Lennox ML193DF045P36B Unit Information

Corp. 1026-L5
Revised 03-2014
Service Literature
ML193DF
ML193DF SERIES UNITS
ML193DF series units are high-efficiency gas furnaces
manufactured with Lennox DuralokPlust aluminized steel
clamshell-type heat exchangers, with a stainless steel con­
densing coil. ML193DF units are available in heating input
capacities of 44,000 to 110,000 Btuh (13 to 32.2 kW) and
cooling applications from 2 through 5 tons (7.0 through
17.6 kW). Refer to Engineering Handbook for proper siz­
ing.
Units are factory equipped for use with natural gas. A kit is
available for conversion to LPG operation. All ML193DF
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 out­
lined 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.
WARNING
Table of Contents
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.
Specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
Optional Accessories . . . . . . . . . . . . . . . . . . . . . . . . . . 3
Blower Performance Data . . . . . . . . . . . . . . . . . . . . . . 4
I-Unit Components . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
II Placement and Installation . . . . . . . . . . . . . . . . . . . . 18
III-Start-Up . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36
WARNING
IV-Heating System Service Checks . . . . . . . . . . . . . . 37
V-Typical Operating Conditions . . . . . . . . . . . . . . . . . 39
Sharp edges.
Be careful when servicing unit to avoid sharp edges
which may result in personal injury.
VI-Maintenance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40
VII-Wiring and Sequence of Operation . . . . . . . . . . . 42
Page 1
© 2014 Lennox Industries Inc.
Litho U.S.A.
SPECIFICATIONS
Gas
Heating
Performance
Model No. ML193DF045P36B ML193DF070P36B ML193DF090P48C ML193DF110P60C
93%
93%
93%
93%
Input - Btuh
44,000
66,000
88,000
110,000
Output - Btuh
41,000
61,000
82,000
102,000
Temperature rise range - °F
25 - 55
50 - 80
40 - 70
50 - 80
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
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.
1/2
1/2
1/2
1/2
with field supplied (PVC coupling) - o.d.
3/4
3/4
3/4
3/4
10 x 8
10 x 8
10 x 10
11 ½ x 10
1/3
1/3
1/2
1
Tons of add-on cooling
2.5 - 3
2.5 - 3
3-4
4-5
Air Volume Range - cfm
605 - 1615
560 - 1550
920 - 2145
1210 - 2410
1
AFUE
Gas Manifold Pressure (in. w.g.)
Nat. Gas / LPG/Propane
Connections
in.
Indoor
Blower
Wheel nom. dia. x width - in.
Motor output - hp
Electrical
Data
Voltage
120 volts - 60 hertz - 1 phase
Blower motor full load amps
6.1
6.1
8.2
11.5
Maximum overcurrent protection
15
15
15
15
124
129
147
162
Shipping Data
lbs. - 1 package
NOTE - Filters and provisions for mounting are not furnished and must be field provided.
1
Annual Fuel Utilization Efficiency based on DOE test procedures and according to FTC labeling regulations. Isolated combustion system rating for non-weatherized
furnaces.
Page 2
OPTIONAL ACCESSORIES - MUST BE ORDERED EXTRA
“B” Width Models
“C” Width Models
11M60
11M61
6 ft.
26K68
26K68
24 ft.
26K69
26K69
50 ft.
26K70
26K70
Fiberglass - 1/2 in. x 66 ft.
36G53
36G53
Aluminum foil - 2 in. x 60 ft.
16P89
16P89
51W18
51W18
65W80
65W80
51W07
51W08
(2) 20 x 20 x 1
(2) 20 x 20 x 1
51W03
51W03
71M80
69M29
---
60L46
44W92
44W92
---
44W93
CABINET ACCESSORIES
Downflow Combustible Flooring Base
CONDENSATE DRAIN KITS
Condensate Drain Heat Cable
Heat Cable Tape
Crawl Space Vent Drain Kit
CONTROLS
Twinning Kit
DOWNFLOW FILTER KITS
Downflow Air Filter and Rack Kit
No. and Size of filter - in.
NIGHT SERVICE KITS
Night Service Kit
TERMINATION KITS
See Installation Instructions for specific venting information.
Termination Kits Direct Vent Applications
Only
Concentric
US - 2 in.
3 in.
Canada - 2 in.
3 in.
Termination Kits Direct or Non-Direct vent
Flush-Mount
2, 2-1/2 or 3 in.
51W11
51W11
Wall - Close
Couple
US - 2 in.
22G44
---
3 in.
44J40
44J40
Wall - Close
Couple WTK
Canada - 2 in.
30G28
---
3 in.
81J20
81J20
Roof
2 in.
15F75
Wall Ring Kit
2 in.
15F74
Roof Termination Flashing Kit - Direct or Non-Direct Vent Contains two flashings
15F75
3
44J41
15F74
44J41
Cleanable polyurethane frame type filter.
Kits contain enough parts for two, non−direct vent installations.
3
Non-direct vent only.
NOTE - Termination Kits 44W92, 44W93, 30G28, 81J20 are certified to ULC S636 standard for use in Canada only.
1
2
GAS HEAT ACCESSORIES
Input
all models
High Altitude
Pressure Switch Kit
Natural Gas to
LPG/Propane Kit
LPG/Propane
to Natural Gas Kit
Natural Gas
High Altitude
Orifice Kit
4501 - 7500 ft.
7501 - 10,000 ft.
0 - 7500 ft.
0 - 7500 ft.
7501- 10,000 ft.
74W90
74W91
69W73
73W81
73W37
Page 3
BLOWER DATA
ML193DF045XP36B PERFORMANCE (Less Filter)
External
Static
Pressure
in. w.g.
ML193DF090XP48C PERFORMANCE (Less Filter)
Air Volume / Watts at Various Blower Speeds
High
MediumHigh
MediumLow
Low
cfm Watts cfm Watts cfm Watts cfm Watts
External
Static
Pressure
in. w.g.
Air Volume / Watts at Various Blower Speeds
High
MediumHigh
MediumLow
Low
cfm Watts cfm Watts cfm Watts cfm Watts
0.00
1615 650 1385 555 1205 465 1045 390
0.00
2075 800 1890 720 1625 645 1375 535
0.10
1605 640 1375 545 1195 455 1035 380
0.10
1995 755 1830 680 1590 615 1350 515
0.20
1500 620 1340 525 1165 445 1015 370
0.20
1910 715 1775 645 1575 580 1340 500
0.30
1450 590 1290 490 1125 420
975
365
0.30
1825 680 1705 610 1530 550 1325 485
0.40
1350 560 1235 480 1090 405
920
345
0.40
1730 645 1620 580 1475 525 1285 460
0.50
1300 545 1170 450 1035 380
875
335
0.50
1630 615 1530 545 1405 500 1240 440
0.60
1195 500 1095 425
840
320
0.60
1530 585 1450 525 1330 470 1175 420
990
365
0.70
1140 485 1020 400
895
345
780
300
0.70
1430 555 1340 485 1260 450 1095 390
0.80
1025 450
920
370
840
330
695
275
0.80
1300 525 1245 465 1145 415 1015 370
0.90
945
800
335
700
295
605
250
0.90
1185 495
435
ML193DF070XP36B PERFORMANCE (Less Filter)
External
Static
Pressure
in. w.g.
MediumHigh
MediumLow
430 1045 385
915
340
ML193DF110XP60C PERFORMANCE (Less Filter)
Air Volume / Watts at Various Blower Speeds
High
1110
Low
cfm Watts cfm Watts cfm Watts cfm Watts
External
Static
Pressure
in. w.g.
High
MediumHigh
MediumLow
Low
cfm Watts cfm Watts cfm Watts cfm Watts
0.00
1505 660 1310 570 1090 455
940
390
0.10
1480 625 1295 550 1070 435
935
365
0.10
2405 1385 2180 1070 1855 905 1555 730
0.20
1405 585 1255 515 1055 425
930
350
0.20
2285 1345 2120 1030 1850 865 1540 720
0.30
1355 580 1225 475 1045 405
900
330
0.30
2220 1315 2015 1005 1770 840 1535 705
0.40
1305 540 1165 470 1010 385
890
325
0.40
2185 1295 1950 955 1750 815 1530 685
0.50
1270 525
835
305
0.50
2045 1240 1830 925 1680 790 1500 660
1110
425
975
370
0.00
Air Volume / Watts at Various Blower Speeds
2410 1390 2190 1080 1860 910 1560 735
0.60
1175 500 1080 415
925
345
815
290
0.60
1965 1220 1710 890 1575 755 1445 640
0.70
1105 460 1000 395
855
320
745
270
0.70
1820 1165 1610 850 1495 720 1370 615
0.80
1040 440
925
365
790
300
670
250
0.80
1625 1155 1510 820 1400 695 1315 595
0.90
920
825
335
680
270
560
225
0.90
1455 1110 1390 790 1350 660 1210 565
400
Page 4
PARTS ARRANGEMENT
CONTROL BOX
(Includes integrated control,
transformer and door switch)
BAG ASSEMBLY
BLOWER MOTOR
(hidden)
BLOWER
ACCESS
PANEL
COMBUSTION
AIR INDUCER
BLOWER DECK
PRIMARY LIMIT
BURNER
ACCESS
PANEL
COLD END HEADER BOX
HEAT EXCHANGER
GAS VALVE
BURNER BOX ASSEMBLY
(includes sensor, rollout switches and ignitor)
FIGURE 1
Page 5
I-UNIT COMPONENTS
WARNING
ML193DF unit components are shown in figure 1. The
combustion air inducer, gas valve and burners can be ac­
cessed by removing the burner access panel. The blower
and control box can be accessed by removing the blower
access door.
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
result if repair is attempted.
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.
ML193DF Control Box
INTEGRATED IGNITION
CONTROL
(A92)
DOOR INTERLOCK
SWITCH (S51)
The ignition control system consists of an integrated con­
trol (figure 4) ignitor (figure 10) and sensor (figure 10). The
integrated control and ignitor work in combination to en­
sure furnace ignition and ignitor durability. The integrated
control, controls all maor furnace operations. The inte­
grated control also features two LED lights (DS1 red and
DS2 green) for troubleshooting and two accessory termi­
nals rated at (1) one amp. The integrated control also fea­
tures a (3) amp fuse for overcurrent protection. Tables 1
and 2 show jack plug terminal designations. See table 3 for
troubleshooting diagnostic codes. The 95 volt ignitor is
made from a high strength, silicon nitride material that pro­
vides long life and trouble free maintenance. The inte­
grated control continuously monitors line voltage and
maintains the ignitor power at a consistent level to provide
proper lighting and maximum ignitor life.
TABLE 1
4-Pin Terminal Designation
TRANSFORMER
(T1)
PIN #
FIGURE 2
FUNCTION
1
Combustion Air Inducer Line
2
3
4
Ignitor Line
Combustion Air Inducer Neutral
Ignitor Neutral
TABLE 2
1. Transformer (T1)
PIN #
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. Integrated Ignition Control 100973 (A92)
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.
12-Pin Terminal Designations
FUNCTION
1
High Limit Output
2
Not Used
3
24V Line
4
Not Used
5
Rollout Switch Out
6
24V Neutral
7
High Limit Input
8
Ground
9
Gas Valve Common
10
Pressure Switch In
11
Rollout Switch In
12
Gas Valve Out
Electronic Ignition (See Figure 5)
On a call for heat the integrated control monitors the com­
bustion air inducer prove switch. The integrated control will
not begin the heating cycle if the prove switch is closed (bypassed). Once the prove switch is determined to be open,
the combustion air inducer is energized. When the differen­
Page 6
tial in the prove switch is great enough, the prove switch
closes and a 15-second pre-purge begins. If the prove
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 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 five trials
for ignition (including 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 sequence again.
The integrated control has an added feature of ignitor pow­
er regulation to maintain consistent lighting and longer igni­
tor life under all line voltage conditions.
Fan Control
The fan on time of 30 seconds is not adjustable. The fan off
delay (amount of time that the blower operates after the
heat demand has been satisfied) may be adjusted by
changing the jumper position across the five pins on the
integrated control. The unit is shipped with a factory fan off
setting of 90 seconds. The fan off delay affects comfort and
is adjustable to satisfy individual applications. Adjust the
fan off delay to achieve a supply air temperature between
90° and 110°F at the moment that the blower is de-ener­
gized. Longer off delay settings provide lower return air
temperatures; shorter settings provide higher return air
temperatures. See figure 3.
FAN‐OFF TIME IN SECONDS
NO JUMPER
To adjust fan-off timing, reposition jumper across pins
to achieve desired setting.
FIGURE 3
INTEGRATED CONTROL
(Automatic Hot Surface Ignition System)
HUM
LINE
XFMR
EAC
COOL
HEAT
PARK
FLAME
NEUTRALS
TERMINAL DESIGNATIONS
Humidifier (120VAC)
Input (120VAC)
Transformer (120VAC)
Electronic Air Cleaner (120VAC)
Blower - Cooling Speed (120VAC)
Blower - Heating Speed (120VAC)
Dead terminals to park alternate spd taps
Flame sensor
Neutral terminals (120VAC)
3 AMP, 32 VAC FUSE
LED 1
LED 2
BLOWER OFF
DELAY JUMPER
FIGURE 4
Page 7
The integrated control is equipped with two LED lights for troubleshooting. The diagnostic codes are listed below in table 3.
TABLE 3
DIAGNOSTIC CODES
Make sure to Identify LED'S Correctly.
LED #1 (Red)
LED #2 (Green)
DESCRIPTION
SIMULTANEOUS
SLOW FLASH
SIMULTANEOUS
SLOW FLASH
Power on - Normal operation.
Also signaled during cooling and continuous fan.
SIMULTANEOUS
FAST FLASH
SIMULTANEOUS
FAST FLASH
Normal operation - signaled when heating demand initiated at thermostat.
SLOW FLASH
ON
OFF
SLOW FLASH
Pressure prove switch open.
OR: Blocked inlet/exhaust vent;
OR: Pressure switch closed prior to activation of combustion air inducer.
ALTERNATING
SLOW FLASH
ALTERNATING
SLOW FLASH
Watchguard 1 hour -- burners failed to ignite or lost flame 5 times during single
heating demand.
SLOW FLASH
OFF
ON
SLOW FLASH
ON
ON
Primary or secondary limit switch open. Limit must close within 3 minutes or unit
goes into 1 hour Watchguard.
Flame sensed without gas valve energized.
Rollout switch open. OR: 12‐pin connector improperly attached.
Circuit control failure or control wired incorrectly.
ON
OFF
OFF
ON
FAST FLASH
SLOW FLASH
Main power polarity reversed. Switch line and neutral.
SLOW FLASH
FAST FLASH
Low flame signal. Measures below 1.5 microamps. Replace flame sense rod.
ALTERNATING
FAST FLASH
ALTERNATING
FAST FLASH
Improper main ground.
OR: Line voltage below 90 volts.
NOTE - Slow flash rate equals 1 Hz (one flash per second). Fast flash rate equals 3 Hz (three flashes per second).
Minimum flame sense current = 0.5 microAmps.
É
É
É
ON
OFF
15 Sec.
Pre -Purge
20 sec.
Ignitor Warmup
*4 Sec.Trial
for Ign.
**Blower “On”
Delay
End of
Heat Demand
5 SEC
Blower
Off
Time
ÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉ
ÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉ
ÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉ
ÉÉÉÉÉÉÉÉÉ
ÉÉÉÉÉÉÉÉÉ
ÉÉÉÉÉÉÉÉÉÉÉÉÉ
ÉÉÉÉÉÉÉÉÉ
ÉÉÉÉÉÉÉÉÉ
Post
Purge
DEMAND
CAI
IGNITOR
GAS VALVE
INDOOR BLOWER
*Ignitor will energize the first 3 seconds of the 4 second trial for ignition
**Blower on time will be 45 seconds after gas valve is energized. Blower off time will depend on “OFF TIME” Setting.
FIGURE 5
Page 8
TABLE 5
4. Integrated Ignition Control 103085 (A92)
PIN #
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 6 with control terminal designations
in tables 4 and 5), flame sensor and ignitor (figure 10). 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 troubleshooting
and two accessory terminals rated at (1) one amp. See
table 6 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.
