Lennox ML296UHV(X), ML296UH045XV36B, ML296UH070XV36B Series Manual

Page 1

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

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

Page 2

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.

Annual Fuel Utilization E󰀩ciency based on DOE test procedures and according to FTC labeling regulations. Isolated combustion system rating for non-weatherized furnaces.

Model No. ML296UH045XV36B ML296UH070XV36B

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

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.

Annual Fuel Utilization E󰀩ciency based on DOE test procedures and according to FTC labeling regulations. Isolated combustion system rating for non-weatherized furnaces.

Page 2

Page 3

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

C B A D C B

+ 745 875 990 1005 905 1075 1210 1370

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

C B A D C B

+ 685 765 895 910 595 760 865 980

NORM 620 705 800 820 540 660 785 890

— 545 625 715 725 485 600 695 790

Factory default jumper setting.

NOTES - The e󰀨ect 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

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

NORM 645 725 810 815 550 680 770 880

— 570 655 735 750 465 610 720 775

Factory default jumper setting.

Second Stage “HEAT” Speed - cfm Second Stage “COOL” Speed - cfm

C B A D C B

First Stage “HEAT” Speed - cfm First Stage “COOL” Speed - cfm

C B A D C B

Speed Switch Positions

Page 3

Page 4

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

C B A D C B

Speed Switch Positions

+ 780 880 990 1010 920 1065 1205 1340

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

C B A D C B

+ 705 795 905 925 610 760 845 975

NORM 645 725 810 815 550 680 770 880

— 570 655 735 750 465 610 720 775

Factory default jumper setting.

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

C B A D C B

+ 965 1130 1255 1400 860 1060 1215 1365

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

C B A D C B

+ 940 1070 1195 1345 600 740 840 970

NORM 830 965 1100 1235 555 665 770 855

— 755 840 975 1130 500 600 680 790

Factory default jumper setting.

Speed Switch Positions

Page 4

Page 5

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

C B A D C B

Speed Switch Positions

+ 980 1095 1225 1395 840 1050 1205 1355

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

C B A D C B

+ 920 1055 1205 1325 590 705 805 955

NORM 800 950 1075 1215 540 640 725 820

— 730 810 960 1095 500 580 665 720

Factory default jumper setting.

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

C B A D C B

+ 975 1095 1245 1385 855 1045 1205 1350

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

C B A D C B

+ 925 1050 1175 1330 595 715 815 950

NORM 810 945 1070 1220 520 655 755 840

— 730 840 955 1095 490 595 670 745

Factory default jumper setting.

Speed Switch Positions

Page 5

Page 6

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

C B A D C B

+ 1230 1310 1360 1605 1165 1375 1580 1770

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

C B A D C B

+ 1165 1250 1315 1520 840 1005 1155 1315

NORM 1075 1140 1195 1405 780 915 1045 1190

— 935 1030 1065 1285 690 835 955 1070

Factory default jumper setting.

Speed Switch Positions

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

C B A D C B

+ 1210 1275 1320 1555 1140 1340 1525 1725

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

C B A D C B

+ 1140 1230 1280 1455 820 1005 1135 1290

NORM 1040 1135 1180 1370 755 880 1025 1150

— 910 1000 1075 1250 680 815 925 1065

Factory default jumper setting.

Speed Switch Positions

Page 6

Page 7

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

C B A D C B

Speed Switch Positions

+ 1560 1760 1905 2080 1312 1560 1744 1955

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

C B A D C B

+ 1155 1325 1420 1565 937 1064 1247 1407

NORM 1055 1200 1310 1480 864 972 1146 1282

— 935 1075 1170 1315 790 888 1025 1167

Factory default jumper setting.

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

C B A D C B

+ 1530 1735 1845 2025 1270 1519 1712 1899

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

C B A D C B

+ 1140 1280 1390 1550 918 1053 1198 1366

NORM 1040 1175 1260 1430 820 964 1095 1231

— 910 1080 1150 1265 722 852 987 1116

Factory default jumper setting.

Speed Switch Positions

Page 7

Page 8

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

Page 9

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

Page 10

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

Page 11

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

Page 12

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

Page 13

TABLE 5

Emerson Motor Only

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

Page 14

GenTeq HARNESS CONNECTORS

POWER

CONNECTOR J48

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

J49

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

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

J49 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 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

Page 15

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

Page 16

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

Page 17

Intake Air Top Cap

Rollout Switch

ML296UHV HEATING COMPONENTS

Burner Assembly

Sensor

Rollout Switch

Ignitor

Burner Box Cover

Manifold And Gas Orifices

Two-Stage Gas Valve

FIGURE 11

Page 17

Page 18

Check ignitor circuit for correct resistance.

Test 1

Remove 4-pin plug from control.

Check ohms reading across terminals 1 and 5.

Reading should be between 39 and 70 ohms. 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.

Meter

(set to ohms)

ML296UHV Ignitor Check

Integrated Control Detail

Seperate the 2-pin jack-plug near the manifold and check

Check ignitor for correct resistance.

resistance of ignitor at the plug. Reading should be

between 39 and 70 ohms. 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

Meter

(set to ohms)

Insert meter probes into terminals 1 and 5 (use small

Check ignitor for correct voltage

diameter probes in order not to damage plug).

Check voltage during 20 second ignitor warm up period.

Voltage should read 120 volts +

these values, check for correct supply voltage to furnace.

Test 3

10%. If voltage reads below

Integrated Control Detail

Meter

(set to AC volts)

Integrated Control Detail

FIGURE 12

Page 18

Page 19

7. Combustion Air Inducer (B6) and Cold End Header Box

All ML296UHV(X) units use a two-stage combustion air in ducer to move air through the burners and heat exchanger during heating operation. The blower uses a 120VAC mo tor. The motor operates during all heating operation and is controlled by integrated control control A92. The inducer also operates for 15 seconds before burner ignition (pre‐ purge) and for 5 seconds after the gas valve closes (post‐ purge). The inducer operates on low speed during firststage heat, then switches to high speed for second stage heat.

NOTE - Each furnace model uses a unique CAI. Refer to Lennox Repair Parts listing for correct inducer for replace ment.

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 pressure switch hoses. The pressure switch measures the pressure differential across the combustion air induc er orifice or difference in the channel and the box. If re

placement is necessary the gaskets used to seal the box to the vestibule panel and the combustion air in ducer to the box, must also be replaced.

A proving switch connected to the combustion air inducer ori fice plate is used to prove inducer operation. The combustion air inducer orifice will be different for each model. See table 7 for orifice sizes. The pressure switch measures the pressure differential across the combustion air inducer orifice. When the proving switch opens, the furnace control (A92) immedi ately closes the gas valve to prevent burner operation.

TABLE 7

ML296UHV(X) Unit C.A.I. Orifice Size

-045 0.618

-070 0.920

-090 0.920

-110 1.040

8. Combustion Air Inducer Pressure Switch (S18)

ML296UHV(X) series units are equipped with a dual com bustion air pressure switch (first and second stage) located on the combustion air inducer orifice bracket. See figure 13. The switch is connected to the combustion air inducer hous ing by means of a flexible silicone hose. It monitors negative air pressure in the combustion air inducer housing.

The switches are a single‐pole single‐throw proving switch electrically connected to the integrated control. The purpose of the switch is to prevent burner operation if the combustion air inducer is not operating or if the flue becomes obstructed.

On heat demand (first or second stage) the switch senses that the combustion air inducer is operating. It closes a cir cuit to the integrated control when pressure inside the com bustion air inducer decreases to a certain set point. Set points vary depending on unit size. See table 8. The pressure sensed by the switch is negative relative to atmo spheric pressure. If the flue becomes obstructed during op eration, the switch senses a loss of negative pressure (pressure becomes more equal with atmospheric pres sure) and opens the circuit to the furnace control and gas valve. A bleed port on the switch allows relatively dry air in the vestibule to purge switch tubing, to prevent condensate build up.

COMBUSTION AIR PRESSURE SWITCH

Tap (negative - )

Tap (positive +)

Low Fire Switch

3/16 Terminals

" Terminals

1/4

High Fire Switch

FIGURE 13

NOTE - The switch is factory set and is not field adjustable. It is a safety shut‐down control in the furnace and must not be by-passed for any reason. If switch is closed or bypassed, the control will not initiate ignition at start up.

