G61MP
Corp. 0308−L6
Revised 10−2004
Service Literature
G61MP SERIES UNITS
G61MP series units are high−efficiency multi−position (up-
flow, downflow, horizontal right and left) gas furnaces
manufactured with Lennox Duralok Plust heat exchang-
ers 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 Ox-
ides (NO ) Standards and California Seasonal Efficiency re-
x
quirements. All units use a redundant gas valve to assure
safety shut−off as required by C.S.A.
All specifications in this manual are subject to change. Pro-
cedures outlined in this manual are presented as a recom-
mendation only and do not supersede or replace local or
state codes. In the absence of local or state codes, the
guidelines and procedures outlined in this manual (except
where noted) are recommendations only and do not consti-
tute code.
IMPORTANT
Improper installation, adjustment, alteration, service
or maintenance can cause property damage, person-
al injury or loss of life. Installation and service must
be performed by a qualified installer, service agency
or the gas supplier.
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
VI Maintenance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35
VII Wiring and Sequence of Operation . . . . . . . . . . . . 38
VIII Field Wiring and Jumper Setting . . . . . . . . . . . . . 46
IX Control Board Troubleshooting . . . . . . . . . . . . . . . . 48
WARNING
Electric shock hazard. Can cause injury
or death. Before attempting to perform
any service or maintenance, turn the
electrical power to unit OFF at discon-
nect switch(es). Unit may have multiple
power supplies.
WARNING
Sharp edges.
Be careful when servicing unit to avoid sharp edges
which may result in personal injury.
Page 1
© 2003 Lennox Industries Inc.
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SPECIFICATIONS
ModelꢀNo.
Inputꢀ− Btuh (kW)
Outputꢀ− Btuh (kW)
G61MP−48C−110
110,000 (32.2)
104,000 (30.5)
45 − 75 (25 − 42)
75,000 (22.0)
72,000 (21.1)
30 − 60 (18 − 36)
94.1%
G61MP−60C−110
110,000 (32.2)
104,000 (30.5)
35 − 65 (21 − 39)
75,000 (22.0)
72,000 (21.1)
25 − 55 (14 − 31)
94.1%
G61MP−60D−135
132,000 (38.7)
124,000 (36.3)
40 − 70 (24 − 42)
90,000 (26.4)
86,000 (25.2)
30 − 60 (18 − 36)
94.1%
Gas
Heating
Performance
High Fire
Temperature rise range − _F (_C)
Low Fire
Inputꢀ− Btuh (kW)
Outputꢀ− Btuh (kW)
Temperature rise range − _F (_C)
1
AFUE
California Seasonal Efficiency
Highꢀstaticꢀ(CSA)ꢀ− in.ꢀw.g. (Pa)
88.4%
87.0%
87.7%
0.5
0.5
0.5
2
Connections
in.
Intake Pipe (PVC)
2
2
3
2
Exhaust Pipe (PVC)
2
2
3
Condensate Drain Trap (PVC pipe) − i.d.
with field supplied (PVC coupling) − o.d.
hose with hose clamp − i.d. x o.d.
GasꢀpipeꢀsizeꢀIPS
1/2
1/2
1/2
3/4
3/4
3/4
1−1/4 x 1
1−1/4 x 1
1−1/4 x 1
1/2
1/2
1/2
Indoor
Blower
Wheelꢀnominalꢀdiameter ꢀxꢀwidth −ꢀin. (mm)
Motorꢀoutput − hp (W)
10 x 10 (254 x 254)
1/2 (373)
3 − 4 (10.5 − 14.0)
178 (81)
11−1/2 x 10 (292 x 229)
1 (746)
11−1/2 x 10 (292 x 229)
1 (746)
Tonsꢀ(kW) ofꢀadd-onꢀcooling
lbs. (kg) − 1 package
4 − 5 (14.0 − 17.5)
186 (84)
4 − 5 (14.0 − 17.5)
206 (93)
ShippingꢀData
Electricalꢀcharacteristics
120 volts − 60 hertz − 1 phase (less than 12 amps)
OPTIONAL ACCESSORIES − MUST BE ORDERED EXTRA
3, 4
Air Filter and Rack Kit −
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)
Size of filter
5
Side Return
6 ft. (1.8 m)
Single 44J22 or Ten Pack (66K63) − (1) 16 x 25 x 1 in. (406 x 635 x 25 mm)
Condensate Drain Heat
Cable
26K68
26K69
26K70
39G04
39G03
26K68
26K69
26K68
26K69
24 ft. (7.3 m)
50 ft. (15.2 m)
26K70
26K70
Heat Cable Tape
39G04
39G04
Fiberglass − 1/2 in. (38 mm) x 66 ft. (20 m)
Aluminum foil − 2 in. (25 mm) x 60 ft. (18 m)
Catalog Number − Shipping Weight
Dimensions − H x W x D − in. (mm)
39G03
39G03
4
EZ Filter Base
73P57 − 8 lbs. (4 kg)
73P58 − 10 lbs. (5 kg)
73P58 − 10 lbs. (5 kg)
4 x 21−5/8 x 28−5/8
(102 x 549 x 727)
4 x 24−5/8 x 28−5/8
(102 x 625 x 727)
4 x 24−5/8 x 28−5/8
(102 x 625 x 727)
Size of field provided filter − in. (mm)
20 x 25 x 1
(508 x 635 x 25)
24 x 24 x 1
(610 x 610 x 25)
24 x 24 x 1
(610 x 610 x 25)
Down−Flow Additive Base
11M61
59M16
11M61
59M16
11M62
59M16
5
High Altitude Orifice Kit − Natural Gas Only
6
High Altitude Pressure Switch Kit − Order two each
− − −
− − −
56M93
4501−10,000 ft. (1372−3048 m)
Horizontal Support Frame Kit − Ship. Weight − lbs. (kg)
56J18 − 18 (8)
59M13
59M14
59M87
− − − −
56J18 − 18 (8)
59M13
56J18 − 18 (8)
59M13
LPG/Propane Kit
0−7500 ft. (0−2286 m)
7501−10,000ft. (2286−3048m)
59M14
59M14
Natural to LPG/Propane Kit
RAB Return Air Base
59M87
59M87
RAB60C (12M71)
33K97
RAB60D (12M72)
− − −
7
Termination Kits − Concentric
Roof/Wall
2 inch (51 mm)
3 inch (76 mm)
33K97
60L46
Direct Vent
Applications
60L46
60L46
Wall
Close−Coupled 3 inch (76 mm)
2 inch (51 mm)
44J40
44J40
44J40
7,8
Termination Kits Roof
Direct Vent or Non−
Direct Vent
Wall
15F75
15F75
− − −
3 inch (76 mm)
44J41
44J41
44J41
9
Ring Kit 2 inch (51 mm)
15F74
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.
Determine from venting tables proper exhaust pipe size and termination kit required.
Cleanable polyurethane frame type filter.
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.
2
3
4
5
6
7
8
9
Required for proper operation at altitudes from 7501 to 10,000 ft. (2286 to 3048 m).
Required for proper operation at altitudes over 4500 ft. (1370 m).
See Installation Instructions for specific venting information.
Kits contain enough parts for two, non−direct vent installations.
Non−direct vent applications only.
Page 3
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BLOWER DATA
G61MP−36B−045 PERFORMANCE (Less Filter)
External Static
Pressure
Air Volume / Watts at Different Blower Speeds
High
Medium−High
Medium−Low
Low
in. w.g.
Pa
25
cfm
1555
1515
1470
1410
1350
1290
1220
1145
1050
945
L/s
735
715
695
665
640
610
575
540
495
445
Watts
630
605
580
555
535
505
485
460
425
410
cfm
1410
1385
1345
1310
1250
1205
1145
1080
985
L/s
665
655
635
620
590
570
540
510
465
425
Watts
585
555
520
495
465
450
420
400
365
345
cfm
1190
1190
1170
1155
1120
1080
1020
975
L/s
560
560
550
545
530
510
480
460
410
390
Watts
520
485
455
440
410
390
365
345
320
305
cfm
1030
1020
1010
1000
980
L/s
485
480
475
470
465
450
430
405
370
345
Watts
435
415
400
385
360
345
320
300
285
270
0.00
0.10
0.20
0.30
0.40
0.50
0.60
0.70
0.80
0.90
25
50
75
100
125
150
175
200
225
950
905
860
870
785
900
825
730
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.
G61MP−36B−070 PERFORMANCE (Less Filter)
Air Volume / Watts at Different Blower Speeds
External Static
Pressure
High
Medium−High
Medium−Low
Low
in. w.g.
0.00
0.10
0.20
0.30
0.40
0.50
0.60
0.70
0.80
0.90
Pa
0
cfm
1640
1600
1540
1495
1420
1360
1275
1170
1080
945
L/s
775
755
725
705
670
640
600
555
510
445
Watts
660
635
605
580
545
525
490
465
440
400
cfm
1415
1395
1370
1345
1275
1245
1165
1085
1010
840
L/s
665
660
650
635
605
590
550
515
475
395
Watts
575
550
525
505
480
450
410
385
360
320
cfm
1160
1160
1160
1145
1125
1080
1025
965
L/s
545
545
545
540
530
510
485
430
410
360
Watts
485
460
445
425
395
375
350
335
310
275
cfm
1005
1000
995
990
965
945
900
860
775
710
L/s
475
470
470
465
455
445
425
405
365
335
Watts
410
385
375
365
345
325
305
295
270
245
25
50
75
100
125
150
175
200
225
865
765
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.
G61MP−48C−090 PERFORMANCE (Less Filter)
Air Volume / Watts at Different Blower Speeds
External Static
Pressure
High
Medium−High
Medium−Low
Low
in. w.g.
0.00
0.10
0.20
0.30
0.40
0.50
0.60
0.70
0.80
0.90
Pa
0
cfm
L/s
1030
1005
985
955
915
880
820
775
725
630
Watts
930
885
840
800
760
725
670
640
600
540
cfm
1835
1825
1810
1775
1735
1660
1590
1475
1340
1170
L/s
865
860
855
835
820
785
750
695
630
555
Watts
790
750
720
685
650
600
575
520
465
440
cfm
1520
1510
1505
1500
1480
1430
1380
1290
1175
1070
L/s
715
710
710
705
700
675
650
610
555
505
Watts
630
610
580
565
535
505
475
450
405
375
cfm
1280
1275
1270
1265
1250
1215
1175
1105
1020
950
L/s
605
600
600
595
590
575
555
520
480
450
Watts
510
495
475
460
440
425
410
375
355
330
2180
2135
2085
2030
1940
1865
1740
1645
1540
1335
25
50
75
100
125
150
175
200
225
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.
G61MP−48C−110 PERFORMANCE (Less Filter)
Air Volume / Watts at Different Blower Speeds
External Static
Pressure
High
L/s
Medium−High
L/s
Medium−Low
L/s
Low
L/s
in. w.g.
0.00
0.10
0.20
0.30
0.40
0.50
0.60
0.70
0.80
0.90
Pa
0
cfm
Watts
880
850
805
750
725
680
660
620
550
520
cfm
1880
1855
1815
1755
1715
1630
1550
1410
1230
1120
Watts
755
730
690
650
625
580
550
505
450
415
cfm
1490
1480
1475
1475
1465
1420
1360
1210
1125
1050
Watts
602
585
560
545
510
490
460
405
380
365
cfm
1235
1230
1225
1220
1215
1150
1110
1035
970
Watts
485
475
460
445
430
400
380
350
325
310
2160
2100
2035
1965
1885
1780
1690
1575
1375
1225
1020
990
960
925
890
840
800
745
650
580
890
705
580
580
580
575
575
540
525
490
460
420
25
875
700
50
860
695
75
830
695
100
125
150
175
200
225
810
690
770
670
735
640
665
570
580
530
530
495
885
NOTES − All air data is measured external to unit without filter (not furnished − field provided).
Air volume based on bottom air return air. Actual air volume may vary on side return air applications.
Page 4
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BLOWER DATA
G61MP−60C−090 PERFORMANCE (Less Filter) − Single Side Return Air − Air volumes in bold require field fabricated transi-
tion to accommodate 20 x 25 x 1 in. (508 x 635 x 25 mm) air filter in order to maintain proper air velocity.
Air Volume / Watts at Different Blower Speeds
External Static
Pressure
High
L/s
Medium−High
L/s
Medium−Low
L/s
Low
L/s
in. w.g.
Pa
0
cfm
Watts
1495
1475
1435
1380
1350
1305
1270
1205
1190
1150
cfm
Watts
1155
1135
1080
1035
1015
990
cfm
Watts
895
865
845
825
815
790
775
760
745
715
cfm
Watts
695
690
685
680
670
655
640
620
605
580
0.00
0.10
0.20
0.30
0.40
0.50
0.60
0.70
0.80
0.90
2835
2785
2715
2620
2550
2450
2365
2240
2185
2015
1335
1315
1280
1235
1205
1155
1115
1060
1030
950
2340
2345
2275
2260
2230
2175
2130
2070
1965
1820
1105
1105
1075
1065
1055
1025
1005
975
1800
1805
1825
1840
1845
1850
1830
1815
1775
1690
850
1440
1515
1560
1600
1620
1615
1615
1595
1555
1440
680
715
735
755
765
765
760
755
735
680
25
855
50
860
75
870
100
125
150
175
200
225
870
870
940
865
915
855
925
865
840
860
820
800
NOTES − All air data is measured external to unit without filter (not furnished − field provided).
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.
Air Volume / Watts at Different Blower Speeds
External Static
Pressure
High
L/s
Medium−High
L/s
Medium−Low
L/s
Low
L/s
in. w.g.
Pa
0
cfm
Watts
1450
1415
1385
1335
1300
1260
1220
1190
1140
1090
cfm
Watts
1105
1080
1050
1030
990
cfm
Watts
900
885
870
850
825
800
775
745
715
685
cfm
Watts
700
700
695
690
675
665
650
630
615
590
0.00
0.10
0.20
0.30
0.40
0.50
0.60
0.70
0.80
0.90
2840
2765
2695
2605
2530
2420
2330
2250
2135
2030
1340
1305
1270
1230
1195
1140
1100
1060
1010
960
2345
2365
2345
2315
2265
2210
2145
2050
2000
1885
1105
1115
1895
1950
1985
1990
1990
1970
1930
1875
1810
1720
895
1515
1580
1620
1645
1665
1675
1665
1645
1620
1560
715
745
765
775
785
790
785
775
765
735
25
920
50
1105
1090
1070
1045
1010
965
935
75
940
100
125
150
175
200
225
940
955
930
925
910
885
885
945
865
855
890
830
810
NOTES − All air data is measured external to unit without filter (not furnished − field provided).
G61MP−60C−110 PERFORMANCE (Less Filter) − Single Side Return Air − Air volumes in bold require field fabricated transi-
tion 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
Air Volume / Watts at Different Blower Speeds
High
L/s
Medium−High
L/s
Medium−Low
L/s
Low
L/s
in. w.g.
0.00
0.10
0.20
0.30
0.40
0.50
0.60
0.70
0.80
0.90
Pa
0
cfm
2625
2570
2410
2425
2335
2270
2170
2110
2035
1900
Watts
1350
1330
1305
1265
1220
1195
1155
1130
1090
1055
cfm
Watts
1080
1060
1035
990
cfm
Watts
885
865
845
825
810
785
765
730
705
680
cfm
Watts
700
700
690
675
660
640
630
610
580
565
1240
1215
1135
1145
1100
1070
1025
995
2310
2325
2285
2230
2175
2120
2045
1950
1885
1760
1090
1095
1080
1055
1025
1000
965
1885
1910
1930
1925
1910
1895
1860
1795
1745
1665
890
1515
1575
1620
1635
1640
1640
1630
1590
1540
1470
715
745
765
770
775
775
770
750
725
695
25
900
50
910
75
905
100
125
150
175
200
225
950
900
935
895
885
875
920
855
845
960
890
820
825
895
830
780
785
NOTES − All air data is measured external to unit without filter (not furnished − field provided).
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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
Air Volume / Watts at Different Blower Speeds
High
L/s
Medium−High
L/s
Medium−Low
L/s
Low
L/s
in. w.g.
0.00
0.10
0.20
0.30
0.40
0.50
0.60
0.70
0.80
0.90
Pa
0
cfm
Watts
1385
1355
1315
1275
1250
1205
1185
1150
1090
1050
cfm
Watts
1090
1075
1015
990
cfm
Watts
935
885
865
840
830
790
765
730
710
675
cfm
Watts
710
735
690
675
660
665
650
635
610
590
2720
2665
2585
2505
2435
2350
2255
2160
2020
1910
1285
1255
1220
1180
1150
1110
1065
1020
955
2410
2385
2350
2290
2235
2170
2100
2005
1905
1820
1135
1125
1110
2055
2025
2030
2025
2030
1975
1915
1865
1810
1705
970
1620
1730
1680
1695
1695
1735
1720
1680
1625
1540
765
815
795
800
800
820
810
795
765
725
25
955
50
955
75
1080
1055
1025
990
955
100
125
150
175
200
225
940
960
930
930
895
905
945
840
880
900
825
855
900
860
795
805
NOTES − All air data is measured external to unit without filter (not furnished − field provided).
