Lennox 070XP36B, 045XP36B, 110XP48C, 110XP60C, 135XP60D Unit Information
...
Corp. 1035-L7
Service Literature
Revised 03-2014
ML195UH SERIES UNITS
ML195UH series units are high-efficiency gas furnaces
manufactured with Lennox DuralokPlust aluminized steel
clamshell-type heat exchangers, with a stainless steel con
densing coil. ML195UH units are available in heating input
capacities of 44,000 to 132,000 Btuh (13 to 38.6 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 ML195UH
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.
ML195UH
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
Specifications 2.................................
Optional Accessories 3..........................
Blower Performance Data 4......................
I-Unit Components 7............................
II Placement and Installation 20....................
III-Start-Up 45...................................
IV-Heating System Service Checks 46..............
V-Typical Operating Conditions 48.................
VI-Maintenance 49...............................
VII-Sequence of Operation 52.....................
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.
Page 1
© 2014 Lennox Industries Inc.
Litho U.S.A.
SPECIFICATIONS
Gas
Heating
Performance
Temperature rise range - °F 40 - 70 25 - 55 40 - 70 50 - 80
Gas Manifold Pressure (in. w.g.)
Nat. Gas / LPG/Propane
High static - in. w.g. 0.5 0.5 0.5 0.5
Connections
in.
Intake / Exhaust Pipe (PVC) 2 / 2 2 / 2 2 / 2 2 / 2
Gas pipe size IPS 1/2 1/2 1/2 1/2
Condensate Drain Trap (PVC pipe) - i.d. 1/2 1/2 1/2 1/2
with furnished 90° street elbow 1/2 slip x 1/2 Mipt 1/2 slip x 1/2 Mipt 1/2 slip x 1/2 Mipt 1/2 slip x 1/2 Mipt
with eld supplied (PVC coupling) - o.d. 3/4 3/4 3/4 3/4
Indoor
Wheel nom. dia. x width - in. 10 x 8 10 x 8 10 x 8 10 x 8
Blower
Tons of add-on cooling 2.5 - 3 2 - 3 2.5 - 3 2 - 3
Air Volume Range - cfm 390 - 1140 700 - 1605 650 - 1585 655 - 1630
Electrical
Data
Blower motor full load amps 3.1 6.1 6.1 6.1
Maximum overcurrent protection 12 12 12 12
Shipping Data lbs. - 1 package 119 121 129 144
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.
Model No. ML195UH
045XP24B
1
AFUE 95% 95% 95% 95%
ML195UH
045XP36B
ML195UH
070XP36B
ML195UH
090XP36C
Input - Btuh 44,000 44,000 66,000 88,000
Output - Btuh 41,000 42,000 64,000 85,000
3.5 / 10.0 3.5 / 10.0 3.5 / 10.0 3.5 / 10.0
Motor output - hp 1/3 1/3 1/3 1/3
Voltage 120 volts - 60 hertz - 1 phase
SPECIFICATIONS
Gas
Heating
Performance
Temperature rise range - °F 40 - 70 50 - 80 40 - 70 45 - 75
Gas Manifold Pressure (in. w.g.)
Nat. Gas / LPG/Propane
High static - in. w.g. 0.5 0.5 0.5 0.5
Connections
in.
Intake / Exhaust Pipe (PVC) 2 / 2 2 / 2 2 / 2 2 / 2
Gas pipe size IPS 1/2 1/2 1/2 1/2
Condensate Drain Trap (PVC pipe) - i.d. 1/2 1/2 1/2 1/2
with furnished 90° street elbow 1/2 slip x 1/2 Mipt 1/2 slip x 1/2 Mipt 1/2 slip x 1/2 Mipt 1/2 slip x 1/2 Mipt
with eld supplied (PVC coupling) - o.d. 3/4 3/4 1 1
Indoor
Wheel nom. dia. x width - in. 10 x 10 10 x 10 11-1/2 x 10 11-1/2 x 10
Blower
Tons of add-on cooling 3 - 4 3 - 4 4 - 5 4 - 5
Air Volume Range - cfm 900 - 2140 715 - 2000 1250 - 2485 1145 - 2595
Electrical
Data
Blower motor full load amps 8.2 8.2 11.5 11.5
Maximum overcurrent protection 12 12 15 15
Shipping Data lbs. - 1 package 149 159 164 177
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.
