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.
ML193DF
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.
Table of Contents
Specifications2.................................
Optional Accessories3..........................
Blower Performance Data4......................
I-Unit Components6............................
II Placement and Installation18....................
III-Start-Up36...................................
IV-Heating System Service Checks37..............
V-Typical Operating Conditions39.................
VI-Maintenance40...............................
VII-Wiring and Sequence of Operation42...........
WARNING
Improper installation, adjustment, alteration, service
or maintenance can cause property damage, person
al injury or loss of life. Installation and service must
be performed by a licensed professional HVAC in
staller (or equivalent), service agency or the gas sup
plier.
WARNING
Sharp edges.
Be careful when servicing unit to avoid sharp edges
which may result in personal injury.
with eld supplied (PVC coupling) - o.d.3/43/43/43/4
Indoor
Blower
Wheel nom. dia. x width - in.10 x 810 x 810 x 1011 ½ x 10
Motor output - hp1/31/31/21
Tons of add-on cooling2.5 - 32.5 - 33 - 44 - 5
Air Volume Range - cfm605 - 1615560 - 1550920 - 21451210 - 2410
Electrical
Data
Blower motor full load amps6.16.18.211.5
Voltage120 volts - 60 hertz - 1 phase
Maximum overcurrent protection15151515
Shipping Datalbs. - 1 package124129147162
NOTE - Filters and provisions for mounting are not furnished and must be eld provided.
1
Annual Fuel Utilization Efciency based on DOE test procedures and according to FTC labeling regulations. Isolated combustion system rating for non-weatherized
furnaces.
Page 2
Page 3
OPTIONAL ACCESSORIES - MUST BE ORDERED EXTRA
“B” Width Models“C” Width Models
CABINET ACCESSORIES
Downow Combustible Flooring Base11M6011M61
CONDENSATE DRAIN KITS
Condensate Drain Heat Cable6 ft. 26K6826K68
24 ft.26K6926K69
50 ft.26K7026K70
Heat Cable TapeFiberglass - 1/2 in. x 66 ft.36G5336G53
Aluminum foil - 2 in. x 60 ft.16P8916P89
Crawl Space Vent Drain Kit51W1851W18
CONTROLS
Twinning Kit65W8065W80
DOWNFLOW FILTER KITS
Downow Air Filter and Rack Kit51W0751W08
No. and Size of lter - in.(2) 20 x 20 x 1(2) 20 x 20 x 1
NIGHT SERVICE KITS
Night Service Kit51W0351W03
TERMINATION KITS
See Installation Instructions for specic venting information.
Termination Kits Direct Vent Applications
Only
Termination Kits -
Direct or Non-Direct vent
Roof Termination Flashing Kit - Direct or Non-Direct Vent Contains two ashings
1
Cleanable polyurethane frame type lter.
2
Kits contain enough parts for two, non−direct vent installations.
3
Non-direct vent only.
NOTE - Termination Kits 44W92, 44W93, 30G28, 81J20 are certied to ULC S636 standard for use in Canada only.
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.
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)
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
result if repair is attempted.
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.
TRANSFORMER
(T1)
FIGURE 2
1. Transformer (T1)
A transformer located in the control box provides power to
the low voltage section of the unit. The transformers on all
models are rated at 40VA with a 120V primary and 24V
secondary.
2. Door Interlock Switch (S51)
A door interlock switch rated 14A at 120VAC is located on
the control box. The switch is wired in series with line volt
age. When the blower door is removed the unit will shut
down.
3. Integrated Ignition Control 100973 (A92)
TABLE 1
4-Pin Terminal Designation
PIN #FUNCTION
1Combustion Air Inducer Line
2
3
4
Ignitor Line
Combustion Air Inducer Neutral
Ignitor Neutral
TABLE 2
12-Pin Terminal Designations
PIN #FUNCTION
1High Limit Output
2Not Used
324V Line
4Not Used
5Rollout Switch Out
624V Neutral
7High Limit Input
8Ground
9Gas Valve Common
10Pressure Switch In
11Rollout Switch In
12Gas Valve Out
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.
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
Page 7
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
LED 1
LED 2
INTEGRATED CONTROL
(Automatic Hot Surface Ignition System)
TERMINAL DESIGNATIONS
HUM
LINE
XFMR
EAC
COOL
HEAT
PARK
FLAME
NEUTRALS
3 AMP, 32 VAC FUSE
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)
BLOWER OFF
DELAY JUMPER
FIGURE 4
Page 7
Page 8
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
FAST FLASH
SLOW FLASHON
OFFSLOW FLASH
ALTERNATING
SLOW FLASH
SLOW FLASHOFFFlame sensed without gas valve energized.
Power on - Normal operation.
Also signaled during cooling and continuous fan.
Normal operation - signaled when heating demand initiated at thermostat.
Primary or secondary limit switch open. Limit must close within 3 minutes or unit
goes into 1 hour Watchguard.
Pressure prove switch open.
OR: Blocked inlet/exhaust vent;
OR: Pressure switch closed prior to activation of combustion air inducer.
Watchguard 1 hour -- burners failed to ignite or lost flame 5 times during single
heating demand.
ON
ON
OFF
ON
OFF
ON
Circuit control failure or control wired incorrectly.
FAST FLASHSLOW FLASHMain power polarity reversed. Switch line and neutral.
SLOW FLASHFAST FLASHLow 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.
*4 Sec.Trial
for Ign.
**Blower “On”
Delay
End of
Heat Demand
5 SEC
Post
Purge
Blower
Off
Time
ON
OFF
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.
15 Sec.
Pre -Purge
20 sec.
Ignitor Warmup
FIGURE 5
Page 8
Page 9
4. Integrated Ignition Control 103085 (A92)
WARNING
Shock hazard.
Disconnect power before servicing. Control is not
field repairable. If control is inoperable, simply re
place entire control.
Can cause injury or death. Unsafe operation will re
sult if repair is attempted.
The hot surface ignition control system consisting of an in
tegrated control (figure 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.
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
4-Pin Terminal Designation
PIN #FUNCTION
1Combustion Air Inducer Line
2
3
4
Ignitor Line
Combustion Air Inducer Neutral
Ignitor Neutral
TABLE 5
12-Pin Terminal Designations
PIN #FUNCTION
1High Limit Output
2Sensor
324V Line
4Not Used
5Rollout Switch Out
624V Neutral
7High Limit Input
8Ground
9Gas Valve Common
10Pressure Switch In
11Rollout Switch In
12Gas Valve Out
TABLE 6
DIAGNOSTIC CODES
LED StatusDESCRIPTION
LED Off
LED OnNormal operation.
1 Flash
2 Flashes
3 Flashes
4 FlashesPrimary limit switch open.
5 FlashesRollout switch open.
6 FlashesPressure switch cycle lockout.
7 FlashesLockout, burners fail to light.
8 Flashes
9 FlashesLine 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.
No power to control or control harware
fault detected.
Flame present with gas vavle
de-energized.
Pressure switch closed with combustion
air inducer de-energized.
