Lennox Hearth OASIS SERIES LSO-43 - Manual (Page 12)

NOTE: DIAGRAMS & ILLUSTRATIONS NOT TO SCALE. 12
Figure 34
Figure 35
Return elbow support straps must be securely
attached under tension (in shear) to structural
framing members above. Do not substitute a
FTF10-30 offset elbow in place of a FTF10-E30
return elbow.
OFFSET CALCULATIONS
Step 1. Use Offset Chart to determine amount
of horizontal offset (A) and height (B) for
various chimney section assemblies.
Step 2. Use “Height of Chimney Only” column
in The Vertical Elevation Chart to determine
combinations of chimney used above return
elbow to achieve desired heights. Reference
Components Effective Height Chart in vertical
elevation chart section on page 13.
Step 3. Use Elevation Chart as job estimator
only. Add necessary firestop spacers and sta-
bilizers as required. Firestop spacers must be
used as shown in
Figures 20 and 21 and
stabilizers as shown in Figure 25.
SPECIAL OFFSET INSTRUCTIONS
To clear any overhead obstructions, you may
offset your chimney system using Security's
30
°
offset and return elbows. Use two elbows
- an offset elbow to initiate the offset and a
return elbow to terminate it. A 30
° offset
elbow, angling in any direction, may be the
first component used off the top of the fire-
place flue collar.
The offset and return elbows may be attached
together, or a section or sections of chimney
may be used between, but do not exceed 20' in
total length between elbows. If sections of pipe
exceed 10' between elbows, a chimney stabi-
lizer must be used at the midpoint (
Figure 33 ).
The stabilizer support straps must be attached
under tension (in shear) to structural framing
members above. When two sets of elbows are
used, the maximum combined length of chim-
ney used between elbows cannot exceed 20'
(
Figure 34 ). Example: If C
1
= 10' then C
2
cannot
exceed 10'.
If an offset exceeds 6' in length, each chimney
joint beyond the first 6' of offset to the return
elbow, must be secured by a No. 8 x
¹⁄₂" sheet
metal screw located at the underside of the
joint (
Figure 35 ).
A ¹⁄₈" diameter hole must be drilled in the
chimney joint using a ¹⁄₈" diameter drill. Hole
should be drilled in center of joint overlap ( see
Figure 36 ). Be sure to drill only through the
outer chimney casting. Do not puncture the
inner flue.
Maximum offset of chimney system is 30 ° .
Two offsets must not be assembled to form a
60
°
offset. However, two sets of offset and
return elbows may be used on a single flue
system, provided the total height of the sys-
tem exceeds 25'.
Figure 33
Stabilizer
A
1
20'
Max.
B
1
10'
Max.
Offset
Elbow
Return
Elbow
A
1
C
1
B
1
B
2
C
2
A
2
A
1
C
1
B
1
B
2
C
2
A
2
Chimney
Section
Joints
No. 8 x ¹⁄₂" SMS
Screws Required at
Ever
y Joint Past 6'
No Screws Required in
Joints for First 6' of Offset
4'
6'