OFFSET INSTALLATIONS
RULES GOVERNING OFFSET INSTALLATIONS
Sometimes it is necessary to use elbows to create an
inclined run of pipe (offset installation) that will make
installation easier by avoiding plumbing, wiring or other
obstructions. The following rules apply to offset installations.
A. 60' maximum system height.
B. Four 30° elbows (two pairs) maximum per system. Each
offset elbow must be used with a return elbow. The
chimney pipe must be vertical when it penetrates the
roof.
C. The chimney offset is to be a maximum of 30° from
vertical.
D. Maximum inclined chimney run of 20'.
E. Additional support is to be provided every 6' of inclined
run of chimney. Use flue support 8204S.
F. Minimum height of fireplace using two elbows (one pair)
is 13'6"; four elbows (two pairs) is 21'.
G. Elbows may be used directly off the top of the firebox and
may be mounted with the return elbow directly on top of
the offset elbow.
H. A MINIMUM OF 1" AIR SPACE CLEARANCE MUST BE
MAINTAINED FROM THE CHIMNEY PIPE AND ELBOWS
TO ALL COMBUSTIBLES.
I. Local building codes must be followed in all cases as to
the particular requirements concerning the installation of
factory built fireplaces.
TO INSTALL ELBOWS
1. Place the offset elbow (no straps) on top of the firebox or
chimney section and point the upper half in the direction
you require the chimney to incline. Snap lock all sections
permanently in place.
2. Adjust the inner section of the elbow into the inside of the
inner collar of the firebox or the inner section of the
chimney pipe.
3. Adjust the outer section of the elbow over the outer
section of the flue collar or outer section of the chimney
pipe. Snaplock all sections permanently into place.
4. The return elbow has 18" support straps. The support
straps should be nailed to the framing in the manner
indicated in figure 16. It may be necessary to add framing
or lengthen the straps with hanger iron to support
chimney pipe and elbows.
5. See figure 18 for offset calculation: Locate the center
point of the flue on the ceiling with a plumb bob as shown
on page 5. The center of the correct location for the
ceiling opening will be the amount of the offset dimension
away from the ceiling nail. See figure 18. The "X" dimen-
sion in the drawing is the amount of the offset. Be sure to
consider the direction that your offset will incline. To
achieve the minimum offset, (see table), attach the return
elbow to the first elbow. To achieve further offset, you
may install various lengths of pipe between the elbows to
a maximum length of 72 inches without a flue support.
6. When the flue penetrates the ceiling at a 30° angle,
install firestop spacer 8230F. (See step 7 on page 8 for
construction detail.)
Figure 14
CHIMNEY TERMINATION
HEIGHT 10 FOOT RULE OF
THUMB
Under most conditions the fireplace system will draw
properly if the chimney height is determined in
accordance with the following guidelines:
1. If your chimney penetrates the roof within 10' of its
peak, it must extend at least 24" above your roof's
peak and be at least 36" above the highest point of
the roof opening (see figure 15).
2. If the chimney penetrates the roof farther than 10'
from its peak, measure from the center line of the
chimney to a point 10' away, between the chimney
and the peak of the roof. The top of the chimney
must be at least 24" above this point and at least 36"
above the highest point of the roof opening. (See
figure 16).
3. When figuring required chimney height, the termina-
tion counts as 6" of effective chimney height. The
balance of the required height will consist of chimney
sections and the effective height of the firebox.
4. The 10' Rule of Thumb is a guide for calculating
chimney height that works under most conditions.
However, many factors can cause the need for
additional chimney height beyond what the 10' Rule
of Thumb would indicate. Topographical factors can
cause high pressure zones which prevent a chimney
from drawing. This can occur if the house is located
in a low lying area, in a valley or near the base of a
cliff or hillside. The same situation can occur it the
chimney is near other steep roof lines or tall build-
ings. Areas with high winds also frequently require
higher than normal chimneys. Certain styles of
architecture tend to interfere with a fireplace's proper
draw. If the room in which the fireplace is located
has a very high ceiling, smoke may enter the room
unless the chimney is terminated at a level higher
Figure 15
Figure 16
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