Lennox ML196UH030XE36B Installation and operation manual

Page 1
©2020 Lennox Industries Inc.
Litho U.S.A.
Corp 1911-L7
07/2020 ML196UHE
Service Literature
ML196UHE SERIES UNITS
ML196UHE series units are high-efficiency gas fur
naces manufactured with Lennox DuralokPlustalumi
nized steel clamshell-type heat exchangers, with a stainless
steel condensing coil. ML196UHE units are available in
heating input capacities of 30,000 to 135,000 Btuh and
cooling applications from 1.5 through 5 tons. Refer to Engi
neering Handbook for proper sizing.
Units are factory equipped for use with natural gas. A kit is
available for conversion to LP/Propane operation. All
ML196UHE units are equipped with a hot surface ignition
system. The gas valve is redundant to assure safety
shut-off as required by C.S.A.
The heat exchanger, burners and manifold assembly can be
removed for inspection and service. The maintenance section
gives a detailed description on how this is done.
All specifications are subject to change. Procedures outlined
in this manual are presented as a recommendation only
and do not supersede or replace local or state codes.
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.
Table of Contents
Specifications 2.................................
Optional Accessories 3..........................
Blower Performance Data 4......................
I-Unit Components 7............................
II Placement and Installation 21....................
III-Start-Up 42...................................
IV-Heating System Service Checks 43..............
V-Typical Operating Conditions 47.................
VI-Maintenance 48...............................
VII-Sequence of Operation and Flow Charts 51......
WARNING
Improper installation, adjustment, alteration, service
or maintenance can cause property damage, person
al injury or loss of life. Installation and service must
be performed by a licensed professional HVAC in
staller (or equivalent), service agency or the gas sup
plier.
CAUTION
As with any mechanical equipment, contact with
sharp sheet metal edges can result in personal in
jury. Take care while handling this equipment and
wear gloves and protective clothing.

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SPECIFICATIONS
Gas
Heating
Performance
Model No. ML196UH
030XE36B
ML196UH
045XE36B
ML196UH
070XE36B
ML196UH
070XE48B
ML196UH
090XE36C
1AFUE 96% 96% 96% 96% 96%
Input - Btuh 30,000 44,000 66,000 66,000 88,000
Output - Btuh 29,000 42,800 63,900 63,900 85,600
Temperature rise range - °F 25 - 55 35 - 65 35 - 65 30 - 60 45 - 75
Gas Manifold Pressure (in. w.g.)
Nat. Gas / LPG/Propane 3.5 / 10 3.5 / 10 3.5 / 10 3.5 / 10 3.5 / 10
High static - in. w.g. 0.5 0.5 0.5 0.5 0.5
Energy Star® Certied Yes Yes Yes Yes Yes
Connections
in.
Intake / Exhaust Pipe (PVC) 2 / 2 2 / 2 2 / 2 2 / 2 2 / 2
Gas pipe size IPS 1/2 1/2 1/2 1/2 1/2
Condensate Drain Trap (PVC pipe) - i.d. 3/4 3/4 3/4 3/4 3/4
with furnished 90° street elbow 3/4 slip x 3/4 Mipt
with eld supplied (PVC coupling) - o.d. 3/4 slip x 3/4 MPT
Indoor
Blower
Wheel nom. dia. x width - in. 10 x 8 10 x 8 10 x 8 11-1/2 x 10 10 x 8
Motor Type DC Brushless DC Brushless DC Brushless DC Brushless DC Brushless
Motor output - hp 1/2 1/2 1/2 3/4 1/2
Tons of add-on cooling 1.5 - 3 1.5 - 3 1.5 - 3 2 - 4 1.5 - 3
Air Volume Range - cfm 175 - 1435 520 - 1345 550 - 1380 500 - 1710 460 - 1470
Electrical Data Voltage 120 volts - 60 hertz - 1 phase
Blower motor full load amps 6.8 6.8 6.8 8.4 6.8
Maximum overcurrent protection 15 15 15 15 15
Shipping Data lbs. - 1 package 120 124 129 XXX XXX
NOTE - Filters and provisions for mounting are not furnished and must be eld provided.
1 Annual Fuel Utilization E󰀩ciency based on DOE test procedures and according to FTC labeling regulations. Isolated combustion system rating for non-weatherized furnaces.
SPECIFICATIONS
Gas
Heating
Performance
Model No. ML196UH
090XE48C
ML196UH
090XE60C
ML196UH
110XE60C
ML196UH
135XE60D
1AFUE 96% 96% 96% 96%
Input - Btuh 88,000 88,000 110,000 132,000
Output - Btuh 85,600 85,600 107,200 127,000
Temperature rise range - °F 50 - 80 35 - 65 45 - 75 45 - 75
Gas Manifold Pressure (in. w.g.)
Nat. Gas / LPG/Propane 3.5 / 10 3.5 / 10 3.5 / 10 3.5 / 10
High static - in. w.g. 0.5 0.5 0.5 0.5
Energy Star® Certied Yes Yes Yes Yes
Connections
in.
Intake / Exhaust Pipe (PVC) 2 / 2 2 / 2 2 / 2 2 / 2
Gas pipe size IPS 1/2 1/2 1/2 1/2
Condensate Drain Trap (PVC pipe) - i.d. 3/4 3/4 3/4 3/4
with furnished 90° street elbow 3/4 slip x 3/4 Mipt
with eld supplied (PVC coupling) - o.d. 3/4 slip x 3/4 MPT
Indoor
Blower
Wheel nom. dia. x width - in. 10 x 10 11 x 11 11-1/2 x 10 11 x 11
Motor Type DC Brushless DC Brushless DC Brushless DC Brushless
Motor output - hp 3/4 1 1 1
Tons of add-on cooling 2.5 - 4 3-5 3 - 5 3-5
Air Volume Range - cfm 760 - 1740 XXX 1055 - 2220 1310 - 2400
Electrical Data Voltage 120 volts - 60 hertz - 1 phase
Blower motor full load amps 8.4 10.9 10.9 10.9
Maximum overcurrent protection 15 15 15 15
Shipping Data lbs. - 1 package 152 XXX 164 XXX
NOTE - Filters and provisions for mounting are not furnished and must be eld provided.
1 Annual Fuel Utilization E󰀩ciency based on DOE test procedures and according to FTC labeling regulations. Isolated combustion system rating for non-weatherized furnaces.

