Lennox International Inc. AV-C, ML180UH User Manual

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INSTALLATION

 2011 Lennox Industries Inc.

Dallas, Texas, USA

INSTRUCTIONS

ML180UH

MERIT® SERIES GAS FURNACE UPFLOW / HORIZONTAL AIR DISCHARGE

506816−01 06/2011 Supersedes 506778−01

Litho U.S.A.

THIS MANUAL MUST BE LEFT WITH THE

HOMEOWNER FOR FUTURE REFERENCE

This is a safety alert symbol and should never be ignored. When you see this symbol on labels or in manuals, be alert to the potential for personal injury or death.

WARNING

Improper installation, adjustment, alteration, service or maintenance can cause property damage, personal injury or loss of life. Installation and service must be performed by a licensed professional installer (or equivalent), service agency or the gas supplier.

AIR FLOW

HORIZONTAL LEFT

UPFLOW

AIR FLOW

HORIZONTAL RIGHT

Table of Contents

Unit Dimensions 2. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Parts Arrangement 3. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

ML180UH Gas Furnace 4. . . . . . . . . . . . . . . . . . . . . . . . . .

Shipping and Packing List 4. . . . . . . . . . . . . . . . . . . . . . . .

Safety Information 4. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Use of Furnace as a Construction Heater 5. . . . . . . . . . .

General 5. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Combustion, Dilution & Ventilation Air 6. . . . . . . . . . . . . .

Setting Equipment 9. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Filters 12. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Duct System 12. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Venting 13. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

CAUTION

As with any mechanical equipment, personal injury can result from contact with sharp sheet metal edges. Be careful when you handle this equipment.

Gas Piping 23. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Electrical 25. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Integrated Control 28. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Unit Start−Up 29. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Gas Pressure Adjustment 30. . . . . . . . . . . . . . . . . . . . . . .

High Altitude 30. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Proper Combustion 30. . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Other Unit Adjustments 31. . . . . . . . . . . . . . . . . . . . . . . . . .

Blower Performance Data 33. . . . . . . . . . . . . . . . . . . . . . .

Service 35. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Planned Service 38. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Repair Parts List 38. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Integrated Control Diagnostic Codes 39. . . . . . . . . . . . . .

Troubleshooting 40. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

06/11

*2P0611*

Page 1

506816−01

*P506816-01*

Unit Dimensions − inches (mm)

NOTE − 60C and 60D units that require air volumes

over 1800 cfm (850 L/s) must have one of the following:

1. Single side return air with transition to accommodate 20 x 25 x 1 in. (508 x 635 x 25 mm) cleanable air filter. (Required to maintain proper air velocity.)

2. Single side return with optional return air base.

3. Bottom return air.

4. Return air from both sides.

5. Bottom and one side return air.

See Blower Performance Tables for additional information.

Flue outlet may be horizontal but furnace must be

vented vertically

Optional external side return air filter kit cannot be used

with the optional RAB Return Air Base.

9/16 (14)

OPTIONAL

EXTERNAL

SIDE RETURN

AIR FILTER KIT

(Either Side)

(838)

FLUE OUTLET

(Top)

OPTIONAL

EXTERNAL

SIDE RETURN

AIR FILTER KIT

(Either Side)

3/4(19)

Front Panel

3 (76) Right

6−3/4 (171) Left

9−1/8 (232) Right

8−5/8 (219) Left

5−3/8 (137) Right

1−9/16 (40) Left

3−1/8 (79)

23−3/4

TOP VIEW

3−1/4 (83)

FLUE OUTLET

(Either Side)

ELECTRICAL INLET

(Either Side)

GAS PIPING INLET

(Either Side)

SUPPLY AIR

OPENING

(603)

(635)

27−3/4

(705)

19−7/16

(494)

9/16

(14)

3/4

(19)

Bottom Return

FRONT VIEW

ML180UH Model No.

045P24A 045P36A 070P24A 070P36A

090P36B 090P48B

110P48C 110P60C

135P60D

Air Opening

3/4

(19)

14−3/4

(375)

5/8

(16)

(406)

ELECTRICAL INLET (Either Side)

(Either Side)

3−1/4

(83)

(584)

Side Return Air Opening (Either Side)

23−1/2

(597)

Bottom Return

Air Opening

(356)

1−15/16 (49)

1−1/2

(38)

SIDE VIEW

A B C D

in. mm in. mm in. mm in. mm

14−1/2 368 13−3/8 340 13 330 4−3/4 121

17−1/2 446 16−3/8 416 16 406 6−1/4 159

21 533 19−7/8 504 19−1/2 495 8 203

24−1/2 622 23−3/8 546 23 584 9−3/4 248

Page 2

Parts Arrangement

Combustion Air Inducer

Pressure Switch

Burner Box

(includes sensor, ignitor

and rollout switches)

Gas Valve

Make−Up Box

Heat Exchanger

Upper Access Panel

Blower Access Panel

Primary Limit

(under combustion air inducer)

Capacitor

(includes integrated control,

Control Box

interlock switch and transformer)

Secondary Limits

Blower Assembly

FIGURE 1

Page 3

ML180UH Gas Furnace

The ML180UH unit is shipped ready for installation in the upflow or horizontal right position (for horizontal left position the combustion air pressure switch must be moved). The furnace is shipped with the bottom panel in place. The bottom panel must be removed if the unit is to be installed in a horizontal application. The panel may also be removed in upflow applications.

Shipping and Packing List

Package 1 of 1 contains

1 − Assembled ML180UH unit 1 − Bag assembly containing the following:

2 − Screws 1 − Snap bushing 1 − Snap plug 1 − Wire tie 1 − Vent warning label 1 − Owner’s manual and warranty card

The following items may be ordered separately: 1 − Thermostat 1 − Suspension kit (for horizontal installations) 1 − Propane/LP changeover kit 1 − Return air base 1 − High altitude kit 1 − Side filter kit

Check equipment for shipping damage. If you find any damage, immediately contact the last carrier.

Safety Information

DANGER

Danger of explosion.

There are circumstances in which odorant used with LP/propane gas can lose its scent. In case of a leak, LP/propane gas will settle close to the floor and may be difficult to smell. An LP/propane leak detector should be installed in all LP applications.

WARNING

CAUTION

As with any mechanical equipment, personal injury can result from contact with sharp sheet metal edges. Be careful when you handle this equipment.

Certifications

ML180UH units are CSA International certified to ANSI Z21.47.

In the USA, installation of gas furnaces must conform with local building codes. In the absence of local codes, units must be installed according to the current National Fuel Gas Code (ANSI-Z223.1). The National Fuel Gas Code is available from the following address:

American National Standards Institute, Inc. 11 West 42nd Street New York, NY 10036

Clearances

Adequate clearance must be made around the air openings into the vestibule area. In order to ensure proper unit operation, combustion and ventilation air supply must be provided according to the current National Fuel Gas Code.

Vent installations must be consistent with the venting tables (in this instruction) and applicable provisions of local building codes.

This furnace is CSA International certified for installation clearances to combustible material as listed on the unit nameplate and in the tables in figures 8 and 12. Accessibility and service clearances must take precedence over fire protection clearances.

NOTE − For installation on combustible floors, the furnace shall not be installed directly on carpeting, tile, or other combustible material other than wood flooring.

Installed Locations

For installation in a residential garage, the furnace must be installed so that the burner(s) and the ignition source are located no less than 18 inches (457 mm) above the floor. The furnace must be located or protected to avoid physical damage by vehicles. When a furnace is installed in a public garage, hangar, or other building that has a hazardous atmosphere, the furnace must be installed according to recommended good practice requirements and current National Fuel Gas Code.

Temperature Rise

NOTE − Furnace must be adjusted to obtain a temperature rise within the range specified on the unit nameplate. Failure to do so may cause erratic limit operation and may result in premature heat exchanger failure.

This ML180UH furnace must be installed so that its electrical components are protected from water.

Page 4

Installed in Combination with a Cooling Coil

When this furnace is used with cooling units, it shall be installed in parallel with, or on the upstream side of, cooling units to avoid condensation in the heating compartment. See figure 2. With a parallel flow arrangement, a damper (or other means to control the flow of air) must adequately prevent chilled air from entering the furnace. If the damper is manually operated, it must be equipped to prevent operation of either the heating or the cooling unit, unless it is in the full HEAT or COOL setting. See figure 2.

Heating Unit Installed Parallel to Cooling Coil

Dampers

(open during heating operation only)

Gas Unit

Cooling Coil

Dampers

(open during cooling operation only)

Heating Unit Installed Upstream of Cooling Unit

Gas Unit

Cooling Coil

FIGURE 2

When installed, this furnace must be electrically grounded according to local codes. In addition, in the United States, installation must conform with the current National Electric Code, ANSI/NFPA No. 70. The National Electric Code (ANSI/NFPA No. 70) is available from the following address:

National Fire Protection Association 1 Battery March Park Quincy, MA 02269

NOTE − This furnace is designed for a minimum continuous return air temperature of 60°F (16°C) or an intermittent operation down to 55°F (13°C) dry bulb for cases where a night setback thermostat is used. Return air temperature must not exceed 85°F (29°C) dry bulb.

The ML180UH furnace may be installed in alcoves, closets, attics, basements, garages, crawl spaces and utility rooms in the upflow or horizontal position.

This furnace design has not been CSA International certified for installation in mobile homes, recreational vehicles, or outdoors.

Use of Furnace as Construction Heater

Lennox does not recommend the use of ML180UH units as a construction heater during any phase of construction. Very low return air temperatures, harmful vapors and operation of the unit with clogged or misplaced filters will damage the unit.

ML180UH units may be used for heating of buildings or structures under construction, if the following conditions are met:

D The vent system must be permanently installed per

these installation instructions.

D A room thermostat must control the furnace. The use of

fixed jumpers that will provide continuous heating is not allowed.

D The return air duct must be provided and sealed to the

furnace.

D Return air temperature range between 60°F (16°C) and

80°F (27°C) must be maintained.

D Air filters must be installed in the system and must be

maintained during construction.

D Air filters must be replaced upon construction comple-

tion.

D The input rate and temperature rise must be set per the

furnace rating plate.

D One hundred percent (100%) outdoor air must be pro-

vided for combustion air requirements during construction. Temporary ducting may supply outdoor air to the furnace. Do not connect duct directly to the furnace. Size the temporary duct following these instructions in section for Combustion, Dilution and Ventilation Air in a confined space with air from outside.

D The furnace heat exchanger, components, duct system,

air filters and evaporator coils must be thoroughly cleaned following final construction clean−up.

D All furnace operating conditions (including ignition, in-

put rate, temperature rise and venting) must be verified according to these installation instructions.

General

These instructions are intended as a general guide and do not supersede local codes in any way. Consult authorities having jurisdiction before installation.

In addition to the requirements outlined previously, the following general recommendations must be considered when installing a ML180UH furnace:

 Place the furnace as close to the center of the air dis-

tribution system as possible. The furnace should also be located close to the chimney or vent termination point.

Page 5

 Do not install the furnace where drafts might blow direct-

ly into it. This could cause improper combustion and unsafe operation.

 Do not block the furnace combustion air openings with

clothing, boxes, doors, etc. Air is needed for proper combustion and safe unit operation.

 When the furnace is installed in an attic or other insu-

lated space, keep insulation away from the furnace.

NOTE − The Commonwealth of Massachusetts stipulates these additional requirements:

D Gas furnaces shall be installed by a licensed plumb-

er or fitter only.

D The gas cock must be T handle" type. D When a furnace is installed in an attic, the passage-

way to and service area surrounding the equipment shall be floored.

WARNING

Product contains fiberglass wool.

Disturbing the insulation in this product during installation, maintenance, or repair will expose you to fiberglass wool. Breathing this may cause lung cancer. (Fiberglass wool is known to the State of California to cause cancer.)

Fiberglass wool may also cause respiratory, skin, and eye irritation.

To reduce exposure to this substance or for further information, consult material safety data sheets available from address shown below, or contact your supervisor.

Lennox Industries Inc. P.O. Box 799900 Dallas, TX 75379−9900

Combustion, Dilution & Ventilation Air

In the past, there was no problem in bringing in sufficient outdoor air for combustion. Infiltration provided all the air that was needed. In today’s homes, tight construction practices make it necessary to bring in air from outside for combustion. Take into account that exhaust fans, appliance vents, chimneys, and fireplaces force additional air that could be used for combustion out of the house. Unless outside air is brought into the house for combustion, negative pressure (outside pressure is greater than inside pressure) will build to the point that a downdraft can occur in the furnace vent pipe or chimney. As a result, combustion gases enter the living space creating a potentially dangerous situation.

In the absence of local codes concerning air for combustion and ventilation, use the guidelines and procedures in this section to install ML180UH furnaces to ensure efficient and safe operation. You must consider combustion air needs and requirements for exhaust vents and gas piping.

A portion of this information has been reprinted with permission from the National Fuel Gas Code (ANSI-Z223.1). This reprinted material is not the complete and official position of the ANSI on the referenced subject, which is represented only by the standard in its entirety.

