Lennox ML180UHE User manual

Page 1
UNIT INFORMATIONUNIT INFORMATION
Service Literature
©2016 Lennox Industries, Inc.
WARNING
Electric Shock Hazard. Can cause injury
or death. Unit must be properly grounded
in accordance with national and local
codes.
Line voltage is present at all components
when unit is not in operation on units
with single-pole contactors. Disconnect
all remote electric power supplies before
opening access panel. Unit may have
multiple power supplies.
CAUTION
As with any mechanical equipment, contact with
sharp sheet metal edges can result in personal
injury. Take care while handling this equipment and
wear gloves and protective clothing.
ML180UHE(X) series units are mid-e󰀩ciency gas furnac-
es used for upow or horizontal applications only, man-
ufactured with Lennox Duralok heat exchangers formed
of aluminized steel. ML180UHE(X) units are available in
heating capacities of 44,000 to 132,000 Btuh and cooling
applications 2 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 LP/Propane operation.
ML180UHE(X) model units are equipped with a hot sur-
face ignition system. The ML180UHE(X) unit meets the
California Nitrogen Oxides (NOx) Standards and Califor-
nia Seasonal E󰀩ciency requirements.
All units use a redundant gas valve to assure safety shut-
o󰀨 as required by C.S.A. All specications in this manual
are subject to change. Procedures outlined in this manual
are presented as a recommendation only and do not su-
persede 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 recom-
mended only and do not constitute code.
WARNING
Improper installation, adjustment, alteration,
service or maintenance can cause property damage,
personal injury or loss of life. Installation and service
must be performed by a licensed professional HVAC
installer (or equivalent), service agency or the gas
supplier.
TABLE OF CONTENTS
Specications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Page 2
Blower Data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Page 4
Parts Identication . . . . . . . . . . . . . . . . . . . . . . . . . Page 6
I Unit Components . . . . . . . . . . . . . . . . . . . . . . . . Page 7
II Installation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Page 21
III Start Up . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Page 21
IV Heating System Service Checks . . . . . . . . . Page 21
V Typical Operating Characteristics . . . . . . . . . Page 26
VI Maintenance . . . . . . . . . . . . . . . . . . . . . . . . . . Page 26
VII Wiring and Sequence of Operation . . . . . . Page 29
ML180UHE(X)
Corp 1120-L4
Revised 10-2017
ML180UHE(X) SERIES UNITS