Page 3
OPTIONAL ACCESSORIES
“B” Width Models “C” Width Models “D” Width Models
CABINET ACCESSORIES
Horizontal Suspension Kit - Horizontal only 51W10 51W10 51W10
Return Air Base - Upow only 50W98 50W99 50W99
High Performance Economizer (Commercial Only) 10U53 10U53 10U53
CONDENSATE DRAIN KITS
Condensate Drain Heat Cable 6 ft. 26K68 26K68 26K68
24 ft. 26K69 26K69 26K69
Crawl Space Vent Drain Kit US 51W18 51W18 51W18
Canada 15Z70 15Z70 15Z70
CONTROLS
Blower Relay Kit (for two-stage outdoor units) 85W66 85W66 85W66
iComfort®M30 Smart Wi-Fi Thermostat 15Z69 15Z69 15Z69
Remote Outdoor Temperature Sensor X2658 X2658 X2658
Twinning Kit 16W72 16W72 16W72
FILTER KITS
1Air Filter and
Rack Kit
Horizontal (end) Size of lter - in. 87L96 - 18 x 25 x 1 87L97 - 20 x 25 x 1 87L98 - 25 x 25 x 1
Side Return Single 44J22 44J22 44J22
Ten Pack 66K63 66K63 66K63
Size of lter - in. 16 x 25 x 1 16 x 25 x 1 16 x 25 x 1
NIGHT SERVICE KIT
Night Service Kit 84W48 84W48 84W48
TERMINATION KITS
See Installation Instructions for specic venting information.
Termination Kits -
Direct Vent
Applications Only
Concentric US - 2 in. 71M80 69M29 - - -
3 in. - - - 60L46 60L46
Canada - 2 in. 44W92 44W92 - - -
3 in. - - - 44W93 44W93
Flush-Mount US - 2, 2-1/2 or 3 in. 51W11 51W11 51W11
Canada - 2, 2-1/2 or 3 in. 51W12 51W12 51W12
Wall - Close
Couple
US - 2 in. 22G44 - - - - - -
3 in. 44J40 44J40 44J40
Wall - Close
Couple WTK
Canada - 2 in. 30G28 - - - - - -
3 in. 81J20 81J20 81J20
Termination Kits -
Direct or Non-
Direct vent
Roof 2 in. 15F75 15F75 - - -
Wall Ring Kit 2 in. 15F74 315F74 - - -
2Roof Termination Flashing Kit - Direct or
Non-Direct Vent (2 ashings)
2 in. 44J41 44J41 44J41
VENTING
Flue Coupling 2 in. 17H92 17H92 17H92
1 Cleanable polyurethane frame type lter.
2 Kits contain enough parts for two, non−direct vent installations.
3Non-direct vent only.
NOTE - Termination Kits (44W92, 44W93, 30G28, 51W12, 51W19, 81J20) and Crawl Space Vent Drain Kit (15Z70) are certied to ULC S636 standard for use in
Canada only.

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BLOWER DATA
ML196UH045XE36B PERFORMANCE (Less Filter)
External
Static
Pressure
in. w.g.
Air Volume / Watts at Various Blower Speeds
High Medium-High Medium Medium-Low Low
cfm Watts cfm Watts cfm Watts cfm Watts cfm Watts
0.00 1460 335 1285 235 1190 170 910 85 870 75
0.10 1430 350 1260 245 1155 185 885 95 830 85
0.20 1405 365 1235 255 1125 200 860 105 800 90
0.30 1375 370 1205 265 1090 210 825 115 755 95
0.40 1350 380 1175 275 1055 215 780 125 710 105
0.50 1315 385 1145 285 1020 230 735 130 665 115
0.60 1245 375 1110 295 980 240 685 140 620 125
0.70 N/A N/A 1070 305 940 250 640 145 575 135
0.80 N/A N/A 1020 310 905 260 600 155 530 140
ML196UH070XE36B PERFORMANCE (Less Filter)
External
Static
Pressure
in. w.g.
Air Volume / Watts at Various Blower Speeds
High Medium-High Medium Medium-Low Low
cfm Watts cfm Watts cfm Watts cfm Watts cfm Watts
0.00 1445 315 1315 215 1215 165 930 85 925 75
0.10 1445 335 1275 230 1170 180 905 94 860 80
0.20 1415 345 1240 240 1125 190 870 101 800 85
0.30 1380 355 1205 250 1090 200 830 109 760 95
0.40 1345 370 1175 265 1055 210 790 117 710 105
0.50 1315 385 1150 280 1020 220 735 129 665 115
0.60 1275 390 1110 290 985 230 685 137 625 125
0.70 1210 395 1075 300 950 240 640 146 565 130
0.80 N/A N/A 1030 305 915 250 595 148 535 135
ML196UH030XE36B PERFORMANCE (Less Filter)
External
Static
Pressure
in. w.g.
Air Volume / Watts at Various Blower Speeds
High Medium-High Medium Medium-Low Low
cfm Watts cfm Watts cfm Watts cfm Watts cfm Watts
0.00 1435 346 1170 191 1000 127 775 62 705 45
0.10 1400 351 1130 199 955 132 735 71 635 48
0.20 1360 358 1085 207 905 137 680 81 515 50
0.30 1325 370 1055 217 865 148 625 84 445 55
0.40 1300 382 1020 227 815 157 570 91 380 61
0.50 1265 387 990 231 785 161 515 95 310 66
0.60 1235 402 945 244 735 168 475 104 265 68
0.70 1200 411 910 253 710 175 425 107 215 72
0.80 1160 420 885 260 660 183 355 114 175 75
ML196UH070XE48B PERFORMANCE (Less Filter)
External
Static
Pressure
in. w.g.
Air Volume / Watts at Various Blower Speeds
High Medium-High Medium Medium-Low Low
cfm Watts cfm Watts cfm Watts cfm Watts cfm Watts
0.00 1710 466 1510 305 1330 209 1240 164 1005 104
0.10 1685 477 1485 317 1305 220 1200 178 965 112
0.20 1675 486 1445 331 1250 232 1150 190 885 113
0.30 1640 498 1400 347 1210 246 1095 203 835 123
0.40 1590 518 1370 360 1170 260 1045 215 765 130
0.50 1550 532 1315 374 1135 274 995 225 700 140
0.60 1515 545 1270 392 1070 287 940 238 635 150
0.70 1475 554 1240 402 1015 300 895 247 570 156
0.80 1420 551 1195 419 965 305 835 259 500 172