TABLE 8 0 - 4500'

ML296UHV(X)

Unit

-045 0.35 0.60

-070 0.50 0.85

-090 0.50 0.90

-110 0.45 0.90

Set Point Low

Heat

Set Point High Heat

TABLE 9 4501 - 7500'

ML296UHV(X)

Unit

-045 0.35 0.55

-070 0.45 0.75

-090 0.50 0.85

-110 0.45 0.81

Set Point Low

Heat

Set Point High Heat

TABLE 10 7501 - 10,000'

ML296UHV(X)

Unit

-045 0.35 0.50

-070 0.40 0.70

-090 0.45 0.81

-110 0.41 0.74

Set Point Low

Heat

Set Point High Heat

Page 19

Page 20

Pressure Switch Check

To check pressure switch differential, refer to figure 14 and use the provided fittings and tubing to follow the steps be low.

1 - Remove thermostat demand and allow unit to cycle

off.

2 - Remove the tubing from the negative side (red and black

or red) and positive side (black) of the pressure switch (leave both connected to cold end header box).

3 - Take the 2” length square tubing and connect to the

positive (+) side of the pressure switch. Take the 10” length square tubing and tee into the tubing from the positive side of the cold end header box and the other side of the 2” square tubing. Connect the other end of the 10” square tubing the the positive (+) side of the measuring device.

4 - Take a second piece the 2” length square tubing and

connect to the negative (-) side of the pressure switch. Take a second piece of 10” length square tubing and tee into the tubing from the negative (-) side of the cold end header box and the other side of the 2” square tub ing. Connect the other end of the 10” square tubing the the negative (-) side of the measuring device.

PRESSURE SWITCH CHECK

Black Tubing

(positive +)

Te e

5 - 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 pres sure differential.

The pressure differential should be at least

0.15” greater than those listed in the tables 8, 9 and

10. Readings in table are the set points or “break

points”.

6 - Remove thermostat demand and allow to cycle off.

7 - Replace original pressure switch tubing.

NOTE - Pressure differential values (set point) in table are the ”break”, or ”open” specifications. ”Make”, or ”close” pressure differentials are 0.15” greater than the set points listed in table.

2” long Square

Tubing

Red and Black

or Red Tubing

(negative -)

10” Long Square Tubing

Measuring Device

FIGURE 14

Page 20

Page 21

II-PLACEMENT AND INSTALLATION

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.

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 ap pliance must be certified to ULC S636 and supplied by a single manufacturer as part of an approved vent (ex haust) system. In addition, the first three feet of vent pipe from the furnace flue collar must be accessible for inspection.

PIPING AND FITTINGS SPECIFICATIONS

TABLE 11

Schedule 40 PVC (Pipe) D1785 Schedule 40 PVC (Cellular Core Pipe) F891

Schedule 40 PVC (Fittings) D2466

Schedule 40 CPVC (Pipe) F441

Schedule 40 CPVC (Fittings) F438

SDR-21 PVC or SDR-26 PVC (Pipe) D2241

SDR-21 CPVC or SDR-26 CPVC (Pipe) F442

Schedule 40 ABS Cellular Core DWV (Pipe) F628

Schedule 40 ABS (Pipe) D1527

Schedule 40 ABS (Fittings) D2468

ABS-DWV (Drain Waste & Vent) (Pipe & Fittings)

PVC-DWV (Drain Waste & Vent) Pipe & Fittings)

PRIMER & SOLVENT CEMENT

PVC & CPVC Primer F656 PVC Solvent Cement D2564

CPVC Solvent Cement F493

ABS Solvent Cement D2235

PVC/CPVC/ABS All Purpose Cement For Fittings & Pipe of the same material

ABS to PVC or CPVC Transition Solvent Cement

CANADA PIPE & FITTING & SOLVENT

CEMENT

PVC & CPVC Pipe and Fittings PVC & CPVC Solvent Cement

ABS to PVC or CPVC Transition Cement

POLYPROPYLENE VENTING SYSTEM

PolyPro® by Duravent

InnoFlue® by Centrotherm ULC-S636

D2661

D2665

ASTM

SPECIFICATION

D2564, D2235, F493

D3138

MARKING

ULCS636

ULC-S636

IMPORTANT

ML296UHV 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 con nections to the PVC fittings in the unit.

Use PVC primer and solvent cement or ABS solvent cement meeting ASTM specifications, refer to Table 11. As an alter nate, use all purpose cement, to bond ABS, PVC, or CPVC pipe when using fittings and pipe made of the same materi als. Use transition solvent cement when bonding ABS to ei ther PVC or CPVC.

Page 21

Page 22

Input Size

045

070

090

110

OUTDOOR TERMINATION USAGE*

TABLE 12

STANDARD CONCENTRIC

Flush

Vent Pipe

Dia. in.

2-1/2

2-1/2 YES YES

Mount

Kit

51W11

(US)

51W12

(CA)

2 YES YES YES

3 YES YES

YES YES

YES YES YES

2 inch 3 inch 2 inch

22G44 (US)

30G28 (CA)

Wall Kit Wall Ring Kit

44J40

(US)

81J20 (CA)

YES

15F74

YES

1-1/2 inch 2 inch 3 inch

Field

Fabricated

YES

YES YES YES

71M80

(US)

44W92

(CA)

YES

69M29

(US)

44W92

(CA)

60L46 (US)

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.

Requires field-provided outdoor 1-1/2” exhaust accelerator.

Concentric kits 71M80 and 44W92 include 1-1/2” outdoor accelerator, when used with 045 and 070 input models.

Flush mount kits 51W11 and 51W12 includes 1-1/2 in. outdoor exhaust accelerator, required when used with 045, 070 and 090 input models.

Termination kits 30G28, 44W92, 44W93 and 81J20 are certified to ULC S636 for use in Canada only.

See table 17 for vent accelerator requirements.

NOTE - Time is critical at this stage. Do not allow prim

Joint Cementing Procedure

All cementing of joints should be done according to the specifications outlined in ASTM D 2855.

er to dry before applying cement.

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

DANGER

care to keep excess cement out of socket. Apply sec ond coat to end of pipe.

DANGER OF EXPLOSION!

Fumes from PVC glue may ignite during system check. Allow fumes to dissipate for at least 5 minutes before placing unit into operation.

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

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.

NOTE - Check the inside of vent pipe thoroughly for any obstruction that may alter furnace operation.

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.

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 indi cate an improper assembly due to insufficient sol vent.

9 - Handle joints carefully until completely set.

Page 22

Page 23

Venting Practices

Piping Suspension Guidelines

Conduct the following test while each appliance is operat ing and the other appliances (which are not operating) re main connected to the common venting system. If the venting system has been installed improperly, you must correct the system as indicated in the general venting re quirements section.

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.

NOTE - All horizontal runs of exhaust pipe must slope back to ward unit a minimum of 1/4” (6mm) drop for each 12” (305mm).

Wall Thickness Guidelines

24” maximum 3/4” minimum

inside outside

FIGURE 15

9. 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.

10. 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.

Removal of the Furnace from Common Vent

In the event that an existing furnace is removed from a venting system commonly run with separate gas ap pliances, the venting system is likely to be too large to properly vent the remaining attached appliances.

Wall

WARNING

CARBON MONOXIDE POISONING HAZARD Failure to follow the steps outlined below for each

appliance connected to the venting system being placed into operation could result in carbon mon oxide poisoning or death. The following steps shall be followed for each ap pliance connected to the venting system being placed into operation, while all other appliances connected to the venting system are not in operation:

1 - Seal any unused openings in the common venting sys

tem.

2 - Inspect the venting system for proper size and horizontal

pitch. Determine that there is no blockage, restriction, leakage, corrosion, or other deficiencies which could cause an unsafe condition.

3 - Close all building doors and windows and all doors be

tween the space in which the appliances remaining connected to the common venting system are located and other spaces of the building. Turn on clothes dry ers and any appliances not connected to the common venting system. Turn on any exhaust fans, such as range hoods and bathroom exhausts, so they will oper ate at maximum speed. Do not operate a summer ex haust fan. Close fireplace dampers.

4 - Follow the lighting instructions. Turn on the appliance

that is being inspected. Adjust the thermostat so that the appliance operates continuously.