Page 2
SPECIFICATIONS
Gas
Heating
Performance
Model No. ML180UH045E36A ML180UH070E36A ML180UH070E36B ML180UH090E48B
Model No. - Low Nox ML180UH045XE36A ML180UH070XE36A ML180UH070XE36B ML180UH090XE48B
1AFUE 80% 80% 80% 80%
Input - Btuh 44,000 66,000 66,000 88,000
Output - Btuh 36,000 53,000 53,000 72,000
Temperature rise range - °F 15 - 45 40 - 70 40 - 70 35 - 65
Gas Manifold Pressure (in. w.g.)
Nat. Gas / LPG/Propane
3.5 / 10.0 3.5 / 10.0 3.5 / 10.0 3.5 / 10.0
High Static - in. w.g. 0.50 0.50 0.50 0.50
Connections
in.
Flue connection - in. round 4 4 4 4
Gas pipe size IPS 1/2 1/2 1/2 1/2
Indoor
Blower
Wheel nom. dia. x width - in. 10 x 8 10 x 10 10 x 10 10 x 10
Motor Type DC Brushless DC Brushless DC Brushless DC Brushless
Motor output - hp 1/2 1/2 1/2 3/4
Tons of add-on cooling 1.5 - 3 1.5 - 3 1.5 - 3 2.5 - 4
Air Volume Range - cfm 350 - 1380 625 - 1435 395 - 1415 750 - 1785
Electrical
Data
Voltage 120 volts - 60 hertz - 1 phase
Blower motor full load amps 6.8 6.8 6.8 8.4
Maximum overcurrent protection 15 15 15 15
Shipping Data lbs. - 1 package 111 111 127 142
SPECIFICATIONS
Gas
Heating
Performance
Model No. ML180UH090E60C ML180UH110E60C ML180UH135E60D
Model No. - Low Nox - - - ML180UH110XE60C - - -
1AFUE 80% 80% 80%
Input - Btuh 88,000 110,000 132,000
Output - Btuh 72,000 90,000 107,000
Temperature rise range - °F 30 - 60 35 - 65 30 - 60
Gas Manifold Pressure (in. w.g.)
Nat. Gas / LPG/Propane
3.5 / 10.0 3.5 / 10.0 3.5 / 10.0
High Static - in. w.g. 0.50 0.50 0.50
Connections
in.
Flue connection - in. round 4 4 4
Gas pipe size IPS 1/2 1/2 1/2
Indoor
Blower
Wheel nom. dia. x width - in. 11-1/2 x 10 11-1/2 x 10 11 x 11
Motor Type DC Brushless DC Brushless DC Brushless
Motor output - hp 111
Tons of add-on cooling 3 - 5 3 - 5 3.5 - 5
Air Volume Range - cfm 990 - 2290 920 - 2315 1140 - 2495
Electrical
Data
Voltage 120 volts - 60 hertz - 1 phase
Blower motor full load amps 10.9 10.9 10.9
Maximum overcurrent protection 15 15 15
Shipping Data lbs. - 1 package 152 160 178
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 - ORDER SEPARATELY
“A” Width
Models
“B” Width
Models
“C” Width
Models
“D” Width
Models
CABINET ACCESSORIES
Horizontal Suspension Kit - Horizontal only 51W10 51W10 51W10 51W10
Return Air Base - Upow only 65W75 50W98 50W99 51W00
High Performance Economizer (Commercial Only) 10U53 10U53 10U53 10U53
CONTROLS
iComfort®M30 Smart Wi-Fi Thermostat 15Z69 15Z69 15Z69 15Z69
Remote Outdoor Air Temperature Sensor X2658 X2658 X2658 X2658
Blower Relay Kit (for two-stage outdoor units) 85W66 85W66 85W66 85W66
Furnace Twinning Kit 16W72 16W72 16W72 16W72
FILTERS
1Air Filter and Rack Kit Horizontal (end) 87L95 87L96 87L97 87L98
Size of lter - in. 14 x 25 x 1 18 x 25 x 1 20 x 25 x 1 25 x 25 x 1
Side Return Single 44J22 44J22 44J22 44J22
Ten Pack 66K63 66K63 66K63 66K63
Size of lter - in. 16 x 25 x 1 16 x 25 x 1 16 x 25 x 1 16 x 25 x 1
NIGHT SERVICE KIT
Night Service Kit 84W47 84W47 84W47 84W47
VENTING
Vent Adaptor − 6 in. conn. size upow applications only 18M79 18M79 18M79 18M79
1 Cleanable polyurethane, frame-type lter.
GAS HEAT ACCESSORIES
Input
High Altitude
Pressure Switch Kit
Natural Gas to
LPG/Propane Kit
LPG/Propane
to Natural Gas Kit
Natural Gas
High Altitude
Orice Kit
0 - 4500 ft. 4501 - 7500 ft. 7501 - 10,000 ft. 0 - 7500 ft. 7501 - 10,000 ft. 0 - 7500 ft. 7501 - 10,000 ft.
045 No Change 80W52 80W51 11K49 11K44 73W81 73W37
070 No Change 80W52 80W51 11K49 11K44 73W81 73W37
090 No Change 80W52 80W51 11K49 11K44 73W81 73W37
110 No Change 80W52 80W52 11K49 11K44 73W81 73W37
135 No Change 80W52 80W51 11K49 11K44 73W81 73W37
NOTE - Units may be installed at altitudes up to 2000 ft. above sea level without any modications.
At altitudes above 2000 ft. units must be derated to match information in the shaded areas shown below.
NOTE - This is the only permissible derate for these units.
Input
Gas Manifold Pressure (Outlet) in. w.g. Line Pressure - in. w.g.
0 - 2000 Feet 2001 - 4500 Feet 4501 - 7500 Feet 7501 - 10,000 ft. Minimum
Maximum
Natural
Gas
LPG/
Propane
Natural
Gas
LPG/
Propane
Natural
Gas
LPG/
Propane
1Natural
Gas
LPG/
Propane
Natural
Gas
LPG/
Propane
045 3.5 10 3.2 10 310 3.5 10 4.5 11 13
070 3.5 10 3.2 10 2.8 10 3.5 10 4.5 11 13
090 3.5 10 3.2 10 2.7 9.6 3.5 10 4.5 11 13
110 3.5 10 3.5 10 3 9.6 3.5 10 4.5 11 13
135 3.5 10 3.5 10 2.9 9.6 3.5 10 4.5 11 13
1 Natural Gas High Altitude Orice Kit required.
HIGH ALTITUDE

