Lennox ML296UHV(X), ML296UH045XV36B, ML296UH070XV36B Series Manual
Corp. 1903-L1
Service Literature
ML296UHV(X) SERIES UNITS
ML296UHV(X) series units are 90% efficiency gas fur
naces used for upflow or horizontal applications only,
manufactured with Lennox Duralokt heat exchangers
formed of aluminized steel. ML296UHV(X) units are avail
able in heating capacities of 44,000 to 132,000 Btuh and
cooling applications up to 5 tons. Refer to Engineering
Handbook for proper sizing.
Units are factory equipped for use with natural gas. Kits are
available for conversion to LPG operation. ML296UHV(X)
unit meets the California Nitrogen Oxides (NO
and California Seasonal Efficiency requirements. All units
use a redundant gas valve to assure safety shut-off as re
quired by C.S.A.
All specifications in this manual are subject to change. Pro
cedures outlined in this manual are presented as a recom
mendation only and do not supersede or replace local or
state codes. In the absence of local or state codes, the
guidelines and procedures outlined in this manual (except
where noted) are recommendations only and do not consti
tute code.
TABLE OF CONTENTS
Specifications Page 2.............................
Blower Data Page 3..............................
I Unit Components Page 9........................
II Installation Page 21.............................
III Start Up Page 43..............................
IV Heating System Service Checks Page 44.........
V Typical Operating Characteristics Page 47.........
VI Maintenance Page 47..........................
VII Wiring and Sequence of Operation Page 50......
) Standards
x
ML296UHV(X)
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.
CAUTION
As with any mechanical equipment, contact with
sharp sheet metal edges can result in personal in
jury. Take care while handling this equipment and
wear gloves and protective clothing.
Page 1
© 2019 Lennox Industries Inc.
SPECIFICATIONS
Gas
Heating
AHRI Reference No. N/A N/A
Performance
High
Fire
Temperature rise range - °F 35 - 65 50 - 80
Gas Manifold Pressure (in. w.g.)
Nat. Gas / LPG/Propane
Low
Fire
Temperature rise range - °F 20 - 50 25 - 55
Gas Manifold Pressure (in. w.g.)
Nat. Gas / LPG/Propane
High static - in. w.g. Heating 0.8 0.8
Connections
Intake / Exhaust Pipe (PVC) 2 / 2 2 / 2
in.
Condensate Drain Trap (PVC pipe) - i.d. 3/4 3/4
with furnished 90° street elbow 3/4 slip x 3/4 Mipt 3/4 slip x 3/4 Mipt
with eld supplied (PVC coupling) - o.d. 3/4 slip x 3/4 MPT 3/4 slip x 3/4 MPT
Indoor
Wheel nominal diameter x width - in. 10 x 9 10 x 9
Blower
Tons of add-on cooling 2 - 3 2 - 3
Air Volume Range - cfm 485 - 1370 500 - 1365
Electrical Data Voltage 120 volts - 60 hertz - 1 phase
Blower motor full load amps 7.7 7.7
Maximum overcurrent protection 15 15
Shipping Data lbs. - 1 package 130 138
NOTE - Filters and provisions for mounting are not furnished and must be eld provided.
1
Annual Fuel Utilization Eciency based on DOE test procedures and according to FTC labeling regulations. Isolated combustion system rating for non-weatherized furnaces.
Model No. ML296UH045XV36B ML296UH070XV36B
1
AFUE 96% 96%
Input - Btuh 44,000 66,000
Output - Btuh 42,000 62,000
3.5 / 10.0 3.5 / 10.0
Input - Btuh 29,000 43,000
Output - Btuh 28,000 41,000
1.7 / 4.9 1.7 / 4.9
Cooling 1.0 1.0
Gas pipe size IPS 1/2 1/2
Motor output - hp 1/2 1/2
Gas
Heating
Performance
AHRI Reference No. N/A N/A
High
Fire
Model No. ML296UH090XV48C ML296UH110XV60C
1
AFUE 96% 96%
Input - Btuh 88,000 110,000
Output - Btuh 84,000 106,000
Temperature rise range - °F 45 - 75 45 - 75
Gas Manifold Pressure (in. w.g.)
3.5 / 10.0 3.5 / 10.0
Nat. Gas / LPG/Propane
Low
Fire
Input - Btuh 57,000 72,000
Output - Btuh 55,000 70,000
Temperature rise range - °F 30 - 60 35 - 65
Gas Manifold Pressure (in. w.g.)
1.7 / 4.9 1.7 / 4.9
Nat. Gas / LPG/Propane
High static - in. w.g. Heating 0.8 0.8
Cooling 1.0 1.0
Connections
in.
Intake / Exhaust Pipe (PVC) 2 / 2 2 / 2
Gas pipe size IPS 1/2 1/2
Condensate Drain Trap (PVC pipe) - i.d. 3/4 3/4
with furnished 90° street elbow 3/4 slip x 3/4 Mipt
3/4 slip x 3/4 Mipt
with eld supplied (PVC coupling) - o.d. 3/4 slip x 3/4 MPT 3/4 slip x 3/4 MPT
Indoor
Blower
Wheel nominal diameter x width - in. 11 x 11 11 x 11
Motor output - hp 3/4 1
Tons of add-on cooling 2.5 - 4 3 - 5
Air Volume Range - cfm 680 - 1770 790 - 1955
Electrical Data Voltage 120 volts - 60 hertz - 1 phase
Blower motor full load amps 10.1 12.8
Maximum overcurrent protection 15 20
Shipping Data lbs. - 1 package 163 174
NOTE - Filters and provisions for mounting are not furnished and must be eld provided.