4-Pin Terminal Designation
PIN #
FUNCTION
1
Combustion Air Inducer Line
2
3
4
Ignitor Line
Combustion Air Inducer Neutral
Ignitor Neutral
1
High Limit Output
2
Sensor
3
24V Line
4
Not Used
5
Rollout Switch Out
6
24V Neutral
7
High Limit Input
8
Ground
9
Gas Valve Common
10
Pressure Switch In
11
Rollout Switch In
12
Gas Valve Out
TABLE 6
Electronic Ignition (Figure 7)
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 (bypassed). 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 the 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.
TABLE 4
12-Pin Terminal Designations
FUNCTION
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.
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.
Page 9
INTEGRATED CONTROL
(Automatic Hot Surface Ignition System)
HUM
LINE
XFMR
EAC
COOL
HEAT
PARK
CONT
NEUTRALS
TWIN
TERMINAL DESIGNATIONS
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)
Twinning Terminal (24VAC)
LED
PUSH BUTTON
TWIN
FIGURE 6
ÉÉ
ÉÉ
ON
OFF
DEMAND
CAI
IGNITOR
GAS VALVE
INDOOR BLOWER
ELECTRONIC IGNITION
1
35
15
69
39
5 SEC
ÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉ
ÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉ
ÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉ
ÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉ
ÉÉÉÉÉÉÉÉÉÉ
ÉÉÉÉÉÉÉÉÉÉÉÉÉ
ÉÉÉÉÉÉÉÉÉÉÉÉÉ
ÉÉÉÉÉÉÉÉÉ
ÉÉÉÉÉÉÉÉÉ
Pre -Purge
Ignitor Warm-up
Trial for
Ignition
Blower “On”*
Delay
Post
Purge
*Blower on time will be 30 seconds after flame is sensed. Blower off time will depend on “OFF TIME” Setting.
FIGURE 7
Page 10
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 8.
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.
Twinning 2 ML193DF Furnaces
Integrated control 103085 is equipped with a provision to
”twin” (interconnect) two(2) adjacent furnaces with a com­
mon plenum such that they operate as one (1) large unit.
When twinned, the circulating blower speeds are synchro­
nized between the furnaces. If either furnace has a need to
run the blower, both furnaces will run the blower on the
same speed. The cooling speed has highest priority, fol­
lowed by heating speed and fan speed.
Field installation of twinning consists of connecting wires
between the ”C” and ”Twin” terminals of the two controls.
The 24 VAC secondary of the two systems must be in
phase. All thermostat connections are made to one control
only. Figure 9 show wiring for two-stage and single stage
thermostats.
The twinned furnace without thermostat connections is to
have the call for heat supplied by an external 24VAC isola­
tion relay to prevent its rollout switch from being bypassed
by the other twinned furnace. The coil of the isolation relay
connects from the thermostat ”W” to 24 VAC common. The
contacts of the relay connect ”R” to ”W” on the non-thermo­
stat twin.
HEAT FAN‐OFF TIME IN SECONDS
NO JUMPER
To adjust fan-off timing, reposition jumper across pins to
achieve desired setting.
180 Second
off Time
60
90
120
180
120 Second
off Time
60
90
120
180
90 Second
off Time
60
90
120
180
60
90
120
180
60 Second
off Time
FIGURE 8
Page 11
FIELD WIRING FOR TWINNING THE ML193DF
TWO-STAGE THERMOSTAT
TWIN
R
SINGLE STAGE THERMOSTAT
R
R
TWIN 1
Y
TWIN 1
Y
Y
Y
Call For Fan
Call For Fan
G
Call For 2nd
StageHeat
R
Call For Cool
Call For Cool
Call For 1st
Stage Heat
TWIN
G
G
G
Call For Heat
W
W1
W2
W
W
C
C
TWIN
TWIN
ISOLATION
RELAY
ISOLATION
RELAY
R
R
TWIN 2
TWIN 2
Y
Y
G
G
W
W
C
C
FIGURE 9
Page 12
NOTE - The ML193DF furnace contains electronic
components that are polarity sensitive. Make sure that
the furnace is wired correctly and is properly grounded.
B-Heating Components
Combustion air inducer (B6), primary limit control (S10),
SureLight ignitor, burners, flame rollout switch (S47), gas
valve (GV1), combustion air prove switch (S18), and clam­
shell heat exchangers are located in the heating compart­
ment. The heating compartment can be accessed by re­
moving the burner access panel.
1. Ignitor (Figure 10)
ML193DF units use a mini-nitride ignitor made from a pro­
prietary ceramic material. Ignitor longevity is enhanced by
controlling the voltage to the ignitor. Units equipped with
control 103085 have a 120V ignitor. Units equipped with
control 100973 have a 95V ignitor. See figure 11 and table
7 for resistance and voltage checks.
2. Flame Sensor (Figure 10)
3. Flame Rollout Switches (Figure 10)
Flame rollout switches S47 are SPST N.C. high tempera­
ture limits located on the top left and bottom right of the front
buner box plate. S47 is wired to the burner ignition control
A92. When either of the switches sense flame rollout (indi­
cating a blockage in the combustion passages), the flame
rollout switch trips, and the ignition control immediately
closes the gas valve. Switch S47 in all ML193DF units is
factory preset to open at 250_F + 12_F (121_C + 6.7_C) on
a temperature rise. All flame rollout switches are manual
reset.
A flame sensor is located on the left side of the burner sup­
port. The sensor is mounted on the bottom burner box plate
and the tip protrudes into the flame envelope of the leftmost burner. The sensor can be removed for service with­
out removing any part of the burners. During operation,
flame is sensed by current passed through the flame and
sensing electrode. The ignition control allows the gas valve
to remain open as long as flame signal is sensed.
ML193DF Burner Box Assembly
IGNITOR
BURNERS
ROLLOUT SWITCHES
FRONT BURNER BOX PLATE
SENSOR
GAS VALVE
FIGURE 10
Page 13
IGNITOR CHECKS
Control
103085
100973
TABLE 7
Ohms
Voltage + 10%
39 to 70
120
24 to 47
95
Test 1
Multi−Meter
(set to ohms)
Integrated Control Detail
Test 1
Check ignitor circuit for correct resistance.
Remove 4-pin plug from control.
Check ohms reading across terminals 2 and 4.
See table 7. 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. See table 7. 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.
Multi−Meter
(set to ohms)
Test 2
Integrated Control Detail
Multi−Meter
(set to VAC)
Test 3
Integrated Control Detail
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. See
table 7. If voltage reads below these values, check for
correct supply voltage to furnace.
FIGURE 11
Page 14
4. Primary Limit Control (Figure 12)
Primary limit (S10) used on ML193DF 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 deenergizes the gas valve. The limit automatically resets
when unit temperature returns to normal. The switch is fac­
tory set and cannot be adjusted. For limit replacement re­
move wires from limit terminals and rotate limit switch 90
degrees. Slowly remove from the vestibule panel. Install
replacement limit with same care.
burner input. See table 8 for orifice size. The burner is sup­
ported by the orifice and will easily slide off for service. A
flame retention ring in the end of each burner maintains
correct flame length and shape and keeps the flame from
lifting off the burner head.
TABLE 8
Gas Orifice Size
Unit
Fuel
Orifice Size
All
Natural
0.0625
All
L.P./Propane
0.034
Primary Limit Location and Heat Exchanger
Burner Detail Top Vie­
w
SENSOR
IGNITOR
ORIFICES
FIGURE 13
7. Gas Valve (GV1)
Install limit face down
FIGURE 12
5. Heat Exchanger (Figure 12)
ML193DF units use an aluminized steel primary and stain­
less steel secondary heat exchanger assembly. Heat is
transferred to the air stream from all surfaces of the heat
exchanger. The shape of the heat exchanger ensures
maximum efficiency.
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 pri­
mary and secondary heat exchangers and exhausted out
the exhaust vent pipe.
6. Burners (Figure 13)
The ML193DF uses an internally redundant to valve to as­
sure 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 connected 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
LPG changeover kit is available.
MANIFOLD
PRESSURE
ADJUSTMENT
SCREW
(under
barbed
fitting)
All units use inshot burners. Burners are factory set and do
not require adjustment. Burners can be removed as an as­
sembly for service. Burner maintenance and service is de­
tailed in the MAINTENANCE section of this manual. Each
burner uses an orifice which is precisely matched to the
Page 15
Gas Valve
MANIFOLD
PRESSURE
OUTLET
PORT
INLET
PRESSURE
PORT
FIGURE 14
8. Combustion Air Inducer (B6)
& Cold End Header Box
Pressure Switch
All ML193DF units use a combustion air inducer to move air
through the burners and heat exchanger during heating op­
eration. The blower uses a shaded pole 120VAC motor.
The motor operates during all heating operation and is con­
trolled by burner ignition control A3. Blower operates con­
tinuously while there is a call for heat. The burner ignition
control will not proceed with the ignition sequence until
combustion air inducer operation is sensed by the proving
switches.
The CAI is installed on the cold end header box. The cold
end header box is a single piece made of hard plastic. The
box has an internal channel where the combustion air in­
ducer creates negative pressure at unit start up. The chan­
nel contains an orifice used to regulate flow created by the
CAI. The box has pressure taps for the CAI pressure switch
hoses. The pressure switch measure the pressure across
the CAI 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 CAI to the box, must
also be replaced.
TABLE 9
ML193DF Unit
C.A.I. Orifice Size
-045
0.618
-070
0.891
-090
1.031
-110
1.297
9. Combustion Air Pressure Switch
(Figure 15)
ML193DF series units are equipped with a differential pres­
sure switch located on the cold end header box. The
switches monitor across the CAI orifice to insure proper
flow through the heat exchanger.
The switch is a SPST N.O. prove 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.
24VAC
TERMINALS
BRACKET
TAP
TAP
FIGURE 15
On start‐up, the switch senses that the combustion air in­
ducer is operating. It closes a circuit to the ignition control
when the difference in pressure across the CAI orifice ex­
ceeds a non-adjustable factory setting. If the switch does
not successfully sense the required differential, the switch
cannot close and the furnace cannot operate. If the flue or
air inlet become obstructed during operation, the switch
senses a loss of pressure differential and opens the circuit
to the ignition control. If the condensate line is blocked, wa­
ter will back up into the header box and reduce the pressure
differential across the switch. The prove switch opens if the
differential drops below the set point. See table 10.
Checks of pressure differential can aid in troubleshooting.
When measuring the pressure differential, readings should
be taken at the pressure switch. See figure 16. Lack of dif­
ferential usually indicates problems in the intake or exhaust
piping, but may indicate problems in the heat exchanger,
condensing coil, header boxes, combustion inducer or oth­
er components.
TABLE 10
Altitude ft
4501 0 - 4500
7501 - 10000
ML193DF
7500
Set Point
SetPoint
Set Point
-045
-070
-090
-110
-0.65
-0.60
*Set point is factory set and non-adjustable
Page 16
-0.55
Measuring Pressure Differential
RED TUBING
NEGATIVE
BLACK TUBING
POSITIVE
12-
Remove thermostat demand and allow unit to cycle off.
Install a tee in the negative (-) line (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 negative. How­
ever 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 10.
5-
Remove thermostat demand and allow to cycle off.
6-
Remove manometer and tee's. Reinstall combustion air
sensing hoses to the pressure switch.
FIGURE 16
C-Blower Compartment
1.Blower Motor (B3) and Capacitor (C4)
Blower motor (B3) and capacitor (C4), are located in the
blower compartment. The blower compartment can be ac­
cessed by removing the blower access panel.
All ML193DF units use single-phase direct-drive blower
motors. All motors are 120V permanent split capacitor mo­
tors to ensure maximum efficiency. See SPECIFI­
CATIONS table at the front of this manual for more detail.
See motor nameplate for capacitor ratings.
Blower Motor Housing
BOLTS
MOTOR
CAPACITOR
To Remove Blower From Unit: Disconnect Power, Remove Control
Box, Remove Bolts and Unplug Motor Wires From Control Board.
Then Slide Out Front of Unit.
FIGURE 17
Page 17
II-PLACEMENT AND INSTALLATION
IMPORTANT
Pipe & Fittings Specifications
All pipe, fittings, primer and solvent cement must conform
with American National Standard Institute and the Ameri­
can Society for Testing and Materials (ANSI/ASTM) stan­
dards. The solvent shall be free flowing and contain no
lumps, undissolved particles or any foreign matter that ad­
versely affects the joint strength or chemical resistance of
the cement. The cement shall show no gelation, stratifica­
tion, or separation that cannot be removed by stirring. Re­
fer to the table 11 below for approved piping and fitting ma­
terials.
CAUTION
Solvent cements for plastic pipe are flammable liq­
uids and should be kept away from all sources of
ignition. Do not use excessive amounts of solvent
cement when making joints. Good ventilation should
be maintained to reduce fire hazard and to minimize
breathing of solvent vapors. Avoid contact of ce­
ment with skin and eyes.
TABLE 11
PIPING AND FITTINGS SPECIFICATIONS
Schedule 40 PVC (Pipe)
Schedule 40 PVC (Cellular Core Pipe)
D1785
F891
Schedule 40 PVC (Fittings)
D2466
Schedule 40 CPVC (Pipe)
F441
Schedule 40 CPVC (Fittings)
F438
SDR-21 PVC or SDR-26 PVC (Pipe)
SDR-21 CPVC or SDR-26 CPVC (Pipe)
Schedule 40 ABS Cellular Core DWV (Pipe)
F442
F628
D1527
Schedule 40 ABS (Fittings)
D2468
ABS-DWV (Drain Waste & Vent)
(Pipe & Fittings)
D2661
PVC-DWV (Drain Waste & Vent)
Pipe & Fittings)
D2665
PVC & CPVC Primer
PVC Solvent Cement
CPVC Solvent Cement
ABS Solvent Cement
ASTM
SPECIFICATION
F656
D2564
F493
D2235
PVC/CPVC/ABS All Purpose Cement For
Fittings & Pipe of the same material
D2564, D2235, F493
ABS to PVC or CPVC Transition Solvent
Cement
D3138
CANADA PIPE & FITTING & SOLVENT
CEMENT
PVC & CPVC Pipe and Fittings
PVC & CPVC Solvent Cement
Use PVC primer and solvent cement or ABS solvent ce­
ment meeting ASTM specifications, refer to Table 11. As
an alternate, use all purpose cement, to bond ABS, PVC, or
CPVC pipe when using fittings and pipe made of the same
materials. Use transition solvent cement when bonding
ABS to either PVC or CPVC.
Low temperature solvent cement is recommended during
cooler weather. Metal or plastic strapping may be used for
vent pipe hangers. Uniformly apply a liberal coat of PVC
primer for PVC or use a clean dry cloth for ABS to clean in­
side socket surface of fitting and male end of pipe to depth
of fitting socket.
Canadian Applications Only - Pipe, fittings, primer and
solvent cement used to vent (exhaust) this appliance must
be certified to ULC S636 and supplied by a single
manufacturer as part of an approved vent (exhaust) sys­
tem. In addition, the first three feet of vent pipe from the fur­
nace flue collar must be accessible for inspection.
D2241
Schedule 40 ABS (Pipe)
PRIMER & SOLVENT CEMENT
ML193DF exhaust and intake connections are made
of PVC. Use PVC primer and solvent cement when
using PVC vent pipe. When using ABS vent pipe, use
transitional solvent cement to make connections to
the PVC fittings in the unit.
MARKING
ULCS636
ABS to PVC or CPVC Transition Cement
POLYPROPYLENE VENTING SYSTEM
PolyPro by Duravent
ULC-S636
Page 18
TABLE 12
OUTDOOR TERMINATION USAGE*
STANDARD
Input Size
045
070
090
110
Vent
Pipe
Dia. in.
