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HORIzONTAL (THROUGH-THE-WALL)
TERMINATION CONFIGURATION (Continued)
• If a 90° elbow is used in the horizontal vent run (level height
maintained) the horizontal vent length is reduced by 36"
(914 mm) (Fig. 21 A and B) This does not apply if the 90°
elbows are used to increase or redirect a vertical rise. See
Figure 24.
Example: According to the vent graph (page 17) the
maximum horizontal vent length in a system with a 7.5'
vertical rise is 20' (6m) and if a 90° elbow is required in
the horizontal vent it must be reduced to 17' (5.2 m).
In Figures 23 and 24, Dimension A plus B must not be greater
than 17' (5.2m).
• The maximum number of 45° elbows permitted per side
wall installation is two (2). These elbows can be installed
in either the vertical or horizontal run.
• For each 45° elbow installed in the horizontal run, the length
of the horizontal run MUST be reduced by 18" (45cm). This
does not apply if the 45° elbows are installed on the vertical
part of the vent system.
• The maximum number of elbow degrees in a system is 270°.
See Figure 25.
A
10'
Horizontal 90° Elbow = 3' Reduction
7'6"
A + B = 17' Maximum
Figure 24 - Maximum Vent Run with Elbows
56D3049
Figure 23 - Horizontal Run Reduction
Example:
Total Angular Variation =
B
7'
1
3
4
1 + 2 + 3 + 4 = 270°
Figure 25 - Maximum Elbow Usage
VENT INSTALLATION
90°
A
B
7'6"
Elbow 1 =
90°
Elbow 2 =
45°
Elbow 3 =
45°
Elbow 4 =
90°
270°
1
3
4
1
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