Lennox ML180DF045P24A Installation and operation manual

Page 1 ©2013 Lennox Industries Inc.
ML180DF(X)
Service Literature
Corp. 1219-L4
Revised 02/2013
ML180DF series units are mid-efficiency gas furnaces
used for downflow applications only, manufactured with
Lennox Duraloktheat exchangers formed of aluminized
steel. ML180DF units are available in heating capacities of
44,000 to 110,000 Btuh and cooling applications 1.5 to 5
tons. Refer to Product Specifications bulletin for proper siz
ing.
Units are factory equipped for use with natural gas. Kits are
available for conversion to LP/Propane operation.
ML180DF model units are equipped with a hot surface igni
tion system. 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 recommended only and do not constitute
code.
TABLE OF CONTENTS
Specifications Page 2.............................
Blower Data Page 4..............................
Parts Identification Page 5.........................
I Unit Components Page 6........................
II Installation Page 14.............................
III Start Up Page 14..............................
IV Heating System Service Checks Page 14.........
V Typical Operating Characteristics Page 19.........
VI Maintenance Page 19..........................
VII Wiring and Sequence of Operation Page 22......
VIII Twinning Page 27.............................
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.
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 2
SPECIFICATIONS
Gas
Heating
Performance
Model No.
Model No. - Low NOx
ML180DF045P24A
- - -
ML180DF045P36A
- - -
ML180DF070P36A
ML180DF070XP36A
1AFUE 80% 80% 80%
Input - Btuh 44,000 44,000 66,000
Output - Btuh 35,000 36,000 53,000
Temperature rise range - °F 25 - 55 15 - 45 25 - 55
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. 10 x 7 10 x 8 10 x 8
Motor output - hp 1/5 1/3 1/3
Tons of add-on cooling 1.5 - 2 2 - 3 2 - 3
Air Volume Range - cfm 401 - 1157 739 - 1524 717 - 1562
Electrical
Data
Voltage 120 volts - 60 hertz - 1 phase
Blower motor full load amps 3.1 6.1 6.1
Maximum overcurrent protection 15 15 15
Shipping Data lbs. - 1 package 105 113 128
NOTE - Filters and provisions for mounting are not furnished and must be eld provided.
1 Annual Fuel Utilization Ef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.
Model No. - Low NOx
ML180DF090P36B
- - -
ML180DF090P48B
ML180DF090XP48B
ML180DF110P60C
ML180DF110XP60C
1AFUE 80% 80% 80%
Input - Btuh 88,000 88,000 110,000
Output - Btuh 71,000 71,000 89,000
Temperature rise range - °F 35 - 65 25 - 55 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. 10 x 9 10 x 10 11-1/2 x 10
Motor output - hp 1/3 1/2 1
Tons of add-on cooling 2 - 3 3 - 4 4 - 5
Air Volume Range - cfm 743 -1695 917 - 1929 1517 - 2760
Electrical
Data
Voltage 120 volts - 60 hertz - 1 phase
Blower motor full load amps 6.1 8.2 10.0
Maximum overcurrent protection 15 15 15
Shipping Data lbs. - 1 package 131 140 160
NOTE - Filters and provisions for mounting are not furnished and must be eld provided.
1 Annual Fuel Utilization Efciency based on DOE test procedures and according to FTC labeling regulations. Isolated combustion system rating for non-weatherized furnaces.