Flush­
Mount
Kit
Wall Kit
CONCENTRIC
Wall Ring Kit
2 inch
1-1/2 inch
2 inch
71M80
(US)
444W92
(CA)
69M29
(US)
444W92
(CA)
3 inch
2 inch
3 inch
51W11
(US)
51W12
(CA)
22G44 (US)
430G28 (CA)
44J40
(US)
481J20 (CA)
15F74
2
3YES
YES
1YES
1YES
5YES
2YES
2-1/2
3YES
YES
1YES
1YES
5YES
2YES
3
3YES
YES
1YES
1YES
5YES
2YES
2
3YES
YES
1YES
1YES
5YES
2YES
2-1/2
3YES
YES
1YES
1YES
5YES
2YES
3
3YES
YES
1YES
1YES
5YES
2YES
2
3YES
YES
YES
5YES
YES
YES
2-1/2
3YES
YES
YES
5YES
YES
YES
3
3YES
YES
YES
5YES
YES
YES
2
YES
YES
YES
5YES
YES
YES
2-1/2
YES
YES
5YES
YES
YES
3
YES
YES
5YES
YES
YES
Field
Fabricated
60L46 (US)
(CA)
444W93
NOTE - Standard Terminations do not include any vent pipe or elbows external to the structure. Any vent pipe or elbows external to the structure must be included in total vent length
calculations. See vent length tables.
* Kits must be properly installed according to kit instructions.
1Requires field-provided outdoor 1-1/2” exhaust accelerator.
2Concentric kits 71M80 and 44W92 include 1-1/2” outdoor accelerator, when used with 045 and 070 input models.
3 Flush mount kit 51W11 and 51W12 includes 1-1/2 in. outdoor exhaust accelerator, required when used with 045, 070 and 090 input models.
4 Termination kits 30G28, 44W92, 4493 and 81J20 are certified to ULC S636 for use in Canada only.
5 See table 17 for vent accelerator requirements.
Page 19
Venting Practices
Joint Cementing Procedure
All cementing of joints should be done according to the
specifications outlined in ASTM D 2855.
Piping Suspension Guidelines
SCHEDULE 40
PVC - 5'
all other pipe* - 3'
NOTE - A sheet metal screw may be used to secure the
intake pipe to the connector, if desired. Use a drill or
self tapping screw to make a pilot hole.
DANGER
* See table 11 for allowable pipe.
DANGER OF EXPLOSION!
Fumes from PVC glue may ignite during system
check. Allow fumes to dissipate for at least 5 minutes
before placing unit into operation.
NOTE - Isolate piping at the point where it exits the outside wall or
roof in order to prevent transmission of vibration to the structure.
Wall Thickness Guidelines
24” maximum
3/4” minimum
1 - Measure and cut vent pipe to desired length.
2 - Debur and chamfer end of pipe, removing any ridges
or rough edges. If end is not chamfered, edge of pipe
may remove cement from fitting socket and result in a
leaking joint.
3 - Clean and dry surfaces to be joined.
4 - Test fit joint and mark depth of fitting on outside of
pipe.
5 - Uniformly apply a liberal coat of PVC primer for PVC or
use a clean dry cloth for ABS to clean inside socket
surface of fitting and male end of pipe to depth of fitting
socket.
6 - Promptly apply solvent cement to end of pipe and in­
side socket surface of fitting. Cement should be ap­
plied lightly but uniformly to inside of socket. Take care
to keep excess cement out of socket. Apply second
coat to end of pipe.
NOTE - Time is critical at this stage. Do not allow prim­
er to dry before applying cement.
7 - Immediately after applying last coat of cement to pipe,
and while both inside socket surface and end of pipe
are wet with cement, forcefully insert end of pipe into
socket until it bottoms out. Turn PVC pipe 1/4 turn dur­
ing assembly (but not after pipe is fully inserted) to dis­
tribute cement evenly. DO NOT turn ABS or cellular
core pipe.
NOTE - Assembly should be completed within 20 sec­
onds after last application of cement. Hammer blows
should not be used when inserting pipe.
8 - After assembly, wipe excess cement from pipe at end
of fitting socket. A properly made joint will show a bead
around its entire perimeter. Any gaps may indicate an
improper assembly due to insufficient solvent.
9 - Handle joints carefully until completely set.
inside
Wall
FIGURE 18
CHIMNEY
OR GAS
VENT
(Check sizing
for water
heater only)
FURNACE
(Replaced
by ML193)
REPLACING FURNACE THAT
WAS PART OF A COMMON
VENT SYSTEM
WATER
HEATER
OPENINGS
(To Adjacent
Room)
If an ML193DF furnace replaces a furnace which was com­
monly vented with another gas appliance, the size of the ex­
isting vent pipe for that gas appliance must be checked.
Without the heat of the original furnace flue products, the
existing vent pipe is probably oversized for the single water
heater or other appliance. The vent should be checked for
proper draw with the remaining appliance.
FIGURE 19
Page 20
outside
1. In areas where piping penetrates joists or interior
walls, hole must be large enough to allow clearance on
all sides of pipe through center of hole using a hanger.
2. When furnace is installed in a residence where unit is
shut down for an extended period of time, such as a
vacation home, make provisions for draining conden­
sate collection trap and lines.
Exhaust Piping (Figures 21 and 22)
Route piping to outside of structure. Continue with installa­
tion following instructions given in piping termination sec­
tion.
The ML193DF can be installed as either a Non-Direct
Vent or a Direct Vent gas central furnace.
NOTE - In Direct Vent installations, combustion air is taken
from outdoors and flue gases are discharged outdoors. In
Non-Direct Vent installations, combustion air is taken from
indoors or ventilated attic or crawlspace and flue gases are
discharged outdoors.
Intake and exhaust pipe sizing -- Size pipe according to
tables 13 and 14. Count all elbows inside and outside the
home. Table 13 lists the minimum vent pipe lengths per­
mitted. Table 14 lists the maximum pipe lengths permitted.
TABLE 13
MINIMUM VENT PIPE LENGTHS
CAUTION
Do not discharge exhaust into an existing stack or
stack that also serves another gas appliance. If verti­
cal discharge through an existing unused stack is re­
quired, insert PVC pipe inside the stack until the end
is even with the top or outlet end of the metal stack.
CAUTION
The exhaust vent pipe operates under positive pres­
sure and must be completely sealed to prevent leak­
age of combustion products into the living space.
Vent Piping Guidelines
NOTE - Lennox has approved the use of DuraVent ® manu­
factured vent pipe and terminations as an option to PVC.
When using the PolyPro ® by DuraVent venting system the
vent pipe requirements stated in the unit installation in­
struction – minimum & maximum vent lengths, termination
clearances, etc. – apply and must be followed. Follow the
instructions provided with PoyPro by DuraVent venting
system for assembly or if requirements are more restrict­
ive. The PolyPro by Duravent venting system must also fol­
low the uninsulated and unconditioned space criteria listed
in table 16.
ML193DF
MODEL
MIN. VENT LENGTH*
045, 070, 090, 110
15 ft. or
5 ft plus 2 elbows or
10 ft plus 1 elbow
*Any approved termination may be added to the minimum length listed.
Regardless of the diameter of pipe used, the standard roof
and wall terminations described in section Exhaust Piping
Terminations should be used. Exhaust vent termination
pipe is sized to optimize the velocity of the exhaust gas as it
exits the termination. Refer to table 17.
In some applications which permit the use of several differ­
ent sizes of vent pipe, a combination vent pipe may be
used. Contact Lennox' Application Department for assis­
tance in sizing vent pipe in these applications.
IMPORTANT
Do not use screens or perforated metal in exhaust or
intake terminations. Doing so will cause freeze-ups
and may block the terminations.
Use the following steps to correctly size vent pipe diameter.
Page 21
Piping Size Process
1
2
3
What is the
furnace capacity?
045, 070, 090 or
110?
Which style termination
being used?
Standard or concentric?
See table 12.
NOTE - It is acceptable to use any pipe size which fits within
the guidelines allowed in table 14.
NOTE - All horizontal runs of exhaust pipe must slope back
toward unit. A minimum of 1/4” (6mm) drop for each 12”
(305mm) of horizontal run is mandatory for drainage.
NOTE - Exhaust pipe MUST be glued to furnace exhaust
fittings.
NOTE - Exhaust piping should be checked carefully to
make sure there are no sags or low spots.
Which needs
most elbows?
Intake or
exhaust?
How many elbows?
4 Count all elbows inside
and outside house.
5
Desired pipe size?
2”, 2-1/2”, 3”
6
What is the altitude of
the furnace installation?
7
Use table 14 or 15 to find
max intake or exhaust pipe
length. Includes all vent
pipe and elbows inside
and outside the house.
FIGURE 20
Page 22
TABLE 14
Maximum Allowable Intake or Exhaust Vent Length in Feet
*Size intake and exhaust pipe length separately. Values in table are for Intake OR Exhaust, not combined total. Both Intake and Exhaust must be same pipe
size.
NOTE - Additional vent pipe and elbows used to terminate the vent pipe outside the structure must be included in the total vent length calculation.
Standard Termination at Elevation 0 - 10,000 ft.
2” Pipe
2-1/2” Pipe
Number
Of 90°
Elbows
Used
045
070
090
1
61
46
2
56
3
Model
3” Pipe
Model
110
Model
045
070
090
24
100
80
41
19
95
51
36
14
4
46
31
5
41
26
6
36
21
7
31
16
8
26
11
9
21
10
16
n/a
n/a
n/a
110
045
070
090
110
43
127
127
108
108
75
38
122
122
103
103
90
70
33
117
117
98
98
85
65
28
112
112
93
93
80
60
23
107
107
88
88
75
55
18
102
102
83
83
70
50
13
97
97
78
78
65
45
92
92
73
73
60
40
87
87
68
68
55
35
82
82
63
63
n/a
n/a
Concentric Termination Elevation 0 - 10,000 ft.
2” Pipe
2-1/2” Pipe
Model
Model
Number
Of 90°
Elbows
Used
045
070
090
1
53
38
2
48
33
3
43
28
4
38
5
Model
045
070
090
22
90
70
17
85
65
12
80
23
33
18
6
28
13
7
23
8
18
9
13
10
n/a
110
n/a
n/a
n/a
3” Pipe
110
045
070
090
110
39
111
111
104
104
34
106
106
99
99
60
29
101
101
94
94
75
55
24
96
96
89
89
70
50
19
91
91
84
84
65
45
14
86
86
79
79
60
40
81
81
74
74
55
35
76
76
69
69
50
30
71
71
64
64
45
25
66
66
59
59
n/a
n/a
TABLE 15
Maximum Allowable Exhaust Vent Lengths With Furnace Installed in a Closet or Basement Using Ventilated
Attic or Crawl Space For Intake Air in Feet
NOTE - Additional vent pipe and elbows used to terminate the vent pipe outside the structure must be included in the total vent length calculation.
Standard Termination at Elevation 0 - 10,000 ft.
2” Pipe
2-1/2” Pipe
Number
Of 90°
Elbows
Used
045
070
090
1
51
36
2
46
3
Model
3” Pipe
Model
Model
045
070
090
045
070
14
85
65
090
110
28
107
107
88
31
9
80
88
60
23
102
102
83
41
26
4
83
75
55
18
97
97
78
78
4
36
5
31
21
70
50
13
92
92
73
73
16
65
45
8
87
87
68
6
26
11
68
60
40
3
82
82
63
7
21
6
63
55
35
77
77
58
8
16
1
58
50
30
72
72
53
9
11
53
45
25
67
67
48
10
6
48
40
20
62
62
43
43
n/a
110
n/a
n/a
Page 23
n/a
110
n/a
TYPICAL EXHAUST PIPE CONNECTIONS
Pipe size determined in table 14.
2”
2”
2”
2”
2”
or
3”
TRANSITION
*2”
DO NOT transition from smaller
to larger pipe size in horizontal
runs of exhaust pipe.
INTAKE
EXHAUST
TOP VIEW
* When transitioning up in pipe size, use the shortest length of 2” PVC pipe possible.
NOTE − Exhaust pipe and intake pipe must be the same diameter.
FIGURE 21
TYPICAL INTAKE PIPE CONNECTIONS
Pipe size determined in table 14.
2”
2”
2”
2”
2”
or
TRANSITION
3”
*2”
3”
*2”
TRANSITION
*2”
INTAKE
EXHAUST
TOP VIEW
* When transitioning up in pipe size, use the shortest length of 2” PVC pipe possible.
NOTE − Intake pipe and exhaust pipe must be the same diameter.
FIGURE 22
Follow the next two steps when installing the unit in Direct
Vent applications, where combustion air is taken from
The ML193DF furnace may be installed in either direct
outdoors
and flue gases are discharged outdoors. The
vent or non-direct vent applications. In non-direct vent
provided
air intake screen must not be used in direct
applications, when intake air will be drawn into the furnace
vent applications (outdoors).
from the surrounding space, the indoor air quality must be
Intake Piping
considered. Guidelines listed in Combustion, Dilution and
Ventilation Air section must be followed.
1 - Use cement to secure the intake pipe to the inlet air
connector.
Page 24
2 - Route piping to outside of structure. Continue with
installation following instructions given in general
guide lines for piping terminations and intake and ex­
haust piping terminations for direct vent sections. Re­
fer to table 14 for pipe sizes.
EQUIPMENT IN CONFINED SPACE
(Inlet Air from Ventilated Attic and Outlet Air to Outside)
Ventilation Louvers
Inlet Air
(Minimum
12 in.(305mm) Above
attic floor)
Roof Terminated
Exhaust Pipe
TYPICAL AIR INTAKE PIPE CONNECTIONS
NON−DIRECT VENT APPLICATIONS
*Intake Debris
Screen
(Provided)
AIR
INTAKE
SCREEN
(Provided)
Furnace
* See table 15 for maximum vent lengths
NOTE-The inlet and outlet air openings shall each have a free area
of at least one square inch per 4,000 Btu (645mm 2 per 1.17kW) per
hour of the total input rating of all equipment in the enclosure.
FIGURE 24
EQUIPMENT IN CONFINED SPACE
(Inlet Air from Ventilated Crawlspace and Outlet Air to Outside)
Roof Terminated
Exhaust Pipe
NOTE - Air intake screen and elbow may be rotated, so that
screen may be positioned to face forward or to either side.
FIGURE 23
Follow the next two steps when installing the unit in Non‐
Direct Vent applications where combustion air is taken
from indoors and flue gases are discharged outdoors.
Ventilation
Louvers
(Crawl space)
1 - Use field-provided materials and the factory-provided
air intake screen to route the intake piping as shown in
figure 23. Maintain a minimum clearance of 3” (76mm)
around the air intake opening. The air intake opening
(with the protective screen) should always be directed
forward, or sideways.
2 - If intake air is drawn from a ventilated attic (figure 24)
or ventilated crawlspace (figure 25) the exhaust vent
length must not exceed those listed in table 15. If 3” di­
ameter pipe is used, reduce to 2” diameter pipe at the
termination point to accommodate the debris screen.
3 - Use cement to secure the intake pipe to the connector,
if desired.
CAUTION
If this unit is being installed in an application with
combustion air coming in from a space serviced by
an exhaust fan, power exhaust fan, or other device
which may create a negative pressure in the space,
take care when sizing the inlet air opening. The in­
let air opening must be sized to accommodate the
maximum volume of exhausted air as well as the
maximum volume of combustion air required for
all gas appliances serviced by this space.
Furnace
Coupling or
3 in. to 2 in.
Transition
(Field Provided)
Inlet Air
(Minimum
12 in.(305mm)
Above crawl
space floor)
*Intake Debris Screen Provided)
* See table 15 for maximum vent lengths
NOTE-The inlet and outlet air openings shall each have a free area
of at least one square inch per 4,000 Btu (645mm 2 per 1.17kW) per
hour of the total input rating of all equipment in the enclosure.