1
Annual Fuel Utilization Eciency based on DOE test procedures and according to FTC labeling regulations. Isolated combustion system rating for non-weatherized furnaces.
Page 2
BLOWER DATA
ML296UH045XV36B BLOWER PERFORMANCE (less lter)
BOTTOM RETURN AIR
0 through 0.8 in. w.g. (Heating) and 0 through 1.0 in. w.g. (Cooling) External Static Pressure Range
“ADJUST”
Switch
Positions
Second Stage “HEAT” Speed - cfm Second Stage “COOL” Speed - cfm
1
D
C B A D C B
+ 745 875 990 1005 905 1075 1210 1370
1
NORM 685 765 895 910 815 980 1120 1255
— 610 695 785 810 720 885 1020 1135
“ADJUST”
Switch
Positions
First Stage “HEAT” Speed - cfm First Stage “COOL” Speed - cfm
D
1
C B A D C B
+ 685 765 895 910 595 760 865 980
1
NORM 620 705 800 820 540 660 785 890
— 545 625 715 725 485 600 695 790
1
Factory default jumper setting.
NOTES - The eect of static pressure is included in air volumes shown.
First stage HEAT is approximately 91% of the same second stage HEAT speed position.
First stage COOL (two-stage air conditioning units only) is approximately 70% of the same second stage COOL speed
position. Continuous Fan Only speed is approximately 38% of the same second stage COOL speed position - minimum
500 cfm. Lennox Harmony III™ Zoning System Applications - Minimum blower speed is 453 cfm.
BLOWER DATA
ML296UH045XV36B BLOWER PERFORMANCE (less lter)
SINGLE SIDE RETURN AIR
0 through 0.8 in. w.g. (Heating) and 0 through 1.0 in. w.g. (Cooling) External Static Pressure Range
“ADJUST”
Switch
Positions
+ 780 880 990 1010 920 1065 1205 1340
1
NORM 705 795 905 925 815 985 111 0 1245
— 640 715 805 810 745 890 1020 1130
“ADJUST”
Switch
Positions
+ 705 795 905 925 610 760 845 975
1
NORM 645 725 810 815 550 680 770 880
— 570 655 735 750 465 610 720 775
1
Factory default jumper setting.
NOTES - The eect of static pressure is included in air volumes shown.
First stage HEAT is approximately 91% of the same second stage HEAT speed position.
First stage COOL (two-stage air conditioning units only) is approximately 70% of the same second stage COOL speed
position. Continuous Fan Only speed is approximately 38% of the same second stage COOL speed position - minimum
500 cfm. Lennox Harmony III™ Zoning System Applications - Minimum blower speed is 453 cfm.
Second Stage “HEAT” Speed - cfm Second Stage “COOL” Speed - cfm
1
D
C B A D C B
First Stage “HEAT” Speed - cfm First Stage “COOL” Speed - cfm
D
1
C B A D C B
Speed Switch Positions
Speed Switch Positions
1
A
1
A
1
A
1
A
Page 3
BLOWER DATA
ML296UH045XV36B BLOWER PERFORMANCE (less lter)
SINGLE SIDE RETURN AIR
0 through 0.8 in. w.g. (Heating) and 0 through 1.0 in. w.g. (Cooling) External Static Pressure Range
“ADJUST”
Switch
Positions
Second Stage “HEAT” Speed - cfm Second Stage “COOL” Speed - cfm
1
D
C B A D C B
Speed Switch Positions
+ 780 880 990 1010 920 1065 1205 1340
1
NORM 705 795 905 925 815 985 111 0 1245
— 640 715 805 810 745 890 1020 1130
“ADJUST”
Switch
Positions
First Stage “HEAT” Speed - cfm First Stage “COOL” Speed - cfm
D
1
C B A D C B
+ 705 795 905 925 610 760 845 975
1
NORM 645 725 810 815 550 680 770 880
— 570 655 735 750 465 610 720 775
1
Factory default jumper setting.
NOTES - The eect of static pressure is included in air volumes shown.
First stage HEAT is approximately 91% of the same second stage HEAT speed position.
First stage COOL (two-stage air conditioning units only) is approximately 70% of the same second stage COOL speed
position. Continuous Fan Only speed is approximately 38% of the same second stage COOL speed position - minimum
500 cfm. Lennox Harmony III™ Zoning System Applications - Minimum blower speed is 453 cfm.
