Lennox International Inc Merit Series Gas Furnace installation instructions Other Unit Adjustments

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TABLE 12

Manifold Pressure Settings at all Altitudes

Model

Gas

0−2000 ft

2105−4500 ft.

4501−7500 ft

7501 − 10,000 ft

Line Pressure in.wg.

 

 

Input Size

Min

Max

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

045

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

 

 

 

 

 

 

 

 

 

070

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

 

 

 

 

 

 

 

 

 

090

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

 

 

 

 

 

 

 

 

 

110

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

 

 

 

 

 

 

 

 

 

135

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

 

 

 

 

 

 

 

 

 

TABLE 13

Pressure Switch and Gas Conversion Kits at all Altitudes

Model

Input Size

 

 

 

High Altitude

Natural Gas to LP/Propane

LP/Propane to

High Altitude Pressure Switch Kit

Natural Gas Burner

Natural Gas Burner

Burner Orifice Kit

 

 

 

Orifice Kit

Orifice 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

 

 

 

 

 

 

 

045

 

80W52

80W51

 

 

 

 

 

 

 

 

 

 

 

 

070

 

80W52

80W51

 

 

 

 

 

 

 

 

 

 

 

 

090

No Change

80W52

80W51

73W37

70W89

76W15

73W81

 

 

 

 

 

 

 

 

110

 

80W57

80W52

 

 

 

 

 

 

 

 

 

 

 

 

135

 

80W52

80W51

 

 

 

 

 

 

 

 

 

 

 

 

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

Primary and Secondary Limits

The primary limit is located on the heating compartment vestibule panel. The secondary limits (if equipped) are lo- cated in the blower compartment, attached to the back side of the blower. These auto reset limits are factory−set and re- quire 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 allow- ing ignition trial. The switch is factory−set and requires no adjustment.

Temperature Rise

After the furnace has been started, and supply and return

air temperatures have been allowed to stabilize, check the temperature rise. If necessary, adjust the blower speed to 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 in- tegrated control. The unit is shipped with a factory fan−off delay setting of 90 seconds. The fan−off delay affects com- fort and is adjustable to satisfy individual applications. Ad- just 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 re- turn air temperatures; shorter settings provide higher re- turn air temperatures. See figure 36.

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Contents Table of Contents Installation Instructions ML180UHTOP View Unit Dimensions − inches mmParts Arrangement ML180UH Gas Furnace Safety InformationShipping and Packing List General Use of Furnace as Construction HeaterCombustion, 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 Duct System FiltersLeft Side Vent Discharge VentingUpflow Position Top Vent DischargeHorizontal Right Position Horizontal Left PositionSide Vent Discharge Vent Connection Upflow and Horizontal Position Common Venting Using Metal−Lined Masonry Chimney −1/2 18 − The common vent diameter must always be at least as Cated or common venting system, you must inspectFeet FAN + FAN FAN + NAT 112 175 169 278 Carbon Monoxide Poisoning Hazard Every 8 to 10 feet 2.44 to 3.01 m with suitable hang Ers or straps. Install a drip leg in vertical pipe runs to− In some localities, codes may require the installation Gas PipingLeft−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 Integrated Control Typical ML180UH Field Wiring DiagramUnit Start−Up For Your Safety Read Before LightingProper Combustion Gas Pressure AdjustmentHigh Altitude Manifold Pressure Settings at all Altitudes Other Unit AdjustmentsNo Jumper Heat FAN-OFF Time in Seconds885 453 900750 680653 Single Side Return Air − Air volumes in bold require field1391 860Electrical SHOCK, Fire Or Explosion Hazard Service−045 and −070 units ML180UH BURNER, Combustion AIR Inducer AssemblyHeat Exchanger Removal −090, −110 −135 unitsPage Repair Parts List Planned ServiceDescription Integrated Control Diagnostic CodesNormal Heating Mode Abnormal Heating Mode Troubleshooting Heating Sequence of OperationHeating Sequence Normal Cooling Mode Abnormal Cooling Mode Troubleshooting Cooling Sequence of OperationContinuous Heat Speed FAN Sequence of Operation Troubleshooting Continuous 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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