G61MP−60D−135 PERFORMANCE (Less Filter) − Single Side Return Air − Air volumes in bold require field fabricated transi-
tion 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
Air Volume / Watts at Different Blower Speeds
High
L/s
Medium−High
L/s
Medium−Low
L/s
Low
L/s
in. w.g.
0.00
0.10
0.20
0.30
0.40
0.50
0.60
0.70
0.80
0.90
Pa
0
cfm
Watts
1440
1405
1370
1330
1290
1265
1230
1190
1160
1110
cfm
Watts
1100
1065
1055
1015
985
cfm
Watts
890
865
850
825
805
790
765
740
710
685
cfm
Watts
690
685
675
670
655
645
630
605
590
570
2665
2615
2530
2470
2380
2310
2200
2120
2025
1930
1260
1235
1195
1165
1125
1090
1035
1000
955
2325
2310
2280
2235
2175
2120
2055
1970
1890
1800
1095
1090
1075
1055
1025
1000
970
1865
1915
1925
1920
1910
1890
1835
1790
1720
1655
880
1410
1465
1570
1590
1590
1595
1580
1545
1515
1440
665
690
740
750
750
755
745
730
715
680
25
905
50
910
75
905
100
125
150
175
200
225
900
965
890
935
865
930
900
845
890
875
810
910
850
835
780
NOTES − All air data is measured external to unit without filter (not furnished − field provided).
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
Air Volume / Watts at Different Blower Speeds
High
L/s
Medium−High
L/s
Medium−Low
L/s
Low
L/s
in. w.g.
0.00
0.10
0.20
0.30
0.40
0.50
0.60
0.70
0.80
0.90
Pa
0
cfm
2730
2670
2600
2525
2445
2360
2290
2205
2110
1970
Watts
1465
1440
1400
1360
1325
1280
1255
1220
1195
1120
cfm
Watts
1125
1100
1070
1045
1015
985
cfm
Watts
915
890
865
845
820
790
755
730
710
690
cfm
Watts
680
675
665
655
645
635
615
600
580
545
1290
1260
1225
1190
1155
1115
1080
1040
995
2425
2400
2365
2315
2260
2195
2130
2035
1945
1835
1145
1135
1115
2055
2065
2045
2035
2020
1960
1900
1825
1765
1680
970
1560
1590
1620
1615
1615
1610
1600
1570
1540
1540
735
750
765
760
760
760
755
740
725
725
25
975
50
965
75
1095
1065
1035
1005
960
960
100
125
150
175
200
225
955
925
965
895
910
860
915
880
830
930
865
830
795
NOTES − All air data is measured external to unit without filter (not furnished − field provided).
Page 6
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G61MP PARTS ARRANGEMENT
TOP CAP
DuralokPlusTM
HEAT EXCHANGER
ASSEMBLY
CABINET
BURNER BOX
ASSEMBLY
GAS VALVE
AND MANIFOLD
FLUE
COLLAR
COMBUSTION
AIR PROVE PROVE
SWITCHES*
WARM HEADER
(COLLECTOR)
BOX
COMBUSTION AIR
INDUCER
CONDENSER COIL
BURNER
ACCESS
PANEL
PRIMARY LIMIT
COLD HEADER
(COLLECTOR)
BOX
BLOWER
ACCESS
DOOR
DOOR
INTERLOCK
SWITCH
SECONDARY
LIMITS (2)
*G61MP−090 shown.
G61MP−045 and −070
are equipped with
two switches.
BLOWER
ASSEMBLY
SIGHT
GLASS
CONTROL BOX
FIGURE 1
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I−UNIT COMPONENTS
3. Circuit Breaker (CB8)
A 24V circuit breaker is also located in the control box.
The switch provides overcurrent protection to the trans-
former (T1). The breaker is rated 3A at 32V. If the current
exceeds this limit the breaker will trip and all unit opera-
tion will shutdown. The breaker can be manually reset
G61MP unit components are shown in figure 1. The gas
valve, combustion air inducer and burners can be ac-
cessed by removing the burner access panel. Electrical
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.
CIRCUIT BREAKER CB8
ELECTROSTATIC DISCHARGE (ESD)
Precautions and Procedures
PRESS TO RESET
FIGURE 3
CAUTION
Electrostatic discharge can affect electronic
components. Take precautions during furnace
installation and service to protect the furnace’s
electronic controls. Precautions will help to
avoid control exposure to electrostatic dis-
charge by putting the furnace, the control and
the technician at the same electrostatic poten-
tial. Neutralize electrostatic charge by touching
hand and all tools on an unpainted unit surface,
such as the gas valve or blower deck, before per-
forming any service procedure.
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 igni-
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 accesso-
shooting diagnostic codes.
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 sec-
ondary.
2. Door Interlock Switch (S51)
A door interlock switch rated 14A at 125VAC is wired in se-
ries with line voltage. When the blower door is removed the
unit will shut down.
Electronic Ignition
At the beginning of the heat cycle, SureLight control moni-
tors the first stage and second stage combustion air induc-
er prove switch. The control will not begin the heating cycle
if the first stage prove switch is closed (by−passed). Like-
wise the control will not begin the second stage heating
cycle if the second stage prove switch is closed, and will al-
low 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−min-
ute re−set period.
CONTROL BOX G61MP
CIRCUIT
BREAKER
DOOR INTERLOCK
SWITCH
TRANSFORMER
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-
SURELIGHT
CONTROL
BOARD
FIGURE 2
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onds. After a total of five trials for ignition (including the ini-
tial trial), the control goes into Watchguard−Flame Failure
mode. After a 60−minute reset period, the control will begin
the ignition sequence again.
TABLE 1
Heating Fan Off Delay
Delay (Seconds)
Switch 1
Switch 2
The SureLight control board has an added feature that pro-
longs the life of the ignitor. After a successful ignition, the
SureLight control utilizes less power to energize the ignitor
on successive calls for heat. The control continues to ramp
down the voltage to the ignitor until it finds the lowest
amount of power that will provide a successful ignition. This
amount of power is used for 255 cycles. On the 256th call
for heat, the control will again ramp down until the lowest
power is determined and the cycle begins again.
60
90
Off
Off
On
On
Off
On
Off
On
120
180
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.
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
application. The jumper is factory set on ꢁTWO" for use
with a two−stage thermostat with two stage heat. Re−posi-
tion jumper to ꢁSINGLE" for use with a single stage thermo-
stat 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 in-
door blower will operate on low heat speed. After a 10 min-
ute 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 com-
bustion 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.
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-
TABLE 2
Cooling Fan Off Delay
Dip Switch Settings
Delay (Seconds)
Switch 4
Off
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 satis-
fied) 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−ener-
gized. Adjust the fan−off delay to achieve a supply air tem-
perature between 90° − 110° at the instant the blower is de−
energized. (Longer delay times allow for lower air tempera-
ture, shorter delay times allow for higher air temperature).
2
45
On
Diagnostic LED’s (DS1 and DS2)
Two diagnostic LED’S are located on the two−stage inte-
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.
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TABLE 3
TWO−STAGE INTEGRATED CONTROL BOARD
Integrated Control Board Terminals
120VAC Neutral
LINE
XFMR
EAC
Line
Transformer
LEDs
Electronic Air Cleaner
Indoor Blower
Humidifier
DIP
SWITCHES
1 − 4
CIRC
HUM
120VAC Line
HUM
XMFR
LINE
Humidifier
Transformer
Line
PARK
For Unused Leads
Cooling Speed
Electronic Air Cleaner
HIigh Heat Speed
COOL
EAC
HI HEAT
LO HEAT
W915 FACTORY INSTALLED JUMPER
(MUST CLIP FOR 2 STAGE COOL)
Low Heat, Low Cool and Continuous Fan
Speed
TABLE 4
Integrated Control Board 5 Pin Terminal
PIN #
Function
Ignitor
1
2
3
4
5
THERMOSTAT CONNECTIONS (TB1)
Combustion Air Inducer High Speed
Combustion Air Inducer Low Speed
Combustion Air Inducer Neutral
Ignitor Neutral
TABLE 5
Integrated Control Board 12Pin Terminal
PIN #
1
Function
Gas Valve 2nd Stage (High Fire)
Second Stage Prove Switch
Not Used
2
3
4
Ground
5
24V Hot
DIP SWITCH(ES)
FUNCTION
6
Primary Limit In
1 and 2
Blower Off Delay (Heating Mode)
Second Stage ON Delay (Single−stage t’stat)
Blower Off Delay (Cooling Mode)
7
Gas Valve 1st stage (Low Fire)
Gas Valve Common
24V Neutral
3
4
8
9
10
11
12
Ground
Primary Limit Out
1st Stage Prove Switch
FIGURE 4
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TABLE 6
DIAGNOSTIC CODES
DS1
DS2
DESCRIPTION
SIMULTANEOUS
SLOW FLASH
SIMULTANEOUS
FAST FLASH
SIMULTANEOUS
SLOW FLASH
SIMULTANEOUS
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;
SLOW FLASH
ON
OFF
SLOW FLASH
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.
OFF
FAST FLASH
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.
ALTERNATING
SLOW FLASH
ALTERNATING
SLOW FLASH
SLOW FLASH
OFF
Flame sensed without gas valve energized.
ON
ON
ON
OFF
ON
Circuit board failure or control wired incorrectly. Check 24 and 115 volts to board.
OFF
FAST FLASH
SLOW FLASH
SLOW FLASH
FAST FLASH
Main power polarity reversed. Switch line and neutral.
Low flame signal. Measures below 0.23 microAmps. Replace flame sense rod.
The following conditions are sensed during the ignitor warm−up period only:
1) Improper main ground;
2) Broken ignitor; OR: Open ignitor circuit;
ALTERNATING
FAST FLASH
ALTERNATING
FAST FLASH
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
SUPPLY AIR BLOWER
AND SECONDARY LIMITS
1. Blower Motor (B3) and Capacitor (C4)
All G61MP units use direct drive blower motors. All motors
are 120V permanent split capacitor motors to ensure maxi-
mum efficiency. Ratings for capacitors will be on motor
nameplate. See SPECIFICATIONS section for motor speci-
fications.
SECONDARY
LIMIT (S)
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)
MOTOR/BLOWER
ASSEMBLY
The secondary limits (S21) on G61MP units are located in the
blower compartment on the back side of the blower housing.
dary limts. When excess heat is sensed in the blower compart-
ment, the limit will open. If the limit is open, the furnace control
energizes the supply air blower and closes the gas valve. The
limit automatically resets when unit temperature returns to nor-
mal. The switch is factory set to open at 125°F and cannot be
adjusted.
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
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C−Heating Components
3. Flame Sensor
4. Ignitor
The SureLight ignitor is made of durable silicon nitride. Ig-
nitor longevity is enhanced by controlling voltage to the ig-
nitor. The board finds the lowest ignitor temperature which
will successfully light the burner, thus increasing the life of
the ignitor. Due to this feature of the board, voltage cannot
be measured so ignitor must be ohmed. Ohme value
A flame sensor is located on the left side of the burner sup-
tom of the burner box and the tip protrudes into the flame
envelope of the left−most burner. The sensor can be re-
moved for service without removing any part of the burn-
ers. During operation, flame is sensed by current passed
through the flame and sensing electrode. The SureLight
control allows the gas valve to remain open as long as
flame signal is sensed.
NOTE − The G61MP furnace contains electronic com-
ponents that are polarity sensitive. Make sure that the
furnace is wired correctly and is properly grounded.
All units use inshot burners. Burners are factory set and do not
require adjustment. The manifold brackets are slotted so burn-
ers can be removed as an assembly for service. Burner main-
tenance and service is detailed in the MAINTENANCE sec-
tion of this manual. Each burner uses an orifice which is pre-
cisely 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.
NORMAL FLAME SIGNAL > 0.23 MICROAMPS
LOW FLAME SIGNAL
DROP OUT SIGNAL
< 0.22 MICROAMPS
= 0.16 MICROAMPS
5/16"
A flame retention ring in the end of each burner maintains cor-
rect flame length and shape and keeps the flame from lifting off
the burner head. In addition, the burner entrance to each clam-
shell is fitted with a corbel cup (orifice) used to direct the flow
of combustion products.
FIGURE 6
SureLight Ignitor Location
MEASUREMENT IS TO I.D.
OF RETENTION RING
5/8"
13/32’
5/16"
BRACKET
IGNITOR
BURNERS FRONT VIEW
BURNERS TOP VIEW
FIGURE 7
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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 ter-
minals energizes the valve.
6. Clamshell Heat Exchanger
G61MP units use an aluminized steel primary and stain-
less 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.
Inlet and outlet pressure taps are located on the valve. A regu-
lator 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 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.
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 configura-
tions which can greatly affect the rate of the unit.
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 manu-
al-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.
PRIMARY LIMIT LOCATION
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 but-
ton located on the control.
limit shield
090, −110 and
−135 only
8. Primary Limit Control (S10)
located in the heating vestibule panel. S10 is provided with a
Note orientation of shield and limit if limit is replaced. When ex-
cess 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 nor-
mal. The switch is factory set and cannot be adjusted.
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.
air proving switches. G61MP−090, −110 and −135 units are
equipped with two dual prove switch ꢁassemblies" consist-
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.
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 blow-
er 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
valves are internally redundant to assure safety shut−off. If
the gas valve must be replaced, the same type valve must
be used.
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
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On heat demand (first or second stage) the switch senses
that the combustion air inducer is operating. It closes a cir-
cuit to the furnace control when pressure inside the cold
end header box decreases to a certain set point.
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.
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 con-
densate build up.
3 − Install a manometer with hose from the negative (−)
side of the manometer to the tee installed in the nega-
tive (−) 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.
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.
CAI & COLD END HEADER BOX ASSEMBLY
(−045 & 070 SHOWN)
Install tee’s in the
negative line and
positive line then
connect hoses to
manometer.
DUAL COMBUSTION AIR PROVE SWITCH
G61MP−090, −110 & −135
negative
pressure
first stage
_
_
+
+
second stage
positive
pressure
orifice size
FIGURE 9
prove switches
cold end header box
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 in-
ducer is activated. This will determine if the prove switches
and furnace are operating properly. However, this may not in-
dicate if the sealed combustion system is operating properly.
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 pres-
sure differential.
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, but may indicate
problems in the heat exchanger, condensing coil, head-
er boxes, combustion inducer or other components.
The pressure differential should be greater
5 − Remove thermostat demand and allow to cycle off.
6 − Remove manometer and tee’s. Reinstall combustion air
sensing hoses to the prove switch.
Measuring pressure differential
The differential pressure is the difference in pressure mea-
sured across the cold end header box orifice.
7 − Repeat steps 1 through 6 for the other prove switch.
Page 14
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TABLE 8
12. Combustion Air Inducer (B6)
0’ to 4500’
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 con-
trolled by the ignition control A3. Blower operates continu-
ously while there is a call for heat. The burner ignition con-
trol will not proceed with the ignition sequence until combus-
tion air inducer operation is sensed by the proving switches.
Set Point
Second Stage
Set Point
First Stage
G61MP Unit
−045
−070
−090
−110
−135
0.95"
0.95"
0.85"
0.60"
0.50"
0.35"
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.
TABLE 9*
4501’ to 7500’
Set Point
Second Stage
Set Point
First Stage
G61MP Unit
−045
−070
−090
−110
−135
0.95"
0.95"
0.75"
0.85"
0.55"
0.50"
0.50"
0.35"
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
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.
*Unit may require conversion kit at this altitude. See High Altitude
table.
TABLE 10*
7501’ to 10,000’
Set Point
Second Stage
Set Point
First Stage
G61MP Unit
TABLE 7
G61MP Unit
−045
C.A.I. Orifice Size
.719"
−045
−070
−090
−110
−135
0.95"
0.85"
0.60"
0.85"
0.55"
0.95"
0.85"
0.35"
0.50"
0.35"
−070
.938"
−090
1.063"
−110
1.313"
*Unit may require conversion kit at this altitude. See High Altitude
table.
−135
1.688"
Page 15
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II−PLACEMENT AND INSTALLATION
TABLE 11
OUTDOOR TERMINATION KITS AND CORRESPONDING EQUIVALENCIES
Vent Pipe Length Equivalency (feet)
Outdoor
Exhaust
Accelerator Accelerator Concen-
Outdoor
Exhaust
2" Wall
Kit with
Vent Ex-
tension
1−1/2"
2" Con-
centric
Kit
3" Con-
centric
Kit
VENT
PIPE
DIA.
(in.)