5 - After the main burner has operated for 5 minutes, test

for leaks of flue gases at the draft hood relief opening. Use the flame of a match or candle.

6 - After determining that each appliance connected to the

common venting system is venting properly, (step 3) return all doors, widows, exhaust fans, fireplace damp ers, and any other gas-burning appliances to their pre vious mode of operation.

Page 23

Page 24

7 - If a venting problem is found during any of the preced

ing tests, the common venting system must be modi fied to correct the problem.

Resize the common venting system to the minimum vent pipe size determined by using the appropriate tables in Appendix G. (These are in the current stan dards of the National Fuel Gas Code ANSI Z223.1.

CHIMNEY

OR GAS

VENT

(Check sizing

for water

heater only)

FURNACE

(Replaced by EL296)

If an ML296UHV furnace replaces a furnace which was commonly vented with another gas appliance, the size of the existing vent pipe for that gas appliance must be checked. Without the heat of the original furnace flue prod ucts, 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.

REPLACING FURNACE THAT

WAS PART OF A COMMON

VENT SYSTEM

WATER

HEATER

OPENINGS

(To Adjacent

Room)

FIGURE 16

Exhaust Piping (Figures 17, 19 and 20)

Route piping to outside of structure. Continue with installa tion following instructions given in piping termination sec tion.

quirements stated in the unit installation instruction – min imum & maximum vent lengths, termination clearances, etc. – apply and must be followed. Follow the instructions provided with PoyPro by DuraVent and InnoFlue by Cen trotherm venting system for assembly or if requirements are more restrictive. The PolyPro by Duravent and In noFlue by Centrotherm venting system must also follow the uninsulated and unconditioned space criteria listed in table 16.

The ML296UHV can be installed as either a Non-Direct Vent or a Direct Vent gas central furnace.

NOTE - In Non‐Direct Vent installations, combustion air is taken from indoors or ventilated attic or crawlspace and flue gases are discharged outdoors. In Direct Vent installations, combustion air is taken from outdoors 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.

Regardless of the diameter of pipe used, the standard roof and wall terminations described in section Exhaust Piping Terminations should be used. Exhaust vent termination pipe is sized to optimize the velocity of the exhaust gas as it exits the termination. Refer to table 17.

In some applications which permit the use of several differ ent sizes of vent pipe, a combination vent pipe may be used. Contact Lennox' Application Department for assis tance in sizing vent pipe in these applications.

NOTE - The exhaust collar on all models is sized to ac commodate 2” Schedule 40 vent pipe. In horizontal ap plications, any transition to exhaust pipe larger than 2” must be made in vertical runs of the pipe. Therefore a 2” elbow must be added before the pipe is transitioned to any size larger than 2”. This elbow must be added to the elbow count used to determine acceptable vent lengths. Contact the Application Department for more information concerning sizing of vent systems which include multiple pipe sizes.

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 Centrotherm manufactured vent pipe and terminations as an option to PVC. When using the PolyPro InnoFlue

by Centrotherm venting system the vent pipe re

by DuraVent or

and

Page 24

Horizontal Installation Offset Requirements

Exhaust Pipe

Horizontal

12” Max.

Gas Furnace

NOTE - All horizontal runs of exhaust pipe must slope back to ward 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.

12” Min.

FIGURE 17

Page 25

MINIMUM VENT PIPE LENGTHS

ML296UHV

MODEL

045, 070, 090, 110

*Any approved termination may be added to the minimum length listed.

TABLE 13

MIN. VENT LENGTH*

15 ft. or

5 ft. plus 2 elbows or

10 ft. plus 1 elbow

Use the following steps to correctly size vent pipe diameter.

Piping Size Process

What is the

furnace capacity?

045, 070, 090,

110

Which style termination

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.

Desired pipe size?

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 18

IMPORTANT

Do not use screens or perforated metal in exhaust or intake terminations. Doing so will cause freeze-ups and may block the terminations.

Page 25

Page 26

Maximum Allowable Intake or Exhaust Vent Length in Feet

TABLE 14

NOTE - 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 - 4500 ft

Number Of 90°

Elbows Used

045 070 090 110 045 070 090 11 0 045 070 090 110

1 81 66 44 24 11 5 115 93 58 138 137 118 11 8

2 76 61 39 19 11 0 110 88 53 133 132 113 11 3

3 71 56 34 14 105 105 83 48 128 127 108 108

4 66 51 29

5 61 46 24 95 95 73 38 118 11 7 98 98

6 56 41 19 90 90 68 33 113 11 2 93 93

7 51 36 14 85 85 63 28 108 107 88 88

8 46 31

9 41 26 75 75 53 18 98 97 78 78

10 36 21 70 70 48 13 93 92 73 73

2” Pipe 2-1/2” Pipe 3” Pipe

Model Model Model

100 100 78 43 123 122 103 103

n/a

80 80 58 23 103 102 83 83

n/a

Standard Termination Elevation 4500 - 10,000 ft

Number Of 90°

Elbows Used

045 070 090 110 045 070 090 11 0 045 070 090 110

1 81 66 44

2 76 61 39 110 110 88 53 133 132 11 3 11 3

3 71 56 34 105 105 83 48 128 127 108 108

4 66 51 29 100 100 78 43 123 122 103 103

5 61 46 24 95 95 73 38 118 11 7 98 98

6 56 41 19 90 90 68 33 113 11 2 93 93

7 51 36 14 85 85 63 28 108 107 88 88

8 46 31

9 41 26 75 75 53 18 98 97 78 78

10 36 21 70 70 48 13 93 92 73 73

2” Pipe 2-1/2” Pipe 3” Pipe

Model Model Model

115 115 93 58 138 137 11 8 118

n/a

80 80 58 23 103 102 83 83

n/a

See concentric terminations next page.

Page 26

Page 27

Maximum Allowable Intake or Exhaust Vent Length in Feet

TABLE 14 Continued

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.

Concentric Termination at Elevation 0 - 4500 ft

Number Of 90°

Elbows Used

045 070 090 11 0 045 070 090 11 0 045 070 090 11 0

1 73 58 42 22 105 105 89 54 121 121 114 11 4

2 68 53 37 17 100 100 84 49 116 116 109 109

3 63 48 32 12 95 95 79 44 111 111 104 104

4 58 43 27

5 53 38 22 85 85 69 34 101 101 94 94

6 48 33 17 80 80 64 29 96 96 89 89

7 43 28 12 75 75 59 24 91 91 84 84

8 38 23

9 33 18 65 65 49 14 81 81 74 74

10 28 13 60 60 44 n/a 76 76 69 69

2” Pipe 2-1/2” Pipe 3” Pipe

Model Model Model

90 90 74 39 106 106 99 99

n/a

70 70 54 19 86 86 79 79

n/a

Concentric Termination Elevation 4501 - 10,000 ft

Number Of 90°

Elbows Used

045 070 090 11 0 045 070 090 11 0 045 070 090 11 0

1 73 58 42

2 68 53 37 100 100 84 49 11 6 116 109 109

3 63 48 32 95 95 79 44 111 111 104 104

4 58 43 27 90 90 74 39 106 106 99 99

5 53 38 22 85 85 69 34 101 101 94 94

6 48 33 17 80 80 64 29 96 96 89 89

7 43 28 12 75 75 59 24 91 91 84 84

8 38 23

9 33 18 65 65 49 14 81 81 74 74

10 28 13 60 60 44 n/a 76 76 69 69

2” Pipe 2-1/2” Pipe 3” Pipe

Model Model Model

105 105 89 54 121 121 114 114

n/a

70 70 54 19 86 86 79 79

n/a

Page 27

Page 28

Maximum Allowable Exhaust Vent Lengths With Furnace Installed in a Closet or Basement Using Ventilated