Model No. ML195UH
090XP48C
1
AFUE 95% 95% 95% 95%
ML195UH
110XP48C
ML195UH
110XP60C
Input - Btuh 88,000 110,000 110,000 132,000
Output - Btuh 85,000 105,000 106,000 126,000
3.5 / 10.0 3.5 / 10.0 3.5 / 10.0 3.5 / 10.0
Motor output - hp 1/2 1/2 1 1
Voltage 120 volts - 60 hertz - 1 phase
Page 2
ML195UH
135XP60D
OPTIONAL ACCESSORIES - MUST BE ORDERED EXTRA
“B” Width Models “C” Width Models “D” Width Models
CABINET ACCESSORIES
Horizontal Suspension Kit - Horizontal only 51W10 51W10 51W10
Return Air Base - Upow only 50W98 50W99 51W00
CONDENSATE DRAIN KITS
Condensate Drain Heat Cable 6 ft. 26K68 26K68 26K68
24 ft. 26K69 26K69 26K69
50 ft. 26K70 26K70 26K70
Heat Cable Tape Fiberglass - 1/2 in. x 66 ft. 36G53 36G53 36G53
Aluminum foil - 2 in. x 60 ft. 16P89 16P89 16P89
Crawl Space Vent Drain Kit 51W18 51W18 51W18
FILTER KITS
1
Air Filter and
Rack Kit
NIGHT SERVICE KIT
Night Service Kit 51W03 51W03 51W03
Safety Service Kit 89W20 89W20 89W20
TERMINATION KITS
See Installation Instructions for specic venting information.
Termination Kits Direct Vent
Applications Only
Termination Kits Direct or NonDirect vent
2
Roof Termination Flashing Kit - Direct or Non-
Direct Vent (2 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.
Horizontal (end) Size of lter - in. 87L96 - 18 x 25 x 1 87L97 - 20 x 25 x 1 87L98 - 25 x 25 x 1
Side Return Single 44J22 44J22 44J22
Ten Pack 66K63 66K63 66K63
Size of lter - in. 16 x 25 x 1 16 x 25 x 1 16 x 25 x 1
Concentric US - 2 in. 71M80 69M29 - - -
3 in. - - - 60L46 60L46
Canada - 2 in. 44W92 44W92 - - -
3 in. - - - 44W93 44W93
Flush-Mount 2, 2-1/2 or 3 in. 51W11 51W11 51W11
Wall - Close
Couple
Wall - Close
Couple WTK
US - 2 in. 22G44 - - - - - -
3 in. 44J40 44J40 44J40
Canada - 2 in. 30G28 - - - - - -
3 in. 81J20 81J20 81J20
Roof 2 in. 15F75 15F75 - - -
Wall Ring Kit 2 in. 15F74
3
15F74 - - -
2 in. 44J41 44J41 44J41
GAS HEAT ACCESSORIES
High Altitude
Input
045 No Change 80W60 69W73 73W81 73W37 68W68
070 80W66 80W59 69W73 73W81 73W37 68W68
090 80W65 80W59 69W73 73W81 73W37 68W68
110 80W66 80W59 69W73 73W81 73W37 68W68
135 80W65 80W59 69W73 73W81 73W37 68W68
Pressure Switch Kit
4501 - 7500 ft. 7501 - 10,000 ft. 0 - 7500 ft. 0 - 7500 ft. 7501- 10,000 ft. 7501- 10,000 ft.
Natural Gas to
LPG/Propane Kit
Page 3
LPG/Propane
to Natural Gas Kit
Natural Gas
High Altitude
Orice Kit
LPG/Propane
High Altitude
Orice Kit
BLOWER DATA
ML195UH045XP24B PERFORMANCE (Less Filter)
External
Static
Pressure
in. w.g.
