)
LPG/Propane Kit 0−7500 ft. (0−2286 m) 59M13 59M13 59M13
7501−10,000ft. (2286−3048m) 59M14 59M14 59M14
Natural to LPG/Propane Kit 59M87 59M87 59M87
RAB Return Air Base − − − − RAB60C (12M71) RAB60D (12M72)
7
Termination Kits −
Direct Vent
Concentric
Roof/Wall
Wall Close−Coupled 3 inch (76 mm) 44J40 44J40 44J40
7,8
Termination Kits
Roof
Direct Vent or Non−
Wall Ring Kit 2 inch (51 mm) 15F74 15F74
NOTE − Filters and provisions for mounting are not furnished and must be field provided.
1
Annual Fuel Utilization Efficiency based on DOE test procedures and according to FTC labeling regulations. Isolated combustion system rating for non-weatherized furnaces.
2
Determine from venting tables proper exhaust pipe size and termination kit required.
3
Cleanable polyurethane frame type filter.
4
Not for use with RAB Return Air Base or with 60C and 60D size units with air flow requirements of 1800 cfm (850 L/s) or greater. See Blower Performance tables for additional
information.
5
Required for proper operation at altitudes from 7501 to 10,000 ft. (2286 to 3048 m).
6
Required for proper operation at altitudes over 4500 ft. (1370 m).
7
See Installation Instructions for specific venting information.
8
Kits contain enough parts for two, non−direct vent installations.
9
Non−direct vent applications only.
Horizontal (end) 87L97 − 20 x 25 x 1 in. (508 x 635 x 25 mm) 87L98 − 25 x 25 x 1 in.
(635 x 635 x 25 mm)
5
Side Return
Single 44J22 or Ten Pack (66K63) − (1) 16 x 25 x 1 in. (406 x 635 x 25 mm)
6 ft. (1.8 m) 26K68 26K68 26K68
24 ft. (7.3 m) 26K69 26K69 26K69
50 ft. (15.2 m) 26K70 26K70 26K70
39G04 39G04 39G04
39G03 39G03 39G03
(102 x 549 x 727)
(508 x 635 x 25)
4 x 24−5/8 x 28−5/8
(102 x 625 x 727)
24 x 24 x 1
(610 x 610 x 25)
4 x 24−5/8 x 28−5/8
(102 x 625 x 727)
24 x 24 x 1
(610 x 610 x 25)
− − − − − − 56M93
2 inch (51 mm) 33K97 33K97 − − −
3 inch (76 mm) 60L46 60L46 60L46
2 inch (51 mm) 15F75 15F75 − − −
3 inch (76 mm) 44J41 44J41 44J41
9
15F74
Page 3
BLOWER DATA
External Static
External Static
External Static
External Static
G61MP−36B−045 PERFORMANCE (Less Filter)
External Static
Pressure
in. w.g. Pa cfm L/s Watts cfm L/s Watts cfm L/s Watts cfm L/s Watts
0.00
0.10 25 1515 715 605 1385 655 555 1190 560 485 1020 480 415
0.20 50 1470 695 580 1345 635 520 1170 550 455 1010 475 400
0.30 75 1410 665 555 1310 620 495 1155 545 440 1000 470 385
0.40 100 1350 640 535 1250 590 465 1120 530 410 980 465 360
0.50 125 1290 610 505 1205 570 450 1080 510 390 950 450 345
0.60 150 1220 575 485 1145 540 420 1020 480 365 905 430 320
0.70 175 1145 540 460 1080 510 400 975 460 345 860 405 300
0.80 200 1050 495 425 985 465 365 870 410 320 785 370 285
0.90 225 945 445 410 900 425 345 825 390 305 730 345 270
NOTES − All air data is measured external to unit without filter (not furnished − field provided).
25 1555 735 630 1410 665 585 1190 560 520 1030 485 435
Air volume based on bottom air return air. Actual air volume may vary on side return air applications.
High Medium−High Medium−Low Low
G61MP−36B−070 PERFORMANCE (Less Filter)
External Static
Pressure
in. w.g. Pa cfm L/s Watts cfm L/s Watts cfm L/s Watts cfm L/s Watts
0.00 0 1640 775 660 1415 665 575 1160 545 485 1005 475 410
0.10 25 1600 755 635 1395 660 550 1160 545 460 1000 470 385
0.20 50 1540 725 605 1370 650 525 1160 545 445 995 470 375
0.30 75 1495 705 580 1345 635 505 1145 540 425 990 465 365
0.40 100 1420 670 545 1275 605 480 1125 530 395 965 455 345
0.50 125 1360 640 525 1245 590 450 1080 510 375 945 445 325
0.60 150 1275 600 490 1165 550 410 1025 485 350 900 425 305
0.70 175 1170 555 465 1085 515 385 965 430 335 860 405 295
0.80 200 1080 510 440 1010 475 360 865 410 310 775 365 270
0.90 225 945 445 400 840 395 320 765 360 275 710 335 245
NOTES − All air data is measured external to unit without filter (not furnished − field provided).
Air volume based on bottom air return air. Actual air volume may vary on side return air applications.
High Medium−High Medium−Low Low
G61MP−48C−090 PERFORMANCE (Less Filter)
External Static
Pressure
in. w.g. Pa cfm L/s Watts cfm L/s Watts cfm L/s Watts cfm L/s Watts
0.00 0 2180 1030 930 1835 865 790 1520 715 630 1280 605 510
0.10 25 2135 1005 885 1825 860 750 1510 710 610 1275 600 495
0.20 50 2085 985 840 1810 855 720 1505 710 580 1270 600 475
0.30 75 2030 955 800 1775 835 685 1500 705 565 1265 595 460
0.40 100 1940 915 760 1735 820 650 1480 700 535 1250 590 440
0.50 125 1865 880 725 1660 785 600 1430 675 505 1215 575 425
0.60 150 1740 820 670 1590 750 575 1380 650 475 1175 555 410
0.70 175 1645 775 640 1475 695 520 1290 610 450 1105 520 375
0.80 200 1540 725 600 1340 630 465 1175 555 405 1020 480 355
0.90 225 1335 630 540 1170 555 440 1070 505 375 950 450 330
NOTES − All air data is measured external to unit without filter (not furnished − field provided).