BLOWER DATA
ML296UH070XV36B BLOWER PERFORMANCE (less lter)
BOTTOM RETURN AIR
0 through 0.8 in. w.g. (Heating) and 0 through 1.0 in. w.g. (Cooling) External Static Pressure Range
“ADJUST”
Switch
Positions
Second Stage “HEAT” Speed - cfm Second Stage “COOL” Speed - cfm
1
D
C B A D C B
+ 965 1130 1255 1400 860 1060 1215 1365
1
NORM 880 990 1140 1295 810 960 1130 1265
— 810 890 1030 1170 705 840 1005 1140
“ADJUST”
Switch
Positions
First Stage “HEAT” Speed - cfm First Stage “COOL” Speed - cfm
D
1
C B A D C B
+ 940 1070 1195 1345 600 740 840 970
1
NORM 830 965 1100 1235 555 665 770 855
— 755 840 975 1130 500 600 680 790
1
Factory default jumper setting.
NOTES - The eect of static pressure is included in air volumes shown.
First stage HEAT is approximately 91% of the same second stage HEAT speed position.
First stage COOL (two-stage air conditioning units only) is approximately 70% of the same second stage COOL speed
position. Continuous Fan Only speed is approximately 38% of the same second stage COOL speed position - minimum
500 cfm. Lennox Harmony III™ Zoning System Applications - Minimum blower speed is 453 cfm.
Speed Switch Positions
1
A
1
A
1
A
1
A
Page 4
BLOWER DATA
ML296UH070XV36B BLOWER PERFORMANCE (less lter)
SINGLE SIDE RETURN AIR
0 through 0.8 in. w.g. (Heating) and 0 through 1.0 in. w.g. (Cooling) External Static Pressure Range
“ADJUST”
Switch
Positions
Second Stage “HEAT” Speed - cfm Second Stage “COOL” Speed - cfm
1
D
C B A D C B
Speed Switch Positions
+ 980 1095 1225 1395 840 1050 1205 1355
1
NORM 855 1005 1120 1250 750 945 1130 1230
— 755 870 1020 1170 685 805 990 1110
“ADJUST”
Switch
Positions
First Stage “HEAT” Speed - cfm First Stage “COOL” Speed - cfm
D
1
C B A D C B
+ 920 1055 1205 1325 590 705 805 955
1
NORM 800 950 1075 1215 540 640 725 820
— 730 810 960 1095 500 580 665 720
1
Factory default jumper setting.
NOTES - The eect of static pressure is included in air volumes shown.
First stage HEAT is approximately 91% of the same second stage HEAT speed position.
First stage COOL (two-stage air conditioning units only) is approximately 70% of the same second stage COOL speed
position. Continuous Fan Only speed is approximately 38% of the same second stage COOL speed position - minimum
500 cfm. Lennox Harmony III™ Zoning System Applications - Minimum blower speed is 453 cfm.
BLOWER DATA
ML296UH070XV36B BLOWER PERFORMANCE (less lter)
SIDE RETURN AIR WITH OPTIONAL RETURN AIR BASE
0 through 0.8 in. w.g. (Heating) and 0 through 1.0 in. w.g. (Cooling) External Static Pressure Range
“ADJUST”
Switch
Positions
Second Stage “HEAT” Speed - cfm Second Stage “COOL” Speed - cfm
1
D
C B A D C B
+ 975 1095 1245 1385 855 1045 1205 1350
1
NORM 870 995 1130 1280 790 945 1090 1255
— 790 885 1010 1155 720 845 985 1130
“ADJUST”
Switch
Positions
First Stage “HEAT” Speed - cfm First Stage “COOL” Speed - cfm
D
1
C B A D C B
+ 925 1050 1175 1330 595 715 815 950
1
NORM 810 945 1070 1220 520 655 755 840
— 730 840 955 1095 490 595 670 745
1
Factory default jumper setting.
NOTES - The eect of static pressure is included in air volumes shown.
First stage HEAT is approximately 91% of the same second stage HEAT speed position.
First stage COOL (two-stage air conditioning units only) is approximately 70% of the same second stage COOL speed
position. Continuous Fan Only speed is approximately 38% of the same second stage COOL speed position - minimum
500 cfm. Lennox Harmony III™ Zoning System Applications - Minimum blower speed is 453 cfm.
Speed Switch Positions
1
A
1
A
1
A
1
A
Page 5
BLOWER DATA
ML296UH090XV48C BLOWER PERFORMANCE (less lter)
BOTTOM RETURN AIR, RETURN AIR FROM BOTH SIDES OR RETURN AIR FROM BOTTOM AND ONE SIDE
0 through 0.8 in. w.g. (Heating) and 0 through 1.0 in. w.g. (Cooling) External Static Pressure Range
“ADJUST”
Switch
Positions
Second Stage “HEAT” Speed - cfm Second Stage “COOL” Speed - cfm
1
D
C B A D C B
+ 1230 1310 1360 1605 1165 1375 1580 1770
1
NORM 1115 1195 1255 1455 1075 1265 1440 1645
— 1005 1070 1130 1335 935 1145 1320 1465
“ADJUST”
Switch
Positions
First Stage “HEAT” Speed - cfm First Stage “COOL” Speed - cfm
D
1
C B A D C B
+ 1165 1250 1315 1520 840 1005 1155 1315
1
NORM 1075 1140 1195 1405 780 915 1045 1190
— 935 1030 1065 1285 690 835 955 1070
1
Factory default jumper setting.
NOTES - The eect of static pressure is included in air volumes shown.
First stage HEAT is approximately 91% of the same second stage HEAT speed position.