0.00 1140 455 920 365 765 295 710 265
0.10 1135 445 900 360 765 290 690 255
0.20 1125 430 895 350 755 285 680 255
0.30 1090 415 870 340 725 280 660 250
0.40 1065 405 870 325 715 270 635 245
0.50 1020 390 825 315 675 260 605 235
0.60 945 365 780 300 640 250 555 225
0.70 910 350 740 295 585 240 505 220
0.80 790 325 670 275 510 225 455 205
0.90 735 310 575 255 460 220 390 195
ML195UH045XP36B PERFORMANCE (Less Filter)
External
Static
Pressure
in. w.g.
0.00 1605 700 1370 590 1160 475 1010 400
0.10 1600 680 1355 565 1155 465 1015 390
0.20 1550 645 1330 540 1150 445 1000 380
0.30 1480 620 1295 520 1140 430 975 365
0.40 1425 590 1280 490 1105 415 975 345
0.50 1355 565 1190 460 1085 395 940 335
0.60 1320 545 1165 435 1030 380 900 315
0.70 1225 500 1110 425 980 355 855 310
0.80 1135 480 1050 395 920 330 780 280
0.90 1025 445 950 360 795 295 700 255
Air Volume / Watts at Various Blower Speeds
High
cfm Watts cfm Watts cfm Watts cfm Watts
Air Volume / Watts at Various Blower Speeds
High
cfm Watts cfm Watts cfm Watts cfm Watts
Medium-
High
Medium-
High
Medium-Low Low
Medium-Low Low
ML195UH090XP36C PERFORMANCE (Less Filter)
External
Static
Pressure
in. w.g.
0.00 1630 715 1345 590 1090 475 885 385
0.10 1615 700 1320 580 1070 465 890 380
0.20 1580 675 1305 570 1070 455 890 370
0.30 1525 620 1295 535 1060 435 890 360
0.40 1480 615 1275 515 1055 430 885 350
0.50 1415 565 1220 485 1030 410 860 330
0.60 1350 535 1175 450 1005 390 835 310
0.70 1260 505 1115 415 955 360 785 290
0.80 1190 480 1010 380 880 325 740 285
0.90 1060 435 930 360 795 295 655 250
ML195UH090XP48C PERFORMANCE (Less Filter)
External
Static
Pressure
in. w.g.
0.00 2140 880 1895 780 1590 645 1350 550
0.10 2110 850 1880 760 1585 635 1360 545
0.20 2060 810 1840 725 1580 620 1360 520
0.30 1990 765 1805 690 1550 585 1365 500
0.40 1925 750 1755 655 1510 545 1330 470
0.50 1830 700 1675 610 1460 525 1285 450
0.60 1720 645 1610 575 1390 480 1230 415
0.70 1600 615 1520 535 1300 465 1165 390
0.80 1455 560 1410 500 1200 430 1035 365
0.90 1300 515 1305 465 1100 390 901 320
Air Volume / Watts at Various Blower Speeds
High
cfm Watts cfm Watts cfm Watts cfm Watts
Air Volume / Watts at Various Blower Speeds
High
cfm Watts cfm Watts cfm Watts cfm Watts
Medium-
High
Medium-
High
Medium-Low Low
Medium-Low Low
ML195UH070XP36B PERFORMANCE (Less Filter)
External
Static
Pressure
in. w.g.
0.00 1585 685 1340 585 1095 480 880 380
0.10 1560 665 1320 565 1085 470 885 375
0.20 1515 630 1300 540 1080 460 880 370
0.30 1465 590 1275 520 1065 440 890 360
0.40 1410 570 1235 490 1050 420 875 350
0.50 1345 540 1195 470 1020 400 840 335
0.60 1275 510 1140 440 975 365 830 315
0.70 1195 485 1090 410 930 355 780 290
0.80 1105 460 995 380 850 325 730 275
0.90 985 420 890 345 770 300 650 255
Air Volume / Watts at Various Blower Speeds
High
cfm Watts cfm Watts cfm Watts cfm Watts
Medium-
High
Medium-Low Low
Page 4
ML195UH110XP48C PERFORMANCE (Less Filter)
External
Static
Pressure
in. w.g.