Pressure switch open with combus
tion air inducer energized.
Lockout, buners lost flame too many
times.
Page 9
Page 10
LED
ЙЙЙЙЙЙЙЙЙ
INTEGRATED CONTROL
(Automatic Hot Surface Ignition System)
TERMINAL DESIGNATIONS
HUM
LINE
XFMR
EAC
COOL
HEAT
PARK
CONT
NEUTRALS
TWIN
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)
TWIN
ON
OFF
DEMAND
CAI
IGNITOR
GAS VALVE
INDOOR BLOWER
*Blower on time will be 30 seconds after flame is sensed. Blower off time will depend on “OFF TIME” Setting.
PUSH BUTTON
Pre -PurgeIgnitor Warm-up
15
FIGURE 6
ELECTRONIC IGNITION
351
Trial for
Ignition
FIGURE 7
39
Blower “On”*
Delay
5 SEC69
Post
Purge
Page 10
Page 11
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
60 Second
off Time
60
90
120
180
achieve desired setting.
90 Second
off Time
60
90
120
180
120 Second
60
off Time
90
120
180
FIGURE 8
180 Second
off Time
60
90
120
180
Page 11
Page 12
FIELD WIRING FOR TWINNING THE ML193DF
TWO-STAGE THERMOSTAT
R
Call For Cool
Y
Call For Fan
G
Call For 1st
Stage Heat
Call For 2nd
StageHeat
W1
W2
ISOLATION
RELAY
TWIN
TWIN
SINGLE STAGE THERMOSTAT
R
TWIN 1
Y
G
Call For Cool
Call For Fan
Call For Heat
R
Y
G
W
W
C
ISOLATION
RELAY
R
TWIN 2
Y
G
W
TWIN
TWIN
R
TWIN 1
Y
G
W
C
R
TWIN 2
Y
G
W
C
C
FIGURE 9
Page 12
Page 13
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)
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.
NOTE - The ML193DF furnace contains electronic
components that are polarity sensitive. Make sure that
the furnace is wired correctly and is properly grounded.
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 +
a temperature rise. All flame rollout switches are manual
reset.
12_F (121_C + 6.7_C) on
SENSOR
ML193DF Burner Box Assembly
IGNITOR
BURNERS
ROLLOUT SWITCHES
FRONT BURNER BOX PLATE
GAS VALVE
FIGURE 10
Page 13
Page 14
IGNITOR CHECKS
TABLE 7
ControlOhms
103085
100973
39 to 70
24 to 47
Voltage +
120
95
10%
Multi−Meter
Test 1
(set to ohms)
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.
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.
Multi−Meter
(set to ohms)
Test 2
Integrated Control DetailIntegrated 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
Page 15
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.
Primary Limit Location and Heat Exchanger
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
UnitFuelOrifice Size
AllNatural0.0625
AllL.P./Propane0.034
Burner Detail Top Vie
w
IGNITOR
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)
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
SENSOR
ORIFICES
FIGURE 13
7. Gas Valve (GV1)
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)
INLET
PRESSURE
PORT
Gas Valve
MANIFOLD
PRESSURE
OUTLET
PORT
FIGURE 14
Page 15
Page 16
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
-0450.618
-0700.891
-0901.031
-1101.297
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.
BRACKET
24VAC
TERMINALS
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
ML193DF
0 - 4500
4501 -
7500
7501 - 10000
Set PointSetPointSet Point
-045
-070
-090
-110
-0.65-0.60-0.55
*Set point is factory set and non-adjustable
Page 16
Page 17
Measuring Pressure Differential
RED TUBING
NEGATIVE
BLACK TUBING
POSITIVE
1 - Remove thermostat demand and allow unit to cycle off.
2 - 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.
FIGURE 16
C-Blower Compartment
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.
Blower Motor Housing
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.
1.Blower Motor (B3) and Capacitor (C4)
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.
MOTOR
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
BOLTS
CAPACITOR
Page 17
Page 18
II-PLACEMENT AND INSTALLATION
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.
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.
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.
Page 18
Page 19
Input Size
045
070
090
110
OUTDOOR TERMINATION USAGE*
TABLE 12
STANDARDCONCENTRIC
Flush
Vent
Pipe
Dia. in.
Mount
Kit
51W11
(US)
51W12
2 inch3 inch2 inch
22G44 (US)
4
30G28 (CA)
(CA)
2
2-1/2
3
2
2-1/2
3
2
2-1/2
3
3
YESYES
3
YESYES
3
YESYES
3
YESYES
3
YESYES
3
YESYES
3
YESYESYES
3
YESYESYES
3
YESYESYES
2YESYESYES
2-1/2YESYES
3YESYES
Wall KitWall Ring Kit
44J40
(US)
4
81J20 (CA)
1
YES
1
YES
1
YES
1
YES
1
YES
1
YES
15F74
1
YES
1
YES
1
YES
1
YES
1
YES
1
YES
1-1/2 inch2 inch3 inch
Field
Fabricated
5
YES
5
YES
5
YES
5
YES
5
YES
5
YES
5
YESYESYES
5
YESYESYES
5
YESYESYES
5
YESYESYES
5
YESYESYES
5
YESYESYES
71M80
(US)
4
44W92
(CA)
2
YES
2
YES
2
YES
2
YES
2
YES
2
YES
69M29
(US)
4
44W92
(CA)
60L46 (US)
4
44W93 (CA)
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.
Concentric 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
Page 20
Joint Cementing Procedure
Venting Practices
All cementing of joints should be done according to the
specifications outlined in ASTM D 2855.
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
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.
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.
Piping Suspension Guidelines
SCHEDULE 40
PVC - 5'
all other pipe* - 3'
* See table 11 for allowable pipe.
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
insideoutside
Wall
FIGURE 18
REPLACING FURNACE THAT
CHIMNEY
OR GAS
VENT
(Check sizing
for water
heater only)
FURNACE
(Replaced
by ML193)
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.
WAS PART OF A COMMON
VENT SYSTEM
WATER
HEATER
OPENINGS
(To Adjacent
Room)
FIGURE 19
Page 20
Page 21
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.
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
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.
®
by DuraVent venting system the
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.
MINIMUM VENT PIPE LENGTHS
ML193DF
MODEL
045, 070, 090, 110
*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 PipingTerminations 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.
TABLE 13
MIN. VENT LENGTH*
15 ft. or
5 ft plus 2 elbows or
10 ft plus 1 elbow
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
Page 22
Piping Size Process
What is the
furnace capacity?
1
045, 070, 090 or
110?
Which style termination
2
3
4
being used?
Standard or concentric?
See table 12.
Which needs
most elbows?
Intake or
exhaust?
How many elbows?
Count all elbows inside
and outside house.
NOTE - It is acceptable to use any pipe size which fits within
the guidelines allowed in table 14.
NOTE 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.
All horizontal runs of exhaust pipe must slope back
Desired pipe size?
5
6
7
2”, 2-1/2”, 3”
What is the altitude of
the furnace installation?
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
Page 23
Maximum Allowable Intake or Exhaust Vent Length in Feet
TABLE 14
*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.
