Lennox Hearth LSO-43 installation instructions Special Offset Instructions, Offset Calculations

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 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 35 ).

A¹⁄₈" 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.

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.

A1

Return

Elbow

20'

Max.

B1

Stabilizer

10'

A2

C2

A1

C1

A2

C2

B2

A1

B1

C1

B2

B1

12

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'.

Max.

Offset

Elbow

Figure 33

NOTE: DIAGRAMS & ILLUSTRATIONS NOT TO SCALE.

Figure 34

									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 35