CAUTION

Do not install the furnace in a corrosive or contaminated atmosphere. Meet all combustion and ventilation air requirements, as well as all local codes.

CAUTION

Insufficient combustion air can cause headaches, nausea, dizziness or asphyxiation. It will also cause excess water in the heat exchanger resulting in rusting and premature heat exchanger failure. Excessive exposure to contaminated combustion air will result in safety and performance related problems. Avoid exposure to the following substances in the combustion air supply:

Permanent wave solutions Chlorinated waxes and cleaners Chlorine base swimming pool chemicals Water softening chemicals De-icing salts or chemicals Carbon tetrachloride Halogen type refrigerants Cleaning solvents (such as perchloroethylene) Printing inks, paint removers, varnishes, etc. Hydrochloric acid Cements and glues Antistatic fabric softeners for clothes dryers Masonry acid washing materials

All gas-fired appliances require air for the combustion process. If sufficient combustion air is not available, the furnace or other appliances will operate inefficiently and unsafely. Enough air must be provided to meet the needs of all fuel-burning appliances and appliances such as exhaust fans which force air out of the house. When fireplaces, exhaust fans, or clothes dryers are used at the same time as the furnace, much more air is necessary to ensure proper combustion and to prevent a downdraft. Insufficient air causes incomplete combustion which can result in carbon monoxide.

In addition to providing combustion air, fresh outdoor air dilutes contaminants in the indoor air. These contaminants may include bleaches, adhesives, detergents, solvents and other contaminants which can corrode furnace components.

The requirements for providing air for combustion and ventilation depend largely on whether the furnace is installed in an unconfined or a confined space.

Page 6

Unconfined Space

An unconfined space is an area such as a basement or large equipment room with a volume greater than 50 cubic feet (1.42 m3) per 1,000 Btu (.29 kW) per hour of the combined input rating of all appliances installed in that space. This space also includes adjacent rooms which are not separated by a door. Though an area may appear to be unconfined, it might be necessary to bring in outdoor air for combustion if the structure does not provide enough air by infiltration. If the furnace is located in a building of tight construction with weather stripping and caulking around the windows and doors, follow the procedures in the air from outside section.

Confined Space

A confined space is an area with a volume less than 50 cubic feet (1.42 m3) per 1,000 Btu (.29 kW) per hour of the combined input rating of all appliances installed in that space. This definition includes furnace closets or small equipment rooms.

When the furnace is installed so that supply ducts carry air circulated by the furnace to areas outside the space containing the furnace, the return air must be handled by ducts which are sealed to the furnace casing and which terminate outside the space containing the furnace. This is especially important when the furnace is mounted on a platform in a confined space such as a closet or small equipment room. Even a small leak around the base of the unit at the platform or at the return air duct connection can cause a potentially dangerous negative pressure condition. Air for combustion and ventilation can be brought into the confined space either from inside the building or from outside.

EQUIPMENT IN CONFINED

SPACE ALL AIR FROM INSIDE

CHIMNEY

OR GAS

VENT

WATER

FURNACE

HEATER

Air from Inside

If the confined space that houses the furnace adjoins a space categorized as unconfined, air can be brought in by providing two permanent openings between the two spaces. Each opening must have a minimum free area of 1 square inch (645 mm2) per 1,000 Btu (.29 kW) per hour of total input rating of all gas−fired equipment in the confined space. Each opening must be at least 100 square inches (64516 mm2). One opening shall be within 12 inches (305 mm) of the top of the enclosure and one opening within 12 inches (305 mm) of the bottom. See figure 3.

Air from Outside

If air from outside is brought in for combustion and ventilation, the confined space must have two permanent openings. One opening shall be within 12 inches (305 mm) of the top of the enclosure and one opening within 12 inches (305 mm) of the bottom. These openings must communicate directly or by ducts with the outdoors or spaces (crawl or attic) that freely communicate with the outdoors or indirectly through vertical ducts. Each opening shall have a minimum free area of 1 square inch (645 mm2) per 4,000 Btu (1.17 kW) per hour of total input rating of all equipment in the enclosure. See figures 4 and 5. When communicating with the outdoors through horizontal ducts, each opening shall have a minimum free area of 1 square inch (645 mm2) per 2,000 Btu (.56 kW) per total input rating of all equipment in the enclosure. See figure 6.

When ducts are used, they shall be of the same cross−sectional area as the free area of the openings to which they connect. The minimum dimension of rectangular air ducts shall be no less than 3 inches (75 mm). In calculating free area, the blocking effect of louvers, grilles, or screens must be considered. If the design and free area of protective covering is not known for calculating the size opening required, it may be assumed that wood louvers will have 20 to 25 percent free area and metal louvers and grilles will have 60 to 75 percent free area. Louvers and grilles must be fixed in the open position or interlocked with the equipment so that they are opened automatically during equipment operation.

OPENINGS

(To Adjacent

Room)

NOTE − Each opening shall have a free area of at least one square inch (645 mm2) per 1,000 Btu (.29 kW) per hour of the total input rating of all equipment in the enclosure, but not less than 100 square inches (64516 mm2).

FIGURE 3

Page 7

CHIMNEY OR

GAS VENT

FURNACE

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

VENTILATION LOUVERS

(Each end of attic)

EQUIPMENT IN CONFINED SPACE

ALL AIR FROM OUTSIDE

OUTLET

AIR

WATER

HEATER

CHIMNEY

OR GAS

VENT

FURNACE

VENTILATION

LOUVERS

(For unheated crawl space)

NOTE−The inlet and outlet air openings shall each have a free area of at least one square inch (645

) per 4,000 Btu (1.17 kW) per hour of the total input rating of all equipment in the enclosure.

INLET

AIR

FIGURE 4

EQUIPMENT IN CONFINED SPACE

ALL AIR FROM OUTSIDE

(All Air Through Ventilated Attic)

VENTILATION LOUVERS

(Each end of attic)

OUTLET

AIR

above bottom)

INLET AIR

(Ends 12 in.

WATER

HEATER

FURNACE

CHIMNEY

OR GAS

VENT

WATER

HEATER

EQUIPMENT IN

CONFINED SPACE

ALL AIR FROM

OUTSIDE

OUTLET AIR

INLET AIR

NOTE−The inlet and outlet air openings shall each have a free area of at least one square inch (645 mm2) per 4,000 Btu (1.17 kW) per hour of the total input rating of all equipment in the enclosure.

FIGURE 5

NOTE − Each air duct opening shall have a free area of at least one square inch (645 mm2) per 2,000 Btu (.59 kW) per hour of the total input rating of all equipment in the enclosure. If the equipment room is located against an outside wall and the air openings communicate directly with the outdoors, each opening shall have a free area of at least one square inch (645 mm2) per 4,000 Btu (1.17 kW) per hour of the total input rating of all other equipment in the enclosure.

FIGURE 6

Page 8

Setting Equipment

WARNING

Do not install the furnace on its front or its back. Do not connect the return air ducts to the back of the furnace. Doing so will adversely affect the operation of the safety control devices, which could result in personal injury or death.

The ML180UH gas furnace can be installed as shipped in either the upflow position or the horizontal position. Select a location that allows for the required clearances

that are listed on the unit nameplate. Also consider gas supply connections, electrical supply, vent connection, and installation and service clearances [24 inches (610 mm) at unit front]. The unit must be level.

NOTE − Units with 1/2 hp blower motors are equipped with three flexible legs and one rigid leg. See figure 7. The rigid leg is equipped with a shipping bolt and a flat white plastic washer (rather than the rubber mounting grommet used with a flexible mounting leg). The bolt and washer must

be removed before the furnace is placed into operation. After the bolt and washer have been removed, the rig-

id leg will not touch the blower housing.

ML180UH09048B with 1/2 HP

BLOWER MOTOR

RIGID LEG

remove shipping bolt and washer

FIGURE 7

Upflow Applications

Allow for clearances to combustible materials as indicated on the unit nameplate. Minimum clearances for closet or alcove installations are shown in figure 8.

Upflow Application Installation Clearances

Top

Left Side

Bottom

Type of Vent

Connector

Top 1 in. (25 mm) 1 in. (25 mm)

*Front 2−1/4 in. (57 mm)** 2−1/4 in. (57 mm)

Back 0 0

Sides 0† 0

Vent 6 in. (152 mm) 1 in. (25 mm)

Floor 0‡ 0‡

*Front clearance in alcove installation must be 24 in. (610 mm). Maintain a minimum of 24 in. (610 mm) for front service access. ** 4−1/2 in. if single wall vent pipe is used. ‡For installation on a combustible floor, do not install the furnace directly on carpeting, tile or other combustible materials other than wood flooring. †Left side requires 3 inches if a single wall vent is used on 14−1/2 in. cabinets, or 2inches if a single wall vent pipe is used on 17−1/2 in. cabinets.

Type C Type B1

Right Side

FIGURE 8

Page 9

Return Air −− Upflow Applications

)

Return air can be brought in through the bottom or either side of the furnace installed in an upflow application. If the furnace is installed on a platform with bottom return, make an airtight seal between the bottom of the furnace and the platform to ensure that the furnace operates properly and safely. The furnace is equipped with a removable bottom panel to facilitate installation.

Markings are provided on both sides of the furnace cabinet for installations that require side return air. Cut the furnace cabinet at the maximum dimensions shown on page 2.

NOTE − 60C and 60D units that require air volumes over 1800

cfm (850 L/s) must have one of the following:

1 − Single side return air with transition to accommodate 20

x 25 x 1 in. (508 x 635 x 25 mm) cleanable air filter. (Required to maintain proper air velocity.) See figure 9.

2 − Single side return air with optional return airbase. See fig-

ure 10.

3 − Bottom return air.

4 − Return air from both sides.

5 − Bottom and one side return air.

Refer to Engineering Handbook for additional information.

Single Side Return Air

(with transition and filter)

20” X 25” X 1”

(508mm X 635mm X 25mm)

Cleanable Filter

Return Air

Plenum

AIR FLOW

Transition

FIGURE 9

Optional Return Air Base

(Upflow Applications Only −− For use with A, B, C and D cabinets)

FURNACE

FRONT

IF BASE

IS USED

WITHOUT

INDOOR AIR

QUALITY

AIR FLOW

14−1/2 (368) A Width (65W75) 17−1/2 (446) B Width (50W98) 21 (533) C Width (50W99) 24−1/2 (622) D Width (51W00)

NOTE− Optional Side Return Air Filter Kits are not for use with Optional Return Air Base.

Both the unit return air opening and the base return air opening must be covered by a single plenum or IAQ cabinet.

CABINET

(PCO, Filter

Cabinet, etc.)

OPTIONAL RETURN AIR BASE

IAQ CABINET,

A SINGLE

RETURN AIR

PLENUM

MUST

COVER BOTH

UNIT AND

RETURN

AIR BASE

OPENINGS

3−1/4

(83)

7−1/4

(184)

Minimum unit side return air opening dimensions for units requiring 1800 cfm or more of air (W x H): 23 x 11 in. (584 x 279 mm). The opening can be cut as needed to accommodate plenum or IAQ cabinet while maintaining dimensions shown. Side return air openings must be cut in the field. There are cutting guides stenciled on the cabinet for the side return air opening. The size of the opening must not extend beyond the markings on the furnace cabinet.

To minimize pressure drop, the largest opening height possible (up to 14 inches 356 mm) is preferred.

23 (584)

Overall

(Maximum)

Unit side return air

Opening

5−5/8 (143)

SIDE RETURN

AIR OPENINGS

(Either Side)

26−7/8

(683)

SIDE VIEW

(584)

Minimum

11 (279)

Maximum

14 (356)

22−7/16

(570)

Overall

(Maximum

3/4

(19)

FIGURE 10

Page 10

Removing the Bottom Panel

Remove the two screws that secure the bottom cap to the furnace. Pivot the bottom cap down to release the bottom panel. Once the bottom panel has been removed, reinstall the bottom cap. See figure 11.

Removing the Bottom Panel

Horizontal Applications

The ML180UH furnace can be installed in horizontal applications. Order horizontal suspension kit (51W10) from Lennox, or use equivalent suspension method.

Allow for clearances to combustible materials as indicated on the unit nameplate. Minimum clearances for closet or alcove installations are shown in figure 12.

This furnace may be installed in either an attic or a crawlspace. Either suspend the furnace from roof rafters or floor joists, as shown in figure 13, or install the furnace on a platform, as shown in figure 14.