2" Wall
Plate Kit
3" Wall
Plate Kit
2" Wall
Ring Kit
UNIT
MODEL
(Dia. X
Length)
(Dia. X
Length)
tric Kit
44J40
81J20
1−1/2" X 12"
2" X 12"
71M80
60M29
60L46
22G44
30G28
15F74
Not
Allowed
Not
Allowed
Not
Allowed
2
4
5
12
15
21
42
12
15
24
42
4
5
4*
5*
7*
14*
4*
5*
8*
14*
1
4
5
4
5
Not
Allowed
Not
Allowed
Not
Allowed
2−1/2
36B−045
36B−070
60C−090
Not
Allowed
Not
Allowed
Not
Allowed
3
7
7
7
7
Not
Allowed
Not
Allowed
Not
Allowed
4
14
4
14
4
14
4
14
Not
Allowed
Not
Allowed
Not
Allowed
2
4
Not
Allowed
Not
Allowed
Not
Allowed
2−1/2
5
5
5
5
Not
Allowed
Not
Allowed
Not
Allowed
3
8
8
8
8
Not
Allowed
Not
Allowed
Not
Allowed
4
14
14
14
14
Not
Allowed
Not
Allowed
Not
Allowed
Not
Allowed
2
1
2
3
6
3
6
1**
2**
2**
4**
2***
2***
4***
6***
10***
Not
Allowed
Not
Allowed
Not
Allowed
Not
Allowed
2−1/2
2
Not
Allowed
Not
Allowed
Not
Allowed
Not
Allowed
3
2
6
6
2
Not
Allowed
Not
Allowed
Not
Allowed
Not
Allowed
4
4
12
6
12
6
4
Not
Allowed
Not
Allowed
Not
Allowed
Not
Allowed
2−1/2
2
2
Not
Allowed
Not
Allowed
Not
Allowed
Not
Allowed
3
4
3
4
2
6
6
2
60C−110
60D−135
Not
Allowed
Not
Allowed
Not
Allowed
Not
Allowed
4
12
12
15
25
4
Not
Allowed
Not
Allowed
Not
Allowed
Not
Allowed
Not
Allowed
6
6
Not
Allowed
Not
Allowed
Not
Allowed
Not
Allowed
Not
Allowed
10
10
*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
not required. Requires field−provided and installed 2" exhaust ac-
celerator.
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*NOTE − The exhaust pipe should be offset a minimum of
12 inches to avoid the possibility of water droplets being re-
leased from the exhaust termination. The minimum ex-
haust 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.
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 out-
doors and flue gases are discharged outdoors.
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.
Intake and exhaust pipe sizing in Direct Vent applications
and exhaust pipe sizing in Non-Direct Vent applications −−
lists the maximum equivalent pipe lengths permitted.
In some applications which permit the use of several differ-
ent sizes of vent pipe, a combination vent pipe may be
used. Contact the Application Department for assistance in
sizing vent pipe in these applications.
Maximum vent length is defined as:
Total length (linear feet) of pipe,
NOTE − The flue collar on all models is sized to accommo-
date 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 proper-
ly transition to the larger diameter flue pipe. This elbow
must be added to the elbow count used to determine ac-
ceptable 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.
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
Exhaust Pipe Offset
12" Min.
12" Min.
Upflow and Downflow Application
Rooftop Termination
Upflow and Downflow Application
Side Wall Termination
12" Min.
12" Min.
Horizontal Application
Rooftop Termination
Horizontal Application
Side Wall Termination
FIGURE 11
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Use the following steps to correctly size vent pipe diameter.
1 − Determine the vent termination and its corresponding
B−PVC Joint Cementing Procedure
All cementing of joints should be done according to the
specifications outlined in ASTM D 2855.
2 − Determine the number of 90° elbows required for both
indoor and outdoor (e.g. snow riser) use. Calculate the
corresponding equivalent feet of vent pipe.
3 − Determine the number of 45° elbows required for both
indoor and outdoor use. Calculate the corresponding
equivalent feet of vent pipe.
WARNING
DANGER OF EXPLOSION!
Fumes from PVC glue may ignite during system
check. Allow fumes to dissipate for at least 5 minutes
before placing unit into operation.
4 − Determine the length of straight pipe required.
5 − Add the total equivalent feet calculated in steps 1
through 4 and compare that length to the maximum
ameter. If the total equivalent length required exceeds
the maximum equivalent length listed in the appropri-
ate table, evaluate the next larger size pipe.
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.
TABLE 12
MINIMUM VENT PIPE LENGTHS
G61MP
MODEL
MIN. EQUIV.
VENT LENGTH
EXAMPLE
3 − Clean and dry surfaces to be joined.
045, 070,
090
5 ft. plus 2 elbows of 2", 2−1/2", 3"
or 4" diameter pipe
4 − Test fit joint and mark depth of fitting on outside of pipe.
5 ft. plus 2 elbows of 2−1/2" 3" or 4"
diameter pipe
110**
15 ft.*
5 − Uniformly apply liberal coat of PVC primer for PVC or
ABS cleaner for ABS to inside socket surface of fitting
and male end of pipe to depth of fitting socket.
5 ft. plus 2 elbows of 3" or 4"
diameter pipe
135***
*Any approved termination may be added to the minimum equivalent length
listed.
6 − Promptly apply solvent cement to end of pipe and in-
side socket surface of fitting. Cement should be ap-
plied lightly but uniformly to inside of socket. Take
care to keep excess cement out of socket. Apply sec-
ond coat to end of pipe.
**G61MP−48C−110 and G61MP−60C−110 must have 90° street ell (supplied)
installed directly into unit flue collar.
***G61MP−60D−135 must have 3" to 2" reducing ell (supplied) installed directly
into unit flue collar.
TABLE 13
MAXIMUM VENT PIPE LENGTHS
MAXIMUM EQUIVALENT VENT
G61MP
MODEL
NOTE − Time is critical at this stage. Do not allow prim-
er to dry before applying cement.
LENGTH FEET
ALTITUDE
2" dia. 2−1/2" dia. 3" dia. 4" dia.
045
070
59
59
65
65
42
32
n/a
65
65
42
32
n/a
65
65
42
32
n/a
77
78
234
214
204
179
160
234
214
204
179
160
234
214
204
179
160
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 as-
sembly (but not after pipe is fully inserted) to distribute
cement evenly.
0 − 4500
(0 − 1371 m)
090
26
72
110*
135**
045
n/a
n/a
59
72
***61
77
070
59
78
4501−7500
(1372−2286 m)
090
26
72
110*
135**
045
n/a
n/a
59
72
***46
77
NOTE − Assembly should be completed within 20 sec-
onds after last application of cement. Hammer blows
should not be used when inserting pipe.
070
59
78
7501 − 10000
(2287 − 3048 m)
090
26
72
110*
135**
n/a
n/a
72
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 indi-
cate a defective assembly due to insufficient solvent.
***46
n/a −− Not allowed.
*G61MP−48C−110 and G61MP−60C−110 must have 90° street ell (supplied)
installed directly into unit flue collar.
**G61MP−60D−135 must have 3" to 2" reducing ell (supplied) installed directly
into unit flue collar.
***90° elbows used in configuration of G61MP−60D−135 vent, must be lim-
ited to 3" sweep elbows.
9 − Handle joints carefully until completely set.
Page 18
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3. 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.
C− Venting Practices
The thickness of construction through which vent pipes
may be installed is 24" (610mm) maximum and 3" (76mm)
minimum. If a G61MP 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 prod-
ucts, the existing vent pipe is probably oversized for the
single water heater or other appliance. The vent should be
checked for proper draw with the remaining appliance.
4. Isolate piping at the point where it exits the outside wall
or roof in order to prevent transmission of vibration to
the structure.
5. 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 conden-
sate collection trap and lines.
Exhaust Piping
1. Use recommended piping materials for exhaust pip-
ing.
NOTE − A 2" diameter street ell is strapped to the blower
deck of 48C−110 and 60C−110 units. Street ell must be
2" reducing ell is strapped to the blower deck of the
60D−135 units. In upflow or downflow applications, the
reducing ell must be glued directly into the unit flue collar.
2. Secure all joints so that they are gas-tight using ap-
proved cement.
Suspend piping using hangers at a minimum of every 5
feet (1.52m) for schedule
1. Choose the appropriate side for venting in upflow or
downflow positions. Exhaust piping exits from the top
of the unit in horizontal air discharge applications.
Glue the field−provided exhaust vent pipe (or provided
street ell or reducing ell in upflow or downflow applica-
tions) to the flue collar. All cement joints should be
made according to the specifications outlined in ASTM
D 2855. Refer to pipe and fittings specifications and
gluing procedures.
40 PVC and every 3 feet
STRAPPING
(metal, plastic
or large wire
ties)
(.91m) for ABS−DWV, PVC−
DWV, SPR−21 PVC, and
SDR−26 PVC piping. A suit-
able hanger can be fabri-
cated by using metal or
FIGURE 12
plastic strapping or a large
wire tie.
TYPICAL EXHAUST PIPE CONNECTIONS AND CONDENSATE TRAP INSTALLATION
IN UPFLOW OR DOWNFLOW DIRECT OR NON-DIRECT VENT APPLICATIONS
(Right-Hand Exit in Upflow Application Shown)
2−1/2",
3", OR
4"
2”
PLUG
PLUG
G61MP−045, 070
or 090 with 2−1/2",
3", or 4" vent pipe
REDUCER
2”
2”
VENT PLUG
(Must be
glued in
2"
2”
4"
place)
2”
2−1/2",
3", OR
4"
REDUCER
(use only if
4" pipe is
PLUG
required)
REDUCER
2"***
CONDENSATE
TRAP
3"
(Must be installed
on same side as
exhaust piping)
2"*
3"**
G61MP−110 with
2−1/2", 3", OR 4"
vent pipe
G61MP−135 with
3" OR 4" vent pipe
*2" diameter street elbow provided.
**3" diameter reducing elbow provided.
***Limit pipe length to 2".
FIGURE 13
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TYPICAL EXHAUST PIPE CONNECTIONS
HORIZONTAL DIRECT OR NON-DIRECT VENT
APPLICATIONS
CAUTION
Do not discharge exhaust into an existing stack or
stack that also serves another gas appliance. If verti-
cal discharge through an existing unused stack is re-
quired, insert PVC pipe inside the stack until the end
is even with the top or outlet end of the metal stack.
(Horizontal Right-Hand Air
Discharge Application Shown)
*Limit pipe length to 2"
in G61MPV−110 and
−135 applications.
2−1/2",
3", OR
4"
G61MP−36B−045
G61MP−36B−070
G61MP−48C−090
G61MP−60C−090
G61MP−48C−110*
G61MP−60C−110*
G61MP−60C−135*
CAUTION
The exhaust vent pipe operates under positive pres-
sure and must be completely sealed to prevent leak-
age of combustion products into the living space.
REDUCER
2"*
2"
2"
Intake Piping
DO NOT transition from
smaller to larger pipe
size in horizontal runs.
G61MP−36B−045
G61MP−36B−070
G61MP−48C−090
G61MP−60C−090
The G61MP furnace may be installed in either direct vent
or non−direct vent applications. In non−direct vent applica-
tions, when intake air will be drawn into the furnace from the
surrounding space, the indoor air quality must be consid-
ered and guidelines listed in Combustion, Dilution and Ven-
tilation Air section must be followed.
2"
The G61MP unit is designed for either left−side or right−side
air intake connections in either upflow or downflow applica-
tions. In horizontal applications, air intake must be brought
in through the top. Intake air piping is independent of ex-
haust piping.
Follow the next four steps when installing the unit in direct
vent applications, where combustion air is taken from out-
doors and flue gases are discharged outdoors. The pro-
vided air intake screen must not be used in direct vent ap-
plications.
FIGURE 14
IMPORTANT
Exhaust piping and condensate trap must be
installed on the same side of the unit.
1 − Cement intake piping in slip connector located on the
side of the burner box.
2. All horizontal runs of exhaust pipe must slope back to-
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 ev-
ery 5 feet (1.52m) using hangers.
2 − Use a #7 sheet metal screw to secure the intake pipe to
the connector, if desired. A pilot indentation is provided in
the slip connector to assist in locating and starting the fas-
tener.
NOTE − Exhaust piping should be checked carefully to
make sure there are no sags or low spots.
3 − Glue the provided 2" plug into the unused air intake con-
nector on the opposite side of the cabinet.
3. On the opposite side of the cabinet, glue the provided
2" vent plug into the unused flue collar.
4 − Route piping to outside of structure. Continue with instal-
lation following instructions given in general guide lines for
piping terminations and in intake and exhaust piping ter-
pipe sizes.
4. Route piping to outside of structure. Continue with
installation following instructions given in piping ter-
mination section.
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TYPICAL AIR INTAKE PIPE CONNECTIONS
UPFLOW OR DOWNFLOW DIRECT VENT APPLICATIONS
(Right-Hand Exit in Upflow Application Shown)
2−1/2",
3" OR
4ꢁ
2−1/2",
3" OR
4ꢁ
REDUCER
2ꢁ
2ꢁ*
REDUCER
2"*
2ꢁ
2ꢁ
2ꢁ*
2ꢁ
PLUG
(Must be
glued in
place)
G61MP−36B−045
G61MP−36B−070
G61MP−48C−090
G61MP−60C−090
G61MP−36B−045
G61MP−36B−070
G61MP−48C−090
G61MP−60C−090
G61MP−48C−110*
G61MP−60C−110*
G61MP−36B−045
G61MP−36B−070
G61MP−48C−090
G61MP−60C−090
G61MP−48C−110*
G61MP−60C−110*
G61MP−60C−135*
*Limit pipe length to 2"
in G61MP−110 and
−135 applications.
FIGURE 15
Follow the next three steps when installing the unit in Non-
Direct Vent applications where combustion air is taken
from indoors and flue gases are discharged outdoors.
TYPICAL AIR INTAKE PIPE CONNECTIONS
HORIZONTAL DIRECT VENT APPLICATIONS
(Horizontal Right-Hand Air Discharge Application Shown)
G61MP−36B−045
G61MP−36B−070
TYPICAL AIR INTAKE PIPE CONNECTIONS
UPFLOW OR HORIZONTAL NON-DIRECT
VENT APPLICATIONS
2-1/2”,
*Limit pipe
length to 2" in
G51MP−110
and −135
G61MP−48C−090
G61MP−60C−090
G61MP−48C−110*
G61MP−60C−110*
G61MP−60C−135*
3” OR 4”
(Right-Hand Exit in Upflow Application Shown)
REDUCER
applications.
6 in. Max.
2”*
2-1/2”,
3” OR 4”
2”*
G61MP−36B−045
2”
G61MP−36B−070
G61MP−48C−090
G61MP−60C−090
G61MP−48C−110*
G61MP−60C−110*
PLUG
(Must be
glued in
INTAKE
place)
REDUCER
2”
DEBRIS
SCREEN
(Provided)
2”*
2”
G61MP−36B−045
G61MP−36B−070
G61MP−48C−090
G61MP−60C−090
2”
NOTE − Debris screen and elbow may be rotated, so that
screen may be positioned to face forward, backward or
downward.
FIGURE 17
FIGURE 16
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TYPICAL AIR INTAKE PIPE CONNECTIONS
DOWNFLOW NON-DIRECT VENT APPLICATIONS
(Right-Hand Exit in Downflow Applications Shown)
2" SWEEP
ELL
INTAKE
DEBRIS
SCREEN
(Provided)
6 in. Max.
PLUG
PLUG
(Must be
glued in
place)
(Must be
glued in
place)
2"
18 in.
2" SWEEP ELL
INTAKE DEBRIS
SCREEN
(Provided)
Downflow Additive Flloor Base
Downflow
Evaporator
Coil
NOTE − Debris screen and sweep ell may be rotated, so that
screen may be positioned to face forward, backward or to the side.
FIGURE 18
1 − Use field−provided materials and the factory−provided
air intake screen to route the intake piping as shown in
(76mm) around the air intake opening. The air intake
opening (with the protective screen) should always be
directed either downward or straight out. Use 2" pipe
and fittings only and make sure that the air intake does
not extend more than 6" beyond the G61MP cabinet.
The air intake connector must not be located near
the floor. To avoid this complication in downflow
applications which do not include a downflow
evaporator coil, the intake air routing should be modi-
Testing for Proper Venting and Sufficient Combustion Air
(Non−Direct Vent Applications Only)
WARNING
CARBON MONOXIDE POISONING HAZARD!
Failure to follow the steps outlined below for each
appliance connected to the venting system being
placed into operation could result in carbon monox-
ide poisoning or death.
The following steps shall be followed for each ap-
pliance connected to the venting system being
placed into operation, while all other appliances con-
nected to the venting system are not in operation.
2 − Use a #7 sheet metal screw to secure the intake pipe to
the connector, if desired. A pilot indentation is provided in
the slip connector to assist in locating and starting the fas-
tener.
After the G61MP gas furnace has been started, the follow-
ing test should be conducted to ensure proper venting and
sufficient combustion air has been provided to the G61MP,
as well as to other gas-fired appliances which are separate-
ly vented. The test should be conducted while all ap-
pliances (both in operation and those not in operation) are
connected to the venting system being tested. If the vent-
ing system has been installed improperly, or if provisions
have not been made for sufficient amounts of combustion
air, corrections must be made as outlined in the previous
section.