Number
Of 90°
Elbows
Used
1614624
2564119957538122122103103
35136149070331171179898
44631
541268060231071078888
636217555181021028383
7311670501397977878
826116545
921
1016553582826363
Number
Of 90°
Elbows
Used
1533822
24833178565341061069999
34328128060291011019494
43823
5331870501991918484
6281365451486867979
723
818553576766969
913503071716464
10n/a452566665959
045070090110045070090110045070090110
045070090110045070090110045070090110
2” Pipe2-1/2” Pipe3” Pipe
ModelModelModel
1008043
8565281121129393
n/a
n/a
n/a
Concentric Termination Elevation 0 - 10,000 ft.
2” Pipe2-1/2” Pipe3” Pipe
ModelModelModel
n/a
n/a
n/a
604087876868
907039
75552496968989
6040
n/a
n/a
n/a
n/a
127127108108
92927373
111111104104
81817474
Maximum Allowable Exhaust Vent Lengths With Furnace Installed in a Closet or Basement Using Ventilated
NOTE - Additional vent pipe and elbows used to terminate the vent pipe outside the structure must be included in the total vent length calculation.
Number
Of 90°
Elbows
Used
1513614
2463198060231021028383
34126475551897977878
43621
531166545887876868
626116040382826363
72165535
8161503072725353
911
106402062624343
045070090110045070090110045070090110
2” Pipe2-1/2” Pipe3” Pipe
ModelModelModel
n/a
n/a
TABLE 15
Attic or Crawl Space For Intake Air in Feet
Standard Termination at Elevation 0 - 10,000 ft.
856528
70501392927373
n/a
452567674848
n/a
n/a
Page 23
1071078888
77775858
Page 24
TYPICAL EXHAUST PIPE CONNECTIONS
Pipe size determined in table 14.
*2”
2”
2”
or
DO NOT transition from smaller
to larger pipe size in horizontal
runs of exhaust pipe.
2”
2”
3”
TRANSITION
* 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
2”
INTAKE
EXHAUST
TOP VIEW
Pipe size determined in table 14.
2”
3”
TRANSITION
*2”
* 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
Intake Piping
The ML193DF furnace may be installed in either direct
vent or non-direct vent applications. In non-direct vent
applications, when intake air will be drawn into the furnace
from the surrounding space, the indoor air quality must be
considered. Guidelines listed in Combustion, Dilution and
Ventilation Air section must be followed.
2”
2”
*2”
2”
or
TRANSITION
*2”
2”
3”
INTAKE
TOP VIEW
Follow the next two steps when installing the unit in Direct
Vent applications, where combustion air is taken fromoutdoors and flue gases are discharged outdoors. The
provided air intake screen must not be used in direct
vent applications (outdoors).
1 - Use cement to secure the intake pipe to the inlet air
connector.
EXHAUST
Page 24
Page 25
2 - Route piping to outside of structure. Continue with
e
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.
TYPICAL AIR INTAKE PIPE CONNECTIONS
NON−DIRECT VENT APPLICATIONS
AIR
INTAKE
SCREEN
(Provided)
(Inlet Air from Ventilated Attic and Outlet Air to Outside)
Roof T erminated
Exhaust Pipe
EQUIPMENT IN CONFINED SPACE
Ventilation Louvers
Inlet Air
(Minimum
12 in.(305mm) Abov
attic floor)
*Intake Debris
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
hour of the total input rating of all equipment in the enclosure.
2
per 1.17kW) per
FIGURE 24
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 takenfrom indoors and flue gases are discharged outdoors.
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.
(Inlet Air from Ventilated Crawlspace and Outlet Air to Outside)
Roof T erminated
Exhaust Pipe
Ventilation
Louvers
(Crawl space)
(Field Provided)
EQUIPMENT IN CONFINED SPACE
Furnace
Coupling or
3 in. to 2 in.
Transition
12 in.(305mm)
*Intake Debris Screen Provided)
Inlet Air
(Minimum
Above crawl
space floor)
* 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
hour of the total input rating of all equipment in the enclosure.
2
per 1.17kW) per
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
Page 26
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
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.
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).
Maximum Allowable Exhaust Vent Pipe Length (in ft.) Without Insulation In Unconditioned Space For
TABLE 16
Winter Design Temperatures Single - Stage High Efficiency Furnace
Winter Design
Temperatures
(-18 to -29)
1Refer to 99% Minimum Design Temperature table provided in the current edition of the ASHRAE Fundamentals Handbook.
2
Poly-Propylene 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.
32 to 21
(0 to -6)
20 to 1
(-7 to -17)
0 to -20
1
°F (°C)
Vent Pipe
Diameter
2 in.2624444144442424N/AN/A
2-1/2 in.18N/A32N/A50N/A58N/AN/AN/A
3 in.14122623383355496053
2 in1615282640372424N/AN/A
2-1/2 in.12N/A20N/A30N/A44N/AN/AN/A
3 in.981614262332284035
2 in.109201830282424N/AN/A
2-1/2 in.8N/A14N/A20N/A32N/AN/AN/A
3 in.43108161426233026
045070090110135
PVC
2
PPPVC
Unit Input Size
2
PPPVC
2
PPPVC
2
PPPVC
2
PP
Conditioned
Space
Conditioned
Space
FIGURE 26
Page 26
Pipe Insulation
Unconditioned
Space
Exhaust
Pipe
Intake
Pipe
Page 27
VENT TERMINATION CLEARANCES
FOR NON-DIRECT VENT INSTALLATIONS IN THE USA AND CANADA
INSIDE CORNER
DETAIL
G
D
A
E
B
L
C
Fixed
F
Closed
Operable
B
Operable
B
B
VENT TERMINAL
AIR SUPPLY INLET
US Installations
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
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
* 12”
* Equal to or greater than soffit depth.
horizontal distance of 2 feet (610 mm)
from the center line of the terminal
E =
F =
G =
H =
Clearance to unventilated soffit
Clearance to outside corner
Clearance to inside corner
Clearance to each side of center line ex
tended above meter / regulator assembly
I =
Clearance to service regulator
vent outlet
J =
Clearance to non-mechanical air
supply inlet to building or the com
bustion air inlet to any other ap
* Equal to or greater than soffit depth.
* No minimum to outside corner* No minimum to outside corner
**
3 feet (.9m) within a height 15 feet (4.5m)
*
above the meter / regulator assembly
* 3 feet (.9m)
4 feet (1.2 m) below or to side of opening;
1 foot (30 cm) above opening
pliance
K =
L =
Clearance to mechanical air sup
ply inlet
Clearance above paved sidewalk or
3 feet (.9m) above if within 10 feet
(3m) horizontally
7 feet (2.1m)†
paved driveway located on public property
M =
Clearance under veranda, porch, deck or balcony
1
In accordance with the current ANSI Z223.1/NFPA 54 Natural Fuel Gas Code
2
In 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.