Typical Horizontal Application

Unit Suspended in Attic or Crawlspace

Metal

Internal

Strap

Brace

Screw

Bottom Cap

Bottom Panel

FIGURE 11

Horizontal Application

Installation Clearances

Left End

Vent Connector

Type

Top 0 0

*Front 2−1/4 in. (57 mm)** 2−1/4 in. (57 mm)

Back 0 0

Ends 2 in. (51 mm) 2 in. (51 mm)

Vent 6 in. (152 mm) 1 in. (25 mm)

Floor 0‡ 0‡

Top

Right

AIR FLOW

End

Bottom

Type C Type B1

Bracket

3/16

Air Flow

FIGURE 13

NOTE − Heavy−gauge perforated sheet metal straps may be used to suspend the unit from roof rafters or ceiling joists. When straps are used to suspend the unit in this way, support must be provided for both the ends. The straps must not interfere with the plenum or exhaust piping installation. Cooling coils and supply and return air

plenums must be supported separately. NOTE − When the furnace is installed on a platform in a

crawlspace, it must be elevated enough to avoid water damage and to allow the evaporator coil to drain.

Return Air −− Horizontal Applications

Return air must be brought in through the end of a furnace installed in a horizontal application. The furnace is equipped with a removable bottom panel to facilitate installation. See figure 11.

FIGURE 12

Page 11

Horizontal Application

Unit Installed on Platform

Line contact is permissible but not preferred

See the unit nameplate for

clearances.

GAS

ENTRY

SERVICE PLATFORM

VENT

PIPE

FIGURE 14

WARNING

Improper installation of the furnace can result in personal injury or death. Combustion and flue products must never be allowed to enter the return air system or the living space. Use screws and joint tape to seal the return air system to the furnace. In platform installations with bottom return air, the furnace should be sealed airtight to the return air plenum. A door must never be used as a portion of the return air duct system. The base must provide a stable support and an airtight seal to the furnace. Allow absolutely no sagging, cracks, gaps, etc. The return and supply air duct systems must never be connected to or from other heating devices such as a fireplace or stove, etc. Fire, explosion, carbon monoxide poisoning, personal injury and/or property damage could result.

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 injury or death.

Filters

This unit is not equipped with a filter or rack. A field−provided high−velocity filter is required for the unit to operate properly. Table 1 lists recommended filter sizes. A filter must be in place any time the unit is operating.

TABLE 1

Furnace

Cabinet Width

A − 14−1/2" 16 X 25 X 1 (1) 14 X 25 X 1 (1) B − 17−1/2" 16 X 25 X 1 (1) 16 X 25 X 1 (1)

C − 21" 16 X 25 X 1 (1) 20 X 25 X 1 (1)

D − 24−1/2" 16 X 25 X 1 (2) 24 X 25 X 1 (1)

Side Return Bottom Return

Filter Size

Duct System

Use industry-approved standards (such as those published by Air Conditioning Contractors of America or American Society of Heating, Refrigerating and Air Conditioning Engineers) to size and install the supply and return air duct system. This will result in a quiet and low-static system that has uniform air distribution.

NOTE − Do not operate the furnace in the heating mode with an external static pressure that exceeds 0.5 inches w.c. Higher external static pressures may cause erratic limit operation.

Supply Air Plenum

If the furnace is installed without a cooling coil, a removable access panel must be installed in the supply air duct. The access panel should be large enough to permit inspection (either by smoke or reflected light) of the heat exchanger for leaks after the furnace is installed. The furnace access panel must always be in place when the furnace is operating and it must not allow leaks into the supply air duct system.

Return Air Plenum

NOTE − Return air must not be drawn from a roomwhere this furnace, or any other gas−fueled appliance (i.e., water heater), or carbon monoxide producing device (i.e., wood fireplace) is installed.

When return air is drawn from a room, a negative pressure is created in the room. If a gas appliance is operating in a room with negative pressure, the flue products can be pulled back down the vent pipe and into the room. This reverse flow of the flue gas may result in incomplete combustion and the formation of carbon monoxide gas. This toxic gas might then be distributed throughout the house by the furnace duct system.

In upflow applications, the return air can be brought in through the bottom or either side of the furnace. If a furnace with bottom return air is installed on a platform, make an airtight seal between the bottom of the furnace and the platform to ensure that the unit operates properly and safely. Use fiberglass sealing strips, caulking, or equivalent sealing method between the plenum and the furnace cabinet to ensure a tight seal. If a filter is installed, size the return air duct to fit the filter frame.

Page 12

Venting

A 4−inch diameter flue transition is factory-installed on the combustion air inducer outlet of all models. Figure 16

shows the combustion air inducer as shipped from the factory.

Mounting Screws Location

Flue Transition

Mounting Screws

1 − Remove the four mounting screws (figure 15) which

secure the combustion air inducer / pressure switch assembly to the orifice plate. Lift the assembly and rotate it 90 degrees clockwise or counterclockwise to either the 3 o’clock position or to 9 o’clock position. Re− secure with four screws. Gasket should be left in place.

2 − Use tin snips to cut preferred opening on the cabinet

for repositioning the flue outlet. Use the cut−out piece as a cover plate to patch unused opening on cabinet.

UPFLOW POSITION

Left Side Vent Discharge

Pressure

Switch

Vent Pipe

Collector Box

Make−Up

Box

FIGURE 15

Upflow Position

UPFLOW POSITION

Pressure

Switch

Make−Up

Box

Top Vent Discharge

Flue

Transition

AIR

Vent Pipe

Collector Box

FLOW

FIGURE 16

IMPORTANT

The unit will not vent properly with the flue transition pointed down in the 6 o’clock position. The combustion air inducer may be rotated clockwise or counterclockwise by 90° to allow for top or side vent discharge in all applications. When the unit is installed, the flue transition must be in the 9 o’clock, 12 o’clock or 3 o’clock position.

If necessary, reposition the combustion air inducer, pressure switch and/or make−up box as needed per the following steps. See figures 16 through 22.

Flue

Transition

FLOW

AIR

 Gas supply piping must be brought into the unit from the right

side in order to accommodate the flue pipe.

 Cut combustion air inducer tubing from 9" to 8" to avoid

interference with inducer motor

 Remove make−up box assembly (2 screws) and cut wire tie to

free make−up box wires. Re−install make−up box on other side of cabinet.

 Re−secure make−up box wires: Either pull excess wires

through the blower compartment and secure using supplied wire tie, or coil excess wire and secure to the gas manifold.

FIGURE 17

UPFLOW POSITION

Right Side Vent Discharge

Collector Box

Pressure

Switch

Make−Up

Box

 Cut combustion air inducer tubing from 9" to 5" to avoid

interference with inducer motor

Cover Plate

AIR

Flue Transition

Vent Pipe

FLOW

FIGURE 18

Page 13

Vent Pipe

Pressure

Switch

HORIZONTAL LEFT POSITION

Top Vent Discharge

Vent Pipe

Flue

Transition

HORIZONTAL RIGHT POSITION

Top Vent Discharge

Pressure Switch

Cover Plate

Flue

Transition

Cover Plate

Make−Up Box

 Disconnect pressure switch hose from barbed fitting on the

pressure switch assembly. Remove pressure switch assembly (1 screw) and cut wire tie to free pressure switch wires. Re− install pressure switch on the other side of orifice plate and re− connect pressure switch hose.

 Re−secure pressure switch wires: Either pull excess wires

through the blower compartment and secure using supplied wire tie, or coil excess wire and secure to the gas manifold.

AIR

FLOW

Collector Box

FIGURE 19

HORIZONTAL LEFT POSITION

Side Vent Discharge

Pressure Switch

AIR

FLOW

 Gas supply piping must be brought into the unit from the bot-

tom in order to accommodate the flue pipe.

 Cut combustion air inducer tubing from 9" to 8" to avoid

interference with inducer motor

 Remove make−up box assembly (2 screws) and cut wire tie to

free make−up box wires. Re−install make−up box on other side of cabinet.

 Re−secure make−up box wires: Either pull excess wires through

the blower compartment and secure using supplied wire tie, or coil excess wire and secure to the gas manifold.

Collector Box

Make−Up Box

FIGURE 21

AIR

FLOW

Vent Pipe

Make−Up Box

 Cut combustion air inducer tubing from 9" to 7" to avoid

interference with inducer motor

 Disconnect pressure switch hose from barbed fitting on the

 Re−secure pressure switch wires: Either pull excess wires

through the blower compartment and secure using supplied wire tie, or coil excess wire and secure to the gas manifold.

Collector Box

FIGURE 20

Make−Up Box

AIR

FLOW

HORIZONTAL RIGHT POSITION

Side Vent Discharge

Pressure Switch

Flue Transition

Collector Box

FIGURE 22

Page 14

The ML180UH series units are classified as fan−assisted Category I furnaces when vertically vented according to the latest edition of National Fuel Gas Code (NFPA 54 / ANSI Z223.1) in the USA. A fan−assisted Category I furnace is an appliance equipped with an integral mechanical means to either draw or force combustion products through the combustion chamber and/or heat exchanger. The ML180UH is not approved for use with horizontal venting.

NO T E − Use these instructions as a guide. They do not supersede local codes. This furnace must be vented according to all local codes these installation instructions, and the provided venting tables in these instructions

The venting tables in this manual were extracted from the National Fuel Gas Code (NFPA 54 / ANSI Z223.1) and are provided as a guide for proper vent installation. Proper application, termination, construction and location of vents must conform to local codes having jurisdiction. In the absence of local codes, the NFGC serves as the defining document.

Refer to the tables and the venting information contained in these instructions to properly size and install the venting system.

Use self−drilling sheet metal screws or a mechanical fastener to firmly secure the vent pipe to the round collar of the flue transition. If self−drilling screws are used to attach the vent pipe, it is recommended that three be used. Drive one self−drilling screw through the front and one through each side of the vent pipe and collar. See figure 23.

Install the first vent connector elbow at a minimum of six inches (152 mm) from the furnace vent outlet. See figure

23.

Venting Using a Masonry Chimney

The following additional requirements apply when a lined masonry chimney is used to vent this furnace.

Masonry chimneys used to vent Category I central furnaces must be either tile-lined or lined with a listed metal lining system or dedicated gas vent. Unlined masonry chimneys are prohibited. See figures 24 and 25 for common venting.

A chimney with one or more sides exposed to the outside of the structure is considered to be an exterior chimney.

An exterior masonry chimney that is not tile−lined must be lined with B1 vent or a listed insulated flexible metal vent. An exterior tile−lined chimney that is sealed and capped may be lined with a listed uninsulated flexible metal vent.

If the existing chimney will not accommodate a listed metal liner, either the chimney must be rebuilt to accommodate one of these liners or an alternate approved venting method must be found.

Insulation for the flexible vent pipe must be an encapsulated fiberglass sleeve recommended by the flexible vent pipe manufacturer. See figure 24.

IMPORTANT

Once the venting system is installed, attach the Disconnected Vent" warning sticker to a visible area of the plenum near the vent pipe. See figure 23. The warning sticker is provided in the bag assembly. Order kit 66W04 for additional stickers.

WARNING

Asphyxiation hazard. The exhaust vent for this furnace must be securely connected to the furnace flue transition at all times.

VENT PIPE

(min. 6" length)

FLUE TRANSITION

COLLAR

VENT CONNECTION UPFLOW AND HORIZONTAL POSITION

“DISCONNECTED VENT”

WARNING

STICKER

“DISCONNECTED VENT”

WARNING

STICKER

VENT PIPE

(min. 6" length)

FIGURE 23

Page 15

FLUE

TRANSITION

COLLAR

Common Venting Using Metal−Lined Masonry Chimney

SEALED

MAX. LENGTH

−− SEE NOTE 1

5 ft. (1.5 m)

minimum

VENT CONNECTOR

4 in. (102 mm)

minimum

OTHER

APPLIANCE

NOTE 1 − Refer to the provided venting tables for installations. Refer to the capacity requirements shown in the provided venting tables.

BELOW.

MIN. LENGTH −− AS

SHORT AS PRACTICAL

FURNACE

EXTERIOR

CHIMNEY WITH

METAL

LINER

PERMANENTLY

SEALED FIREPLACE

OPENING

FIGURE 24 DO NOT insulate the space between the liner and the chimney wall with puffed mica or any other loose granular insulating material.

IMPORTANT

SINGLE appliance venting of a fan-assisted furnace into a tile-lined masonry chimney (interior or outside wall) is PROHIBITED. The chimney must first be lined with either type B1 vent or an insulated single wall flexible vent lining system which has been sized according to the provided venting tables and the vent pipe manufacturer’s instructions.

A fan−assisted furnace may be commonly vented into an existing lined masonry chimney if the following conditions are met:

 The chimney is currently serving at least one drafthood−

equipped appliance;

 The vent connectors and chimney are sized according

to the provided venting tables. If type B1 double-wall vent is used inside a chimney, no other appliance can be vented into the chimney. The outer wall of type B1 vent pipe must not be exposed to flue products. A type B1 vent or masonry chimney liner shall terminate above the roof surface with a listed cap or a listed roof assembly according to the terms of their respective listings and the vent manufacturer’s instructions.

When inspection reveals that an existing chimney is not safe for the intended purpose, it shall be rebuilt to conform to nationally recognized standards, lined or relined with suitable materials, or replaced with a gas vent or chimney suitable for venting ML180UH series units. The chimney passageway must be checked periodically to ensure that it is clear and free of obstructions.

