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Existing Masonry Chimneys
If you plan on using an existing masonry chimney,
have it thoroughly inspected and cleaned. Any faults
which make the chimney unsafe and unusable must be
repaired prior to use. These can include improper height,
structural defects, blockages, inadequate clearance to
combustibles, unsealed openings into other rooms of the
house, signs of creosote or smoke leakage, a loose or
absent clean-out door, or absence of a liner.
Do not connect to any air distribution
duct or system
Venting to a Masonry Chimney
When connecting to a masonry chimney, several
provisions are standard. First, whether the chimney con-
nector is vented to the chimney through a thimble or a
breech pipe, neither must pass beyond the inner surface
of the chimney liner, and both must be firmly cemented
in place with refractory cement. (A thimble is a masonry
pipe which is inserted through the chimney wall, and is
frequently the preferred method; a breech pipe is a piece
of steel pipe used the same way.) In Canada, a breech pipe
has ridges or protrusions to lock it firmly into the refrac-
tory cement. In either case, the chimney connector vents
to the chimney through the thimble or breech pipe.
Using a thimble, the connector slides completely inside
the masonry to the inner edge of the flue liner, and may
be easily removed for chimney and connector inspection.
A breech pipe must extend at least 2" (50 mm) into the
room, so the connector can be attached with sheetmetal
screws.
Venting to a Masonry Fireplace Chimney
In some situations, a code compliant chimney originally
used for a masonry fireplace may be used to install your
Oakwood. In addition to the requirements found in the
previous paragraphs, it is important to be aware that all
clearances must be met, including those from the chimney
connector to combustibles — 18" (360 mm) to sides and
18" (450 mm) to ceiling. Do not forget to include floor
protection in your plans. (See Clearances and Floor
Protection in this section.) Since many fireplaces have
exposed wooden mantels and trim, pay special attention
to the clearances necessary to these materials.
If your fireplace chimney is behind a combustible wall,
you must use an approved wall pass-through system to
gain access to the masonry chimney. The chimney con-
nector must enter the chimney at a place where it is lined,
and the fireplace must be made inoperable. For example,
you might remove the damper, replacing it with a secure,
Harman Oakwood
18
ventIng
airtight, noncombustible seal, like a steel plate (remov-
able for inspection); this also satisfies the requirement
that no room air must be allowed to enter the chimney.
Kaowool, mineral wool or equivalent non-combustible
insulation may be installed on top of the plate to help
minimize condensation. (Install a rain cap on the top of
the chimney).
Installing to a Prefabricated Chimney
When venting your Oakwood using a prefabricated
chimney, be sure to contact local building code authori-
ties, and to follow the manufacturer's instructions exactly.
Use only the manufacturer's parts; do not use makeshift
installation techniques. All prefabricated chimneys must
be tested to either the U.S. or Canadian high-temperature
standards, UL 103 or ULC-629.
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