Page 4
BLOWER DATA
ML180UH045E36A PERFORMANCE (Less Filter)
External
Static
Pressure
in. w.g.
Air Volume / Watts at Various Blower Speeds
High
(Black)
Medium-High
(Brown)
Medium
(Blue)
Medium-Low
(Yellow)
Low
(Red)
cfm Watts cfm Watts cfm Watts cfm Watts cfm Watts
0.00 1380 265 1155 165 995 120 975 115 945 105
0.10 1345 270 1120 175 950 120 880 105 865 100
0.20 1320 285 1080 190 900 125 805 105 700 85
0.30 1290 295 1055 200 875 135 750 110 640 90
0.40 1265 310 1010 205 825 145 710 120 595 95
0.50 1230 315 990 215 790 155 660 125 535 100
0.60 1190 330 945 230 750 165 630 135 500 110
0.70 1165 340 915 235 705 170 570 140 435 115
0.80 1130 350 880 245 670 180 535 150 380 120
ML180UH070E36B PERFORMANCE (Less Filter)
External
Static
Pressure
in. w.g.
Air Volume / Watts at Various Blower Speeds
High
(Black)
Medium-High
(Brown)
Medium
(Blue)
Medium-Low
(Yellow)
Low
(Red)
cfm Watts cfm Watts cfm Watts cfm Watts cfm Watts
0.00 - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
0.10 1415 280 1295 170 1145 145 1130 130 955 95
0.20 1355 290 1225 185 1110 150 1080 140 885 100
0.30 1330 300 1190 200 1060 160 1035 155 825 110
0.40 1290 310 1155 205 1015 175 970 160 770 120
0.50 1245 325 1115 215 980 180 930 170 695 125
0.60 1225 335 1045 230 920 190 865 180 625 135
0.70 1190 350 1000 235 855 205 790 190 540 140
0.80 1160 365 925 245 790 205 735 200 445 145
ML180UH070E36A PERFORMANCE (Less Filter)
External
Static
Pressure
in. w.g.
Air Volume / Watts at Various Blower Speeds
High
(Black)
Medium-High
(Brown)
Medium
(Blue)
Medium-Low
(Yellow)
Low
(Red)
cfm Watts cfm Watts cfm Watts cfm Watts cfm Watts
0.00 - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
0.10 1435 282 1215 178 1120 147 1095 133 930 88
0.20 1400 290 1170 187 1090 154 1050 141 875 98
0.30 1365 303 1145 198 1055 164 1025 153 845 102
0.40 1335 311 1105 206 1015 172 985 160 795 110
0.50 1310 325 1075 216 980 177 945 169 760 117
0.60 1285 341 1040 224 950 187 905 175 705 125
0.70 1250 344 1010 235 905 196 865 183 665 129
0.80 1215 354 975 244 860 204 830 191 625 136
ML180UH090E48B PERFORMANCE (Less Filter)
External
Static
Pressure
in. w.g.
Air Volume / Watts at Various Blower Speeds
High
(Black)
Medium-High
(Brown)
Medium
(Blue)
Medium-Low
(Yellow)
Low
(Red)
cfm Watts cfm Watts cfm Watts cfm Watts cfm Watts
0.00 1785 380 1570 270 1440 220 1395 190 1190 120
0.10 1755 395 1535 275 1420 230 1350 205 1140 130
0.20 1730 415 1505 290 1380 245 1310 215 1110 145
0.30 1690 435 1460 305 1345 260 1275 230 1065 155
0.40 1645 440 1435 320 1310 270 1240 240 1010 165
0.50 1615 455 1395 335 1265 285 1180 255 955 180
0.60 1590 470 1350 350 1210 290 1150 265 915 185
0.70 1545 475 1300 360 1175 305 1095 275 860 200
0.80 N/A N/A 1270 370 1140 310 1040 285 820 210