TABLE 15

Attic or Crawl Space For Intake Air in Feet

Standard Termination at Elevation 0 - 4500 ft

Number Of 90°

Elbows Used

045 070 090 110 045 070 090 11 0 045 070 090 110

1 71 56 34 14 100 100 78 43 11 8 11 7 98 98

2 66 51 29 9 95 95 73 38 11 3 11 2 93 93

3 61 46 24 4 90 90 68 33 108 107 88 88

4 56 41 19

5 51 36 14 80 80 58 23 98 97 78 78

6 46 31 9 85 75 63 18 93 92 73 73

7 41 26 4 70 70 48 13 88 87 68 68

8 36 21

9 31 16 60 60 38 3 78 77 58 58

10 26 11 55 55 33 n/a 73 72 53 53

2” Pipe 2-1/2” Pipe 3” Pipe

Model Model Model

85 85 63 28 103 102 83 83

n/a

65 65 43 8 83 82 63 63

n/a

Standard Termination Elevation 4500 - 10,000 ft

Number Of 90°

Elbows Used

045 070 090 110 045 070 090 11 0 045 070 090 110

1 71 56 34

2 66 51 29 95 95 73 38 113 11 2 93 93

3 61 46 24 90 90 68 33 108 107 88 88

4 56 41 19 85 85 63 28 103 102 83 83

5 51 36 14 80 80 58 23 98 97 78 78

6 46 31 9 85 85 53 18 93 92 73 73

7 41 26 4 70 70 48 13 88 87 68 68

8 36 21

9 31 16 60 60 38 3 78 77 58 58

10 26 11 55 55 33 n/a 73 72 53 53

2” Pipe 2-1/2” Pipe 3” Pipe

Model Model Model

100 100 78 43 118 11 7 98 98

n/a

65 65 43 8 83 82 63 63

n/a

Page 28

Page 29

TYPICAL EXHAUST AND INTAKE PIPE CONNECTIONS IN UPFLOW DIRECT OR

NON-DIRECT VENT APPLICATIONS

EXHAUST

2”

INTAKE

2”

EXHAUST INTAKE

TRANSITION

3”

*2”

2”

3”

TRANSITION

*2”

2”

DO NOT transition

from smaller to larger

pipe in horizontal runs

of exhaust pipe.

* When transitioning up in pipe size, use the shortest length of 2” PVC pipe possible.

FIGURE 19

2”

TYPICAL EXHAUST AND INTAKE PIPE CONNECTIONS IN HORIZONTAL DIRECT OR NON-DIRECT VENT

APPLICATIONS

12” max.

EXHAUST

2”

INTAKE

EXHAUST

*2”

(RIGHT HAND DISCHARGE SHOWN)

2”

3”

*2”

2”

TRANSITION

*2”

2”

3”

*2”

45°

MAX

2”

*2”

2”

SIDE VIEW

45°

MAX

DO NOT transition

from smaller to larger

pipe in horizontal runs

of exhaust pipe.

INTAKE

* When transitioning up in pipe size, use the shortest length of 2” PVC pipe possible.

FIGURE 20

Page 29

Page 30

Intake Piping

The ML296UHV 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 and guidelines listed in Combustion, Dilution and Ventilation Air section must be followed.

Follow the next two steps when installing the unit in Direct Vent applications, where combustion air is taken from outdoors and flue gases are discharged outdoors. The

provided air intake screen must not be used in direct vent applications (outdoors).

1 - Use transition solvent cement or a sheet metal screw

to secure the intake pipe to the inlet air connector.

2 - Route piping to outside of structure. Continue with

installation following instructions given in general guidelines 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

HORIZONTAL NON−DIRECT VENT APPLICATIONS

(Horizontal Right−Hand Air Discharge Application Shown)

PVC pipe

coupling

INTAKE

DEBRIS

SCREEN

(Provided)

NOTE - Debris screen may be positioned straight out (preferred) or with an elbow rotated to face down.

TYPICAL AIR INTAKE PIPE CONNECTIONS

UPFLOW NON−DIRECT

VENT APPLICATIONS

INTAKE

DEBRIS

SCREEN

(Provided)

NOTE - Debris screen and elbow may be rotated, so that screen may be positioned to face forward or to either side.

FIGURE 21

FIGURE 22

Follow the next two steps when installing the unit in Non‐ Direct Vent applications where combustion air is taken

from indoors or ventilated attic or crawlspace 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 21 or 22. 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 to either side in the upflow position, and either straight out or downward in the horizontal position.

The air intake piping must not terminate too close to the flooring or a platform. Ensure that the intake air inlet will not be obstructed by loose insulation or other items that may clog the debris screen.

2 - If intake air is drawn from a ventilated attic (figure 23)

or ventilated crawlspace (figure 24) 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 a sheet metal screw to secure the intake pipe to

the connector, if desired.

Page 30

Page 31

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 Attic and Outlet Air to Outside)

Roof Terminated

Exhaust Pipe

* 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.

(Inlet Air from Ventilated Crawlspace and Outlet Air to Outside)

Roof Terminated

Exhaust Pipe

EQUIPMENT IN CONFINED SPACE

Ventilation Louvers

12 in.(305mm) Above

*Intake Debris

Screen

(Provided)

Furnace

per 1.17kW) per

FIGURE 23

EQUIPMENT IN CONFINED SPACE

Inlet Air

(Minimum

attic floor)

General Guidelines for Vent Terminations

In Non‐Direct Vent applications, combustion air is taken from indoors or ventilated attic or crawlspace and the flue gases are discharged to the outdoors. The ML296UHV is then classified as a non‐direct vent, Category IV gas fur nace.

In Direct Vent applications, combustion air is taken from outdoors and the flue gases are discharged to the out doors. The ML296UHV 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 absence of local codes, refer to the current National Fuel Gas Code ANSI Z223-1/NFPA 54 in U.S.A., and current CSA-B149 Natural Gas and Propane Installation Codes in Canada for details.

Position termination according to location given in figure 26 or 27. 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 an outdoor AC 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.

Inlet Air

(Minimum

Ventilation

Louvers

(Crawl space)

Coupling or

3 in. to 2 in.

Transition

(Field Provided)

Furnace

12 in.(305mm)

Above crawl

space floor)

*Intake Debris Screen Provided)

* See table 15 for maximum vent lengths

NOTE-The inlet and outlet air openings shall each have a free area of at least one square inch per 4,000 Btu (645mm hour of the total input rating of all equipment in the enclosure.

per 1.17kW) per

FIGURE 24

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).

Page 31

Page 32

Maximum Allowable Exhaust Vent Pipe Length (in ft.)Without Insulation In Unconditioned Space For

TABLE 16

Winter Design Temperatures Two - Stage High Efficiency Furnace

Winter Design

Temperatures

32 to 21

(0 to -6)

°F (°C)

Vent Pipe

Diameter

045 070 090 110

PVC

PP PVC

2 in. 21 18 33 30 46 42 30 30

2-1/2 in. 16 N/A 26 N/A 37 N/A 36 N/A

Unit Input Size

PP PVC

3 in. 12 12 21 21 30 30 29 29

2 in 11 9 19 17 28 25 27 24

20 to 1

(-7 to -17)

2-1/2 in. 7 N/A 14 N/A 21 N/A 20 N/A

3 in. N/A N/A 9 9 16 16 14 14

2 in. 6 4 12 10 19 16 18 15

0 to -20

(-18 to -29)

2-1/2 in. N/A N/A 7 N/A 13 N/A 12 N/A

3 in. N/A N/A N/A N/A 8 8 7 7

1Refer to 99% Minimum Design Temperature table provided in the current edition of the ASHRAE Fundamentals Handbook.

Poly-Propylene vent pipe (PP) by Duravent and Centrotherm.

NOTE - Concentric terminations are the equivalent of 5' and should be considered when measuring pipe length. 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 figure25.

Conditioned

Space

Conditioned

Space

FIGURE 25

Pipe Insulation

Unconditioned

Space

Exhaust

Pipe

Intake

Pipe

Page 32

Page 33

VENT TERMINATION CLEARANCES

FOR NON-DIRECT VENT INSTALLATIONS IN THE US AND CANADA

INSIDE CORNER

DETAIL

Fixed

Closed

Operable

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

Vertical clearance to ventilated soffit

D =

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

Clearance under veranda, porch, deck or balcony

M =

In accordance with the current ANSI Z223.1/NFPA 54 Natural Fuel Gas Code

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 26

Fixed

Closed

AREA WHERE TERMINAL IS NOT PERMITTED

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.

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.”