Do not install a manual damper, barometric draft regulator, or flue restrictor between the furnace and the chimney.

Never connect a Category I appliance to a chimney that is servicing a solid−fuel appliance. If a fireplace chimney flue is used to vent this appliance, the fireplace opening must be permanently sealed.

A type B or listed chimney lining system that passes through an unused masonry chimney flue is not considered to be exposed to the outdoors.

General Venting Requirements

Vent all ML180UH furnaces according to these instructions:

1 − Vent diameter recommendations and maximum allow-

able piping runs are found in the provided venting tables.

2 − In no case should the vent or vent connector diameter

be less than the diameter specified in the provided venting tables.

3 − The minimum vent capacity determined by the sizing

tables must be less than the low fire input rating and the maximum vent capacity must be greater than the high fire input rating.

4 − Single appliance vents − If the vertical vent or tile-lined

chimney has a larger diameter or flow area than the vent connector, use the vertical vent diameter to determine the minimum vent capacity and the vent

connector diameter to determine the maximum vent capacity. The flow area of the vertical vent, however,

shall not exceed 7 times the flow area of the listed appliance categorized vent area, drafthood outlet area or flue collar area unless designed according to approved engineering methods.

5 − Multiple appliance vents − The flow area of the largest

section of vertical vent or chimney shall not exceed 7 times the smallest listed appliance categorized vent area, drafthood outlet area or flue collar area unless designed according to approved engineering methods.

Page 16

Common Venting Using Tile−Lined Interior Masonry Chimney and Combined Vent Connector

MINIMUM LENGTH = AS SHORT AS PRACTICAL. FOR MAXIMUM LENGTH SEE NOTE TO LEFT

NOTE− Refer to provided venting tables for installations.

OTHER

APPLIANCE

FIGURE 25

6 − The entire length of single wall metal vent connector

shall be readily accessible for inspection, cleaning, and replacement.

7 − Single appliance venting configurations with zero lat-

eral lengths (tables 3 and 4) are assumed to have no elbows in the vent system. For all other vent configurations, the vent system is assumed to have two 90° elbows. For each additional 90° elbow or equivalent (for example two 45° elbows equal one 90° elbow) beyond two, the maximum capacity listed in the venting table should be reduced by 10% (0.90 x maximum listed capacity).

8 − The common venting tables (5, 6, 7, and 8) were gen-

erated using a maximum horizontal vent connector length of 1−1/2 feet (.46 m) for each inch (25 mm) of connector diameter as follows:

TABLE 2

Connector Diameter

inches (mm)

3 (76) 4−1/2 (1.37)

4 (102) 6 (1.83)

5 (127) 7−1/2 (2.29)

6 (152) 9 (2.74)

7 (178) 10−1/2 (3.20)

Maximum Horizontal

Connector Length feet (m)

9 − If the common vertical vent is offset, the maximum

common vent capacity listed in the common venting tables should be reduced by 20%, the equivalent of two 90° elbows (0.80 x maximum common vent capacity). The horizontal length of the offset shall not exceed

INTERIOR TILE−LINED MASONRY CHIMNEY

NOTE − the chimney must be properly sized per provided venting tables or lined with listed metal lining system.

VENT

CONNECTOR

FURNACE

PERMANENTLY SEALED FIREPLACE OPENING

1-1/2 feet (.46 m) for each inch (25 mm) of common vent diameter.

10 − The vent pipe should be as short as possible with the

least number of elbows and angles required to complete the job. Route the vent connector to the vent using the shortest possible route.

11 − A vent connector shall be supported without any dips

or sags and shall slope a minimum of 1/4 inch (6.4 mm) per linear foot (305 mm) of connector, back toward the appliance.

12 − Vent connectors shall be firmly attached to the furnace

flue collar by self−drilling screws or other approved means, except vent connectors of listed type B vent material which shall be assembled according to the manufacturer’s instructions. Joints between sections of single wall connector piping shall be fastened by screws or other approved means.

13 − When the vent connector used for Category I ap-

pliances must be located in or pass through a crawlspace, attic or other areas which may be cold, that portion of the vent connector shall be constructed of listed double-wall type B vent material or material having equivalent insulation qualities.

14 − All venting pipe passing through floors, walls, and ceil-

ings must be installed with the listed clearance to combustible materials and be fire stopped according to local codes. In absence of local codes, refer to NFGC (Z223.1).

15 − No portion of the venting system can extend into, or pass

through any circulation air duct or plenum.

Page 17

16 − Vent connectors serving Category I appliances shall

not be connected to any portion of mechanical draft

systems operating under positive pressure such as

Category III or IV venting systems.

17 − If vent connectors are combined prior to entering the

common vent, the maximum common vent capacity

listed in the common venting tables must be reduced by

10%, the equivalent of one 90° elbow (0.90 x maximum

common vent capacity).

18 − The common vent diameter must always be at least as

large as the largest vent connector diameter.

19 − In no case, shall the vent connector be sized more than

two consecutive table size diameters over the size of the draft hood outlet or flue collar outlet.

20 − Do not install a manual damper, barometric draft regu-

lator or flue restrictor between the furnace and the chimney.

21 − When connecting this appliance to an existing dedi-

cated or common venting system, you must inspect the venting system’s general condition and look for signs of corrosion. The existing vent pipe size must conform to these instructions and the provided venting tables. If the existing venting system does not meet these requirements, it must be resized.

TABLE 3

Capacity of Type B Double−Wall Vents with Type B Double−Wall Connectors

Serving a Single Category I Appliance

Vent and Connector Diameter − D (inches)

Height

(feet)

NOTE − Single appliance venting configurations with zero lateral lengths are assumed to have no elbows in the vent system. For all other vent configurations, the vent system is assumed to have two 90° elbows. For each additional 90° elbow or equivalent (for example two 45° elbows equal one 90° elbow) beyond two, the maximum capacity listed in the venting table should be reduced by 10 percent (0.90 x maximum listed capacity).

Lateral

(feet)

0 0 78 0 152 0 251 0 375

2 13 51 18 97 27 157 32 232

4 21 49 30 94 39 153 50 227

6 25 46 36 91 47 149 59 223

0 0 84 0 165 0 276 0 415

2 12 57 16 109 25 178 28 263

5 23 53 32 103 42 171 53 255

8 28 49 39 98 51 164 64 247

0 0 88 0 175 0 295 0 447

2 12 61 17 118 23 194 26 289

5 23 57 32 113 41 187 52 280

10 30 51 41 104 54 176 67 267

0 0 94 0 191 0 327 0 502

2 11 69 15 136 20 226 22 339

5 22 65 30 130 39 219 49 330

10 29 59 40 121 51 206 64 315

15 35 53 48 112 61 195 76 301

0 0 97 0 202 0 349 0 540

2 10 75 14 149 18 250 20 377

5 21 71 29 143 38 242 47 367

10 28 64 38 133 50 229 62 351

15 34 58 46 124 59 217 73 337

20 48 52 55 116 69 206 84 322

0 0 100 0 213 0 374 0 587

2 9 81 13 166 14 283 18 432

5 21 77 28 160 36 275 45 421

10 27 70 37 150 48 262 59 405

15 33 64 44 141 57 249 70 389

20 56 58 53 132 66 237 80 374

30 NA NA 73 113 88 214 104 346

3 Inch 4 Inch 5 Inch 6 Inch

Appliance Input Rating in Thousands of Btu Per Hour

MIN MAX MIN MAX MIN MAX MIN MAX

Page 18

TABLE 4

Capacity of Type B Double−Wall Vents with Single−Wall Metal Connectors

Serving a Single Category I Appliance

Vent and Connector Diameter − D (inches)

Height

(feet)

Lateral

(feet)

0 38 77 59 151 85 249 126 373

2 39 51 60 96 85 156 123 231

4 NA NA 74 92 102 152 146 225

6 NA NA 83 89 114 147 163 220

0 37 83 58 164 83 273 123 412

2 39 56 59 108 83 176 121 261

5 NA NA 77 102 107 168 151 252

8 NA NA 90 95 122 161 175 243

0 37 87 57 174 82 293 120 444

2 39 61 59 117 82 193 11 9 287

5 52 56 76 111 105 185 148 277

10 NA NA 97 100 132 171 188 261

0 36 93 56 190 80 325 11 6 499

2 38 69 57 136 80 225 11 5 337

5 51 63 75 128 102 216 144 326

10 NA NA 95 11 6 128 201 182 308

15 NA NA NA NA 158 186 220 290

0 35 96 54 200 78 346 11 4 537

2 37 74 56 148 78 248 11 3 375

5 50 68 73 140 100 239 141 363

10 NA NA 93 129 125 223 177 344

15 NA NA NA NA 155 208 216 325

20 NA NA NA NA 186 192 254 306

0 34 99 53 211 76 372 11 0 584

2 37 80 55 164 76 281 109 429

5 49 74 72 157 98 271 136 417

10 NA NA 91 144 122 255 171 397

15 NA NA 115 131 151 239 208 377

20 NA NA NA NA 181 223 246 357

30 NA NA NA NA NA NA NA NA

3 Inch 4 Inch 5 Inch 6 Inch

Appliance Input Rating in Thousands of Btu Per Hour

MIN MAX MIN MAX MIN MAX MIN MAX

Page 19

Vent

Height

(feet)

TABLE 5

Vent Connector Capacity

Type B Double−Wall Vents with Type B Double−Wall Connectors

Serving Two or More Category I Appliances

Connector

Rise

(feet)

1 22 37 35 66 46 106 58 164

2 23 41 37 75 48 121 60 183

3 24 44 38 81 49 132 62 199

1 22 40 35 72 49 114 64 176

2 23 44 36 80 51 128 66 195

3 24 47 37 87 53 139 67 210

1 22 43 34 78 49 123 65 189

2 23 47 36 86 51 136 67 206

3 24 50 37 92 52 146 69 220

1 21 50 33 89 47 142 64 220

2 22 53 35 96 49 153 66 235

3 24 55 36 102 51 163 68 248

1 21 54 33 99 46 157 62 246

2 22 57 34 105 48 167 64 259

3 23 60 35 110 50 176 66 271

1 20 62 31 113 45 181 60 288

2 21 64 33 118 47 190 62 299

3 22 66 34 123 48 198 64 309

3 Inch 4 Inch 5 Inch 6 Inch

MIN MAX MIN MAX MIN MAX MIN MAX

Vent and Connector Diameter − D (inches)

Appliance Input Rating in Thousands of Btu Per Hour

TABLE 6

Common Vent Capacity

Type B Double−Wall Vents with Type B Double−Wall Connectors

Serving Two or More Category I Appliances

Vent

Height

(feet)

6 92 81 140 116 204 161 309 248

8 101 90 155 129 224 178 339 275

10 11 0 97 169 141 243 194 367 299

15 125 112 195 164 283 228 427 352

20 136 123 215 183 314 255 475 394

30 152 138 244 210 361 297 547 459

FAN + FAN FAN + NAT FAN + FAN FAN + NAT FAN + FAN FAN + NAT FAN + FAN FAN + NAT

4 Inch 5 Inch 6 Inch 7 Inch

Appliance Input Rating in Thousands of Btu Per Hour

Common Vent Diameter − D (inches)

Page 20

TABLE 7

Vent Connector Capacity

Type B Double−Wall Vents with Single−Wall Metal Connectors

Serving Two or More Category I Appliances

Vent and Connector Diameter − D (inches)

Height

(feet)

Lateral

(feet)

1 NA NA NA NA NA NA NA NA

2 NA NA NA NA NA NA 168 182

3 NA NA NA NA 121 131 175 198

1 NA NA NA NA NA NA NA NA

2 NA NA NA NA 125 126 184 193

3 NA NA NA NA 130 138 191 208

1 NA NA NA NA 11 9 121 182 186

2 NA NA 84 85 124 134 189 203

3 NA NA 89 91 129 144 197 217

1 NA NA 79 87 116 138 177 214

2 NA NA 83 94 121 150 185 230

3 NA NA 87 100 127 160 193 243

1 49 56 78 97 115 152 175 238

2 52 59 82 103 120 163 182 252

3 55 62 87 107 125 172 190 264

1 47 60 77 110 112 175 169 278

2 51 62 81 115 117 185 177 290

3 54 64 85 119 122 193 185 300

3 Inch 4 Inch 5 Inch 6 Inch

Appliance Input Rating in Thousands of Btu Per Hour

MIN MAX MIN MAX MIN MAX MIN MAX

TABLE 8

Common Vent Capacity

Type B Double−Wall Vents with Single−Wall Metal Connectors

Serving Two or More Category I Appliances

Vent

Height

(feet)

6 NA 78 NA 11 3 200 158 304 244

8 NA 87 NA 126 218 173 331 269

10 NA 94 163 137 237 189 357 292

15 121 108 189 159 275 221 416 343

20 131 118 208 177 305 247 463 383

30 145 132 236 202 350 286 533 446

FAN + FAN FAN + NAT FAN + FAN FAN + NAT FAN + FAN FAN + NAT FAN + FAN FAN + NAT

4 Inch 5 Inch 6 Inch 7 Inch

Appliance Input Rating in Thousands of Btu Per Hour

Common Vent Diameter − D (inches)

Page 21

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 appliances, the venting system is likely to be too large to properly vent the remaining attached appliances.

