1.8.6 CHIMNEY & VENT CONSTRUCTION (VERTICAL SECTION)
INSTALLATION OF FACTORY BUILT
SYSTEMS
Listed gas vents and factory built chimneys must
be installed in accordance with their listings and
the manufacturer's instructions. Vents and
venting systems passing through roofs must
extend though the roof flashing, roof thimble or
roof jack.
INSTALLATION OF MASONRY OR METAL
CHIMNEYS
Masonry or metal chimneys must be built in
accordance with nationally recognized building
codes and standards.
INSTALLATION OF SINGLE WALL GAS VENTS
Single wall metal pipe may be used only for runs
directly from the space in which the appliance is
located through the roof or exterior wall to the
outer air. A pipe passing through a roof must
extend without interruption through the roof
flashing, roof jack or thimble. Single wall metal
pipe must not originate in any unoccupied attic or
concealed space. Additionally, it must not pass
through any attic, inside wall, concealed space or
through any floor. Minimum clearance must be
maintained between the single wall metal pipe
and any combustible surface as outlined in Table
1.8.9.
When a single wall metal pipe passes through an
exterior wall constructed of combustible material,
it must be guarded at the point of passage by a
ventilated thimble as described under "Use of
Thimbles" in Section 1.8.8 of this manual.
Alternatively, a non-ventilating thimble not less
than 18" above and 6" below the roof (with the
annular space open at the bottom and closed at
the top) may be used.
INSPECTIONS OF CHIMNEYS
Before connection of a vent connector to a
chimney, the chimney passageway must be
examined to ascertain that it is clear and free of
obstructions. Cleanouts must be constructed
such that they will remain tightly closed when not
in use. Tee fittings used as cleanouts or
condensate drains must have tight fitting caps to
prevent entrance of air into the chimney at such
points. When an existing masonry chimney is
unlined and local experience indicates that vent
gas condensate may be a problem, an approved
liner or another vent must be installed. When
inspection reveals that an existing chimney is not
safe for the intended application, it must be rebuilt
to conform to nationally recognized standards,
relined with a suitable liner, or replaced with a gas
vent or chimney suitable for the appliances to be
attached.
SUPPORT OF CHIMNEYS AND VENTS
All portions of chimneys must be adequately
supported for the design and weight of the
materials employed. Listed factory built chimneys
must be supported and spaced in accordance
with their listings and the chimney or gas vent
manufacturer's recommendations.
THE GAS VENT OR CHIMNEY MUST BE
SUPPORTED INDEPENDENTLY OF THE
BOILER TOP OR DRAFT DIVERTER.
EQUIPMENT TYPE
MINIMUM REQUIRED DISTANCE FROM COMBUSTIBLE MATERIAL
Listed Vent
Single Wall Metal Pipe
Factory Built Chimney
Water and 15 psig Steam Boilers
not permitted
18"
as listed
All Steam Boilers over 15 psig
not permitted
36"
as listed
Summary of Contents for Forced Draft Steam Boilers
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