Page 33

Page 34

VENT TERMINATION CLEARANCES

FOR DIRECT VENT INSTALLATIONS IN THE US AND CANADA

INSIDE CORNER

DETAIL

Fixed

Closed

Operable

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

Vertical clearance to ventilated soffit

D =

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 =

Clearance to mechanical air sup

ply inlet

L =

Clearance above paved sidewalk or

paved driveway located on public property

Clearance under veranda, porch, deck or balcony

M =

In accordance with the current ANSI Z223.1/NFPA 54 Natural Fuel Gas Code

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.

3 feet (.9m) above if within 10 feet

(3m) horizontally

* 7 feet (2.1m)

*12 inches (305mm)‡

FIGURE 27

Fixed

Closed

AREA WHERE TERMINAL IS NOT PERMITTED

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

* 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)‡

Page 34

Page 35

Details of Intake and Exhaust Piping Terminations for Direct Vent Installations

NOTE - In Direct Vent installations, combustion air is tak en from outdoors and flue gases are discharged to out doors.

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 28 through 35 show typical terminations.

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

28).

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.

NOTE - Care must be taken to avoid recirculation of exhaust back into intake pipe.

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.

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

FIGURE 28

Exiting Exhaust and Intake Vent

(different pressure zones)

Exhaust

Pipe

Furnace

(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

Furnace

(Minimum 12 in. 305 MM) above

grade or snow

FIGURE 30

TABLE 17

EXHAUST PIPE TERMINATION SIZE REDUCTION

ML296UHV

MODEL

*045 and 070

*090 2” (51MM)

110 2” (51MM)

Termination

Pipe Size

1-1/2” (38MM)

Inlet Air

accumulation

Page 35

Page 36

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.

*ML296UHV-045, -070 and -090 units with the flush mount termination must use the 1-1/2”accelerator supplied with the kit.

8. A multiple furnace installation may use a group of up to four terminations assembled together horizontally, as shown in figure 34.

9. A multiple furnace installation may use a group of up to four terminations assembled together horizontally, as shown in figure 34.

2” EXTENSION FOR 2” PVC PIPE1” EXTENSION FOR 3” PVC PIPE

FURNACE

4''

EXHAUST

PIPE

FURNACE

INTAKE

PIPE

GLUE EXHAUST

END FLUSH INTO

TERMINATION

FLAT SIDE

1-1/2” ACCELERATOR

FLUSH-MOUNT SIDE WALL TERMINATION

51W11 (US) or 51W12 (Canada)

FIGURE 31

1 1/2” (38mm) accelerator

EXHAUST

12” (305mm)

Minimum

Above Average

Snow

Accumulation

VENT

provided on 71M80 & 44W92

kits for ML296UHV045P24B,

070P24B & 070P36B

INTAKE

AIR

FLASHING

(Not Furnished)

SHEET METAL STRAP

(Clamp and sheet metal strap must be field installed to support the weight of the termination kit.)

CLAMP

FIELD-PROVIDED

REDUCER MAY BE REQUIRED

TO ADAPT LARGER VENT

PIPE SIZE TO TERMINATION

DIRECT VENT CONCENTRIC ROOFTOP TERMINATION

71M80, 69M29 or 60L46 (US)

44W92 or 44W93 (Canada)

FIGURE 32

FIELD-PROVIDED

REDUCER MAY BE REQUIRED

TO ADAPT LARGER VENT

PIPE SIZE TO TERMINATION

EXHAUST

OUTSIDE

WALL

INTAKE

AIR

VENT

INTAKE

AIR

CLAMP

(Not Furnished)

INTAKE

AIR

12” (305mm) Min.

above grade or

average snow accumulation.

GRADE

DIRECT VENT CONCENTRIC WALL TERMINATION

71M80, 69M29 or 60L46 (US)

44W92 or 44W93 (Canada)

FIGURE 33

EXHAUST

VENT

INTAKE

AIR

Inches (MM)

optional intake elbow

5”

(127MM)

18” MAX. (457MM)

EXHAUST VENT

INTAKE

AIR

12”

(305MM)

5-1/2”

(140mm)

Front View

12” (305MM) Min.

above grade or

average snow accumulation.

Side View

OPTIONAL VENT TERMINATION FOR MULTIPLE UNIT

INSTALLATION OF DIRECT VENT WALL TERMINATION KIT

(30G28 or 81J20)

FIGURE 34

ML296UHV DIRECT VENT APPLICATION

USING EXISTING CHIMNEY

STRAIGHT-CUT OR

3”-8”

(76MM-203MM)

ANGLE-CUT IN DIRECTION

OF ROOF SLOPE *

8” - 12”

(203MM - 305MM)

Minimum 12” (305MM)

above chimney top

plate or average snow

accumulation

NOTE - Do not discharge exhaust gases directly into any chimney or vent stack. If vertical discharge through an existing unused chimney or stack is required, insert pip ing inside chimney until the pipe open end is above top of chimney and terminate as illustrated. In any exterior portion of chimney, the exhaust vent must be insulated.

INTAKE PIPE

INSULATION (optional)

SHEET

METAL TOP

PLATE

INSULATE

TO FORM

SEAL

SHOULDER OF FITTINGS

PROVIDE SUPPORT

OF PIPE ON TOP PLATE

3” - 8”

(76MM-

203MM)

FIGURE 35

EXHAUST

VENT

ALTERNATE

INTAKE PIPE

EXTERIOR

PORTION OF

CHIMNEY

Page 36

Page 37

NOTE − FIELD−PROVIDED

REQUIRED TO ADAPT

LARGER VENT PIPE SIZE

* WALL

SUPPORT

REDUCER MAY BE

TO TERMINATION

STRAIGHT

Intake Elbow

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

APPPLICATION

D− Maximum exhaust

pipe length

EXTENDED

APPLICATION

E− Maximum wall support

distance from top of each

pipe (intake/exhaust)

See maximum allowable venting tables for venting lengths with this arrangement.

* Use wall support every 24” (610 mm). Use two wall supports if extension is greater than 24” (610 mm) but less than 48” (1219 mm).

NOTE − One wall support must be within 6” (152 mm) from top of each pipe (intake and exhaust) to prevent movement in any direction.

ALTERNATE TERMINATIONS (TEE & FORTY−FIVE DEGREE ELBOWS ONLY)

FIELD FABRICATED WALL TERMINATION

Exhaust

12”

Intake Elbow

The exhaust termination tee should be connected to the 2” or 3” PVC flue pipe as shown in the illustration. In horizontal tee applications there must be be a minimum of 3 ft away from covered patios or any living ares and

cannot be within 3 ft of a window. Do not use an accelerator in applications that include an exhaust termination tee. The accelerator is not required.

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.

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.

12”

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)

Front View of

Intake and Exhaust

Intake

Exhaust

2” (51mm)

Vent Pipe

12” (305 mm)

6” (152 mm)

2” (51MM)

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

12” (305 mm)

6” (152 mm)6” (152 mm)

8” (203 mm)8” (203 mm)

6” (152 mm)6” (152 mm)

20” (508 mm)

6” (152 mm)

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 37

Page 38

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 37 and 38 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 velocity required to move the exhaust gases away from the building.

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.

ML296UHV NON-DIRECT VENT APPLICATION

USING EXISTING CHIMNEY

STRAIGHT-CUT OR

ANGLE-CUT IN DIRECTION

OF ROOF SLOPE

Minimum 12” (305MM)

above chimney top

plate or average snow

accumulation

SHEET

METAL TOP

PLATE

INSULATE

TO FORM

SEAL

SHOULDER OF FITTINGS

PROVIDE SUPPORT

OF PIPE ON TOP PLATE

EXTERIOR

PORTION OF

CHIMNEY

12” (305MM)

ABOVE AVE.

SNOW

ACCUMULATION

3” (76MM) OR

2” (51MM) PVC

PROVIDE SUPPORT

FOR EXHAUST LINES

NON-DIRECT VENT ROOF TERMINATION KIT

(15F75 or 44J41)

UNCONDITIONED

ATTIC SPACE

FIGURE 37

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.

Crawl Space and Extended Horizontal Venting

Lennox provides kit 51W18 to install 2” or 3” PVC exhaust piping through the floor joists and into the the crawl space. See figure 39.

This kit can also be used as a supplemental drain for instal lations with condensate run back in the vent pipe (ie. long horizontal runs, unconditioned spaces, etc.).