*12 inches (305mm)‡
FIGURE 27
H
B
Fixed
Closed
A
J
I
M
AREA WHERE TERMINAL
IS NOT PERMITTED
1
Canadian Installations
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”
* Equal to or greater than soffit depth.
* Equal to or greater than soffit depth.
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
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)
7 feet (2.1m)†
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.”
K
2
Page 27
Page 28
VENT TERMINATION CLEARANCES
FOR DIRECT VENT INSTALLATIONS IN THE USA AND CANADA
INSIDE CORNER
DETAIL
G
D
A
E
B
L
C
Fixed
F
Closed
Operable
B
Operable
B
B
VENT TERMINAL
AIR SUPPLY INLET
US Installations
A =
B =
Clearance above grade, veranda,
porch, deck or balcony
Clearance to window or
door that may be opened
12 inches (305mm) or 12 in. (305mm)
above average snow accumulation.
6 inches (152mm) for appliances <10,000
Btuh (3kw), 9 inches (228mm) for ap
pliances > 10,000 Btuh (3kw) and <50,000
Btuh (15 kw), 12 inches (305mm) for ap
pliances > 50,000 Btuh (15kw)
C =
Clearance to permanently
* 12”
closed window
D =
Vertical clearance to ventilated soffit
located above the terminal within a
* Equal to or greater than soffit depth
horizontal distance of 2 feet (610mm)
from the center line of the terminal
E =
F =
G =
H =
Clearance to unventilated soffit
Clearance to outside corner
Clearance to inside corner
Clearance to each side of center line ex
tended above meter / regulator assembly
I =
Clearance to service regulator
vent outlet
J =
Clearance to non-mechanical air
supply inlet to building or the com
bustion air inlet to any other ap
pliance
* 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)
*
6 inches (152mm) for appliances <10,000
Btuh (3kw), 9 inches (228mm) for ap
pliances > 10,000 Btuh (3kw) and <50,000
Btuh (15 kw), 12 inches (305mm) for ap
pliances > 50,000 Btuh (15kw)
K =
L =
M =
1
In accordance with the current ANSI Z223.1/NFPA 54 Natural Fuel Gas Code
2
In 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.
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)
*12 inches (305mm)‡
FIGURE 28
H
B
Fixed
Closed
A
J
I
M
K
AREA WHERE TERMINAL
IS NOT PERMITTED
1
Canadian Installations
2
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”
* 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)
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)
7 feet (2.1m)†
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.”
Page 28
Page 29
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
EXHAUST PIPE TERMINATION SIZE REDUCTION
ML193
MODEL
*045 and *070
*0902” (51mm)
110
*ML193DF-045, -070 and -090 units with the flush-mount termination
must use the 1-1/2”accelerator supplied with the kit.
Exhaust Pipe Size
2” (51mm), 2-1/2” (64mm),
3” (76mm)
3” (76mm)
Termination
Pipe Size
1-1/2” (38mm)
2” (51mm)
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.
NOTE - Care must be taken to avoid recirculation of
exhaust back into intake pipe.
Exiting Exhaust and Intake Vent
(different pressure zones)
Exhaust
Pipe
Furnace
Inlet Air
(Minimum 12 in.
305 MM) above
grade or snow
accumulation
FIGURE 29
Exiting Exhaust and Intake Vent
(different pressure zones)
Roof T
erminated
Exhaust Pipe
Inlet Air
Furnace
(Minimum 12 in.
305 MM) above
grade or snow
accumulation
FIGURE 30
Inches(mm)
8” (203mm) MIN
12” (305mm) ABOVE
AVERAGE SNOW
ACCUMULATION
3” (76mm) OR
2” (51mm) PVC
PROVIDE SUPPORT
FOR INTAKE AND
EXHAUST LINES
DIRECT VENT ROOF TERMINATION KIT
3”(76mm) MAX.
(15F75 or 44J41)
SIZE TERMINATION
PIPE PER TABLE 17.
UNCONDITIONED
ATTIC SPACE
1/2” (13mm) FOAM
INSULATION IN
UNCONDITIONED
SPACE
FIGURE 31
Page 29
Page 30
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.
1-1/2” (38mm) accelerator
provided on 71M80 & 44W92
12” (305mm)
Minimum
Above Average
Snow
Accumulation
kits for ML193DF045P36B- &
INTAKE
070P36B
FLASHING
(Not Furnished)
EXHAUST
VENT
INTAKE
AIR
Inches (mm)
optional intake elbow
OPTIONAL VENT TERMINATION FOR MULTIPLE UNIT
INSTALLATION OF DIRECT VENT WALL TERMINATION KIT
5”
(127mm)
18” MAX.
(457mm)
EXHAUST VENT
Side View
(30G28 or 81J20)
INTAKE
AIR
12”
(305mm)
5-1/2”
(140mm)
Front View
12” (305mm) Min.
above grade or
average snow ac
cumulation.
FIGURE 34
2” EXTENSION FOR 2” PVC
PIPE1” EXTENSION FOR 3”
PVC PIPE
4''
FURNACE
EXHAUST
PIPE
SHEET METAL STRAP
(Clamp and sheet metal strap
must be field installed to support
CLAMP
DIRECT VENT CONCENTRIC ROOFTOP TERMINATION
71M80, 69M29 or 60L46 (US)
41W92 or 41W93 (Canada)
the weight of the termination kit.)
FIELD-PROVIDED
REDUCER MAY BE REQUIRED
TO ADAPT LARGER VENT
PIPE SIZE TO TERMINATION
FIGURE 32
1-1/2” (38mm) accelerator
FIELD-PROVIDED
REDUCER MAY BE
REQUIRED TO ADAPT
LARGER VENT PIPE
SIZE TO TERMINA
TION
EXHAUST
AIR
INTAKE
AIR
DIRECT VENT CONCENTRIC WALL TERMINATION
OUTSIDE
WALL
CLAMP
(Not Furnished)
71M80, 69M29 or 60L46 (US)
41W92 or 41W93 (Canada)
provided on 71M80 &
44W92 kits for
ML193DF045P36B- &
070P36B
INTAKE
AIR
EXHAUST
AIR
12” (305mm) Min.
INTAKE
AIR
above grade or
average snow ac
cumulation.
GRADE
FIGURE 33
FURNACE
INTAKE
PIPE
GLUE EXHAUST
END FLUSH INTO
TERMINATION
FLAT
SIDE
1-1/2” ACCELERATOR
(all -45, -070 and -090 units)
FLUSH-MOUNT SIDE WALL TERMINATION
51W11 (US) or 51W12 (Canada)
FIGURE 35
Page 30
Page 31
NOTE − FIELD−PROVIDED
REQUIRED TO ADAPT
LARGER VENT PIPE SIZE
* WALL
SUPPORT
C1
REDUCER MAY BE
TO TERMINATION
C1
A
E
D
B
STRAIGHT
APPPLICATION
D
B
A
EXTENDED
APPLICATION
FIELD FABRICATED WALL TERMINATION
A− Minimum clearance
above grade or average
snow accumulation
B− Maximum horizontal
separation between
intake and exhaust
C1 -Minimum from end of
exhaust to inlet of intake
C2 -Minimum from end of
exhaust to inlet of intake
D− Maximum exhaust
pipe length
E− Maximum wall support
distance from top of each
pipe (intake/exhaust)
D
B
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.
