ML180UH Schematic Wiring Diagram and Sequence of Operation

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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.

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Lennox International Inc Merit Series Gas Furnace ML180UH Schematic Wiring Diagram and Sequence of Operation
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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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