NOTE - Do not discharge exhaust gases directly into any chimney or vent stack. If ver tical discharge through an existing unused chimney or stack is required, insert piping inside chimney until the pipe open end is above top of chimney and terminate as illus trated. In any exterior portion of chimney, the exhaust vent must be insulated.

FIGURE 38

Venting In A Crawl Space

Basement Floor

KIT 51W81

(USA) KIT 51W81 (CANADA)

FIGURE 39

Page 38

Page 39

Condensate Piping

This unit is designed for either right‐ or left‐side exit of con densate piping in upflow applications. In horizontal applica tions, the condensate trap must extend below the unit. An 8” service clearance is required for the condensate trap. Refer to figures 40 and 42 for condensate trap locations. Figure 48 shows trap assembly using 1/2” PVC or 3/4” PVC.

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.

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 - Use a large flat head screw driver or a 1/2” drive socket

extension and remove plug (figure 40) from the cold end header box at the appropriate location on the side of the unit. Install provided 3/4 NPT street elbow fitting into cold end header box. Use Teflon tape or appropri ate pipe dope.

NOTE - Cold end header box drain plugs are factory in stalled. Check the unused plug for tightness to prevent leakage.

3 - Install the cap over the clean out opening at the base

of the trap. Secure with clamp. See figure 48.

4 - Install drain trap using appropriate PVC fittings, glue

all joints. Glue the provided drain trap as shown in fig ure 48. Route the condensate line to an open drain.

Condensate line must maintain a 1/4” downward slope from the furnace to the drain.

5 - Figures 43 and 44 show the furnace and evaporator

coil using a separate drain. If necessary the conden sate line from the furnace and evaporator coil can drain together. See figures 45, 46 and 47. Upflow furnace (figure 46) - In upflow furnace applica tions the field provided vent must be a minimum 1” to a maximum 2” length above the condensate drain outlet connection. Any length above 2” may result in a flooded heat exchanger if the combined primary drain line were to become restricted. Horizontal furnace (figure 47) - In horizontal furnace applications the field provided vent must be a mini mum 4” to a maximum 5” length above the condensate drain outlet connection. Any length above 5” may re sult in a flooded heat exchanger if the combined pri mary drain line were to become restricted.

CONDENSATE TRAP AND PLUG LOCATIONS

(Unit shown in upflow position)

Trap

(same on

right side)

1-1/2 in.

Plug

(same on left side)

NOTE - In upflow applications where side return air filter is installed on same side as the conden sate trap, filter rack must be installed beyond condensate trap or trap must be re-located to avoid interference.

FIGURE 40

NOTE - In horizontal applications it is recommended to install a secondary drain pan underneath the unit and trap assembly.

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.

Field Provided Drain Components

Elbow

Barbed Fitting

Tubing

Hose Clamp

FIGURE 41

Page 39

Page 40

CAUTION

Do not use copper tubing or existing copper conden sate lines for drain line.

6 - If unit will be started immediately upon completion of

installation, prime trap per procedure outlined in Unit Start-Up section.

CONDENSATE TRAP LOCATIONS

(Unit shown in upflow position with remote trap)

FieldProvidedVent

Min. 1” AboveCondensate

Drain

Connection

1”

Min.

2” Max.

*5’ max.

PVCPipeOnly

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. Heating cable kit is available 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.

ML296UHV With Evaporator Coil Using A Separate Drain

Evaporator drain

line required

(Trap at coil is optional)

Field Provided Vent (1” min. 2” max. above condensate connection)

Trap can be installed a

maximum 5' from furnace

To Drain

*Piping from furnace must slope down a minimum of 1/4” per ft. toward trap.

FIGURE 42

ML296UHV with Evaporatoir Coil Using a Separate Drain

(Unit shown in horizontal left-hand discharge position)

Evaporator

Coil

Condensate

DrainConnection

Condensate

DrainConnection

FIGURE 43

Field Provided Vent (4” min. to 5” max. above condensate connection)

4”min

5”max

5’ max.

PVC Pipe Only

Drain

Pan

(Trap at coil is optional)

Piping from furnace and evaporator coil must slope down a minimum 1/4” per ft. toward trap

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.

Page 40

Page 41

Condensate Trap With Optional Overflow Switch

From Evaporator Coil

Optional

Field Provided Vent

1” min. 2” max. above

condensate drain.

FurnaceCondensate

Drain

Connection

ML296UHV with Evaporator Coil Using a Common Drain

(Trap at coil is optional)

(1” min. to 2”Max.above

condensatedrain connection)

Condensate

Drain

Connection

Evaporator drain

line required

Drain

Pan

FIGURE 45

FIGURE 46

ML296UHV with Evaporator Coil Using a Common Drain

(Unit shown in horizontal left−hand discharge position)

Evaporator

Coil

4”min

5”max

5’ max.

PVC Pipe Only

CondensateDrain

Connection

(Trap at coil is optional)

Piping from furnace and evaporator coil must slope down a minimum 1/4” per ft. toward trap

FIGURE 47

(4” min. to 5” Max.above

condensatedrain

connection)

Page 41

Page 42

TRAP / DRAIN ASSEMBLY USING 1/2” PVC OR 3/4” PVC

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)

Trap

Optional Drain Piping FromTrap

Drain Assembly for 1/2 inch Drain Pipe

1/2 inch PVC Pipe

(Not Furnished)

90° Elbow

1/2 inch PVC

(Not Furnished)

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

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)

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 Unit

90° Elbow

3/4 inch PVC

(Not Furnished)

Drain

DrainTrap Assembly

(Furnished)

(178)

Drain Trap Clean Out

90° Elbow

3/4 inch PVC

(Not Furnished)

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

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

Drain

FIGURE 48

Page 42

Page 43

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 with

in range listed on the nameplate. If not, consult th e pow e r company and have voltage condition corrected be fore 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 fur

nace area for gas. Be sure to smell next to the floor be cause some gas is heavier than air and will settle on the floor.

The gas valve on the ML296UHV is equipped with a gas control 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 at tempted repair may result in a fire or explosion.

Placing the furnace into operation:

ML296UHV units are equipped with a SureLight system. Do not

attempt to manually light burners on this

ignition

furnace. 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 SureLight 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 49)

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 49. 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 49.

WHITE RODGERS GAS VALVE

MANIFOLD

PRESSURE POST

INLET PRESSURE

POST

GAS VALVE SHOWN IN OFF POSITION

HIGH FIRE ADJUSTMENT

SCREW

(under cap)

LOW FIRE ADJUSTMENT

SCREW

(under cap)

FIGURE 49

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 43

Page 44

IV-HEATING SYSTEM SERVICE CHECKS

A-CSA Certification

All units are CSA design certified without modifications. Refer to the ML296UHV(X) Installation Instruction.

B-Gas Piping

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.

WARNING

Do not exceed 600 in-lbs (50 ft-lbs) torque when attaching the gas piping to the gas valve.

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

through Lennox under part number 31B2001. See Corp. 8411-L10, for further details.

Do not use matches, candles, flame or any other source of ignition to check for gas leaks.

D-Testing Gas Supply Pressure

An inlet pressure post located on the gas valve provides ac cess to the supply pressure. See figure 49. Back out the 3/32 hex screw one turn, connect a piece of 5/16 tubing and connect to a manometer to measure supply pressure. See table 21 for supply line pressure.

E-Check Manifold Pressure

NOTE - Pressure test adapter kit (10L34) is available from Lennox to facilitate manifold pressure measurement.

A manifold pressure post located on the gas valve provides access to the manifold pressure. See figure 49. Back out the 3/32 hex screw one turn, connect a piece of 5/16 tubing and connect to a manometer to measure manifold pres sure. To correctly measure manifold pressure, the differential pressure between the positive gas manifold and the nega tive burner box must be considered.

IMPORTANT

For safety, connect a shut‐off valve between the ma nometer and the gas tap to permit shut off of gas pressure to the manometer.

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 0.5 psig (14” W.C.). See figure 50. If the pressure is greater than 0.5psig (14”W.C.), use the manual shut-off valve before pressure testing to isolate fur nace from gas supply.

GAS PIPING TEST PROCEDURE

MANUAL MAIN SHUT-OFF VALVE

WILL NOT HOLD TEST PRESSURE

IN EXCESS OF 0.5 PSIG (14”W.C.)