First stage COOL (two-stage air conditioning units only) is approximately 70% of the same second stage COOL speed
position. Continuous Fan Only speed is approximately 38% of the same second stage COOL speed position - minimum
500 cfm. Lennox Harmony III™ Zoning System Applications - Minimum blower speed is 453 cfm.
Speed Switch Positions
1
A
1
A
BLOWER DATA
ML296UH090XV48C BLOWER PERFORMANCE (less lter)
SINGLE SIDE RETURN AIR
0 through 0.8 in. w.g. (Heating) and 0 through 1.0 in. w.g. (Cooling) External Static Pressure Range
“ADJUST”
Switch
Positions
Second Stage “HEAT” Speed - cfm Second Stage “COOL” Speed - cfm
1
D
C B A D C B
+ 1210 1275 1320 1555 1140 1340 1525 1725
1
NORM 1115 1175 1230 1400 1040 1235 1395 1565
— 990 1070 1125 1295 910 1120 1275 1400
“ADJUST”
Switch
Positions
First Stage “HEAT” Speed - cfm First Stage “COOL” Speed - cfm
D
1
C B A D C B
+ 1140 1230 1280 1455 820 1005 1135 1290
1
NORM 1040 1135 1180 1370 755 880 1025 1150
— 910 1000 1075 1250 680 815 925 1065
1
Factory default jumper setting.
NOTES - The eect of static pressure is included in air volumes shown.
First stage HEAT is approximately 91% of the same second stage HEAT speed position.
First stage COOL (two-stage air conditioning units only) is approximately 70% of the same second stage COOL speed
position. Continuous Fan Only speed is approximately 38% of the same second stage COOL speed position - minimum
500 cfm. Lennox Harmony III™ Zoning System Applications - Minimum blower speed is 453 cfm.
Speed Switch Positions
1
A
1
A
Page 6
BLOWER DATA
ML296UH110XV60C BLOWER PERFORMANCE (less lter)
BOTTOM RETURN AIR, RETURN AIR FROM BOTH SIDES OR RETURN AIR FROM BOTTOM AND ONE SIDE
0 through 0.8 in. w.g. (Heating) and 0 through 1.0 in. w.g. (Cooling) External Static Pressure Range
“ADJUST”
Switch
Positions
Second Stage “HEAT” Speed - cfm Second Stage “COOL” Speed - cfm
1
D
C B A D C B
Speed Switch Positions
1
A
+ 1560 1760 1905 2080 1312 1560 1744 1955
1
NORM 1415 1610 1740 1930 1219 1405 1569 1796
— 1285 1485 1560 1745 1075 1272 1428 1634
“ADJUST”
Switch
Positions
First Stage “HEAT” Speed - cfm First Stage “COOL” Speed - cfm
D
1
C B A D C B
1
A
+ 1155 1325 1420 1565 937 1064 1247 1407
1
NORM 1055 1200 1310 1480 864 972 1146 1282
— 935 1075 1170 1315 790 888 1025 1167
1
Factory default jumper setting.
NOTES - The eect of static pressure is included in air volumes shown.
First stage HEAT is approximately 91% of the same second stage HEAT speed position.
First stage COOL (two-stage air conditioning units only) is approximately 70% of the same second stage COOL speed
position. Continuous Fan Only speed is approximately 38% of the same second stage COOL speed position - minimum
500 cfm. Lennox Harmony III™ Zoning System Applications - Minimum blower speed is 478 cfm.
BLOWER DATA
ML296UH110XV60C BLOWER PERFORMANCE (less lter)
SINGLE SIDE RETURN AIR − Air volumes in bold (over 1800 cfm) require Optional Return Air Base and eld fabricated transition
to accommodate 20 x 25 x 1 in. air lter in order to maintain proper air velocity.
0 through 0.8 in. w.g. (Heating) and 0 through 1.0 in. w.g. (Cooling) External Static Pressure Range
“ADJUST”
Switch
Positions
Second Stage “HEAT” Speed - cfm Second Stage “COOL” Speed - cfm
1
D
C B A D C B
+ 1530 1735 1845 2025 1270 1519 1712 1899
1
NORM 1380 1555 1705 1860 1170 1363 1555 1774
— 1235 1440 1540 1710 1059 1218 1401 1581
“ADJUST”
Switch
Positions
First Stage “HEAT” Speed - cfm First Stage “COOL” Speed - cfm
D
1
C B A D C B
+ 1140 1280 1390 1550 918 1053 1198 1366
1
NORM 1040 1175 1260 1430 820 964 1095 1231
— 910 1080 1150 1265 722 852 987 1116
1
Factory default jumper setting.
NOTES - The eect of static pressure is included in air volumes shown.
First stage HEAT is approximately 91% of the same second stage HEAT speed position.
First stage COOL (two-stage air conditioning units only) is approximately 70% of the same second stage COOL speed
position. Continuous Fan Only speed is approximately 38% of the same second stage COOL speed position - minimum
500 cfm. Lennox Harmony III™ Zoning System Applications - Minimum blower speed is 478 cfm.