Page 5
ML180UH110E60C 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
(Black)
Medium-
High
(Brown)
Medium
(Blue)
Medium-
Low
(Yellow)
Low
(Red)
High
(Black)
Medium-
High
(Brown)
Medium
(Blue)
Medium-
Low
(Yellow)
Low
(Red)
cfm Watts cfm Watts cfm Watts cfm Watts cfm Watts cfm Watts cfm Watts cfm Watts cfm Watts cfm Watts
0.00 2230 635 1945 430 1715 295 1555 230 1470 185 2315 645 1990 415 1780 300 1610 230 1510 200
0.10 2180 655 1905 445 1690 305 1510 240 1340 175 2260 655 1945 425 1740 315 1550 240 1400 185
0.20 2135 680 1865 465 1630 330 1470 260 1280 190 2210 680 1895 450 1680 335 1510 255 1350 200
0.30 2090 695 1830 480 1595 345 1440 275 1235 200 2165 700 1850 465 1650 355 1455 275 1285 210
0.40 2050 715 1785 495 1550 360 1385 285 1175 210 2130 715 1830 485 1585 365 1395 285 1230 225
0.50 2025 730 1740 520 1500 375 1340 300 1130 225 2095 730 1770 500 1535 385 1365 300 1175 235
0.60 2010 750 1710 535 1470 390 1305 320 1080 240 2055 755 1725 515 1495 400 1305 315 1135 250
0.70 1965 755 1670 555 1420 410 1255 330 1015 255 2000 765 1675 535 1465 410 1255 325 1080 265
0.80 1905 785 1635 560 1380 425 1215 350 975 270 1965 785 1640 555 1400 425 1210 345 1025 275
ML180UH090E60C PERFORMANCE (Less Filter)
External
Static
Pressure
in. w.g.
Air Volume / Watts at Di󰀨erent Blower Speeds
Bottom Return Air, Side 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
(Black)
Medium-
High
(Brown)
Medium
(Blue)
Medium-
Low
(Yellow)
Low
(Red)
High
(Black)
Medium-
High
(Brown)
Medium
(Blue)
Medium-
Low
(Yellow)
Low
(Red)
cfm Watts cfm Watts cfm Watts cfm Watts cfm Watts cfm Watts cfm Watts cfm Watts cfm Watts cfm Watts
0.00 2255 640 1940 420 1750 310 1580 230 1485 185 2290 655 1980 425 1775 310 1605 235 1495 195
0.10 2200 655 1910 440 1705 315 1535 240 1385 190 2250 675 1945 445 1730 320 1555 245 1400 190
0.20 2150 675 1865 450 1655 340 1490 260 1340 205 2210 695 1885 465 1680 340 1510 265 1350 205
0.30 2125 695 1835 475 1635 355 1450 275 1285 215 2165 715 1850 475 1645 355 1470 275 1285 215
0.40 2090 715 1800 495 1585 370 1405 285 1235 230 2135 720 1810 490 1595 370 1410 290 1225 230
0.50 2060 735 1760 510 1545 385 1370 305 1200 245 2070 735 1765 515 1545 390 1370 305 1180 245
0.60 2020 750 1725 525 1515 405 1320 320 1145 255 2030 760 1715 530 1495 405 1325 320 1140 255
0.70 1980 765 1680 540 1465 420 1265 330 1105 270 1990 775 1685 540 1450 425 1265 330 1095 270
0.80 1935 785 1635 560 1420 435 1225 350 1055 285 1950 795 1645 560 1415 435 1225 345 1040 285
ML180UH135E60D 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
(Black)
Medium-
High
(Brown)
Medium
(Blue)
Medium-
Low
(Yellow)
Low
(Red)
High
(Black)
Medium-
High
(Brown)
Medium
(Blue)
Medium-Low
(Yellow)
Low
(Red)
cfm Watts cfm Watts cfm Watts cfm Watts cfm Watts cfm Watts cfm Watts cfm Watts cfm Watts cfm Watts
0.00 2495 755 2295 590 2045 435 1845 315 1650 230 2365 725 2295 575 2005 410 1820 300 1635 235
0.10 2440 780 2220 620 2015 445 1820 330 1615 245 2350 745 2210 595 2000 435 1745 320 1530 230
0.20 2390 790 2175 640 1935 470 1735 350 1550 255 2330 775 2175 625 1945 455 1730 330 1490 250
0.30 2360 805 2140 655 1895 490 1720 370 1485 275 2245 785 2135 645 1895 475 1655 355 1425 265
0.40 2285 835 2125 675 1850 510 1660 380 1455 290 2215 810 2085 660 1840 495 1600 375 1385 285
0.50 2240 860 2060 690 1815 535 1610 400 1415 310 2175 825 2045 680 1815 505 1590 390 1340 290
0.60 2225 865 2015 715 1785 550 1535 420 1330 320 2125 845 1995 700 1765 530 1525 405 1300 310
0.70 2160 895 1955 735 1755 570 1500 440 1265 340 2095 865 1950 710 1700 545 1485 420 1260 325
0.80 2105 905 1925 750 1715 580 1435 450 1215 345 2065 880 1890 725 1680 565 1415 445 1205 345

Page 6
Control Box
(includes integrated control,
interlock switch and transformer)
Gas Valve
Burner Box
(includes sensor, ignitor
and rollout switches)
Combustion Air Inducer
Combustion Air Inducer
Pressure Switch
Heat Exchanger
Upper Access Panel
Blower Access Panel
Primary Limit
(under
combustion
air inducer)
Make-Up Box
Blower Assembly
Power Choke
(4 and 5 Ton Only)
PARTS ARRANGEMENT
FIGURE 1

