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Masonry chimneys used to vent Category I central furnaces
must be either tile lined or lined with a listed metal lining
system or dedicated gas vent. Unlined masonry chimneys
are prohibited. See Figure 24 and Figure 25 for common
venting.
A chimney with one or more sides exposed to the outside
of the structure is considered to be an exterior chimney.
An exterior masonry chimney that is not tile lined must be
lined with B1 vent or a listed insulated flexible metal vent.
An exterior tile lined chimney that is sealed and capped
may be lined with a listed uninsulated flexible metal vent.
If the existing chimney will not accommodate a listed metal
liner, either the chimney must be rebuilt to accommodate
one of these liners or an alternate approved venting
method must be found.
Insulation for the flexible vent pipe must be an encapsulated
fiberglass sleeve recommended by the flexible vent pipe
manufacturer. See Figure 24.
NOTE 1: Refer to the provided venting tables for installations.
Refer to the capacity requirements shown in the provided
venting tables.
Figure 24. Common Venting Using Metal-Lined
Masonry Chimney
NOTE: Refer to provided
venting tables for installations.
Figure 25. Common Venting Using Tile Lined Interior Masonry Chimney and Combined Vent Connector
507335-03
DO NOT insulate the space between the liner and the
chimney wall with puffed mica or any other loose granular
insulating material.
SINGLE appliance venting of a fan assisted furnace into
a tile lined masonry chimney (interior or outside wall) is
prohibited. The chimney must first be lined with either
type B1 vent or an insulated single wall flexible vent
lining system which has been sized according to the
provided venting tables and the vent pipe manufacturer's
instructions.
A fan assisted furnace may be commonly vented into an
existing lined masonry chimney if the following conditions
are met:
•
The chimney is currently serving at least one drafthood
equipped appliance.
•
The vent connectors and chimney are sized according
to the provided venting tables.
If type B1 double wall vent is used inside a chimney, no
other appliance can be vented into the chimney. The outer
wall of type B1 vent pipe must not be exposed to flue
products. A type B1 vent or masonry chimney liner shall
terminate above the roof surface with a listed cap or a listed
roof assembly according to the terms of their respective
listings and the vent manufacturer's instructions.
When inspection reveals that an existing chimney is not
safe for the intended purpose, it shall be rebuilt to conform
to nationally recognized standards, lined or relined with
suitable materials, or replaced with a gas vent or chimney
suitable for venting. The chimney passageway must be
checked periodically to ensure that it is clear and free of
obstructions.
Do not install a manual damper, barometric draft regulator,
or flue restrictor between the furnace and the chimney.
Issue 2302
IMPORTANT
NOTE: The chimney must be properly
sized per provided venting tables or lined
with listed metal lining system.
Page 15 of 39
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