1/8 NPT PLUG

GAS VALVE

FIGURE 50

When checking piping connections for gas leaks, use pre ferred means. Kitchen detergents can cause harmful corro sion on various metals used in gas piping. Use of a specialty Gas Leak Detector is strongly recommended. It is available

CAP

1 - Connect the test gauge positive side “+“ to manifold

pressure tap on gas valve as noted above.

2 - Tee into the gas valve regulator vent hose and connect

to test gauge negative “-”.

3 - Ignite unit on low fire and let run for 5 minutes to allow

for steady state conditions.

4 - After allowing unit to stabilize for 5 minutes, record low

fire manifold pressure and compare to value given in table 21. If necessary, make adjustment. Figure 49 shows location of low fire adjustment screw.

5 - Repeat on high fire and compare to value given in

table 21. If necessary, make adjustment. Figure 49 shows location of high fire adjustment screw.

6 - Shut unit off and remove manometer as soon as an ac

curate reading has been obtained.

7 - Start unit and perform leak check. Seal leaks if found.

The gas valve is factory set and should not require adjust ment. All gas valves are factory regulated.

F- Proper Gas Flow (Approximate)

Furnace should operate at least 5 minutes before check ing gas flow. Determine time in seconds for two revolu tions of gas through the meter. (Two revolutions assures a more accurate time.) Divide by two and compare to time in table 18 below. If manifold pressure matches table 21 and rate is incorrect, check gas orifices for proper size and restriction.

Page 44

Page 45

NOTE- To obtain accurate reading, shut off all other gas appliances connected to meter.

TABLE 18

GAS METER CLOCKING CHART

Seconds for One Revolution

ML296

Unit

Natural LP

1 cu ft

Dial

2 cu ft

Dial

1 cu ft

Dial

2 cu ft

DIAL

-045 80 160 200 400

-70 55 110 136 272

-90 41 82 102 204

-110 27 54 68 136

Natural-1000 btu/cu ft LP-2500 btu/cu ft

IMPORTANT

For safety, shut unit off and remove manometer as soon as an accurate reading has been obtained. Take care to replace pressure tap plug.

G- Proper Combustion

Furnace should operate minimum 15 minutes with correct manifold pressure and gas flow rate before checking com bustion. See sections E- and F-. Take combustion sample beyond the flue outlet. Table 19 shows acceptable com bustions. The maximum carbon monoxide reading

should not exceed 100 ppm.

TABLE 19

EL296 Model

CO2%

For Nat

Low Fire High Fire Low Fire High Fire

CO2%

For L.P

045 5.4 - 6.4 7.5 - 8.5 6.4 - 7.4 8.8 - 9.8

070 5.3 - 6.3 7.4 - 8.4 6.3 - 7.3 8.7 - 9.7

090 5.8 - 6.8 7.6 - 8.6 6.8 - 7.8 8.9 - 9.9

110 6.1 - 7.1 8.0 - 9.0 7.1 - 8.1 9.3 - 10.3

The maximum carbon monoxide reading should not exceed 100ppm.

H- High Altitude

The manifold pressure, gas orifice and pressure switch may require adjustment or replacement to ensure proper operation at higher altitudes. See table 20 for gas conver sion and pressure switch kits. See table 21 for manifold pressures

TABLE 20

LP/Propane Conversion Kit and Pressure Switch Requirements at Varying Altitudes

ML296

Unit

-045

Natural to

LP/Propane

0 - 7500 ft

(0 - 2286m)

High Altitude

Natural Burner

Orifice Kit

7501 - 10,000 ft

(2286 - 3038m)

High Altitude

LP/Propane Burner

Orifice Kit

7501 - 10,000 ft

(2286 - 3038m)

High Altitude Pressure Switch

4501 - 7500 ft

(1373 - 2286m)

7501 -10,000 ft (2286 - 3048m)

14A47 14A50

-070 14A54 14A53

-090 14A57 14A54

*11K51 73W37 *11K46

-110 14A46 14A51

* 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).

TABLE 21

Manifold Pressure Settings

Supply Line

Pressure

in. w.g.

0 - 10000 ft.

Min Max

ML296

Unit

All

Sizes

Manifold Pressure in. wg.

Gas

Natural 1.7 3.5 1.6 3.3 1.5 3.2 1.5 3.1 1.7 3.5 4.5 13.0

LP/

propane

0-4500 ft. 4501-5500 ft. 5501-6500 ft. 6501 - 7500ft. 7501 - 10000ft.

Low Fire

4.9 10.0 4.6 9.4 4.4 9.1 4.3 8.9 4.9 10.0 11.0 13.0

High

Fire

Low

Fire

High

Fire

Low Fire

High

Fire

Low Fire

High

Fire

Low Fire

High

Fire

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.

Page 45

Page 46

I- Proper Ground and Voltage

A poorly grounded furnace can contribute to premature ig nitor failure. Use the following procedure to check for ground and voltage to the integrated control. 1 - Measure the AC voltage between Line Neutral (spade

terminals) and “C” terminal (low voltage terminal block) on the integrated control. See figure 51. A wide variation in the voltage between Line Neutral and “C” as a function of load indicates a poor or partial ground. Compare the readings to the table below. If the read ings exceed the maximum shown in table 1, make re pairs before operating the furnace.

2 - In addition, measure the AC voltage from Line Hot to

Line Neutral (spade terminals) on the integrated con trol. See figure 51. This voltage should be in the range of 97 to 132 Vac

TABLE 22

Furnace Status

Power On Furnace Idle 0.3 2

CAI / Ignitor Energized 0.75 5

Indoor Blower Energized Less than 2 10

Measurement VAC

Expected Maximum

CHECK VOLTAGE BETWEEN LINE NEUTRAL

AND LOW VOLTAGE “C” TERMINAL

CHECK VOLTAGE BETWEEN LINE HOT

AND LINE NEUTRAL

W1 W2 GY2Y1

RDHLODS

FIGURE 51

Page 46

Page 47

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 position, 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 (Figure 52)

Temperature rise for ML296UHV units depends on unit in put, blower speed, blower horsepower and static pressure as marked on the unit rating plate. The blower speed must be set for unit operation within the range of “TEMP. RISE °F” listed on the unit rating plate.

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. For heating speed (second

stage heat speed) external static pressure drop must

not be more than 0.8” W.C. For cooling speed (second

stage cool speed) external static pressure drop must

not be more than 1.0” W.C.

4 - Seal the hole when the check is complete.

EXTERNAL STATIC PRESSURE

Supply Duct Static ________

Return Duct Static + _____

Total Duct Static = ________(dry coil)

Supply Air

TEMPERATURE RISE

Supply Duct Temperature ________

Return Duct Temperature

Temperature Rise = ________

FIGURE 52

C-External Static Pressure

1 - Tap locations shown in figure 53.

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 discharge (supply) side of the system. On ducted sys tems, connect the other end of manometer to the return duct as above.

_____

SUPPLY

AIR

Temperatures

RETURN AIR

Duct Static

Return Air

FIGURE 53

VI-MAINTENANCE

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.

Page 47

Page 48

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 23 lists recommended filter sizes.

IMPORTANT

If a highefficiency filter is being installed as part of this system to ensure better indoor air quality, the fil ter must be properly sized. Highefficiency filters have a higher static pressure drop than standardef 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 ACC002 (August 2000).

TABLE 23

Furnace

Cabinet Width

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).

3 - Check amp-draw on the blower motor.

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.

Minimum Filter Size

16 x 25 x 1 (1)

Condensate Hose Screen (Figure 54)

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 54

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 the burner box cover (if equipped) and remove gas valve/manifold assembly.

5 - Remove sensor wire from sensor. Disconnect 2‐pin

plug from the ignitor. 6 - Disconnect wires from flame roll-out switches. 7 - Disconnect combustion air intake pipe. It may be nec

essary to cut the existing pipe to remove burner box

assembly. 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 - Loosen the clamps to the flexible exhaust coupling. 10 - Disconnect condensate drain line from the cold end

header box. 11 - Disconnect condensate drain tubing from flue collar.

Remove screws that secures the flue collar into place.