Conduct the following test while each appliance is operating and the other appliances (which are not operating) remain 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 requirements section.

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 monoxide poisoning or death. The following steps shall be followed for each appliance 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 dryers 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 operate at maximum speed. Do not operate a summer exhaust 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 burner have 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 dampers, and any other gas−burning appliances to their previous mode of operation.

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

ing tests, the common venting system must be modified 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 standards of the National Fuel Gas Code ANSI Z223.1.

Page 22

Gas Piping

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.

4 − The piping should be sloped 1/4 inch (6.4 mm) per 15

feet (4.57 m) upward toward the meter from the furnace. The piping must be supported at proper intervals [every 8 to 10 feet (2.44 to 3.01 m)] with suitable hangers or straps. Install a drip leg in vertical pipe runs to the unit.

CAUTION

If a flexible gas connector is required or allowed by the authority that has jurisdiction, black iron pipe shall be installed at the gas valve and extend outside the furnace cabinet. The flexible connector can then be added between the black iron pipe and the gas supply line.

Gas Supply

5 − A 1/8" N.P.T. plugged tap or pressure post is located

on the gas valve to facilitate test gauge connection. See figure 35.

6 − In some localities, codes may require the installation of

a manual main shut-off valve and union (furnished by the installer) external to the unit. The union must be of the ground joint type.

1 − This unit is shipped standard for left or right side instal-

lation of gas piping (or top entry in horizontal applications). Connect the gas supply to the piping assembly.

2 − When connecting the gas supply piping, consider fac-

tors such as length of run, number of fittings, and furnace rating to avoid excessive pressure drop. Table 9

Compounds used on threaded joints of gas piping must be resistant to the actions of liquified petroleum gases.

IMPORTANT

lists recommended pipe sizes for typical applications.

3 − The gas piping must not run in or through air ducts,

clothes chutes, gas vents or chimneys, dumb waiters, or elevator shafts.

NOTE − If emergency shutoff is necessary, shut off the main manual gas valve and disconnect main power to the furnace. The installer should properly label these devices.

TABLE 9

Gas Pipe Capacity − ft3/hr (m3/hr)

Nominal

Iron Pipe

Size

inches

(mm)

1/2

(12.7)

3/4

(19.05)

(25.4)

1−1/4

(31.75)

1−1/2

(38.1)

(50.8)

2−1/2

(63.5)

(76.2)

Internal

Diameter

inches

(mm)

.622

(17.799)

.824

(20.930)

1.049

(26.645)

1.380

(35.052)

1.610

(40.894)

2.067

(52.502)

2.469

(67.713)

3.068

(77.927)

(3.048)20(6.096)30(9.144)40(12.192)50(15.240)60(18.288)70(21.336)80(24.384)90(27.432)

172

(4.87)

360

(10.19)

678

(19.19)

1350

(38.22)

2090

(59.18)

4020

(113.83)

6400

(181.22)

11300

(319.98)

118

(3.34)

247

(7.00)

466

(13.19)

957

(27.09)

1430

(40.49)

2760

(78.15)

4400

(124.59)

7780

(220.30)

(2.69)

199

(5.63)

374

(10.59)

768

(22.25)

1150

(32.56)

2220

(62.86)

3530

(99.95)

6250

(176.98)

(18.60)

(27.89)

(53.80)

(85.51)

(151.49)

NOTE − Capacity given in cubic feet (m3 ) of gas per hour and based on 0.60 specific gravity gas.

Length of Pipe − feet (m)

(2.29)

170

(4.81)

320

(9.06)

657

985

1900

3020

5350

(2.03)

151

(4.28)

284

(8.04)

583

(16.50)

873

(24.72)

1680

(47.57)

2680

(75.88)

4740

(134.22)

(1.84)

137

(3.87)

257

(7.27)

528

(14.95)

791

(22.39)

1520

(43.04)

2480

(70.22)

4290

(121.47)

(1.69)

126

(3.56)

237

(6.71)

486

(13.76)

728

(20.61)

1400

(39.64)

2230

(63.14)

3950

(111.85)

(1.58)

117

(3.31)

220

(6.23)

452

(12.79)

677

(19.17)

1300

(36.81)

2080

(58.89)

3670

(103.92)

(1.47)

110

(3.11)

207

(5.86)

424

(12.00)

635

(17.98)

1220

(34.55)

1950

(55.22)

3450

(97.69)

100

(30.480)

(1.42)

104

(2.94)

195

(5.52)

400

(11.33)

600

(17.00)

1160

(32.844)

1840

(52.10)

3260

(92.31)

Page 23

MANUAL

MAIN SHUT−OFF

VALV E

(With 1/8 in. NPT

Plugged Tap Shown)

GROUND

JOINT

UNION

Left Side Piping

(Standard)

AUTOMATIC

GAS VALVE

AUTOMATIC

GAS VALVE

MANUAL

MAIN SHUT−OFF

VALV E

(With 1/8 in. NPT

Plugged Tap

Shown)

GROUND

JOINT

UNION

DRIP LEG

MANUAL

MAIN SHUT−OFF

VALV E

GROUND

JOINT

UNION

DRIP LEG

FIELD

PROVIDED

AND INSTALLED

NOTE − BLACK IRON PIPE ONLY TO BE ROUTED INSIDE OF CABINET

FIGURE 26

Horizontal Applications

Possible Gas Piping Configurations

MANUAL

MAIN SHUT−OFF

VALV E

GROUND

JOINT

UNION

DRIP LEG

Right Side Piping

(Alternate)

Horizontal Application

Left−Side Air Discharge

MANUAL

MAIN SHUT−OFF

VALV E

Horizontal Application

Right−Side Air Discharge

FIELD

PROVIDED

AND INSTALLED

NOTE − BLACK IRON PIPE ONLY TO BE ROUTED INSIDE OF CABINET

FIGURE 27

GROUND

JOINT UNION

DRIP LEG

Page 24

Leak Check

After gas piping is completed, carefully check all piping connections (factory− and field−installed) for gas leaks. Use a leak detecting solution or other preferred means.

NOTE − If emergency shutoff is necessary, shut off the main manual gas valve and disconnect the main power to the furnace. The installer should properly label these devices.

The unit is equipped with a field make−up box on the left hand side of the cabinet. The make−up box may be moved to the right side of the furnace to facilitate installation. If the make−up box is moved to the right side, clip the wire ties that bundle the wires together. The excess wire must be pulled into the blower compartment. Secure the excess wire to the existing harness to protect it from damage.

INTERIOR MAKE−UP BOX INSTALLATION

CAUTION

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

The furnace must be isolated by closing its individual manual shut-off valve and disconnecting from from the gas supply system the during any pressure testing of the gas supply system at pressures greater than 1/2 psig (3.48 kPa, 14 inches w.c.).

IMPORTANT

When testing pressure of gas lines, gas valve must be disconnected and isolated. See figure 28. Gas valves can be damaged if subjected to pressures greater than 1/2 psig (3.48 kPa, 14 inches w.c.).

MANUAL MAIN

SHUT−OFF VALVE

WILL NOT HOLD

NORMAL TEST

PRESSURE

1/8 NPT PLUG

ISOLATE

GAS VALVE

FURNACE

Right Side

BOX

FIGURE 29

INTERIOR MAKE−UP BOX INSTALLATION

Left side

BOX

CAP

FIGURE 28

Electrical

ELECTROSTATIC DISCHARGE (ESD)

Precautions and Procedures

CAUTION

Electrostatic discharge can affect electronic components. Take precautions during furnace installation and service to protect the furnace’s electronic controls. Precautions will help to avoid control exposure to electrostatic discharge by putting the furnace, the control and the technician at the same electrostatic potential. Neutralize electrostatic charge by touching hand and all tools on an unpainted unit surface, such as the gas valve or blower deck, before performing any service procedure.

FIGURE 30

Refer to figure 32 for schematic wiring diagram and troubleshooting and figure 33 for field wiring.

The power supply wiring must meet Class I restrictions. Protected by either a fuse or circuit breaker, select circuit protection and wire size according to unit nameplate.

NOTE − Unit nameplate states maximum current draw. Maximum over−current protection allowed is 15 AMP.

Holes are on both sides of the furnace cabinet to facilitate wiring.

Install a separate (properly sized) disconnect switch near the furnace so that power can be turned off for servicing.

Page 25

Before connecting the thermostat, check to make sure the wires will be long enough for servicing at a later date. Make sure that thermostat wire is long enough to facilitate future removal of blower for service.

Complete the wiring connections to the equipment. Use the provided unit wiring diagram and the field wiring diagram shown in figure 33. Use 18−gauge wire or larger that is suitable for Class II rating for thermostat connections.

Electrically ground the unit according to local codes or, in the absence of local codes, according to the current National Electric Code (ANSI/NFPA No. 70). A green ground wire is provided in the field make−up box.

NOTE − The ML180UH furnace contains electronic components that are polarity sensitive. Make sure that the furnace is wired correctly and is properly grounded.

 The furnace requires 120 volts + 10% (Range: 108

volts to 132 volts).

 The furnace operates at 60 Hz +

5% (Range: 57 Hz to

63 Hz).

 The furnace integrated control requires both polarity

and proper ground. Both polarity and proper grounding should be checked before attempting to operate the furnace on either permanent or temporary power.

 Generator should have a wave form distortion of less

than 5% RHD.

Thermostat

Install the room thermostat according to the instructions provided with the thermostat. See figure 31 for thermostat designations. If the furnace is being matched with a heat pump, refer to the FM21 installation instruction or appropriate dual fuel thermostat instructions.

Accessory Terminals

One line voltage EAC" 1/4" spade terminal is provided on the furnace integrated control. See figure 34 for integrated control configuration. This terminal is energized when the indoor blower is operating. Any accessory rated up to one amp can be connected to this terminal with the neutral leg of the circuit being connected to one of the provided neutral terminals. If an accessory rated at greater than one amp is connected to this terminal, it is necessary to use an external relay.

One line voltage HUM" 1/4" spade terminal is provided on the furnace integrated control. See figure 34 for integrated control configuration. This terminal is energized in the heating mode when the combustion air inducer is operating. Any humidifier rated up to one amp can be connected to this terminal with the neutral leg of the circuit being connected to one of the provided neutral terminals. If a humidifier rated at greater than one amp is connected to this terminal, it is necessary to use an external relay relay.

Generator Use − Voltage Requirements

The following requirements must be kept in mind when specifying a generator for use with this equipment:

ML180UH and CONDENSING UNIT

(Refer to specific thermostat and outdoor unit.)

Thermostat Furnace Condensing

THERMOSTAT DESIGNATIONS

Unit

POWER

HEAT

COOLING

INDOOR BLOWER

COMMON

*NOTE − R" REQUIRED ON SOME OUTDOOR UNITS

*CONDENSING

CONDENSING

UNIT COMMON

UNIT

FIGURE 31

Indoor Blower Speeds

1 − When the thermostat is set to FAN ON," the indoor

blower will run continuously on the heating speed when there is no cooling or heating demand.

2 − When the ML180UH is running in the heating mode,

the indoor blower will run on the heating speed.

3 − When there is a cooling demand, the indoor blower will

run on the cooling speed.

Page 26

ML180UH Schematic Wiring Diagram and Sequence of Operation

1 − When there is a call for heat, W1 of the thermostat energizes W of the furnace control with 24VAC.

2 − Integrated control runs a self−check. S10 primary limit, S47 rollout switch and S21 secondary limit contacts are found to be closed. Call for

heat can continue.

3 − Integrated control (A92) energizes combustion air inducer B6. Combustion air inducer runs until S18 combustion air pressure switch closes .

Once S18 closes, a 15−second pre−purge follows.

4 − Integrated control (A92) energizes ignitor. A 20−second warm−up period begins.

5 − Gas valve opens for a 4−second trial for ignition

6 − Flame is sensed, gas valve remains open for the heat call.

7 − After 45−second delay, integrated control (A92) energizes indoor blower B3.

8 − When heat demand is satisfied, W1 of the indoor thermostat de−energizes W of the ignition control which de−energizes the gas valve

Combustion air inducer B6 continues a 5−second post−purge period, and indoor blower B3 completes a selected OFF time delay.