0.00 2000 910 1675 765 1360 635 1185 525
0.10 1980 895 1650 745 1370 610 1180 505
0.20 1935 855 1600 710 1400 590 1170 485
0.30 1875 830 1560 680 1370 570 1160 490
0.40 1800 785 1490 655 1325 545 1120 455
0.50 1725 720 1400 610 1295 515 1080 435
0.60 1630 685 1335 585 1185 480 1030 410
0.70 1530 665 1290 525 1100 435 940 385
0.80 1410 610 1190 485 985 400 790 365
0.90 1245 560 1000 430 925 380 715 315
Air Volume / Watts at Various Blower Speeds
High
cfm Watts cfm Watts cfm Watts cfm Watts
Medium-
High
Medium-Low Low
BLOWER DATA
ML195UH110XP60C PERFORMANCE (Less Filter)
Air Volume / Watts at Different Blower Speeds
External
Static
Pressure
in. w.g.
0.00 2485 1515 2090 1070 1835 865 1380 660 2400 1475 2100 1075 1755 870 1320 655
0.10 2460 1475 2075 1040 1810 835 1390 650 2370 1440 2090 1060 1735 850 1330 645
0.20 2405 1445 2040 995 1790 820 1405 650 2320 1405 2060 1050 1720 835 1340 650
0.30 2335 1375 1990 980 1760 790 1460 635 2235 1350 2040 1030 1725 825 1350 645
0.40 2215 1355 1935 940 1740 775 1410 630 2165 1330 1975 970 1700 815 1330 632
0.50 2185 1310 1865 895 1680 750 1410 625 2040
0.60 2060 1270 1805 870 1630 720 1405 610 1960 1260 1845 910 1635 770 1340 620
0.70 1945 1235 1700 840 1605 700 1380 590 1865 1215 1750 890 1575 730 1295 600
0.80 1845 1210 1605 810 1505 670 1305 570 1715 1175 1590 840 1505 710 1280 590
0.90 1730 1150 1570 790 1470 660 1250 540 1630 1135 1490 685 1460 685 1235 565
ML195UH135XP60D PERFORMANCE (Less Filter)
External
Static
Pressure
in. w.g.
0.00 2595 1515 2245 2015 1780 890 1365 700 2540 1500 2185 1095 1715 880 1350 700
0.10 2570 1490 2235 1095 1765 875 1370 665 2525 1480 2165 1085 1725 870 1335 675
0.20 2440 1465 2135 1075 1745 865 1395 660 2440 1445 2120 1090 1725 865 1345 675
0.30 2340 1405 2075 1060 1755 845 1365 660 2345 1400 2060 1060 1715 850 1345 670
0.40 2255 1370 1995 1005 1680 825 1370 660 2220 1345 1955 1015 1685 820 1370 660
0.50 2095 1320 1915 960 1650 805 1335 650 2100
0.60 1995 1270 1840 935 1595 775 1320 630 2005 1285 1780 945 1605 790 1285 635
0.70 1900 1225 1755 905 1540 755 1270 615 1845 1235 1700 910 1510 740 1225 610
0.80 1740 1180 1650 875 1430 725 1190 590 1745 1185 1645 880 1450 720 1175 595
0.90 1580 1140 1535 840 1350 695 1145 570 1655 1160 1545 840 1380 705 1135 575
Bottom Return Air, Side Return Air with Optional Return Air
Base, Return Air from Both Sides or Return Air from Bottom
and One Side.
High Medium-High Medium-Low Low High Medium-High Medium-Low Low
cfm Watts cfm Watts cfm Watts cfm Watts cfm Watts cfm Watts cfm Watts cfm Watts
Air Volume / Watts at Different Blower Speeds
Bottom Return Air, Side Return Air with Optional Return Air
Base, Return Air from Both Sides or Return Air from Bottom
and One Side.
High Medium-High Medium-Low Low High Medium-High Medium-Low Low
cfm Watts cfm Watts cfm Watts cfm Watts cfm Watts cfm Watts cfm Watts cfm Watts
Single Side Return Air − Air volumes in bold require eld
fabricated transition to accommodate 20 x 25 x 1 in. air lter
in order to maintain proper air velocity.