Page 7
I-UNIT COMPONENTS
ML180UHE(X) unit components are shown in gure 1.The
gas valve, combustion air inducer and burners can be ac-
cessed by removing the upper access panel. Electrical
components are in the control box (gure 2) found in the
blower section.
ELECTROSTATIC DISCHARGE (ESD)
Precautions and Procedures
CAUTION
Electrostatic discharge can a󰀨ect
electronic components. Take precautions
to neutralize electrostatic charge by
touching your hand and tools to metal
prior to handling the control.
1. Control Transformer (T1)
A transformer located in the control box provides power to
the low voltage section of the unit. Transformers on all
models are rated 40VA with a 120V primary and a 24V
secondary.
2. Door Interlock Switch (S51)
A door interlock switch rated 14A at 125VAC is wired in
series with line voltage. When the blower door is removed
the unit will shut down.
NOTE - The door interlock switch is a safety switch. Do
not by-pass or jumper switch.
CONTROL BOX
DOOR INTERLOCK
SWITCH (S51)
INTEGRATED IGNITION
CONTROL
(A92)
TRANSFORMER
(T1)
CIRCUIT
BREAKER
(CB8)
FIGURE 2
3. Circuit Breaker (CB8)
A 24V circuit breaker is also located in the control box. The
switch provides overcurrent protection to the transform-
er (T1). The breaker is rated at 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 by
pressing the button on the face.
4. Integrated Control (A92)
WARNING
Shock hazard.
Disconnect power before servicing. Control is not
eld repairable. If control is inoperable, simply
replace entire control.
Can cause injury or death. Unsafe operation will
result if repair is attempted.
The hot surface ignition control system consisting of an in-
tegrated control (gure 3 with control terminal designations
in tables 1, 2 and 3), sensor and ignitor (gure 6). The in-
tegrated control and ignitor work in combination to ensure
furnace ignition and ignitor durability. The integrated con-
trol, controls all major furnace operations. The integrated
control also features a RED LED for troubleshooting and
two accessory terminals rated at (1) one amp. See table 4
or 5. for troubleshooting diagnostic codes. The nitride ig-
nitor is made from a non-porous, high strength proprietary
ceramic material that provides long life and trouble free
maintenance.
Electronic Ignition (Figure 4)
On a call for heat the integrated control monitors the com-
bustion air inducer pressure switch. The control will not
begin the heating cycle if the pressure switch is closed
(bypassed). Once the pressure switch is determined to
be open, the combustion air inducer is energized. When
the di󰀨erential in the pressure switch is great enough, the
pressure switch closes and a 15-second pre-purge be-
gins. If the pressure switch is not proven within 2-1/2 min-
utes, the integrated control goes into Watchguard-Pres-
sure 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 seconds for a 4-second trial for ignition. The ignitor re-
mains energized for the rst 3 seconds during the 4 second
trial. If ignition is not proved during the 4-second period,
the integrated control will try four more times with an inter
purge and warm-up time between trials of 35 seconds.
After a total of ve trials for ignition (including the initial
trial), the integrated control goes into Watchguard-Flame
Failure mode. After a 60-minute reset period, the integrat-
ed control will begin the ignition sequence again.

Page 8
TABLE 1
4-Pin Terminal Designation
PIN # FUNCTION
1Combustion Air Inducer Line
2 Ignitor Line
3 Combustion Air Inducer Neutral
4 Ignitor Neutral
TABLE 2
12-Pin Terminal Designations
PIN # FUNCTION
1High Limit Output
2 Not Used
3 24V Line
4 Not Used
5 Rollout Switch Out
6 24V Neutral
7 High Limit Input
8Ground
9 Gas Valve Common
10 Pressure Switch In
11 Rollout Switch In
12 Gas Valve Out
TABLE 3
1/4” Quick Connect Terminals
120HUM Humidier 120VAC
LINE 120VAC
XFMR Transformer 120VAC
CIRC Indoor blower 120VAC
EAC Indoor air quality accessory 120VAC
NEUTRALS Common 120VAC
HUM24 Humidier 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 speed taps
FS Flame sense
24 COM Common 24VAC
INTEGRATED CONTROL
(Automatic Hot Surface Ignition System)
BLOWER OFF DELAY
RED LED RECALL BUTTON
FIGURE 3

Page 9
TABLE 4
RED LED
Flash Code2Diagnostic Codes / Status of Furnace
Off No power to control or board fault detected
Heartbeat
1
Normal Operation - Idle, Continuous Fan, Cool
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.
6Ignitor Circuit Failure - not available on this control
7Primary or Secondary Limit Open or Watchguard Mode - Limit Switch Open longer than 3 minutes
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 1A ”Heartbeat” is indicated by a ”Slow Flash” - 1 sec on 1 sec off, repeating
Note 2Error codes are indicated by a “rapid flash” - the LED flashes X times at ½ second on ½ second off, remains off for 3
seconds then repeats.
Note3
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.
(-02 inegrated Control)