FIGURE 25
General Guidelines for Vent Terminations
In Non‐Direct Vent applications, combustion air is taken
from indoors and the flue gases are discharged to the out­
doors. The ML193DF is then classified as a non‐direct
vent, Category IV gas furnace.
In Direct Vent applications, combustion air is taken from
outdoors and the flue gases are discharged to the out­
doors. The ML193DF is then classified as a direct vent,
Category IV gas furnace.
In both Non‐Direct Vent and Direct Vent applications, the
vent termination is limited by local building codes. In the ab­
sence of local codes, refer to the current National Fuel Gas
Code ANSI Z223-1/NFPA 54 in U.S.A., and current CSAB149 Natural Gas and Propane Installation Codes in Can­
ada for details.
Page 25
closed areas that are not exposed to the outdoor ambient
temperature and are above 32 degrees F (0°C) are to be
considered conditioned spaces.
Position termination according to location given in figure 27
or 28. In addition, position termination so it is free from any
obstructions and 12” above the average snow accumula­
tion.
At vent termination, care must be taken to maintain
protective coatings over building materials (prolonged
exposure to exhaust condensate can destroy protective
coatings). It is recommended that the exhaust outlet not be
located within 6 feet (1.8m) of a condensing unit because
the condensate can damage the painted coating.
NOTE - See table 16 for maximum allowed exhaust pipe
length without insulation in unconditioned space during
winter design temperatures below 32°F (0°C). If required
exhaust pipe should be insulated with 1/2” (13mm) Arma­
flex or equivalent. In extreme cold climate areas, 3/4”
(19mm) Armaflex or equivalent may be necessary. Insula­
tion must be protected from deterioration. Armaflex with
UV protection is permissable. Basements or other en­
IMPORTANT
Do not use screens or perforated metal in exhaust
terminations. Doing so will cause freeze-ups and
may block the terminations.
IMPORTANT
For Canadian Installations Only:
In accordance to CSA International B149 installation
codes, the minimum allowed distance between the
combustion air intake inlet and the exhaust outlet of
other appliances shall not be less than 12 inches
(305mm).
TABLE 16
Maximum Allowable Exhaust Vent Pipe Length (in ft.) Without Insulation In Unconditioned Space For
Winter Design Temperatures Single - Stage High Efficiency Furnace
Winter Design
Temperatures1 °F (°C)
32 to 21
(0 to -6)
20 to 1
(-7 to -17)
0 to -20
(-18 to -29)
Vent Pipe
Diameter
2 in.
2-1/2 in.
3 in.
2 in
2-1/2 in.
3 in.
2 in.
2-1/2 in.
3 in.
045
PVC
26
18
14
16
12
9
10
8
4
070
2PP
24
N/A
12
15
N/A
8
9
N/A
3
2PP
PVC
44
32
26
28
20
16
20
14
10
41
N/A
23
26
N/A
14
18
N/A
8
Unit Input Size
090
2PP
PVC
44
44
50
N/A
38
33
40
37
30
N/A
26
23
30
28
20
N/A
16
14
110
PVC
24
58
55
24
44
32
24
32
26
1Refer
135
2PP
24
N/A
49
24
N/A
28
24
N/A
23
PVC
N/A
N/A
60
N/A
N/A
40
N/A
N/A
30
2PP
N/A
N/A
53
N/A
N/A
35
N/A
N/A
26
to 99% Minimum Design Temperature table provided in the current edition of the ASHRAE Fundamentals Handbook.
vent pipe (PP)
NOTE - Maximum uninsulated vent lengths listed may include the termination(vent pipe exterior to the structure) and cannot exceed 5 linear feet or the
maximum allowable intake or exhaust vent length listed in table 14 or 15 which ever is less.
NOTE - If insulation is required in an unconditioned space, it must be located on the pipe closest to the furnace. See figure26.
2 Poly-Propylene
Conditioned
Space
Pipe Insulation
Conditioned
Space
Unconditioned
Space
FIGURE 26
Page 26
Exhaust
Pipe
Intake
Pipe
VENT TERMINATION CLEARANCES
FOR NON-DIRECT VENT INSTALLATIONS IN THE USA AND CANADA
INSIDE CORNER
DETAIL
G
H
A
D
E
B
L
Fixed
Closed
Operable
F
B
B
C
I
Fixed
Closed
Operable
M
B
K
J
A
B
AREA WHERE TERMINAL
IS NOT PERMITTED
AIR SUPPLY INLET
VENT TERMINAL
US Installations1
A=
Clearance above grade, veranda,
porch, deck or balcony
B=
Clearance to window or
door that may be opened
C=
Clearance to permanently
closed window
D=
Vertical clearance to ventilated soffit
located above the terminal within a
horizontal distance of 2 feet (610 mm)
from the center line of the terminal
E=
Clearance to unventilated soffit
F=
Clearance to outside corner
G=
12 inches (305mm) or 12 in. (305mm)
above average snow accumulation.
4 feet (1.2 m) below or to side of opening;
1 foot (30cm) above opening
Canadian Installations2
12 inches (305mm) or 12 in. (305mm)
above average snow accumulation.
6 inches (152mm) for appliances <10,000
Btuh (3kw), 12 inches (305mm) for
appliances > 10,000 Btuh (3kw) and
<100,000 Btuh (30kw), 36 inches (.9m)
for appliances > 100,000 Btuh (30kw)
* 12”
* 12”
* Equal to or greater than soffit depth.
* Equal to or greater than soffit depth.
* Equal to or greater than soffit depth.
* No minimum to outside corner
*
Clearance to inside corner
* Equal to or greater than soffit depth.
* No minimum to outside corner
*
H=
Clearance to each side of center line ex­
tended above meter / regulator assembly
* 3 feet (.9m) within a height 15 feet (4.5m)
above the meter / regulator assembly
3 feet (.9m) within a height 15 feet (4.5m)
above the meter / regulator assembly
I=
Clearance to service regulator
vent outlet
Clearance to non-mechanical air
supply inlet to building or the com­
bustion air inlet to any other ap­
pliance
* 3 feet (.9m)
3 feet (.9m)
J=
K=
L=
M=
4 feet (1.2 m) below or to side of opening;
1 foot (30 cm) above opening
Clearance to mechanical air sup­
ply inlet
Clearance above paved sidewalk or
paved driveway located on public property
Clearance under veranda, porch, deck or balcony
3 feet (.9m) above if within 10 feet
(3m) horizontally
7 feet (2.1m)†
7 feet (2.1m)†
*12 inches (305mm)‡
1 In
2 In
accordance with the current ANSI Z223.1/NFPA 54 Natural Fuel Gas Code
accordance with the current CSA B149.1, Natural Gas and Propane Installation Code
† A vent shall not terminate directly above a sidewalk or paved driveway that is
located between two single family dwellings and serves both dwellings.
‡ Permitted only if veranda, porch, deck or balcony is fully open
on a minimum of two sides beneath the floor. Lennox recommends
avoiding this location if possible.
FIGURE 27
Page 27
6 inches (152mm) for appliances <10,000
Btuh (3kw), 12 inches (305mm) for
appliances > 10,000 Btuh (3kw) and
<100,000 Btuh (30kw), 36 inches (.9m)
for appliances > 100,000 Btuh (30kw)
6 feet (1.8m)
12 inches (305mm)‡
*For clearances not specified in ANSI Z223.1/NFPA 54 or CSA
B149.1, clearance will be in accordance with local installation
codes and the requirements of the gas supplier and these instal­
lation instructions.”
VENT TERMINATION CLEARANCES
FOR DIRECT VENT INSTALLATIONS IN THE USA AND CANADA
INSIDE CORNER
DETAIL
G
H
A
D
E
B
L
Fixed
Closed
Operable
F
B
B
C
I
Fixed
Closed
Operable
M
B
A
K
J
B
AREA WHERE TERMINAL
IS NOT PERMITTED
AIR SUPPLY INLET
VENT TERMINAL
US Installations1
A=
Clearance above grade, veranda,
porch, deck or balcony
B=
Clearance to window or
door that may be opened
C=
Clearance to permanently
closed window
D=
Vertical clearance to ventilated soffit
located above the terminal within a
horizontal distance of 2 feet (610mm)
from the center line of the terminal
E=
Clearance to unventilated soffit
F=
Clearance to outside corner
G=
Clearance to inside corner
H=
Clearance to each side of center line ex­
tended above meter / regulator assembly
I=
Clearance to service regulator
vent outlet
Clearance to non-mechanical air
supply inlet to building or the com­
bustion air inlet to any other ap­
pliance
J=
K=
L=
Clearance to mechanical air sup­
ply inlet
Clearance above paved sidewalk or
paved driveway located on public property
12 inches (305mm) or 12 in. (305mm)
above average snow accumulation.
1 In
12 inches (305mm) or 12 in. (305mm)
above average snow accumulation.
6 inches (152mm) for appliances <10,000 6 inches (152mm) for appliances <10,000
Btuh (3kw), 9 inches (228mm) for ap­
Btuh (3kw), 12 inches (305mm) for
pliances > 10,000 Btuh (3kw) and <50,000
appliances > 10,000 Btuh (3kw) and
Btuh (15 kw), 12 inches (305mm) for ap­
<100,000 Btuh (30kw), 36 inches (.9m)
pliances > 50,000 Btuh (15kw)
for appliances > 100,000 Btuh (30kw)
* 12”
* 12”
* Equal to or greater than soffit depth
* Equal to or greater than soffit depth
* No minimum to outside corner
*
* 3 feet (.9m)
* Equal to or greater than soffit depth
* Equal to or greater than soffit depth
* No minimum to outside corner
*
3 feet (.9m) within a height 15 feet (4.5m)
above the meter / regulator assembly
3 feet (.9m) within a height 15 feet (4.5m)
above the meter / regulator assembly
3 feet (.9m)
6 inches (152mm) for appliances <10,000 6 inches (152mm) for appliances <10,000
Btuh (3kw), 9 inches (228mm) for ap­
Btuh (3kw), 12 inches (305mm) for
pliances > 10,000 Btuh (3kw) and <50,000
appliances > 10,000 Btuh (3kw) and
Btuh (15 kw), 12 inches (305mm) for ap­
<100,000 Btuh (30kw), 36 inches (.9m)
pliances > 50,000 Btuh (15kw)
for appliances > 100,000 Btuh (30kw)
3 feet (.9m) above if within 10 feet
6 feet (1.8m)
(3m) horizontally
7 feet (2.1m)†
* 7 feet (2.1m)
M = Clearance under veranda, porch, deck or balcony
2 In
Canadian Installations2
*12 inches (305mm)‡
accordance with the current ANSI Z223.1/NFPA 54 Natural Fuel Gas Code
accordance with the current CSA B149.1, Natural Gas and Propane Installation Code
† A vent shall not terminate directly above a sidewalk or paved driveway that is located
between two single family dwellings and serves both dwellings.
‡ Permitted only if veranda, porch, deck or balcony is fully open on a minimum of
two sides beneath the floor. Lennox recommends avoiding this location if possible.
FIGURE 28
Page 28
12 inches (305mm)‡
*For clearances not specified in ANSI Z223.1/NFPA 54 or CSA
B149.1, clearance will be in accordance with local installation
codes and the requirements of the gas supplier and these
installation instructions.”
Details of Intake and Exhaust Piping Terminations for
Direct Vent Installations
NOTE - In Direct Vent installations, combustion air is taken
from outdoors and flue gases are discharged to outdoors.
NOTE - Flue gas may be slightly acidic and may adversely
affect some building materials. If any vent termination is
used and the flue gasses may impinge on the building ma­
terial, a corrosion-resistant shield (minimum 24 inches
square) should be used to protect the wall surface. If the
optional tee is used, the protective shield is recommended.
The shield should be constructed using wood, plastic,
sheet metal or other suitable material. All seams, joints,
cracks, etc. in the affected area should be sealed using an
appropriate sealant. See figure 36.
Intake and exhaust pipes may be routed either horizontally
through an outside wall or vertically through the roof. In at­
tic or closet installations, vertical termination through the
roof is preferred. Figures 31 through 37 show typical ter­
minations.
1. Intake and exhaust terminations are not required to be
in the same pressure zone. You may exit the intake on
one side of the structure and the exhaust on another
side (figure 29). You may exit the exhaust out the roof
and the intake out the side of the structure (figure 30).
2. Intake and exhaust pipes should be placed as close
together as possible at termination end (refer to il­
lustrations). Maximum separation is 3” (76mm) on roof
terminations and 6” (152mm) on side wall termina­
tions.
NOTE - When venting in different pressure zones, the
maximum separation requirement of intake and ex­
haust pipe DOES NOT apply.
3. On roof terminations, the intake piping should termi­
nate straight down using two 90° elbows (See figure
31).
4. Exhaust piping must terminate straight out or up as
shown. A reducer may be required on the exhaust pip­
ing at the point where it exits the structure to improve
the velocity of exhaust away from the intake piping.
See table 17.
TABLE 17
NOTE - Care must be taken to avoid recirculation of
exhaust back into intake pipe.
Exiting Exhaust and Intake Vent
(different pressure zones)
Exhaust
Pipe
FIGURE 29
Exiting Exhaust and Intake Vent
(different pressure zones)
Roof Terminated
Exhaust Pipe
Exhaust Pipe Size
Termination
Pipe Size
*045 and *070
*090
110
2” (51mm), 2-1/2” (64mm),
3” (76mm)
3” (76mm)
1-1/2” (38mm)
2” (51mm)
2” (51mm)
Inlet Air
(Minimum 12 in.
305 MM) above
grade or snow
accumulation
Furnace
FIGURE 30
Inches(mm)
EXHAUST PIPE TERMINATION SIZE REDUCTION
ML193
MODEL
Inlet Air
(Minimum 12 in.
305 MM) above
grade or snow
accumulation
Furnace
3”(76mm) MAX.
SIZE TERMINATION
PIPE PER TABLE 17.
UNCONDITIONED
ATTIC SPACE
8” (203mm) MIN
*ML193DF-045, -070 and -090 units with the flush-mount termination
must use the 1-1/2”accelerator supplied with the kit.
1/2” (13mm) FOAM
INSULATION IN
UNCONDITIONED
SPACE
12” (305mm) ABOVE
AVERAGE SNOW
ACCUMULATION
5. On field-supplied terminations for side wall exit, ex­
haust piping may extend a maximum of 12 inches
(305mm) for 2” PVC and 20 inches (508mm) for 3”
(76mm) PVC beyond the outside wall. Intake piping
should be as short as possible. See figure 36.
6. On field supplied terminations, a minimum distance
between the end of the exhaust pipe and the end of the
intake pipe without a termination elbow is 8” and a
minimum distance of 6” with a termination elbow. See
figure 36.
Page 29
3” (76mm) OR
2” (51mm) PVC
PROVIDE SUPPORT
FOR INTAKE AND
EXHAUST LINES
DIRECT VENT ROOF TERMINATION KIT
(15F75 or 44J41)
FIGURE 31
7.
If intake and exhaust piping must be run up a side wall
to position above snow accumulation or other ob­
structions, piping must be supported. At least one
bracket must be used within 6” from the top of the el­
bow and then every 24” (610mm) as shown in figure
36, to prevent any movement in any direction. When
exhaust and intake piping must be run up an outside
wall, the exhaust piping must be terminated with pipe
sized per table 17.The intake piping may be equipped
with a 90° elbow turndown. Using turndown will add 5
feet (1.5m) to the equivalent length of the pipe.
8. A multiple furnace installation may use a group of up to
four terminations assembled together horizontally, as
shown in figure 34.
EXHAUST
VENT
INTAKE
AIR
18” MAX.
(457mm)
INTAKE
Minimum
Above Average
Snow
Accumulation
12” (305mm) Min.
above grade or
average snow ac­
INTAKE
cumulation.
