Lennox International Inc SL280DFV installation instructions Duct System, Venting

Duct System

Use industry-approved standards (such as those pub- lished by Air Conditioning Contractors of America or Ameri- can Society of Heating, Refrigerating and Air Conditioning Engineers) to size and install the supply and return air duct system. This will result in a quiet and low-static system that has uniform air distribution.

NOTE − Do not operate the furnace in the heating mode with an external static pressure that exceeds 0.8 inches w.c. Higher external static pressures may cause erratic lim- it operation.

Ensure that you have made a seal between the supply air plenum and the furnace and between the furnace and the return air plenum.

Return Air Plenum

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 device (i.e., wood fireplace) is installed. When return air is drawn from a room, a negative pressure is created in the room. If a gas appliance is operating in a room with negative pres- sure, 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 combustion and the formation of carbon monoxide gas. This toxic gas might then be dis- tributed throughout the house by the furnace duct sys- tem.

Venting

A 4−inch diameter flue transition is factory-installed on all models. Modifying or removing the flue transition will cause the unit to operate unsafely and will void the unit certification. The vent connector does not require insula- tion.

The SL280DFV series units are classified as fan−assisted Category I furnaces when vertically vented according to the latest edition of National Fuel Gas Code (NFPA 54 / ANSI Z223.1). A fan−assisted Category I furnace is an ap- pliance equipped with an integral mechanical means to ei- ther draw or force combustion products through the com- bustion chamber and/or heat exchanger.

NOTE − Use these instructions as a guide. They do not su- persede local codes. This furnace must be vented accord- ing to all local codes, these installation instructions, and the provided venting tables in these instructions

The venting tables in this manual were extracted from the National Fuel Gas Code (NFPA 54 / ANSI Z223.1) and are provided as a guide for proper vent installation. Proper ap- plication, termination, construction and location of vents must conform to local codes having jurisdiction. In the ab- sence of local codes, the NFGC serves as the defining doc- ument.

Refer to the tables and the venting information contained in these instructions to properly size and install the venting system.

IMPORTANT

Once the venting system is installed, attach the connected Vent" warning sticker to a visible area of the plenum near the vent pipe. The warning sticker is provided in the bag assembly. Order kit 66W04 for additional stickers.

WARNING

Asphyxiation hazard. The exhaust vent for this fur- nace must be securely connected to the furnace flue transition at all times.

VENT CONNECTION	“DISCONNECTED VENT”
	WARNING
	STICKER
FLUE TRANSITION
COLLAR

FIGURE 14

Use self−drilling sheet metal screws or a mechanical fas- tener to firmly secure the vent pipe to the round collar of the flue transition. If self−drilling screws are used to attach the vent pipe, it is recommended that three be used. Drive one self−drilling screw through the front and one through each side of the vent pipe and collar. See figure 14.

Masonry chimneys used to vent Category I central fur- naces must be either tile-lined or lined with a listed metal lining system or dedicated gas vent. Unlined masonry chimneys are prohibited. See figures 15 and 16 for com- mon venting.

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