1290 1920 945 1700 790 1325 620
Single Side Return Air − Air volumes in bold require eld
fabricated transition to accommodate 20 x 25 x 1 in. air lter
in order to maintain proper air velocity.
1310 1895 985 1620 805 1320 650
Page 5
MANIFOLD
GAS VALVE
COMBUSTION AIR
INDUCER
BURNER
ACCESS
PANEL
ROLLOUT
SWITCHES
ML195UH PARTS IDENTIFICATION
FLEXIBLE NO-HUB
EXHAUST COLLAR
BURNER BOX
ASSEMBLY
DuralokPlus
HEAT EXCHANGER
ASSEMBLY
TOP CAP
TM
SIGHT
GLASS
BLOWER
ACCESS
DOOR
COMBUSTION
AIR PRESSURE
SWITCH
COLD END
HEADER BOX
PRIMARY LIMIT
BLOWER
ASSEMBLY
CONTROL BOX
(includes integrated control, transformer and interlock switch)
FIGURE 1
CABINET
BAG ASSEMBLIES
(shipping location)
Page 6
I-UNIT COMPONENTS
ML195UH 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.
ML195UH Control Box
TRANSFORMER
(T1)
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 flame sensor (figure
10). The integrated control and ignitor work in combination
to ensure furnace ignition and ignitor durability. The inte
grated control, controls all major furnace operations. The
integrated control also features two LED lights (DS1 red
and DS2 green) for troubleshooting and two accessory ter
minals rated at (1) one amp. The integrated control also
features 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.
INTEGRATED IGNITION
CONTROL
(A92)
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
1 Combustion Air Inducer Line
2
3
4
Ignitor Line
Combustion Air Inducer Neutral
Ignitor Neutral
TABLE 2
12-Pin Terminal Designations
PIN # FUNCTION
1 High Limit Output
2 Not Used
3 24V Line
4 Not Used
5 Rollout Switch Out
6 24V Neutral
7 High Limit Input
8 Ground
9 Gas Valve Common
10 Pressure Switch In
11 Rollout Switch In
12 Gas Valve Out
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 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 at 19 sec
onds for a 4-second trial for ignition. The ignitor remains
energized for the first 3 seconds during the 4 second trial. If
ignition is not proved during the 4-second period, the inte
grated control will try four more times with an inter purge
and warm-up time between trials of 35 seconds. After a to
tal of five trials for ignition (including the initial trial), the inte
grated control goes into Watchguard-Flame Failure mode.
After a 60-minute reset period, the integrated control will
begin the ignition sequence again.
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 8
The integrated control is equipped with two LED lights for troubleshooting. The diagnostic codes are listed below in table 3.
ЙЙЙЙЙЙЙЙЙ
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 FLASH ON
OFF SLOW FLASH
ALTERNATING
SLOW FLASH
SLOW FLASH OFF Flame sensed without gas valve energized.
ON SLOW FLASH Rollout switch open. OR: 12‐pin connector improperly attached.
SIMULTANEOUS
SLOW FLASH
SIMULTANEOUS
FAST FLASH
ALTERNATING
SLOW FLASH
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 board failure or control wired incorrectly.
FAST FLASH SLOW FLASH Main power polarity reversed. Switch line and neutral.
SLOW FLASH FAST FLASH Low flame signal. Measures below 1.5 microamps. Replace flame sense rod.
ALTERNATING
FAST FLASH
ALTERNATING
FAST FLASH
Improper main ground.
OR: Line voltage below 90 volts.
NOTE - Slow flash rate equals 1 Hz (one flash per second). Fast flash rate equals 3 Hz (three flashes per second).
Minimum flame sense current = 0.5 microAmps.
*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 30 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 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 120V ig
nitor 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 4 second 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 (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.
TABLE 4
4-Pin Terminal Designation
PIN # FUNCTION
1 Combustion Air Inducer Line
2
3
4
Ignitor Line
Combustion Air Inducer Neutral
Ignitor Neutral
TABLE 5
12-Pin Terminal Designations
PIN # FUNCTION
1 High Limit Output
2 Sensor
3 24V Line
4 Not Used
5 Rollout Switch Out
6 24V Neutral
7 High Limit Input
8 Ground
9 Gas Valve Common
10 Pressure Switch In
11 Rollout Switch In
12 Gas Valve Out
TABLE 6
DIAGNOSTIC CODES
LED Status DESCRIPTION
LED Off
LED On Normal operation.