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ML196UH090XE48C PERFORMANCE (Less Filter)
External
Static
Pressure
in. w.g.
Air Volume / Watts at Various Blower Speeds
High Medium-High Medium Medium-Low Low
cfm Watts cfm Watts cfm Watts cfm Watts cfm Watts
0.00 1765 375 1535 250 1410 180 1315 155 1155 115
0.10 1735 390 1500 260 1365 200 1270 165 1130 125
0.20 1700 405 1465 275 1330 215 1230 175 1095 135
0.30 1660 425 1435 290 1295 225 1195 190 1055 145
0.40 1640 435 1400 300 1265 235 1165 200 1010 155
0.50 1615 450 1370 315 1230 250 1125 215 965 165
0.60 1575 465 1340 325 1190 265 1080 230 925 180
0.70 1530 470 1305 340 1150 280 1045 235 885 190
0.80 N/A N/A 1260 345 1115 285 1000 245 845 195
BLOWER DATA
ML196UH090XE36C PERFORMANCE (Less Filter)
External
Static
Pressure
in. w.g.
Air Volume / Watts at Various Blower Speeds
High Medium-High Medium Medium-Low Low
cfm Watts cfm Watts cfm Watts cfm Watts cfm Watts
0.00 1470 313 1355 233 1195 171 975 92 895 50
0.10 1445 325 1330 249 1170 184 940 101 855 63
0.20 1430 335 1300 270 1150 196 885 109 735 75
0.30 1385 350 1265 275 1110 206 870 122 680 82
0.40 1370 365 1230 287 1085 217 815 126 640 91
0.50 1340 376 1200 298 1055 226 790 137 595 96
0.60 1300 384 1170 305 1015 231 735 146 565 103
0.70 1280 394 1150 317 985 245 700 152 505 108
0.80 1230 395 1125 328 960 256 665 162 460 117
ML196UH090XE60C PERFORMANCE (Less Filter)
External
Static
Pressure
in. w.g.
Air Volume / Watts at Various Blower Speeds
High Medium-High Medium Medium-Low Low
cfm Watts cfm Watts cfm Watts cfm Watts cfm Watts
0.00 2105 638 1860 431 1705 327 1585 274 1425 203
0.10 2075 652 1820 449 1675 344 1550 287 1380 213
0.20 2050 672 1790 470 1630 363 1505 295 1335 218
0.30 2005 694 1765 485 1590 375 1475 314 1300 233
0.40 1975 701 1715 496 1565 392 1425 325 1230 242
0.50 1960 714 1700 514 1510 405 1395 339 1195 256
0.60 1925 738 1650 530 1480 419 1355 351 1145 268
0.70 1865 745 1610 541 1435 434 1300 366 1110 282
0.80 1830 739 1580 554 1400 445 1270 383 1050 293