AIR
Inches (mm)
Side View
optional intake elbow
OPTIONAL VENT TERMINATION FOR MULTIPLE UNIT
INSTALLATION OF DIRECT VENT WALL TERMINATION KIT
(30G28 or 81J20)
FIGURE 34
2” EXTENSION FOR 2” PVC
PIPE1” EXTENSION FOR 3”
PVC PIPE
FLASHING
(Not Furnished)
FURNACE
EXHAUST
PIPE
4''
FURNACE
INTAKE
PIPE
SHEET METAL STRAP
(Clamp and sheet metal strap
must be field installed to support
the weight of the termination kit.)
GLUE EXHAUST
END FLUSH INTO
TERMINATION
CLAMP
FIELD-PROVIDED
REDUCER MAY BE REQUIRED
TO ADAPT LARGER VENT
PIPE SIZE TO TERMINATION
FLAT
SIDE
FLUSH-MOUNT SIDE WALL TERMINATION
51W11 (US) or 51W12 (Canada)
FIGURE 35
FIGURE 32
FIELD-PROVIDED
REDUCER MAY BE
REQUIRED TO ADAPT
LARGER VENT PIPE
SIZE TO TERMINA­
TION
OUTSIDE
WALL
EXHAUST
AIR
1-1/2” (38mm) accelerator
provided on 71M80 &
44W92 kits for
ML193DF045P36B- &
070P36B
INTAKE
AIR
EXHAUST
AIR
CLAMP
(Not Furnished)
1-1/2” ACCELERATOR
(all -45, -070 and -090 units)
DIRECT VENT CONCENTRIC ROOFTOP TERMINATION
71M80, 69M29 or 60L46 (US)
41W92 or 41W93 (Canada)
INTAKE
AIR
Front View
EXHAUST VENT
1-1/2” (38mm) accelerator
provided on 71M80 & 44W92
kits for ML193DF045P36B- &
070P36B
12” (305mm)
12”
(305mm)
5-1/2”
(140mm)
5”
(127mm)
INTAKE 12” (305mm) Min.
AIR
above grade or
average snow ac­
cumulation.
GRADE
DIRECT VENT CONCENTRIC WALL TERMINATION
71M80, 69M29 or 60L46 (US)
41W92 or 41W93 (Canada)
FIGURE 33
Page 30
FIELD FABRICATED WALL TERMINATION
NOTE − FIELD−PROVIDED
REDUCER MAY BE
REQUIRED TO ADAPT
LARGER VENT PIPE SIZE
TO TERMINATION
2” (51mm) 3” (76mm)
Vent Pipe Vent Pipe
D
D
B
Intake
Elbow
C1
A
B
C2
A
STRAIGHT
APPPLICATION
A− Minimum clearance
above grade or average
snow accumulation
12” (305 mm)
12” (305 mm)
B− Maximum horizontal
separation between
intake and exhaust
6” (152 mm)
6” (152 mm)
C1 -Minimum from end of
exhaust to inlet of intake 8” (203 mm)
8” (203 mm)
C2 -Minimum from end of
exhaust to inlet of intake 6” (152 mm)
6” (152 mm)
D− Maximum exhaust
pipe length
20” (508 mm)
12” (305 mm)
E− Maximum wall support
distance from top of each 6” (152 mm)
pipe (intake/exhaust)
* WALL
SUPPORT
D
D
E
E
B
B
A
C1
EXTENDED
APPLICATION
A
C2
6” (152 mm)
See venting table 14 for maximum venting lengths
with this arrangement.
* Use wall support every 24” (610 mm). Use two
wall supports if extension is greater than
24” (610 mm) but less than 48” (1219 mm).
NOTE − One wall support must be within 6” (152 mm)
from top of each pipe (intake and exhaust) to prevent
movement in any direction.
ALTERNATE TERMINATIONS (TEE & FORTY−FIVE DEGREE ELBOWS ONLY)
B
D
B
Exhaust
D
1
C
C
2
Intake
Elbow
A
3
1
E
Intake
B
B− Horizontal
separation between
intake and exhaust
C− Minimum from
end of exhaust to
inlet of intake
A
Front View of
Intake and Exhaust
D
A− Clearance above
grade or average snow
accumulation
D− Exhaust pipe length
2” (51MM)
Vent Pipe
3” (76MM)
Vent Pipe
12” (305 mm) Min.
12” (305 mm) Min.
6” (152 mm) Min.
6” (152 mm) Min.
24” (610 mm) Max. 24” (610 mm) Max.
9” (227 mm) Min.
9” (227 mm) Min.
12” (305 mm) Min. 12” (305 mm) Min.
16” (405 mm) Max. 20” (508 mm) Max.
E− Wall support distance
from top of each pipe
6” (152 mm) Max.
(intake/exhaust)
6” (152 mm) Max.
Exhaust
12”
C
2
A
1
The exhaust termination tee should be connected to the 2” or 3” PVC flue pipe as shown in the illustration.
Do not use an accelerator in applications that include an exhaust termination tee.
The accelerator is not required.
2 As required. Flue gas may be acidic and may adversely affect some building materials. If a side wall vent
termination is used and flue gases will impinge on the building materials, a corrosion−resistant shield
(24 inches square) should be used to protect the wall surface. If optional tee is used, the protective shield
is recommended. The shield should be constructed using wood, sheet metal or other suitable material.
All seams, joints, cracks, etc. in affected area, should be sealed using an appropriate sealant.
3 Exhaust pipe 45° elbow can be rotated to the side away from the combustion air inlet to direct exhaust
away from adjacent property. The exhaust must never be directed toward the combustion air inlet.
FIGURE 36
Page 31
2. On field supplied terminations for side wall exit, ex­
haust piping may extend a maximum of 12 inches
(305mm) for 2” PVC and 20 inches (508mm) for 3”
(76mm) PVC beyond the outside wall.
ML193DF DIRECT VENT APPLICATION
STRAIGHT-CUT OR
USING EXISTING CHIMNEY ANGLE-CUT
IN DIRECTION
OF ROOF SLOPE *
8” - 12”
(203mm - 305mm)
Minimum 12” (305MM)
above chimney top
plate or average snow
accumulation
3” - 8”
(76mm203mm)
EXHAUST VENT
1/2” (13mm)
WEATHERPROOF
INSULATION
3. If exhaust piping must be run up a side wall to position
above snow accumulation or other obstructions, pip­
ing must be supported every 24 inches (610mm).
When exhaust piping must be run up an outside wall,
any reduction in exhaust pipe size must be done after
the final elbow.
4. Distance between exhaust pipe terminations on mul­
tiple furnaces must meet local codes.
SHOULDER OF FITTINGS
PROVIDE SUPPORT
OF PIPE ON TOP PLATE
INTAKE PIPE
INSULATION (optional)
SHEET
METAL TOP
PLATE
ALTERNATE
INTAKE PIPE
3” - 8”
(76mm203mm)
INSULATE
TO FORM
SEAL
EXTERIOR
PORTION OF
CHIMNEY
ML193DF NON-DIRECT VENT APPLICATION
USING EXISTING CHIMNEY
*SIZE TERMINATION
PIPE PER TABLE 17.
STRAIGHT-CUT OR
ANGLE-CUT IN DIRECTION
OF ROOF SLOPE
SIZE TERMINATION
PIPE PER TABLE 17.
NOTE - Do not discharge exhaust gases directly into any chimney or vent stack. If ver­
tical discharge through an existing unused chimney or stack is required, insert piping
inside chimney until the pipe open end is above top of chimney and terminate as illus­
trated. In any exterior portion of chimney, the exhaust vent must be insulated.
FIGURE 37
Details of Exhaust Piping Terminations for Non‐Direct
Vent Applications
Exhaust pipes may be routed either horizontally through an
outside wall or vertically through the roof. In attic or closet
installations, vertical termination through the roof is pre­
ferred. Figures 38 through 39 show typical terminations.
1. Exhaust piping must terminate straight out or up as
shown. The termination pipe must be sized as listed in
table 17.The specified pipe size ensures proper ve­
locity required to move the exhaust gases away from
the building.
12” (305mm)
ABOVE AVE.
SNOW
ACCUMULATION
3” - 8”
(76mm203mm)
Minimum 12” (305MM)
above chimney top
plate or average snow
accumulation
SHOULDER OF FITTINGS
PROVIDE SUPPORT
OF PIPE ON TOP PLATE
SHEET
METAL TOP
PLATE
INSULATE
TO FORM
SEAL
3” - 8”
(76mm203mm)
EXTERIOR
PORTION OF
CHIMNEY
NOTE - Do not discharge exhaust gases directly into any chimney or vent stack. If ver­
tical discharge through an existing unused chimney or stack is required, insert piping
inside chimney until the pipe open end is above top of chimney and terminate as illus­
trated. In any exterior portion of chimney, the exhaust vent must be insulated.
SIZE TERMINATION
PIPE PER TABLE
17.
FIGURE 39
1/2” (13mm) FOAM
INSULATION
3” (76mm) OR
2” (51mm) PVC
EXHAUST VENT
1/2” (13mm)
WEATHERPROOF
INSULATION
UNCONDITIONED
ATTIC SPACE
PROVIDE SUPPORT
FOR EXHAUST LINES
NON-DIRECT VENT ROOF TERMINATION KIT
(15F75 or 44J41)
FIGURE 38
Page 32
Condensate Piping
This unit is designed for either right‐ or left‐side exit of con­
densate piping. Refer to figures 40 and 42 for condensate
trap locations.
NOTE - If necessary the condensate trap may be installed
up to 5’ away from the furnace. Use PVC pipe to connect
trap to furnace condensate outlet. Piping from furnace
must slope down a minimum of 1/4” per ft. toward trap.
CONDENSATE TRAP AND PLUG LOCATIONS
4 - Install drain trap using appropriate PVC fittings, glue
all joints. Glue the provided drain trap as shown in fig­
ures 46 and 47. Route the condensate line to an open
drain.
5 - Figure 44 shows the furnace and evaporator coil using
a separate drain. If necessary, the condensate line
from the furnace and evaporator coil can drain togeth­
er. See figures 45 and 43. The field provided vent must
be a minimum 1” to a maximum 2” length above the
condensate drain outlet connection.
NOTE - If necessary the condensate trap may be installed
up to 5 feet away from the furnace. Piping from furnace
must slope down a minimum of 1/4” per ft. toward trap.
NOTE - Appropriately sized tubing and barbed fitting may
be used for condensate drain. Attach to the drain on the
trap using a hose clamp. See figure 41.
Trap
(same on
right side)
1-1/2 in.
Field Provided Drain Components
Plug
(same on left
side)
Elbow
Barbed Fitting
Tubing
Hose Clamp
FIGURE 41
FIGURE 40
1 - Determine which side condensate piping will exit the
unit, location of trap, field-provided fittings and length
of PVC pipe required to reach available drain.
2 - For furnaces with a 1/2” drain connection use a 3/8 al­
len wrench and remove plug (figure 40) from the cold
end header box at the appropriate location on the side
of the unit. Install field-provided 1/2 NPT male fitting
into cold end header box. For furnaces with a 3/4”
drain connection use a large flat head screw driver or a
1/2” drive socket extension and remove plug. Install
provided 3/4 NPT street elbow fitting into cold end
header box. Use Teflon tape or appropriate pipe dope.
3 - Install the cap over the clean out opening at the base
of the trap. Secure with clamp. See figures 46 and 47.
6 - If unit will be started immediately upon completion of
installation, prime trap per procedure outlined in Unit
Start-Up section.
Condensate line must slope downward away from the
trap to drain. If drain level is above condensate trap,
condensate pump must be used. Condensate drain
line should be routed within the conditioned space to
avoid freezing of condensate and blockage of drain
line. If this is not possible, a heat cable kit may be used
on the condensate trap and line. Heat cable kit is avail­
able from Lennox in various lengths; 6 ft. (1.8m) - kit
no. 26K68; 24 ft. (7.3m) - kit no. 26K69; and 50 ft.
(15.2m) - kit no. 26K70.
Page 33
CAUTION
Do not use copper tubing or existing copper
condensate lines for drain line.
CONDENSATE TRAP LOCATION
(shown with right side exit of condensation)
ML193DF with Evaporator Coil
Using a Separate Drain
Field Provided Vent
1” min. 2” max. above
condensate drain.
Trap can be installed a maxi­
mum of 5ft. from furnace (*PVC
only)
Field Provided Vent
1” min. 2” max. above
condensate drain.
Condensate Drain
Connection
1” min.
2” max.
5’ max.
Evaporator Drain Line
(vent required)
Drain
to drain
*Piping from furnace must slope down a
minimum 1/4” per ft. toward trap
FIGURE 42
FIGURE 44
IMPORTANT
When combining the furnace and evaporator
coil drains together, the A/C condensate drain
outlet must be vented to relieve pressure in or­
der for the furnace pressure switch to operate
properly.
Condensate Trap With Optional Overflow Switch
From Evaporator Coil
Field Provided Vent
1” min. 2” max. above
condensate drain.
ML193DF with Evaporator
Coil Using a Common Drain
Field Provided Vent
1” min. 2” max. above
condensate drain.
FurnaceCondensate
Drain Connection
Optional
Condensate Drain
Connection
Evaporator Drain Line
(vent required)
FIGURE 43
FIGURE 45
Page 34
TRAP / DRAIN ASSEMBLY USING 1/2” PVC OR 3/4” PVC
COLD END HEADER BOX WITH 3/4” DRAIN CONNECTION
Optional Condensate Drain Connection
Adapter 3/4 inch slip X
3/4 inch mpt (not furnished)
90° Street Elbow
3/4 inch PVC
(not furnished)
Adapter 3/4 inch slip X
3/4 inch mpt (not furnished)
Condensate Drain
Connection In Unit
90° Street Elbow
3/4 inch PVC
( furnished)
1 (25 mm) Min.
2 (50 mm) Max.
Above Top Of
Condensate Drain
Connection In Unit
Vent
Condensate Drain
Connection In Unit
5 Feet
Maximum
90° Elbow 3/4 inch PVC
(Not Furnished)
To
Trap
Optional DrainPiping FromTrap
3/4 inch PVC Pipe
(Not Furnished)
1/2 inch PVC Pipe
(Not Furnished)
Coupling 3/4 inch slip X slip
(Not Furnished)
Drain Assembly for 1/2 inch Drain Pipe
1/2 inch PVC Pipe
(Not Furnished)
Drain Trap
Assembly
(Furnished)
90° Elbow
1/2 inch PVC
(Not Furnished)
To
Drain
Drain Assembly for 3/4 inch Drain Pipe
Drain Trap
Clean Out
90° Elbow
3/4 inch PVC
(Not Furnished)
90° Elbow
3/4 inch PVC
(Not Furnished)
To Coupling 3/4 inch slip X slip
Drain
(Not Furnished)
To
Drain
DrainTrap Assembly with 1/2 inch Piping
1 (25 mm) Min. 2 (50 mm) Max. Above Top
Of Condensate Drain Connection In Unit
DrainTrap Assembly
(Furnished)
Vent
1 (25 mm) Min. 2 (50 mm) Max. Above Top
Of Condensate Drain Connection In Unit
Vent
3/4 inch
1/2 inch
7
(178)
DrainTrap Assembly with 3/4 inch Piping
Condensate Drain
Connection In Unit
Condensate Drain
Connection In Unit
To
Drain
To
Drain
FIGURE 46
Page 35
TRAP / DRAIN ASSEMBLY USING 1/2” PVC OR 3/4” PVC
Optional Condensate Drain Connection
Adapter 1/2 inch slip X
1/2 inch mpt (Not Furnished)
90° Street Elbow
1/2 inch PVC
(Not Furnished)
1 (25 mm) Min.
2 (50 mm) Max.