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.
B
Intake
Elbow
Intake and Exhaust
Intake
C
A
Front View of
Exhaust
D
Exhaust
3
A− Clearance above
grade or average snow
accumulation
B− Horizontal
separation between
intake and exhaust
C− Minimum from
end of exhaust to
inlet of intake
D− Exhaust pipe length
E− Wall support distance
from top of each pipe
(intake/exhaust)
Vent Pipe
12” (305 mm) Min. 12” (305 mm) Min.
6” (152 mm) Min.
24” (610 mm) Max.
9” (227 mm) Min.
12” (305 mm) Min.
16” (405 mm) Max.
6” (152 mm) Max.
3” (76MM)
Vent Pipe
6” (152 mm) Min.
24” (610 mm) Max.
9” (227 mm) Min.
12” (305 mm) Min.
20” (508 mm) Max.
6” (152 mm) Max.
FIGURE 36
Page 31
Page 32
ML193DF DIRECT VENT APPLICATION
USING EXISTING CHIMNEY
8” - 12”
(203mm - 305mm)
Minimum 12” (305MM)
above chimney top
plate or average snow
accumulation
*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.
INTAKE PIPE
INSULATION (optional)
SHEET
METAL TOP
PLATE
INSULATE
TO FORM
SEAL
3” - 8”
(76mm203mm)
STRAIGHT-CUT OR
ANGLE-CUT IN DIRECTION
OF ROOF SLOPE *
EXHAUST VENT
1/2” (13mm)
WEATHERPROOF
INSULATION
SHOULDER OF FITTINGS
PROVIDE SUPPORT
OF PIPE ON TOP PLATE
3” - 8”
(76mm203mm)
ALTERNATE
INTAKE PIPE
EXTERIOR
PORTION OF
CHIMNEY
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.
SIZE TERMINATION
PIPE PER TABLE
12” (305mm)
ABOVE AVE.
SNOW
ACCUMULATION
1/2” (13mm) FOAM
INSULATION
17.
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.
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.
ML193DF NON-DIRECT VENT APPLICATION
USING EXISTING CHIMNEY
SIZE TERMINATION
PIPE PER TABLE 17.
3” - 8”
(76mm-
Minimum 12” (305MM)
above chimney top
plate or average snow
accumulation
METAL TOP
INSULATE
TO FORM
SEAL
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.
203mm)
SHEET
PLATE
STRAIGHT-CUT OR
ANGLE-CUT IN DIRECTION
OF ROOF SLOPE
EXHAUST VENT
1/2” (13mm)
WEATHERPROOF
INSULATION
SHOULDER OF FITTINGS
PROVIDE SUPPORT
OF PIPE ON TOP PLATE
3” - 8”
(76mm-
203mm)
EXTERIOR
PORTION OF
CHIMNEY
FIGURE 39
3” (76mm) OR
2” (51mm) PVC
PROVIDE SUPPORT
FOR EXHAUST LINES
NON-DIRECT VENT ROOF TERMINATION KIT
(15F75 or 44J41)
FIGURE 38
UNCONDITIONED
ATTIC SPACE
Page 32
Page 33
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.
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.
Plug
(same on left
side)
Field Provided Drain Components
Elbow
Barbed Fitting
Tubing
Hose Clamp
FIGURE 41
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.
CAUTION
Donot use copper tubing or existing copper
condensate lines for drain line.
Page 33
Page 34
CONDENSATE TRAP LOCATION
(shown with right side exit of condensation)
Trap can be installed a maxi
mum of 5ft. from furnace (*PVC
only)
Field Provided Vent
1” min. 2” max. above
condensate drain.
1” min.
2” max.
5’ max.
ML193DF with Evaporator Coil
Using a Separate Drain
Field Provided Vent
1” min. 2” max. above
condensate drain.
Condensate Drain
Connection
Evaporator Drain Line
(vent required)
to drain
*Piping from furnace must slope down a
minimum 1/4” per ft. toward trap
FIGURE 42
Condensate Trap With Optional Overflow Switch
From Evaporator Coil
Optional
Field Provided Vent
1” min. 2” max. above
condensate drain.
FurnaceCondensate
Drain
Connection
Drain
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.
ML193DF with Evaporator
Coil Using a Common Drain
Field Provided Vent
1” min. 2” max. above
condensate drain.
Condensate Drain
Connection
FIGURE 43
Evaporator Drain Line
(vent required)
FIGURE 45
Page 34
Page 35
it
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)
Condensate Drain
Connection In Unit
90° Street Elbow
3/4 inch PVC
( furnished)
To
Trap
OptionalDrainPipingFromTrap
Drain Assembly for 1/2 inch Drain Pipe
1/2 inch PVC Pipe
(Not Furnished)
90° Elbow
1/2 inch PVC
(Not Furnished)
To
Drain
Drain Assembly for 3/4 inch Drain Pipe
1 (25mm) Min.
2 (50 mm) Max.
Above Top Of
Condensate Drain
Connection In Unit
Elbow 3/4 inch PVC
90°
(Not Furnished)
1/2 inch PVC Pipe
(Not Furnished)
Adapter 3/4 inch slip X
3/4 inch mpt (not furnished)
V
ent
5 Feet
Maximum
3/4 inch PVC Pipe
(Not Furnished)
Coupling 3/4 inch slip X slip
(Not Furnished)
Drain Trap
Assembly
(Furnished)
Condensate Drain
Connection In Un
90° Elbow
3/4 inch PVC
(Not Furnished)
To
Drain
DrainTrapAssembly
(Furnished)
7
(178)
Drain Trap
Clean Out
90° Elbow
3/4 inch PVC
(Not Furnished)
T
o
Coupling 3/4 inch slip X slip
Drain
DrainTrap Assembly with 1/2 inch Piping
1 (25 mm) Min. 2 (50 mm) Max. Above Top
Of Condensate Drain Connection In Unit
(Not Furnished)
Vent
1/2 inch
Condensate Drain
Connection In Unit
To
Drain
DrainTrap Assembly with 3/4 inch Piping
1 (25 mm) Min. 2 (50 mm) Max. Above Top
Of Condensate Drain Connection In Unit
Vent
3/4 inch
Condensate Drain
Connection In Unit
To
Drain
FIGURE 46
Page 35
Page 36
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)
Condensate Drain
Connection In Unit
90° Street Elbow
1/2 inch PVC
(Furnished)
To
Trap
Optional Drain Piping From Trap
Drain Assembly for 1/2 inch Drain Pipe
1/2 inch PVC Pipe
(Not Furnished)
90° Elbow
1/2 inch PVC
(Not Furnished)
To
Drain
Drain Assembly for 3/4 inch Drain Pipe
1 (25 mm) Min.
2 (50 mm) Max.
