Lennox International Inc Merit Series Gas Furnace installation instructions Return Air Plenum

Page 10

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

Single Side Return Air

(with transition and filter)

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. (Re- quired to maintain proper air velocity.) See figure 9.

2 − Single side return air with optional return airbase. See fig- ure 10.

AIR FLOW

20” X 25” X 1”

(508mm X 635mm X 25mm)

Cleanable Filter

Return Air

Plenum

3 − Bottom return air.

4 − Return air from both sides.

5 − Bottom and one side return air.

Refer to Engineering Handbook for additional information.

Transition

FIGURE 9

Optional Return Air Base

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

 

FURNACE

 

FRONT

 

INDOOR AIR

 

QUALITY

 

CABINET

AIR FLOW

(PCO, Filter

 

Cabinet, etc.)

IF BASE

3−1/4

 

 

 

IS USED

 

 

 

WITHOUT

(83)

 

 

 

IAQ CABINET,

 

 

 

 

 

 

A SINGLE

 

 

 

 

 

 

RETURN AIR

 

 

 

 

 

 

PLENUM

 

 

 

 

 

 

MUST

 

 

 

 

 

 

COVER BOTH

 

 

 

 

 

 

 

 

 

 

 

 

UNIT AND

 

 

 

 

 

 

 

 

 

 

 

 

RETURN

 

 

 

 

 

 

7−1/4

AIR BASE

OPENINGS

(184)

 

 

 

 

 

1 23 (584)

 

 

 

 

Overall

1 Minimum

 

 

(Maximum)

 

 

 

 

11 (279)

 

1 Unit side return air

2 Maximum

1 22−7/16

14 (356)

(570)

 

Opening

 

Overall

 

 

 

 

(Maximum)

5−5/8

SIDE RETURN

 

AIR OPENINGS

 

(143)

 

 

 

 

(Either Side)

 

 

OPTIONAL

 

14−1/2 (368) A Width (65W75)

RETURN

17−1/2 (446) B Width (50W98)

AIR BASE

21 (533) C Width (50W99)

 

24−1/2 (622) D Width (51W00)

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

23

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

(584)

 

 

 

3/4

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

26−7/8

(19)

 

 

 

 

(683)

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

SIDE VIEW

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

1Both the unit return air opening and the base return air opening must be covered by a single plenum or IAQ cabinet.

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.

2To minimize pressure drop, the largest opening height possible (up to 14 inches 356 mm) is preferred.

FIGURE 10

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Contents Installation Instructions ML180UH Table of ContentsUnit Dimensions − inches mm TOP ViewParts Arrangement ML180UH Gas Furnace Safety InformationShipping and Packing List Use of Furnace as Construction Heater GeneralCombustion, Dilution & Ventilation Air Equipment in Confined Space ALL AIR from Inside Equipment in Confined Space Setting Equipment Return Air Plenum Right Horizontal Application Installation Clearances Top LeftEnd Bottom Filters Duct SystemTop Vent Discharge VentingUpflow Position Left Side Vent DischargeHorizontal Right Position Horizontal Left PositionSide Vent Discharge Vent Connection Upflow and Horizontal Position Common Venting Using Metal−Lined Masonry Chimney −1/2 Cated or common venting system, you must inspect 18 − The common vent diameter must always be at least asFeet FAN + FAN FAN + NAT 112 175 169 278 Carbon Monoxide Poisoning Hazard Gas Piping Ers or straps. Install a drip leg in vertical pipe runs to− In some localities, codes may require the installation Every 8 to 10 feet 2.44 to 3.01 m with suitable hangLeft−Side Air Discharge Horizontal ApplicationRight−Side Air Discharge Electrical Interior MAKE−UP BOX InstallationElectrostatic Discharge ESD Thermostat Designations ML180UH Schematic Wiring Diagram and Sequence of Operation Typical ML180UH Field Wiring Diagram Integrated ControlFor Your Safety Read Before Lighting Unit Start−UpProper Combustion Gas Pressure AdjustmentHigh Altitude Other Unit Adjustments Manifold Pressure Settings at all AltitudesHeat FAN-OFF Time in Seconds No Jumper680 453 900750 885860 Single Side Return Air − Air volumes in bold require field1391 653Service Electrical SHOCK, Fire Or Explosion Hazard−090, −110 −135 units ML180UH BURNER, Combustion AIR Inducer AssemblyHeat Exchanger Removal −045 and −070 unitsPage Planned Service Repair Parts ListIntegrated Control Diagnostic Codes DescriptionTroubleshooting Heating Sequence of Operation Normal Heating Mode Abnormal Heating ModeHeating Sequence Troubleshooting Cooling Sequence of Operation Normal Cooling Mode Abnormal Cooling ModeTroubleshooting Continuous Fan Sequence of Operation Continuous Heat Speed FAN Sequence of Operation

Merit Series Gas Furnace specifications

Lennox International Inc. is a leading name in the heating and cooling industry, and their Merit Series Gas Furnace embodies the commitment to quality and efficiency that the company is known for. The Merit Series is designed to provide reliable heating in a sustainable manner, making it an excellent choice for homeowners seeking comfort without excessive energy bills.

One of the standout features of the Merit Series Gas Furnace is its efficiency ratings. The units in this series typically boast Annual Fuel Utilization Efficiency (AFUE) ratings of up to 95%. This level of efficiency means that the furnace converts a significant portion of the fuel it uses into heat, ultimately lowering operating costs. Such energy-efficient performance is not only beneficial for the wallet but also promotes environmental sustainability.

The Merit Series also incorporates advanced technologies that enhance its operation. The inclusion of a multi-speed blower motor is a notable feature that provides thoughtful airflow management throughout the home. By adjusting the speed according to the heating needs, the furnace optimizes comfort levels while minimizing noise and energy consumption. Homeowners can enjoy a warm environment without the disruptive sounds often associated with traditional furnaces.

Moreover, the Merit Series comes equipped with durable construction materials designed to withstand the test of time. From the robust heat exchanger to the heavy-gauge cabinet, Lennox focuses on longevity and reliability. This ensures that homeowners can trust their furnace to operate effectively even in the harshest winter conditions.

Safety features are also integral to the design of the Merit Series Gas Furnace. With an integrated Flame Sensor and a built-in safety shut-off system, the furnace ensures that any irregularities in operation are promptly detected and addressed. Such measures provide peace of mind for families using the heating system throughout the cold months.

Installation and maintenance are further simplified with the Merit Series. Its design facilitates easier access for HVAC professionals, allowing for quicker installations and routine service, ensuring that homeowners spend less time and money on upkeep.

In conclusion, Lennox International Inc.'s Merit Series Gas Furnace combines efficiency, advanced technology, and robust construction, making it a top choice for families looking to enhance their home's heating system. With its energy-saving innovations and commitment to reliability, the Merit Series stands as an exemplary option in today’s market.
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