Lennox International Inc Merit Series Gas Furnace Venting, Upflow Position, Top Vent Discharge

Venting

A 4−inch diameter flue transition is factory-installed on the combustion air inducer outlet of all models. Figure 16 shows the combustion air inducer as shipped from the factory.

	Mounting Screws Location
Flue Transition	Mounting Screws

FIGURE 15

	Upflow Position
	UPFLOW POSITION
	Top Vent Discharge
	Vent Pipe
	Flue
	Transition
Pressure	Collector Box
Switch
Make−Up
Box

AIR FLOW

FIGURE 16

IMPORTANT

The unit will not vent properly with the flue transition pointed down in the 6 o’clock position.

The combustion air inducer may be rotated clock- wise or counterclockwise by 90° to allow for top or side vent discharge in all applications. When the unit is installed, the flue transition must be in the 9 o’clock, 12 o’clock or 3 o’clock position.

If necessary, reposition the combustion air inducer, pres- sure switch and/or make−up box as needed per the follow- ing steps. See figures 16 through 22.

1 − Remove the four mounting screws (figure 15) which secure the combustion air inducer / pressure switch assembly to the orifice plate. Lift the assembly and ro- tate it 90 degrees clockwise or counterclockwise to ei- ther the 3 o’clock position or to 9 o’clock position. Re− secure with four screws. Gasket should be left in place.

2 − Use tin snips to cut preferred opening on the cabinet for repositioning the flue outlet. Use the cut−out piece as a cover plate to patch unused opening on cabinet.

UPFLOW POSITION

Left Side Vent Discharge

Pressure	Collector Box Make−Up
Switch
	Box

Vent Pipe

Flue

Transition

AIR FLOW

DGas supply piping must be brought into the unit from the right side in order to accommodate the flue pipe.

DCut combustion air inducer tubing from 9" to 8" to avoid interference with inducer motor

DRemove make−up box assembly (2 screws) and cut wire tie to free make−up box wires. Re−install make−up box on other side of cabinet.

DRe−secure make−up box wires: Either pull excess wires through the blower compartment and secure using supplied wire tie, or coil excess wire and secure to the gas manifold.

FIGURE 17

UPFLOW POSITION

Right Side Vent Discharge

Collector Box	Cover Plate	Flue Transition
		Vent Pipe

Pressure

Switch

Make−Up

Box

AIR FLOW

DCut combustion air inducer tubing from 9" to 5" to avoid interference with inducer motor

FIGURE 18

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