Above Top Of
Condensate Drain
Connection In Unit
Condensate Drain
Connection In Unit
90° Street Elbow
1/2 inch PVC
(Furnished)
Adapter 1/2 inch slip X
1/2 inch mpt (Not Furnished) Condensate Drain
Connection In Unit
Vent
5 Feet
Maximum
90° Elbow 1/2 inch PVC
(Not Furnished)
To
Trap
Optional Drain Piping From Trap
1/2 inch PVC Pipe
(Not Furnished)
1/2 inch PVC Pipe
(Not Furnished)
Coupling 1/2 inch slip X slip
(Not Furnished)
Drain Assembly for 1/2 inch Drain Pipe
1/2 inch PVC Pipe
(Not Furnished)
Drain Trap
Assembly
(Furnished)
90° Elbow
1/2 inch PVC
(Not Furnished)
To
Drain
Drain Assembly for 3/4 inch Drain Pipe
Drain Trap
Clean Out
90° Elbow
3/4 inch PVC
(Not Furnished)
To
Drain
90° Elbow
3/4 inch PVC
(Not Furnished)
Drain Trap Assembly with 3/4 inch Piping
To Coupling 3/4 inch slip X slip
Drain
(Not Furnished)
Drain Trap Assembly with 1/2 inch Piping
1 (25 mm) Min. 2 (50 mm) Max. Above Top
Of Condensate Drain Connection In Unit
Drain Trap Assembly
(Furnished)
Vent
1 (25 mm) Min. 2 (50 mm) Max. Above Top
Of Condensate Drain Connection In Unit
Vent
3/4 inch
1/2 inch
7
(178)
Drain Trap Assembly with 3/4 inch Piping
Condensate Drain
Connection In Unit
Condensate Drain
Connection In Unit
To
Drain
To
Drain
FIGURE 47
Page 36
III-START‐UP
A-Preliminary and Seasonal Checks
1 - Inspect electrical wiring, both field and factory installed
for loose connections. Tighten as required.
2 - Check voltage at disconnect switch. Voltage must be
within range listed on the nameplate. If not, consult the
power company and have voltage condition corrected
before starting unit.
3 - Inspect condition of condensate traps and drain as­
sembly. Disassemble and clean seasonally.
B-Heating Start‐Up
BEFORE LIGHTING the unit, smell all around the furnace
area for gas. Be sure to smell next to the floor because
some gas is heavier than air and will settle on the floor.
The gas valve on the ML193DF is equipped with a gas con­
trol switch. Use only your hand to move the switch. Never
use tools. If the the switch will not move by hand, replace
the valve. Do not try to repair it. Force or attempted repair
may result in a fire or explosion.
Placing the furnace into operation:
ML193DF units are equipped with a SureLight ignition sys­
tem. Do not attempt to manually light burners on this fur­
nace. Each time the thermostat calls for heat, the burners
will automatically light The ignitor does not get hot when
there is no call for heat on units with SureLightt ignition
system.
Priming Condensate Trap
The condensate trap should be primed with water prior to
start-up to ensure proper condensate drainage. Either pour
10 fl. oz. (300 ml) of water into the trap, or follow these steps
to prime the trap:
1 - Follow the lighting instructions to place the unit into op­
eration.
2 - Set the thermostat to initiate a heating demand.
3 - Allow the burners to fire for approximately 3 minutes.
4 - Adjust the thermostat to deactivate the heating de­
mand.
5 - Wait for the combustion air inducer to stop. Set the
thermostat to initiate a heating demand and again al­
low the burners to fire for approximately 3 minutes.
6 - Adjust the thermostat to deactivate the heating de­
mand and again wait for the combustion air inducer to
stop. At this point, the trap should be primed with suffi­
cient water to ensure proper condensate drain opera­
tion.
WARNING
If you do not follow these instructions exactly, a fire
or explosion may result causing property damage,
personal injury or death.
Gas Valve Operation (Figure 48)
1 - STOP! Read the safety information at the beginning of
this section.
2 - Set the thermostat to the lowest setting.
3 - Turn off all electrical power to the unit.
4 - This furnace is equipped with an ignition device which
automatically lights the burners. Do not try to light the
burners by hand.
5 - Remove the upper access panel.
6 - Move gas valve switch to OFF. See figure 48.
7 - Wait five minutes to clear out any gas. If you then smell
gas, STOP! Immediately call your gas supplier from a
neighbor's phone. Follow the gas supplier's instruc­
tions. If you do not smell gas go to next step.
8 - Move gas valve switch to ON. See figure 48.
MANIFOLD
PRESSURE
ADJUSTMENT
SCREW
(under
barbed
fitting)
MANIFOLD
PRESSURE
OUTLET
INLET
PRESSURE
PORT
GAS VALVE SHOWN IN ON POSITION
FIGURE 48
9 - Replace the upper access panel.
10- Turn on all electrical power to to the unit.
11- Set the thermostat to desired setting.
NOTE - When unit is initially started, steps 1 through 11
may need to be repeated to purge air from gas line.
12- If the appliance will not operate, follow the instructions
“Turning Off Gas to Unit” and call your service techni­
cian or gas supplier.
Turning Off Gas to Unit
1 - Set the thermostat to the lowest setting.
2 - Turn off all electrical power to the unit if service is to be
performed.
3 - Remove the upper access panel.
4 - Move gas valve switch to OFF.
5 - Replace the upper access panel.
Failure To Operate
If the unit fails to operate, check the following:
1 - Is the thermostat calling for heat?
2 - Are access panels securely in place?
3 - Is the main disconnect switch closed?
4 - Is there a blown fuse or tripped breaker?
5 - Is the filter dirty or plugged? Dirty or plugged filters will
cause the limit control to shut the unit off.
6 - Is gas turned on at the meter?
7 - Is the manual main shut‐off valve open?
8 - Is the internal manual shut‐off valve open?
9 - Is the unit ignition system in lockout? If the unit locks
out again, inspect the unit for blockages.
Page 37
available through Lennox under part number 31B2001.
See Corp. 8411-L10, for further details.
IV-HEATING SYSTEM SERVICE CHECKS
A-C.S.A. Certification
All units are C.S.A. design certified without modifications.
Refer to the ML193DF Operation and Installation Instruc­
tion Manual Information.
WARNING
Do not use matches, candles, flame or any other
source of ignition to check for gas leaks.
B-Gas Piping
CAUTION
D-Testing Gas Supply Pressure
If a flexible gas connector is required or allowed by
the authority that has jurisdiction, black iron pipe
shall be installed at the gas valve and extend outside
the furnace cabinet. The flexible connector can then
be added between the black iron pipe and the gas
supply line.
Gas supply piping should not allow more than 0.5”W.C.
drop in pressure between gas meter and unit. Supply gas
pipe must not be smaller than unit gas connection.
Compounds used on gas piping threaded joints should be
resistant to action of liquefied petroleum gases.
C-Testing Gas Piping
IMPORTANT
In case emergency shutdown is required, turn off
the main shut‐off valve and disconnect the main
power to unit. These controls should be properly
labeled by the installer.
When pressure testing gas lines, the gas valve must be dis­
connected and isolated. Gas valves can be damaged if
subjected to more than 0.5psig (14” W.C.). See figure 49.
MANUAL MAIN SHUT-OFF
VALVE WILL NOT HOLD
NORMAL TEST PRESSURE
1/8” N.P.T. PLUGGED TAP
FURNACE
ISOLATE
GAS VALVE
CAP
FIGURE 49
When checking piping connections for gas leaks, use pre­
ferred means. Kitchen detergents can cause harmful cor­
rosion on various metals used in gas piping. Use of a spe­
cialty Gas Leak Detector is strongly recommended. It is
When testing supply gas pressure, use the 1/8” N.P.T.
plugged tap or pressure post located on the gas valve to
facilitate test gauge connection. See figure 48. Check gas
line pressure with unit firing at maximum rate. Low pres­
sure may result in erratic operation or underfire. High pres­
sure can result in permanent damage to gas valve or over­
fire.
On multiple unit installations, each unit should be checked
separately, with and without units operating. Supply pres­
sure must fall within range listed in table 19.
E-Check Manifold Pressure
After line pressure has been checked and adjusted, check
manifold pressure. Move pressure gauge to outlet pres­
sure tap located on unit gas valve (GV1).
Checks of manifold pressure are made as verification of
proper regulator adjustment.
IMPORTANT
For safety, connect a shut‐off valve between the
manometer and the gas tap to permit shut off of
gas pressure to the manometer.
1 - Remove the threaded plug from the outlet side of the
gas valve and install a field-provided barbed fitting.
Connect to a manometer to measure manifold pres­
sure.
2 - Start unit and allow 5 minutes for unit to reach steady
state.
3 - While waiting for the unit to stabilize, observe the
flame. Flame should be stable and should not lift from
burner. Natural gas should burn blue.
4 - After allowing unit to stabilize for 5 minutes, record
manifold pressure and compare to value given in table
19.
NOTE - Shut unit off and remove manometer as soon as an
accurate reading has been obtained. Take care to remove
barbed fitting and replace threaded plug.
Page 38
F- Proper Gas Flow (Approximate)
G- Proper Combustion
Gas Flow (Approximate)
Furnace should operate at least 15 minutes with correct
manifold pressure and gas flow rate before checking com­
bustions. Take sample beyond the flue outlet and compare
to table 20.
TABLE 18
GAS METER CLOCKING CHART
Seconds for One Revolution
Natural
LP
ML193
Unit
1 cu ft
2 cu ft
1 cu ft
2 cu ft
Dial
Dial
Dial
DIAL
-045
80
160
200
400
-070
55
110
136
272
-090
41
82
102
204
-110
33
66
82
164
Natural-1000 btu/cu ft
TABLE 20
ML193
Unit
-045
-070
-090
-110
LP-2500 btu/cu ft
Pressure in.wg.
Nat. Gas
All sizes
L.P. Gas
All sizes
8.6 - 9.3
NOTE - In Canada, certification for installations at eleva­
tions over 4500 feet (1372 m) is the jurisdiction of local au­
thorities.
ML193DF-1 through -6 units require no manifold pressure
adjustments for operation at altitudes up to 10,000 feet
(3048 m) above sea level. However, -7 units and later in­
stalled at altitude of 4501 - 10,000 feet (1373 to 3048m) re­
quire a pressure switch change which can be ordered sep­
arately and manifold de-rate. See table 19 or table 21 for
manifold pressures at varying altitudes. Table 22 lists con­
version kit and pressure switch requirements at varying al­
titudes.
The combustion air pressure switch is factory-set and re­
quires no adjustment.
Supply
Pressure in.wg.
Manifold
7.2 - 7.9
H- High Altitude
TABLE 19
Manifold and Supply Pressure (Outlet) inches w.c.
At All Altitudes For -1 Through -6 Units
Model
Input Sizes
CO2% For L.P.
The carbon monoxide reading should not exceed 50 ppm.
NOTE - To obtain accurate reading, shut off all other gas
appliances connected to meter.
Furnace should operate at least 5 minutes before checking
gas flow. Determine time in seconds for two revolutions of
gas through the meter. (Two revolutions assures a more
accurate time). Divide by two and compare to time in table
18. If manifold pressure matches table 19 and rate is incor­
rect, check gas orifices for proper size and restriction. Re­
move temporary gas meter if installed.
Fuel
CO2% For Nat
Min.
Max.
3.5
4.5
13.0
10.0
11.0
13.0
TABLE 21
Manifold and Supply Line Pressure 0-10,000ft. For -7 Units and Later
Manifold Pressure in. wg.
ML193
Unit
All Sizes
Gas
Supply Line
Pressure
in. w.g.
0 - 10000 ft.
0-4500 ft.
4501-5500 ft.
5501-6500 ft.
6501 7500ft.
7501 - 10000ft.
Natural
3.5
3.3
3.2
3.1
3.5
4.5
13.0
LP/propane
10.0
9.4
9.1
8.9
10.0
11.0
13.0
NOTE - A natural to L.P. propane gas changeover kit is necessary to convert this unit. Refer to the changeover kit installation instruction for the conversion
procedure.
TABLE 22
Conversion Kit and Pressure Switch Requirements at Varying Altitudes
ML193
Unit
-045
-070
-090
-110
Natural to
LP/Propane
High Altitude
Natural Burner Ori­
fice Kit
LP/Propane to
Natural
0 - 7500 ft
(0 - 2286m)
7501 - 10,000 ft
(2286 - 3038m)
0 - 7500 ft
(0 - 2286m)
4501 - 7500 ft
(1373 - 2286m)
7501 -10,000 ft
(2286 - 3048m)
*69W73
73W37
*73W81
93W87
93W88
High Altitude Pressure Switch
* Conversion requires installation of a gas valve manifold spring which is provided with the gas conversion kit.
Pressure switch is factory set. No adjustment necessary. All models use the factory-installed pressure switch from 0-4500 feet (0-1370 m).
Page 39
I-Flame Signal
V-TYPICAL OPERATING CHARACTERISTICS
A transducer (Part #78H5401 available from Lennox Re­
pair Parts) is required to measure flame signal if meter
used will not read a low micro amp signal. Seefigure50.
The transducer converts microamps to volts on a 1:1 con­
version. Flame signal is shown in table 23. A digital readout
meter must be used. The transducer plugs into most me­
ters.
A-Blower Operation and Adjustment
1 - Blower operation is dependent on thermostat control
system.
2 - Generally, blower operation is set at thermostat sub­
base fan switch. With fan switch in ON position, blower
operates continuously. With fan switch in AUTO posi­
tion, blower cycles with demand or runs continuously
while heating or cooling circuit cycles.
3 - Depending on the type of indoor thermostat, blower
and entire unit will be off when the system switch is in
OFF position.
B-Temperature Rise
Temperature rise depends on unit input, blower speed,
blower horsepower and static pressure as marked on the
unit rating plate. The blower speed must be set for unit op­
eration within the range of “TEMP. RISE °F” listed on the
unit rating plate.
To Measure Temperature Rise:
TABLE 23
Normal Flame Signal
1.50 Microamps
Low Flame Signal
1.40 Microamps
Drop Out Signal
= 0.50 Microamps
To Measure Flame Signal:
1 - Set the volt meter to the DC voltage scale. Insert trans­
ducer into the VDC and common inputs. Observe cor­
rect polarities. Failure to do so results in negative (-)
values.
2 - Turn off supply voltage to control.
3 - Disconnect ignition control flame sensor wire from the
flame sensor.
4 - Connect (-) lead of the transducer to flame sensor.
5 - Connect (+) lead of transducer to the ignition control
sensor wire.
6 - Turn supply voltage on and close thermostat contacts
to cycle system.
7 - When main burners are in operation for two minutes,
take reading. Remember 1 DC volt = 1 DC microamp.
NOTE-MUST USE DIGITAL METER
SET DIAL TO
MEASURE VDC
(+)
(+) TO
IGNITION
CONTROL
SENSOR
WIRE
(-)
(-) TO
FLAME
SENSOR
FIGURE 50
TRANSDUCER
PART #78H5401
RED COLLAR
INDICATES
POSITIVE
LEAD
1 - Place plenum thermometers in the supply and return
air plenums. Locate supply air thermometer in the first
horizontal run of the plenum where it will not pick up ra­
diant heat from the heat exchanger.
2 - Set thermostat for heat call. Unit must operate on sec­
ond-stage heat.
3 - After plenum thermometers have reached their high­
est and steadiest readings, subtract the two readings.
The difference should be in the range listed on the unit
rating plate. If the temperature is too low, decrease
blower speed. If temperature is too high, first check the
firing rate. Provided the firing rate is acceptable, in­
crease blower speed to reduce temperature.
C-External Static Pressure
1 - Tap locations shown in figure 51.
STATIC PRESSURE
2 - Punch a 1/4” diameter hole TEST
in supply and return air ple­
nums. Insert manometer filter
hose flush with inside edge
of hole or insulation. Seal coil
around the hose with perma­
gum. Connect the zero end
of the manometer to the dis­
FIGURE 50
charge (supply) side of the system. On ducted sys­
tems, connect the other end of manometer to the return
duct as above.