Page 3
HIGH ALTITUDE DERATE
NOTE - Units may be installed at altitudes up to 4500 ft. above sea level without any modications.
At altitudes above 4500 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 - 4500 Feet 4501 - 7500 Feet 7501 - 10,000 ft. Minimum
Maximum
Natural
Gas
LPG/
Propane
Natural
Gas
LPG/
Propane
1Natural
Gas
LPG/
Propane
Natural
Gas
LPG/
Propane
045 3.5 10 3.5 10 3.5 10 4.5 11 13
070 3.5 10 3.3 10 3.5 10 4.5 11 13
090 3.5 10 3.3 10 3.5 10 4.5 11 13
110 3.5 10 3.3 10 3.5 10 4.5 11 13
1 Natural Gas High Alitude Orice Kit required.
OPTIONAL ACCESSORIES - ORDER SEPARATELY
“A” Width
Models
“B” Width
Models
“C” Width
Models
CABINET ACCESSORIES
Downow Combustible Flooring Base 11M59 11M60 11M61
CONTROLS
Twinning Kit 15L38 15L38 15L38
FILTERS
1 Downow Filter Cabinet 51W06 51W07 51W08
No. and Size of lter - in. (1) 20 x 20 x 1 (2) 20 x 16 x 1 (2) 20 x 16 x 1
service kits
Night Service Kit 51W03 51W03 51W03
Universal Service Kit - Switches 89W19 89W19 89W19
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 No Change 80W51 70W89 76W15 73W81 73W37
070 No Change 80W52 80W51 70W89 76W15 73W81 73W37
090 No Change No Change 80W51 70W89 76W15 73W81 73W37
110 No Change 80W52 80W51 70W89 76W15 73W81 73W37
INSTALLATION CLEARANCES
Vent Type Type B1 Type C NOTE − Air for combustion must conform to the methods outlined in the
National Fuel Gas Code (NFPA 54/ANSI-Z223.1).
NOTE − In the U.S. ue sizing must conform to the methods outlined in the
current National Fuel Gas Code (NFPA 54/ANSI-Z223.1) or applicable
provisions of local building codes.
1 Left side requires 4 in. if single wall vent is used on 14-1/2 in. “A” width
cabinets, 2 in. on 17-1/2 in. “B” width cabinets.
2 Clearance for installation on combustible oor if Optional Downow
Combustible Flooring Base is installed between furnace and combustible oor.
Not required in add-on cooling applications if installed in accordance with local
codes, National Fuel Gas Code ANSI-Z223.1 or National Standard of Canada
CAN/CSA-B149.1 and CAN/CSA-B149.2 Installation Code for Gas Burning
Appliances”. Do not install the furnace directly on carpeting, tile, or other
combustible materials other than wood ooring.
Sides 0 in. (0 mm) 1in. (0 mm)
Rear 0 in. (0 mm) 0 in. (0 mm)
Top 1 in. (25 mm) 1 in. (25 mm)
Front 2-1/4 in. (57 mm) 2-1/4 in. (57 mm)
Front (service/alcove) 24 in. (610 mm) 24 in. (610 mm)
Floor 2 Combustible 2 Combustible
Flue 1 in. (25 mm) 6 in. (152 mm)