Page 6
BLOWER DATA
ML196UH110XE60C PERFORMANCE (Less Filter)
External
Static
Pressure
in. w.g.
Air Volume / Watts at Di󰀨erent Blower Speeds
Bottom Return Air, Side Return Air with Return Air from
Both Sides or Return Air from Bottom and One Side.
Single Side Return Air − Air volumes in bold (over 1800
cfm) require Optional Return Air Base and eld fabricated
transition to accommodate 20 x 25 x 1 in. air lter in order to
maintain proper air velocity.
High Med-High Medium Med-Low Low High Med-High Medium Med-Low Low
cfm Watts cfm Watts cfm Watts cfm Watts cfm Watts cfm Watts cfm Watts cfm Watts cfm Watts cfm Watts
0.00 2220 655 1975 440 1800 325 1665 390 1050 180 2180 685 1910 460 1750 345 1660 285 1430 195
0.10 2185 680 1925 460 1750 345 1625 285 1440 200 2155 705 1885 480 1720 360 1610 295 1415 205
0.20 2150 705 1880 480 1710 365 1590 300 1390 220 2130 725 1855 495 1685 380 1565 305 1380 220
0.30 2110 720 1850 495 1680 380 1560 320 1350 230 2085 745 1825 510 1655 390 1535 325 1335 230
0.40 2080 735 1810 520 1650 405 1515 330 1310 245 2060 760 1795 530 1625 405 1495 340 1295 245
0.50 2045 755 1785 530 1610 415 1470 350 1265 255 2030 775 1765 545 1585 425 1450 355 1255 265
0.60 2010 775 1740 545 1575 430 1440 370 1220 270 1995 785 1725 565 1550 435 1420 370 1205 275
0.70 1980 790 1705 565 1525 450 1400 375 1170 280 1960 795 1690 575 1505 455 1385 385 1165 290
0.80 1950 795 1670 580 1485 460 1360 390 1140 293 1895 790 1650 590 1465 470 1335 395 1120 295
ML196UH135XE60D PERFORMANCE (Less Filter)
External
Static
Pressure
in. w.g.
Air Volume / Watts at Di󰀨erent Blower Speeds
Bottom Return Air, Side Return Air with Return Air from
Both Sides or Return Air from Bottom and One Side.
Single Side Return Air − Air volumes in bold (over 1800
cfm) require Optional Return Air Base and eld fabricated
transition to accommodate 20 x 25 x 1 in. air lter in order to
maintain proper air velocity.
High Med-High Medium Med-Low Low High Med-High Medium Med-Low Low
cfm Watts cfm Watts cfm Watts cfm Watts cfm Watts cfm Watts cfm Watts cfm Watts cfm Watts cfm Watts
0.00 2400 920 2205 709 2035 513 1800 363 1625 268 2280 929 2100 703 1935 531 1720 368 1550 269
0.10 2370 930 2170 718 1985 524 1760 375 1585 279 2245 941 2075 720 1910 543 1700 380 1530 280
0.20 2345 937 2150 723 1960 552 1725 385 1535 291 2210 957 2050 745 1895 558 1695 396 1500 295
0.30 2305 958 2120 744 1920 565 1690 404 1505 305 2200 978 2030 757 1850 569 1675 408 1475 308
0.40 2275 974 2070 763 1885 576 1665 419 1475 323 2175 990 2015 774 1845 584 1640 427 1450 326
0.50 2230 986 2055 779 1845 593 1620 433 1435 330 2145 989 2010 783 1820 603 1605 446 1410 332
0.60 2195 988 2030 796 1810 614 1590 451 1385 348 2125 980 1990 809 1785 618 1580 455 1375 351
0.70 2125 961 1985 806 1780 626 1545 468 1355 359 2060 937 1960 819 1765 635 1545 474 1340 366
0.80 2065 931 1965 822 1760 642 1500 479 1310 377 1980 912 1925 825 1730 646 1510 491 1295 379

Page 7
ML196UHE PARTS IDENTIFICATION
FIGURE 1
TOP CAP
BURNER BOX
ASSEMBLY
DuralokPlusTM
HEAT EXCHANGER
ASSEMBLY
CONTROL BOX
(includes integrated ignition control, trans
former, circuit breaker and interlock switch)
COMBUSTION AIR
INDUCER
BURNER
ACCESS
PANEL
COMBUSTION
AIR PRESSURE
SWITCH
PRIMARY LIMIT
GAS VALVE
BLOWER
ASSEMBLY
FLEXIBLE NO-HUB
EXHAUST COLLAR
COLD END
HEADER BOX
BAG ASSEMBLIES
(shipping location)
BLOWER ACCESS
PANEL

Page 8
I-UNIT COMPONENTS
ELECTROSTATIC DISCHARGE (ESD)
Precautions and Procedures
CAUTION
Electrostatic discharge can affect elec
tronic components. Take precautions
to neutralize electrostatic charge by
touching your hand and tools to metal
prior to handling the control.
ML196UHE unit components are shown in figure 1. The
combustion air inducer, gas valve and burners can be ac
cessed by removing the outer access panel. The blower
and control box can be accessed by removing the blow
er access panel.
A-Control Box Components (Figure 2)
Unit transformer (T1) and integrated ignition control (A92)
are located in the control box. In addition, a door interlock
switch (S51) is located in the control box.
FIGURE 2
ML196UHE Control Box
Integrated Control
Door Interlock
Switch
Transformer
Circuit Breaker
1. Transformer (T1)
A transformer located in the control box provides power to
the low voltage section of the unit. The transformers on all
models are rated at 40VA with a 120V primary and 24V
secondary.
2. Door Interlock Switch (S51)
A door interlock switch rated 14A at 120VAC is located on
the control box. The switch is wired in series with line volt
age. When the blower door is removed the unit will shut
down.
3. Circuit Breaker (CB8)
A 24V circuit breaker is also located in the control box. The
switch provides overcurrent protection to the transformer
(T1). The breaker is rated at 3A at 32V. If the current ex
ceeds this limit the breaker will trip and all unit operation will
shutdown. The breaker can be manually reset by pressing
the button on the face.
4. Integrated Ignition Control (A92)
WARNING
Shock hazard.
Disconnect power before servicing. Control is not
field repairable. If control is inoperable, simply re
place entire control.
Can cause injury or death. Unsafe operation will re
sult if repair is attempted.
The hot surface ignition control system consisting of an in
tegrated control (figure 3 with control terminal designa
tions in tables 1, 2 and 3), sensor and ignitor (figure 5). The
integrated control and ignitor work in combination to en
sure furnace ignition and ignitor durability. The integrated
control, controls all major furnace operations. The inte
grated control also features a RED LED for troubleshoot
ing and two accessory terminals rated at (1) one amp. See
table 4 for troubleshooting diagnostic codes. The nitride
ignitor is made from a non-porous, high strength propri
etary ceramic material that provides long life and trouble
free maintenance.
TABLE 1
4-Pin Terminal Designation
PIN # FUNCTION
1Combustion Air Inducer Line
2Ignitor Line
3Combustion Air Inducer Neutral
4Ignitor Neutral
TABLE 2
12-Pin Terminal Designations
PIN # FUNCTION
1High Limit Output
2Not Used
324V Line
4Not Used
5Rollout Switch Out
624V Neutral
7High Limit Input
8 Ground
9Gas Valve Common
10 Pressure Switch In
11 Rollout Switch In
12 Gas Valve Out