3 − Glue the provided 2" plug into the unused air intake con-
nector on the opposite side of the cabinet.
1 − Seal any unused openings in the venting system.
2 − Visually inspect the venting system for proper size and
horizontal pitch. Determine there is no blockage or re-
striction, leakage, corrosion, or other deficiencies
which could cause an unsafe condition.
Page 22
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3 − To the extent that it is practical, close all building doors
and windows and all doors between the space in which
the appliances connected to the venting system are lo-
cated and other spaces of the building.
from any obstructions and above the level of snow accu-
mulation (where applicable). The termination should be at
least 12 inches (305mm) from any opening through which
flue products could enter the building.
4 − Close fireplace dampers.
At vent termination, care must be taken to maintain
protective coatings over building materials (prolonged
exposure to exhaust condensate can destroy protective
coatings). It is recommended that the exhaust outlet not be
located within 6 feet (1.8m) of a condensing unit because
the condensate can damage the painted coating.
5 − Turn on clothes dryers and any appliances not con-
nected to the venting system. Turn on any exhaust
fans, such as range hoods and bathroom exhausts, so
they will operate at maximum speed. Do not operate a
summer exhaust fan.
6 − Follow the lighting instruction to place the appliance
being inspected into operation. Adjust thermostat so
appliance will operate continuously.
NOTE − If winter design temperature is below 32°F (0°C),
exhaust piping should be insulated with 1/2" (13mm), Ar-
maflex or equivalent when run through unheated space.
Do not leave any surface area of exhaust pipe open to out-
side air; exterior exhaust pipe should be insulated with 1/2"
(13mm) Armaflex or equivalent. In extreme cold climate
areas, 3/4" (19mm) Armaflex or equivalent may be neces-
sary. Insulation on outside runs of exhaust pipe must be
painted or wrapped to protect insulation from deterioration.
Exhaust pipe insulation may not be necessary in some
specific applications.
7 − Test for spillage of flue gases at the draft hood relief
opening after 5 minutes of main burner operation. Use
the flame of match or candle, or smoke from a ciga-
rette, cigar.
8 − If improper venting is observed during any of the
above tests, the venting system must be corrected or
sufficient combustion/make-up air must be provided.
The venting system should be re-sized to approach
the minimum size as determined by using the ap-
propriate tables in appendix G in the current standards
of the National Fuel Gas Code ANSI−Z223.1/NPFA 54
in the U.S.A., and the appropriate Natural Gas and
Propane appliances venting sizing tables in the cur-
rent standard of the CSA−B149 Natural Gas and Pro-
pane Installation Codes in Canada.
NOTE − During extremely cold temperatures, below
approximately 20°F (6.7°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 avail-
able from Lennox. See Condensate Piping section for part
numbers.
9 − After determining that each appliance remaining
connected to the common venting system properly
vents when tested as indicated in step 3, return
doors, windows, exhaust fans, fireplace dampers
and any other gas-burning appliance to their previous
condition of use.
General Guidelines for Vent Terminations for Non-Direct
Vent Installations.
IMPORTANT
Do not use screens or perforated metal in exhaust
terminations. Doing so will cause freeze−ups and
may block the terminations.
In Non-Direct Vent applications, combustion air is taken
from indoors and the flue gases are discharged to the out-
doors. The G61MP is then classified as a non-direct vent,
Category IV gas furnace. In Non-Direct Vent applications,
the vent termination is limited by local building codes. In
the absence of local codes, refer to the current National
Fuel Gas Code ANSI Z223−1/NFPA 54 in U.S.A., and cur-
rent CSA−B149 Natural Gas and Propane Installation
Codes in Canada for details.
IMPORTANT
For Canadian Installations Only:
In accordance to CSA International B149 installation
codes, the minimum allowed distance between the
combustion air intake inlet and the exhaust outlet of
other appliances shall not be less than 12 inches
(305mm).
Position termination end according to location given in fig-
Page 23
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VENT TERMINATION CLEARANCES
FOR INSTALLATIONS IN THE USA AND CANADA*
− G61MP VENT TERMINATION
− AIR INLET OF OTHER APPLIANCE
C
less than
10 ft (3.048M)
D
F
D
E
G
A − Clearance above grade − 12 in. (305mm) minimum.
E − Clearance to non−mechanical air supply inlet or outlet
for vent installations in USA − 48 in. (1219mm) minimum
horizontal and below, 12 in. (305mm) minimum above.
for vent installations in Canada − 12 in. (305mm) minimum
for appliances ꢀ 100,000 Btuh (30 kW);
B − Clearance to window or door that may be opened −
for vent installations in USA − 12 in. (305mm) minimum.
for vent installations in Canada − 12 in. (305mm) minimum
for appliances ꢀ 100,000 Btuh (30 kW);
36 in. (0.9m) minimum for appliances > 100,000 Btuh (30
kW).
36 in. (0.9m) minimum for appliances > 100,000 Btuh (30
kW).
F − Clearance to mechanical air supply inlet −−
for vent installations in USA − 36 in. minimum (914mm).
C − Do not position terminations directly under roof eaves.
D − Clearance to electric meters, gas meters, regulators, and
relief equipment −
G − Clearance to mechanical air supply inlet −−
for vent installations in Canada − 72 in. (1829mm) mini-
mum.
for vent installations in USA − 48 in (1219mm) minimum.
for vent installations in Canada − see current edition of CSA
B149 Code.
H − Do not point terminations into recessed areas such as win-
dow wells, stairwells or alcoves.
J − Do not position terminations directly above a walkway.
* Note −
(I) Dimensions are from the current edition of The National Fuel Gas Code − ANSI-Z223.1/NFPA 54 for USA installa-
tions. In Canada, refer to current edition of CSA B149 installation codes. Local codes or regulations may require dif-
ferent clearances.
(II) In Non-Direct Vent installations, combustion air is taken from indoors and the flue gases are discharged to the outdoors.
FIGURE 19
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Details of Intake and Exhaust Piping Terminations for
Direct Vent Installations
9. Based on the recommendation of the manufacturer, a
multiple furnace installation may use a group of up to
four termination kits WTK assembled together hori-
NOTE − In Direct Vent installations, combustion air is taken
from outdoors and flue gases are discharged to outdoors.
TABLE 14
EXHAUST PIPE TERMINATION SIZE REDUCTION
Intake and exhaust pipes may be routed either horizontally
through an outside wall or vertically through the roof. In at-
tic or closet installations, vertical termination through the
minations.
G61MP
MODEL
Exhaust Pipe Size
Termination Pipe Size
045 and 070
090
2", 2−1/2", 3" or 4"
2", 2−1/2", 3" or 4"
2−1/2", 3" or 4"
3" or 4"
1−1/2"
2"
1. 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.
110
2"*
135
2"*
*Approved 3" concentric termination kit terminates with 2−5/8" ID pipe.
3(76) MAX.
2. Intake and exhaust pipes should be placed as close
together as possible at termination end (refer to il-
lustrations). Maximum separation is 3" (76mm) on roof
terminations and 6" (152mm) on side wall termina-
tions.
SIZE TERMINATION
Inches(mm)
UNCONDITIONED
ATTIC SPACE
8" (203) MIN
1/2" (13) FOAM
INSULATION IN
UNCONDITIONED
SPACE
3. If necessary, install a field−provided reducer to adapt
larger vent pipe size to termination pipe size.
12" (305) ABOVE
AVERAGE SNOW
ACCUMULATION
4. On roof terminations, the intake piping should termi-
nate straight down using two 90° elbows (See figure
20).
3" (76) OR
2" (51) PVC
5. Exhaust piping must terminate straight out or up as
shown. In rooftop applications, a reducer may be re-
quired on the exhaust piping at the point where it exits
the structure to improve the velocity of exhaust away
from the intake piping. See table 14.
PROVIDE SUPPORT
FOR INTAKE AND
EXHAUST LINES
NOTE − Care must be taken to avoid recirculation of
exhaust back into intake pipe.
DIRECT VENT ROOF TERMINATION KIT
(15F75 or 44J41)
6. On field supplied terminations for side wall exits, ex-
haust piping should extend a minimum of 12 inches
(305mm) beyond the outside wall. Intake piping
FIGURE 20
12" (305) MAX.
(unless supported)
1/2" (13) ARMAFLEX
INSULATION IN
UNCONDITIONED SPACE
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 inches (203mm).
1/2" (13)
ARMAFLEX
INSULATION
FIELD−
PROVIDED
REDUCER MAY
BE REQUIRED
TO ADAPT
LARGER VENT
PIPE SIZE TO
TERMINATION
SIZE
8. If intake and exhaust piping must be run up a side wall
to position above snow accumulation or other obstruc-
tions, piping must be supported every 3 ft. (.9m) as
method. In addition, WTK wall termination kit must be
extended for use in this application. See figure 27.
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 5 feet (1.5m) to the equivalent length of the
pipe.
TERMINATION
PIPE PER
6" (152)
MAXIMUM
OUTSIDE
WALL
8" (203)
MINIMUM
2" (51) PVC
COUPLING
Inches (mm)
TOP VIEW WALL RING KIT
(15F74)
FIGURE 21
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EXHAUST VENT
EXHAUST
TERMINATION
12" (305) ABOVE
AVERAGE SNOW
ACCUMULATION
Inches (mm)
Front View
INTAKE
VENT
INTAKE
TERMINATION
1/2" (13) Foam Insulation
in Unconditioned Space
Side View
FIELD−PROVIDED
REDUCER MAY BE REQUIRED
TO ADAPT LARGER VENT
PIPE SIZE TO TERMINATION
FIELD−
PROVIDED
REDUCER MAY
BE REQUIRED
TO ADAPT
EXHAUST VENT
EXHAUST
INTAKE
LARGER VENT
PIPE SIZE TO
TERMINATION
DIRECT VENT CONCENTRIC ROOFTOP TERMINATION
(71M80, 69M29 or 60L46)
INTAKE VENT
OUTSIDE WALL
Inches (mm)
FIGURE 22
DIRECT VENT WALL TERMINATION KIT
(22G44, 44J40, 30G28 or 81J20)
INTAKE
Inches (mm)
TERMINATION
EXHAUST
TERMINATION
FIGURE 25
EXHAUST
12"
(305)
INTAKE
EXHAUST
VENT
12" (305) Min.
above grade.
5"
(127)
5−1/2"
(140)
FIELD−PROVIDED
REDUCER MAY
BE REQUIRED TO
ADAPT LARGER
VENT PIPE SIZE
TO TERMINATION
INTAKE
VENT
18" MAX.
(457)
Front View
EXHAUST VENT
DIRECT VENT CONCENTRIC WALL TERMINATION
(71M80, 69M29 or 60L46)
Inches (mm)
FIGURE 23
INTAKE
VENT
Side View
12" (305) MAX. for 2" (51)
(unless supported)
Inches(mm)
UNCONDITIONED
SPACE
OPTIONAL VENT TERMINATION FOR MULTIPLE UNIT
INSTALLATION OF DIRECT VENT WALL TERMINATION KIT WTK
8 (203)
MIN.
OUTSIDE WALL
FIGURE 26
SIZE
TERMINATION
PROVIDE SUPPORT
FOR INTAKE AND
PIPE PER
EXHAUST LINES EVERY
36" (914)
12" (305) ABOVE
FIELD−PROVIDED
AVERAGE SNOW
REDUCER MAY
ACCUMULATION
BE REQUIRED TO
ADAPT LARGER
VENT PIPE SIZE
TO TERMINATION
1/2" (13) FOAM
INSULATION IN
UNCONDITIONED
SPACE
1/2" (13) FOAM
INSULATION
SIDE VIEW
DIRECT VENT WALL RING TERMINATION
(15F74)
ment.
FIGURE 24
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12" (305) MAX. for 2" (51)
20" (508) MAX. for 3" (76)
(unless supported)
Inches (mm)
EXHAUST
AIR
COVER EXHAUST
VENT WITH
1/2" (13)
12"
(305)
FOAM
INSULATION
8" (203)
INTAKE
AIR
INTAKE
AIR
Minimum
EXHAUST
12" (305)
Minimum
ABOVE GRADE
AIR
12" MIN.
(305)
5"
(127)
Above Grade
5-1/2"
(140)
GRADE
Side View
GRADE
Front View
DIRECT VENT TERMINATION
WALL TERMINATION KIT (22G44, 44J40, 30G28 or 81J20) EXTENDED VENT FOR GRADE CLEARANCE
FIGURE 27
G61MP DIRECT VENT APPLICATION
USING EX
STRAIGHT−CUT OR
ANGLE−CUT IN DIRECTION
OF ROOF SLOPE *
Inches(mm)
SIZE TERMINATION
PIPE PER TABLE
14.
12" (305mm)
ABOVE AVE.
SNOW
ACCUMULATION
3" − 8"
(76mm−
8" − 12"
EXHAUST VENT
1/2" (13mm)
WEATHERPROOF
INSULATION
203mm)
(203mm − 305mm)
SHOULDER OF FITTINGS
PROVIDE SUPPORT
OF PIPE ON TOP PLATE
INTAKE PIPE
INSULATION (optional)
3" (76) OR
2" (51) PVC
SHEET
METAL TOP
PLATE
UNCONDITIONED
ATTIC SPACE
ALTERNATE
INTAKE PIPE
PROVIDE SUPPORT
FOR EXHAUST LINES
MINIMUM 12"
(305mm) ABOVE
ROOF
3" − 8"
(76mm−
203mm)
INSULATE
TO FORM
SEAL
EXTERIOR
PORTION OF
CHIMNEY
*SIZE TERMINATION
NON−DIRECT VENT ROOF TERMINATION KIT
(15F75 or 44J41)
FIGURE 29
NOTE − Do not discharge exhaust gases directly into any chimney or vent stack. If ver-
tical 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 illus-
trated. In any exterior portion of chimney, the exhaust vent must be insulated.
FIGURE 28
Details of Exhaust Piping Terminations for Non-Direct
Vent Applications
12" (305) Max. for 2" (51)
Unless Supported
1/2" (13) ARMAFLEX
INSULATION IN
UNCONDITIONED SPACE
Exhaust pipes may be routed either horizontally through an
outside wall or vertically through the roof. In attic or closet
installations, vertical termination through the roof is pre-
1/2" (13)
ARMAFLEX
INSULATION
FIELD−PROVIDED
REDUCER MAY
BE REQUIRED TO
ADAPT LARGER
VENT PIPE SIZE
TO TERMINATION
1. Exhaust piping must terminate straight out or up as
shown. The termination pipe must be sized as listed in
locity required to move the exhaust gases away from
the building.
PVC REDUCER
SIZE TERMINATION
Inches (mm)
TOP VIEW
NON−DIRECT VENT WALL RING KIT
(15F74)
2. On field supplied terminations for side wall exits, ex-
haust piping should extend a maximum of 12 inches
(305mm) beyond the outside wall, unless support is
FIGURE 30
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3. If exhaust piping must be run up a side wall to position
above snow accumulation or other obstructions, pip-
ing must be supported every 3 feet (.9m) as shown in
When exhaust piping must be run up an outside wall,
any reduction in exhaust pipe size must be done after
the final elbow.
CONDENSATE TRAP LOCATIONS
(Unit shown in upflow position)
Horizontal
left and
Horizontal
right and
optional
optional
downflow
downflow
12" (305) Max. for 2" (51)
Unless Supported
Inches(mm)
UNCONDITIONED
SPACE
OUTSIDE WALL
SIZE TER-
MINATION
PIPE PER
Optional
upflow
Optional
upflow
PROVIDE SUPPORT
FOR EXHAUST LINES
EVERY 36" (914)
12" (305) ABOVE
AVERAGE SNOW
ACCUMULATION
FIELD−PROVIDED
REDUCER MAY BE
REQUIRED TO
ADAPT LARGER
VENT PIPE SIZE TO
TERMINATION
FIGURE 33
1/2" (13) FOAM
1 − Determine which side condensate piping will exit the
unit. Remove plugs from the condensate collar at the
appropriate location on the side of the unit.
INSULATION IN
UNCONDITIONED
SPACE
1/2" (13) FOAM
INSULATION
SIDE VIEW
NON−DIRECT VENT WALL RING TERMINATION
(15F74)
NOTE − The condensate trap is factory−shipped with
two rubber O−rings and two rubber clean−out caps
installed. Check to make sure that these items are in
place before installing the trap assembly.
FIGURE 31
G61MP NON−DIRECT VENT APPLICATION
USING EXISTING CHIMNEY
2 − Install condensate trap onto the condensate collar.
Use provided HI/LO screws to secure two upper
flanges of the trap to the collar. Use provided sheet
metal screw to secure bottom trap flange to side of
STRAIGHT−CUT OR
ANGLE−CUT IN DIRECTION
OF ROOF SLOPE
SIZE TERMINATION
3" − 8"
(76mm−
203mm)
EXHAUST VENT
1/2" (13mm)
WEATHERPROOF
INSULATION
NOTE − In upflow and downflow applications, con-
densate trap must be installed on the same side as
exhaust piping.
