M400BFC Balanced Flue
| Chimney Centerline |
| Actual Center- |
| point |
| 8 6M" |
| (222mm) |
| Plumb Line |
| Plumb Bob |
| Imaginary Center- |
| point |
| FPC556a |
Fig. 9 | Locate centerline of chimney with plumb line. |
Offset Installation
In order to clear an obstruction, it may be necessary to offset chimney from vertical. This is accomplished by using elbows. Use the 30° Offset Elbow table on Page 5 to determine proper offset and parts required.
Each offset requires two (2) elbows. The second elbow is equipped with support straps. It is very important to install the second elbow in each offset as close to the ceiling or support as possible so that the elbow straps can be secured to framing members to help support the weight of the chimney.
Determine offset distance of your chimney arrangement from centerline of fireplace to centerline of chimney where it is to pass through ceiling.
Locate center point of the chimney on ceiling as though a straight up chimney arrangement is to be used. Mea- sure your offset dimension from straight up chimney center point on ceiling.
Ceiling Chimney Hole/
Possible Obstructions
The size of the hole in ceiling will vary with the angle at which the chimney passes through ceiling.
Drive a nail up through ceiling at marked chimney cen- ter point. Go to floor above and see where hole will be cut. Check to see where existing ceiling joists and other possible obstructions are located...i.e. wiring, plumbing etc... If necessary,
to avoid obstructions.
Cutting the Hole
Cover fireplace collar opening and cut proper sized chimney hole in chimney.
Framing the Ceiling Hole
Frame the ceiling chimney hole as shown in Figure
10.It is good practice to use framing lumber that is the same size as the ceiling joists; this is a requirement at attic level.
Existing |
| 17¹⁄₂” |
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| |
Ceiling |
|
| 17¹⁄₂” |
| |
Joists |
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| (445mm) |
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| (445mm) |
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| Chimney |
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| Hole |
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| New |
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| Framing |
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| Members |
| Ceiling | FP551b |
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Fig. 10 | Typical frame for ceiling chimney hole. |
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The following table gives firestop spacer model num- bers:
Chimney Hole Size
| Angle of Chimney |
| |
| at Ceiling | ||
Size of Chimney | Vertical | 30° |
|
| FS2A | FS6A | |
8” Flue | 17¹⁄₂” x 17¹⁄₂” | 17⁷⁄₈” x 29⁵⁄₈” | |
| (445 x 445mm) | (454 x 753mm) | |
Fig. 11 Ceiling chimney hole sizes necessary for installing firestop spacer.
The inside dimension of the frame must be the same as the hole size selected from Figure 11 in order to provide required the 2” (51mm) air space between the outside diameter of the chimney and the edges of the
framed ceiling hole.
10 | 87D1505 |