Table 803.2(1) through Table 803.2(9) shall not be used where obstructions are installed in the venting
system. The installation of vents serving listed appliances
with vent dampers shall be in accordance with the appliance manufacturer's installation instructions or in accordance with
the following:
The maximum capacity of the vent connector shall be
determined using the NAT Max column.
The maximum capacity of the vertical vent or chimney
shall be determined using the FAN + NAT column where
the second appliance is a fan-assisted appliance, or the
NAT + NAT column where the second appliance is
equipped with a draft hood.
The minimum capacity shall be determined as if the
appliance were a fan-assisted appliance, as follows:
The minimum capacity of the vent connector shall be
determined using the FAN Min column.
The FAN + FAN column shall be used where the
second appliance is a fan-assisted appliance, and the
FAN + NAT column shall be used where the second
appliance is equipped with a draft hood, to determine
whether the vertical vent or chimney configuration is
not permitted (NA). Where the vent configuration is
NA, the vent configuration shall not be permitted and
an alternative venting configuration shall be utilized.
[NFPA 54:13.2.1]
TABLE 803.2(1)
TYPE B DOUBLE-WALL VENT [NFPA 54: TABLE 13.2(a)]*
For SI units: 1 inch = 25.4 mm, 1 foot = 304.8 mm, 1000 British thermal units per hour = 0.293 kW, 1 square inch = 0.000645 m2
* NA: Not applicable.
TABLE 803.2(2)
TYPE B DOUBLE-WALL VENT [NFPA 54: TABLE 13.2(b)]*
For SI units: 1 inch = 25.4 mm, 1 foot = 304.8 mm, 1000 British thermal units per hour = 0.293 kW, 1 square inch = 0.000645 m2
* NA: Not applicable.
TABLE 803.2(3)
MASONRY CHIMNEY [NFPA 54: TABLE 13.2(c)]*
For SI units: 1 inch = 25.4 mm, 1 foot = 304.8 mm, 1000 British thermal units per hour = 0.293 kW, 1 square inch = 0.000645 m2
* NA: Not applicable.
TABLE 803.2(4)
MASONRY CHIMNEY [NFPA 54: TABLE 13.2(d)]*
For SI units: 1 inch = 25.4 mm, 1 foot = 304.8 mm, 1000 British thermal units per hour = 0.293 kW, 1 square inch = 0.000645 m2
* NA: Not applicable.
For SI units: 1 inch = 25.4 mm, 1 foot = 304.8 mm, 1000 British thermal units per hour = 0.293 kW, 1 square inch = 0.000645 m2
* NA: Not applicable
TABLE 803.2(5)
SINGLE-WALL METAL PIPE OR TYPE B ASBESTOS-CEMENT VENT [NFPA 54:TABlE 13.2(e)]*
For SI units: 1 inch = 25.4 mm, 1 foot = 304.8 mm, 1000 British thermal units per hour = 0.293 kW, 1 square inch = 0.000645 m2
* NA: Not applicable.
TABLE 803.2(6)
EXTERIOR MASONRY CHIMNEY [NFPA 54: TABLE 13.2(f)]*
For SI units: 1 inch = 25.4 mm, 1 foot = 304.8 mm, 1000 British thermal units per hour = 0.293 kW, 1 square inch = 0.000645 m2
* NA: Not applicable.
TABLE 803.2(7)
EXTERIOR MASONRY CHIMNEY [NFPA 54: TABLE 13.2(9)]1, 2For SI units: 1 inch = 25.4 mm, 1 foot = 304.8 mm, 1000 British thermal units per hour = 0.293 kW, 1 square inch = 0.000645 m2, °C = (°F-32)/1.8
Notes: 1 See Figure 803.1.2(6) for a map showing loca1 99 percent winter design temperatures in the United States. 2 NA: Not applicable.
TABLE 803.2(8)
EXTERIOR MASONRY CHIMNEY [NFPA 54: TABLE 13.2(h)]*
For SI units: 1 inch = 25.4 mm, 1 foot = 304.8 mm, 1000 British thermal units per hour = 0.293 kW, 1 square inch = 0.000645 m2
* NA: Not applicable.