Speed Switch Positions
1
A
1
A
Page 7
Gas Valve
ML296UHV PARTS IDENTIFICATION
Field Make Up Box
Burner Box Assembly
Heat Exchanger
Combustion
Air Inducer
Access Panel
Pressure
Switch
Assembly
Door
Interlock
Switch
Bag Assemblies
(shipping location)
Primary Limit
Variable Speed Motor
Two-Stage Integrated Control
FIGURE 1
Page 8
I-UNIT COMPONENTS
ML296UHV(X) unit components are shown in figure 1. The
gas valve, combustion air inducer and burners can be ac
cessed by removing the access panel. Electrical compo
nents are in the control box (figure 2) found in the blower
section.
CAUTION
Electrostatic discharge can affect elec
tronic components. Take precautions
to neutralize electrostatic charge by
touching your hand and tools to metal
prior to handling the control.
A- Control Box
1. Control Transformer (T1)
A transformer located in the control box provides power to
the low voltage section of the unit. Transformers on all
models are rated 40VA with a 120V primary and a 24V sec
ondary.
2. Door Interlock Switch (S51)
A door interlock switch rated 14A at 125VAC is wired in se
ries with line voltage. When the inner blower access panel
is removed the unit will shut down.
Control Box Components
Transformer
3. Integrated Control (A92)
Units are equipped with a two-stage, variable speed inte
grated control. The system consists of a ignition / blower
control (figure 3) with control pin designations in tables 3
and 4 and ignitor. The control and ignitor work in combina
tion to ensure furnace ignition and ignitor durability. The
control provides gas ignition, safety checks and indoor
blower control with two-stage gas heating. The furnace
combustion air inducer, gas valve and indoor blower are
controlled in response to various system inputs such as
thermostat signal, pressure and limit switch signal and
flame signal.
The furnace has a built-in, self-diagnostic capability. If a
system problem occurs, a fault code is shown by a red LED
on the control. The control continuously monitors its own
operation and the operation of the system. If a failure oc
curs, the LED will indicate the failure code. The flash codes
are presented in table 2.
Fault Code History Button
The control stores the last five fault codes in memory. A
pushbutton switch is located on the control. When the
pushbutton switch is pressed and released, the control
flashes the stored fault codes. The most recent fault code is
flashed first; the oldest fault code is flashed last. To clear
the fault code history, press and hold the pushbutton switch
in for more than 5 seconds before releasing.
Door Interlock Switch
Integrated Control
FIGURE 2
WARNING
Shock hazard.
Disconnect power before servicing. Integrated
control is not field repairable. If control is inoper
able, simply replace entire control.
Can cause injury or death. Unsafe operation will re
sult if repair is attempted.
Single Stage Thermostat Operation
The automatic heat staging option allows a single stage
thermostat to be used with two stage furnace models. To
activate this option, move the jumper pin (see Figure 3) to
desired setting (5 minutes or 10 minutes). The furnace will
start on 1st stage heat and stay at 1st stage heat for the
duration of the selected time before switching to 2nd stage
heat.
W1 on the integrated control must be connected to W1 on
the thermostat.
High Heat State LED
A green LED is provided on the control board to indicate
high heat state
(see Table 1).
CFM LED
An amber LED is provided on the control board to display
CFM. To determine what CFM the motor is delivering at any
time, count the number of times the amber LED flashes.
Each flash signifies 100 CFM; count the flashes and multi
ply by 100 to determine the actual CFM delivered (for ex
ample: 5 flashes x 100 = 500 CFM).
Page 9
TABLE 1
High Heat State Green LED
LED Status DESCRIPTION
LED Off No demand for high heat
LED On High heat demand, operating normally
LED Flashing
High heat demand, high pressure
switch not closed
TABLE 2
Diagnostic Codes Red LED
LED Status DESCRIPTION
LED Off
LED On Normal operation.
1 Flash
2 Flashes
3 Flashes
4 Flashes Primary limit switch open.
5 Flashes Not used
6 Flashes Pressure switch cycle lockout.
7 Flashes Lockout, burners fail to light.
8 Flashes
9 Flashes Line voltage polarity incorrect.
Control 5 Pin Terminal Designation
PIN # Function
1 Ignitor (Hot)
2 Combustion Air Inducer High Speed
3 Combustion Air Inducer Low Speed
4 Combustion Air Inducer Neutral
5 Ignitor Neutral
Airflow Adjustments
Cooling Mode
The units are factory set for the highest airflow for each model.
Adjustments can be made to the cooling airflow by reposi
tioning the jumper plug marked COOL – A, B, C, D (see Fig
ure 3). To determine what CFM the motor is delivering at
any time, count the number of times the amber LED on the
control board flashes. Each flash signifies 100 CFM; count
the flashes and multiply by 100 to determine the actual CFM
delivered (for example: 5 flashes x 100 = 500 CFM).
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.
Low-fire pressure, rollout or limit
switch open.
Lockout, buners lost flame too many
times.
TABLE 3
TABLE 4
12 Pin Terminal Designation
PIN # Function
1 Gas Valve Second Stage
2 Second Stage Prove Switch
3 Rollout Switch In
4 Ground
5 24V Hot
6 Primary Limit In
7 Gas Valve First Stage
8 Gas Valve Common
9 24V Neutral
10 Ground
11 Rollout Switch Out
12 First Stage Prove Switch
Heating Mode
These units are factory set to run at the middle of the heating
rise range as shown on the unit rating plate. If higher or lower
rise is desired, reposition the jumper plug marked HEAT - A,
B, C, C (see Figure 3) . To determine what CFM the motor is
delivering at any time, count the number of times the amber
LED on the control board flashes. Each flash signifies 100
CFM; count the flashes and multiply by 100 to determine the
actual CFM delivered (for example: 5 flashes x 100= 500.
