Harman Oakwood - Chimneys and Venting; Draft; Chimney Connectors; Wall Pass-throughs

16 Harman Oakwood
3-90-08327R26_03/14
Chimney Connectors and Chimneys
Draft
Draft is widely misunderstood. It is important that you, the
stove operator, realize that draft is a variable effect, not a
given quantity. Stoves and chimneys do not have draft, yet
draft is the key to your stove’s performance.
Draft is a force, produced by an operating stove and the
chimney to which it is attached. It is created by hot gases
rising up the chimney, creating a pressure difference
between the inside of your home and the outside air. It
continually moves fresh combustion air into the stove, and
hot exhaust gases out of the stove; without this constant
ow, the re will go out.
Other factors, such as barometric pressure, winds, the
airtightness of the home, the total inside chimney volume,
chimney height and the presence of venting devices such
as exhaust fans also play a role in maintaining an adequate
draft. Low barometric pressures, super insulated homes and
exhaust fans can reduce draft; winds can play havoc with
draft; and too large or too small a chimney volume can cause
reduced draft due to the excessive cooling or not enough
room to vent exhaust gases. Introducing outside air directly
to the stove may help remedy a low draft problem. Some
signs of inadequate draft are smoking, odor, difculty in
maintaining the re, and low heat output. Overdraft can be
caused by a very tall chimney even if it is the recommended
size, and can cause overring of your stove. Signs of an
overdraft include rapid fuel consumption, inability to slow
the re, and parts of the stove or chimney connector glowing
red. It is important that you follow the chimney guidelines in
this manual, including size, type, and height to avoid draft
problems.
When installed and operated according to this manual, the
Oakwood will produce enough hot gases to keep the chimney
warm so that adequate draft is maintained throughout the
burn cycle.
Chimney Connectors
In general, following these guidelines will ensure compliance
with all national and provincial codes; prior to beginning your
installation, check with your local building code ofcial to
check on additional local regulations which may inuence
the design and placement of your venting system.
The Harman® Oakwood may be installed with a minimum
(.6 mm) 24 gauge chimney connector pipe. The size of the
connector should correspond to the size of the ue collar
opening. Do not use makeshift compromises. No part of the
chimney connector may pass through an attic or roof space,
closet or other concealed space, or through a oor or ceiling.
Whenever possible, avoid passing the connector through a
combustible wall; if you must, use an approved wall pass-
through, described later in this section.
VENTING
Assemble the connector beginning at the ue collar, with the
crimped ends pointing towards the stove (to keep debris and
creosote akes inside the system). Each joint, including the
one to the stove’s ue collar and the one to the chimney itself
should be secured with at least three sheet metal screws.
Screws may be a maximum of 3 inches apart. A 1-1/4" (30
mm) overlap is required at each joint, including the ue collar
attachment. No more than two 90 degree elbows should be
used, and the total length of connector should not exceed
10 feet (3 m). All horizontal runs of connector must have a
minimum upward slope of 1/4"(6 mm) per foot (20 mm per
meter).
Chimney connector should correspond to the size of the ue
collar opening. Do not use makeshift compromises. No part
of the chimney connector may pass through an attic or roof
cemented in place with refractory cement.
Wall Pass-throughs
Occasionally it is necessary to pass the chimney connector
through a combustible wall to reach the chimney. Depending
on your local building codes, and the pertinent provincial or
national codes, there are several choices for accomplishing
this safely. Before beginning your installation, contact local
officials, and also the chimney connector and chimney
manufacturer for specic requirements.
Canada. Three methods are approved by the Canadian
Standards Association. The diagram on the next page shows
one method requiring an 18"(450 mm) air space between the
connector and the wall. It allows use of one or two covers
as described in the diagram. The two other methods are
described in detail in the current issue of CAN/CSA B365,
the national standard.
United States In the U.S., the national code is NFPA 211.
While many localities adopt this standard, be sure to check
with local authorities before beginning your installation.
The NFPA (National Fire Protection Agency) permits four
methods for passing through a combustible wall. A commonly
used method to pass through a wall directly to a masonry
chimney is to clear a minimum 12"(300 mm) around the
entire chimney connector, and ll it with brick masonry which
is at least 3.5"(90 mm) thick. A reclay liner, minimum 3/8"
(9 mm) wall thickness must run through the brick wall to the
chimney liner (but not beyond the inner surface of the liner).
It must be cemented in place with refractory cement. This
method is illustrated on the next page. For details on the
other three options, refer to the most recent edition of the
NFPA 211 code.