Air volume based on bottom air return air. Actual air volume may vary on side return air applications.
High Medium−High Medium−Low Low
G61MP−48C−110 PERFORMANCE (Less Filter)
External Static
Pressure
in. w.g. Pa cfm L/s Watts cfm L/s Watts cfm L/s Watts cfm L/s Watts
0.00 0 2160 1020 880 1880 890 755 1490 705 602 1235 580 485
0.10 25 2100 990 850 1855 875 730 1480 700 585 1230 580 475
0.20 50 2035 960 805 1815 860 690 1475 695 560 1225 580 460
0.30 75 1965 925 750 1755 830 650 1475 695 545 1220 575 445
0.40 100 1885 890 725 1715 810 625 1465 690 510 1215 575 430
0.50 125 1780 840 680 1630 770 580 1420 670 490 1150 540 400
0.60 150 1690 800 660 1550 735 550 1360 640 460 111 0 525 380
0.70 175 1575 745 620 1410 665 505 1210 570 405 1035 490 350
0.80 200 1375 650 550 1230 580 450 1125 530 380 970 460 325
0.90 225 1225 580 520 1120 530 415 1050 495 365 885 420 310
NOTES − All air data is measured external to unit without filter (not furnished − field provided).
Air volume based on bottom air return air. Actual air volume may vary on side return air applications.
High Medium−High Medium−Low Low
Air Volume / Watts at Different Blower Speeds
Air Volume / Watts at Different Blower Speeds
Air Volume / Watts at Different Blower Speeds
Air Volume / Watts at Different Blower Speeds
Page 4
BLOWER DATA
External Static
External Static
G61MP−60C−090 PERFORMANCE (Less Filter) − Single Side Return Air − Air volumes in bold require field fabricated transition to accommodate 20 x 25 x 1 in. (508 x 635 x 25 mm) air filter in order to maintain proper air velocity.
External Static
Pressure
in. w.g. Pa cfm L/s Watts cfm L/s Watts cfm L/s Watts cfm L/s Watts
0.00 0 2835 1335 1495 2340 1105 1155 1800 850 895 1440 680 695
0.10 25 2785 1315 1475 2345 1105 1135 1805 855 865 1515 715 690
0.20 50 2715
0.30
0.40 100 2550 1205 1350 2230 1055 1015 1845 870 815 1620 765 670
0.50 125 2450 1155 1305 2175 1025 990 1850 870 790 1615 765 655
0.60 150 2365 1115 1270 2130 1005 940 1830 865 775 1615 760 640
0.70 175 2240 1060 1205 2070 975 915 1815 855 760 1595 755 620
0.80 200 2185 1030 1190 1965 925 865 1775 840 745 1555 735 605
0.90 225 2015 950 1150 1820 860 820 1690 800 715 1440 680 580
NOTES − All air data is measured external to unit without filter (not furnished − field provided).
75 2620 1235 1380 2260 1065 1035 1840 870 825 1600 755 680
High Medium−High Medium−Low Low
1280 1435 2275 1075 1080 1825 860 845 1560 735 685
G61MP−60C−090 PERFORMANCE (Less Filter) − Bottom Return Air, Side Return Air with Optional RAB Return Air Base,
Return Air from Both Sides or Return Air from Bottom and One Side.
External Static
Pressure
in. w.g. Pa cfm L/s Watts cfm L/s Watts cfm L/s Watts cfm L/s Watts
0.00 0 2840 1340 1450 2345 1105 1105 1895 895 900 1515 715 700
0.10 25 2765 1305 1415 2365 1115 1080 1950 920 885 1580 745 700
0.20 50 2695 1270 1385 2345 1105 1050 1985 935 870 1620 765 695
0.30 75 2605 1230 1335 2315 1090 1030 1990 940 850 1645 775 690
0.40 100 2530 1195 1300 2265 1070 990 1990 940 825 1665 785 675
0.50 125 2420 1140 1260 2210 1045 955 1970 930 800 1675 790 665
0.60 150 2330 1100 1220 2145 1010 925 1930 910 775 1665 785 650
0.70 175 2250 1060 1190 2050 965 885 1875 885 745 1645 775 630
0.80 200 2135 1010 1140 2000 945 865 1810 855 715 1620 765 615
0.90 225 2030 960 1090 1885 890 830 1720 810 685 1560 735 590
NOTES − All air data is measured external to unit without filter (not furnished − field provided).
High Medium−High Medium−Low Low
Air Volume / Watts at Different Blower Speeds
Air Volume / Watts at Different Blower Speeds
G61MP−60C−110 PERFORMANCE (Less Filter) − Single Side Return Air − Air volumes in bold require field fabricated transition to accommodate 20 x 25 x 1 in. (508 x 635 x 25 mm) air filter in order to maintain proper air velocity.
