12
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 34 ). 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 35 ). Example: If C1 = 10' then C2 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 36 ).
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 (Figure 37 ). 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'.
Return elbow support straps must be se- curely attached under tension (in shear) to structural framing members above. Do not substitute a
OFFSET CALCULATIONS
Step 1. Use Offset Chart to determine amount of horizontal offset (A) and height (B) for vari- ous 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.
Step 3. Use Elevation Chart as job estimator only. Add necessary firestop spacers and stabi- lizers as required. Firestop spacers must be used as shown in Figures 21 and 22 and stabi- lizers as shown in Figure 26.
A1
Return
Elbow
20'
Max.
B1
Stabilizer
10' Max.
Offset
Elbow
Figure 34
NOTE: DIAGRAMS & ILLUSTRATIONS NOT TO SCALE.
A2
C2
A1
C1
Figure 35
A2
C2
A1
C1
B2
B1
B2
B1
