Lennox International Inc MERIT SERIES GAS FURNACE DOWNFLOW AIR DISCHARGE, ML193DF

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19 − Reinstall heat exchanger into cabinet making sure that the clamshells of the heat exchanger assembly are resting on the support located at the rear of the cabi- net. Remove the indoor blower to view this area through the blower opening.

20 − Re-secure the supporting screws along the vestibule sides and bottom to the cabinet. Reinstall blower and mounting screws.

21 − Reinstall cabinet screws on front flange at blower deck.

22 − Reinstall the primary limit on the vestibule panel.

23 − Route heating component wiring through hole in blow- er deck and reinsert strain relief bushing.

24 − Reinstall electrical junction box.

25 − Reinstall the combustion air inducer. Reconnect the combustion air inducer to the wire harness.

26 − Reinstall pressure switches and reconnect pressure switch wiring.

27 − Carefully connect combustion air pressure switch hosing from pressure switches to proper stubs on cold end header collector box.

28 − Reinstall condensate trap.

29 − Reconnect exhaust piping and exhaust drain tubing.

30 − Reinstall burner box assembly in vestibule area.

31 − Reconnect flame roll−out switch wires.

32 − Reconnect sensor wire and reconnect 2−pin plug from ignitor.

33 − Secure burner box assembly to vestibule panel using four existing screws. Make sure burners line up in center of burner ports.

34 − Reinstall gas valve manifold assembly. Reconnect gas supply line to gas valve.

35 − Reconnect 2 wires to gas valve.

36 − Replace the blower compartment access panel.

37 − Refer to instruction on verifying gas and electrical con- nections when re−establishing supplies.

38 − Follow lighting instructions to light and operate fur- nace for 5 minutes to ensure that heat exchanger is clean and dry and that furnace is operating properly.

39 − Replace heating compartment access panel.

Cleaning the Burner Assembly

1 − Turn off electrical and gas power supplies to furnace. Remove upper and lower furnace access panels.

2 − Disconnect the 2−pin plug from the gas valve.

3 − Remove the burner box cover.

4 − Disconnect the gas supply line from the gas valve. Re- move gas valve/manifold assembly.

5 − Mark and disconnect sensor wire from the sensor. Dis- connect 2-pin plug from the ignitor at the burner box.

6− Remove four screws which secure burner box assem- bly to vest panel. Remove burner box from the unit.

7 − Use the soft brush attachment on a vacuum cleaner to gently clean the face of the burners. Visually inspect the inside of the burners and crossovers for any block- age caused by foreign matter. Remove any blockage.

8− Reconnect the sensor wire and reconnect the 2−pin plug to the ignitor wiring harness.

9 − Reinstall the burner box assembly using the existing four screws. Make sure that the burners line up in the center of the burner ports.

10 − Reinstall the gas valve manifold assembly. Reconnect the gas supply line to the gas valve. Reinstall the burn- er box cover.

11 − Reconnect 2−pin plug to gas valve.

12 − Replace the blower compartment access panel.

13 − Refer to instruction on verifying gas and electrical con- nections when re−establishing supplies.

14 − Follow lighting instructions to light and operate fur- nace for 5 minutes to ensure that heat exchanger is clean and dry and that furnace is operating properly.

15 − Replace heating compartment access panel.

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Contents Table of Contents Installation Instructions ML193DFML193DF ML193DF Unit Dimensions − inches mmBlower Motor BAG AssemblyML193DF Parts Arrangement Control BOXShipping and Packing List Safety InformationDirect Vent Installation NON−DIRECT Vent ML193DF Gas FurnaceUse of Furnace as Construction Heater Combustion, Dilution & Ventilation Air GeneralEquipment in Confined Space − ALL AIR from Inside Equipment in Confined Space − ALL AIR from Outside Shipping Bolt RemovalSetting Equipment Installation − Setting EquipmentFront Horizontal Back NC‡ NON−COMBUSTIBLE Floor Opening SizeSide View Combustible Flooring Base Opening Size− Seal the cabinet and check for air leaks Duct System Pipe & Fittings SpecificationsPiping and Fittings Specifications FiltersOutdoor Termination Kits Usage Schedule Joint Cementing ProcedureVenting Practices Piping Suspension GuidelinesMinimum Vent Pipe Lengths Vent Piping GuidelinesML193DF MIN. Vent Length Model Maximum Allowable Intake or Exhaust Vent Length in Feet Typical Intake Pipe Connections Typical Exhaust Pipe ConnectionsIntake Exhaust Typical AIR Intake Pipe Connections Inches 305mm or 12 in mm Inside Corner DetailUS Installations1 Canadian Installations2 Direct Vent Roof Termination KIT − On field supplied terminations, a minimum distanceFLUSH−MOUNT Side Wall Termination KIT 51W11 51mm 76mm Vent Pipe Support Reducer MAY beRequired to Adapt Unconditioned SpaceTop View Front ViewExhaust NON−DIRECT Vent Roof Termination KIT 203mm − 305mmML193DF NON−DIRECT Vent Application Using Existing Chimney To drain ML193DF with Evaporator CoilTrap / Drain Assembly Using 1/2 PVC or 3/4 PVC Furnace Isolate GAS Valve Gas PipingGAS Pipe Capacity − FT3/HR kL/HR Electrical Precautions and ProceduresElectrostatic Discharge ESD BOX Inside FACTORY− Installed Left Side MAKE−UPInterior MAKE−UP BOX Exterior MAKE−UP BOXThermostat Designations Typical ML193DF Field Wiring DiagramTypical ML193DF Wiring Diagram Automatic Hot Surface Ignition System For Your Safety Read Before OperatingUnit Start−Up Integrated ControlPage High Altitude Information Gas Pressure AdjustmentGAS Meter Clocking Chart Proper Combustion2286m 3048m 2286 − 3038m73W37 73W81 68W68 74W90 74W91 69W73 Heat FAN-OFF Time in Seconds Other Unit AdjustmentsNo Jumper High Low In. w.g Cfm Watts Cfm Watts cfm Watts Blower DataElectrical SHOCK, Fire Or Explosion Hazard ServicePage LED #1 Red LED #2 Green Planned ServiceIgnition Control Board Diagnostic Codes Diagnostic CodesNormal Heating Mode Abnormal Heating Mode Troubleshooting Heating Sequence of OperationHeating Sequence of Operation Heating Sequence Normal Cooling Mode Abnormal Cooling Mode Troubleshooting Cooling Sequence of OperationCooling Sequence of Operation Continuous Heat Speed FAN Sequence of Operation Troubleshooting Continuous Fan Sequence of OperationRepair Parts List Intake / Exhaust Pipe Start−Up & Performance Check ListGAS Supply Return AIR Duct System Supply AIR DuctVent Pipe Temperature RiseTotal External Static Drain Line Condensate Line ThermostatLY BELOW. Keep Clear of ALL OBSTRUC- Tions Requirements for Commonwealth of Massachusetts