External Static
Pressure
in. w.g. Pa cfm L/s Watts cfm L/s Watts cfm L/s Watts cfm L/s Watts
0.00 0 2625 1240 1350 2310 1090 1080 1885 890 885 1515 715 700
0.10 25 2570 1215 1330 2325 1095 1060 1910 900 865 1575 745 700
0.20 50 2410 1135 1305 2285 1080 1035 1930 910 845 1620 765 690
0.30 75 2425 1145 1265 2230 1055 990 1925 905 825 1635 770 675
0.40 100 2335 1100 1220 2175 1025 950 1910 900 810 1640 775 660
0.50 125 2270 1070 1195 2120 1000 935 1895 895 785 1640 775 640
0.60 150 2170 1025 1155 2045 965 885 1860 875 765 1630 770 630
0.70 175 2110 995 1130 1950 920 855 1795 845 730 1590 750 610
0.80 200 2035 960 1090 1885 890 820 1745 825 705 1540 725 580
0.90 225 1900 895 1055 1760 830 780 1665 785 680 1470 695 565
NOTES − All air data is measured external to unit without filter (not furnished − field provided).
High Medium−High Medium−Low Low
Air Volume / Watts at Different Blower Speeds
Page 5
BLOWER DATA
G61MP−60C−110 PERFORMANCE (Less Filter) − Bottom Return Air, Side Return Air with Optional RAB Return Air Base,
Return Air from Both Sides or Return Air from Bottom and One Side.
External Static
Pressure
in. w.g. Pa cfm L/s Watts cfm L/s Watts cfm L/s Watts cfm L/s Watts
0.00 0 2720 1285 1385 2410 1135 1090 2055 970 935 1620 765 710
0.10 25 2665 1255 1355 2385 1125 1075 2025 955 885 1730 815 735
0.20 50 2585 1220 1315 2350 1110 1015 2030 955 865 1680 795 690
0.30 75 2505 1180 1275 2290 1080 990 2025 955 840 1695 800 675
0.40 100 2435 1150 1250 2235 1055 940 2030 960 830 1695 800 660
0.50 125 2350 1110 1205 2170 1025 930 1975 930 790 1735 820 665
0.60 150 2255 1065 1185 2100 990 895 1915 905 765 1720 810 650
0.70 175 2160 1020 1150 2005 945 840 1865 880 730 1680 795 635
0.80 200 2020 955 1090 1905 900 825 1810 855 710 1625 765 610
0.90 225 1910 900 1050 1820 860 795 1705 805 675 1540 725 590
NOTES − All air data is measured external to unit without filter (not furnished − field provided).
High Medium−High Medium−Low Low
G61MP−60D−135 PERFORMANCE (Less Filter) − Single Side Return Air − Air volumes in bold require field fabricated transition to accommodate 20 x 25 x 1 in. (508 x 635 x 25 mm) air filter in order to maintain proper air velocity.
External Static
Pressure
in. w.g. Pa cfm L/s Watts cfm L/s Watts cfm L/s Watts cfm L/s Watts
0.00 0 2665 1260 1440 2325 1095 1100 1865 880 890 1410 665 690
0.10 25 2615 1235 1405 2310 1090 1065 1915 905 865 1465 690 685
0.20 50 2530 1195 1370 2280 1075 1055 1925 910 850 1570 740 675
0.30 75 2470 1165 1330 2235 1055 1015 1920 905 825 1590 750 670
0.40 100 2380 1125 1290 2175 1025 985 1910 900 805 1590 750 655
0.50 125 2310 1090 1265 2120 1000 965 1890 890 790 1595 755 645
0.60 150 2200 1035 1230 2055 970 935 1835 865 765 1580 745 630
0.70 175 2120 1000 1190 1970 930 900 1790 845 740 1545 730 605
0.80 200 2025 955 1160 1890 890 875 1720 810 710 1515 715 590
0.90 225 1930 910 1110 1800 850 835 1655 780 685 1440 680 570
NOTES − All air data is measured external to unit without filter (not furnished − field provided).
High Medium−High Medium−Low Low
Air Volume / Watts at Different Blower Speeds
Air Volume / Watts at Different Blower Speeds
G61MP−60D−135 PERFORMANCE (Less Filter) − Bottom Return Air, Side Return Air with Optional RAB Return Air Base,
Return Air from Both Sides or Return Air from Bottom and One Side.
External Static
Pressure
in. w.g. Pa cfm L/s Watts cfm L/s Watts cfm L/s Watts cfm L/s Watts
0.00 0 2730 1290 1465 2425 1145 1125 2055 970 915 1560 735 680
0.10 25 2670 1260 1440 2400 1135 1100 2065 975 890 1590 750 675
0.20 50 2600 1225 1400 2365 1115 1070 2045 965 865 1620 765 665
0.30 75 2525 1190 1360 2315 1095 1045 2035 960 845 1615 760 655
0.40 100 2445 1155 1325 2260 1065 1015 2020 955 820 1615 760 645
0.50 125 2360 1115 1280 2195 1035 985 1960 925 790 1610 760 635
0.60 150 2290 1080 1255 2130 1005 965 1900 895 755 1600 755 615
0.70 175 2205 1040 1220 2035 960 910 1825 860 730 1570 740 600
0.80 200 2110 995 1195 1945 915 880 1765 830 710 1540 725 580
0.90 225 1970 930 1120 1835 865 830 1680 795 690 1540 725 545
NOTES − All air data is measured external to unit without filter (not furnished − field provided).
High Medium−High Medium−Low Low
Air Volume / Watts at Different Blower Speeds
Page 6
G61MP PARTS ARRANGEMENT
TOP CAP
BURNER BOX
ASSEMBLY
GAS VALVE
AND MANIFOLD
FLUE
COLLAR
COMBUSTION
AIR PROVE PROVE
SWITCHES*
COMBUSTION AIR
INDUCER
DuralokPlus
HEAT EXCHANGER
ASSEMBLY
TM
CABINET
WARM HEADER
(COLLECTOR)
BOX
CONDENSER COIL
BURNER
ACCESS
PANEL
BLOWER
ACCESS
DOOR
*G61MP−090 shown.