Above Top Of
Condensate Drain
Connection In Unit
90° Elbow 1/2 inch PVC
(Not Furnished)
1/2 inch PVC Pipe
(Not Furnished)
Adapter 1/2 inch slip X
1/2 inch mpt (Not Furnished)
Vent
5 Feet
Maximum
1/2 inch PVC Pipe
(Not Furnished)
Coupling 1/2 inch slip X slip
(Not Furnished)
Drain Trap
Assembly
(Furnished)
Condensate Drain
Connection In Unit
90° Elbow
3/4 inch PVC
(Not Furnished)
To
Drain
Drain Trap Assembly
(Furnished)
7
(178)
90° Elbow
3/4 inch PVC
(Not Furnished)
To
Coupling 3/4 inch slip X slip
Drain
Drain Trap Assembly with 1/2 inch Piping
1 (25 mm) Min. 2 (50 mm) Max. Above Top
Of Condensate Drain Connection In Unit
(Not Furnished)
Vent
1/2 inch
Condensate Drain
Connection In Unit
To
Drain
Drain Trap
Clean Out
Drain Trap Assembly with 3/4 inch Piping
Drain Trap Assembly with 3/4 inch Piping
1 (25 mm) Min. 2 (50 mm) Max. Above Top
Of Condensate Drain Connection In Unit
Vent
3/4 inch
Condensate Drain
Connection In Unit
To
Drain
FIGURE 47
Page 36
Page 37
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)
INLET
PRESSURE
PORT
GAS VALVE SHOWN IN ON POSITION
MANIFOLD
PRESSURE
OUTLET
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
Page 38
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.
B-Gas Piping
available through Lennox under part number 31B2001.
See Corp. 8411-L10, for further details.
WARNING
Do not use matches, candles, flame or any other
source of ignition to check for gas leaks.
CAUTION
If a flexible gas connector is required or allowed by
the authority that has jurisdiction, black iron pipe
shall be installed at the gas valve and extend outside
the furnace cabinet. 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
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
FURNACE
ISOLATE
GAS VALVE
D-Testing Gas Supply Pressure
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
Page 39
F- Proper Gas Flow (Approximate)
Gas Flow (Approximate)
TABLE 18
GAS METER CLOCKING CHART
Seconds for One Revolution
ML193
Unit
-04580160200400
-07055110136272
-0904182102204
-110336682164
Natural-1000 btu/cu ft LP-2500 btu/cu ft
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.
Manifold and Supply Pressure (Outlet) inches w.c.
At All Altitudes For -1 Through -6 Units
Fuel
Nat. GasAll sizes3.54.513.0
L.P. GasAll sizes10.011.013.0
NaturalLP
1 cu ft
Dial
2 cu ft
Dial
TABLE 19
Model
Input Sizes
Manifold
Pressure in.wg.
1 cu ft
Dial
2 cu ft
DIAL
Supply
Pressure in.wg.
Min.Max.
G- Proper Combustion
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 20
ML193
Unit
CO2%
For Nat
CO2%
For L.P.
-045
-070
-090
7.2 - 7.98.6 - 9.3
-110
The carbon monoxide reading should not exceed 50 ppm.
H- High Altitude
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.
TABLE 21
Manifold and Supply Line Pressure 0-10,000ft. For -7 Units and Later
Manifold Pressure in. wg.
ML193
Unit
All Sizes
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.
Gas
0-4500 ft.4501-5500 ft. 5501-6500 ft.
Natural3.53.33.23.13.54.513.0
LP/propane10.09.49.18.910.011.013.0
6501 -
7500ft.
7501 - 10000ft.
Supply Line
0 - 10000 ft.
TABLE 22
Conversion Kit and Pressure Switch Requirements at Varying Altitudes
Natural to
ML193
Unit
-045
-070
-090
-110
* 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).
LP/Propane
0 - 7500 ft
(0 - 2286m)
*69W7373W37*73W8193W8793W88
High Altitude
Natural Burner Ori
fice Kit
7501 - 10,000 ft
(2286 - 3038m)
LP/Propane to
Natural
0 - 7500 ft
(0 - 2286m)
High Altitude Pressure Switch
4501 - 7500 ft
(1373 - 2286m)
7501 -10,000 ft
(2286 - 3048m)
Pressure
in. w.g.
Page 39
Page 40
I-Flame Signal
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.
TABLE 23
Normal Flame Signal
Low Flame Signal
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
(+) TO
IGNITION
CONTROL
SENSOR
WIRE
FIGURE 50
1.50 Microamps
1.40 Microamps
SET DIAL TO
MEASURE VDC
(+)
(-)
(-) TO
FLAME
SENSOR
TRANSDUCER
PART #78H5401
RED COLLAR
INDICATES
POSITIVE
LEAD
V-TYPICAL OPERATING CHARACTERISTICS
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:
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.
2 - Punch a 1/4” diameter hole
in supply and return air ple
nums. Insert manometer
hose flush with inside edge
of hole or insulation. Seal
around the hose with perma
gum. Connect the zero end
of the manometer to the dis
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.
STATIC PRESSURE
TEST
filter
coil
FIGURE 50
Page 40
Page 41
VI-MAINTENANCE
Furnace
Cabinet Width
TABLE 24
Filter Size
WARNING
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.
17-1/2”
21”
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 +
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.
16 x 25 x 1 (1)
10%
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.
Filters
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).
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.
Condensate Hose Screen
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
Page 42
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
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
Page 43
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
Page 44
Sequence of Operation Flow Chart - Integrated Control 100973
HEATING SEQUENCE OF OPERATION
NORMAL HEATING MODE
POWER ON
CONTROL SELF-CHECK OKAY?
YES
IS POLARITY CORRECT?
YES
IS THERE A PROPER GROUND?
YES
IS VOLTAGE
ABOVE 90 VOLTS?
YES
ROLLOUT SWITCH CLOSED?
YES
NO
NO
NO
ABNORMAL HEATING MODE
GAS VALVE OFF. COMBUSTION AIR INDUCER OFF.
(RESET CONTROL BY TURNING MAIN POWER OFF.)
NO
NO
HEATING UNTIL VOLTAGE RISES ABOVE 95 VOLTS.
GAS VALVE OFF. COMBUSTION AIR INDUCER ON.
SEQUENCE HOLDS UNTIL ROLLOUT SWITCH CLOSES
AND POWER IS RESET OR T'STAT IS INTERRUPTED
INDOOR BLOWER DELAY OFF.
LED #1 ON
LED #2 ON
POLARITY REVERSED.
LED #1 -- FAST FLASH
LED #2 -- SLOW FLASH
IMPROPER GROUND.
LED #1 -- ALTERNATING FAST FLASH
LED #2 -- ALTERNATING FAST FLASH
LEDs SIGNAL FAST ALTERNATING FLASH.
CONTROL WILL NOT RESPOND TO A CALL FOR
INDOOR BLOWER ON.
LED #1 -- ON. LED #2 -- SLOW FLASH.
FOR MINIMUM OF 1 SECOND.
NO
(Flame sensed without gas valve energized)
BURNER OFF?