MINIMUM12"
(305mm) ABOVE
AVERAGE SNOW
ACCUMULATION
SHOULDER OF FITTINGS
PROVIDE SUPPORT
OF PIPE ON TOP PLATE
SHEET
METAL TOP
PLATE
CAUTION
DO NOT use a power driver to tighten screws which
secure condensate trap to cabinet. Screws should
be hand−tightened using a screw driver to avoid the
possibility of damage to the trap assembly.
3" − 8"
(76mm−
203mm)
INSULATE
TO FORM
SEAL
EXTERIOR
PORTION OF
CHIMNEY
3 − Glue the field−provided coupling or pipe to the trap.
Install a tee and vent pipe near the trap.
NOTE − The condensate trap drain stubs (both sides)
have an outer diameter which will accept a standard
3/4" PVC coupling. The inner diameter of each stub
will accept standard 1/2" diameter PVC pipe.
NOTE − Do not discharge exhaust gases directly into any chimney or vent stack. If ver-
tical 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 illus-
trated. In any exterior portion of chimney, the exhaust vent must be insulated.
FIGURE 32
NOTE − Vinyl tubing may be used for condensate
drain. Tubing must be 1−1/4" OD X 1" ID and should be
attached to the drain stubs on the trap using a hose
clamp.
Condensate Piping
This unit is designed for either right- or left-side exit of con-
densate piping in either upflow or downflow applications;
however, it must be installed on the same side of the unit as
the exhaust piping. In horizontal applications, the conden-
sate trap should extend below the unit. A 5−1/2" service
clearance is required for the condensate trap. Refer to fig-
ure for condensate trap locations.
4 − Glue the field−provided drain line to the tee. Route the
drain line to an open drain. As an alternate, clear vinyl
tubing may be used to drain condensate away from
the trap. Secure the vinyl tubing to the drain stubs on
the trap using a hose clamp. Do not overtighten the
Page 28
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hose clamp.
5 − If unit will be started immediately upon completion of
installation, prime trap per procedure outlined in Unit
Start−Up section.
Condensate line must be sloped downward away from
condensate trap to drain. If drain level is above con-
densate trap, condensate pump must be used. Con-
densate drain line should be routed within the condi-
tioned space to avoid freezing of condensate and
blockage of drain line. If this is not possible, a heat
cable kit may be used on the condensate trap and line.
Heating cable kit is available from Lennox in various
lengths; 6 ft. (1.8m) − kit no. 18K48; 24 ft. (7.3m) − kit
no. 18K49; and 50 ft. (15.2m) − kit no. 18K50.
6 − Glue the provided cap onto the unused condensate
drain line stub.
CONDENSATE ASSEMBLY
HI/LO SCREWS
(DO NOT use power
driver. Hand−tighten
using screw driver.)
VENT
NIPPLE
O−RINGS
CAUTION
Do not use copper tubing or existing copper
condensate lines for drain line.
TEE
CAP
NIPPLE
COUPLING
CLEAN−OUT ACCESS
(both sides)
CONDENSATE TRAP
SCREW
FIGURE 34
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III−START-UP
WARNING
If you do not follow these instructions exactly, a fire
or explosion may result causing property damage,
personal injury or death.
A−Preliminary and Seasonal Checks
1 − Inspect electrical wiring, both field and factory installed
for loose connections. Tighten as required.
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.
B−Heating Start-Up
FOR YOUR SAFETY READ BEFORE OPERATING
1 − STOP! Read the safety information at the beginning of
this section.
WARNING
Shock and burn hazard.
2 − Set the thermostat to the lowest setting.
3 − Turn off all electrical power to the unit.
G61MP units are equipped with a hot surface igni-
tion system. Do not attempt to light manually.
4 − This furnace is equipped with an ignition device which
automatically lights the burners. Do not try to light the
burners by hand.
BEFORE LIGHTING the unit, smell all around the fur-
nace area for gas. Be sure to smell next to the floor be-
cause some gas is heavier than air and will settle on the
floor.
5 − Remove the upper access panel.
The gas valve on the G61MP may be equipped with ei-
ther a gas control knob or gas control lever. Use only your
hand to push the lever or turn the gas control knob. Never
use tools. If the the lever will not move or the knob will not
push in or turn by hand, do not try to repair it. Force or at-
tempted repair may result in a fire or explosion.
6 − Honeywell VR8205 Gas Valve − Turn knob on gas
valve clockwise
35.
to OFF. Do not force. See figure
White Rodgers 36E Gas Valve − Switch gas valve le-
valve.
Placing the furnace into operation:
®
G61MP units are equipped with a SureLight ignition
system. Do not attempt to manually light burners on this
furnace. Each time the thermostat calls for heat, the
burners will automatically light. The ignitor does not get
7 − Wait five 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 instruc-
tions. If you do not smell gas go to next step.
®
hot when there is no call for heat on units with SureLight
ignition system.
Priming Condensate Trap
The condensate trap should be primed with water prior to
start−up to ensure proper condensate drainage. Either
pour 10 fl. oz. (300 ml) of water into the trap, or follow
these steps to prime the trap:
HONEYWELL VR8205 Series Gas Valve
REFERENCE TO
BURNER BOX
hose barb in place of cap
1 − Follow the lighting instructions to place the unit into op-
eration.
MANIFOLD
PRESSURE
TAP
HIGH FIRE
ADJUSTMENT
SCREW
2 − Set the thermostat to initiate a heating demand.
(under cap)
3 − Allow the burners to fire for approximately 3 minutes.
4 − Adjust the thermostat to deactivate the heating de-
mand.
5 − Wait for the combustion air inducer to stop. Set the
thermostat to initiate a heating demand and again al-
low the burners to fire for approximately 3 minutes.
lOW FIRE
ADJUSTMENT
SCREW
(under cap)
6 − Adjust the thermostat to deactivate the heating de-
mand and again wait for the combustion air inducer to
stop. At this point, the trap should be primed with suffi-
cient water to ensure proper condensate drain opera-
tion.
iNLET PRESSURE TAP
GAS VALVE SHOWN IN OFF POSITION
FIGURE 35
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IV−HEATING SYSTEM SERVICE CHECKS
A−C.S.A. Certification
All units are C.S.A. (formally A.G.A. and C.G.A. combined)
design certified without modifications. Refer to the G61MP
Installation Instruction.
WHITE RODGERS 36E SERIES GAS VALVE
HIGH FIRE
MANIFOLD
PRESSURE
ADJUSTMENT
ON SIDE
B−Gas Piping
(under cap)
MANIFOLD
PRESSURE
TAP ON SIDE
CAUTION
If a flexible gas connector is required or allowed by
the authority that has jurisdiction, black iron pipe
shall be installed at the gas valve and extend outside
the furnace cabinet.
LOW FIRE MANIFOLD
PRESSURE ADJUSTMENT
ON SIDE (under cap)
INLET PRESSURE
TAP ON SIDE
GAS VALVE SHOWN IN OFF POSITION
FIGURE 36
WARNING
Do not exceed 600 in−lbs (50 ft−lbs) torque when
attaching the gas piping to the gas valve.
8 − Honeywell VR8205 Gas Valve − Turn knob on gas
valve counterclockwise
to ON. Do not force.
White Rodgers 36E Gas Valve − Switch gas valve lever
valve.
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.
9 − Replace the upper access panel.
10− Turn on all electrical power to to the unit.
11− Set the thermostat to desired setting.
Compounds used on gas piping threaded joints should be
resistant to action of liquefied petroleum gases.
NOTE − When unit is initially started, steps 1 through 11
may need to be repeated to purge air from gas line.
C−Testing Gas Piping
12− If the appliance will not operate, follow the instructions
ꢁTurning Off Gas to Unit" and call your service techni-
cian or gas supplier.
IMPORTANT
In case emergency shutdown is required, turn off
the main shut-off valve and disconnect the main
power to unit. These controls should be properly
labeled by the installer.
Turning Off Gas to Unit
1 − Set the thermostat to the lowest setting.
2 − Turn off all electrical power to the unit if service is to be
performed.
When pressure testing gas lines, the gas valve must be dis-
connected and isolated. Gas valves can be damaged if
3 − Remove the upper access panel.
4 − Honeywell VR8205 Gas Valve − Turn knob on gas
valve clockwise to OFF. Do not force.
White Rodgers 36E Gas Valve −Switch gas valve le-
ver to OFF.
GAS PIPING TEST PROCEDURE
MANUAL MAIN SHUT−OFF VALVE
5 − Replace the upper access panel.
C−Safety or Emergency Shutdown
Turn off unit power. Close manual and main gas valves.
D−Extended Period Shutdown
CAP
Turn off thermostat or set to ꢁUNOCCUPIED" mode. Close
all gas valves (both internal and external to unit) to guaran-
tee no gas leak into combustion chamber. Turn off power to
unit. All access panels and covers must be in place and se-
cured.
GAS VALVE
FIGURE 37
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When checking piping connections for gas leaks, use pre-
ferred means. Kitchen detergents can cause harmful corro-
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.
5 − After allowing unit to stabilize for 5 minutes, record
manifold pressure and compare to value given in table
19.
6 − Repeat steps 3, 4 and 5 on high heat.
NOTE − Shut unit off and remove manometer as soon as an
accurate reading has been obtained. Take care to replace
pressure tap plug.
Do not use matches, candles, flame or any other source of
ignition to check for gas leaks.
NOTE − During this test procedure, the unit will be overfir-
ing:
D−Testing Gas Supply Pressure
D Operate unit only long enough to obtain accurate read-
ing to prevent overheating heat exchanger.
When testing supply gas pressure, connect test gauge to
36. Check gas line pressure with unit firing at maximum
rate. Low pressure may result in erratic operation or under-
fire. High pressure can result in permanent damage to gas
gas connection (line).
D Attempts to clock gas meter during this procedure will
be inaccurate. Measure gas flow rate only during nor-
mal unit operation.
7 − When test is complete remove obstruction from hose
and return hose to gas valve barbed fitting.
On multiple unit installations, each unit should be checked
separately, with and without units operating. Supply pres-
TABLE 15
F− Proper Gas Flow (Approximate)
Furnace should operate at least 5 minutes before check-
ing gas flow. Determine time in seconds for two revolu-
tions of gas through the meter. (Two revolutions assures a
more accurate time.) Divide by two and compare to time
and rate is incorrect, check gas orifices for proper size and
restriction.
All G61MP Units
Natural
LP
Line Pressure WC"
4.5 − 10.5
11.0 − 13.0
E−Check Manifold Pressure
After line pressure has been checked and adjusted, check
manifold pressure. Move pressure gauge to outlet pres-
sure tap located on unit gas valve (GV1). Checks of man-
ifold pressure are made as verification of proper regulator ad-
justment. Manifold pressure for the G61MP can be measured
at any time the gas valve is open and is supplying gas to the
NOTE− To obtain accurate reading, shut off all other gas
appliances connected to meter.
TABLE 16
GAS METER CLOCKING CHART
Seconds for One Revolution
Natural
1 cu ft
Dial
82
LP
G61MP
Unit
2 cu ft
Dial
164
110
82
1 cu ft
Dial
205
136
102
82
2 cu ft
DIAL
410
−45
−70
IMPORTANT
For safety, connect a shut-off valve between the
manometer and the gas tap to permit shut off of
gas pressure to the manometer.
55
272
−90
41
204
−110
−135
33
66
164
27
54
68
136
Natural−1000 btu/cu ft
LP−2500 btu/cu ft
The gas valve is factory set and should not require adjust-
ment. All gas valves are factory regulated sensing atmo-
spheric pressure.
IMPORTANT
Manifold Pressure Measurement & Adjustment
For safety, shut unit off and remove manometer as
soon as an accurate reading has been obtained.
Take care to replace pressure tap plug.
NOTE − Pressure test adapter kit (10L34) is available from
Lennox to facilitate manifold pressure measurement.
1 − Connect test gauge to outlet tap on gas valve.
G− Proper Combustion
2 − Disconnect pressure sensing hose from gas valve.
3 − Start unit on low heat and allow 5 minutes for unit to
reach steady state.
Furnace should operate minimum 15 minutes with correct
manifold pressure and gas flow rate before checking com-
beyond the flue outlet and compare to the tables below.
The maximum carbon monoxide reading should not ex-
ceed 100 ppm.
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.
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TABLE 17
High Heat
CO %
H− High Altitude
NOTE − In Canada, certification for installations at eleva-
tions over 4500 feet (1372 m) is the jurisdiction of local au-
thorities.
Unit
CO %
For L.P.
2
For Nat
2
G61MP−36B−045
G61MP−36B−070
G61MP−48C−090
G61MP−60C−090
G61MP−48C−110
G61MP−60C−110
G61MP−60D−135
6.5 − 7.5
7.4 − 8.4
6.5 − 7.5
6.9 − 7.9
6.9 − 7.9
7.2 − 8.2
7.2 − 8.2
7.4 − 8.4
7.4 − 8.4
7.8 − 8.8
7.8 − 8.8
8.1 − 9.1
8.1 − 9.1
8.3 − 9.3
The manifold pressure may require adjustment to ensure
proper manifold pressure settings at varying altitudes and
required pressure switch changes and conversion kits at
varying altitudes.
The combustion air pressure switches are factory−set and
require no adjustment.
NOTE − A natural to L.P. propane gas changeover kit is nec-
essary to convert this unit. Refer to the changeover kit
installation instruction for the conversion procedure.
TABLE 18
Low Heat
CO %
Unit
CO %
For L.P.
2
For Nat
2
I− Condensate pH Range
G61MP−36B−045
G61MP−36B−070
G61MP−48C−090
G61MP−60C−090
G61MP−48C−110
G61MP−60C−110
G61MP−60D−135
4.8 − 5.8
5.3 − 6.3
5.3 − 6.3
5.9 − 6.9
5.9 − 6.9
6.1 − 7.1
6.1 − 7.1
6.7 − 7.7
The condensate is mildly acidic and can be measured with
pH indicators. The pH scale is a measurement of acidity
and alkalinity. The following scale shows the relative pH of
some common liquids as compared with condensate of
G61MP units. The concentration of the acidity of all these
fluids including the condensate is very low and harmless.
4.8 − 5.8
5.1 − 6.1
5.1 − 6.1
5.3 − 6.3
5.3 − 6.3
5.7 − 6.7
pH RANGE
0
1
2
3
4
5
Vinegar
Wine
Orange Juice
Tomato Juice
Increasing
Acidity
G61 Condensate
pH Range
6
7
Tap Water
8
Increasing
Alkalinity
9
10
11
TABLE 19
Conversion Kit Requirements and Manifold Pressures
Manifold Pressure at all
altitudes
Altitude
0−4500 ft.
(0−1372 m)
4501−7500 ft.
(1373−2286 m)
7501−10,000
(2287−3048 m)
Model
Input
Size
Low Fire
High Fire
Gas
Required
Conversion
Kit
Required
Conversion
Kit
Required
Conversion
Kit
Pressure
Switch
Pressure
Switch
Pressure
Switch
in.
w.c.
in.
kPa
kPa
w.c.
Nat
N/A
No Change
N/A
No Change
59M16
No Change
1.7
0.42
3.5
0.87
−045
−070
−090
−110
−135
LPG
Nat
59M13
N/A
No Change
No Change
59M13
N/A
No Change
No Change
59M14
59M16
No Change
56M06
4.9
1.7
1.22 10.0
0.42 3.5
2.5
0.87
LPG
Nat
59M13
N/A
No Change
No Change
59M13
N/A
No Change
75M22
59M14
59M16
56M06
56M21
4.9
1.7
1.22 10.0
0.42 3.5
2.5
0.87
LPG
Nat
59M13
N/A
No Change
No Change
59M13
N/A
75M22
59M14
59M16
56M21
4.9
1.7
1.22 10.0
0.42 3.5
2.5
No Change
No Change
0.87
LPG
Nat
59M13
N/A
No Change
No Change
59M13
N/A
No Change
59M93
59M14
59M16
No Change
56M93
4.9
1.7
1.22 10.0
0.42 3.5
2.5
0.87
LPG
59M13
No Change
59M13
59M93
59M14
56M93
4.9
1.22 10.0
2.5
Pressure switch is factory set. No adjustment necessary. All models use the factory installed pressure switch from 0−4500 feet (0−1370 m).
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J−Flame Signal
V−TYPICAL OPERATING CHARACTERISTICS
A−Blower Operation and Adjustment
1 − Blower operation is dependent on thermostat control
system.
A microamp DC meter is needed to check the flame signal
on the ignition control.
Flame (microamp) signal is an electrical current which passes
from the furnace control through the sensor during unit opera-
tion. Current passes from the sensor through the flame to
ground to complete a safety circuit.