FIGURE 32

Page 27

TYPICAL ML180UH FIELD WIRING DIAGRAM

IGNITOR

*NOTE − R" REQUIRED ON SOME OUTDOOR UNITS

FIGURE 33

INTEGRATED CONTROL

(Automatic Hot Surface Ignition System)

TERMINAL DESIGNATIONS

HUM LINE XFMR EAC COOL HEAT PARK FLAME NEUTRALS

3 AMP, 32 VAC FUSE

Humidifier (120VAC) Input (120VAC) Transformer (120VAC) Electronic Air Cleaner (120VAC) Blower − Cooling Speed (120VAC) Blower − Heating Speed (120VAC) Dead terminals to park alternate speed taps Flame sensor Neutral terminals (120VAC)

HEAT FAN OFF

DELAY JUMPER

FIGURE 34

Page 28

Unit Start−Up

FOR YOUR SAFETY READ BEFORE LIGHTING

WARNING

Do not use this furnace if any part has been underwater. A flood−damaged furnace is extremely dangerous. Attempts to use the furnace can result in fire or explosion. Immediately call a qualified service technician to inspect the furnace and to replace all gas controls, control system parts, and electrical parts that have been wet or to replace the furnace, if deemed necessary.

WARNING

If overheating occurs or if gas supply fails to shut off, shut off the manual gas valve to the appliance before shutting off electrical supply.

CAUTION

Before attempting to perform any service or maintenance, turn the electrical power to unit OFF at disconnect switch.

BEFORE LIGHTING smell all around the appliance area for

gas. Be sure to smell next to the floor because some gas is heavier than air and will settle on the floor.

The gas valve on the ML180UH unit will be equipped with a gas control switch. Use only your hand to move the switch. Never use tools. If the switch will not turn or if the control switch will not move by hand, do not try to repair it.

Placing the furnace into operation:

ML180UH units are equipped with an automatic ignition system. Do not attempt to manually light burners on these furnaces. 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 an automatic ignition system.

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 35)

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 switch on gas valve to OFF. Do not force. See

figure 35.

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 instructions. If you do not smell gas go to next step.

MANIFOLD

PRESSURE

ADJUSTMENT

SCREW

INLET

PRESSURE

PORT

8 − Move switch on gas valve to ON. Do not force. See fig-

ure 35.

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 technician 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 switch on gas valve to OFF. Do not force. 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 circuit 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 lock out? If the unit locks out

again, call the service technician to inspect the unit for

blockages. 10 − Is pressure switch closed? Obstructed flue will cause

unit to shut off at pressure switch. Check flue and outlet

for blockages.

GAS VALVE SHOWN IN ON POSITION

FIGURE 35

MANIFOLD

PRESSURE

OUTLET

PORT

Page 29

11 − Are flame rollout switches tripped? If flame rollout

switches are tripped, call the service technician for inspection.

Heating Sequence Of Operation (follow steps below or see Figure 32 for more detail)

1 − When thermostat calls for heat, combustion air blower

starts.

2 − Combustion air pressure switch proves blower opera-

tion. Switch is factory−set and requires no adjustment.

3 − After a 15−second prepurge, the hot surface ignitor en-

ergizes.

4 − After a 20−second ignitor warm−up period, the gas

valve solenoid opens. A 4−second trial for ignition period begins.

5 − Gas is ignited, flame sensor proves the flame, and the

combustion process continues.

6 − If flame is not detected after first ignition trial, the igni-

tion control will repeat steps 3 and 4 four more times before locking out the gas valve (WATCHGUARD" flame failure mode). The ignition control will then automatically repeat steps 1 through 6 after 60 minutes.

7 − To interrupt the 60−minute WATCHGUARD" period,

move thermostat from Heat" to OFF" then back to Heat." Heating sequence then restarts at step 1.

Gas Pressure Adjustment

Gas Flow (Approximate)

TABLE 10

GAS METER CLOCKING CHART

Seconds for One Revolution

ML180UH

Unit

−045 80 160 200 400

−070 55 110 136 272

−090 41 82 102 204

−110 33 66 82 164

−135 27 54 68 136

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

Furnace should operate at least 5 minutes before checking 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 10 below. If manifold pressure matches table 12 and rate is incorrect, check gas orifices for proper size and restriction. Remove temporary gas meter if installed.

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

Natural LP

1 cu ft

Dial

2 cu ft

Dial

1 cu ft

Dial

2 cu ft

DIAL

Supply Pressure Measurement

A threaded plug on the inlet side of the gas valve provides access to the supply pressure tap. Remove the threaded plug, install a field−provided barbed fitting and connect a manometer to measure supply pressure. See table 12 for proper line pressure. Replace the threaded plug after measurements have been taken.

Manifold Pressure Measurement

1 − Remove the threaded plug from the outlet side of the

gas valve and install a field−provided barbed fitting. Connect to a manometer to measure manifold pressure.

2 − Start unit and allow 5 minutes for unit to reach steady

state.

3 − While waiting for the unit to stabilize, observe the

flame. Flame should be stable and should not lift from burner. Natural gas should burn blue.

4 − After allowing unit to stabilize for 5 minutes, record

manifold pressure and compare to value given in table

12.

NOTE − Shut unit off and remove manometer as soon as an accurate reading has been obtained. Take care to remove barbed fitting and replace threaded plug.

Proper Combustion

Furnace should operate a minimum 15 minutes with correct manifold pressure and gas flow rate before checking combustion. Take combustion sample beyond the flue outlet and compare to the tables below. The maximum car-

bon monoxide reading should not exceed 50 ppm.

TABLE 11

ML180UH

Unit

−045

−070

−090

−110

−135

CO2%

For Nat

7.2 − 7.8 7.5 − 9.0

CO2%

For L.P.

High Altitude

The manifold pressure may require adjustment and combustion air pressure switch may need replacing to ensure proper combustion at higher altitudes. Refer to table 12 for manifold pressure and table 13 for pressure switch change and gas conversion kits.

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.

Page 30

TABLE 12

Manifold Pressure Settings at all Altitudes

Model

Input Size

045

070

090

110

135

Gas 0−2000 ft 2105−4500 ft. 4501−7500 ft 7501 − 10,000 ft

Nat 3.5 3.2 3.0 3.5 4.5 13.0

LP/propane 10.0 10.0 10.0 10.0 11.0 13.0

Nat 3.5 3.2 2.8 3.5 4.5 13.0

LP/propane 10.0 10.0 10.0 10.0 11.0 13.0

Nat 3.5 3.2 2.7 3.5 4.5 13.0

LP/propane 10.0 10 9.6 10.0 11.0 13.0

Nat 3.5 3.5 3.0 3.5 4.5 13.0

LP/propane 10.0 10.0 9.6 10.0 11.0 13.0

Nat 3.5 3.5 2.9 3.5 4.5 13.0

LP/propane 10.0 10.0 9.6 10.0 11.0 13.0

Pressure Switch and Gas Conversion Kits at all Altitudes

Model

Input Size

045

070 80W52 80W51

090 80W52 80W51

110 80W57 80W52

135 80W52 80W51

High Altitude Pressure Switch Kit

0−4500 ft 4501−7500 ft 7501 − 10,000 ft 7501 − 10,000 ft 0 − 7500 ft 7501 − 10,000 ft 0 − 7500 ft

80W52 80W51

No Change

TABLE 13

High Altitude

Natural Gas Burner

Orifice Kit

73W37 70W89 76W15 73W81

Natural Gas to LP/Propane

Burner Orifice Kit

Line Pressure in.wg.

Min Max

LP/Propane to

Natural Gas Burner

Orifice Kit

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.

Other Unit Adjustments

air temperatures have been allowed to stabilize, check the temperature rise. If necessary, adjust the blower speed to

Primary and Secondary Limits

The primary limit is located on the heating compartment vestibule panel. The secondary limits (if equipped) are located in the blower compartment, attached to the back side of the blower. These auto reset limits are factory−set and require no adjustment.

Flame Rollout Switches

This manually reset switches are located on the top of the burner box.

Pressure Switch

The pressure switch is located in the heating compartment adjacent to the combustion air inducer. The switch checks for proper combustion air inducer operation before allowing ignition trial. The switch is factory−set and requires no adjustment.

Temperature Rise

After the furnace has been started, and supply and return

maintain the temperature rise within the range shown on the unit nameplate. Increase the blower speed to decrease the temperature. Decrease the blower speed to increase the temperature rise. Failure to adjust the temperature rise may cause erratic limit operation.

Fan Control

The fan−on time of 30 seconds is not adjustable. The heat fan−off delay (amount of time that the blower operates after the heat demand has been satisfied) may be adjusted by changing the jumper position across the five pins on the integrated control. The unit is shipped with a factory fan−off delay setting of 90 seconds. The fan−off delay affects comfort and is adjustable to satisfy individual applications. Adjust the fan−off delay to achieve a supply air temperature between 90° and 110°F at the moment that the blower is de−energized. Longer off delay settings provide lower return air temperatures; shorter settings provide higher return air temperatures. See figure 36.

Page 31

HEAT FAN-OFF TIME IN SECONDS

Blower Speeds

Follow the steps below to change the blower speeds.

1 − Turn off electrical power to furnace.

2 − Remove blower access panel.

NO JUMPER

To adjust fan−off timing, reposition jumper across pins to

60 Second

off Time

120

180

achieve desired setting.

90 Second

off Time

120

180

120 Second

off Time

120

180

180 Second

off Time

120

180

FIGURE 36

Thermostat Heat Anticipation

Set the heat anticipator setting (if adjustable) according to the amp draw listed on the wiring diagram that is attached to the unit.

NOTE − Do not secure the electrical conduit directly to the air ducts or structure.

Electrical

1 − Check all wiring for loose connections. 2 − Check for the correct voltage at the furnace (furnace

operating). Correct voltage is 120VAC + 10%.

3 − Check amp−draw on the blower motor with inner blow-

er panel in place. Unit Nameplate__________Actual__________

3 − Disconnect existing speed tap at integrated control

speed terminal.

NOTE − Termination of any unused motor leads must be insulated.

4 − Place unused blower speed tap on integrated control

PARK" terminal or insulate.

5 − Refer to blower speed selection chart on unit wiring dia-

gram for desired heating or cooling speed. See Blower performance data beginning on the next page.

6 − Connect selected speed tap at integrated control

speed terminal.

7 − Resecure blower access panel.

8 − Turn on electrical power to furnace.

9 − Recheck temperature rise.

Electronic Ignition

The integrated control has an added feature of an internal Watchguard control. The feature serves as an automatic reset device for integrated control lockout caused by ignition failure. This type of lockout is usually due to low gas line pressure. After one hour of continuous thermostat demand for heat, the Watchguard will break and remake thermostat demand to the furnace and automatically reset the integrated control to begin the ignition sequence.

Page 32

BLOWER DATA

ML180UH045P24A PERFORMANCE (Less Filter)

External

Static

Pressure

in. w.g.

0.00 1130 453 900 328 750 261 680 237

0.10 1115 432 885 321 735 255 670 230

0.20 1100 413 870 315 720 249 655 223

0.30 1070 396 855 304 700 241 640 217

0.40 1030 375 830 294 685 234 620 209

0.50 990 356 800 283 655 223 590 200

0.60 930 335 750 261 610 207 535 186

0.70 870 315 705 245 540 193 490 175

0.80 785 285 615 223 455 175 405 158

0.90 615 247 485 196 375 157 345 143

ML180UH045P36A PERFORMANCE (Less Filter)

External

Static

Pressure

in. w.g.

0.00 1670 711 1335 614 1140 485 925 388

0.10 1620 663 1335 577 1130 470 940 376

0.20 1570 619 1330 543 1115 455 950 366

0.30 1525 598 1315 511 1140 432 950 349

0.40 1470 552 1275 491 1125 413 945 336

0.50 1400 525 1235 455 1085 384 925 317

0.60 1330 486 1185 422 1050 361 885 300

0.70 1225 450 1135 395 995 336 840 283

0.80 1135 418 1010 359 925 315 785 258

0.90 1020 388 930 329 820 278 650 227

Air Volume / Watts at Various Blower Speeds

High

cfm Watts cfm Watts cfm Watts cfm Watts

Air Volume / Watts at Various Blower Speeds

High

cfm Watts cfm Watts cfm Watts cfm Watts

Medium-

High

Medium-

High

Medium-

Low

Medium-

Low

ML180UH070P36A PERFORMANCE (Less Filter)

External

Static

Pressure

in. w.g.

0.00 1660 696 1370 604 1095 495 935 386

0.10 1620 658 1365 568 1115 468 945 374

0.20 1580 621 1355 535 1135 442 960 362

0.30 1520 595 1335 513 1130 423 955 350

0.40 1480 562 1300 478 1100 403 945 335

0.50 1400 520 1270 450 1080 382 925 320

0.60 1340 490 1205 420 1035 358 880 301

0.70 1245 458 1125 393 975 333 835 282

0.80 1160 434 1045 364 915 310 775 262

0.90 1045 393 940 334 830 283 785 268

ML180UH090P36B PERFORMANCE (Less Filter)

External

Static

Pressure

in. w.g.

