Lennox MERIT Series Installation Instructions Manual page 17

Common Venting Using Tile-Lined Interior Masonry Chimney and Combined Vent Connector
NOTE- Refer to provided venting tables
for installations.
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 (tables 3 and 4 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 (4 and 5) 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:
TABLE 2
Connector Diameter
inches (mm)
3 (76)
4 (102)
5 (127)
6 (152)
7 (178)
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.
MINIMUM LENGTH = AS SHORT AS PRACTICAL.
FOR MAXIMUM LENGTH SEE NOTE TO LEFT
OTHER
APPLIANCE
AIR FLOW
Figure 25
Maximum Horizontal
Connector Length feet (m)
4-1/2 (1.37)
6 (1.83)
7-1/2 (2.29)
9 (2.74)
10-1/2 (3.20)
VENT
CONNECTOR
FURNACE
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
appliances must be located in or pass through
a crawlspace, attic 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 havingequivalent insulation
qualities.
14 - All venting pipe passing through floors, walls, and
ceilings must be installed with the listed clearance
to combustible materials and be fire stopped
according to local codes. In absence of local codes,
refer to NFGC (Z223.1).
15 - No portion of the venting system can extend into,
or pass through any circulation air duct or plenum.
16 - Vent connectors serving Category I appliances shall
not be connected to any portion of mechanical draft
systems operating under positive pressure such as
Category III or IV venting systems.
Page 17
INTERIOR TILE-LINED
MASONRY CHIMNEY
NOTE - the chimney must be properly
sized per provided venting tables or
lined with listed metal lining system.
PERMANENTLY
SEALED FIREPLACE
OPENING