G61MP−045 and −070
are equipped with
two switches.
SIGHT
GLASS
DOOR
INTERLOCK
SWITCH
PRIMARY LIMIT
COLD HEADER
(COLLECTOR)
BOX
SECONDARY
LIMITS (2)
BLOWER
ASSEMBLY
CONTROL BOX
FIGURE 1
Page 7
I−UNIT COMPONENTS
G61MP unit components are shown in figure 1. The gas
valve, combustion air inducer and burners can be accessed by removing the burner access panel. Electrical
components are in the control box (figure 2) found in the
blower section.
G61MP units are factory equipped with a bottom return air
panel in place. The panel is designed to be field removed as
required for bottom air return. Markings are provided for side
return air and may be cut out in the field.
ELECTROSTATIC DISCHARGE (ESD)
Precautions and Procedures
3. 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 shutdown. The breaker can be manually reset
by pressing the button on the face. See figure 3.
CIRCUIT BREAKER CB8
PRESS TO RESET
CAUTION
Electrostatic discharge can affect electronic
components. Take precautions during furnace
installation and service to protect the furnace’s
electronic controls. Precautions will help to
avoid control exposure to electrostatic discharge by putting the furnace, the control and
the technician at the same electrostatic potential. Neutralize electrostatic charge by touching
hand and all tools on an unpainted unit surface,
such as the gas valve or blower deck, before performing any service procedure.
A−Control Box
1. Control Transformer (T1)
A transformer located in the control box provides power to
the low voltage section of the unit. Transformers on all
models are rated 40VA with a 120V primary and a 24V secondary.
2. Door Interlock Switch (S51)
A door interlock switch rated 14A at 125VAC is wired in series with line voltage. When the blower door is removed the
unit will shut down.
CONTROL BOX G61MP
CIRCUIT
BREAKER
DOOR INTERLOCK
SWITCH
SURELIGHT
CONTROL
BOARD
FIGURE 2
TRANSFORMER
FIGURE 3
WARNING
Shock hazard.
Disconnect power before servicing. Integrated
Control Board 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.
4. Integrated Control Board (A92)
All G61MP units are equipped with the Lennox Two−Stage
Integrated control board. The system consists of a ignition control board (figure 4 with control terminal designations in tables 3, 4 and 5) and ignitor (figure 7). The board
and ignitor work in combination to ensure furnace ignition
and ignitor durability. The board controls all major furnace
operations. The board features two LED lights, DS1 and
DS2 for troubleshooting. The board also has two accessory terminals rated at (1) one amp. See table 6 for troubleshooting diagnostic codes.
Electronic Ignition
At the beginning of the heat cycle, SureLight control monitors the first stage and second stage combustion air inducer prove switch. The control will not begin the heating cycle
if the first stage prove switch is closed (by−passed). Likewise the control will not begin the second stage heating
cycle if the second stage prove switch is closed, and will allow first stage heat only. However if the second stage prove
switch closes during the first stage pre−purge, the control
will respond to second stage heat. Once the first stage
prove switch is determined to be open, the combustion air
inducer is energized on low (first stage) heat speed. When
the differential in the prove switch is great enough, the
prove switch closes and a 15−second pre−purge begins. If
the switch is not proven within 2−1/2 minutes, the control
goes into Watchguard−Pressure Switch mode for a 5−minute re−set period.
After the 15−second pre−purge period, the SureLight ignitor
warms up for 20 seconds after which the gas valve opens
for a 4−second trial for ignition. The ignitor energizes during
the trial until flame is sensed. If ignition is not proved during
the 4−second period, the control will try four more times with
an inter purge and warm−up time between trials of 35 sec-
Page 8
onds. 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 ignitor
on successive calls for heat. The control continues to ramp
down the voltage to the ignitor until it finds the lowest
amount of power that will provide a successful ignition. This
amount of power is used for 255 cycles. On the 256th call
for heat, the control will again ramp down until the lowest
power is determined and the cycle begins again.
Two Stage Operation / Thermostat Selection Jumper
The control can be utilized in two modes: SINGLE−STAGE
thermostat or TWO−STAGE thermostat. The thermostat
selection jumper E20, located just below dip switches 1
through 4 (figure 4), must be positioned for the particular
application. The jumper is factory set on TWO" for use
with a two−stage thermostat with two stage heat. Re−position jumper to SINGLE" for use with a single stage thermostat with two stage heat.
While in the single−stage thermostat mode (single jumper
setting), the burners will always fire on first−stage heat. The
combustion air inducer will operate on low speed and indoor blower will operate on low heat speed. After a 10 minute recognition period, the unit will switch to second stage
heat. While in the two−stage thermostat mode (two jumper
setting) the burners will fire on first−stage heat. The combustion air inducer will operate on low speed and indoor
blower will operate on low heat speed. The unit will switch
to second−stage heat on call from the indoor thermostat. If
there is a simultaneous call for first and second stage heat,
the unit will fire on first stage heat and switch to second
stage heat after 30 seconds of operation. See Sequence of
Operation flow charts in the back of this manual for more
detail.
Dip Switch Settings
Dip Switches 1 and 2 − Heating Fan off Delay − 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 1 and 2
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. For customized comfort, monitor the supply
air temperature once the heat demand is satisfied. Note the
supply air temperature at the instant the blower is de−energized. Adjust the fan−off delay to achieve a supply air temperature between 90° − 110° at the instant the blower is de−
energized. (Longer delay times allow for lower air temperature, shorter delay times allow for higher air temperature).
See table 1 for dip switch settings.