0.00 1795 781 1450 606 1195 464 970 390

0.10 1760 730 1435 576 1185 452 970 378

0.20 1725 683 1420 547 1170 440 975 368

0.30 1685 656 1410 525 1170 420 980 356

0.40 1630 625 1370 501 1150 400 955 340

0.50 1535 569 1315 469 1125 391 925 326

0.60 1470 533 1275 440 1085 367 910 309

0.70 1365 490 1185 407 1020 344 840 290

0.80 1255 466 1105 380 935 314 785 266

0.90 1160 430 1000 352 815 285 680 258

Air Volume / Watts at Various Blower Speeds

High

cfm Watts cfm Watts cfm Watts cfm Watts

Air Volume / Watts at Various Blower Speeds

High

cfm Watts cfm Watts cfm Watts cfm Watts

Medium-

High

Medium-

High

Medium-

Low

Medium-

Low

ML180UH070P24A PERFORMANCE (Less Filter)

External

Static

Pressure

in. w.g.

0.00 1160 450 1005 380 865 309

0.10 1135 439 990 369 845 299

0.20 1115 429 975 358 820 289

0.30 1085 410 955 348 790 279

0.40 1045 389 925 335 775 270

0.50 1015 374 885 321 735 260

0.60 965 358 835 307 700 248

0.70 890 335 780 289 635 232

0.80 810 315 700 268 560 214

0.90 715 289 565 238 420 189

Air Volume / Watts at Various Blower Speeds

High Medium Low

cfm Watts cfm Watts cfm Watts

Page 33

ML180UH090P48B PERFORMANCE (Less Filter)

External

Static

Pressure

in. w.g.

0.00 2160 873 1825 775 1515 649 1260 544

0.10 2030 804 1780 719 1525 613 1280 518

0.20 1910 740 1740 666 1535 580 1305 493

0.30 1840 698 1705 643 1500 551 1305 474

0.40 1770 664 1635 594 1460 517 1280 445

0.50 1665 625 1560 567 1410 483 1225 420

0.60 1585 595 1470 523 1330 451 1190 391

0.70 1470 561 1365 483 1260 421 111 5 368

0.80 1355 514 1230 433 1155 392 1020 338

0.90 1200 471 1120 399 1020 345 920 315

Air Volume / Watts at Various Blower Speeds

High

cfm Watts cfm Watts cfm Watts cfm Watts

Medium-

High

Medium-

Low

BLOWER DATA

ML180UH110P48C PERFORMANCE (Less Filter)

External

Static

Pressure

in. w.g.

0.00 2170 980 1845 792 1565 678 1270 564

0.10 2125 919 1820 747 1555 648 1300 540

0.20 2080 862 1790 705 1540 619 1335 516

0.30 2015 807 1745 652 1545 587 1335 498

0.40 1940 748 1695 629 1505 552 1320 470

0.50 1850 716 1635 581 1470 523 1295 449

0.60 1775 679 1575 560 1395 484 1235 417

0.70 1680 637 1470 508 1320 450 1170 387

0.80 1560 592 1350 469 1205 404 1050 345

0.90 1425 546 1190 424 1060 362 910 307

ML180UH110P60C PERFORMANCE (Less Filter)

External

Static

Pressure

in. w.g.

0.00 2575 1391 2270 1050 1845 860 1430 661 2715 1509 2175 1103 1695 858 1410 653

0.10 2520 1359 2250 1034 1860 841 1455 654 2605 1454 2160 1060 1740 848 1430 651

0.20 2465 1329 2230 1018 1870 823 1480 647 2505 1401 2150 1018 1785 838 1450 649

0.30 2385 1307 2180 981 1885 809 1540 646 2435 1349 2115 991 1795 818 1485 638

0.40 2295 1256 2105 942 1865 778 1570 638 2350 1308 2070 965 1805 801 1480 631

0.50 2200 1214 2055 909 1845 762

0.60 2130 1186 1985 882 1795 741 1550 604 2175 1228 1955 901 1755 752 1490 611

0.70 2015 1150 1890 848 1720 711 1505 580 2085 1186 1850 853 1710 722 1460 594

0.80 1905 1105 1810 815 1675 687 1470 565 1965 1147 1785 818 1640 689 1425 567

0.90 1795 1054 1710 779 1545 647 1375 533 1830 1094 1700 794 1555 662 1355 545

Bottom Return Air, Side Return Air with Optional Return Air Base, Return Air from Both Sides or Return Air from Bottom and One Side.

High Medium-High Medium-Low Low High Medium-High Medium-Low Low

cfm Watts cfm Watts cfm Watts cfm Watts cfm Watts cfm Watts cfm Watts cfm Watts

Air Volume / Watts at Various Blower Speeds

High

cfm Watts cfm Watts cfm Watts cfm Watts

Air Volume / Watts at Different Blower Speeds

Medium-

High

1570 619 2260 1274 2010 929 1785 775 1480 621

Medium-

Low

Single Side Return Air − Air volumes in bold require eld

fabricated transition to accommodate 20 x 25 x 1 in. air lter in order to maintain proper air velocity.

Low

ML180UH135P60D PERFORMANCE (Less Filter)

Air Volume / Watts at Different Blower Speeds

External

Static

Pressure

in. w.g.

0.00 2785 1492 2205 1083 1665 840 1345 632 2810 1528 2185 1100 1705 835 1260 622

0.10 2750 1441 2220 1056 1725 825 1395 625 2725 1463 2180 1075 1715 827 1320 624

0.20 2720 1392 2235 1029 1785 810 1445 618 2640 1400 2180 1051 1720 819 1380 626

0.30 2605 1362 2220 1002 1820 800 1460 623 2575 1374 2165 1005 1790 803 1420 622

0.40 2495 1312 2185 968 1845 779 1485 616 2495 1343 2145 988 1775 791 1450 617

0.50 2420 1275 2135 939 1825 767

0.60 2335 1234 2080 909 1825 753 1495 593 2305 1257 2045 914 1775 753 1480 593

0.70 2220 1190 1995 864 1760 716 1475 576 2215 1214 1970 884 1740 727 1455 583

0.80 2120 1157 1890 835 1680 686 1435 558 2110 1170 1890 851 1675 699 1430 565

0.90 1985 1102 1790 794 1605 656 1390 536 1985 1122 1790 811 1600 667 1380 543

Bottom Return Air, Side Return Air with Optional Return Air Base, Return Air from Both Sides or Return Air from Bottom and One Side.

High Medium-High Medium-Low Low High Medium-High Medium-Low Low

cfm Watts cfm Watts cfm Watts cfm Watts cfm Watts cfm Watts cfm Watts cfm Watts

1505 605 2405 1292 2105 948 1780 777 1470 610

Single Side Return Air − Air volumes in bold require eld

fabricated transition to accommodate 20 x 25 x 1 in. air lter in order to maintain proper air velocity.

Page 34

Service

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 operation, serious injury, death, or property damage. Before servicing, disconnect all electrical power to furnace. When servicing controls, label all wires prior to disconnecting. Take care to reconnect wires correctly. Verify proper operation after servicing.

At the beginning of each heating season, a qualified technician should check the system as follows:

Blower

Check the blower wheel for debris and clean if necessary. The blower motors are prelubricated for extended bearing life. No further lubrication is needed.

WARNING

Filters

All ML180UH filters are installed external to the unit. Filters should be inspected monthly. Clean or replace the filters when necessary to ensure that the furnace operates properly. Replacement filters must be rated for high velocity airflow. Table 1 lists recommended filter sizes.

Flue And Chimney

1 − Check flue pipe, chimney and all connections for tight-

ness and to make sure there is no blockage. 2 − Check unit for proper draft.

Electrical

1 − Check all wiring for loose connections. 2 − Check for the correct voltage at the furnace (furnace

operating). Correct voltage is 120VAC + 10%.

3 − Check amp−draw on the blower motor with inner blow-

er panel in place.

Unit Nameplate__________Actual__________

Page 35

Cleaning the Heat Exchanger and Burners

NOTE − Use papers or protective covering in front of the furnace during cleaning.

1 − Turn off both electrical and gas power supplies to fur-

nace.

2 − Remove flue pipe and top cap (some applications top

cap can remain) from the unit.

3 − Label the wires from gas valve, rollout switches, prima-

ry limit switch and make−up box then disconnect them.

4 − Remove the screws that secure the combustion air in-

ducer/pressure switch assembly to the collector box. Carefully remove the combustion air inducer to avoid damaging blower gasket. If gasket is damaged, it must be replaced to prevent leakage.

ML180UH BURNER, COMBUSTION AIR INDUCER ASSEMBLY &

HEAT EXCHANGER REMOVAL

Flue Transition

Pressure Switch

5 − Remove the collector box located behind the combus-

tion air inducer. Be careful with the collector box gasket. If the gasket is damaged, it must be replaced to prevent leakage.

6 − Disconnect gas supply piping. Remove the screw se-

curing the burner box cover and remove cover. Remove the four screws securing the burner manifold assembly to the vestibule panel and remove the assembly from the unit.

7 − Remove screws securing burner box and remove

burner box.

8 − NOX units only − Remove screw securing NOX insert.

Remove NOX insert. See figure 38.

Gasket

Rollout Switches

(−090, −110 −135 units)

Rollout Switches

(−045 and −070 units)

Sensor

Ignitor

Manifold And Gas Valve

Orifice Plate

Combustion Air Inducer

FIGURE 37

Heat Exchanger

Collector Box

Retention Rings

Cross Over

Page 36

9 − Remove screws from both sides, top and bottom of

vestibule panel.

10 − Remove heat exchanger. It may be necessary to

spread cabinet side to allow more room. If so, remove five screws from the left side or right side of cabinet. See figure 39.

11 − Backwash using steam. Begin from the burner opening

on each clam. Steam must not exceed 275°F.

12 −To clean burners, run a vacuum cleaner with a soft brush

attachment over the face of burners. Visually inspect inside the burners and crossovers for any blockage caused by foreign matter. Remove any blockage. Figure 37 shows burner detail.

13 − To clean the combustion air inducer visually inspect and

using a wire brush clean where necessary. Use compressed air to clean off debris and any rust.

14 −Reinstall heat exchanger in vestibule. (Replace the

five screws in the cabinet from step 10 if removed).

15 − NOx units only − Replace NOx inserts.

16 − Reinstall collector box and combustion air assembly.

Reinstall all screws to the collector box and combustion air inducer. Failure to replace all screws may cause leaks. Inspect gaskets for any damage and replace if necessary.

17 − Reinstall burner box, manifold assembly and burner box

cover.

ML180UH NOx INSERTS

Remove 5 screws if necessary

(either side of cabinet)

FIGURE 39

18 − Reconnect all wires.

19 −Reconnect top cap and vent pipe to combustion air in-

ducer outlet.

NOx Insert

FIGURE 38

20 −Reconnect gas supply piping.

21 −Turn on power and gas supply to unit.

22 −Set thermostat and check for proper operation.

23 −Check all piping connections, factory and field, for gas

leaks. Use a leak detecting solution or other preferred

means.

CAUTION

24 −If a leak is detected, shut gas and electricity off and

repair leak.

25 −Repeat steps 24 and 26 until no leaks are detected.

26 −Replace access panel.

Page 37

Planned Service

The following items should be checked during an annual inspection. Power to the unit must be shut off for the service technician’s safety.

Fresh air grilles and louvers (on the unit and in the room where the furnace is installed) − Must be open and unobstructed to provide combustion air.

Operating performance − Unit must be observed during operation to monitor proper performance of the unit and the vent system.

Burners − Must be inspected for rust, dirt, or signs of water.

Vent pipe − Must be inspected for signs of water, damaged

or sagging pipe, or disconnected joints.

Unit appearance − Must be inspected for rust, dirt, signs of water, burnt or damaged wires, or components.

Blower access panel − Must be properly in place and provide a seal between the return air and the room where the furnace is installed.

Return air duct − Must be properly attached and provide an air seal to the unit.

Combustion gases − Flue products must be analyzed and compared to the unit specifications.

Problems detected during the inspection may make it necessary to temporarily shut down the furnace until the items can be repaired or replaced.

Instruct the homeowners to pay attention to their furnace. Situations can arise between annual furnace in-

spections that may result in unsafe operation. For instance, items innocently stored next to the furnace may obstruct the combustion air supply. This could cause incomplete combustion and the production of carbon monoxide gas.

Repair Parts List

The following repair parts are available through independent Lennox dealers. When ordering parts, include the complete furnace model number listed on the CSA International nameplate −− Example: ML180UH045P24A−01. All service must be

performed by a licensed professional installer (or equivalent), service agency, or gas supplier.

Cabinet Parts

Upper access panel Blower panel Top cap

Control Panel Parts

Transformer Integrated control Door interlock switch Circuit breaker

Blower Parts

Blower wheel Blower housing Motor Motor mounting frame Motor capacitor Blower housing cutoff plate

Heating Parts

Flame sensor Heat exchanger assembly Gas manifold Combustion air inducer Gas valve Main burner cluster Main burner orifices Pressure switch Ignitor Primary limit control Flame rollout switch (s) Secondary limit

Page 38

Integrated Control Diagnostic Codes

DIAGNOSTIC CODES

Make sure to Identify LED’S Correctly.

