Lennox International Inc EL180UHE Venting, Return Air Plenum, Mounting Screws Location

Return Air Plenum

NOTE - Return air must not be drawn from a room­ where this furnace, or any other gas-fueled appliance (i.e., water heater), or carbon monoxide producing de­ vice (i.e., wood fireplace) is installed.

When return air is drawn from a room, a negative pres­ sure is created in the room. If a gas appliance is operating in a room with negative pressure, the flue products can be pulled back down the vent pipe and into the room. This reverse flow of the flue gas may result in incomplete com­ bustion and the formation of carbon monoxide gas. This toxic gas might then be distributed throughout the house by the furnace duct system.

In upflow applications, the return air can be brought in through the bottom or either side of the furnace. If a fur­ nace with bottom return air is installed on a platform, make an airtight seal between the bottom of the furnace and the platform to ensure that the unit operates properly and safely. Use fiberglass sealing strips, caulking, or equiva­ lent sealing method between the plenum and the furnace cabinet to ensure a tight seal. If a filter is installed, size the return air duct to fit the filter frame.

Venting

A 4-inch diameter flue transition is factory‐installed on the combustion air inducer outlet of all models. Figure 15 shows the combustion air inducer as shipped from the factory.

	Mounting Screws Location
Flue Transition	Mounting Screws

FIGURE 14

UPFLOW POSITION
Top Vent Discharge
Flue	Vent Pipe
Transition	Collector Box
Pressure
Switch
Make-Up
Box
AIR	FLOW

FIGURE 15

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 20.

1 - Remove the four mounting screws (figure 14) 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.

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