7'6"
A
B
•
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 19.
Example: According to the vent graph (page 16) 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 20 and 21,
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 22.
Figure 21 - Maximum Vent Run with Elbows
Figure 20 - Horizontal Run Reduction
Figure 22 - Maximum Elbow Usage
VENT INSTALLATION
90°
A + B = 17' Maximum
90° Elbow = 3'
1 + 2 + 3 + 4 = 270°
1
2
3
1
2
3
4
7'6"
10'
7'
A
B
HORIZONTAL TERMINATION CONFIGURATION —
RIGID VENTING
(Continued)
Example:
Elbow 1 = 90
°
Elbow 2 = 45
°
Elbow 3 = 45
°
Elbow 4 = 90
°
Total Angular Variation
= 270
°
20
21
