Lennox International Inc Merit Series Gas Furnace Thermostat Designations

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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 suit- able 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 Na- tional Electric Code (ANSI/NFPA No. 70). A green ground wire is provided in the field make−up box.

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

Accessory Terminals

One line voltage ade 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

SThe furnace requires 120 volts + 10% (Range: 108 volts to 132 volts).

SThe furnace operates at 60 Hz + 5% (Range: 57 Hz to 63 Hz).

SThe 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.

SGenerator 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 appropri- ate dual fuel thermostat instructions.

ML180UH and CONDENSING UNIT

THERMOSTAT DESIGNATIONS

(Refer to specific thermostat and outdoor unit.)

Thermostat

Furnace

Condensing

 

 

Unit

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 exter- nal relay.

One line voltage ade terminal is provided on

the furnace integrated control. See figure 34 for integrated control configuration. This terminal is energized in the

R

W1

Y

G

C

POWER

HEAT

COOLING

INDOOR BLOWER

COMMON

R

W

Y

G

C

*CONDENSING

UNIT

CONDENSING

UNIT

CONDENSING UNIT COMMON

heating mode when the combustion air inducer is operat- ing. Any humidifier rated up to one amp can be connected to this terminal with the neutral leg of the circuit being con- nected to one of the provided neutral terminals. If a humidi- fier rated at greater than one amp is connected to this termi- nal, 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:

*NOTE −

FIGURE 31

Indoor Blower Speeds

1 − When the thermostat is set to AN 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.

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Contents Installation Instructions ML180UH Table of ContentsUnit Dimensions − inches mm TOP ViewParts Arrangement Shipping and Packing List Safety InformationML180UH Gas Furnace 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 End Bottom Horizontal Application Installation Clearances Top LeftRight Filters Duct SystemTop Vent Discharge VentingUpflow Position Left Side Vent DischargeSide Vent Discharge Horizontal Left PositionHorizontal Right Position 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 hangRight−Side Air Discharge Horizontal ApplicationLeft−Side Air Discharge Electrostatic Discharge ESD Interior MAKE−UP BOX InstallationElectrical Thermostat Designations ML180UH Schematic Wiring Diagram and Sequence of Operation Typical ML180UH Field Wiring Diagram Integrated ControlFor Your Safety Read Before Lighting Unit Start−UpHigh Altitude Gas Pressure AdjustmentProper Combustion 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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