Adjust Tap
Airflow amounts may be increased or decreased by 10% by
moving the ADJUST jumper plug (see Figure 3) from the
NORM position to the (+) or (-) position. Changes to the AD
JUST tap will affect both cooling and heating airflows. The
TEST position on the ADJUST tap is not used.
Continuous Blower Operation
The comfort level of the living space can be enhanced
when using this feature by allowing continuous circulation
of air between calls for cooling or heating. The circulation of
air occurs at half the full cooling airflow rate.
To engage the continuous blower operation, place the fan
switch on the thermostat into the ON position. A call for fan
from the thermostat closes R to G on the ignition control
board. The control waits for a 1 second thermostat delay
before responding to the call for fan by ramping the circulat
ing blower up to 50% of the cooling speed. When the call for
continuous fan is satisfied, the control immediately ramps
down the circulating blower.
Page 10
INTEGRATED CONTROL
Heat Stage Jumper
(single stage shown)
Air Flow
Jumper
TERMINAL DESIGNATIONS
HUM -Humidifier (120VAC)
Line - Input (120VAC)
XFMR - Transformer (120VAC)
Cont - Continuous blower
EAC - Indoor Air Accessory (120VAC)
Cool - Cool Speed (120VAC)
Park 1 - Dead terminal for alternate speed tap
Park 2 - Dead terminal for alternate speed tap
HI Heat - High heat speed
LO Heat - Low heat speed
FIGURE 3
Heat
Taps
Cool
Taps
Page 11
B- Indoor Blower Motor
Power Choke
(5 Ton Only)
To Remove Blower From Unit: Remove Bolts and
Wiring Jackplugs. Then Slide Out Front of Unit.
Blower Motor
(B3)
FIGURE 4
Blower Motor (B3)
Blower motors are manufactured by GenTeq and Nidec. See
figures 5 and 6. Motors operate the same and are only differ
ent in physical appearance. They are both three‐phase, elec
tronically controlled DC brushless motors (controller converts
single-phase AC to three-phase DC), with a permanent mag
net type rotor (figure 5). Because these motors have a per
manent magnet rotor it does not need brushes like conven
tional DC motors.
Internal components for both manufactured motors are simi
lar and shown in figure 7. The stator windings are split into
three poles which are electrically connected to the controller.
This arrangement allows motor wi ndings to tu r n on and off
in sequence by the controller.
NIDEC BLOWER MOTOR B3
MOTOR
J49
16X4W
J48
CONTROLLER
FIGURE 6
BLOWER MOTOR COMPONENTS
STATOR
(WINDINGS)
BEARING
OUTPUT
SHAFT
ROTOR
FIGURE 7
The controller uses sensing devices to sense what position
the rotor is in at any given time. By sensing the position of the
rotor and then switching the motor windings on and off in se
quence, the rotor shaft turns the blower.
All blower motors use single phase power. An external
run capacitor is not used. The motor uses permanently
lubricated ball‐type bearings.
Internal Operation
A solid‐state controller is attached to the motor. The
controller is primarily an AC to DC converter. Converted
DC power is used to drive the motor. The controller con
tains a microprocessor which monitors varying condi
tions inside the motor (such as motor workload). The
controller on the Emerson motor includes the 16X4W
control with three LED's PW, RX and TX located on the
face for troubleshooting. Figure 6 shows the location of
the 16X4W and table 5 the LED codes.
GenTeq BLOWER MOTOR B3
J48
MOTOR
CONTROLLER
J49
FIGURE 5
Each time the controller switches a stator winding (figure 7) on
and off, it is called a “pulse.” The length of time each pulse
stays on is called the “pulse width.” By varying the pulse width
(figure 10), the controller varies motor speed (called “pulse‐
width modulation”). This allows for precise control of motor
speed and allows the motor to compensate for varying load
conditions as sensed by the controller. In this case, the control
ler monitors the static workload on the motor and varies motor
rpm in order to maintain constant airflow (cfm).
The motor controller is driven by the Two-stage Variable
Speed Integrated control board. The board receives its
demand (PWM signal or fixed 24 VAC or VDC signal) from
optional controls such as the Harmony IIIt zoning system,
SignatureStatt, Efficiency Plus Humidity Control (CCB1) or a
conventional thermostat.
Page 12
TABLE 5
Emerson Motor Only
PW
LEDRXLEDTXLED
Off Blink Blink
Blink Blink Blink Rotating Normal. PW blink is 100cfm/blink
Blink Off Blink
Off Off Off
Motor rpm is continually adjusted internally to maintain
constant cfm. The controller monitors the static work load on
the motor and motor amp‐draw to determine the amount of
rpm adjustment. Blower rpm may be adjusted any amount in
order to maintain a constant cfm as shown in Blower Ratings
Tables. The cfm remains relatively stable over a broad range
of static pressure. Since the blower constantly adjusts rpm to
maintain a specified cfm, motor rpm is not rated. Hence, the
terms “cool speed” , “heat speed ” or “speed tap” in this manu
al, on the unit wiring diagram and on blower B3, refer to blower
cfm regardless of motor rpm.
