Special Offset Instructions; Offset Calculations - Lennox Hearth Products OASIS SERIES LSO-43 Installation Instructions Manual

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
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
metal screw located at the underside of the
joint ( Figure 35 ).
A " diameter hole must be drilled in the
chimney joint using a
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'.
12
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
= 10' then C cannot
used as shown in Figures 20 and 21 and
1 2
stabilizers as shown in Figure 25 .
" sheet
" diameter drill. Hole
B
1
Figure 33
NOTE: DIAGRAMS & ILLUSTRATIONS NOT TO SCALE.
A
1
Return
Elbow
20'
Max.
Stabilizer
10'
Max.
Offset
Elbow
A
2
C
2
A
1
C
1
A
2
C
2
B
2
A
1
B
1
C
1
Figure 34
Chimney
Section
4'
6'
Figure 35
B
2
B
1
Joints
No. 8 x " SMS