Lennox International Inc Merit Series Gas Furnace installation instructions

Common Venting Using Metal−Lined Masonry Chimney

		SEALED
	MAX. LENGTH
	−− SEE NOTE 1
5 ft. (1.5 m)	BELOW.
	MIN. LENGTH −− AS
minimum		EXTERIOR
	SHORT AS PRACTICAL
		CHIMNEY WITH
		METAL
		LINER
VENT CONNECTOR
4 in. (102 mm)
minimum
	FURNACE
OTHER
APPLIANCE
		PERMANENTLY
		SEALED FIREPLACE
		OPENING

NOTE 1 − Refer to the provided venting tables for installations. Refer to the capacity requirements shown in the provided venting tables.

FIGURE 24

DO NOT insulate the space between the liner and the chimney wall with puffed mica or any other loose gran- ular insulating material.

IMPORTANT

SINGLE appliance venting of a fan-assisted furnace into a tile-lined masonry chimney (interior or outside wall) is PROHIBITED. The chimney must first be lined with either type B1 vent or an insulated single wall flexible vent lining system which has been sized ac- cording to the provided venting tables and the vent pipe manufacturer’s instructions.

A fan−assisted furnace may be commonly vented into an existing lined masonry chimney if the following conditions are met:

SThe chimney is currently serving at least one drafthood− equipped appliance;

SThe vent connectors and chimney are sized according to the provided venting tables.

If type B1 double-wall vent is used inside a chimney, no oth- er appliance can be vented into the chimney. The outer wall of type B1 vent pipe must not be exposed to flue products. A type B1 vent or masonry chimney liner shall terminate above the roof surface with a listed cap or a listed roof as- sembly according to the terms of their respective listings and the vent manufacturer’s instructions.

When inspection reveals that an existing chimney is not safe for the intended purpose, it shall be rebuilt to conform to nationally recognized standards, lined or relined with suitable materials, or replaced with a gas vent or chimney suitable for venting ML180UH series units. The chimney passageway must be checked periodically to ensure that it is clear and free of obstructions.

Do not install a manual damper, barometric draft regulator, or flue restrictor between the furnace and the chimney. Never connect a Category I appliance to a chimney that is servicing a solid−fuel appliance. If a fireplace chimney flue is used to vent this appliance, the fireplace opening must be permanently sealed.

A type B or listed chimney lining system that passes through an unused masonry chimney flue is not considered to be exposed to the outdoors.

General Venting Requirements

Vent all ML180UH furnaces according to these instruc- tions:

1 − Vent diameter recommendations and maximum allow- able piping runs are found in the provided venting tables.

2 − In no case should the vent or vent connector diameter be less than the diameter specified in the provided venting tables.

3 − The minimum vent capacity determined by the sizing tables must be less than the low fire input rating and the maximum vent capacity must be greater than the high fire input rating.

4 − Single appliance vents − If the vertical vent or tile-lined chimney has a larger diameter or flow area than the vent connector, use the vertical vent diameter to de- termine the minimum vent capacity and the vent connector diameter to determine the maximum vent capacity. The flow area of the vertical vent, however, shall not exceed 7 times the flow area of the listed ap- pliance categorized vent area, drafthood outlet area or flue collar area unless designed according to approved engineering methods.

5 − Multiple appliance vents − The flow area of the largest section of vertical vent or chimney shall not exceed 7 times the smallest listed appliance categorized vent area, drafthood outlet area or flue collar area unless de- signed according to approved engineering methods.

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