3"
47
DM 54 Chimney System: Offset Block
DM 54 Offset Chimney Block:
For vertical DM 54 chimney to bypass overhead obstructions,
the Isokern offset chimney block is used. Offset blocks are six inch
(6”) thick, single module chimney components, measuring twenty-one
and one-half inch (21-1/2”) wide by twenty-five inches (25”) long. The
fourteen inch hole passes through the block at thirty (30°) degrees.
An offset chimney block can be set as the first flue component on top of
the MAGNUM smoke dome.
When building offset sequences it is necessary to support the
third offset block in the sequence and every third offset block thereafter.
When using only one or two offset blocks no additional support is
required.
Offset sequences are best when built as low as possible in the
chimney run to maximize performance.
Do not make support columns of brick, stone or wood. All support
columns must bear onto proper noncombustible foundations.
Isokern Offset Chimney Block Installation:
Isokern offset chimney blocks are stacked in a stair step
fashion with each successive block overhanging the previous offset
block by three inches (3”), allowing the flue to rise at an angle of thirty
(30°) degrees off of vertical. (Figure 94)
When building offset sequences check the interior flue
alignment as each offset block is set to avoid creating overhanging
ledges on the inside of the flue. Such internal overhangs will inhibit
flue drafting.
Each offset block is to be set fully in a bed of Earthcore Mortar,
completely sealing each offset block to the underlying component.
Offset chimney block sequences can be built to shift the
chimney run to the left, right or to the rear of the firebox/smoke dome
assembly.
Offset blocks can be set in a spiraling rotation, thus moving
the chimney to a point that is diagonally away from its starting point.
Offsets to the Left or Right:
When offsetting chimneys to the left or right of the firebox it is not
possible to build a support column directly under the third offset block.
To create proper support, construct a support column against
the firebox from bearing up to the level of the smoke dome. Bridge from
the column over to bearing on the smoke dome with two pieces of four
inch (4”) by four inch (4”) by five-eighths inch (5/8”) steel angle.
(Figure 95)
On the steel angles build a masonry or steel support column up
to the underside of the third offset block in the sequence. (Figure 95)
NOTE:
For offset chimney block sequences that clear the side
wall of the firebox below, it is allowable to support the first offset
block that clears the the firebox side wall and then to proceed with
supports at each third offset block thereafter. (Figure 96)
FIGURE 94
FIGURE 95
FIGURE 96
