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18 73D0024
VERTICAL/HORIZONTAL TERMINATION
CONFIGURATIONS (continued)
• If a 90° elbow is used in the horizontal vent run (level height
maintained) the horizontal vent length is reduced by 36".
See Figures 11 and 12, page 17. This does not apply if the
90° elbows are used to increase or redirect a vertical rise.
See Figure 14.
Example: According to the vent graph (page 16) the
maximum horizontal vent length in a system with a 10'
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 13 and 14 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 15.
Figure 14 - Maximum Vent Run with Elbows
Example: Elbow 1 = 90°
Elbow 2 = 45°
Elbow 3 = 45°
Elbow 4 = 90°
Total Angular Variation = 270°
Figure 13 - Horizontal Run Reduction
Figure 15 - Maximum Elbow Usage
VENT INSTALLATION
90°
A + B = 17' Maximum
90° Elbow = 3'
1 + 2 + 3 + 4 = 270°
1
2
3
4
10'
AB
10'
10'
7'
A
B
24" Min.