TABLE 1
Heating Fan Off Delay
Delay (Seconds)
60 Off Off
90 Off On
120 On Off
180 On On
Switch 3 − Second Stage Delay (Used with Single−Stage
Thermostat Only) −− This switch is used to determine the
second stage on delay when a single−stage thermostat is
being used. The switch is factory−set in the ON position,
which provides a 10−minute delay before second−stage
heat is initiated. If the switch is toggled to the OFF position,
it will provide a 15−minute delay before second−stage heat
is initiated. This switch is only activated when the thermo-
stat selector jumper is positioned for SINGLE−stage ther-
mostat use.
Switch 4 − Cooling Fan off Delay − The fan on delay time
of 2 seconds is not adjustable. Fan off time (time that the
blower operates after the cool demand has been satisfied)
can be adjusted by flipping dip switch 4. The unit is shipped
with a factory fan off setting of 45 seconds. Fan off time will
affect comfort and is adjustable to satisfy individual ap-
plications. See table 2 for cool fan off time settings.
Cooling Fan Off Delay
Delay (Seconds) Switch 4
2 Off
45 On
Diagnostic LED’s (DS1 and DS2)
Two diagnostic LED’S are located on the two−stage inte-
grated control board. See figure 4. These light flashes cor-
respond with the codes detailed in table 6.
Factory Installed Jumper Y1 to Y2
A factory−installed jumper from Y1 to Y2 terminals on the
integrated control board terminal strip must be clipped for
two−stage cooling.
Switch 1 Switch 2
TABLE 2
Page 9
TWO−STAGE INTEGRATED CONTROL BOARD
LEDs
DIP
SWITCHES
1 − 4
W915 FACTORY INSTALLED JUMPER
(MUST CLIP FOR 2 STAGE COOL)
THERMOSTAT CONNECTIONS (TB1)
TABLE 3
Integrated Control Board Terminals
120VAC Neutral
LINE Line
XFMR Transformer
EAC Electronic Air Cleaner
CIRC Indoor Blower
HUM Humidifier
120VAC Line
HUM Humidifier
XMFR Transformer
LINE Line
PARK For Unused Leads
COOL Cooling Speed
EAC Electronic Air Cleaner
HI HEAT HIigh Heat Speed
LO HEAT Low Heat, Low Cool and Continuous Fan
Speed
TABLE 4
Integrated Control Board 5 Pin Terminal
PIN # Function
1 Ignitor
2 Combustion Air Inducer High Speed
3 Combustion Air Inducer Low Speed
4 Combustion Air Inducer Neutral
5 Ignitor Neutral
DIP SWITCH(ES) FUNCTION
1 and 2 Blower Off Delay (Heating Mode)
3 Second Stage ON Delay (Single−stage t’stat)
4 Blower Off Delay (Cooling Mode)
FIGURE 4
TABLE 5
Integrated Control Board 12Pin Terminal
PIN # Function
1 Gas Valve 2nd Stage (High Fire)
2 Second Stage Prove Switch
3 Not Used
4 Ground
5 24V Hot
6 Primary Limit In
7 Gas Valve 1st stage (Low Fire)
8 Gas Valve Common
9 24V Neutral
10 Ground
11 Primary Limit Out
12 1st Stage Prove Switch
Page 10
TABLE 6
ONONON
Circuit board failure or control wired incorrectly. Check 24 and 115 volts to board.
DIAGNOSTIC CODES
Diagnostic LEDs are labeled DS1 and DS2. See figure 4 for location of diagnostic LEDs.
DS1 DS2 DESCRIPTION
SIMULTANEOUS
SLOW FLASH
SIMULTANEOUS
FAST FLASH
SLOW FLASH ON
OFF SLOW FLASH
OFF FAST FLASH
ALTERNATING
SLOW FLASH
SLOW FLASH OFF Flame sensed without gas valve energized.
ON ON
OFF ON
FAST FLASH SLOW FLASH Main power polarity reversed. Switch line and neutral.
SLOW FLASH FAST FLASH Low flame signal. Measures below 0.23 microAmps. Replace flame sense rod.
ALTERNATING
FAST FLASH
SIMULTANEOUS
SLOW FLASH
SIMULTANEOUS
FAST FLASH
ALTERNATING
SLOW FLASH
OFF
ALTERNATING
FAST FLASH
Power on − Normal operation.
Also signaled during cooling and continuous fan.
Normal operation − signaled when heating demand initiated at thermostat.
Primary, secondary, backup secondary or rollout limit switch open. Limits must
close within 3 minutes or unit goes into 1 hour Watchguard.
Low prove switch open;
OR: Blocked inlet/exhaust vent;
OR: Low prove switch closed prior to activation of combustion air inducer.
High prove switch open;
OR: Blocked inlet/exhaust vent;
OR: High prove switch closed prior to activation of combustion air inducer.
Watchguard −− burners failed to ignite; OR limit open more than 3 minutes;
OR lost flame sense 5 times in one heating cycle;
OR pressure switch opened 5 times in one heating cycle.
Circuit board failure or control wired incorrectly. Check 24 and 115 volts to board.
The following conditions are sensed during the ignitor warm−up period only:
1) Improper main ground;
2) Broken ignitor; OR: Open ignitor circuit;
3) Line voltage below 75 volts.
(If voltage lower than 75 volts prior to ignitor warm-up, control will signal waiting on
call from thermostat, and will not respond.
NOTE − Slow flash rate equals 1 Hz (one flash per second). Fast flash rate equals 3 Hz (three flashes per second).
Low flame sense current = 0.17−0.22 microAmps.
B−Blower Compartment
1. Blower Motor (B3) and Capacitor (C4)
SUPPLY AIR BLOWER
AND SECONDARY LIMITS
All G61MP units use direct drive blower motors. All motors
are 120V permanent split capacitor motors to ensure maximum efficiency. Ratings for capacitors will be on motor
nameplate. See SPECIFICATIONS section for motor specifications.