Remove flue collar. It may be necessary to cut the exit

ing exhaust pipe for removal of the fitting. 12 - Mark and disconnect all combustion air pressure tub

ing from cold end header collector box. 13 - Mark and remove wires from pressure switch assemb

ly. Remove the assembly. Keep tubing attached to

pressure switches. 14 - 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. 15 - Disconnect the condensate drain line. 16 - Remove cold end header box.

Page 48

Page 49

17 - Remove electrical junction box from the side of the fur

nace.

18 - 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. 19 - Remove the primary limit from the vestibule panel. 20 - Remove two screws from the front cabinet flange at

the blower deck. Spread cabinet sides slightly to allow

clearance for removal of heat exchanger. 21 - 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. 22 - Back wash heat exchanger with soapy water solution

or steam. If steam is used it must be below 275°F

(135°C) .

23 - Thoroughly rinse and drain the heat exchanger. Soap

solutions can be corrosive. Take care to rinse entire

assembly. 24 - Reinstall heat exchanger into cabinet making sure that

the clamshells of the heat exchanger assembly is en

gaged properly into the support bracket on the blower

deck. Remove the indoor blower to view this area

through the blower opening. 25 - Re‐secure the supporting screws along the vestibule

sides and bottom to the cabinet. 26 - Reinstall cabinet screws on front flange at blower

deck. 27 - Reinstall the primary limit on the vestibule panel. 28 - Route heating component wiring through hole in blow

er deck and reinsert strain relief bushing. 29 - Reinstall electrical junction box. 30 - Reinstall the cold end header box. 31 - Reinstall the combustion air inducer. Reconnect the

plug to the wire harness. 32 - Reinstall pressure switches and reconnect pressure

switch wiring. 33 - Carefully connect combustion air pressure switch

tubing from pressure switches to proper ports on

cold end header collector box. 34 - Reconnect condensate drain line to the cold end

header box. 35 - Use securing screws to reinstall flue collar to the top

cap on the furnace. Reconnect exhaust piping and ex

haust drain tubing. 36 - Replace flexible exhaust adapter on combustion air in

ducer and flue collar. Secure using two existing hose

clamps. 37 - Reinstall burner box assembly in vestibule area. Se

cure burner box assembly to vestibule panel using

four existing screws. Make sure burners line up in

center of burner ports

38 - Reconnect flame roll-out switch wires. 39 - Reconnect sensor wire and reconnect 2-pin plug from

ignitor.

40 - Reinstall gas valve manifold assembly. Reconnect

gas supply line to gas valve. 41 - Reconnect the combustion air intake pipe. 42 - Reinstall burner box cover. 43 - Reconnect wires to gas valve. 44 - Replace the blower compartment access panel. 45 - Reconnect gas supply piping. Turn on power and gas

supply to unit. 46- Follow lighting instructions on unit nameplate to light

and operate furnace for 5 minutes to ensure the fur

nace is operating properly. 47- Check all piping connections, factory and field, for gas

leaks. Use a leak detecting solution or other preferred means.

48- Replace heating compartment access panel.

CAUTION

Some soaps used for leak detection are corrosive to certain metals. Carefully rinse piping thoroughly af ter leak test has been completed. Do not use matches, candles, flame or other sources of ignition to check for gas leaks.

Cleaning the Burner Assembly (if needed)

1 - Turn off electrical and gas power supplies to furnace.

Remove upper and lower furnace access panels. 2 - Disconnect the wires from the gas valve. 3 - Remove the burner box cover (if equipped). 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 wires from flame rollout switches. 6 - Disconnect combustion air intake pipe. It may be nec

essary to cut the existing pipe to remove burner box

assembly. 7 - Remove four screws which secure burner box assem

bly to vest panel. Remove burner box from the unit. 8 - 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. 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 - Reconnect the sensor wire and reconnect the 2-pin

plug to the ignitor wiring harness. Reconnect wires to

flame rollout switches. 11 - Reinstall the gas valve manifold assembly. Reconnect

the gas supply line to the gas valve. Reinstall the burn

er box cover. 12 - Reconnect wires to gas valve. 13 - Replace the blower compartment access panel. 14 - Refer to instruction on verifying gas and electrical con

nections when re-establishing supplies. 15 - 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. 16 - Replace heating compartment access panel.

Page 49

Page 50

VII- Wiring and Sequence of Operation

Page 50

Page 51

On a call for heat from the room thermostat, the control board performs a 1 second self check. Upon confirmation that the pressure switch contacts are in an open position, the control energizes the combustion blower on high speed. The control then checks for adequate combustion air by making sure the low-fire pressure switch contacts are closed.

The igniter energizes and is allowed to warm up for 20 sec onds before the gas valve energizes on 1st stage and burn ers ignite. 45 seconds after the control confirms ignition has occurred, the control drops the combustion blower to low speed.

The circulating blower ramps up to 50% of 1st stage heat speed and operates at that speed for one minute (including ramp up time), then at 75% of 1st stage heat speed for an additional minute. After that, the circulating blower oper ates at full 1st stage heat speed until either the heat call is satisfied or the thermostat initiates a call for 2nd stage heat. On a call for 2nd stage heat, the control energizes the circu lating air blower on full CFM 2nd stage heat.

If the automatic heat staging option is being used the fur nace does not switch to 2nd stage heat in response to a call from the thermostat but instead operates at 1st stage heat for the duration of the selected time before automatically switching to 2nd stage heat.

When the call for heat is satisfied, the gas valve and com bustion air blower shut down. The control board shuts off the gas valve and runs the combustion blower for an addi tional 15 seconds. The circulating air blower continues to run for 2 minutes at 82% of the selected heating speed (low fire or high fire) before ramping down.

In the event the unit loses ignition, the control will attempt to recycle up to five times before it goes into a 1 hour lockout. Lockout may be manually reset by removing power from the control for more than 1 second or removing the thermo stat call for heat for more than 3 seconds.

If during a heating cycle the limit control senses an abnor mally high temperature and opens, the control board deenergizes the gas valve and the combustion blower while the circulating blower ramps up to 2nd stage heat speed. The circulating blower remains energized until the limits are closed.

Fan On

When the thermostat is set for continuous fan operation and there is no demand for heating or cooling, a call for fan closes the R to G circuit and the circulating blower motor runs at50% of the selected cooling CFM until switched off. When the call for fan is turned off, the control de-energizes the circulating blower.

Cooling

The unit is set up at the factory for single stage cooling. For two stage cooling operation, clip the jumper wire located between the Y to Y2 terminals on the integrated ignition/ blower control board. If the active dehumidification feature is enabled, the circulating blower runs at 70% of the se lected cooling speed as long as there is a call for dehumidi fication.

WARNING

The system must not be in either the passive or ac tive dehumidification mode when charging a cooling system.

Single Stage Cooling

A call for cooling from the thermostat closes the R to Y cir cuit on the integrated ignition/blower control board. The control waits for a 1-second delay before energizing the cir culating blower to 82% of the selected cooling CFM (pas sive dehumidification mode). After 7.5 minutes, the circu lating blower automatically ramps up to 100% of the se lected cooling airflow. When the call for cooling is satisfied, the circulating blower ramps back down to 82% of the se lected cooling airflow for 1 minute, then shuts off.

Two-Stage Cooling

A call for 1st stage cooling from the thermostat closes the R to Y circuit on the control board. The control waits for a 1second delay before energizing the circulating blower. The blower motor runs at 57% of the selected air flow for the first

7.5 minutes of the 1st stage cooling demand (passive de humidification mode). After 7.5 minutes, the blower motor runs at 70% of the selected cooling air flow until 1st stage cooling demand is satisfied.

A call for 2nd stage cooling from the thermostat closes the R to Y2 circuit on the control board. The blower motor ramps up to 100% of the selected cooling air flow. When the demand for cooling is met, the blower ramps down to Y1 until satisfied, then ramps down to 57% for 1 minute, then turns off.

Heat Pump

For heat pump operation, clip the jumper wire located bel low the O terminal on the integrated ignition/blower control board. In heat pump mode, a call for heat will result in the circulating air blower operating at the selected cooling air flow after a brief ramp-up period.

Page 51

Lennox ML296UHV(X), ML296UH045XV36B, ML296UH070XV36B Series Manual

Specifications and Main Features

Frequently Asked Questions

User Manual

SPECIFICATIONS

BLOWER DATA