Page 10
TABLE 5
(-03 Integrated Control)
RED LED
Flash Code 2
Diagnostic Codes / Status of Furnace
O󰀨 No power to control or board fault detected
Heartbeat1Normal Operation - Idle, Continuous Fan, Cool
Continuous Rapid Flash Call For Heat / Burner Operation
1Reverse Line Voltage Polarity
2 Improper Earth Ground
3 Burner failed to light, or lost ame during heat demand
4 Low Flame Signal - check ame sensor
5Watchguard - burner failed to light, exceeded maximum number of retries or
recycles.
6 Not Used
7Primary or Secondary Limit Open or Watchguard Mode - Limit Switch Open longer
than 3 minutes
8Rollout Switch Open
9 Pressure 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 o󰀨, repeating
Note - 2 Error codes are indicated by a “rapid ash” - the LED ashes X times at ½ second on ½
second o󰀨, remains o󰀨 for 3 seconds then repeats.
Note - 3
Last 10 error codes are stored in memory including when power is shut o󰀨 to the
unit. - To recall, pressand release button, most recent will be displayed rst, LED o󰀨 for 3
sec, then next error code is displayed, etc. To clear error codes, depress and hold button
longer than 5 seconds.

Page 11
DEMAND
CAI
GAS VALVE
15
ON
OFF
38
IGNITOR
34
1
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
Blower “On”*
Delay
ELECTRONIC IGNITION
FIGURE 4
Fan Time Control
Heating Fan On Time
The fan on time of 30 seconds is not adjustable.
Heating Fan O Time
Fan o󰀨 time (time that the blower operates after the heat
demand has been satised) can be adjusted by moving
the jumper to a di󰀨erent setting. The unit is shipped with
a factory fan o󰀨 setting of 90 seconds. For customized
comfort, monitor the supply air temperature once the heat
demand is satised. Note the supply air temperature at
the instant the blower is de-energized.
Adjust the fan-o󰀨 delay to achieve a supply air tempera-
ture between 90° - 110° at the instant the blower is de-en-
ergized. (Longer delay times allow for lower air tempera-
ture, shorter delay times allow for higher air temperature).
See gure 5.
Cooling Fan On Time
The fan on time is 2 seconds and is not adjustable.
Cooling Fan O Time
The control has a 45 second fan o󰀨 delay after cooling
demand has been met. This delay is factory set and not
adjustable.
HEAT FAN
‐
OFF TIME IN SECONDS
To adjust fan-off timing, reposition jumper across pins to
achieve desired setting.
NO JUMPER
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
FIGURE 5

Page 12
HEATING COMPONENTS Gaskets
Collector Box
Orifice Plate
Flue Transition
Pressure Switch
Combustion Air Inducer
Manifold And Gas Valve
Ignitor
Sensor
Rollout Switches
FIGURE 6
5. Flame Rollout Switches (Figure 6)
Flame rollout switch (S47) is a high temperature limit.
Each furnace is equipped with two identical switches. The
limit is a N.C. SPST manual-reset limit connected in series
with the integrated control A92. When S47 senses rollout,
the integrated control immediately stops ignition and clos-
es the gas valve. If unit is running and ame rollout is de-
tected, the gas valve will close and integrated control will
be disabled. Rollout can be caused by a blocked heat ex-
changer, blocked ue or lack of combustion air. The switch
has a factory setpoint of 210°F and cannot be adjusted.
To manually reset a tripped switch, push the reset button
located on the control.
6. Primary Limit Control
The primary limit on ML180UHE(X) units is located in the
heating vestibule panel under the combustion air induc-
er. See gure 7. When excess heat is sensed in the heat
exchanger, the limit will open. If the limit is open, the in-
tegrated control energizes the supply air blower and clos-
es the gas valve. The limit automatically resets when unit
temperature returns to normal.
The switch must reset within three minutes or SureLight®
control will go into Watchguard for one hour. The switch is
factory set and cannot be adjusted. The switch may have
a di󰀨erent setpoint for each unit model number. If limit
switch must be replaced, refer to Lennox ProductZone re-
pair parts list.
Primary Limit Under Combustion Air Inducer
Primary
Limit
FIGURE 7
7. Flame Sensor (Figure 6)
A ame sensor is located on the left side of the burner sup-
port. The sensor is mounted on the ame rollout plate and
the tip protrudes into the ame envelope of the left-most
burner. The sensor can be removed for service (clean
with steel wool) without removing any part of the burn-
ers. During operation, ame is sensed by current passed
through the ame and sensing electrode. The integrated
control allows the gas valve to remain open as long as
ame signal is sensed.
A microamp DC meter is needed to check the ame signal
on the integrated control.

