3 - For single appliance vents: If the verticalvent 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 flowareaof thevedicelvent,how-
ever, shall not exceed 7 times the flow area of the
listedappliancecategorizedvent area, drefthcodout-
letarea or flue cellar area unlessdesignedaccording
to approvedengineeringmethods.
4 - For multiple appliance vents: The flowarea ofthelarg-
estsectionofvertical vent or chimneyshallnotexceed
7 times thesmallest listed appliancecetegefized vent
area, drafthoodoutlet area or flue collararea unless
designedaccording to approved engineering meth-
ods.
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 4 and 5, are assumed to have
no elbows in the vent system. For all other vent config-
urations, the vent system is assumed to have two 90°
elbows. For each additional 90° elbowor equivalent
(for example two 45° elbows equal one 90° elbow) be-
yond two, the maximum capacity listed in the venting
table should be reduced by 10 percent (0.90 x maxi-
mumlisted capacity).
7 - The common venting tables 6, 7, 8, and 9 were gener-
ated using a maximum hodzontal vent connector
length of 1-1/2 feet (.46 m) for each inch (25 ram) of
connector diameter as follows:
TABLE 3
Connector
Diameter
inches (ram)
3(76)
4(102)
5 (127)
s(152)
7 (178)
Maximum Horizontal
Connector Length
feet (m)
4-1/2 (1.37)
s (1.e3)
7-tr2(2.29)
8 (2.74)
10-1/2 (3.20}
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 hodzontal length of the offset shallnot ex-
ceed 1-1/2feet (.46 m) for each inch (25 ram) of cem-
mon vent diameter.
9- The vent pipe should be as short as possible with
the least number of elbows and angles required to
complete the job. The vent connector should be
routed to the vent using the shortest possible route.
10- A vent connector shall be supported without any dips
or sags and shall slope a minimum of 1/4 inch (6.4
ram) per linear foot (305 mm) of connector, back to-
ward the appliance. See local and national installation
codes for support intervals and methods. National
installation code in the USA is current edition of Na-
tional fuel Gas Code (ANSI-Z223.1). National installa-
tion codes in Canada are current editions of CAN/
CGA-B149 codes.
11- Vent connectors shall be firmly attached to fumace
flue collars by screws or other approved means, ex-
cept vent connectors of listed type B vent material
which shall be assembled according to the manufac-
turer's instructions. Joints between sections of single
wall connector piping shall be fastened by screws or
otherapproved means.
12- When the vent connector used for Category I ap-
pliances must be located in or pass through a crawl-
space or other areaswhich may be cold, that portion of
the vent connector shall be constructed of listed
double-wall type B vent material or matedal having
equivalent insulation qualities.
13- All venting pipe passingthrough floors, walls, and ceil-
ings must be installed with the listed clearance to com-
bustible materials and be fire stopped according to lo-
cal codes. In absence of local codes, referto NFGC
(Z223.1).
14- No portionof theventing system can extendinto,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 operating 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 inthe commonventing tables mustbe reducedby
10%,the equivalent of one 90° elbow (0.90x maximum
common vent capacity).
17- The common vent diameter must always be at leastas
large as the largest vent connector diameter.
18- In no case, shall the vent connector be sized more
than two consecutive table size diameters over the
size of the draft hood outlet or flue collar outlet.
19- Do not install a manual damper, barometric draft regu-
lator or flue restdctor between the furnace and the
chimney.
20- When connecting this appliancetoan existingdedicated
or common venting system,the venting system mustbe
inspected for signs of corrosion and general condition.
The sizing of the vent system must be reviewedand
mast conform to these instructions and the provided
venting tables for the USA, and the appropriateventing
tables in the standards of CAN/CGA B149.1 and
B149.2 of the Natural Gas and Propane Installation
Code forCanada. If the existingsystem is inconflictwith
these requirements, the venting system must be re-
sized.
Page 14
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