Page 4
BLOWER DATA
ML180DF045P36A PERFORMANCE (Less Filter)
External
Static
Pressure
in. w.g.
Air Volume / Watts at Various Blower Speeds
High Medium-
High
Medium-
Low Low
cfm Watts cfm Watts cfm Watts cfm Watts
0.10 1524 567 1385 528 1144 431 947 366
0.20 1465 542 1351 490 1129 407 943 354
0.30 1414 517 1293 463 1111 393 950 341
0.40 1343 489 1236 436 1083 371 945 329
0.50 1255 464 1190 409 1038 356 897 311
0.60 1205 443 1106 380 999 333 870 292
0.70 1140 421 1059 366 943 317 816 275
0.80 1031 388 962 335 870 297 739 252
ML180DF070P36A PERFORMANCE (Less Filter)
External
Static
Pressure
in. w.g.
Air Volume / Watts at Various Blower Speeds
High Medium-
High
Medium-
Low Low
cfm Watts cfm Watts cfm Watts cfm Watts
0.10 1562 591 1386 539 1159 436 956 374
0.20 1506 553 1355 504 1149 418 953 361
0.30 1459 528 1314 473 1119 392 941 343
0.40 1390 500 1264 442 1082 374 915 323
0.50 1306 477 1200 415 1048 352 904 305
0.60 1213 441 1129 391 987 332 849 288
0.70 1140 417 1066 361 901 304 798 270
0.80 1038 395 975 342 836 283 717 244
ML180DF090P48B PERFORMANCE (Less Filter)
External
Static
Pressure
in. w.g.
Air Volume / Watts at Various Blower Speeds
High Medium-
High
Medium-
Low Low
cfm Watts cfm Watts cfm Watts cfm Watts
0.10 1929 755 1794 668 1585 572 1332 489
0.20 1864 717 1745 623 1544 540 1321 463
0.30 1779 683 1676 588 1496 510 1296 440
0.40 1694 647 1600 558 1443 473 1265 417
0.50 1596 607 1502 511 1363 440 1212 393
0.60 1483 577 1413 485 1258 406 1148 370
0.70 1340 544 1273 449 1148 374 1042 339
0.80 1221 505 1138 416 1018 350 917 307
ML180DF110P60C PERFORMANCE (Less Filter)
External
Static
Pressure
in. w.g.
Air Volume / Watts at Various Blower Speeds
High Medium-
High
Medium-
Low Low
cfm Watts cfm Watts cfm Watts cfm Watts
0.10 2760 1401 2325 1045 1888 871 1531 686
0.20 2670 1362 2319 1003 1937 847 1565 679
0.30 2557 1292 2257 964 1945 832 1605 674
0.40 2536 1287 2220 949 1935 812 1622 661
0.50 2384 1230 2152 911 1918 782 1626 644
0.60 2273 1191 2063 884 1884 762 1617 630
0.70 2197 1151 2021 875 1822 737 1574 610
0.80 2115 1140 1950 854 1749 708 1517 579
ML180DF045P24A PERFORMANCE (Less Filter)
External
Static
Pressure
in. w.g.
Air Volume / Watts at Various Blower Speeds
High Medium-
High
Medium-
Low Low
cfm Watts cfm Watts cfm Watts cfm Watts
0.10 1157 399 938 333 764 273 699 243
0.20 1120 381 924 322 745 264 677 237
0.30 1084 362 890 311 723 258 650 230
0.40 1027 349 864 298 695 250 633 224
0.50 975 334 814 283 674 238 605 215
0.60 902 322 764 268 623 225 564 203
0.70 831 305 682 248 549 208 477 186
0.80 713 280 576 228 470 192 401 171
ML180DF090P36B PERFORMANCE (Less Filter)
External
Static
Pressure
in. w.g.
Air Volume / Watts at Various Blower Speeds
High Medium-
High
Medium-
Low Low
cfm Watts cfm Watts cfm Watts cfm Watts
0.10 1695 647 1431 546 1180 468 973 379
0.20 1641 611 1405 516 1162 443 967 368
0.30 1595 589 1384 492 1146 420 958 349
0.40 1525 548 1344 472 1136 399 954 337
0.50 1438 515 1271 432 1110 374 929 319
0.60 1370 489 1197 400 1057 352 886 299
0.70 1260 451 1119 374 983 328 823 273
0.80 1164 425 1020 344 900 300 743 249

Page 5
ML180DF PARTS ARRANGEMENT
FIGURE 1
Primary Limit
(under combustion
air inducer)
Control Box
(includes integrated control,
interlock switch and transformer)
Gas Valve Burner Box
(includes sensor, ignitor
and rollout switches)
Combustion
Air Inducer
Blower Access Panel
Heating Compartment
Access Panel
Heat Exchanger
Flue Chase
Blower Assembly
Secondary Limit

Page 6
I-UNIT COMPONENTS
ML180DF unit components are shown in figure 1.The gas
valve, combustion air inducer and burners can be ac
cessed by removing the heating compartment access pan
el. Electrical components are in the control box (figure 2)
found in the blower section.
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.
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.
FIGURE 2
CONTROL BOX ML180DF
Integrated Control
Transformer
Door
Interlock
Switch
3. Integrated 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 and 2), flame sensor and ignitor (figure 6).
The integrated control and ignitor work in combination to
ensure furnace ignition and ignitor durability. The inte
grated control, controls all major furnace operations. The
integrated control also features a RED LED for trouble
shooting and two accessory terminals rated at (1) one
amp. See table 3 for troubleshooting diagnostic codes.
The 120 volt ignitor is made from a high strength, silicon
nitride 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 be
gin 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 after which the gas valve opens for a 4-sec
ond trial for ignition. The ignitor remains energized for the
first 3 seconds of trial for ignition. If ignition is not proved
during the trial for ignition, the integrated control will try four
more times with an inter purge and warm-up time between
trials of 30 seconds. After a total of five trials for ignition (in
cluding the initial trial), the integrated control goes into
Watchguard-Flame Failure mode. After a 60-minute reset
period, the integrated control will begin the ignition se
quence again.

