Lennox International Inc Merit Series Gas Furnace Electrical, Electrostatic Discharge ESD

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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.

CAUTION

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

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

ISOLATE

SHUT−OFF VALVE

GAS VALVE

WILL NOT HOLD

FURNACE

NORMAL TEST

 

PRESSURE

 

1/8 NPT PLUG

 

CAP

FIGURE 28

Electrical

ELECTROSTATIC DISCHARGE (ESD)

Precautions and Procedures

CAUTION

Electrostatic discharge can affect electronic com- ponents. Take precautions during furnace installa- tion and service to protect the furnace’s electronic controls. Precautions will help to avoid control ex- posure to electrostatic discharge by putting the fur- nace, the control and the technician at the same electrostatic potential. Neutralize electrostatic charge by touching hand and all tools on an un- painted unit surface, such as the gas valve or blower deck, before performing any service procedure.

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

Right Side

BOX

FIGURE 29

INTERIOR MAKE−UP BOX INSTALLATION

Left side

BOX

FIGURE 30

Refer to figure 32 for schematic wiring diagram and trou- bleshooting 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.

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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 FiltersUpflow Position VentingTop Vent Discharge 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 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 − In some localities, codes may require the installation Ers or straps. Install a drip leg in vertical pipe runs toGas Piping 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 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 Seconds750 453 900680 8851391 Single Side Return Air − Air volumes in bold require field860 653Electrical SHOCK, Fire Or Explosion Hazard ServiceHeat Exchanger Removal ML180UH BURNER, Combustion AIR Inducer Assembly−090, −110 −135 units −045 and −070 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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