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' (6.1 m) in total length between elbows (see Figure 36 ). If sections of pipe exceed 10' (3 m) between elbows, a chimney stabilizer must be used at the midpoint. The stabilizer support straps must be attached under tension (in shear) to structural framing members above. When two sets of offset elbows are used, the maximum combined length of chimney used between elbows cannot exceed 20' (6.1 m) (see Figures 37 and 38 ). Example: If C1 = 10' (3m) then C2 cannot exceed 10' (3 m).

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 mental screw located at the underside of the joint (Figure 39 ).

 

 

 

 

 

 

 

 

 

Joints

Chimney

 

 

 

 

 

4'

Required

at

6'

 

 

 

 

 

Past

Section

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Screws

Joint

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Offset

Every

 

 

No. 8 x ¹⁄₂" SMS

 

 

Required 6'

in

 

 

 

 

 

 

 

 

 

 

 

 

 

 

6'

 

of

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

First

 

 

 

 

 

 

 

 

 

Screws

for

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

No

Joints

 

 

 

 

 

 

 

 

 

 

Figure 39

A ¹⁄₈" (3 mm) diameter hole must be drilled in the chimney joint using a ¹⁄₈" (3 mm) diameter drill. Hole should be drilled in center of joint overlap (Figure 40 ). Be sure to drill only through the outer chimney casting. Do not puncture the inner flue.

Underside of Chimney

Figure 40

Maximum offset of the chimney system is 30° . Two offset elbows 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 system exceeds 22' (5.6 m).

Return elbow support straps must be securely attached under tension (in shear) to structural framing members above.

OFFSET CALCULATIONS

1.Use Offset Chart to determine amount of horizontal offset (A) and height (B) for various chimney sections.

2.Use “Height of Chimney Only” column to determine combinations of pipe used above return elbow to achieve desired heights. Refer- ence Components Effective Height Chart in vertical elevation chart section.

3.Use Elevation Chart as job estimator only. Add necessary firestop spacers and stabilizers as required. Firestop spacers must be used as shown in Figures 20 and 21 and stabilizers as shown in Figure 25.

INSTALLING OFFSETS

First, review Offset Elevation Chart and Figure 35 on page 14 for reference.

Step 1. Determine the offset distance where chimney is to pass through the first ceiling- dimension “A.” To find this point on your ceil- ing, first determine the center point for a vertical chimney following the instructions for vertical installation.

Measure height to the ceiling from the top of fireplace-dimension “B.” Use Offset Elevation Chart to find dimension “A.” Mark point where you will drive your nail to show the center point for your offset ceiling cut.

Step 2. Proceed by using the Straight Up Installation Instructions for cutting and framing ceiling and roof openings.

Note: See “Framing and Dimension” Chart for the sizes of the ceiling and roof openings. The size of the roof opening varies with the degree of pitch of the roof.

NOTE: DIAGRAMS & ILLUSTRATIONS NOT TO SCALE.

OFFSET ELBOW ASSEMBLY

Offset elbows install the same as chimney sections. First, snap the inner section INTO the preceding inner section of flue. Check connection by pulling up slightly to ensure a tight fit. Next, the outer sections snap locks OVER the preceding outer section of chimney. Again, check outer section by pulling up slightly to ensure proper connection is made.

RETURN ELBOW ASSEMBLY

Return elbows install the same way as round terminations and stabilizers:

Step 1. Hold return elbow over top of last chimney section.

Step 2. Center inner slip section into inner flue pipe-slip down.

Step 3. Center outer locking section over outer chimney pipe-push down until locking joint has firmly engaged.

Step 4. Pull up slightly on return elbow to ensure locking joint has firmly engaged.

Step 5. Secure support straps to framing members by nailing under tension in sheer (Figure 41 ).

Return Elbow

Figure 41

Note: The return elbow assembly performs the same function as a stabilizer. Consider this when determining the need for a stabilizer.

Note: Do not apply excessive pressure to any subsequent chimney section following return elbow assembly when installing. Ensure subsequent chimney sections are securely attached by testing as noted above.

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