Lennox Hearth LBR-4324-H, LBC-4324-H, LBR-3824 Special Offset Instructions, Offset Calculations

3.The effective heights of the components are:

The Fireplace	=	48-3/8"
FTF10-12	=	10-1/4"
FTF10-18	=	16-1/4"
FTF10-36	=	34-1/4"
FTF10-CTDTM Termination	=	13"
FTF10-CT1 Termination	=	12" to 18"
FTF10-CT2 Termination	=	15" to 23"
FTF10-S4 Stabilizer *	=	3"*

*Required for every 30' of vertical chimney and/or 10' of offset chimney.

4.Determine amount of chimney height re- quired by subtracting total combined height of all pre-selected components (fireplace and chimney components from total desired height.)

Reference Vertical Elevation Chart and deter- mine the number of chimney sections (quantity and length) required.

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, an- gling in any direction, may be the first compo- nent used off the top of the fireplace flue collar.

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 40 ). 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 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 23 and 24 and

A2

C2

A1

C1

A2

C2

B2

A1

B1

C1

B2

B1

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 stabilizer must be used at the midpoint (Figure 37 ). 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 chimney used between elbows can- not exceed 20' (Figure 38 ). 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 39 ).

stabilizers as shown in Figure 29.

A1

Return

Elbow

20'

Max.

B1

Stabilizer

10' Max.

Offset

Elbow

Figure 37

Figure 38

									Joints
Chimney						4'	Required		At	6'
									Past
Section
						Screws		Joint
						Offset	Every
		Required 6'		In	of			No. 8 x 1/2" SMS
	6'
			First
	Screws	For
No	Joints

Figure 39

12

NOTE: DIAGRAMS & ILLUSTRATIONS NOT TO SCALE.