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A B-type venting system must be connected to the appliance for
venting to the outside of the building.
The following section is provided as a guide to a standard B-type
vent installation.
Standing codes requirements concerning B-type vent installations
may vary within your state, province or local codes jurisdiction. There-
fore, it is recommended that you check with your local building codes
for specific requirements or in absence of local codes, follow Section
7.0 of the current National Fuel Gas Code ANSI Z223.1/NFPA 54.
This gas appliance must be vented to the outdoors only and may not
be terminated into an attic space or into a chimney flue servicing a
solid fuel burning appliance.
This appliance may be vented through a manufactured chimney
system or a masonry chimney using a B-vent adapter or a chimney
liner system if all are listed, inspected and approved by local codes
and/or building authorities.
The examples shown in Figure 10, are typical of most B-vent instal-
lations and codes practices. A minimum of 3 feet vertical rise (off the
top of the unit) before offset is recommended.
Example 1: Shows the minimum allowable system height and lateral
offset for a 60° or greater inclination. Code specifies that offsets at
60° or greater are considered horizontal and must follow the 75%
rule for lateral to total vertical system height. Codes also allow only
one offset in the total system when at 60° or greater. The total vertical
height in this example represents the minimum height of 8 feet and
therefore the allowable lateral is 6 feet when the 75% rule applies. If
the lateral length must exceed 75% then the system must be sized
in accordance with Category I venting tables.
Maintain
Listed
Clearance
8'
(2.44 m)
Position
Firestop
12' Min.
(3.66 m) Min.
EXAMPLE 1
8
VENTING INSTALLATION
Listed Vent Cap
Maintain
Listed
Clearance
Support Each
Lateral At
60°
Least Every
6 Feet
Position
6' (1.83 m)
Firestop
Maintain
Listed
Clearance
EXAMPLE 2
Figure 10 - Typical B-Vent Configuration
SuperiorFireplaces.US.com
Example 2: Shows a multiple offset each at 45° of inclination. Mul-
tiple offsets are permitted if they do not exceed 45° of inclination.
The total lengths of the two offsets are not required to meet the 75%
allowable rule.
Example 3: Shows a single offset at 45° of inclination and therefore
the lateral length at 10 feet of offset does not have to meet the 75%
rule.
In each case the offsets must be supported and firestops must be
positioned wherever the vent must pass through a sub-floor, ceiling
joist or an attic overhang. The vent pipe must terminate vertically
into a listed type vent cap and extend a sufficient height through an
approved roof flashing, roof jack or a roof thimble (38FST recom-
mended). At all points listed clearances must be maintained.
Vent terminations must be located in accordance with height and
proximity rules of NFPA No. 54. These rules apply to vents at 12"
diameter or less and require a minimum height in accordance with
the roof pitch and a minimum of 8 ft. distance from a vertical wall or
obstruction (see Figure 11, page 9).
Listed Vent Cap
Maintain
Listed
Clearance
45°
Position
Firestop
45°
12' Min.
(3.66 m) Min.
Maintain
Listed
Clearance
Listed Vent Cap
Maintain
Listed
Clearance
45°
10' (3.05 m)
(3.66 m) Min.
Maintain
Listed
Clearance
EXAMPLE 3
12' Min.
126736-01_E
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