3 - With only the blower motor running and the evaporator
coil dry, observe the manometer reading. Adjust blow­
er motor speed to deliver the air desired according to
the job requirements.
4 - External static pressure drop must not be more than
0.8” W.C. in the heating mode and must not exceed
1.0” W.C in the cooling mode.
5 - Seal the hole when the check is complete.
To change existing heat tap, turn off power then switch out
speed tap with tap connected to ”PARK” . See unit diagram
for blower motor tap colors for each speed.
Page 40
TABLE 24
VI-MAINTENANCE
WARNING
Furnace
Cabinet Width
Filter Size
17-1/2”
16 x 25 x 1 (1)
21”
ELECTRICAL SHOCK, FIRE,
OR EXPLOSION HAZARD.
Failure to follow safety warnings exactly could result
in dangerous operation, serious injury, death or
property damage.
Improper servicing could result in dangerous opera­
tion, serious injury, death, or property damage.
Before servicing, disconnect all electrical power to
furnace.
When servicing controls, label all wires prior to dis­
connecting. Take care to reconnect wires correctly.
Verify proper operation after servicing.
At the beginning of each heating season, system should be
checked as follows by a qualified service technician:
Blower
Check the blower wheel for debris and clean if necessary.
The blower motors are prelubricated for extended bearing
life. No further lubrication is needed.
WARNING
The blower access panel must be securely in place
when the blower and burners are operating. Gas
fumes, which could contain carbon monoxide, can
be drawn into living space resulting in personal inju­
ry or death.
Exhaust and air intake pipes
Check the exhaust and air intake pipes and all connections
for tightness and to make sure there is no blockage.
NOTE - After any heavy snow, ice or frozen fog event the
furnace vent pipes may become restricted. Always check
the vent system and remove any snow or ice that may be
obstructing the plastic intake or exhaust pipes.
Electrical
1 - Check all wiring for loose connections.
2 - Check for the correct voltage at the furnace (furnace
operating). Correct voltage is 120VAC + 10%
3 - Check amp-draw on the blower motor with blower ac­
cess panel in place.
Motor Nameplate__________Actual__________
Winterizing and Condensate Trap Care
1 - Turn off power to the furnace.
2 - Have a shallow pan ready to empty condensate water.
3 - Remove the clean out cap from the condensate trap
and empty water. Inspect the trap then reinstall the
clean out cap.
Condensate Hose Screen (Figure 52)
Check the condensate hose screen for blockage and clean
if necessary.
1 - Turn off power to the unit.
2 - Remove hose from cold end header box. Twist and pull
screen to remove.
3 - Inspect screen and rinse with tap water if needed.
4 - Reinstall screen and turn on power to unit.
Filters
Condensate Hose Screen
All air filters are installed external to the unit. Filters should
be inspected monthly. Clean or replace the filters when
necessary to ensure proper furnace operation. Table 24
lists recommended filter sizes.
IMPORTANT
If a high­efficiency filter is being installed as part of
this system to ensure better indoor air quality, the fil­
ter must be properly sized. High­efficiency filters
have a higher static pressure drop than standard­ef­
ficiency glass/foam filters. If the pressure drop is too
great, system capacity and performance may be re­
duced. The pressure drop may also cause the limit to
trip more frequently during the winter and the indoor
coil to freeze in the summer, resulting in an increase
in the number of service calls.
Before using any filter with this system, check the
specifications provided by the filter manufacturer
against the data given in the appropriate Lennox
Product Specifications bulletin. Additional informa­
tion is provided in Service and Application Note
ACC­00­2 (August 2000).
Hose
FIGURE 52
Cleaning Heat Exchanger
If cleaning the heat exchanger becomes necessary, follow
the below procedures and refer to figure 1 when disassem­
bling unit. Use papers or protective covering in front of fur­
nace while removing heat exchanger assembly.
1 - Turn off electrical and gas supplies to the furnace.
2 - Remove the furnace access panels.
3 - Disconnect the 2 wires from the gas valve.
4 - Remove gas supply line connected to gas valve. Re­
move gas valve/manifold assembly.
5 - Remove sensor wire from sensor. Disconnect 2‐pin
plug from the ignitor.
Page 41
6 - Disconnect wires from flame roll-out switches.
7 - Loosen clamps at vent elbow. Disconnect condensate
drain tubing from flue collar. and remove the vent el­
bow.
8 - Remove four burner box screws at the vestibule panel
and remove burner box. Set burner box assembly
aside.
NOTE - If necessary, clean burners at this time. Follow
procedures outlined in Burner Cleaning section.
9 - Mark and disconnect all combustion air pressure tub­
ing from cold end header collector box.
10 - Mark and remove wires from pressure switches. Re­
move pressure switches. Keep tubing attached to
pressure switches.
11 - Disconnect the plug from the combustion air inducer.
Remove two screws which secure combustion air in­
ducer to collector box. Remove combustion air induc­
er assembly. Remove ground wire from vest panel.
12 - Remove electrical junction box from the side of the fur­
nace.
13 - Mark and disconnect any remaining wiring to heating
compartment components. Disengage strain relief
bushing and pull wiring and bushing through the hole
in the blower deck.
14 - Remove the primary limit from the vestibule panel.
15 - Remove two screws from the front cabinet flange at
the blower deck. Spread cabinet sides slightly to allow
clearance for removal of heat exchanger.
16 - Remove screws along vestibule sides and bottom
which secure vestibule panel and heat exchanger as­
sembly to cabinet. Remove two screws from blower
rail which secure bottom heat exchanger flange. Re­
move heat exchanger from furnace cabinet.
17 - Back wash heat exchanger with soapy water solution
or steam. If steam is used it must be below 275°F
(135°C) .
18 - Thoroughly rinse and drain the heat exchanger. Soap
solutions can be corrosive. Take care to rinse entire
assembly.
19 - Reinstall heat exchanger into cabinet making sure that
the clamshells of the heat exchanger assembly are
resting on the support located at the rear of the cabi­
net. Remove the indoor blower to view this area
through the blower opening.
20 - Re‐secure the supporting screws along the vestibule
sides and bottom to the cabinet. Reinstall blower and
mounting screws.
21 - Reinstall cabinet screws on front flange at blower
deck.
22 - Reinstall the primary limit on the vestibule panel.
23 - Route heating component wiring through hole in blow­
er deck and reinsert strain relief bushing.
24 - Reinstall electrical junction box.
25 - Reinstall the combustion air inducer. Reconnect the
combustion air inducer to the wire harness.
26 - Reinstall pressure switches and reconnect pressure
switch wiring.
27 - Carefully connect combustion air pressure switch hos­
ing from pressure switches to proper stubs on cold end
header collector box.
28 - Reinstall condensate trap.
29 - Reconnect exhaust piping and exhaust drain tubing.
30 - Reinstall burner box assembly in vestibule area.
31 - Reconnect flame roll-out switch wires.
32 - Reconnect sensor wire and reconnect 2-pin plug from
ignitor.
33 - Secure burner box assembly to vestibule panel using
four existing screws. Make sure burners line up in
center of burner ports.
34 - Reinstall gas valve manifold assembly. Reconnect
gas supply line to gas valve.
35 - Reconnect 2 wires to gas valve.
36 - Replace the blower compartment access panel.
37 - Refer to instruction on verifying gas and electrical con­
nections when re-establishing supplies.
38 - Follow lighting instructions to light and operate fur­
nace for 5 minutes to ensure that heat exchanger is
clean and dry and that furnace is operating properly.
39 - Replace heating compartment access panel.
Cleaning the Burner Assembly
1 - Turn off electrical and gas power supplies to furnace.
Remove upper and lower furnace access panels.
2 - Disconnect the 2-pin plug from the gas valve.
3 - Remove the burner box cover.
4 - Disconnect the gas supply line from the gas valve. Re­
move gas valve/manifold assembly.
5 - Mark and disconnect sensor wire from the sensor. Dis­
connect 2‐pin plug from the ignitor at the burner box.
6 - Remove four screws which secure burner box assem­
bly to vest panel. Remove burner box from the unit.
7 - Use the soft brush attachment on a vacuum cleaner to
gently clean the face of the burners. Visually inspect
the inside of the burners and crossovers for any block­
age caused by foreign matter. Remove any blockage.
8 - Reconnect the sensor wire and reconnect the 2-pin
plug to the ignitor wiring harness.
9 - Reinstall the burner box assembly using the existing
four screws. Make sure that the burners line up in the
center of the burner ports.
10 - Reinstall the gas valve manifold assembly. Reconnect
the gas supply line to the gas valve. Reinstall the burn­
er box cover.
11 - Reconnect 2-pin plug to gas valve.
12 - Replace the blower compartment access panel.
13 - Refer to instruction on verifying gas and electrical con­
nections when re-establishing supplies.
14 - Follow lighting instructions to light and operate fur­
nace for 5 minutes to ensure that heat exchanger is
clean and dry and that furnace is operating properly.
15 - Replace heating compartment access panel.
Page 42
VII-WIRING DIAGRAM AND SEQUENCE OF OPERATION
ML193DF With Integrated Control 100973
1 - When there is a call for heat, W1 of the thermostat en­
ergizes W of the furnace control with 24VAC.
2 - S10 primary limit switch and S47 rollout switch are
closed. Call for heat can continue.
3 - The integrated contol (A92) energizes combustion air
inducer B6. Combustion air inducer runs until S18
combustion air prove switch closes (switch must close
within 2-1/2 minutes or control goes into 5 minute
Watchguard Pressure Switch delay). Once S18
closes, a 15-second pre-purge follows.
4 - The integrated control (A92) energizes ignitor. A
20-second warm-up period begins.
5 - Gas valve opens for a 4-second trial for ignition
6 - Flame is sensed, gas valve remains open for the heat
call.
7 - After 30-second delay, the integrated control (A92)
energizes indoor blower B3.
8 - When heat demand is satisfied, W1 of the indoor ther­
mostat de-energizes W of the integrated control which
de-energizes the gas valve. Combustion air inducer
B6 continues a 5-second post-purge period, and in­
door blower B3 completes a selected OFF time delay.
Page 43
Sequence of Operation Flow Chart - Integrated Control 100973
HEATING SEQUENCE OF OPERATION
ABNORMAL HEATING MODE
NORMAL HEATING MODE
POWER ON
GAS VALVE OFF. COMBUSTION AIR INDUCER OFF.
INDOOR BLOWER DELAY OFF.
LED #1 ON
LED #2 ON
(RESET CONTROL BY TURNING MAIN POWER OFF.)
NO
CONTROL SELF-CHECK OKAY?
YES
NO
POLARITY REVERSED.
LED #1 -- FAST FLASH
LED #2 -- SLOW FLASH
NO
IMPROPER GROUND.
LED #1 -- ALTERNATING FAST FLASH
LED #2 -- ALTERNATING FAST FLASH
IS POLARITY CORRECT?
YES
IS THERE A PROPER GROUND?
YES
NO
LEDs SIGNAL FAST ALTERNATING FLASH.
CONTROL WILL NOT RESPOND TO A CALL FOR
HEATING UNTIL VOLTAGE RISES ABOVE 95 VOLTS.
IS VOLTAGE
ABOVE 90 VOLTS?
YES
ROLLOUT SWITCH CLOSED?
GAS VALVE OFF. COMBUSTION AIR INDUCER ON.
INDOOR BLOWER ON.
LED #1 -- ON. LED #2 -- SLOW FLASH.
SEQUENCE HOLDS UNTIL ROLLOUT SWITCH CLOSES
AND POWER IS RESET OR T'STAT IS INTERRUPTED
FOR MINIMUM OF 1 SECOND.
NO
YES
BURNER OFF?
GAS VALVE OFF. COMBUSTION AIR INDUCER ON.
INDOOR BLOWER ON HEATING SPEED.
LED #1 -- SLOW FLASH
LED #2 -- OFF
NO
(Flame sensed without gas valve energized)
YES
NO
NORMAL OPERATION:
LED #1 -- SLOW FLASH
LED #2 -- SLOW FLASH
YES
THERMOSTAT CALLS FOR HEAT:
LED #1 -- FAST FLASH
LED #2 -- FAST FLASH
NO
YES
COMBUSTION AIR INDUCER OFF.
INDOOR BLOWER ON
LED #1 SLOW FLASH RATE
LED #2 -- ON
PRIMARY LIMIT SWITCH. CLOSED?
YES
NO
IS COMBUSTION AIR
PRESSURE SWITCH OPEN?
YES
GAS VALVE OFF.
COMBUSTION AIR INDUCER OFF.
INDOOR BLOWER OFF WITH DELAY.
LED #1 OFF
LED #2 SLOW FLASH
(Sequence holds until pressure switch
opens or thermostat resets control.)
IS COMBUSTION AIR INDUCER
ENERGIZED?
YES
HAS COMBUSTION AIR PRESSURE
SWITCH CLOSED IN 2.5 MINUTES?
NO
YES
CONTINUED NEXT
PAGE
Page 44
PRESSURE SWITCH IS IN WATCHGUARD MODE.
GAS VALVE OFF. COMBUSTION AIR INDUCER OFF.
INDOOR BLOWER OFF WITH DELAY.
LED #1 -- OFF. LED #2 -- SLOW FLASH.
IS 5‐MINUTE RESET PERIOD COMPLETE?
YES
HEATING SEQUENCE CONTINUED
NORMAL HEATING MODE
ABNORMAL HEATING MODE
15‐SECOND COMBUSTION AIR INDUCER PREPURGE
INITIATED BY CLOSED PRESSURE SWITCH.
YES
NO
IS VOLTAGE ABOVE 90 VOLTS?
IGNITOR WARM‐UP -- 20 SECONDS.
YES
NO
YES
4‐SECOND TRIAL FOR IGNITION.
GAS VALVE OPENS. IGNITOR ENERGIZED FOR
FIRST 3 SECONDS OF THE TRIAL.
YES
FLAME STABILIZATION PERIOD.
4 SECONDS
LEDS SIGNAL
ALTERNATING
FAST FLASH UNTIL
VOLTAGE IS ABOVE
95 VOLTS, THEN
RESTARTS HEATING
SEQUENCE.
GAS VALVE OFF. COMBUSTION AIR INDUCER ON.
INDOOR BLOWER OFF.
NO HAS CONTROL FAILED TO SENSE FLAME FOR
FIVE CONSECUTIVE TRIES DURING A SINGLE
HEAT DEMAND?
FLAME RECTIFICATION CURRENT
CHECK. CAN FLAME BE PROVEN WITHIN
4 SECONDS AFTER GAS VALVE OPENS?
(0.5 microamps)
NO
YES
WATCHGUARD MODE. GAS VALVE OFF.
COMBUSTION AIR INDUCER OFF.
INDOOR BLOWER OFF WITH DELAY
LEDs SIGNAL WATCHGUARD FAILURE CODE.
IS 60‐MINUTE RESET PERIOD COMPLETE?
YES
YES
NO
NO
HAS CONTROL RESET IGNITION
SEQUENCE FOUR TIMES?
FLAME PRESENT?
YES
YES
LIMIT SWITCH WATCHGUARD
MODE. GAS VALVE, COMB. AIR
INDUCER AND INDOOR BLOW­
ER OFF. LEDs SIGNAL LIMIT
SWITCH OPEN UNTIL MAIN
POWER IS
INTERRUPTED OR
GAS VALVE DE-ENERGIZED.
T'STAT IS CYCLED
COMBUSTION AIR INDUCER DE-ENERGIZED.
OFF/ON FOR 1 SEC.
NO INDOOR BLOWER ON UNTIL SWITCH CLOSES.
MINIMUM. 60-MIN­
LED #1 -- SLOW FLASH. LED #2 -- ON.
UTE WATCHGUARD
IS LIMIT SWITCH CLOSED?
PERIOD STARTS AT
YES
TIME LIMIT CLOSES.
