General Venting Requirements - Lennox G23Q2-50 Unit Information

If "B" vent or an insulated flexible vent pipe cannot be used
as liners, the chimney must be rebuilt to accommodate
one of these methods or some alternate approved method
must be found to vent the appliance.
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 G23(X) series units. The chimney pas-
sageway must be checked periodically to ensure that it is
clear and free of obstructions.

General Venting Requirements

All G23(X) furnaces must be vented in accordance with
the methods outlined in these instructions.
1 - Vent diameter recommendations and maximum runs
allowed 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 - For 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, how-
ever, shall not exceed 7 times the flow area of the
listed appliance categorized vent area, drafthood out-
let area or flue collar area unless designed in accor-
dance with approved engineering methods.
4 - For multiple appliance vents: The flow area of the
largest section of vertical vent or chimney shall not ex-
ceed 7 times the smallest listed appliance catego-
rized vent area, flue collar area or drafthood outlet
area unless designed in accordance with approved
engineering methods.
5 - The entire length of single wall metal vent connector
shall be readily accessible for inspection, cleaning,
and replacement.
6 - Single appliance venting configurations with zero lat-
eral lengths, see tables 9 and 10, 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 percent
(0.90 x maximum listed capacity).
7 - The common venting tables 11, 12, 13, and 14 were
generated using a maximum horizontal vent connec-
tor length of 1-1/2 feet (18 inches) for each inch of
connector diameter as follows:
CONNECTOR
DIAMETER
(INCHES)
8 - 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 ca-
pacity). The horizontal length of the offset shall not ex-
ceed 1-1/2 feet for each inch of common vent diame-
ter.
9 - The vent pipe should be as short as possible with
the least number of elbows and angles to do the
job. The vent connector should be routed to the vent
utilizing the shortest possible route.
10- A vent connector shall be supported without any dips
or sags and shall slope a minimum of 1/4" per linear
foot of connector, back towards the appliance.
11- Vent connectors shall be firmly attached to furnace
flue collars by sheet metal screws or other approved
means, except vent connectors of listed Type "B" vent
material which shall be assembled in accordance
with the manufacturer's instructions. Joints between
sections of single wall connector piping shall be fas-
tened by sheet metal screws or other approved
means.
12- When the vent connector used for Category I ap-
pliances must be located in or pass through a crawl
space or other areas which may be cold, that portion
of the vent connector shall be listed double-wall Type
B vent material or material having equivalent insula-
tion qualities.
13- 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).
14- No portion of the venting system can extend into, or
pass through any circulation air duct or plenum.
15- Vent connectors serving Category I appliances shall
not be connected to any portion of mechanical draft
systems operation under positive pressure such as
Category III or IV venting systems.
16- If vent connectors are combined prior to entering the
common vent, the maximum common vent capacity
listed in the common venting tables must be reduced
by 10%, the equivalent of one 90 - elbow (0.90 x maxi-
mum common vent capacity).
17- Common vent diameter must always be at least as
large as the largest vent connector diameter.
3DJH 
MAXIMUM HORIZONTAL
CONNECTOR LENGTH
3
4
5
6
7
(FEET)
4-1/2
6
7-1/2
9
10-1/2