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9
VENTING INSTALLATION
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 fi restops must be
positioned wherever the vent must pass through a sub-fl oor, ceiling
joist or an attic overhang. The vent pipe must terminate vertically
into a listed type vent cap and extend a suffi cient height through an
approved roof fl ashing, 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 ANSI Z223.1/NFPA 54, or the Natural Gas and
Propane Installation Code, CSA B149.1. 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 10
).
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.
Therefore, it is recommended that you check with your local building
codes for specifi c requirements or in absence of local codes, follow
Section 7.0 of the current National Fuel Gas Code ANSI Z223.1/NFPA
54, or the Natural Gas and Propane Installation Code, CSA B149.1.
This gas appliance must be vented to the outdoors only and may
not be terminated into an attic space or into a chimney fl ue serving
a separate 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 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 specifi es 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
Maintain
Listed
Clearance
Maintain
Listed
Clearance
Maintain
Listed
Clearance
Maintain
Listed
Clearance
Maintain
Listed
Clearance
Maintain
Listed
Clearance
12
'
Min.
(3.66 m) Min.
12
'
Min.
(3.66 m) Min.
8
'
(2.44 m)
12
'
Min.
(3.66 m) Min.
6
'
(1.83 m)
10
'
(3.05 m)
45°
45°
45°
60°
Position
Firestop
Position
Firestop
Position
Firestop
Listed Vent Cap
Listed Vent Cap
Listed Vent Cap
Support Each
Lateral At
Least Every
6 Feet
EXAMPLE 3
EXAMPLE 2
EXAMPLE 1
Figure 10 - Typical B-Vent Confi guration
IMPORTANT NOTICE
ANSI Z223.1/NFPA 54 (USA), or CSA B149.1 (Canada)
defi nes minimum space requirements for the instal-
lation of this appliance.
This fi replace must be installed in an unconfi ned space
with a minimum of 50 cubic feet per 1,000 BTUs of gas
output. Therefore 36” models require 2,650 cubic feet,
42” models require 3,100 cubic feet and 50” models
require 3,300 cubic feet. If the space you wish to in-
stall the fi replace does not meet these requirements
ANSI Z223.1/NFPA 54 or CSA B149.1 details several
actions that may be taken.