2 − Generally, blower operation is set at thermostat sub-
base fan switch. With fan switch in ON position, blower
operates continuously. With fan switch in AUTO position,
blower cycles with demand or runs continuously while
heating or cooling circuit cycles.
To Measure Flame Signal − Ignition Control:
A
transducer
(Part
3 − Depending on the type of indoor thermostat, blower
and entire unit will be off when the system switch is in
OFF position.
TRANSDUCER
(PART #78H5401)
#78H5401 available from
Lennox Repair Parts) is
required to measure flame
signal if meter used will not
read a low micro amp sig-
transducer converts mi-
B−Temperature Rise
Temperature rise for G61MP 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 ꢁTEMP. RISE °F"
listed on the unit rating plate.
FIGURE 38
croamps to volts on a 1:1 conversion. Flame signal for the
SureLight control should read 0.23 or greater microamps with
a lockout signal of 0.16 microamps. A digital readout meter
must be used. The transducer plugs into most meters.
To Measure Temperature Rise:
1 − Place plenum thermometers in the supply and return air
plenums. Locate supply air thermometer in the first hori-
zontal run of the plenum where it will not pick up radiant
heat from the heat exchanger.
1 − Set the volt meter to the DC voltage scale. Insert
transducer into the VDC and common inputs. Ob-
serve correct polarities. Failure to do so results in
negative (−) values.
2 − Set thermostat to highest setting.
3 − After plenum thermometers have reached their high-
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, in-
crease blower speed to reduce temperature. To
change blower speed taps see the Blower Speed Taps
section in this manual.
2 − Turn off supply voltage to control.
3 − Disconnect ignition control flame sensor wire from the
flame sensor.
4 − Connect (−) lead of the transducer to flame sensor.
5 − Connect (+) lead of transducer to the ignition control sen-
sor wire.
6 − Turn supply voltage on and close thermostat contacts to
cycle system.
C−External Static Pressure
1 − Tap locations shown in figure 40.
7 − When main burners are in operation for two minutes, take
reading. Remember 1 DC volt = 1 DC microamp.
2 − Punch a 1/4" diameter hole
STATIC PRESSURE TEST
in supply and return air ple-
nums. Insert manometer
hose flush with inside edge
of hole or insulation. Seal
around the hose with perma-
gum. Connect the zero end
NOTE−MUST USE DIGITAL METER
SET DIAL TO MEASURE
VDC
of the manometer to the dis-
FIGURE 40
charge (supply) side of the system. On ducted sys-
tems, 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 at-
mosphere.
RED COLLAR
(+)
INDICATES
POSITIVE
LEAD
(−)
(−) TO
FLAME SENSOR
3 − With only the blower motor running and the evaporator
coil dry, observe the manometer reading. Adjust blow-
er motor speed to deliver the air desired according to
the job requirements.
(+) TO
IGNITION
CONTROL
SENSOR
WIRE
4 − External static pressure drop must not be more than
0.8" W.C.
FIGURE 39
5 − Seal around the hole when the check is complete.
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Filters
D−Blower Speed Taps
Blower speed tap changes are made on the SureLight con-
on dummy terminals "PARK " on the SureLight board. The
high heating tap is connected to the "HI HEAT " terminal
and the low heating / continuous blower tap is connected to
the "LO HEAT" terminal. The cooling tap is connected to the
ꢁCOOL" tap.
To change existing heat tap, turn off power then switch out
speed tap on "HI HEAT" or ꢁLO HEAT" with tap connected
each speed.
Filters should be inspected monthly. Clean or replace the
filters when necessary to ensure proper furnace opera-
tion. Replacement filters must be rated for high velocity
TABLE 21
Filter Size
Furnace
Cabinet Size
Side Return
Bottom Return
16 X 25 X 1 (1)
20 X 25 X 1 (1)
24 X 25 X 1 (1)
17−1/2"
21"
24−1/2"
16 X 25 X 1 (1)
16 X 25 X 1 (1)
16 X 25 X 1 (2)
Exhaust and air intake pipes
TABLE 20
Check the exhaust and air intake pipes and all connections
for tightness and to make sure there is no blockage.
Electrical
1 − Check all wiring for loose connections.
2 − Check for the correct voltage at the furnace (furnace
operating).
3 − Check amp−draw on the blower motor.
Motor Nameplate__________Actual__________
Winterizing and Condensate Trap Care
1 − Turn off power to the unit.
2 − Have a shallow pan ready to empty condensate water.
VI−MAINTENANCE
3 − Remove the drain plug from the condensate trap and
empty water. Inspect the trap then reinstall the drain
plug.
Cleaning Heat Exchanger
WARNING
ELECTRICAL SHOCK, FIRE,
OR EXPLOSION HAZARD.
If cleaning the heat exchanger becomes necessary, follow
the below procedures and refer to figure 1 when disassem-
bling unit. Use papers or protective covering in front of fur-
nace while removing heat exchanger assembly.
Failure to follow safety warnings exactly could result
in dangerous operation, serious injury, death or
property damage.
Improper servicing could result in dangerous opera-
tion, serious injury, death, or property damage.
Before servicing, disconnect all electrical power to
furnace.
When servicing controls, label all wires prior to dis-
connecting. Take care to reconnect wires correctly.
Verify proper operation after servicing.
IMPORTANT
Safety glasses and surgical mask should be worn
when cleaning heat exchanger and or burner
assembly.
1 − Turn off electrical and gas supplies to the furnace.
2 − Remove the upper and lower furnace access panels.
At the beginning of each heating season, system should be
checked as follows by a qualified service technician:
3 − Mark all gas valve wires and disconnect them from
valve.
Blower
4 − Remove gas supply line connected to gas valve. Re-
move gas valve/manifold assembly.
Check the blower wheel for debris and clean if necessary.
The blower motors are prelubricated for extended bearing
life. No further lubrication is needed.
5 − Remove sensor wire from sensor. Disconnect 2-pin
plug from the ignitor.
6 − Disconnect wires from flame roll−out switches.
7 − Remove burner box cover and remove four burner box
screws at the vestibule panel and remove burner box.
Set burner box assembly aside. G61MP−135 only −
Remove and discard two additional shipping screws.
WARNING
The blower access panel must be securely in place
when the blower and burners are operating. Gas
fumes, which could contain carbon monoxide, can
be drawn into living space resulting in personal inju-
ry or death.
NOTE − If necessary, clean burners at this time. Follow
procedures outlined in Burner Cleaning section.
8 − Loosen three clamps and remove flexible exhaust tee.
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20 − Back wash heat exchanger with soapy water solution
or steam. If steam is used it must be below 275°F
(135°C) .
G61MP−135 ONLY
21 − Thoroughly rinse and drain the heat exchanger. Soap
solutions can be corrosive. Take care to rinse entire
assembly.
Remove and discard two shipping screws.
22 − Reinstall heat exchanger into cabinet making sure that
the clamshells of the heat exchanger assembly are
resting on the support located at the rear of the cabi-
net. Remove the indoor blower to view this area
through the blower opening.
23 − Re-secure the supporting screws along the vestibule
sides and bottom to the cabinet.
24 − Reinstall cabinet screws on front flange at blower
deck.
25 − Reinstall the primary limit on the vestibule panel.
26 − Route heating component wiring through hole in blow-
er deck and reinsert strain relief bushing.
FIGURE 41
27 − Reinstall electrical junction box.
9 − Remove 3/8 inch rubber cap from condensate drain
plug and drain. Replace cap after draining.
28 − Reinstall the combustion air inducer. Reconnect the
3−pin plug to the wire harness. Reconnect the two
wires to the backup secondary limit, if applicable.
10 − Disconnect condensate drain line from the conden-
sate trap. Remove condensate trap (it may be neces-
sary to cut drain pipe). Remove screws that secure
condensate collars to either side of the furnace and re-
move collars. Remove drain tubes from cold end
header collector box.
29 − Reinstall pressure switches and reconnect pressure
switch wiring.
30 − Carefully connect combustion air pressure switch
hosing from pressure switches to proper stubs on
cold end header collector box.
11 − Disconnect condensate drain tubing from flue collar.
Remove screws that secure both flue collars into
place. Remove flue collars. It may be necessary to cut
the exiting exhaust pipe for removal of the fittings.
31 − Reinstall condensate collars on each side of the fur-
nace. Reconnect drain tubing to collector box.
32 − Reinstall condensate trap on same side as exhaust
pipe. Reconnect condensate drain line to the conden-
sate trap.
12 − Mark and disconnect all combustion air pressure tub-
ing from cold end header collector box.
33 − Use securing screws to reinstall flue collars to either
side of the furnace. Reconnect exhaust piping and ex-
haust drain tubing.
13 − Mark and remove wires from pressure switches. Re-
move pressure switches. Keep tubing attached to
pressure switches.
34 − Replace flexible exhaust tee on combustion air induc-
er and flue collars. Secure using three existing hose
clamps.
14 − Disconnect the 3-pin plug from the combustion air in-
ducer. Disconnect the two wires to the backup secon-
dary limit, if applicable. Remove four screws which se-
cure combustion air inducer to collector box. Remove
combustion air inducer assembly. Remove ground
wire from vest panel.
35 − Reinstall burner box assembly in vestibule area.
36 − Reconnect flame roll−out switch wires.
37 − Reconnect sensor wire and reconnect 2−pin plug from
ignitor.
15 − Remove electrical junction box from the side of the fur-
nace.
38 − Secure burner box assembly to vestibule panel using
four existing screws. Make sure burners line up in
center of burner ports.
16 − Mark and disconnect any remaining wiring to heating
compartment components. Disengage strain relief
bushing and pull wiring and bushing through the hole in
the blower deck.
39 − Reinstall gas valve manifold assembly. Reconnect
gas supply line to gas valve.
40 − Reinstall burner box cover.
17 − Remove the primary limit from the vestibule panel.
41 − Reconnect wires to gas valve.
18 − Remove two screws from the front cabinet flange at
the blower deck. Spread cabinet sides slightly to allow
clearance for removal of heat exchanger.
42 − Replace the blower compartment access panel.
43 − Refer to instruction on verifying gas and electrical con-
nections when re−establishing supplies.
19 − Remove screws along vestibule sides and bottom
which secure vestibule panel and heat exchanger as-
sembly to cabinet. Remove two screws from blower
rail which secure bottom heat exchanger flange. Re-
move heat exchanger from furnace cabinet.
44 − Follow lighting instructions to light and operate fur-
nace for 5 minutes to ensure that heat exchanger is
clean and dry and that furnace is operating properly.
45 − Replace heating compartment access panel.
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Cleaning the Burner Assembly
1 − Turn off electrical and gas power supplies to furnace.
Remove upper and lower furnace access panels.
7 − Reconnect the sensor wire and reconnect the 2−pin
plug to the ignitor wiring harness.
8 − Reinstall the burner box assembly using the existing
four screws. Make sure that the burners line up in the
center of the burner ports.
2 − Mark all gas valve wires and disconnect them from the
valve.
3 − Disconnect the gas supply line from the gas valve. Re-
move gas valve/manifold assembly.
9 − Reinstall the gas valve manifold assembly. Reconnect
the gas supply line to the gas valve. Reinstall the burn-
er box cover.
4 − Mark and disconnect sensor wire from the sensor. Dis-
connect 2-pin plug from the ignitor at the burner box.
10 − Reconnect the gas valve wires to the gas valve.
11 − Replace the blower compartment access panel.
5 − Remove burner box cover and remove four screws
which secure burner box assembly to vest panel. Re-
move burner box from the unit. G61MP−135 only − Re-
move and discard two additional shipping screws.
12 − Refer to instruction on verifying gas and electrical con-
nections when re−establishing supplies.
13 − Follow lighting instructions to light and operate fur-
nace for 5 minutes to ensure that heat exchanger is
clean and dry and that furnace is operating properly.
6 − Use the soft brush attachment on a vacuum cleaner to
gently clean the face of the burners. Visually inspect
the inside of the burners and crossovers for any block-
age caused by foreign matter. Remove any blockage.
14 − Replace heating compartment access panel.
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VII− Wiring and Sequence of Operation
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Single−Stage Thermostat, Two Stage Heat. Jumper
E20 set at ꢁSINGLE"
Sequence of Operation
Sequence depends on type thermostat used. G61MP
units are applicable for single stage or two stage ther-
mostats. Both type thermostats are described below.
Thermostat jumper E20 dictates which mode unit will
operate in. See flow chart for more sequence detail.
SureLight Control Self Check
1− SureLight control energizes combustion air inducer B6
on low heat speed. Combustion air inducer runs until
S128 low heat prove switch contacts close (switch
must close within 2 1/2 minutes or control goes into
Watchguard Pressure Switch mode High heat prove
switch S102 may also close). A 15 second pre−purge
follows once S128 closes.
When there is a call for heat, the SureLight integrated con-
trol runs a self check. The control checks for S10 primary
limit, S21 secondary limit (s) and S47 rollout switch nor-
mally closed contacts. The control also checks for S102
high heat and S128 low heat prove switch normally open
contacts. Once self check is complete and all safety
switches are operational, heat call can continue.
2− SureLight control begins 20 second ignitor warm up
period.
3− Gas valve opens on first stage for a 4 second trial for
ignition. Ignitor stays energized during the trial or until
flame sensed.
4− Flame is sensed, gas valve remains on first stage heat,
ignitor de−energizes.
Two−Stage Thermostat, Two Stage Heat. Jumper E20
set at ꢀTWO".
5− After 45 second delay, indoor blower B3 is energized
on low heat speed.
1− SureLight control energizes combustion air inducer B6
on low heat speed. Combustion air inducer runs until
S128 low heat prove switch contacts close (switch
must close within 2 1/2 minutes or control goes into
Watchguard Pressure Switch mode. High heat prove
switch S102 may also close). A 15 second pre−purge
follows once S128 closes.
6− A 10 minute (factory set) or 15 minute (field set) second
stage heat delay period begins.
7− After the delay the combustion air inducer ramps up to
high heat speed.
8− S102 high heat prove switch closes and the gas valve
energizes second stage heat.
2− SureLight control begins 20 second ignitor warm up
period.
9− B3 indoor blower energizes on high heat speed.
3− Gas valve opens on first stage for a 4 second trial for
ignition. Ignitor stays energized during the trial or until
flame sensed.
4− Flame is sensed, gas valve remains on first stage heat,
ignitor de−energizes.
5− After 45 second delay, indoor blower B3 is energized
on low heat speed.
The furnace will stay in this mode until first stage de-
mand is satified OR a second stage heat demand is
initiated.
6− Second stage heat demand initiated. A 30 second sec-
ond stage recognition period begins.
7− The combustion air inducer ramps up to high heat
speed.
8− S102 high heat prove switch closes and the gas valve
energizes second stage heat.
9− B3 indoor blower energizes on high heat speed.
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HEATING SEQUENCE OF OPERATION
NORMAL AND ABNORMAL HEATING MODE
GAS VALVE OFF. COMBUSTION AIR INDUCER
POWER ON
OFF. INDOOR BLOWER OFF. CHECK FOR
BROKEN IGNITOR OR OPEN IGNITER CIRCUIT.
DS1 AND DS2 ALTERNATING FAST FLASH.
NO
CONTROL SELF−CHECK OKAY?
GAS VALVE OFF. COMBUSTION AIR INDUCER OFF.
INDOOR BLOWER OFF. (RESET CONTROL BY
TURNING MAIN POWER OFF.) DS1 ON, DS2 ON
POLARITY REVERSED.
DS1 −− FAST FLASH
DS2 −− SLOW FLASH
NO
POLARITY OKAY?
YES
NO
IS THERE A
PROPER GROUND?
SIGNAL HOLDS UNTIL UNIT IS PROPERLY GROUNDED.
DS1 AND DS2 ALTERNATING FAST FLASH.
YES
NO
IS VOLTAGE
ABOVE 75 VOLTS?
SIGNAL HOLDS UNTIL VOLTAGE RISES ABOVE 75 VOLTS.
DS1 AND DS2 ALTERNATING FAST FLASH.
YES
GAS VALVE OFF. COMBUSTION AIR INDUCER ON.
INDOOR BLOWER ON HEATING SPEED.
DS1 SLOW FLASH, DS2 OFF.
NO
BURNER OFF?
(CONTINUOUS FLAME CHECK)
YES
A
NORMAL OPERATION:
DS 1 −− SIMULTANEOUS SLOW FLASH
DS 2 −− SIMULTANEOUS SLOW FLASH
COMBUSTION AIR INDUCER OFF.
INDOOR BLOWER ON. HAS PRIMARY OR
YES
SECONDARY LIMIT RESET WITHIN 3 MINUTES?
DS1 SLOW FLASH, DS2 ON.
B
NO
THERMOSTAT CALLS FOR HEAT:
DS 1 −− SIMULTANEOUS FAST FLASH
DS 2 −− SIMULTANEOUS FAST FLASH
NO
NO
60−MINUTE LIMIT WATCHGUARD MODE.
