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10
VENTING INSTALLATION
A B-type venting system must be connected to the appliance for
venting to the outside of the building.
IHP defines installation standards of this product. Third party prod-
ucts must be installed to their specific standards.
Standing codes requirements concerning B-type vent installations
may vary within your state, province or local codes jurisdiction.
Therefore, it is recommended that you check with your local build-
ing codes for specific requirements or in absence of local codes,
follow Section 7.0 of the current National Fuel Gas Code NFPA No.
54/ANSI Z223.1.
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 adaptor or a chimney
liner system if all are listed, inspected and approved by local codes
and/or building authorities.
The examples shown in Figure 9, are typical of most B-vent instal-
lations and code practices.
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 allows 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 the Category I venting tables.
Example 2 shows a multiple offset each at 45° of inclination. Multiple
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 subfloor, 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. At all points the
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 feet distance from a vertical wall
or obstruction (see Figure 10, Page 11).
If venting horizontally through a side wall becomes necessary, a listed
thimble (38FST recommended) approved for use with B-type vent
must be used. Check with your local codes before venting through
a side wall.
Figure 9 - Typical B-Vent Configuration
Maintain
Listed
Clearance
12' Min.
45°
6'
8'
12' Min.
60°
45°
Position
Firestop
Position
Firestop
Listed
Vent Cap
Listed Vent Cap
Maintain
Listed
Clearance
Maintain
Listed
Clearance
Maintain
Listed
Clearance
Support
Each
Lateral
At Least
Every
6 Feet
Maintain
Listed
Clearance
EXAMPLE 2
EXAMPLE 1
Maintain
Listed
Clearance
12' Min.
45°
Position
Firestop
Listed
Vent Cap
Maintain
Listed
Clearance
10'
EXAMPLE 3