Page 9
TABLE 3
1/4” QUICK CONNECT TERMINALS
120HUM Humidifier 120VAC
LINE 120VAC
XFMR Transformer 120VAC
CIRC Indoor blower 120VAC
EAC Indoor air quality accessory 120VAC
NEUTRALS Common 120VAC
HUM24 Humidifier 24VAC
3/16” QUICK CONNECT TERMINALS
COOL Cooling tap 24VAC
HEAT Heating tap 24VAC
FAN Continuous blower 24 VAC
PARK (no power) Park terminal for unused speed taps
FS Flame sense
24 COM Common 24VAC
TABLE 4
The integrated control is equipped with an LED light for troubleshooting. The diagnostic codes are listed below in table 4.
RED LED
Flash Code 2Diagnostic Codes / Status of Furnace
Off No power to control or board fault detected
Heartbeat
1
Normal Operation - Idle, Continuous Fan, Cool
Continuous Rapid
Flash Call For Heat / Burner Opertation
1Reverse Line Voltage Polarity
2Improper Earth Ground
3Burner failed to light, or lost flame during heat demand
4Low Flame Signal - check flame sensor
5Watchguard - burner failed to light, exceeded maximum number of retries or recycles.
6Not Used
7Primary or Secondary Limit Open or Watchguard Mode - Limit Switch Open longer than 3 min
utes
8Rollout Switch Open
9Pressure Switch failed to close or opened during heat demand
10 Watchguard - Pressure Switch opened 5 times during one heat demand
11 Pressure Switch stuck closed prior to activation of combustion air inducer
12 Flame Sensed without gas valve energized
13 Low Line Voltage
Notes
Note 1 A ”Heartbeat” is indicated by a ”Slow Flash” - 1 sec on 1 sec off, repeating
Note 2 Error codes are indicated by a ”Rapid Flash” - the LED flashes X times at 1/2 sec on 1/2 sec
off, remains off for 3 sec, then repeats
Note 3
Last 10 error codes are stored in memory including when power is shut off to the unit. - To recall,
press and release button, most recent will be displayed first, LED off for 3 sec, then next error
code is displayed, etc. To clear error codes, depress and hold button longer than 5 seconds.

Page 10
FIGURE 3
INTEGRATED CONTROL
(Automatic Hot Surface Ignition System)
BLOWER OFF DELAY
RED LED RECALL BUTTON
Electronic Ignition
On a call for heat the integrated control monitors the com
bustion air inducer pressure switch. The control board will
not begin the heating cycle if the pressure switch is closed
(by-passed). Once the pressure switch is determined to be
open, the combustion air inducer is energized. When the
differential in the pressure switch is great enough, the pres
sure switch closes and a 15-second pre-purge begins. If
the pressure switch is not proven within 2-1/2 minutes, the
integrated control goes into Watchguard-Pressure Switch
mode for a 5-minute re-set period.
After the 15-second pre-purge period, the ignitor warms up
for 20 seconds during which the gas valve opens at 19 sec
onds for a 4-second trial for ignition. The ignitor remains
energized for the first 3 seconds during the 4 second trial. If
ignition is not proved during the 4-second period, the inte
grated control will try four more times with an inter purge
and warm-up time between trials of 35 seconds. After a to
tal of five trials for ignition (including the initial trial), the inte
grated control goes into Watchguard-Flame Failure mode.
After a 60-minute reset period, the integrated control will
begin the ignition sequence again.
Fan Time Control
Heating Fan On Time
The fan on time of 30 seconds is not adjustable.
Heating Fan Off Time
Fan off time (time that the blower operates after the heat
demand has been satisfied) can be adjusted by moving the
jumper to a different setting. The unit is shipped with a fac
tory fan off setting of 90 seconds. For customized comfort,
monitor the supply air temperature once the heat demand
is satisfied. Note the supply air temperature at the instant
the blower is de-energized.
Adjust the fan-off delay to achieve a supply air temperature
between 90° - 110° at the instant the blower is de-ener
gized. (Longer delay times allow for lower air temperature,
shorter delay times allow for higher air temperature). See
figure 4.
Cooling Fan On Time
The fan on time is 2 seconds and is not adjustable.
Cooling Fan Off Time
The control has a 45 second fan off delay after cooling de
mand has been met. This delay is factory set and not ad
justable.
HEAT FAN‐OFF TIME IN SECONDS
To adjust fan-off timing, reposition jumper across pins to
achieve desired setting.
NO JUMPER
FIGURE 4
60 90
120
180
60 90
120
180
60 90
120
180
60 90
120
180
60 Second
off Time
90 Second
off Time
120 Second
off Time
180 Second
off Time

Page 11
FIGURE 5
ML196UHE Burner Box Assembly
Gas Valve
Burner Box Front
Rollout Switch(s)
Flame Sensor
Ignitor
Burner Assembly
B-Heating Components
Combustion air inducer (B6), primary limit control (S10), ig
nitor, burners, flame rollout switch (S47), gas valve (GV1),
combustion air pressure switch (S18), and heat exchangers
are located in the heating compartment. The heating
compartment can be accessed by removing the outer ac
cess panel.
1. Flame Rollout Switches (Figure 5)
Flame rollout switches S47 are SPST N.C. high temperature
limits located on the left and right of the front buner box plate.
S47 is wired to the burner ignition control A92. When ei
ther of the switches sense flame rollout (indicating a
blockage in the combustion passages), the flame rollout
switch trips, and the ignition control immediately closes
the gas valve. Switch S47 in all ML196UHE units is factory
preset to open at 210_F + 12_F (99_C + 6.7_C) on a tem
perature rise. All flame rollout switches are manual reset. See
table 4 flash code 8 for troubleshooting.
2. Heat Exchanger (Figure 6)
ML196UHE units use an aluminized steel primary and
stainless steel secondary heat exchanger assembly.
Heat is transferred to the air stream from all surfaces of
the heat exchanger. The shape of the heat exchanger en
sures maximum efficiency.
The combustion air inducer pulls fresh air through the burn
er box. This air is mixed with gas in the burners. The gas /
air mixture is then burned at the entrance of each clam
shell. Combustion gases are then pulled through the primary
and secondary heat exchangers and exhausted out the ex
haust vent pipe.
3. Primary Limit Control (Figure 6)
Primary limit (S10) used on ML196UHE units is located in the
heating vestibule panel. When excess heat is sensed in the
heat exchanger, the limit will open. Once the limit opens, the
furnace control energizes the supply air blower and de-en
ergizes the gas valve. The limit automatically resets when
unit temperature returns to normal. The switch is factory
set and cannot be adjusted. For limit replacement remove
wires from limit terminals, remove mounting screws, rotate
limit switch 90 degrees and slowly remove from the vesti
bule panel. Install replacement limit with same care. See
table 4 flash code 7 for troubleshooting if limit switch
opens during operation.