GAS VALVE OFF, COMBUSTION AIR INDUCER
OFF, INDOOR BLOWER OFF WITH DELAY.
DS1 AND DS2 ALTERNATING SLOW FLASH.
YES
PRIMARY AND SECONDARY LIMIT
SWITCHES CLOSED?
YES
GAS VALVE OFF. COMBUSTION AIR INDUCER OFF.
NO
ROLLOUT SWITCH CLOSED?
NO
HAS MANUAL ROLLOUT SWITCH(ES) BEEN
RESET (CLOSED) WITHIN 3 MINUTES?
DS1 SLOW FLASH, DS2 ON.
YES
YES
FIRST (LOW) STAGE PRESSURE
SWITCHES OPEN?
NO
NO
YES
GAS VALVE OFF. COMBUSTION AIR INDUCER OFF.
INDOOR BLOWER OFF. CONTROL REMAINS UNTIL
PRESSURE SWITCH IS DETECTED OPEN.
DS1 OFF, DS2 SLOW FLASH.
SECOND (HIGH) STAGE PRESSURE
SWITCHES OPEN?
GAS VALVE OFF.
COMBUSTION AIR INDUCER OFF.
INDOOR BLOWER OFF.
TWO−STAGE OR SINGLE−STAGE THERMOSTAT
CALL FOR HEAT
CONTROL WILL NOT ATTEMPT SECOND−STAGE
OPERATION DURING THIS HEAT DEMAND.
FIRST−STAGE OPERATION WILL BE ATTEMPTED.
DS1 OFF, DS2 FAST FLASH.
COMBUSTION AIR INDUCER ON LOW SPEED.
DS1 AND DS2 SIMULTANEOUS FAST FLASH
CONTINUED ON NEXT PAGE
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HEATING SEQUENCE OF OPERATION
CONTINUED
THERMOSTAT CALLS FOR HEAT
DS1 AND DS2 SIMULTANEOUS FAST FLASH
(Refer to box A on previous page)
NO
FIRST−STAGE (LOW FIRE) PRESSURE
SWITCH CLOSED WITHIN 2.5 MINUTES?
GAS VALVE OFF. COMBUSTION AIR INDUCER
OFF. INDOOR BLOWER OFF. UNIT WILL RETRY
AFTER 5−MINUTE WAIT PERIOD.
YES
DS1 OFF, DS2 SLOW FLASH.
15−SECOND COMBUSTION AIR INDUCER
PRE−PURGE INITIATED BY CLOSED FIRST−STAGE
PRESSURE SWITCH (or 15 SECOND
INTER−PURGE PERIOD.)
DS1 AND DS2 SIMULTANEOUS FAST FLASH.
IGNITOR WARM−UP (20 SECONDS)
DS1 AND DS2 SIMULTANEOUS FAST FLASH
COMBUSTION AIR INDUCER OFF, IGNITER OFF.
SIGNAL HOLDS UNTIL VOLTAGE RISES ABOVE 75 VOLTS.
DS1 AND DS2 ALTERNATING FAST FLASH.
NO
NO
NO
IS VOLTAGE ABOVE 75 VOLTS?
YES
COMBUSTION AIR INDUCER OFF, IGNITER OFF.
SIGNAL HOLDS UNTIL UNIT IS PROPERLY GROUNDED.
DS1 AND DS2 ALTERNATING FAST FLASH.
IS THERE A PROPER GROUND?
COMBUSTION AIR INDUCER OFF, IGNITOR OFF.
SIGNAL HOLDS UNTIL IGNITOR IS REPLACED
OR RECONNECTED.
IS IGNITOR INTACT AND CONNECTED?
DS1 AND DS2 ALTERNATING FAST FLASH.
YES
AT END OF IGNITOR 20 SECOND WARM UP
PERIOD, 4−SECOND TRIAL FOR IGNITION.
GAS VALVE OPENS, IGNITOR ENERGIZED DURING
4−SECOND TRIAL UNTIL FLAME SENSED.
DS1 AND DS2 SIMULTANEOUS FAST FLASH.
YES
4−SECOND FLAME STABILIZATION PERIOD.
DS1 AND DS2 SIMULTANEOUS FAST FLASH.
GAS VALVE OFF. COMBUSTION AIR
INDUCER ON. INDOOR BLOWER OFF.
DS1 SLOW FLASH, DS2 FAST FLASHN.
HAS CONTROL FAILED TO SENSE
FLAME FOR FIVE CONSECUTIVE TRIES
DURING A SINGLE HEAT DEMAND?
FLAME RECTIFICATION CURRENT CHECK
CAN FLAME BE PROVEN WITHIN 4
SECONDS AFTER GAS VALVE OPENS?
(u0.16 microamps)
NO
NO
YES
WATCHGUARD MODE. GAS VALVE OFF,
COMBUSTION AIR INDUCER OFF.
INDOOR BLOWER OFF.
YES
DS1 AND DS2 ALTERNATING SLOW FLASH.
IS 60−MINUTE RESET PERIOD COMPLETE?
YES
NO
HAS CONTROL RESET IGNITION SEQUENCE
FOUR (4) TIMES?
DS1 SLOW FLASH, DS2 FAST FLASH.
FLAME PRESENT?
NO
YES
CONTINUED ON NEXT PAGE
Page 41
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HEATING SEQUENCE OF OPERATION
CONTINUED
THERMOSTAT CALLS FOR HEAT.
DS1 AND DS2 SIMULTANEOUS FAST FLASH.
SEE BOX A.
FLAME SIGNAL ABOVE
(u0.22 microamps)
NO
LOW FLAME SIGNAL
(Does not affect control operation)
DS1 SLOW FLASH, DS2 FAST FLASH.
YES
YES
SINGLE−STAGE THERMOSTAT MODE
(E20 SET AT ꢁSINGLE")
TWO STAGE THERMOSTAT MODE
(E20 SET AT ꢁTWO")
YES
YES
START SECOND−STAGE RECOGNITION
ON DELAY (10 OR 15 MINUTES).
DS1 AND DS2 SIMULTANEOUS FAST FLASH.
45−SECOND INDOOR BLOWER ON DELAY BEGINS.
DS1 AND DS2 SIMULTANEOUS FAST FLASH.
YES
YES
FIRST−STAGE (LOW FIRE)
PRESSURE SWITCHES CLOSED?
PRIMARY, SECONDARY, ROLLOUT AND BACKUP
SECONDARY LIMIT SWITCHES CLOSED?
YES
NO
NO
NO
C
FIRST−STAGE HEAT DEMAND SATISFIED?
DS1 AND DS2 SIMULTANEOUS SLOW FLASH.
GAS VALVE OFF, COMBUSTION AIR INDUCER OFF,
INDOOR BLOWER ON. DS1 SLOW FLASH, DS2 ON.
YES
GAS VALVE OFF, COMBUSTION AIR INDUCER
OFF FOLLOWING POST PURGE.
INDOOR BLOWER OFF WITH DELAY
HAS PRIMARY, SECONDARY, ROLLOUT OR BACKUP
SECONDARY LIMIT SWITCH CLOSED WITHIN 3 MINUTES?
(Indoor blower on low speed during 3−minute period)
YES
DS1 AND DS2 SIMULTANEOUS SLOW FLASH
NO
SECOND−STAGE HEAT DEMAND.
SECOND−STAGE HEAT DEMAND REQUIRED?
DS1 AND DS2 SIMUTANEOUS SLOW FLASH.
LIMIT SWITCH WATCHGUARD MODE.
GAS VALVE OFF, COMBUSTION AIR INDUCER OFF,
YES
INDOOR BLOWER OFF WITH DELAY.
DS1 AND DS2 ALTERNATING SLOW FLASH.
IS 60−MINUTE RESET PERIOD COMPLETE?
YES
SECOND STAGE PRESSURE SWITCHES CLOSED?
ABNORMAL FLASH CODE.
NOTE − IF SECOND−STAGE PRESSURE SWITCHES
WERE ORIGINALLY FOUND CLOSED,
ABNORMAL CODE WILL FLASH.
GAS VALVE OFF. COMBUSTION AIR INDUCER ON.
INDOOR BLOWER OFF AFTER DELAY.
DS1 OFF, DS 2 SLOW FLASH.
YES
NO
SECOND−STAGE PRESSURE SWITCHES CLOSED
AT BEGINNING OF HEAT DEMAND?
DS1 OFF, DS2 SLOW FLASH.
NO
SECOND−STAGE 30−SECOND DELAY ON BEGINS.
DS1 AND DS2 SIMULTANEOUS FAST FLASH
YES
SECOND STAGE HEAT DEMAND
DS1 AND DS2 SIMULTANEOUS SLOW FLASH.
SECOND−STRAGE COMBUSTION AIR INDUCER
ON. SECOND−STAGE GAS VALVE ON. HIGH
HEAT INDOOR BLOWER SPEED ON.
NO
DS1 AND DS2 SIMULTANEOUS FAST FLASH.
RETURNS TO FIRST−STAGE HEAT MODE WHICH
CONTINUES UNTIL SECOND−STAGE PRESSURE
SWITCHES CAN BE PROVEN or HEAT DEMAND IS
SATISFIED. FIVE (5) MINUTE WAIT PERIOD
INITIATED BEFORE RETRY. WERE 5 ATTEMPTS
MADE FOR SECOND−STAGE HEAT?
YES
SECOND−STAGE PRESSURE SWITCHES CLOSED
IN LESS THAN TEN (10) SECONDS?
DS1 AND DS2 SIMULTANEOUS FAST FLASH.
NO
YES
YES
NORMAL OPERATION.
DS1 AND DS2 SIMULTANEOUS SLOW FLASH.
CONTINUED ON NEXT PAGE
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HEATING SEQUENCE OF OPERATION
CONTINUED
SEE BOX A
NORMAL OPERATION
DS1 AND DS2 SIMULTANEOUS SLOW FLASH.
SEE BOX B
THERMOSTAT CALLS FOR HEAT
DS 1 AND DS 2 SIMULTANEOUS FAST FLASH
GAS VALVE OFF. COMBUSTION AIR INDUCER OFF.
INDOOR BLOWER ON.
DS1 SLOW FLASH, DS2 ON.
YES
ARE PRIMARY, SECONDARY, ROLLOUT AND
BACKUP SECONDARY LIMIT SWITCHES CLOSED?
NO
HAS PRIMARY, SECONDARY, ROLLOUT OR BACKUP
SECONDARY LIMIT SWITCH CLOSED WITHIN 3 MINUTES?
YES
NO
LIMIT SWITCH WATCHGUARD MODE. GAS VALVE
OFF. COMBUSTION AIR INDUCER OFF. INDOOR
BLOWER OFF WITH DELAY. IS 60−MINUTE RESET
PERIOD COMPLETE? DS SLOW FLASH, DS2 ON.
YES
GAS VALVE OFF, COMBUSTION AIR INDUCER OFF
AFTER 15 SECOND POST PURGE, INDOOR
BLOWER OFF AFTER DELAY.
YES
NO
FIRST−STAGE (LOW FIRE) HEAT
PRESSURE SWITCHES CLOSED?
DS1 OFF, DS2 FAST FLASH.
RETURN TO HEAT DEMAND?
RETURN TO FIRST−STAGE HEAT MODE.
FIRST−STAGE CONTINUES UNTIL SECOND−
STAGE PRESSURE SWITCHES CAN BE PROV-
EN or HEAT DEMAND IS SATISFIED. A FIVE (5)
MINUTE WAIT PERIOD IS INITIATED BEFORE
RETRY. WERE 5 ATTEMPTS MADE FOR
SECOND−STAGE HEAT?
SECOND−STAGE (HIGH FIRE) HEAT
PRESSURE SWITCHES CLOSED?
YES
NO
YES
NO
HEAT DEMAND SATISFIED?
DS1 AND DS2 SIMULTANEOUS FAST FLASH.
SEE BOX C
FIRST−STAGE HEAT DEMAND SATISFIED?
YES
YES
SINGLE−STAGE THERMOSTAT MODE
(E20 SET AT ꢁSINGLE")
TWO STAGE THERMOSTAT MODE?
(E20 SET AT ꢁTWO")
YES
YES
SECOND STAGE HEAT
FIRST AND SECOND STAGE HEAT
DEMAND SATISFIED SIMULTANEOUSLY.
DS1 & DS2 SIMULTANEOUS FAST FLASH.
HEAT DEMAND SATISFIED?
DS1 AND DS2
SIMULTANEOUS FAST FLASH.
DEMAND SASTISFIED?
DS1 AND DS2
SIMULTANEOUS FAST FLASH.
NO
YES
YES
YES
GAS VALVE OFF, COMBUSTION AIR
INDUCER OFF AFTER POST PURGE
PERIOD, INDOOR BLOWER OFF AF-
TER SELECTED DELAY.
GAS VALVE, COMBUSTION AIR INDUCER
AND INDOOR BLOWER RETURN TO FIRST−
STAGE OPERATION.
DS1 AND DS2 SIMULTANEOUS FAST FLASH.
DS1 AND DS2
SIMULTANEOUS FAST FLASH
FIRST STAGE HEAT DEMAND SATISFIED?
YES
GAS VALVE OFF. COMBUSTION AIR INDUCER
OFF AFTER 5−SECOND POST−PURGE PERIOD.
INDOOR BLOWER OFF. DELAY INITIATED.
DS1 & DS2 SIMULTANEOUS FAST FLASH.
DEMAND FOR HEAT SATISFIED.
POWER ON STAND BY.
DS1 AND DS2
SIMULTANEOUS SLOW FLASH
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COOLING SEQUENCE OF OPERATION
POWER ON
YES
IS POLARITY REVERSED?
SIGNAL POLARITY REVERSED.
DS1 FAST FLASH, DS2 SLOW FLASH.
NO
SIGNAL IMPROPER
GROUND AT DS.
SIGNAL HOLDS
UNTIL UNIT IS
PROPERLY
NO
NO
YES
IS THERE
PROPER GROUND?
IS VOLTAGE
ABOVE 75 VOLTS?
LOW VOLTAGE SIGNAL AT DS HOLDS
UNTIL VOLTAGE RISES ABOVE 75 VOLTS.
YES
GROUNDED.
THERMOSTAT CALLS FOR FIRST−STAGE COOL.
COMPRESSOR AND CONDENSER FAN
ENERGIZED.
INDOOR BLOWER ENERGIZED ON FIRST STAGE
COOL SPEED AFTER 2 SECOND DELAY.
YES
COMPRESSOR AND CONDENSER FAN DE−ENERGIZED.
INDOOR BLOWER DE−ENERGIZED.
FIRST−STAGE DEMAND FOR COOL SATISFIED?
NO
THERMOSTAT CALLS FOR SECOND−STAGE COOL.
INDOOR BLOWER RAMPS UP TO SECOND−STAGE COOL SPEED.
SECOND−STAGE DEMAND FOR COOL SATISFIED?
YES
UNIT RETURNS TO FIRST STAGE COOL
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CONTINUOUS LOW SPEED FAN SEQUENCE OF OPERATION
MANUAL FAN SELECTION MADE AT THERMOSTAT.
AFTER 2 SECOND DELAY, INDOOR BLOWER IS
ENERGIZED ON CONTINUOUS FAN SPEED
(LOW HEAT / LOW COOL).
YES
YES
THERMOSTAT CALLS FOR FIRST STAGE COOL.
YES
THERMOSTAT CALLS FOR FIRST−STAGE HEAT.
YES
COMPRESSOR IS ENERGIZED AND INDOOR
BLOWER CONTINUES TO OPERATE IN LOW
COOL SPEED.
BURNERS IGNITE AND INDOOR BLOWER
CONTINUES TO OPERATE IN CONTINUOUS
LOW (LOW HEAT / LOW COOL) MODE.
FIRST−STAGE COOL DEMAND SATISFIED?
FIRST−STAGE HEAT DEMAND SATISFIED.
NO
YES
YES
NO
SECOND STAGE COOL DEMAND
THERMOSTAT CALLS FOR SECOND−STAGE HEAT.
YES
INDOOR BLOWER RAMPS TO SECOND
STAGE COOL SPEED
INDOOR BLOWER SWITCHES TO HIGH HEAT SPEED
AFTER 30−SECOND RECOGNITION PERIOD.
YES
SECOND STAGE COOL DEMAND SATISFIED?
YES
SECOND−STAGE HEAT DEMAND SATISFIED.
YES
INDOOR BLOWER RAMPS DOWN TO FIRST STAGE
COOL SPEED.
INDOOR BLOWER RAMPS DOWN TO LOW
HEAT SPEED.
NOTE − Continuous low speed fan and cooling low
speed are equal to the low heat fan speed.
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VIII− Field Wiring Applications and Jumper Settings
Field Wiring Applications
Thermostat
1 Heat / 1 Cool
Wiring Connections
W915
E20
Y1 to Y2
Leave Installed
SINGLE
SINGLE
TWO
S1
T’STAT
CONTROL
TERM. STRIP
OUTDOOR
UNIT
NOTE − Use dip switch 3
to set second−stage heat
ON delay.
