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If an exterior location is necessary, an exterior
located Gas Vent (as per Figure 3) must be:
- Enclosed by a chase spaced out 1" from
the vent at least to the roof line.
- The enclosure should be caulked to prevent
entry of moisture.
- It is also recmommended that his chase be
insulated to a minimum of R-12 (RSI 2.1).
- Rigid type insulation is recommended. If
a non rigid type is use, it must be restrained
in such a manner so that the required
minimum air space clearance to combustible
is respected.
- The bottom of the enclosure must be closed
off.
- It is recommended to provide an access
panel for future inspection and cleaning of
the vent.
Adjustable
Flashing
Wall
Support/
Band
R12 Min.
Insulation
25mm (1")
Clearance to
Combustible
Material
FIG.3 - Exterior
Enclosed Type B Gas
Vent
Use an Attic Insulation
Shield in the attic
DuraCap
space or
Cap
enclosedthe vent
completely. Maintain
Storm Collar
the required minimum
airspace clearance
to enclosure, wires and
Attic
building insulation.
Insulation
Shield
Wall
Firestop
Spacer or
Wall Thimble
Fixed
Length
NOTE: DIAGRAMS & ILLUSTRATIONS ARE NOT TO SCALE.
Appliances served by an exterior gas vent
must have an air supply to the appliance
room adequate to balance indoor and outdoor
pressures. Otherwise, "stack action" of the
heated building can cause reverse venting
action when the appliance is off, or operating
on its pilot.
In multi-family residential, high rise and many
other types of buildings, codes specify that
vents must be located in fire-rated shafts or
chases. Building code requirements in such
cases must be carefully followed with respect
to wall construction, access, clearance,
support, initial penetration of breaching, and
method of termination.
Attic
Insulation
Shield
Tee
Tee Cap
6. VENT CONNECTOR TYPE AND SIZE
Model BV Type B Gas Vent meets all building
codes and safety standards for use as gas
appliance vent connectors. Correct selec-
tion of connector and vent size is detailed
in the "National Fuel Gas Code" (NFPA 54)
and the Canadian Gas Installation Code
CSA-B149.1-00, and/or local/regional codes.
Draft Hood connectors must be attached to
the appliance outlet with screws. Single wall
connectors, if used must be secured to the
appliance, to the gas vent, and at all joints with
3 sheet metal screws per joint. Attachment
of vent to non-metallic outlets should be per
appliance manufacturer recommendations.
NOTE: See the Large Diameter Model BV in
Section 2 for the requirement of Draft Hood
Connectors.
Type B Gas Vent
Storm Collar
Adjustable Flashing
FIG. 4 -
Typical Ceiling
and Roof
Penetrations
(Attic)
Adjustable
Length
Vent
7
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