Lennox DAVE SIGNATURE SL280DFV Installation Instructions Manual page 14

A fan-assisted furnace may be commonly vented into an
existing lined masonry chimney if the following conditions
are met:
• The chimney is currently serving at least one draft-
hood equipped appliance
• The vent connectors and chimney are sized accord-
ing to the provided venting tables.
If type B1 double-wall vent is used inside a chimney, no
other appliance can be vented into the chimney. The outer
wall of type B1 vent pipe must not be exposed to flue prod-
ucts. A type B1 vent or masonry chimney liner shall termi-
nate above the roof surface with a listed cap or a listed
roof assembly 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 SL280DFV 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 consid-
ered to be exposed to the outdoors.
General Venting Requirements
Vent all SL280DFV furnaces according to these instruc-
tions:
1 - Vent diameter recommendations and maximum
allowable 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
determine 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
appliance categorized vent area, drafthood outlet
area or flue collar area unless designed according
to approved engineering methods.
5 - Appliance vents - The flow area of the largest
sction 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 designed according to approved engineering
methods.
6 - The entire length of single wall metal vent connector
shall be readily accessible for inspection, cleaning,
and replacement.
7 - Single appliance venting configurations with zero
lateral lengths (TABLE 5) are assumed to have
no elbows in the vent system. For all other vent
configurations, the vent system is assumed to have
two 90° elbows. For each additional 90° elbow or
equivalent (for example two 45° elbows equal one
90° elbow) beyond two, the maximum capacity
listed in the venting table should be reduced by
10% (0.90 x maximum listed capacity).
8 - The common venting tables (TABLE 6 and TABLE
7) were generated using a maximum horizontal vent
connector length of 1-1/2 feet (.46 m) for each inch
(25 mm) of connector diameter as follows:
Connector
Diameter inches
3
4
5
6
7
9 - If the common vertical vent is offset, the maximum
common vent capacity listed in the common venting
tables should be reduced by 20%, the equivalent
of two 90° elbows (0.80 x maximum common vent
capacity). The horizontal length of the offset shall
not exceed 1-1/2 feet (.46 m) for each inch (25 mm)
of common vent diameter.
10 - The vent pipe should be as short as possible with
the least number of elbows and angles required to
complete the job. Route the vent connector to the
vent using the shortest possible route.
11 - A vent connector shall be supported without any
dips or sags and shall slope a minimum of 1/4 inch
(6.4 mm) per linear foot (305 mm) of connector,
back toward the appliance.
12 - Vent connectors shall be firmly attached to the
furnace flue collar by self-drilling screws or other
approved means, except vent connectors of listed
type B vent material which shall be assembled
according to the manufacturer's instructions. Joints
between sections of single wall connector piping
shall be fastened by screws or other approved
means.
13 - When the vent connector used for Category I
ppliances must be located in or pass through a
crawlspace or other areas which may be cold, that
portion of the vent connector shall be constructed
of listed double-wall type B vent material or material
having equivalent insulation qualities.
Page 14
TABLE 4
Maximum Horizontal
Connector Length feet
4-1/2
6
7-1/2
9
10-1/2