YES
NORMAL OPERATION:
LED #1 -- SLOW FLASH
LED #2 -- SLOW FLASH
YES
THERMOSTAT CALLS FOR HEAT:
LED #1 -- FAST FLASH
LED #2 -- FAST FLASH
YES
PRIMARY LIMIT SWITCH. CLOSED?
YES
IS COMBUSTION AIR
PRESSURE SWITCH OPEN?
YES
IS COMBUSTION AIR INDUCER
ENERGIZED?
YES
HAS COMBUSTION AIR PRESSURE
SWITCH CLOSED IN 2.5 MINUTES?
YES
NO
NO
GAS VALVE OFF. COMBUSTION AIR INDUCER ON.
INDOOR BLOWER ON HEATING SPEED.
NO
NO
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?
LED #1 -- SLOW FLASH
LED #2 -- OFF
COMBUSTION AIR INDUCER OFF.
INDOOR BLOWER ON
LED #1 SLOW FLASH RATE
LED #2 -- ON
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.)
YES
CONTINUED NEXT
PAGE
Page 44
Page 45
HEATING SEQUENCE CONTINUED
NORMAL HEATING MODEABNORMAL HEATING MODE
15‐SECOND COMBUSTION AIR INDUCER PREPURGE
INITIATED BY CLOSED PRESSURE SWITCH.
YES
IGNITOR WARM‐UP -- 20 SECONDS.
YES
4‐SECOND TRIAL FOR IGNITION.
GAS VALVE OPENS. IGNITOR ENERGIZED FOR
FIRST 3 SECONDS OF THE TRIAL.
YES
FLAME STABILIZATION PERIOD.
4 SECONDS
FLAME RECTIFICATION CURRENT
CHECK. CAN FLAME BE PROVEN WITHIN
4 SECONDS AFTER GAS VALVE OPENS?
(0.5 microamps)
YES
FLAME PRESENT?
YES
FLAME SIGNAL 1.5 MICROAMPS OR GREATER?
YES
INDOOR BLOWER ON
AFTER 30-SECOND DELAY
YES
PRIMARY AND SECONDARY LIMIT
SWITCHES CLOSED?
YES
NO
IS VOLTAGE ABOVE 90 VOLTS?
YES
GAS VALVE OFF. COMBUSTION AIR INDUCER ON.
NO
HAS CONTROL FAILED TO SENSE FLAME FOR
FIVE CONSECUTIVE TRIES DURING A SINGLE
WATCHGUARD MODE. GAS VALVE OFF.
LEDs SIGNAL WATCHGUARD FAILURE CODE.
IS 60‐MINUTE RESET PERIOD COMPLETE?
NO
NO
(Does not affect operation of control)
LED #1 -- SLOW FLASH
COMBUSTION AIR INDUCER DE-ENERGIZED.
INDOOR BLOWER ON UNTIL SWITCH CLOSES.
NO
LED #1 -- SLOW FLASH. LED #2 -- ON.
HAS PRIMARY / SECONDARY
INDOOR BLOWER OFF.
HEAT DEMAND?
COMBUSTION AIR INDUCER OFF.
INDOOR BLOWER OFF WITH DELAY
HAS CONTROL RESET IGNITION
SEQUENCE FOUR TIMES?
LOW FLAME SIGNAL
LED #2 -- FAST FLASH
GAS VALVE DE-ENERGIZED.
IS LIMIT SWITCH CLOSED?
YES
LIMIT RESET TIME
EXCEEDED 3 MINUTES?
LEDS SIGNAL
NO
LIMIT SWITCH WATCHGUARD
MODE. GAS VALVE, COMB. AIR
INDUCER AND INDOOR BLOW
ER OFF. LEDs SIGNAL LIMIT
SWITCH OPEN UNTIL MAIN
YES
ALTERNATING
FAST FLASH UNTIL
VOLTAGE IS ABOVE
95 VOLTS, THEN
RESTARTS HEATING
SEQUENCE.
NO
YES
YES
NO
YES
POWER IS
INTERRUPTED OR
T'STAT IS CYCLED
OFF/ON FOR 1 SEC.
MINIMUM. 60-MIN
UTE WATCHGUARD
PERIOD STARTS AT
TIME LIMIT CLOSES.
IS 60-MIN. PERIOD
COMPLETE?
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
SEQUENCE HOLDS UNTIL ROLLOUT SWITCH IS RESET
NO
THERMOSTAT IS CYCLED OFF/ON FOR 1 SEC. MINIMUM.
HAS PRESSURE SWITCH OPENED 5
TIMES IN THE SAME HEAT DEMAND?
GAS VALVE DE-ENERGIZED.
COMBUSTION AIR INDUCER ON.
INDOOR BLOWER OFF WITH DELAY
LED #1 -- OFF. LED #2 -- SLOW FLASH.
HAS CAB SWITCH CLOSED IN 2.5 MINUTES?
5‐MINUTE PRESSURE SWITCH
WATCHGUARD MODE.
GAS VALVE POWER OFF.
COMBUSTION AIR INDUCER POWER ON.
INDOOR BLOWER ON
LED #1 -- ON. LED #2 -- SLOW FLASH.
AND MAIN POWER IS INTERRUPTED OR
NO
NO
Page 45
YES
WATCHGUARD
1 HR
PRESSURE
SWITCH
MODE
Page 46
COOLING SEQUENCE OF OPERATION
NORMAL COOLING MODEABNORMAL COOLING MODE
POWER ON
IGNITION CONTROL MAIN POWER ON.
CONTROL SELF DIAGNOSTIC CHECK.
IS CONTROL OPERATING NORMALLY?
YES
IS THERE A PROPER GROUND?
YES
IS POLARITY CORRECT?
YES
NO
IS VOLTAGE
ABOVE 90 VOLTS?
YES
ROLLOUT SWITCH MONITORED CONTINUOUSLY.
IS ROLLOUT SWITCH CLOSED?
YES
NO
NO
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.
NO
NO
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.
LED SIGNALS LOW VOLTAGE. CONTROL WILL
CONTINUE TO CALL FOR COOLING
IN THIS CONDITION.
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.
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
Page 47
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).
NO
THERMOSTAT CALLS FOR COOLING.
YES
SYSTEM FAN SWITCHED TO COOL SPEED.
EAC TERM. REMAINS ON.
THERMOSTAT OPENS.
MANUAL FAN SELECTION MADE AT THERMOSTAT.
CONTROL (G) ENERGIZES SYSTEM FAN AT HEAT
SPEED. EAC TERM. ENERGIZED.
NO
HUM TERM. ENERGIZES
WITH COMB. AIR INDUCER.
YES
SYSTEM FAN REMAINS ON
HEATING SPEED.
THERMOSTAT OPENS.
HUM TERM. DE-ENERGIZES
WITH COMB. AIR INDUCER
SYSTEM FAN REMAINS ON
HEATING SPEED.
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Page 48
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
Page 49
Sequence of Operation Flow Chart - Integrated Control 103085
HEATING SEQUENCE OF OPERATION
NORMAL HEATING MODE
POWER ON
CONTROL SELF-CHECK OKAY?