1 Flash
2 Flashes
3 Flashes
4 Flashes Primary limit switch open.
5 Flashes Rollout switch open.
6 Flashes Pressure switch cycle lockout.
7 Flashes Lockout, burners fail to light.
8 Flashes
9 Flashes Line voltage polarity incorrect.
Note - This control is equipped with a push button switch for
diagnostic code recall. The control stores the last 5 fault
codes in non-volatile memory. The most recent fault code
is flashed first, the oldest fault code is flashed last. There is
a 2 second pause between codes. When the push button
switch is pressed for less than 5 seconds, the control will
flash the stored fault codes when the switch is released.
The fault code history may be cleared by pressing the push
button switch for more than 5 seconds.
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 10
LED
ЙЙЙЙЙЙЙЙЙЙЙЙЙЙЙЙЙЙЙЙЙЙЙЙ
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 -Purge Ignitor Warm-up
15
FIGURE 6
ELECTRONIC IGNITION
351
Trial for
Ignition
FIGURE 7
39
Blower “On”*
Delay
5 SEC69
Post
Purge
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 ML195UH 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
off Time
60
90
120
180
FIGURE 8
180 Second
off Time
60
90
120
180
Page 12
TWO-STAGE THERMOSTAT
FIELD WIRING FOR TWINNING THE ML195UH
TWIN
SINGLE STAGE THERMOSTAT
TWIN
Call For Cool
Call For Fan
Call For 1st
Stage Heat
Call For 2nd
StageHeat
R
Y
G
W1
W2
ISOLATION
RELAY
TWIN
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
C
TWIN
R
TWIN 1
Y
G
W
C
R
TWIN 2
Y
G
W
C
FRONT BURNER BOX PLATE
ROLLOUT SWITCHES
FLAME SENSOR
FIGURE 9
ML195UH Burner Box Assembly
BURNERS
IGNITOR
ORIFICES
GAS VALVE
FIGURE 10
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. Flame Rollout Switches (Figure 10)
Burner Detail Top View
IGNITOR
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 ML195UH units is
factory preset to open at 210_F +
12_F (99_C + 6.7_C) on a
temperature rise. All flame rollout switches are manual re
set.
2. Primary Limit Control (Figure 12)
Primary limit (S10) used on ML195UH 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, remove mounting screws,
rotate limit switch 90 degrees and slowly remove from the
vestibule panel. Install replacement limit with same care.
3. Burners (Figure 11)
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
burner input. See table 7 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.
FLAME SENSOR
ORIFICES
FIGURE 11
4. Heat Exchanger (Figure 12)
ML195UH 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.
Primary Limit Location and Heat Exchanger
TABLE 7
Gas Orifice Size
Unit Fuel Orifice Size
All Natural 0.063
All L.P./Propane 0.0340
Install limit face down
FIGURE 12
5. Gas Valve (GV1)
The ML195UH uses an internally redundant valve to as
sure safety shut‐off. If the gas valve must be replaced, the
same type valve must be used.
Page 14
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
INLET
PRESSURE
PORT
Gas Valve
MANIFOLD
PRESSURE
OUTLET
PORT
FIGURE 13
6. Flame Sensor (Figure 10)
A flame sensor is located on the left side of the burner sup
port. The sensor is mounted on the front burner box plate
and the tip protrudes into the flame envelope of the 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 ML195UH furnace contains electronic
components that are polarity sensitive. Make sure that
the furnace is wired correctly and is properly grounded.
A microamp DC meter is needed to check the flame signal
on the integrated control.
Flame (microamp) signal is an electrical current which
passes from the integrated control to the sensor during unit
operation. Current passes from the sensor through the
flame to ground to complete a safety circuit.
To Measure Flame Signal - Integrated Control:
Use a digital readout meter capable of reading DC micro
amps. See figure 14 for flame signal check.
1 - Set the meter to the DC amps scale.
2 - Turn off supply voltage to control.
