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Venting Using a Masonry Chimney
The following additional requirements apply when a lined
masonry chimney is used to vent this furnace.
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 met-
al liner, either the chimney must be rebuilt to accommo-
date one of these liners or an alternate approved venting
method must be found.
Insulation for the flexible vent pipe must be an encapsu-
lated fiberglass sleeve recommended by the flexible vent
pipe manufacturer. See figure 17.
Common Venting Using Metal-Lined Masonry Chimney
MAX. LENGTH
-- SEE NOTE 1
BELOW.
5 ft. (1.5 m)
MIN. LENGTH -- AS
minimum
SHORT AS PRACTICAL
VENT CONNECTOR
4 in. (102 mm)
minimum
OTHER
APPLIANCE
NOTE 1 - Refer to the provided venting tables for installations. Refer
to the capacity requirements shown in the provided venting tables.
Figure 17
DO NOT insulate the space between the liner and
the chimney wall with puffed mica or any other loose
granular insulating material
IMPORTANT
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 draft
hood equipped appliance
•
The vent connectors and chimney are sized accord-
ing to the provided venting tables.
SEALED
EXTERIOR
CHIMNEY WITH
METAL
LINER
FURNACE
PERMANENTLY
SEALED FIREPLACE
OPENING
AIR FLOW
If type B1 double-wall vent is used inside a chimney, no
other appliance can be vented into the chimney. The out-
er 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 as-
sembly 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 ML180DFE series units. 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.
Never connect a Category I appliance to a chimney that is
servicing a solid-fuel appliance. If a fireplace chimney flue
is used to vent this appliance, the fireplace opening must
be permanently sealed.
A type B or listed chimney lining system that passes
through an unused masonry chimney flue is not consid-
ered to be exposed to the outdoors.
General Venting Requirements
Vent all ML180DFE furnaces according to these instruc-
tions:
1 - Vent diameter recommendations and maximum
allowable piping runs are found in the provided
venting tables.
2 - In no case should the vent or vent connector diameter
be less than the diameter specified in the provided
venting tables.
3 - The minimum vent capacity determined by the sizing
tables must be less than the low fire input rating and
the maximum vent capacity must be greater than the
high fire input rating.
4 - Single appliance vents - If the vertical vent or tile-
lined chimney has a larger diameter or flow area than
the vent connector, use the vertical vent diameter to
determine the minimum vent capacity and the vent
connector diameter to determine the maximum vent
capacity. The flow area of the vertical vent, however,
shall not exceed 7 times the flow area of the listed
appliance categorized vent area, drafthood outlet
area or flue collar area unless designed according to
approved engineering methods.
5 - Multiple appliance vents - The flow area of the largest
section of vertical vent or chimney shall not exceed
7 times the smallest listed appliance categorized
vent area, drafthood outlet area or flue collar area
unless designed according to approved engineering
methods.
6 - The entire length of single wall metal vent connector
shall be readily accessible for inspection, cleaning,
and replacement.
Page 13
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