LED #1 (Red) LED #2 (Green) DESCRIPTION

SIMULTANEOUS

SLOW FLASH

SIMULTANEOUS

FAST FLASH

SLOW FLASH ON

OFF SLOW FLASH

ALTERNATING

SLOW FLASH

SLOW FLASH OFF Flame sensed without gas valve energized.

ON SLOW FLASH Rollout switch open. OR: 12-pin connector improperly attached.

SIMULTANEOUS

SLOW FLASH

SIMULTANEOUS

FAST FLASH

ALTERNATING

SLOW FLASH

Power on − Normal operation. Also signaled during cooling and continuous fan.

Normal operation − signaled when heating demand initiated at thermostat.

Primary or secondary limit switch open. Limit must close within 3 minutes or unit goes into 1 hour Watchguard.

Pressure prove switch open. OR: Blocked inlet/exhaust vent; OR: Pressure switch closed prior to activation of combustion air inducer.

Watchguard 1 hour − burners failed to ignite or lost flame 5 times during single heating demand.

OFF

Circuit board failure or control wired incorrectly.

FAST FLASH SLOW FLASH Main power polarity reversed. Switch line and neutral.

SLOW FLASH FAST FLASH Low flame signal. Measures below 1.5 microamps. Replace flame sense rod.

ALTERNATING

FAST FLASH

ALTERNATING

FAST FLASH

Improper main ground. OR: Line voltage below 90 volts.

NOTE − Slow flash rate equals 1 Hz (one flash per second). Fast flash rate equals 3 Hz (three flashes per second). Minimum flame sense current = 0.5 microAmps.

Page 39

Troubleshooting: Heating Sequence of Operation

HEATING SEQUENCE OF OPERATION

NORMAL HEATING MODE

POWER ON

CONTROL SELF−CHECK OKAY?

YES

IS POLARITY CORRECT?

YES

IS THERE A PROPER GROUND?

YES

IS VOLTAGE

ABOVE 90 VOLTS?

YES

ROLLOUT SWITCH CLOSED?

YES

ABNORMAL HEATING MODE

GAS VALVE OFF. COMBUSTION AIR INDUCER OFF.

(RESET CONTROL BY TURNING MAIN POWER OFF.)

CONTROL WILL NOT RESPOND TO A CALL FOR

HEATING UNTIL VOLTAGE RISES ABOVE 95 VOLTS.

GAS VALVE OFF. COMBUSTION AIR INDUCER ON.

SEQUENCE HOLDS UNTIL ROLLOUT SWITCH CLOSES

AND POWER IS RESET OR T’STAT IS INTERRUPTED

INDOOR BLOWER DELAY OFF.

LED #1 ON LED #2 ON

POLARITY REVERSED.

LED #1 −− FAST FLASH

LED #2 −− SLOW FLASH

IMPROPER GROUND. LED #1 −− ALTERNATING FAST FLASH LED #2 −− ALTERNATING FAST FLASH

LEDs SIGNAL FAST ALTERNATING FLASH.

INDOOR BLOWER ON.

LED #1 −− ON. LED #2 −− SLOW FLASH.

FOR MINIMUM OF 1 SECOND.

(Flame sensed without gas valve energized)

BURNER OFF?

YES

NORMAL OPERATION:

LED #1 −− SLOW FLASH LED #2 −− SLOW FLASH

YES

THERMOSTAT CALLS FOR HEAT:

LED #1 −− FAST FLASH LED #2 −− FAST FLASH

YES

PRIMARY AND SECONDARY LIMIT SWITCH.

CLOSED?

YES

IS COMBUSTION AIR

PRESSURE SWITCH OPEN?

YES

IS COMBUSTION AIR INDUCER

ENERGIZED?

YES

HAS COMBUSTION AIR PRESSURE

SWITCH CLOSED IN 2.5 MINUTES?

YES

CONTINUED NEXT PAGE

GAS VALVE OFF. COMBUSTION AIR INDUCER ON.

INDOOR BLOWER ON HEATING SPEED.

PRESSURE SWITCH IS IN WATCHGUARD MODE.

GAS VALVE OFF. COMBUSTION AIR INDUCER OFF.

INDOOR BLOWER OFF WITH DELAY.

LED #1 −− OFF. LED #2 −− SLOW FLASH.

IS 5-MINUTE RESET PERIOD COMPLETE?

LED #1 −− SLOW FLASH

LED #2 −− OFF

COMBUSTION AIR INDUCER OFF.

INDOOR BLOWER ON

LED #1 SLOW FLASH RATE

LED #2 −− ON

GAS VALVE OFF.

COMBUSTION AIR INDUCER OFF.

INDOOR BLOWER OFF WITH DELAY.

LED #1 OFF

LED #2 SLOW FLASH

(Sequence holds until pressure switch

opens or thermostat resets control.)

YES

Page 40

Troubleshooting: Heating Sequence of Operation (Continued)

HEATING SEQUENCE CONTINUED

NORMAL HEATING MODE ABNORMAL HEATING MODE

15-SECOND COMBUSTION AIR INDUCER PREPURGE

INITIATED BY CLOSED PRESSURE SWITCH.

YES

IGNITOR WARM-UP −− 20 SECONDS.

YES

4-SECOND TRIAL FOR IGNITION.

GAS VALVE OPENS. IGNITOR ENERGIZED FOR

FIRST 3 SECONDS OF THE TRIAL.

YES

FLAME STABILIZATION PERIOD.

4 SECONDS

FLAME RECTIFICATION CURRENT

CHECK. CAN FLAME BE PROVEN WITHIN

4 SECONDS AFTER GAS VALVE OPENS?

(0.5 microamps)

YES

FLAME PRESENT?

YES

FLAME SIGNAL 1.5 MICROAMPS OR GREATER?

YES

INDOOR BLOWER ON

AFTER 30−SECOND DELAY

YES

PRIMARY AND SECONDARY LIMIT

SWITCHES CLOSED?

YES

IS VOLTAGE ABOVE 90 VOLTS?

YES

GAS VALVE OFF. COMBUSTION AIR INDUCER ON.

HAS CONTROL FAILED TO SENSE FLAME FOR FIVE CONSECUTIVE TRIES DURING A SINGLE

WATCHGUARD MODE. GAS VALVE OFF.

LEDs SIGNAL WATCHGUARD FAILURE CODE.

IS 60-MINUTE RESET PERIOD COMPLETE?

(Does not affect operation of control)

LED #1 −− SLOW FLASH

COMBUSTION AIR INDUCER DE−ENERGIZED.

INDOOR BLOWER ON UNTIL SWITCH CLOSES.

LED #1 −− SLOW FLASH. LED #2 −− ON.

HAS PRIMARY / SECONDARY

EXCEEDED 3 MINUTES?

INDOOR BLOWER OFF.

HEAT DEMAND?

COMBUSTION AIR INDUCER OFF.

INDOOR BLOWER OFF WITH DELAY

HAS CONTROL RESET IGNITION

SEQUENCE FOUR TIMES?

LOW FLAME SIGNAL

LED #2 −− FAST FLASH

GAS VALVE DE−ENERGIZED.

IS LIMIT SWITCH CLOSED?

YES

LIMIT RESET TIME

LEDS SIGNAL

LIMIT SWITCH WATCHGUARD

MODE. GAS VALVE, COMB. AIR

INDUCER AND INDOOR BLOW-

ER OFF. LEDs SIGNAL LIMIT SWITCH OPEN UNTIL MAIN

YES

ALTERNATING

FAST FLASH UNTIL

VOLTAGE IS ABOVE

95 VOLTS, THEN

RESTARTS HEATING

SEQUENCE.

YES

POWER IS INTERRUPTED OR T’STAT IS CYCLED

OFF/ON FOR 1 SEC.

MINIMUM. 60−MINUTE

WATCHGUARD PE -

RIOD STARTS AT

TIME LIMIT CLOSES.

IS 60−MIN. PERIOD

COMPLETE?

ROLLOUT SWITCH CLOSED?

YES

COMBUSTION AIR PRESSURE

SWITCH CLOSED?

YES

THERMOSTAT DEMAND SATISFIED.

YES

LED #1 & #2 SIMULTANEOUS SLOW FLASHES.

YES

COMB. AIR INDUCER CONTINUES 5-SECOND

POST PURGE AFTER T’STAT DEMAND IS SATISFIED.

INDOOR AIR BLOWER COMPLETES SELECTED OFF"

DELAY BEFORE SHUTTING OFF.

SEQUENCE HOLDS UNTIL ROLLOUT SWITCH IS RESET

THERMOSTAT IS CYCLED OFF/ON FOR 1 SEC. MINIMUM.

HAS PRESSURE SWITCH OPENED 5

TIMES IN THE SAME HEAT DEMAND?

GAS VALVE DE−ENERGIZED.

COMBUSTION AIR INDUCER ON.

INDOOR BLOWER OFF WITH DELAY

LED #1 −− OFF. LED #2 −− SLOW FLASH.

HAS CAB SWITCH CLOSED IN 2.5 MINUTES?

5-MINUTE PRESSURE SWITCH

WATCHGUARD MODE.

GAS VALVE POWER OFF.

COMBUSTION AIR INDUCER POWER ON.

INDOOR BLOWER ON

LED #1 −− ON. LED #2 −− SLOW FLASH.

AND MAIN POWER IS INTERRUPTED OR

Page 41

YES

WATCHGUARD

1 HR

PRESSURE

SWITCH

MODE

Troubleshooting: Cooling Sequence of Operation

COOLING SEQUENCE OF OPERATION

NORMAL COOLING MODE ABNORMAL COOLING MODE

POWER ON

IGNITION CONTROL MAIN POWER ON.

CONTROL SELF DIAGNOSTIC CHECK.

IS CONTROL OPERATING NORMALLY?

YES

IS THERE A PROPER GROUND?

YES

IS POLARITY CORRECT?

YES

IS VOLTAGE

ABOVE 90 VOLTS?

YES

ROLLOUT SWITCH MONITORED CONTINUOUSLY.

IS ROLLOUT SWITCH CLOSED?

YES

GAS VALVE OFF. COMBUSTION AIR INDUCER OFF.

INDOOR BLOWER OFF WITH NORMAL DELAY.

SIGNAL CIRCUIT BOARD FAILURE AT LED.

INTERRUPT MAIN POWER TO RESET CONTROL.

SIGNAL IMPROPER GROUND AT LED.

CONTROL WILL CONTINUE TO CALL FOR COOLING

IN THIS CONDITION.

SIGNAL POLARITY REVERSED AT LED. CONTROL

WILL CONTINUE TO CALL FOR COOLING IN THIS

CONDITION.

LED SIGNALS LOW VOLTAGE. CONTROL WILL

CONTINUE TO CALL FOR COOLING

IN THIS CONDITION.

GAS VALVE OFF. COMBUSTION AIR INDUCER ON.

INDOOR BLOWER ON.

SIGNAL ROLL-OUT SWITCH OPEN AT LED.

SEQUENCE HOLDS UNTIL ROLLOUT SWITCH CLOSES

AND MAIN POWER IS INTERRUPTED OR THERMOSTAT

IS CYCLED OFF/ON FOR 1 SEC. MINIMUM.

LED: SLOW FLASH RATE REMAINS UNCHANGED

THROUGHOUT COOLING CYCLE.

THERMOSTAT CALLS FOR COOLING.

COMPRESSOR CONTACTOR AND SYSTEM FAN

ENERGIZED WITH 2-SECOND DELAY

(COOLING SPEED). EAC TERM. ENERGIZED.

THERMOSTAT OPENS.

COMPRESSOR OFF.

SYSTEM FAN AND EAC TERM. OFF

WITH 45-SECOND DELAY.

Page 42

Troubleshooting: Continuous Fan Sequence of Operation

CONTINUOUS HEAT SPEED FAN SEQUENCE OF OPERATION

LED: SLOW FLASH RATE REMAINS

UNCHANGED THROUGHOUT SEQUENCE.

MANUAL FAN SELECTION MADE AT THERMOSTAT.

CONTROL (G) ENERGIZES SYSTEM FAN AT HEAT

SPEED. EAC TERMINAL IS ENERGIZED.

THERMOSTAT CALLS FOR HEAT (W).

THERMOSTAT CALLS FOR COOLING.

YES

SYSTEM FAN SWITCHED TO COOL SPEED.

EAC TERM. REMAINS ON.

THERMOSTAT OPENS.

MANUAL FAN SELECTION MADE AT THERMOSTAT.

CONTROL (G) ENERGIZES SYSTEM FAN AT HEAT

SPEED. EAC TERM. ENERGIZED.

HUM TERM. ENERGIZES

WITH COMB. AIR INDUCER.

YES

SYSTEM FAN REMAINS ON

HEATING SPEED.

THERMOSTAT OPENS.

HUM TERM. DE−ENERGIZES

WITH COMB. AIR INDUCER

SYSTEM FAN REMAINS ON

HEATING SPEED.

Page 43

Lennox International Inc. AV-C, ML180UH User Manual

Specifications and Main Features

Frequently Asked Questions

User Manual