NOTE − Shafts on 1 HP motors have 2 flat sides and are
matched with blower wheels with 2 set screws.
2. Secondary Limit Controls (S21)
The secondary limits (S21) on G61MP units are located in the
blower compartment on the back side of the blower housing.
See figure 5. All G61MP units are equipped with two secondary limts. When excess heat is sensed in the blower compartment, the limit will open. If the limit is open, the furnace control
CAPACITOR
To Remove Blower From Unit: Disconnect Power, Remove Control
Box, Remove Bolts and Unplug Motor Wires From Control Board.
Then Slide Out Front of Unit.
FIGURE 5
SECONDARY
LIMIT (S)
MOTOR/BLOWER
ASSEMBLY
energizes the supply air blower and closes the gas valve. The
limit automatically resets when unit temperature returns to normal. The switch is factory set to open at 125°F and cannot be
adjusted.
Page 11
C−Heating Components
3. Flame Sensor
A flame sensor is located on the left side of the burner support. See figure 6. The sensor is mounted through the bottom of the burner box and the tip protrudes into the flame
envelope of the left−most burner. The sensor can be removed for service without removing any part of the burners. During operation, flame is sensed by current passed
through the flame and sensing electrode. The SureLight
control allows the gas valve to remain open as long as
flame signal is sensed.
NORMAL FLAME SIGNAL > 0.23 MICROAMPS
LOW FLAME SIGNAL < 0.22 MICROAMPS
DROP OUT SIGNAL = 0.16 MICROAMPS
5/16"
FIGURE 6
4. Ignitor
The SureLight ignitor is made of durable silicon nitride. Ignitor longevity is enhanced by controlling voltage to the ignitor. The board finds the lowest ignitor temperature which
will successfully light the burner, thus increasing the life of
the ignitor. Due to this feature of the board, voltage cannot
be measured so ignitor must be ohmed. Ohme value
should be 10.9 to 19.7. See 7 for ignitor location.
NOTE − The G61MP furnace contains electronic components that are polarity sensitive. Make sure that the
furnace is wired correctly and is properly grounded.
5. Burners (Figure 7)
All units use inshot burners. Burners are factory set and do not
require adjustment. The manifold brackets are slotted so 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 and is threaded into the
burner manifold. All G61MP natural gas units are fitted with
.089" sized orifices. See SPECIFICATIONS" tables for LP
kits and high altitude.
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 is fitted with a corbel cup (orifice) used to direct the flow
of combustion products.
13/32’
IGNITOR
MEASUREMENT IS TO I.D.
5/8"
OF RETENTION RING
SureLight Ignitor Location
5/16"
BRACKET
BURNERS TOP VIEWBURNERS FRONT VIEW
FIGURE 7
Page 12
6. Clamshell Heat Exchanger
G61MP units use an aluminized steel primary and stainless steel secondary heat exchanger assembly. Heat is
transferred to the air stream from all surfaces of the heat
exchanger. The shape of the heat exchanger ensures
maximum efficiency.
The combustion air inducer pulls fresh air through the air
intake box. This air is mixed with gas in the burner venturi
and at the corbel orifices. The gas / air mixture is then
burned at the entrance of each clamshell. Combustion
gases are then pulled through the primary and secondary heat
exchangers and exhausted out the exhaust vent pipe.
7. Flame Rollout Switches (S47)
Flame rollout switch S47 is a high temperature limit located
on each side of the burner box. Each furnace is equipped
with two identical switches. The limit is a N.C. SPST manual-reset limit connected in series with the primary limit S10.
When S47 senses rollout, the circuit breaks and the ignition
control immediately stops ignition and closes the gas
valve.
If unit is running and flame rollout is detected, the gas valve
will close and ignition control will be disabled. Rollout can
be caused by a blocked heat exchanger, flue or lack of
combustion air. The switch is factory set to trip (open) at
250°F and cannot be adjusted. The switch can be manually
reset. To manually reset a tripped switch, push the reset button located on the control.
8. Primary Limit Control (S10)
Figure 8 shows the primary limit (S10) used on G61MP units
located in the heating vestibule panel. S10 is provided with a
shield on some models (figure 8) and must not be removed.
Note orientation of shield and limit if limit is replaced. When excess heat is sensed in the heat exchanger, the limit will open.
Once the limit opens, the furnace control energizes the
supply air blower and de−energizes the gas valve. The limit
automatically resets when unit temperature returns to normal. The switch is factory set and cannot be adjusted.
9. Backup Secondary Limit Control (S113)
(G61MP−090, 110, 135 only)
Backup secondary limit control S113 is a N.C. auto−reset
switch located on the combustion air inducer. S113 acts as
a backup to primary limit S10 in the event of an indoor blower failure. S113 contacts open when temperature on the
CAI reaches 142°.
10. Gas Valve (GV1)
The G61MP uses a two−stage gas valve manufactured by
Honeywell (figure 35) or White Rodgers (figure 36). The
valves are internally redundant to assure safety shut−off. If
the gas valve must be replaced, the same type valve must
be used.
24VAC terminals and gas control knob or switch are located
on the valve. All terminals on the gas valve are connected to
wires from the electronic ignition control. 24V applied to the terminals energizes the valve.
Inlet and outlet pressure taps are located on the valve. A regulator adjustment screw is located on the valve.
LPG change over kit s are available from Lennox. Kits include
burner orifices and a gas valve regulator conversion kit.
The burner box is sealed and operates under a negative
pressure. A pressure hose is connected from the burner
box to the gas valve. The gas valve senses the pressure in
the burner box and changes gas valve outlet (manifold)
pressure based on changes in the burner box pressure.
The intent is to compensate for different vent configurations which can greatly affect the rate of the unit.
