EQUIPMENT TYPE
MINIMUM REQUIRED DISTANCE FROM COMBUSTIBLE MATERIAL
Listed Type B Vent
Single Wall Metal
Pipe
Factor Built Chimney
UL Listed F-Series Water or 15 psig
Steam with Draft Diverter
as listed
6" as listed
UL Listed CL-Series Water or 15 psig
Steam with Draft Diverter or Barometric
as listed
6" as listed
UL Listed K-Series Water with Draft
Diverter or Barometric
as listed 6" as listed
UL Listed K-Series 15 psig Steam with
Draft Diverter
as listed 6" as listed
UL Listed K-Series 15 psig Steam with
Barometric
not permitted 18" as listed
Unlisted Water and 15 psig Steam
Boilers
not permitted 18" as listed
All Steam Boilers over 15 psig
Regardless of Draft Control
not permitted 36" as listed
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 recommendation. THE GAS
VENT OR CHIMNEY MUST BE SUPPORTED
INDEPENDENTLY OF THE BOILER TOP OR
DRAFT DIVERTER.
1.8.10 MARKING OF GAS VENTS
In those localities where solid and liquid fuels are
used extensively, gas vents must be plainly and
permanently identified by a label reading:
"This gas vent is for appliances which burn gas
only. Do not connect to incinerators or solid or
liquid fuel burning appliances."
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