Page 12
FIGURE 6
Primary Limit Location and Heat Exchanger
Install limit face down
4. Gas Valve (Figure 7)
The ML196UHE uses an internally redundant valve to assure
safety shut‐off. If the gas valve must be replaced, the same
type valve must be used.
24VAC terminals and gas control switch are located on
top of the valve. All terminals on the gas valve are con
nected to wires from the ignition control. 24V applied to the
terminals opens the valve.
Inlet and outlet pressure taps are located on the valve. A
manifold adjustment screw is also located on the valve. An
LP/Propane changeover kit is available.
FIGURE 7
GAS VALVE SHOWN IN ON POSITION
MANIFOLD
PRESSURE
OUTLET
PORT
INLET
PRESSURE
PORT
MANIFOLD PRESSURE
ADJUSTMENT SCREW
(under barbed fitting)
5. Flame Sensor (Figure 5)
A flame sensor is located on the left side of the burner sup
port. The sensor is mounted on the front burner box plate
and the tip protrudes into the flame envelope of the left-
most burner. The sensor can be removed for service (use
steel wool only to clean) without removing any part of the
burners. During operation, flame is sensed by current
passed through the flame and sensing electrode. The igni
tion control allows the gas valve to remain open as long as
flame signal is sensed.
NOTE - The ML196UHE is polarity sensitive. Make sure
that the furnace is wired correctly and is properly grounded.
A microamp DC meter is needed to check the flame signal
on the integrated control.
Flame (microamp) signal is an electrical current which passes
from the integrated control to the sensor during unit operation.
Current passes from the sensor through the flame to ground to
complete a safety circuit.
To Measure Flame Signal - Integrated Control:
Use a digital readout meter capable of reading DC micro
amps. See figure 8 for flame signal check.
1 - Set the meter to the DC amps scale.
2 - Turn off supply voltage to control.
3 - Remove sensor wire from integrated control.
4 - Connect (-) lead to flame sensor wire.
5 - Connect (+) lead to Terminal FS on integrated control.
6 - Turn supply voltage on and close thermostat contacts to
cycle system.
7 - When main burners are in operation for two minutes, take
reading.
6. Ignitor (Figure 5)
ML196UHE units use a nitride ignitor made from a propri
etary ceramic material. To check ignitor, measure its resist
ance and voltage. A value of 39 to 70 ohms indicates a
good ignitor. Voltage to the ignitor should be 102 - 132VAC.
See figure 9 for resistance and voltage checks.

Page 13
FIGURE 8
Measuring Flame Signal
Flame Signal In Microamps
Normal Low Drop Out
1.5 0.5 - 1.4 0.4
Set Dial to DC MicroAmps
(+)
Multi−Meter
(+)
(+) To Control
Sensor Terminal
(−) To Flame
Terminal
Flame Sensor
Terminal
Flame Sensor
Wire
Intergrated
Control
Remove sensor from integrated
control and connect alligator clip
(−) to flame sensor lead.
Remove sensor from integrated
control and connect alligator clip
(+) to terminal on control.

Page 14
FIGURE 9
Test 1
Check ignitor circuit for correct resistance.
Remove 4-pin plug from control.
Check ohms reading across terminals 2 and 4.
Reading should be between 39 and 70 ohms. If
value is correct, this is the only test needed.
If the reading on the meter is not correct, (0 or
infinity) then a second test is needed.
Test 2
Check ignitor for correct resistance.
Seperate the 2-pin jack-plug near the manifold and check
resistance of ignitor at the plug. Reading should be
between 39 and 70 ohms. If the reading is correct, then
the problem is with the wiring between the jack-plug and
the control. If reading is not correct, the issue is the ignitor.
Test 3
Check ignitor for correct voltage
Insert meter probes into terminals 2 and 4 (use small
diameter probes in order not to damage plug).
Check voltage during 20 second ignitor warm up period.
Voltage should read 120 volts + 10%. If voltage reads below
these values, check for correct supply voltage to furnace.
Multi−Meter
(set to ohms)
Multi−Meter
(set to ohms)
Multi−Meter
(set to VAC)