YES
IS POLARITY CORRECT?
YES
IS THERE A PROPER GROUND?
YES
IS VOLTAGE
ABOVE 90 VOLTS?
YES
ROLLOUT SWITCH CLOSED?
YES
NO
NO
ABNORMAL HEATING MODE
NO
NO
NO
GAS VALVE OFF. COMBUSTION AIR INDUCER OFF.
INDOOR BLOWER DELAY OFF.
LED: OFF
POLARITY REVERSED.
LED: 9 FLASHES
IMPROPER GROUND.
LED: OFF
CONTROL WILL NOT RESPOND TO CALL FOR HEAT
UNTIL PROPER GROUND.
LED: ON STEADY
IGNITOR WILL GLOW DIMLY BUT WILL NOT LIGHT
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
BURNER OFF?
(Contiuous Flame Check)
YES
NORMAL OPERATION:
LED: STEADY ON
YES
THERMOSTAT CALLS FOR
HEAT:
LED: STEADY ON
YES
PRIMARY AND SECONDARY LIMIT SWITCH.
CLOSED?
YES
IS COMBUSTION AIR
PRESSURE SWITCH OPEN?
YES
IS COMBUSTION AIR INDUCER
ENERGIZED?
YES
HAS COMBUSTION AIR PRESSURE
SWITCH CLOSED IN 2.5 MINUTES?
YES
CONTINUED NEXT
PAGE
NO
NO
GAS VALVE OFF. COMBUSTION AIR INDUCER ON.
INDOOR BLOWER ON HEATING SPEED.
COMBUSTION AIR INDUCER OFF.
NO
NO
PRESSURE SWITCH IS IN WATCHGUARD MODE.
GAS VALVE OFF. COMBUSTION AIR INDUCER OFF.
INDOOR BLOWER OFF WITH DELAY.
IS 5‐MINUTE RESET PERIOD COMPLETE?
LED: 1 FLASH
INDOOR BLOWER ON
LED: 4 FLASHES
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.)
LED: 3 FLASHES
YES
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HEATING SEQUENCE CONTINUED
NORMAL HEATING MODEABNORMAL HEATING MODE
15‐SECOND COMBUSTION AIR INDUCER PREPURGE
INITIATED BY CLOSED PRESSURE SWITCH.
YES
IGNITOR WARM‐UP -- 20 SECONDS.
YES
4‐SECOND TRIAL FOR IGNITION.
GAS VALVE OPENS.
YES
FLAME STABILIZATION PERIOD.
4 SECONDS
FLAME RECTIFICATION CURRENT
CHECK. CAN FLAME BE PROVEN WITHIN
4 SECONDS AFTER GAS VALVE OPENS?
YES
FLAME PRESENT?
YES
NO
IS VOLTAGE ABOVE 90 VOLTS?
YES
GAS VALVE OFF. COMBUSTION AIR INDUCER ON.
NO
HAS CONTROL FAILED TO SENSE FLAME FOR
FIVE CONSECUTIVE TRIES DURING A SINGLE
WATCHGUARD MODE. GAS VALVE OFF.
LED: 7 FLASHES WATCHGUARD FAILURE CODE.
IS 60‐MINUTE RESET PERIOD COMPLETE?
NO
INDOOR BLOWER OFF.
HEAT DEMAND?
COMBUSTION AIR INDUCER OFF.
INDOOR BLOWER OFF WITH DELAY
HAS CONTROL RESET IGNITION
SEQUENCE FOUR TIMES?
NO
LED: ON STEADY
UNTIL VOLTAGE IS
ABOVE 95 VOLTS,
THEN RESTARTS
HEATING
SEQUENCE.
NO
YES
YES
NO
FLAME SIGNAL 1.5 MICROAMPS OR GREATER?
YES
INDOOR BLOWER ON
AFTER 30-SECOND DELAY
YES
PRIMARY AND SECONDARY LIMIT
SWITCHES CLOSED?
YES
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
COMBUSTION AIR INDUCER DE-ENERGIZED.
INDOOR BLOWER ON UNTIL SWITCH CLOSES.
NO
NO
NO
NO
LOW FLAME SIGNAL
(Does not affect operation of control)
LED: ON STEADY
GAS VALVE DE-ENERGIZED.
LED: 4 FLASHES
IS LIMIT SWITCH CLOSED?
NO
5 MINUTE WATCHGUARD MODE.
HAS LIMIT SWITCHED CLOSED
AFTER 5 MINUTES?
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.
YES
YES
YES
WATCHGUARD
1 HR
PRESSURE
SWITCH
MODE
Page 50
Page 51
COOLING SEQUENCE OF OPERATION
NORMAL COOLING MODEABNORMAL COOLING MODE
POWER ON
IGNITION CONTROL MAIN POWER ON. LED: ON STEADY
CONTROL SELF DIAGNOSTIC CHECK.
IS CONTROL OPERATING NORMALLY?
YES
IS THERE A PROPER GROUND?
YES
IS POLARITY CORRECT?
YES
NO
IS VOLTAGE
ABOVE 90 VOLTS?
YES
NO
GAS VALVE OFF. COMBUSTION AIR INDUCER OFF.
INDOOR BLOWER OFF WITH NORMAL DELAY.
INTERRUPT MAIN POWER TO RESET CONTROL.
NO
CONTROL WILL CONTINUE TO CALL FOR COOLING
NO
CONTROL WILL CONTINUE TO CALL FOR COOLING
CONTROL WILL CONTINUE TO CALL FOR
COOLING IN THIS CONDITION.
LED: OFF
LED: ON STEADY
IN THIS CONDITION.
LED: 9 FLASHES
IN THIS CONDITION.
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.
SYSTEM FAN AND EAC TERM. OFF
LED: ON STEADY.
THERMOSTAT OPENS.
COMPRESSOR OFF.
WITH 60‐SECOND DELAY.
CONTINUOUS FAN SEQUENCE OF OPERATION
MANUAL FAN SELECTION MADE AT THERMOSTAT.
CONTROL (G) ENERGIZES SYSTEM FAN ON CONTINUOUS
BLOWER SPEED. EAC TERMINAL IS ENERGIZED.
THERMOSTAT CALLS FOR HEAT (W).
NO
THERMOSTAT CALLS FOR COOLING.
YES
SYSTEM FAN SWITCHED TO COOL SPEED.
EAC TERM. REMAINS ON.
LED: ON STEADY
NO
HUM TERM. ENERGIZES
WITH COMB. AIR INDUCER.
YES
SYSTEM FAN SWITCHES TO
HEATING SPEED.
THERMOSTAT OPENS.
THERMOSTAT OPENS.
MANUAL FAN SELECTION MADE AT THERMOSTAT.
CONTROL (G) ENERGIZES SYSTEM FAN ON
CONTINUOUS BLOWER SPEED.
HUM TERM. DE-ENERGIZES
WITH COMB. AIR INDUCER
SYSTEM FAN SWITCHES TO
CONTINUOUS BLOWER SPEED
.
Page 51
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