IS 60-MIN. PERIOD
YES
HAS PRIMARY / SECONDARY
COMPLETE?
LIMIT RESET TIME
NO
FLAME SIGNAL 1.5 MICROAMPS OR GREATER?
YES
INDOOR BLOWER ON
AFTER 30-SECOND DELAY
YES
PRIMARY AND SECONDARY LIMIT
SWITCHES CLOSED?
YES
LOW FLAME SIGNAL
(Does not affect operation of control)
LED #1 -- SLOW FLASH
LED #2 -- FAST FLASH
EXCEEDED 3 MINUTES?
NO
NO
ROLLOUT SWITCH CLOSED?
YES
COMBUSTION AIR PRESSURE
SWITCH CLOSED?
YES
THERMOSTAT DEMAND SATISFIED.
YES
LED #1 & #2 SIMULTANEOUS SLOW FLASHES.
YES
COMB. AIR INDUCER CONTINUES 5‐SECOND
POST PURGE AFTER T'STAT DEMAND IS SATISFIED.
INDOOR AIR BLOWER COMPLETES SELECTED “OFF”
DELAY BEFORE SHUTTING OFF.
NO
GAS VALVE POWER OFF.
COMBUSTION AIR INDUCER POWER ON.
INDOOR BLOWER ON
LED #1 -- ON. LED #2 -- SLOW FLASH.
SEQUENCE HOLDS UNTIL ROLLOUT SWITCH IS RESET
AND MAIN POWER IS INTERRUPTED OR
THERMOSTAT IS CYCLED OFF/ON FOR 1 SEC. MINIMUM.
HAS PRESSURE SWITCH OPENED 5
1 HR
TIMES IN THE SAME HEAT DEMAND?
PRESSURE
SWITCH
YES
NO
WATCHGUARD
GAS VALVE DE-ENERGIZED.
MODE
COMBUSTION AIR INDUCER ON.
INDOOR BLOWER OFF WITH DELAY
LED #1 -- OFF. LED #2 -- SLOW FLASH.
HAS CAB SWITCH CLOSED IN 2.5 MINUTES?
NO
5‐MINUTE PRESSURE SWITCH
WATCHGUARD MODE.
Page 45
COOLING SEQUENCE OF OPERATION
NORMAL COOLING MODE
ABNORMAL COOLING MODE
POWER ON
IGNITION CONTROL MAIN POWER ON.
NO
CONTROL SELF DIAGNOSTIC CHECK.
IS CONTROL OPERATING NORMALLY?
GAS VALVE OFF. COMBUSTION AIR INDUCER OFF.
INDOOR BLOWER OFF WITH NORMAL DELAY.
SIGNAL CIRCUIT CONTROL FAILURE AT LED.
INTERRUPT MAIN POWER TO RESET CONTROL.
YES
NO
IS THERE A PROPER GROUND?
YES
NO
IS POLARITY CORRECT?
YES
SIGNAL IMPROPER GROUND AT LED.
CONTROL WILL CONTINUE TO CALL FOR COOLING
IN THIS CONDITION.
SIGNAL POLARITY REVERSED AT LED. CONTROL
WILL CONTINUE TO CALL FOR COOLING IN THIS
CONDITION.
NO
LED SIGNALS LOW VOLTAGE. CONTROL WILL
CONTINUE TO CALL FOR COOLING
IN THIS CONDITION.
IS VOLTAGE
ABOVE 90 VOLTS?
YES
NO
ROLLOUT SWITCH MONITORED CONTINUOUSLY.
IS ROLLOUT SWITCH CLOSED?
YES
LED: SLOW FLASH RATE REMAINS UNCHANGED
THROUGHOUT COOLING CYCLE.
THERMOSTAT CALLS FOR COOLING.
COMPRESSOR CONTACTOR AND SYSTEM FAN
ENERGIZED WITH 2‐SECOND DELAY
(COOLING SPEED). EAC TERM. ENERGIZED.
THERMOSTAT OPENS.
COMPRESSOR OFF.
SYSTEM FAN AND EAC TERM. OFF
WITH 45‐SECOND DELAY.
Page 46
GAS VALVE OFF. COMBUSTION AIR INDUCER ON.
INDOOR BLOWER ON.
SIGNAL ROLL‐OUT SWITCH OPEN AT LED.
SEQUENCE HOLDS UNTIL ROLLOUT SWITCH CLOSES
AND MAIN POWER IS INTERRUPTED OR THERMOSTAT
IS CYCLED OFF/ON FOR 1 SEC. MINIMUM.
CONTINUOUS HEAT SPEED FAN SEQUENCE OF OPERATION
LED: SLOW FLASH RATE REMAINS
UNCHANGED THROUGHOUT SEQUENCE.
MANUAL FAN SELECTION MADE AT THERMOSTAT.
CONTROL (G) ENERGIZES SYSTEM FAN AT HEAT
SPEED. EAC TERMINAL IS ENERGIZED.
THERMOSTAT CALLS FOR HEAT (W).
YES
NO
THERMOSTAT CALLS FOR COOLING.
YES
SYSTEM FAN SWITCHED TO COOL SPEED.
EAC TERM. REMAINS ON.
NO
HUM TERM. ENERGIZES
WITH COMB. AIR INDUCER.
SYSTEM FAN REMAINS ON
HEATING SPEED.
THERMOSTAT OPENS.
HUM TERM. DE-ENERGIZES
WITH COMB. AIR INDUCER
THERMOSTAT OPENS.
MANUAL FAN SELECTION MADE AT THERMOSTAT.
CONTROL (G) ENERGIZES SYSTEM FAN AT HEAT
SPEED. EAC TERM. ENERGIZED.
Page 47
SYSTEM FAN REMAINS ON
HEATING SPEED.
ML193DF With Integrated Control 103085
1 - When there is a call for heat, W1 of the thermostat en­
ergizes W of the furnace control with 24VAC.
2 - S10 primary limit switch and S47 rollout switch are
closed. Call for heat can continue.
3 - The integrated control (A92) energizes combustion air
inducer B6. Combustion air inducer runs until S18
combustion air prove switch closes (switch must close
within 2-1/2 minutes or control goes into 5 minute
Watchguard Pressure Switch delay). Once S18
closes, a 15-second pre-purge follows.
4 - The integrated control (A92) energizes ignitor. A
20-second warm-up period begins.
5 - Gas valve opens for a 4-second trial for ignition
6 - Flame is sensed, gas valve remains open for the heat
call.
7 - After 30-second delay, the integrated control (A92)
energizes indoor blower B3.
8 - When heat demand is satisfied, W1 of the indoor ther­
mostat de-energizes W of the integrated control which
de-energizes the gas valve. Combustion air inducer
B6 continues a 5-second post-purge period, and in­
door blower B3 completes a selected OFF time delay.
Page 48
Sequence of Operation Flow Chart - Integrated Control 103085
HEATING SEQUENCE OF OPERATION
ABNORMAL HEATING MODE
NORMAL HEATING MODE
POWER ON
GAS VALVE OFF. COMBUSTION AIR INDUCER OFF.
INDOOR BLOWER DELAY OFF.
LED: OFF
NO
CONTROL SELF-CHECK OKAY?
YES
NO
POLARITY REVERSED.
LED: 9 FLASHES
IS POLARITY CORRECT?
YES
IMPROPER GROUND.
LED: OFF
CONTROL WILL NOT RESPOND TO CALL FOR HEAT
UNTIL PROPER GROUND.
NO
IS THERE A PROPER GROUND?
YES
NO
LED: ON STEADY
IGNITOR WILL GLOW DIMLY BUT WILL NOT LIGHT
IS VOLTAGE
ABOVE 90 VOLTS?
YES
ROLLOUT SWITCH CLOSED?
GAS VALVE OFF. COMBUSTION AIR INDUCER ON.
INDOOR BLOWER ON.
LED: 5 FLASHES
SEQUENCE HOLDS UNTIL ROLLOUT SWITCH CLOSES
AND POWER IS RESET OR T'STAT IS INTERRUPTED
FOR MINIMUM OF 1 SECOND.
NO
YES
BURNER OFF?
GAS VALVE OFF. COMBUSTION AIR INDUCER ON.
INDOOR BLOWER ON HEATING SPEED.
LED: 1 FLASH
NO
(Contiuous Flame Check)
YES
NO
NORMAL OPERATION:
LED: STEADY ON
YES
COMBUSTION AIR INDUCER OFF.
INDOOR BLOWER ON
LED: 4 FLASHES
THERMOSTAT CALLS FOR
HEAT:
LED: STEADY ON
YES
NO
PRIMARY AND SECONDARY LIMIT SWITCH.
CLOSED?
YES
NO
IS COMBUSTION AIR
PRESSURE SWITCH OPEN?
YES
IS COMBUSTION AIR INDUCER
ENERGIZED?
YES
HAS COMBUSTION AIR PRESSURE
SWITCH CLOSED IN 2.5 MINUTES?
NO
YES
CONTINUED NEXT
PAGE
Page 49
GAS VALVE OFF.
COMBUSTION AIR INDUCER OFF.
INDOOR BLOWER OFF WITH
DELAY.
LED: 2 FLASHES
(Sequence holds until pressure switch
opens or thermostat resets control.)
PRESSURE SWITCH IS IN WATCHGUARD MODE.
GAS VALVE OFF. COMBUSTION AIR INDUCER OFF.
INDOOR BLOWER OFF WITH DELAY.
LED: 3 FLASHES
IS 5‐MINUTE RESET PERIOD COMPLETE?
YES
HEATING SEQUENCE CONTINUED
NORMAL HEATING MODE
ABNORMAL HEATING MODE
15‐SECOND COMBUSTION AIR INDUCER PREPURGE
INITIATED BY CLOSED PRESSURE SWITCH.
YES
NO
IS VOLTAGE ABOVE 90 VOLTS?
IGNITOR WARM‐UP -- 20 SECONDS.
YES
NO
YES
4‐SECOND TRIAL FOR IGNITION.
GAS VALVE OPENS.
LED: ON STEADY
UNTIL VOLTAGE IS
ABOVE 95 VOLTS,
THEN RESTARTS
HEATING
SEQUENCE.
GAS VALVE OFF. COMBUSTION AIR INDUCER ON.
INDOOR BLOWER OFF.
NO HAS CONTROL FAILED TO SENSE FLAME FOR
FIVE CONSECUTIVE TRIES DURING A SINGLE
HEAT DEMAND?
YES
FLAME STABILIZATION PERIOD.
4 SECONDS
FLAME RECTIFICATION CURRENT
CHECK. CAN FLAME BE PROVEN WITHIN
4 SECONDS AFTER GAS VALVE OPENS?
NO
YES
WATCHGUARD MODE. GAS VALVE OFF.
COMBUSTION AIR INDUCER OFF.
INDOOR BLOWER OFF WITH DELAY
LED: 7 FLASHES WATCHGUARD FAILURE CODE.
IS 60‐MINUTE RESET PERIOD COMPLETE?
YES
YES
NO
NO
HAS CONTROL RESET IGNITION
SEQUENCE FOUR TIMES?
FLAME PRESENT?
YES
NO
FLAME SIGNAL 1.5 MICROAMPS OR GREATER?
YES
INDOOR BLOWER ON
AFTER 30-SECOND DELAY
GAS VALVE DE-ENERGIZED.
COMBUSTION AIR INDUCER DE-ENERGIZED.
INDOOR BLOWER ON UNTIL SWITCH CLOSES.
LED: 4 FLASHES
IS LIMIT SWITCH CLOSED?
YES
PRIMARY AND SECONDARY LIMIT
SWITCHES CLOSED?
LOW FLAME SIGNAL
(Does not affect operation of control)
LED: ON STEADY
NO
YES
NO
YES
5 MINUTE WATCHGUARD MODE.
HAS LIMIT SWITCHED CLOSED
AFTER 5 MINUTES?
NO
NO
ROLLOUT SWITCH CLOSED?
YES
COMBUSTION AIR PRESSURE
SWITCH CLOSED?
YES
THERMOSTAT DEMAND SATISFIED.
YES
LED: ON STEADY
YES
COMB. AIR INDUCER CONTINUES 15‐SECOND
POST PURGE AFTER T'STAT DEMAND IS SATISFIED.
INDOOR AIR BLOWER COMPLETES SELECTED “OFF”
DELAY BEFORE SHUTTING OFF.
NO
YES
GAS VALVE POWER OFF.
COMBUSTION AIR INDUCER POWER ON AFTER 15
SECOND DELAY. INDOOR BLOWER ON
LED: 5 FLASHES
SEQUENCE HOLDS UNTIL ROLLOUT SWITCH IS RESET
AND MAIN POWER IS INTERRUPTED OR
THERMOSTAT IS CYCLED OFF/ON FOR 1 SEC. MINIMUM.
HAS PRESSURE SWITCH OPENED 5
TIMES IN THE SAME HEAT DEMAND?
NO
GAS VALVE DE-ENERGIZED.
COMBUSTION AIR INDUCER ON.
INDOOR BLOWER OFF WITH DELAY
LED: 6 FLASHES 5 MINUTE PRESSURE
SWITCH WATCHGUARD MODE.
Page 50
1 HR
PRESSURE
SWITCH
YES
WATCHGUARD
MODE
COOLING SEQUENCE OF OPERATION
NORMAL COOLING MODE
ABNORMAL COOLING MODE
POWER ON
IGNITION CONTROL MAIN POWER ON. LED: ON STEADY
NO
CONTROL SELF DIAGNOSTIC CHECK.
IS CONTROL OPERATING NORMALLY?
GAS VALVE OFF. COMBUSTION AIR INDUCER OFF.
INDOOR BLOWER OFF WITH NORMAL DELAY.
LED: OFF
INTERRUPT MAIN POWER TO RESET CONTROL.
YES
NO
IS THERE A PROPER GROUND?
LED: ON STEADY
CONTROL WILL CONTINUE TO CALL FOR COOLING
IN THIS CONDITION.
YES
NO
IS POLARITY CORRECT?
LED: 9 FLASHES
CONTROL WILL CONTINUE TO CALL FOR COOLING
IN THIS CONDITION.
YES
NO
LED: ON STEADY.
CONTROL WILL CONTINUE TO CALL FOR
COOLING IN THIS CONDITION.
IS VOLTAGE
ABOVE 90 VOLTS?
YES
LED: ON STEADY.
REMAINS UNCHANGED THROUGHOUT COOLING CYCLE.
THERMOSTAT CALLS FOR COOLING.
COMPRESSOR CONTACTOR AND SYSTEM FAN
ENERGIZED WITH 2‐SECOND DELAY
(COOLING SPEED). EAC TERM. ENERGIZED.
THERMOSTAT OPENS.
COMPRESSOR OFF.
SYSTEM FAN AND EAC TERM. OFF
WITH 60‐SECOND DELAY.
CONTINUOUS FAN SEQUENCE OF OPERATION
LED: ON STEADY
MANUAL FAN SELECTION MADE AT THERMOSTAT.
CONTROL (G) ENERGIZES SYSTEM FAN ON CONTINUOUS
BLOWER SPEED. EAC TERMINAL IS ENERGIZED.
THERMOSTAT CALLS FOR HEAT (W).
YES
NO
SYSTEM FAN SWITCHES TO
HEATING SPEED.
THERMOSTAT CALLS FOR COOLING.
YES
SYSTEM FAN SWITCHED TO COOL SPEED.
EAC TERM. REMAINS ON.
HUM TERM. ENERGIZES
WITH COMB. AIR INDUCER.
NO
THERMOSTAT OPENS.
HUM TERM. DE-ENERGIZES
WITH COMB. AIR INDUCER
THERMOSTAT OPENS.
MANUAL FAN SELECTION MADE AT THERMOSTAT.
CONTROL (G) ENERGIZES SYSTEM FAN ON
CONTINUOUS BLOWER SPEED.
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SYSTEM FAN SWITCHES TO
CONTINUOUS BLOWER SPEED
.