Page 15
7. Combustion Air Inducer (B6)
& Cold End Header Box
All ML196UHE units use a combustion air inducer to
move air through the burners and heat exchanger during
heating operation. The blower uses a shaded pole
120VAC motor. The motor operates during all heating op
eration and is controlled by integrated control A92. Blower
operates continuously while there is a call for heat. The in
tegrated control will not proceed with the ignition sequence
until combustion air inducer operation is sensed by the prov
ing switches.
The combustion air inducer 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 pres
sure at unit start up. The channel contains an orifice used
to regulate flow created by the combustion air inducer.
The box has pressure taps for the combustion air inducer
pressure switch hoses. The pressure switch measures
the pressure across the combustion air inducer orifice or
difference in the channel and the box. If replacement is
necessary the gaskets used to seal the box to the
vestibule panel and the combustion air inducer to
the box, must also be replaced.
TABLE 5
ML196UHE Unit Combustion Air Inducer
Orifice Size
-030 0.525”
-045 0.618”
-070 0.775”
-090 0.905”
-110 1.040”
-135 1.235”
8. Combustion Air Pressure Switch
(Figure 10)
ML196UHE series units are equipped with a differential
pressure switch located on the cold end header box. The
switch monitors across the combustion air inducer orifice to in
sure proper flow through the heat exchanger.
The switch is a SPST N.O. pressure switch electrically con
nected to the integrated control. The purpose of the switch is
to prevent burner operation if the combustion air inducer is not
moving enough air for proper combustion.
FIGURE 10
Pressure Switch
On start‐up, the switch monitors whether the combustion air
inducer is operating. It closes a circuit to the integrated
control when the difference in pressure across the com
bustion air inducer orifice exceeds a non-adjustable factory
setting. If the switch does not successfully sense the re
quired differential, the switch cannot close and the fur
nace cannot operate. If the flue or air inlet become ob
structed during operation, the switch senses a loss of
pressure differential and opens the circuit to the integrated
control. If the condensate line is blocked, water will back up
into the header box and reduce the pressure differential
across the switch. The pressure switch opens if the differ
ential drops below the set point. See table 6.
Checks of pressure differential can aid in troubleshooting.
When measuring the pressure differential, readings should be
taken at the pressure switch. See figure 11and table 7. Lack of
differential usually indicates problems in the intake or exhaust
piping, but may indicate problems in the heat exchanger,
condensing coil, header boxes, combustion inducer or
other components.
TABLE 6
Unit
Altitude ft.
0 - 4500 4501 - 7500 7501 - 10000
Set Point “w.c. Set Point “w.c Set Point “w.c.
-030 -0.65 -0.65 -0.60
-045 -0.65 -0.65 -0.60
-070 -0.95 -0.85 -0.75
-090 -0.90 -0.80 -0.65
-110 -0.90 -0.85 -0.65
-135 -0.90 -0.80 -0.65
*Set point is factory set and non-adjustable

Page 16
To Cold End Header Box
Field Provided Tubing
To Pressure Switch
To Cold End Header Box
FIGURE 11
1 - Remove thermostat demand and allow unit to
cycle off.
2 - Install a tee in the negative (-) line (red and black tubing
or red tubing) and a tee in the positive (+) line (black
tubing) running from the pressure switch to the cold
end header box.
3 - Install a manometer with hose from the negative (-)
side of the manometer to the tee installed in the
negative (-) line and with hose from the positive (+)
side of the manometer to the tee in the positive (+)
line.
NOTE - Both sides of the cold end header box are nega
tive. However the (+) port reads less negative pressure
than the (-) port.
4 - Operate unit and observe manometer reading.
Readings will change as heat exchanger warms.
a. Take one reading immediately after start‐up.
b. Take a second reading after unit has reached
steady state (approximately 5 minutes). This will be
the pressure differential.
The pressure differential should be greater
than those listed in table 6.
5 - Remove thermostat demand and allow to cycle off.
6 - Remove manometer and tee's. Reinstall combustion
air sensing hoses to the pressure switch.
Measuring Pressure Differential
Black Tubing
(positive +)
Red and Black Tubing
or Red Tubing
(negative -)
“+”
High
“-”
Low

Page 17
TABLE 7
Pressure Switch Troubleshooting Guide
Problem Corrective Action
Pressure switch stuck closed Check that the pressure switch is open without the combustion air inducer operat
ing. Replace if defective.
Pressure switch does not close due to
obstruction in vent pipe.
Check for restricted vent. Remove all blockage.
Check for proper vent sizing. See table 12.
Pressure switch does not close due to
incorrect routing of the pressure
switch tubing.
Check that the pressure switch tubing is correctly routed. Correctly route pressure
witch line.
Pressure switch does not close due to
obstructions in the pressure switch
line.
Remove any obstructions from the the pressure switch line and/or taps
Pressure switch tubing damaged. Check pressure switch tubing for leaks. Replace damaged tubing if necessary.
Condensate in pressure switch tubing. Check pressure switch tubing for condensate. Remove condensate from tubing.
Pressure switch does not close due to
a low differential pressure across the
pressure switch.
Check the differential pressure across the pressure switch.
Check for restricted inlet vent. Remove all blockage.
Check for proper vent sizing and run length. See table12.
Wrong pressure switch installed in the
unit, or pressure switch is out of cal
ibration
Check that the correct pressure switch is installed in the unit. Replace pressure
switch if necessary.
Miswiring of furnace or improper con
nections at pressure switch.
Check for correct wiring and loose connections. Correct wiring and/or replace any
loose connections.
Pressure switch failure. If all the above modes of failure have been checked, the pressure switch may have
failed. Replace pressure switch and determine if unit will operate.
Damaged condensate trap. Check trap for any cracks or damage and replace if necessary.
Cold end header box does not drain
properly.
Check that the furnace is set properly with a slight tilt (0 - 1/2”) towards the front
if necessary. See furnace installation instruction.
Air leakage around the combustion air
inducer gasket. Check gasket and replace if necessary.
Air leakage around the cold end head
er box gasket. Check gasket and replace if necessary.
Damaged cold end header box tubing. Check tubing and replace if necessary.
ÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉ
ÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉ
ÉÉÉÉÉÉÉÉÉÉÉÉÉÉ
É
É
DEMAND
CAI
GAS VALVE
15
ON
OFF
ÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉ
É
É
38
ÉÉÉÉÉÉÉÉÉÉ
ÉÉÉÉÉÉÉÉÉÉ
IGNITOR
341
Pre -Purge Ignitor Warm-up Trial for
Ignition Post
Purge
5 SEC80
*Blower on time will be 30 seconds after flame is sensed. Blower off time will depend on “OFF TIME” Setting.
INDOOR BLOWER
ÉÉÉÉÉÉÉÉÉ
ÉÉÉÉÉÉÉÉÉ
Blower “On”*
Delay
ELECTRONIC IGNITION
FIGURE 12