ON−10 minutes. OFF−15
minutes.
HSXB15
(LSOM)
1 Heat / 2 Cool
Clip
S1
T’STAT
CONTROL
TERM. STRIP
OUTDOOR
UNIT
NOTE − Use dip switch 3
to set second−stage heat
ON delay.
ON−10 minutes. OFF−15
minutes.
HSXA19
(LSOM)
2 Heat / 2 Cool
Clip
S1
T’STAT
CONTROL
TERM. STRIP
OUTDOOR
UNIT
HSXA19
(LSOM)
2 Heat / 1 Cool
TWO
Leave Installed
S1
T’STAT
CONTROL
TERM. STRIP
OUTDOOR
UNIT
HSXB15
(LSOM)
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Field Wiring Applications (Continued)
Thermostat
Wiring Connections
W915
E20
Y1 to Y2
Leave Installed
FM21 Heat Pump / 1
Cool
SINGLE
CONTROL
TERM. STRIP
FM21
*Disconnect existing
furnace transformer and re-
place with 75VA, 24V trans-
former if defrost option to be
used.
75VA, 24V
TRANSFORMER*
NOTE − Wiring connections to
outdoor unit and thermostat
made at FM21 control board
per FM21 instructions.
NOTE −
Cut Y1/Y2 jumper
for two−stage
cooling.
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IX−SURELIGHT® CONTROL TROUBLESHOOTING CHART
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
1.1
Possible Cause
1.1.1
Corrective Action / Comments
ACTION 1 − Check 120V main voltage.
Determine cause of main power failure.
− Both diagnostic lights fail to light up. Main voltage 120V not supplied to unit.
1.1.2
ACTION 1 − Check for correct wiring of 120V to
power make up box and transformer.
ACTION 2 − Check 24V wiring to control board.
LED#1−Off
LED#2−Off
Miswiring of furnace or improper con-
nections.
1.1.3
ACTION 1 − Replace fuse.
ACTION 2 − If fuse still blows, check for short.
Blown fuse
ACTION 1 − Check that door switch is activated
when door is closed.
ACTION 2−Check wire connections to switch, re-
place loose connectors.
ACTION 3 − Check continuity of switch in closed
position. Replace if defective.
1.1.4
Door interlock switch failure.
1.1.5
Transformer Failure.
1.1.6
ACTION 1 − Check that transformer output is
24V. Replace if defective.
ACTION 1 − If all the above items have been
checked, replace board.
Failed control board.
ACTION 1 − Manually reset the roll−out switch
by pushing the top button.
1.2
1.2.1
ACTION 2 − Determine the cause of the roll−out
switch activation before leaving furnace.
− Diagnostic lights flash the roll−out
Roll−out switch open.
code.
ACTION 1 − Check continuity across roll−out
switch. Replace roll−out switch if switch is reset
but does not have continuity.
1.2.2
Roll−out switch failure.
LED#1−On,
1.2.3
LED#2−Slow Flash
ACTION 1 − Check wiring connections to switch.
Miswiring or improper connections at
roll−out switch.
ACTION 1 − Check 9−pin connector for proper
connection to control board.
1.2.4
ACTION 2 − Check continuity of the multi plug
pin.
9 pin connector failure
1.3
− On initial power−up the comb. air in-
ducer does not energize.
− Diagnostic lights flash the reverse
polarity code.
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.
1.3.1
120V main power polarity reversed.
LED#1−Fast Flash,
LED#2−Slow Flash.
1.4
1.4.1
ACTION 1 − Check for 120V to combustion air
inducer. If no power, check wire and connec-
tions.
− On initial power up the combustion
air inducer does not energize.
− Diagnostic lights flash normal power
on operation.
Open combustion air inducer motor
circuit.
1.4.2
ACTION 1 − If power is present at blower, replace
blower.
LED#1−Slow Flash
LED#2−Slow Flash
Failed combustion air inducer motor.
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PROBLEM 1: UNIT FAILS TO OPERATE IN THE COOLING, HEATING, OR CONTINUOUS FAN MODE
Condition
1.5
Possible Cause
Corrective Action / Comments
ACTION 1 − Check that the unit is properly
ground.
1.5.1
− Diagnostic lights flash the improper
main ground.
ACTION 2 − Install a proper main ground to the
unit
Improper ground to the unit.
1.5.2
ACTION 1 − Check 6−pin connector for proper
installation. Correctly insert connector into con-
trol.
6−Pin connector is improperly
attached to the circuit board.
LED#1−Alternating Fast Flash
LED#2−Alternating Fast Flash
ACTION 1 − Check that the line voltage is above
75V. Determine cause of voltage drop and supply
correct voltage to the control.
1.5.3
Line voltage is below 75V.
ACTION 1 − Check for correct wiring and loose
connections in the ignitor circuit. Check mult−plug
connections for correct installation.
1.5.4
Open ignitor circuit.
ACTION 1 − Unplug ignitor and read resistance
across ignitor. If resistance does not read be-
tween 10.9 and 19.7 ohms, replace the ignitor.
1.5.5
Broken or failed ignitor.
PROBLEM 2: UNIT FAILS TO FIRE IN THE HEATING MODE, COMBUSTION AIR BLOWER DOES NOT
ENERGIZE
Condition
2.1
Possible Cause
Corrective Action / Comments
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.
− Unit operates with a cooling or contin-
uous fan demand.
− Combustion air inducer will not start
with a Heating demand.
2.1.1
Primary, secondary or backup secon-
dary (if equipped ) limit open.
− Diagnostic lights flash the limit failure
mode.
2.1.2
ACTION 1 − Check for correct wiring and loose
connections. Correct wiring and/or replace any
loose connections.
Miswiring of furnace or improper
connections at limit switch(es).
LED#1−Slow Flash,
LED#2−On
2.2
2.2.1
− Unit operates with a cooling and con-
tinuous fan demand.
− Combustion air inducer will not start
with a Heating demand.
ACTION 1 − Check for correct wiring and loose
connections. Correct wiring and/or replace any
loose connections.
Miswiring of furnace or improper
connections to combustion air
inducer.
− Diagnostic lights flash the pressure
switch failure code.
ACTION 1 − Check that the prove switch is open
without the combustion air inducer operating. Re-
place if defective.
2.2.2
LED#1−Off,
LED#2−Slow Flash
Prove switch stuck closed.
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PROBLEM 2: UNIT FAILS TO FIRE IN THE HEATING MODE, COMBUSTION AIR INDUCER DOES
NOT ENERGIZE (CONT.).
Condition
2.3
Possible Cause
Corrective Action/Comments
2.3.1
− Unit operates with a cooling and con-
tinuous fan demand.
− Combustion air inducer will not start
with a Heating demand.
ACTION 1 − Check for correct wiring and loose
connections. Correct wiring and/or replace any
loose connections.
Miswiring of furnace or improper
connections to combustion air induc-
er.
− Diagnostic lights flash the pressure
switch failure code 2.5 minutes after
heating demand.
ACTION 1 − If there is 120V to combustion air in-
ducer and it does not operate, replace combus-
tion air inducer.
2.3.2
Combustion air inducer failure.
LED#1−Off,
LED#2−Slow Flash
PROBLEM 3: UNIT FAILS TO FIRE IN THE HEATING MODE, COMBUSTION AIR INDUCER
ENERGIZES, IGNITOR IS NOT ENERGIZED.
Condition
3.1
Possible Cause
3.1.1
Corrective Action/Comments
ACTION 1−Check that the prove switch lines are
correctly routed. Correctly route pressure switch
lines.
− Unit operates with a cooling and
continuous fan demand.
− Combustion air inducer energizes
with a heating demand.
− Diagnostic lights flash the pressure
switch failure code 2.5 minutes after
heating demand.
Prove switch does not close due to
incorrect routing of the pressure
switch lines.
3.1.2
ACTION 1 − Remove any obstructions from the
the pressure lines and/or taps.
Prove switch does not close due to
obstructions in the pressure lines.
3.1.3
ACTION 1 − Check prove switch lines for leaks.
Replace any broken lines.
Prove switch lines damaged
3.1.4
LED#1−Off
LED#2−Slow Flash
ACTION 1−Check prove switch lines for conden-
sate. Remove condensate from lines.
Condensate in prove switch line.
ACTION 1 − Check the differential pressure
across the prove switch. This pressure should
exceed the set point listed on the switch.
ACTION 2 − Check for restricted inlet vent. Re-
move all blockage.
3.1.5
Prove switch does not close due to a
low differential pressure across the
prove switch.
ACTION 3 − Check for proper vent sizing and
run length.
3.1.6
ACTION 1 − Check that the proper prove switch
is installed in the unit. Replace prove switch if
necessary.
Wrong prove switch installed in the
unit, or prove switch is out of
calibration.
3.1.7
ACTION 1 − Check for correct wiring and loose
connections. Correct wiring and/or replace any
loose connections.
Miswiring of furnace or improper
connections at prove switch.
ACTION 1−If all the above modes of failure have
been checked, the prove switch may have failed.
Replace prove switch and determine if unit will
operate.
3.1.8
Prove switch failure.
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PROBLEM 4: UNIT FAILS TO FIRE IN THE HEATING MODE, COMBUSTION AIR BLOWER
ENERGIZES, IGNITOR IS ENERGIZED.
Condition
4.1
Possible Cause
Corrective Action/Comments
ACTION 1−Check line pressure at the gas valve.
Pressure should not exceed 13" WC for both nat-
ural and propane. Line pressure should read a
minimum 4.5" WC for natural and 8.0"WC for pro-
pane.
4.1.1
− Unit operates with a cooling and
continuous fan demand.
− Combustion air inducer energizes
with Heating demand.
Check that gas is being supplied to
the unit.
4.1.2
ACTION 1 − Check for correct wiring and loose
connections. Correct wiring and/or replace any
loose connections.
Miswiring of gas valve or loose-
connections at multi−pin control amp
plugs or valve.
− Ignitor is energized but unit fails to
light.
ACTION 1−Check that 24V is supplied to the gas
valve approximately 35 seconds after heat de-
mand is initiated.
ACTION 2 − Replace the valve if 24V is supplied
but valve does not open.
4.1.3
LED#1−Alternating Slow Flash
LED#2−Alternating Slow Flash
Defective gas valve or ignition
control.
ACTION 3 − Replace the control board if 24V is
not supplied to valve.
PROBLEM 5: BURNERS LIGHT WITH A HEATING DEMAND BUT UNIT SHUTS DOWN
PREMATURELY
Condition
Possible Cause
5.1.1
Corrective Action/Comments
ACTION 1 − Check for restricted intake and ex-
haust vent. Remove all blockage.
Low pressure differential at the prove
switch.
ACTION 2: Check for proper vent sizing. See
installation instructions.
5.1
5.1.2
− Burners fire with a heating demand.
− Burners light but unit shuts off prior
to satisfying T−stat demand.
− Diagnostic lights flash the pressure
switch code.
ACTION 1 − Check vent termination kit installed.
See Placement and Installation section.
Wrong concentric vent kit used for
terminating the unit.
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 con-
densate lines.
5.1.3
Condensate drain line is not draining
properly.
LED#1−Off
LED#2−Slow Flash
ACTION 1 − Check for restricted intake and ex-
haust. Remove all blockage.
5.1.4
Low pressure differential at the prove
switch.
ACTION 2: Check for proper vent sizing. See
installation instructions.
5.2
5.2.1
ACTION 1 − Check that sensor is properly lo-
cated and that the sense wire is properly at-
tached to both the sensor and the control.
− Combustion air inducer energizes
with a heating demand.
Sensor or sense wire is improperly
installed.
− Burners light but fail to stay lit.
− After 5 tries the control diagnostics
flash the watchguard burners failed to
ignite code.
ACTION 1 − Check for a broken sensor.
ACTION 2 − Test continuity across the sense
wire. If wire or sensor are damaged replace the
component.
5.2.2
Sensor or sense wire is broken.
ACTION 1 − Check for resistance between the
sensor rod and the unit ground.
5.2.3
ACTION 2 − Check for resistance between the
sensor wire and the unit ground.
ACTION 3 − Correct any shorts found in circuit.
Sensor or sensor wire is grounded to
the unit.
LED#1−Alternating Slow Flash
LED#2−Alternating Slow Flash
ACTION 1 − Check the microamp signal from
the burner flame. If the microamp signal is be-
low normal, 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.
5.2.4
Control does not sense flame.
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PROBLEM 5: BURNERS LIGHT WITH HEATING DEMAND BUT UNIT SHUTS DOWN
PREMATURELY (CONT.)
Condition
5.3
Possible Cause
Corrective Action/Comments
ACTION 1 − Check that the manifold pressure
matches value listed on nameplate. See installa-
tion instructions for proper procedure.
ACTION 2 − Verify that the installed orifice size
match the size listed on the nameplate or installa-
tion instructions.
− Combustion air inducer energizes
with a heating demand.
− Burners light.
− Roll−out switch trips during the
heating demand.
5.3.1
Unit is firing above 100% of the
nameplate input.
ACTION 3 − Check gas valve sensing hose to in-
sure no leaks are present.
ACTION 4 − Check the input rate to verify rate
matches value listed on nameplate.
− Diagnostic lights flash roll−out fail-
ure.
ACTION 1 − Tighten orifice until leak is sealed.
NOTE: Be careful not to strip orifice threads.
ACTION 2 − Check for gas leakage at the
threaded orifice connection. Use approved meth-
od for leak detection (see unit instructions).
5.3.2
Gas orifices leak at the manifold
connection.
LED#1−On
LED#2−Slow Flash
5.3.3
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, replace
heat exchanger if necessary, tag and return heat
exchanger to proper Lennox personnel.
Air leakage at the connections
between the primary heat exchanger,
secondary heat exchanger, and
combustion air blower.
5.3.4
ACTION 1 − Check for sooting deposits or other
restrictions in the heat exchanger assembly.
Clean assembly as outlined in instruction manu-
al.
Insufficient flow through the heat
exchanger caused by a sooted or
restricted heat exchanger.
ACTION 2 − Check for proper combustion.
5.3.5
ACTION 1 − Check that the burners are firing into
the center of the heat exchanger openings. Cor-
rect the location of the burners if necessary.
Burners are not properly located in
the burner box.
5.4
5.4.1
ACTION 1 − Check for proper flow of exhaust
gases away from intake vent. Remove any ob-
stacles in front of the intake and exhaust vent
which would cause recirculation.
ACTION 2−Check for correct intake and exhaust
vent installation. See instructions
− Combustion air inducer energizes
with a heating demand.
− Burners light roughly and the unit
fails to stay lit.
− Diagnostic lights flash watchguard
flame failure.
Recirculation of flue gases. This
condition causes rough ignitions and
operation. Problem is characterized
by nuisance flame failures.
ACTION 1 − Remove burner and inspect the
cross−overs for burrs, or any restriction or if
crossover is warped. Remove restriction or re-
place burners.
5.4.2
LED#1−Alternating Slow Flash
LED#2−Alternating Slow Flash
Improper burner cross−overs
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PROBLEM 6: CONTROL SIGNALS LOW FLAME SENSE DURING HEATING MODE
Condition
6.0
Possible Cause
6.1.1
Corrective Action/Comments
ACTION 1−Check the sensor rod for proper loca-
tion on the burner. Properly locate the sensor rod
or replace if rod cannot be located correctly.
− Unit operates correctly but the diag-
nostic lights flash low flame sense
code.
Sensor rod is improperly located on
the burner.
ACTION 1 − Check sensor rod for contamination
or coated surface. Clean the sensor rod with steel
wool or replace sensor. DO NOT USE SAND PA-
PER TO CLEAN ROD. SAND PAPER WILL
CONTRIBUTE TO THE CONTAMINATION
PROBLEM.
6.1.2
LED#1−Slow Flash
LED#2−Fast Flash
Sensor rod is contaminated.
PROBLEM 7: INDOOR BLOWER FAILS TO OPERATE IN COOLING, HEATING, OR CONTINUOUS
FAN MODE
Condition
7.0
Possible Cause
7.1.1
Corrective Action/Comments
ACTION 1− Correct wiring and/or replace any
loose connections. Check for correct wiring and
loose connections.
− Indoor blower fails to operate in
continuous fan, cooling, or heating
mode.
Miswiring of furnace or improper
connections at control or indoor blow-
er motor.
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 motor tap but
the blower does not operate, replace the motor.
7.1.2
120V is not being supplied to the
indoor air blower or blower motor fail-
ure.
7.1.3
ACTION 1 − If there is not 120V when "Y", "G", or
"W" is energized, replace the control.
Defective control board
7.1.4
ACTION 1 − Replace capacitor
Defective run capacitor
PROBLEM 8: RF STATIC DURING TIME FOR IGNITION
Condition
8.0
Possible Cause
8.1.2
Corrective Action/Comments
ACTION 1 − Call Technical Support, Dallas.
− AM radio interference.
Ignitor operation
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SERVICE NOTES
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