The unit control indicates the desired cfm. The blower will
maintain the desired cfm as long as external static pressure
does not exceed 0.8”. If the system exceeds this amount, the
blower may enter a “cut back”, mode wherein it then slows
down to protect itself from electrical damage. During this “cut
back” mode the unit control will still indicate the same desired
cfm regardless of actual motor rpm.
When Harmony is used, speed taps are overridden and a
PWM signal generated by the Harmony controller continuous
ly varies motor speed based upon zone demands.
Initial Power Up
When line voltage is applied to B3, there will be a large inrush
of power lasting less than 1/4 second. This inrush charges a
bank of DC filter capacitors inside the controller. If the discon
nect switch is bounced when the disconnect is closed, the dis
connect contacts may become welded. Try not to bounce the
disconnect switch when applying power to the unit.
Motor Start‐Up
When B3 begins start‐up, the motor gently vibrates back and
forth for a moment. This is normal. During this time the elec
tronic controller is determining the exact position of the rotor.
Once the motor begins turning, the controller slowly eases
the motor up to speed (this is called “soft‐start”). The motor
may take as long as 10‐15 seconds to reach full speed. If the
Motor
Blower
Not
Rotating
Not
Rotating
Not
Rotating
Turn off power for 1 minute then restart. If motor still
Verify power to the 16X4W. Turn off power then restart.
Action
Normal
Verify 16X4W and motor control hp match. Verify
power to motor control.
does not rotate replace the controller.
If LED's are still out, replace controller.
motor does not reach 200rpm within 13 seconds, the motor
shuts down. Then the motor will immediately attempt a re
start. The shutdown feature provides protection in case of a
frozen bearing or blocked blower wheel. The motor may at
tempt to start eight times. If the motor does not start after the
eighth try, the controller locks out. Reset controller by momen
tarily turning off power to unit.
The DC filter capacitors inside the controller are connected
electrically to the speed tap wires. The capacitors take
approximately 5 minutes to discharge when the disconnect
is opened. For this reason it is necessary to wait at least 5
minutes after turning off power to the unit before attempt
ing to change speed taps.
DANGER
Disconnect power from unit and
wait at least five minutes to allow
capacitors to discharge before at
tempting to adjust motor speed tap
settings. Failure to wait may cause
personal injury or death.
External Operation (Speed Tap Priority)
Figures 8 and 9 show the two quick‐connect jacks (J48 and
J49) which connect the motor to the ML296UHV. Jack J48
is the power plug and jack J49 connects the unit controls to
the motor.
Jack J48 is the power plug. Line voltage must be applied to
J48 pins 4 and 5 in order for the motor to operate. When
using 120VAC pins 1 and 2 must be jumpered.
Jack J49 connects the unit controls to the motor. The motor
assigns priority to J49 pin 2 so that if a call for cooling and a
call for heating are concurrent, heating call overrides and
the blower operates on high speed heating tap.
Page 13
GenTeq HARNESS CONNECTORS
POWER
CONNECTOR J48
1
J48
PIN 1 ‐ Jumper PIN 1 to PIN2 for 120VAC line input only.
PIN 2 ‐ Jumper PIN 1 to PIN2 for 120VAC line input only.
PIN 3 ‐ Ground
PIN 4 ‐ AC Line
PIN 5 ‐ AC Line
CONTROL
CONNECTOR J49
16
J49
1
PIN 1 ‐ C1
PIN 2 ‐ W / W1
PIN 3 ‐ C2
PIN 4 - Delay
PIN 5 ‐ Cool
PIN 6 ‐ Y1
PIN 7 ‐ Adjust
PIN 8 ‐ Out
PIN 9 ‐ O
PIN 10 ‐ DS(PWM)
PIN 11 ‐ Heat
PIN 12 ‐ R
PIN 13 ‐ EM / W2
PIN 14 ‐ Y / Y2
PIN 15 ‐ G
PIN 16 ‐ Out +
FIGURE 8
EMERSON MOTOR HARNESS CONNECTORS
POWER
CONNECTOR J48
1
J48
PIN 1 ‐ Jumper PIN 1 to PIN2 for 120VAC line input only.
PIN 2 ‐ Jumper PIN 1 to PIN2 for 120VAC line input only.
PIN 3 ‐ Ground
PIN 4 ‐ AC Line
PIN 5 ‐ AC Line
CONTROL
CONNECTOR J49
16
J49
PIN 1 ‐ C1
1
PIN 2 ‐ W / W1
PIN 3 ‐ C2
PIN 4 - Delay
PIN 5 ‐ Cool
PIN 6 ‐ Y1
PIN 7 ‐ Adjust
PIN 8 ‐ Out
PIN 9 ‐ O
PIN 10 ‐ DS(PWM)
PIN 11 ‐ Heat
PIN 12 ‐ R
PIN 13 ‐ EM / W2
PIN 14 ‐ Y / Y2
PIN 15 ‐ G
PIN 16 ‐ Out +
FIGURE 9
Power Choke (L13)
A choke coil is used on 5 ton 1 hp units. The choke is lo
cated on the blower housing and is used to suppress transient
current spikes.