Page 18
C- Blower Compartment
IMPORTANT
Each blower is statically and dynamically balanced
as an assembly before installation in the unit.
ML196UHE units are equipped with a constant torque ECM
motor. It has a DC motor coupled to an electronic control
module both contained in the same motor housing. The mo
tor is programmed to provide constant torque at each of the
five selectable speed taps. Each tap requires 24 volts to en
ergize.
Input Voltage Requirements
The circuit is designed to be operated with AC voltage. To
enable a tap requires 12 to 33VAC. Expected current draw
will be less than 20mA.
Troubleshooting the Motor
Troubleshooting the motor is an easy process. Follow
steps below.
1- Shut off power to unit.
2- Remove input plugs P48 and P49 from motor. See
figure 16 for troubleshooting procedure.
If correct voltage is present in tests 1 and 2 and motor is not
operating properly, replace motor. The motor is not field re
pairable.
If replacing the indoor blower motor or blower wheel is nec
essary, placement is critical. The blower wheel must be cen
tered in the blower housing as shown in figure 13. When re
placing the indoor blower motor the set screw must be
aligned and tightened with the motor shaft as shown in figure
14.
9. Secondary Limit Controls
The secondary limit is located in the blower compartment on
the back side of the blower housing. See figure 15. When ex
cess heat is sensed in the blower compartment, the limit will
open. If the limit is open, the furnace control energizes the sup
ply air blower and closes the gas valve. The limit automatically
resets when unit temperature returns to normal. The secon
dary limit cannot be adjusted.
FIGURE 13
Center Blower Wheel
in Blower Housing
BLOWER WHEEL REPLACEMENT
FIGURE 14
Set Screw
Housing Hub
ALIGN AND TIGHTEN SET SCREW WITH
FLAT SIDE OF MOTOR SHAFT
Motor
Shaft
FIGURE 15
SECONDARY LIMIT CONTROL
Secondary Limits

Page 19
1
2
3
4
5
C
L
G
N
Multi−Meter
(set to VAC)
P48
P49
120 120
Turn on power to unit. Check for 120 volts across terminals
“L” and “N” on input plug P48. If voltage is present continue
to test 2. If voltage is not present problem may be may be up
stream of plug P48 and proceed to test 3.
1
2
3
4
5
C
L
G
N
Multi−Meter
(set to VAC)
P48
P49 24
Switch thermostat to CONTINUOUS FAN MODE. Check for
24 volts across terminal “C” on input plug P48and speed tap
used for continuous fan. (1, 2, 3, 4 or 5) on input plug P49. If
24 volts is not present problem may be up stream of plug P49.
Proceed to test 4.
Multi−Meter
(set to VAC)
120 120
24
Multi−Meter
(set to VAC)
Check for 24 volts across terminals “24 COM” and “FAN” ter
minals on the integrated control. If voltage is present, prob
lem is with the harness. If voltage is not present problem
may be may be with the integrated control
Check for 120 volts across terminals “CIRC” and “Neutrals”
on the integrated control. If voltage is present, problem is
with the harness. If voltage is not present problem may be
may be with the integrated control.
Test 1
Test 2
Test 3 (if necessary)
Test 4 (if necessary)
FIGURE 16

12
3
4
5
6
7
8
9
10
11 12
1/16
TURN
Page 20
Replacing the Motor Module
1. Disconnect electrical power to unit.
2. Remove unit access panel.
3. Unplug the two harnesses from the motor control mod
ule. See figure 17.
TWO HARNESS
CONNECTIONS
MOTOR CONTROL MODULE
MOTOR
FIGURE 17
Unplug the Two Harness Connection
4. Remove the two hex head bolts securing the motor
control module to the motor (see figure 18).
REMOVE BOTH HEX
HEAD BOLTS
FIGURE 18
Remove the Hex Head Bolts
5. Slide the motor control module away from the motor to
access and disconnect the internal three wire connec
tor. It is not necessary to remove blower motor itself.
Set both hex head bolts aside.
Testing the Motor (Figure19)
If any motor fails the below tests, do not install the new con
trol module. The motor is defective and it also must be re
placed. The new control can fail if placed on a defective mo
tor.
1. Using an ohmmeter check the resistance from any one
of the motor connector pins to the aluminum end plate
of the motor. This resistance should be greater than
100k ohms.
2. Check the resistances between each of the three mo
tor connector pins. These should all read approxim
ately the same resistance within an ohm.
3. Check to see if the blower wheel spins freely.
FIGURE 19
Motor Test
TABLE 8
Scale Measurement range in
words ohms
2 M two megohm-two million
ohms 0 - 2,000,000
200 K two hundred kilo-ohm-two
hundred thousand ohms 0 - 200,000
20 K twenty kilo-ohm-twenty
thousand ohms 0 - 20,000
2 K two kilo-ohm two-thousand
ohms 0 - 2,000
200 two hundred ohms 0 - 200
Motor Module Installation
All replacement motor control modules look similar; how
ever, each module is designed for a specific motor size. It is
very important to make sure that you are using the correct
replacement motor control module. USE OF THE WRONG
MOTOR CONTROL MODULE MAY RESULT IN UNEX
PECTED UNIT OPERATION.
1. Verify electrical power to unit is disconnected.
2. Connect three-wire harness from motor to control
module.
3. Mount new motor control module
to motor using two hex head bolts
removed in figure 18. Torque bolts
to 22 inch pounds or 1/16th clock
turn as exampled to the right.
4. Reconnect the two harnesses to
the motor control module.
5. The electrical connectors of the motor should be facing
down to form a drip loop (figure20). This will directs
moisture away from the motor and its electric connec
tions on the motor.
CONNECTOR
ORIENTATION
BETWEEN 4 AND 8
O'CLOCK
BACK OF CONTROL
MODULE
DRIP LOOP
FIGURE 20
Drip Loop