TABLE 803.2(9)
EXTERIOR MASONRY CHIMNEY [NFPA 54: TABLE 13.2(i)]1, 2For SI units: 1 inch = 25.4 mm, 1 foot = 304.8 mm, 1000 British thermal units per hour = 0.293 kW, 1 square inch = 0.000645 m2, °C = (°F-32)/1.8
Notes: 1 See Figure 803.1.2(6) for a map showing loca1 99 percent winter design temperatures in the United States. 2 NA: Not applicable.
The
maximum vent connector horizontal length shall be 18
inches per inch (18 mm/mm) of connector diameter as
shown in Table 803.2.1, or as permitted by Section 803.2.2.
[NFPA 54:13.2.2]
TABLE 803.2.1
VENT CONNECTOR MAXIMUM LENGTH
[NFPA 54: TABLE 13.2.2]
The vent connector shall be routed to the vent utilizing
the shortest possible route. Connectors with longer horizontal
lengths than those listed in Table 803.2.1 are
permitted under the following conditions:
The maximum capacity (FAN Max or NAT Max) of
the vent connector shall be reduced 10 percent for each
additional multiple of the length listed in Table 803.2.1.
For example, the length listed for a 4 inch (l02 mm)
connector shall not exceed 6 feet (1829 mm). With a
connector length exceeding 6 feet (1829 mm) but not
exceeding 12 feet (3658 mm), the maximum capacity
shall be reduced by 10 percent (0.90 x maximum vent
connector capacity). With a connector length exceeding
12 feet (3658 mm) but not exceeding 18 feet (5486
mm), the maximum capacity shall be reduced by 20
percent (0.80 x maximum vent capacity).
For a connector serving a fan-assisted appliance, the
minimum capacity (FAN Min) of the connector shall
be determined by referring to the corresponding
single appliance table. For Type B double-wall
connectors, Table 803.1.2(1) shall be used. For
single-wall connectors, Table 803.1.2(2) shall be
used. The height (H) and lateral (L) shall be measured
according to the procedures for a single-appliance
vent, as though the other appliances were not
present. [NFPA 54:13.2.3]
Where the vent
connectors are combined prior to entering the vertical
portion of the common vent to form a common vent manifold,
the size of the common vent manifold and the
common vent shall be determined by applying a 10 percent
reduction (0.90 x maximum common vent capacity) to the
common vent capacity part of the common vent tables.
The length of the common vent manifold (LM) shall not
exceed 18 inches per inch (18 mm/mm) of common vent
diameter (D). (See Figure 802.6.4.2) [NFPA 54:13.2.4]
Where the common vertical vent is
offset, the maximum capacity of the common vent shall be
reduced in accordance with Section 803.2.5, and the horizontal length
of the common vent offset shall not exceed
18 inches per inch (18 mm/mm) of common vent diameter
(D). Where multiple offsets occur in a common vent, the total horizontal length of offsets combined shall not exceed
18 inches per inch (18 mm/mm) of the common vent diameter.
[NFPA 54:13.2.5]
For each elbow up to and
including 45 degrees (0.79 rad) in the common vent, the
maximum common vent capacity listed in the venting
tables shall be reduced by 5 percent. For each elbow
exceeding 45 degrees (0.79 rad) up to and including 90
degrees (1.57 rad), the maximum common vent capacity
listed in the venting tables shall be reduced by 10 percent.