3 - Disconnect integrated control flame sensor wire from
the flame sensor.
4 - Connect (-) lead to flame sensor.
5 - Connect (+) lead 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.
7. Ignitor (Figure 10)
ML195UH 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 15 and table
8 for resistance and voltage checks.
Page 15
Flame Signal In Microamps
Normal Low Drop Out
1.5
0.5 - 1.4
0.4
Measuring Flame Signal
Flame Sensor
Wire
Remove sensor wire from
integrated control and
connect alligator clip(-) to
flame sensor lead.
Intergrated
Control
Multi−Meter
Set Dial to Ohms
Flame Sensor
Terminal
(+)
(+)
To Flame
Terminal
(+) To Control
Sensor Terminal
Remove sensor wire from
integrated control and
connect alligator clip(+) to
terminal on control.
FIGURE 14
Page 16
Check ignitor circuit for correct resistance.
Test 1
Remove 4-pin plug from control.
Check ohms reading across terminals 2 and 4.
See table 8. 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 1
IGNITOR CHECKS
TABLE 8
Control Ohms
103085
100973
39 to 70
24 to 47
Voltage +
120
95
10%
Check ignitor for correct resistance.
Test 2
Seperate the 2-pin jack-plug near the manifold and check
resistance of ignitor at the plug. See table 8. If the reading
is correct, then the problem is with the wiring between the
jack-plug and the control. If reading is not correct, the
issue is the ignitor.
Test 2
Multi−Meter
(set to ohms)
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 8. If voltage reads below these values, check for
correct supply voltage to furnace.
Integrated Control Detail
Integrated Control Detail
Multi−Meter
(set to VAC)
Test 3
Integrated Control Detail
FIGURE 15
Page 17
8. Combustion Air Inducer (B6)
& Cold End Header Box
All ML195UH units use a combustion air inducer to move
air through the burners and heat exchanger during heating
operation. The blower uses a shaded pole 120VAC motor.
The motor operates during all heating operation and is con
trolled by integrated control A3. Blower operates continu
ously while there is a call for heat. The integrated control
will not proceed with the ignition sequence until combus
tion air inducer operation is sensed by the proving
switches.
The combustion air inducer is installed on the cold end
header box. The cold end header box is a single piece
made of hard plastic. The box has an internal channel
where the combustion air inducer creates negative pres
sure at unit start up. The channel contains an orifice used to
regulate flow created by the combustion air inducer. The
box has pressure taps for the combustion air inducer pres
sure switch hoses. The pressure switch measures the
pressure across the combustion air inducer orifice or differ
ence in the channel and the box. If replacement is neces
sary the gaskets used to seal the box to the vestibule
panel and the combustion air inducer to the box, must
also be replaced.
TABLE 9
Unit
-045 0.618”
-070 0.810”
-090 0.973”
-110 1.040”
-135 1.235”
Combustion Air Inducer
Orifice Size
9. Combustion Air Pressure Switch
(Figure 16)
ML195UH series units are equipped with a differential
pressure switch located on the cold end header box. The
switch monitors across the combustion air inducer orifice to
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.
Pressure Switch
FIGURE 16
On start‐up, the switch monitors whether the combustion
air inducer is operating. It closes a circuit to the integrated
control when the difference in pressure across the com
bustion air inducer orifice exceeds a non-adjustable factory
setting. If the switch does not successfully sense the re
quired differential, the switch cannot close and the furnace
cannot operate. If the flue or air inlet become obstructed
during operation, the switch senses a loss of pressure dif
ferential and opens the circuit to the integrated control. If
the condensate line is blocked, water will back up into the
header box and reduce the pressure differential across the
switch. The prove switch opens if the differential drops be
low 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 17. 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.
Unit
-045 -0.65 -0.65 -0.60
-070 -0.90 -0.85 -0.65
-090 -0.90 -0.80 -0.65
-110 -0.90 -0.85 -0.65
-135 -0.90 -0.80 -0.65
*Set point is factory set and non-adjustable
0 - 4500 4501 - 7500 7501 - 10000
Set Point
“w.c.
Set Point “w.c
Set Point
“w.c.
Page 18
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