PRIMARY LIMIT LOCATION
limit shield
090, −110 and
−135 only
limit faces shield
FIGURE 8
11. Combustion Air Inducer
Prove Switch (S18)
All G61MP units are equipped with combustion air prove
switches located on the combustion air inducer housing.
G61MP−045 and −070 (figure 10) units have two combustion
air proving switches. G61MP−090, −110 and −135 units are
equipped with two dual prove switch assemblies" consisting of two switches acting as one. See figure 9. The switches
are connected to the cold end header box by means of a
flexible hose that monitors negative air pressure in the cold
end header box.
The switches are a single-pole single-throw proving switch
electrically connected to the furnace control. The purpose of
the switch is to prevent burner operation if the combustion
air inducer is not operating or if the flue becomes obstructed.
Page 13
On heat demand (first or second stage) the switch senses
that the combustion air inducer is operating. It closes a circuit to the furnace control when pressure inside the cold
end header box decreases to a certain set point.
Set points vary depending on unit size. See tables 8, 9 and
10. The pressure sensed by the switch is negative. If the air
intake vent pipe or outlet vent pipe becomes obstructed
during operation, the switch senses a change of negative
pressure and opens the circuit to the furnace control and
gas valve. A bleed port on the switch allows relatively dry
air in the vestibule to purge switch tubing, to prevent condensate build up.
The switch is factory set and is not field adjustable. It is a
safety shut-down control in the furnace and must not be by−
passed for any reason. If switch is closed or by−passed, the
control will not initiate ignition at start up.
1 − Remove thermostat demand and allow unit to cycle
off.
2 − Install a tee in the negative (−) line and a tee in the positive
(+) line running from one of the prove switches to the cold
end header box.
3 − Install a manometer with hose from the negative (−)
side of the manometer to the tee installed in the negative (−) line and with hose from the positive (+) side of
the manometer to the tee in the positive (+) line.
NOTE − Both sides of the cold end header box are negative.
However the (+) port reads less negative pressure than the
(−) port.
CAI & COLD END HEADER BOX ASSEMBLY
(−045 & 070 SHOWN)
DUAL COMBUSTION AIR PROVE SWITCH
G61MP−090, −110 & −135
first stage
negative
pressure
second stage
positive
pressure
FIGURE 9
To troubleshoot the prove switches, temporarily jumper them.
The unit will not fire with the switches jumpered. Therefore, the
prove switches must be bypassed after the combustion air inducer is activated. This will determine if the prove switches
and furnace are operating properly. However, this may not indicate if the sealed combustion system is operating properly.
Checks of pressure differential can aid in troubleshooting.
When measuring the pressure differential, readings should be
taken at the prove switch. Lack of differential usually indicates
problems in the intake or exhaust piping, bu t ma y indicat e
problems in the heat exchanger, condensing coil, header boxes, combustion inducer or other components.
Measuring pressure differential
The differential pressure is the difference in pressure measured across the cold end header box orifice.
Install tee’s in the
negative line and
positive line then
connect hoses to
manometer.
_
+
cold end header box
prove switches
_
+
orifice size
FIGURE 10
4 − Operate unit and observe manometer reading. Read-
ings will change as heat exchanger warms.
a. Take one reading immediately after start-up.
b. Take a second reading after unit has reached steady
state (approximately 5 minutes). This will be the pressure differential.
The pressure differential should be greater
than those listed in table 8, 9 or 10.
5 − Remove thermostat demand and allow to cycle off.
6 − Remove manometer and tee’s. Reinstall combustion air
sensing hoses to the prove switch.
7 − Repeat steps 1 through 6 for the other prove switch.
Page 14
12. Combustion Air Inducer (B6)
0.95"
0.95"
0.85"
0.50"
0.95"
0.95"
All G61MP units use a combustion air inducer to move air
through the burners and heat exchanger during heating
operation. The blower uses a PSC 120VAC motor. The
motor operates during all heating operation and is controlled by the ignition control A3. Blower operates continuously while there is a call for heat. The burner ignition control will not proceed with the ignition sequence until combustion air inducer operation is sensed by the proving switches.
The CAI is installed on the cold end header box. The cold
end header box is a single piece made of hard plastic.
The box has an internal channel where the combustion
air inducer creates negative pressure at unit start up. The
channel contains an orifice used to regulate flow created
by the CAI. The box has pressure taps for the CAI prove
switch hoses.
The prove switches measure the pressures across the
CAI orifice or difference in the channel and the box. A
window is provided on the bottom right hand side of the
box to indicate orifice size. See figure 10. See table 7 for
orifice size per unit. If replacement is necessary the
gaskets used to seal the box to the vestbule panel
and the CAI to the box, must also be replaced.
TABLE 7
G61MP Unit C.A.I. Orifice Size
−045 .719"
−070 .938"
−090 1.063"
−110 1.313"
−135 1.688"
TABLE 8
0’ to 4500’
G61MP Unit
Set Point
Second Stage
Set Point
First Stage
−045
−070
"
"
−090
−110
"
"
−135 0.60" 0.35"
TABLE 9*
4501’ to 7500’
G61MP Unit
Set Point
Second Stage
Set Point
First Stage
−045
−070
"
"
−090 0.75" 0.50"
−110 0.85" 0.50"
−135 0.55" 0.35"
*Unit may require conversion kit at this altitude. See High Altitude
table.
TABLE 10*
7501’ to 10,000’
G61MP Unit
Set Point
Second Stage
Set Point
First Stage
−045 0.95" 0.95"
−070 0.85" 0.85"
−090 0.60" 0.35"
−110 0.85" 0.50"
−135 0.55" 0.35"
*Unit may require conversion kit at this altitude. See High Altitude
table.