[NFPA 54:13.2.6]
Tee and wye fittings
connected to a common gas vent shall be considered as
part of the common gas vent and constructed of materials
consistent with that of the common gas vent. [NFPA
54:13.2.9]
At the point where tee or wye
fittings connect to a common gas vent, the opening size
of the fitting shall be equal to the size of the common
vent. Such fittings shall not be prohibited from having
reduced size openings at the point of connection of appliance
gas vent connectors. [NFPA 54:13.2.10]
Sea level input
ratings shall be used where determining maximum capacity
for high-altitude installation. Actual input (derated for altitude)
shall be used for determining minimum capacity for
high-altitude installation. [NFPA 54:13.2.11]
The connector rise (R) for each
appliance connector shall be measured from the draft hood
outlet or flue collar to the centerline where the vent gas
streams come together. [NFPA 54:13.2.12]
For multiple appliances located on
one floor, the total height (H) shall be measured from the
highest draft hood outlet or flue collar up to the level of the
outlet of the common vent. [NFPA 54:13.2.13]
For multistory installations,
the total height (H) for each segment of the system
shall be the vertical distance between the highest draft hood
outlet or flue collar entering that segment and the centerline
of the next higher interconnection tee. (See Figure
803.2.12) [NFPA 54:13.2.14]
FIGURE 803.2.12
MULTISTORY GAS VENT DESIGN PROCEDURE
FOR EACH SEGMENT OF SYSTEM
[NFPA 54: FIGURE F.1(m)]
The
size of the lowest connector and of the vertical vent
leading to the lowest interconnection of a multistory
system shall be in accordance with Table 803.1.2(1) or Table 803.1.2(2) for available total height (H) up to the
lowest interconnection. (See Figure 803.2.13) [NFPA
54:13.2.15]
FIGURE 803.2.13
PRINCIPLES OF DESIGN OF MULTISTORY VENTS USING
VENT CONNECTOR AND COMMON VENT DESIGN TABLES
[NFPA 54: FIGURE F.1(n)]
Offsets in
multistory common vent systems shall be limited to a
single offset in each system, and systems with an offset
shall comply with the following:
The offset angle shall not exceed 45 degrees (0.79
rad) from vertical.
The horizontal length of the offset shall not exceed
18 inches per inch (18 mm/mm) of common vent
diameter of the segment in which the offset is located.
For the segment of the common vertical vent
containing the offset, the common vent capacity listed
in the common venting tables shall be reduced by 20
percent (0.80 x maximum common vent capacity).
A multistory common vent shall not be reduced in
size above the offset. [NFPA 54:13.2.17]
Where two or
more appliances are connected to a vertical vent or
chimney, the flow area of the largest section of vertical
vent or chimney shall not exceed seven times the smallest
listed appliance categorized vent areas, flue collar area,
or draft hood outlet area unless designed in accordance
with approved engineering methods. [NFPA 54:13.2.18]
For appliances with
more than one input rate, the minimum vent connector
capacity (FAN Min) determined from the tables shall be
less than the lowest appliance input rating, and the
maximum vent connector capacity (FAN Max or NAT
Max) determined from the tables shall exceed the highest
appliance input rating. [NFPA 54:13.2.19]
Listed, corrugated metallic chimney liner systems in
masonry chimneys shall be sized by using Table 803.2(1)
or Table 803.2(2) for Type B vents, with the maximum
capacity reduced by 20 percent (0.80 x maximum capacity)
and the minimum capacity as shown in Table 803.2(1) or
Table 803.2(2). Corrugated metallic liner systems installed
with bends or offsets shall have their maximum capacity
further reduced in accordance with Section 803.2.5. The
20 percent reduction for corrugated metallic chimney liner
systems includes an allowance for one long radius 90
degree (1.57 rad) turn at the bottom of the liner. [NFPA
54:13.2.20]
Where a
table permits more than one diameter of pipe to be used
for a connector or vent, all the permitted sizes shall be
permitted to be used. [NFPA ...
Vent connectors shall
not be increased more than two sizes exceeding the listed
appliance categorized vent diameter, flue collar diameter,
or draft ...
, and the horizontal length
of the common vent offset shall not exceed
18 inches per inch (18 mm/mm) of common vent diameter
( D ). Where multiple offsets occur ...
The
maximum vent connector horizontal length shall be 18
inches per inch (18 mm/mm) of connector diameter as
shown in Table 803.2.1, or as permitted ...
