Lennox International Inc Lennox Merit Series Gas Furnace Upflow/Horizontal Air Discharge, ML193UH

Intake Piping

The ML193UH furnace may be installed in either direct vent or non-direct vent applications. In non-direct vent applications, when intake air will be drawn into the furnace from the surrounding space, the indoor air quality must be considered and guidelines listed in Combustion, Dilution and Ventilation Air section must be followed.

Follow the next two steps when installing the unit in Direct Vent applications, where combustion air is taken from outdoors and flue gases are discharged outdoors. The

provided air intake screen must not be used in direct vent applications (outdoors).

1 - Use transition solvent cement or a sheet metal screw to secure the intake pipe to the inlet air connector.

2 - Route piping to outside of structure. Continue with installation following instructions given in general guide lines for piping terminations and intake and ex­ haust piping terminations for direct vent sections. Re­ fer to table 5 for pipe sizes.

TYPICAL AIR INTAKE PIPE CONNECTIONS

UPFLOW NON−DIRECT

VENT APPLICATIONS

INTAKE DEBRIS SCREEN (Provided)

NOTE - Debris screen and elbow may be rotated, so that screen may be positioned to face forward or to either side.

FIGURE 28

TYPICAL AIR INTAKE PIPE CONNECTIONS

HORIZONTAL NON−DIRECT VENT APPLICATIONS (Horizontal Right−Hand Air Discharge Application Shown)

PVC pipe

coupling

OR

INTAKE DEBRIS SCREEN (Provided)

NOTE - Debris screen may be positioned straight out (preferred) or with an elbow rotated to face down.

FIGURE 29

Follow the next two steps when installing the unit in Non‐ Direct Vent applications where combustion air is taken from indoors and flue gases are discharged outdoors.

1 - Use field-provided materials and the factory-provided air intake screen to route the intake piping as shown in figure 28 or 29. Maintain a minimum clearance of 3” (76mm) around the air intake opening. The air intake opening (with the protective screen) should always be directed forward or to either side in the upflow position, and either straight out or downward in the horizontal position.

The air intake piping must not terminate too close to the flooring or a platform. Ensure that the intake air inlet will not be obstructed by loose insulation or other items that may clog the debris screen.

2 - If intake air is drawn from a ventilated attic (figure 30) or ventilated crawlspace (figure 31) the exhaust vent length must not exceed those listed in table 7. If 3” di­ ameter pipe is used, reduce to 2” diameter pipe at the termination point to accommodate the debris screen.Use a sheet metal screw to secure the intake pipe to the connector, if desired.

3 - Use a sheet metal screw to secure the intake pipe to the connector, if desired.

Page 21