Page 15
II−PLACEMENT AND INSTALLATION
36B−045
36B−070
60C−090
60D−135
OUTDOOR TERMINATION KITS AND CORRESPONDING EQUIVALENCIES
Outdoor
Exhaust
Accelerator
(Dia. X
Length)
UNIT
MODEL
VENT
PIPE
DIA.
(in.)
1−1/2" X 12"
2 4
2−1/2 5
3 7
4 14
2 4
2−1/2 5
3 8
4 14
Not
Allowed
Not
Allowed
Not
Allowed
Not
Allowed
Not
Allowed
Not
Allowed
Not
Allowed
Not
Allowed
Not
Allowed
60C−110
2
2−1/2
3
4
2−1/2
3
4
3
4
*Requires field−provided and installed 1−1/2" exhaust accelerator.
**Requires field−provided and installed 2" exhaust accelerator.
***For use only in non−direct vent applications, when snow riser is
Outdoor
Exhaust
Accelerator
(Dia. X
1−1/2"
Concen-
tric Kit
Length)
2" X 12" 71M80 60M29 60L46 22G44
Not
Allowed
Not
Allowed
Not
Allowed
Not
Allowed
Not
Allowed
Not
Allowed
Not
Allowed
Not
Allowed
1
2
2
4
2
2
4
6
10
12
15
21
42
12
15
24
42
Not
Allowed
Not
Allowed
Not
Allowed
Not
Allowed
Not
Allowed
Not
Allowed
Not
Allowed
Not
Allowed
Not
Allowed
TABLE 11
Vent Pipe Length Equivalency (feet)
2" Con-
centric
Allowed
Allowed
Allowed
Allowed
Allowed
Allowed
Allowed
Allowed
Allowed
Allowed
3" Con-
centric
Kit
Not
Allowed
Not
Allowed
Not
Allowed
Not
Allowed
Not
Allowed
Not
Allowed
Not
Allowed
Not
Allowed
3 3
6 6
6 6
12 12
6 6
6 6
12 12
Not
Not
Kit
Not
Not
Not
Not
Not
Not
Not
Not
15
25
2" Wall
Plate Kit
3" Wall
Plate Kit
44J40
81J20
4 4* 4 4
5 5* 5 5
7 7* 7 7
14 14* 14 14
4 4* 4 4
5 5* 5 5
8 8* 8 8
14 14* 14 14
Not
Allowed
Not
Allowed
Not
Allowed
Not
Allowed
Not
Allowed
Not
Allowed
Not
Allowed
Not
Allowed
Not
Allowed
1
2
2
4
2
2
4
6
10
2" Wall
Kit with
Vent Ex-
tension
30G28 15F74
Not
Allowed
Not
Allowed
Not
Allowed
Not
Allowed
Not
Allowed
Not
Allowed
Not
Allowed
Not
Allowed
Not
Allowed
not required. Requires field−provided and installed 2" exhaust accelerator.
2" Wall
Ring Kit
1**
2**
2**
4**
2***
2***
4***
6***
10***
Page 16
A−Vent Piping Guidelines
The G61MP can be installed as either a Non−Direct Vent
or a Direct Vent gas central furnace.
NOTE − In Non-Direct Vent installations, combustion air is
taken from indoors and flue gases are discharged outdoors.
In Direct Vent installations, combustion air is taken from outdoors and flue gases are discharged outdoors.
Intake and exhaust pipe sizing in Direct Vent applications
and exhaust pipe sizing in Non-Direct Vent applications −−
Size pipe according to tables 12 and 13. Table 12 lists the
minimum equivalent vent pipe lengths permitted. Table 13
lists the maximum equivalent pipe lengths permitted.
Maximum vent length is defined as:
Total length (linear feet) of pipe,
Plus Equivalent length (feet) of fittings,
Plus Equivalent length (feet) of termination.
NOTE − Include ALL pipe and ALL fittings, both in
doors and outdoors.
Regardless of the diameter of pipe used, the standard roof
and wall terminations described in section Exhaust Piping
Terminations should be used. Exhaust vent termination
pipe is sized to optimize the velocity of the exhaust gas as
it exits the termination. Refer to table 14.
*NOTE − The exhaust pipe should be offset a minimum of
12 inches to avoid the possibility of water droplets being released from the exhaust termination. The minimum exhaust vent length is 15 ft. Shorter exhaust vent lengths may
result in the discharge of water droplets from the exhaust
termination, in spite of the 12−inch vertical offset.
Each 90° elbow (including those provided with the furnace)
of any diameter is equivalent to 5 feet (1.52m) of vent pipe
of the same diameter. Two 45° elbows are equivalent to
one 90° elbow of the same diameter. One 45° elbow is
equal to 2.5 feet (.76m) of vent pipe of the same diameter.
In some applications which permit the use of several different sizes of vent pipe, a combination vent pipe may be
used. Contact the Application Department for assistance in
sizing vent pipe in these applications.
NOTE − The flue collar on all models is sized to accommodate 2" Schedule 40 flue pipe. When vent pipe which is
larger than 2" must be used in an upflow application, a 2"
elbow must be applied at the flue collar in order to properly transition to the larger diameter flue pipe. This elbow
must be added to the elbow count used to determine acceptable vent lengths. Assign an equivalent feet value to
this elbow according to the larger size pipe being used.
Contact the Application Department for more information
concerning sizing of vent systems which include multiple
pipe sizes.
12" Min.
Upflow and Downflow Application
Rooftop Termination
12" Min.
Horizontal Application
Rooftop Termination
Exhaust Pipe Offset
12" Min.
Upflow and Downflow Application
Side Wall Termination
12" Min.
Horizontal Application
Side Wall Termination
FIGURE 11
Page 17
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