Precautions
If the furnace or its electronically controlled blower motor is im
properly or inadequately grounded, it may cause television in
terference (commonly known as RFI or radio frequency inter
ference).
This interference is caused by internal switching fre
quencies of the motor controller. TV interference may
show u p as small speck s or l ines which randomly appear
on the TV screen accompanied by pops or clicks in the sound.
Before attempting any service, make sure the indoor unit is
causing the interference. To check, disconnect power to indoor
unit then check TV for continued signs of interference.
TV interference may be stopped by making sure the mo
tor is solidly grounded to the cabinet (metal to metal) and
by making sure the cabinet is solidly grounded. If TV in
te r ference persist s, mak e sure the television (and all af
fected RF appliances) are moved away from the furnace. Also
make sure affected appliances are connected to a separate
electrical circuit.
Page 14
MOTOR SPEED CONTROL WITH D.C. PULSE‐WIDTH MODULATION
ÇÇ
Motor speed is determined by the size of the electrical pulse sent to
the motor windings. The longer the pulse, the faster the motor.
OUTPUT FROM CONTROLLER TO MOTOR WINDINGS
WINDINGS TURNED OFF
The frequency of the pulses to the windings is 20KHz.
DO NOT ATTEMPT TO MEASURE THESE VOLTAGES.
LOW SPEED HEAT/COOL (output from controller to motor windings)
One
Pulse
One revolution
325VDC
O volts
WINDING #1
325VDC
O volts
WINDING #2
325VDC
O volts
WINDING #3
HIGH SPEED HEAT (output from controller to motor windings)
One revolution
325VDC
O volts
WINDING #1
325VDC
O volts
WINDING #2
325VDC
O volts
WINDING #3
WINDINGS TURNED ON
ON PULSE
OFF PULSE
HIGH SPEED COOL (output from controller to motor windings)
One revolution
325VDC
O volts
WINDING #1
325VDC
O volts
WINDING #2
325VDC
O volts
WINDING #3
FIGURE 10
Page 15
C- Heating Components
1. Ignitor
The ignitor is made of durable silicon nitride. Ignitor longev
ity is enhanced by controlling voltage to the ignitor. The in
tegrated control provides a regulated 120 volts to the igni
tor for a consistent ignition and long ignitor life. Ohm value
should be 39 to 70. See figure 11 for ignitor location and fig
ure 12 for ignitor check out.
NOTE - The ML296UHV(X) furnace contains electronic
components that are polarity sensitive. Make sure that the
furnace is wired correctly and is properly grounded.
2. Flame Sensor
A flame sensor is located on the left side of the burner sup
port. See figure 11. The sensor tip protrudes into the flame
envelope of the left-most burner. The sensor can be re
moved for service without removing any part of the burn
ers. During operation, flame is sensed by current passed
through the flame and sensing electrode. The SureLight
control allows the gas valve to remain open as long as
flame signal is sensed. See table 6 for flame signal.
TABLE 6
Flame Signal in Microamps
Normal
1.5 or greater 1.0 or less 0.5
3. Gas Valve
The valve (figure 49) is internally redundant to assure safe
ty shut-off. If the gas valve must be replaced, the same type
valve must be used.
24VAC terminals and gas control knob are located on the
valve. A wire harness connects the terminals from the gas
valve to the electronic ignition control. 24V applied to the termi
nals energizes the valve.
Inlet and outlet pressure taps are located on the valve. A regu
lator adjustment screw is located on the valve.
Low Drop Out
LPG change over kits are available from Lennox. Kits include
burner orifices and a gas valve.
4. Flame Rollout Switches (S47)
Flame rollout switch is a high temperature limit located on
top of the burner box, one on each side.- See figure 11. The
limit is a N.C. SPST manual‐reset limit. When S47 senses
rollout, the circuit breaks and the ignition control immedi
ately stops ignition and closes the gas valve. Rollout can be
caused by a blocked heat exchanger, flue or lack of com
bustion air. The switch is factory set to trip (open) at 210°F
and cannot be adjusted. The switch can be manually reset.
To manually reset a tripped switch, push the reset button lo
cated on the control.
5. Burners
All units use inshot burners. Burners are factory set and re
quire no adjustment. Always operate the unit with the burner
box front panel in place. Each burner uses an orifice (see
table 21 for orifice size) that is precisely matched to the burn
er input. Burners can be removed as a one piece assembly
for service. If burner assembly has been removed, it is critical
to align center of each burner to the center of the clamshell
when re-installing. See more detail in Section VI- MAINTE
NANCE.
6. Primary Limit Control (S10)
The primary limit (S10) is located in the heating vestibule pan
el. When excess heat is sensed in the heat exchanger, the
limit will open. If the limit is open, the furnace control energizes
the supply air blower and closes the gas valve. The limit auto
matically resets when unit temperature returns to normal. The
switch must reset within three minutes or the SureLight control
will go into Watch guard for one hour. The switch is factory
set and cannot be adjusted. The switch may have a different
set point for each unit model number. See Lennox Repair
Parts Handbook if limit switch must be replaced,
Page 16
Loading...