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Heatilator • Birmingham BIR50-B Installation Manual • 4059-701 • Rev G • 06/29/15
C. Arch / Mailbox Style Shroud
The arch or mailbox style shroud generally has two solid sides and a solid top. The exhaust openings are on the two open
ends of the arch (Figure 5.3). Table 5.2 lists the minimum shroud dimensions, the minimum open area per side, and the
minimum total open area for the shroud.
Shaded area represents screened open area. Actual
shape of shroud may vary as long as minimum dimen-
sions and minimum open area requirements are met.
H
W
L
H: Minimum height of shroud
L: Minimum length of shroud
W: Minimum width of shroud
Figure 5.3 Arch/Mailbox-Style Shroud Minimum Dimensions
Table 5.2
Arch / Mailbox Style Shroud Minimum Dimensions
Chimney
Diameter
Chimney Area Min Height H Min Length L Min Width W
Min Open Area
per side
Min Total Open
Area
in
mm
in
mm
in
mm
in
mm
in
mm
sq in
sq in
14
355.6
154
3911.6
24
609.6
32
812.8
32
812.8
520
1040
D. Pyramid Style Shroud
The pyramid style shroud is roughly square or rectangular with an open top for exhaust as well as openings along the
base of the four sides (Figure 5.4). Table 5.3 lists the minimum shroud dimensions, including the minimum height and
length of the base opening.
Shaded area represents screened open area. Actual
shape of shroud may vary as long as minimum dimen-
sions and minimum open area requirements are met.
H2
W
B
H1
L
L: Minimum length of shroud top opening
W: Minimum width of shroud top opening
H1: Minimum total height of shroud
B: Minimum length of opening along base
H2: Minimum height of opening along base
Figure 5.4 Pyramid-Style Shroud Minimum Dimensions
Table 5.3
Pyramid Style Shroud Minimum Dimensions
Chimney
Diameter
Min Height H1 Min Length L Min Width W
Min Base B
Min Height H2
in
mm
in
mm
in
mm
in
mm
in
mm
in
mm
14
355.6
24
609.6
32
812.8
32
812.8
22
558.8
2
50.8