Page 13
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 ame 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 gure 8 and table 6 for ame signal check.
1 - Set the meter to the DC amps scale.
2 - Turn o󰀨 supply voltage to control.
3 - Remove sensor wire from integrated control.
4 - Connect (-) lead to ame 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.
TABLE 6
Flame Signal in Microamps
Normal Low Drop Out
1.5 or greater 0.5 - 1.4 0.4 or less
Measuring Flame Signal
(Typical Furnace and Control)
Flame
Sensor
Flame Sensor
Wire
Integrated
Control
Remove Sensor Wire from
Integrated Control and
Connect Alligator Clip (−)
to Flame Sensor Lead
Flame Sensor
Terminal
Remove Sensor Wire from
Integrated Control and
Connect Alligator Clip (+)
to Terminal on Control
(+)
DIGITAL METER
(+) To Control
Sensor
Terminal
(-) To
flame
sensor
Set dial to measure dc microamps
(+)
Red Collar
Indicates
Positive
Lead
FIGURE 8

Page 14
8. Gas Valve (Figure 6)
The ML180UHE(X) uses an internally redundant gas
valve to assure safety shut-o󰀨. If the gas valve must be
replaced, the same type valve must be used. 24VAC ter-
minals and valve switch are located on the valve. All ter-
minals on the gas valve are connected to wires from the
integrated control. 24V applied to the terminals energizes
the valve.
Inlet and outlet pressure taps are located on the valve. A
regulator adjustment screw is located on the valve. LPG
changeover kits are available from Lennox. Kits include
burner orices and a gas valve regulator spring.
9. Combustion Air Inducer (B6)
All ML180UHE(X) units use a combustion air inducer to
move air through the burners and heat exchanger during
heating operation. The blower uses a 120VAC motor. The
motor operates during all heating operation and is con-
trolled by integrated control A92. The inducer also oper-
ates for 15 seconds before burner ignition (pre-purge) and
for 5 seconds after the gas valve closes (post-purge). A
pressure switch mounted on the combustion air inducer
orice plate is used to prove inducer operation. The com-
bustion air inducer orice will be di󰀨erent for each model.
See table 7 for orice sizes. The switch monitors air pres-
sure in the inducer housing. During normal operation, the
pressure in the housing is negative. If pressure becomes
less negative (signifying any obstruction in the ue) the
pressure switch opens. When the pressure switch opens,
the integrated control (A92) immediately de-energizes the
gas valve to prevent burner operation.
TABLE 7
Model C.A.I. Orice Size
045E36A 1.063”
070E36B 1.316”
090E48B, 090E60C 1.531”
110E60C 1.690”
135E60D 1.940”
10. Ignitor (Figure 6)
The nitride ignitor used on ML180UHE units is made from
a proprietary ceramic material. To check ignitor, measure
its resistance and voltage. A value of 39 to 70 ohms in-
dicates a good ignitor. Voltage to the ignitor should be
120VAC. See gure 9 for resistance, and voltage check.
NOTE - The ML180UHE(X) furnace contains electronic
components that are polarity sensitive. Make sure that the
furnace is wired correctly and is properly grounded.

Page 15
Test 2
Check ignitor for correct resistance.
Separate 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.
Meter
(set to ohms)
Meter
(set to ohms)
Integrated Control Board
Detail
Meter
(set to ohms)
Test 1
Check ignitor circuit for correct resistance.
Remove 4-pin plug from control.
Check ohms reading across terminals 2 and 4.
The 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.
IGNITOR CHECKS
FIGURE 9