Page 7
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
2 Sensor
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
FIGURE 3
INTEGRATED CONTROL
(Automatic Hot Surface Ignition System)
TERMINAL DESIGNATIONS
HUM
LINE
XFMR
EAC
COOL
HEAT
PARK
CONT
NEUTRALS
Humidifier (120VAC)
Input (120VAC)
Transformer (120VAC)
Indoor Air Qality Accessory Air Cleaner (120VAC)
Blower - Cooling Speed (120VAC)
Blower - Heating Speed (120VAC)
Dead terminals to park alternate spd taps
Continuous blower
Neutral terminals (120VAC)
PUSH BUTTON
LED
TWIN
TWIN Twinning Terminal (24VAC)
ÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉ
ÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉ
ÉÉÉÉÉÉÉÉÉÉÉÉÉ
ÉÉÉÉÉÉÉÉÉÉÉÉÉ
ÉÉ
DEMAND
CAI
GAS VALVE
15
ON
OFF
ÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉ
ÉÉ
ÉÉ
39
ÉÉÉÉÉÉÉÉÉÉ
ÉÉÉÉÉÉÉÉÉÉ
IGNITOR
35
1
Pre -Purge Ignitor Warm-up Trial for
Ignition Post
Purge
5 SEC69
*Blower on time will be 30 seconds after flame is sensed. Blower off time will depend on “OFF TIME” Setting.
INDOOR BLOWER
ÉÉÉÉÉÉÉÉÉ
Blower “On”*
Delay
ELECTRONIC IGNITION
FIGURE 4

Page 8
TABLE 3
Note - This control is equipped with a push button switch for
diagnostic code recall. The control stores the last 5 fault
codes in non-volatile memory. The most recent fault code is
flashed first, the oldest fault code is flashed last. There is a
2 second pause between codes. When the push button
switch is pressed for less than 5 seconds, the control will
flash the stored fault codes when the switch is released.
The fault code history may be cleared by pressing the push
button switch for more than 5 seconds.
Integrated Control Diagnostic Codes
DIAGNOSTIC CODES
LED Status DESCRIPTION
LED Off No power to control or control harware
fault detected.
LED On Normal operation.
1 Flash Flame present with gas vavle
de-energized.
2 Flashes Pressure switch closed with combustion
air inducer de-energized.
3 Flashes Pressure switch open with combus
tion air inducer energized.
4 Flashes Primary limit switch open.
5 Flashes Rollout switch open.
6 Flashes Pressure switch cycle lockout.
7 Flashes Lockout, burners fail to light.
8 Flashes Lockout, buners lost flame too many
times.
9 Flashes Line voltage polarity incorrect.
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 120 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 5.
Cooling Fan On Time
The fan on time is 2 seconds and is not adjustable.
Cooling Fan Off Time
The control has a 60 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 5
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 9
ML180DF HEATING COMPONENTS
FIGURE 6
Internal flue pipe
Gasket
Orifice plate
Pressure switch
Collector box
Combustion air inducer
Ignitor
Sensor
Rollout
switch
Burners
Burner box
assembly
Manifold and
Gas valve
4. Flame Rollout Switch (Figure 6)
Flame rollout switch (S47) is a high temperature limit. 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
closes the gas valve. If unit is running and flame rollout is
detected, the gas valve will close and integrated control will
be disabled. Rollout can be caused by a blocked heat ex
changer, blocked flue 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.
5. Primary Limit Control
The primary limit on ML180DF units is located in the heating
vestibule panel under the combustion air inducer. When ex
cess heat is sensed in the heat exchanger, the limit will open. If
the limit is open, the integrated control energizes the supply air
blower and closes the gas valve. The limit automatically resets
when unit temperature returns to normal. The switch must re
set within three minutes or the control will go into Watchguard
for one hour. The switch is factory set and cannot be ad
justed. The switch may have a different setpoint for each unit
model number. If limit switch must be replaced, refer to Len
nox ProductZone repair parts list on Lennox DaveNet®.
6. Flame Sensor (Figure 6)
A flame sensor is located on the left side of the burner sup
port. The sensor is mounted on the flame rollout plate and
the tip protrudes into the flame envelope of the left-most
burner. The sensor can be removed for service (clean us
ing steel wool) without removing any part of the burners.
During operation, flame is sensed by current passed
through the flame and sensing electrode. The integrated
control allows the gas valve to remain open as long as
flame signal is sensed.
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.

Page 10
To Measure Flame Signal - Integrated Control:
Use a digital readout meter capable of reading DC micro
amps. See figure 7 and table 4 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.
TABLE 4
Flame Signal in Microamps
Normal Low Drop Out
1.5 0.5 - 1.4 0.4
FIGURE 7
Measuring Flame Signal
(upflow furnace shown)
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