Page 16
11. Combustion Air Inducer Pressure Switch (S18)
ML180UHE(X) series units are equipped with a combus-
tion air pressure switch located on the combustion air in-
ducer orice bracket. The switch is connected to the com-
bustion air inducer housing by means of a exible silicone
hose. It monitors negative air pressure in the combustion
air inducer housing.
The switch is 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 com-
bustion air inducer is not operating or if the ue becomes
obstructed.
On start-up, the switch senses that the combustion air
inducer is operating. It closes a circuit to the integrated
control when pressure inside the combustion air inducer
decreases to a certain set point. Set points vary depend-
ing on unit size. See table 8. The pressure sensed by
the switch is negative relative to atmospheric pressure.If
the ue becomes obstructed during operation, the switch
senses a loss of negative pressure (pressure becomes
more equal with atmospheric pressure) and opens the cir-
cuit to the integrated control and gas valve. A bleed port
on the switch allows relatively dry air in the vestibule to
purge switch tubing, to prevent condensate build up.
TABLE 8
Unit inches wc
Make Break + 0.05
045E36A-1, -2, -54 -0.75 -0.65
070E36B-1, -2 -0.83 -0.68
070E36B-54 -0.85 -0.70
090E48B, 090E60C-1, -2 -0.80 -0.65
090E48B-54 -0.85 -0.70
110E60C-1, -2 -0.83 -0.68
110E60C-54 -0.85 -0.70
135E60D-1, -2, -54 -0.80 -0.65
The switch is factory set and is not eld adjustable. It is a
safety shut-down control in the furnace and must not be
bypassed for any reason. If switch is closed or by-passed,
the integrated control will not initiate ignition at start up.
Troubleshooting
See gure 10 for measuring operating pressure and
checking resistance in the pressure switch.
MULTI−METER
SET TO MEASURE OHMS
+-
or
Field Provided
Tubing To CAI Port
To Pressure Switch
Remove tubing from CAI and
insert “Tee” and additional tubing.
High
Low
FIGURE 10

Page 17
Multiple Venting
The ML180UHE(X) furnace can vent in multiple positions.
See gure 11. The make up box may be removed and the
combustion air inducer may be rotated clockwise or coun-
terclockwise 90° to allow for vertical or horizontal vent dis-
charge in a vertical or horizontal cabinet position.
Remove the four mounting screws, rotate the assembly
(assembly consists of orice plate, proving switch, gasket
and combustion air inducer), then reinstall the mounting
screws. See unit Installation Instructions for more detail.
IMPORTANT
The combustion air pressure switch must be moved
for horizontal discharge air left position.
vent pipe
vent pipe
flue
transition
vent pipe
FLOW
AIR
flue transition
vent pipe
pressure switch
vent pipe
In all positions route the wires away from moving parts and the heat of the inducer
motor to prevent damage to the wires.The pressure switch must be installed above
the CAI to prevent moisture from collecting in the hoses or switch.
FLOW
AIR
Collector Box
Vent Pipe
Pressure
Switch
vent pipe
Collector Box
FLOW
AIR
Pressure
Switch
FIGURE 11

Page 18
12. Blower Motor
IMPORTANT
Each blower is statically and dynamically balanced
as an assembly before installation in the unit.
ML180UHE 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 motor is programmed to provide constant torque at
each of the ve selectable speed taps. Each tap requires
24 volts to energize.
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
Troubleshooting the motor is an easy process. Follow
steps below.
1 - Shut o󰀨 power to unit.
2 - Remove input plugs P48 and P49 from motor. See
gure 14 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
eld repairable.
If replacing the indoor blower motor or blower wheel is
necessary, placement is critical. The blower wheel must
be centered in the blower housing as shown in gure 12.
When replacing the indoor blower motor the set screw
must be aligned and tightened with the motor shaft as
shown in gure 13.
Center Blower Wheel
in Blower Housing
BLOWER WHEEL REPLACEMENT
FIGURE 12
Set Screw
Housing Hub
ALIGN AND TIGHTEN SET SCREW WITH
FLAT SIDE OF MOTOR SHAFT
Motor
Shaft
FIGURE 13

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
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 inpult 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)
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 necesssary)
Test 4 (if necessary)
FIGURE 14

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
module. See gure 15.
TWO HARNESS
CONNECTIONS
MOTOR CONTROL MODULE
MOTOR
Unplug the Two Harness Connection
FIGURE 15
4 - Remove the two hex head bolts securing the motor
control module to the motor (see gure 16).
REMOVE BOTH HEX
HEAD BOLTS
Remove the Hex Head Bolts
FIGURE 16
5 - Slide the motor control module away from the motor
to access and disconnect the internal three wire
connector. It is not necessary to remove blower
motor itself. Set both hex head bolts aside.
Testing the Motor (Figure17)
If any motor fails the below tests, do not install the new
control module. The motor is defective and it also must be
replaced. The new control can fail if placed on a defective
motor.
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
motor connector pins. These should all read
approximately the same resistance within an ohm.
3 - Check to see if the blower wheel spins freely.
Motor Test
FIGURE 17
TABLE 9
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 thou-
sand 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 specic 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
UNEXPECTED 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 gure 10. Torque bolts to
22 inch pounds or 1/16th clock wise turn.
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 (gure12). This
will directs moisture away from the motor and its
electric connections on the motor
CONNECTOR
ORIENTATION
BETWEEN 4 AND 8
O'CLOCK
BACK OF CONTROL
MODULE
DRIP LOOP
Drip Loop
FIGURE 18