The maximum number of 90 degree elbows per side wall installation is three (3).
The maximum number of 45 degree elbows permitted per side wall installation is two (2). These elbows can be installed in either the vertical or horizontal run.
The maximum horizontal vent length is 36" (914mm) when 90º elbow is installed directly onto fireplace.
3FT (92cm)
Fig. 36
For each 45 degree elbow installed in the horizontal run (while maintaining a constant horizontal plane), the length of the horizontal run MUST be reduced by 18" (457mm). This does not apply if the 45 degree elbows are installed on the vertical part of the vent sys- tem.
If a 90 degree elbow is used in the horizontal vent run (level height maintained) the maxi- mum horizontal vent length is reduced by 36 inches. Fig. 36. This does not apply if the 90 degree elbows are used to increase or redi- rect a vertical rise.
The maximum number of elbow degrees in a system is 270º.
Sample: 1 | - | 90º |
| |
2 | - | 45º |
| |
3 | - | 45º |
| |
4 | - | 90º |
| |
|
|
|
|
|
| Total |
| 270º | |
Fig. 37 |
Example: According to the vent chart the maximum horizontal vent length is 20' when the vertical height is 7.5' from fireplace base height. If one 90 degree elbow is required in the horizontal vent it must be reduced to 17'.
| 84" |
|
| 2134mm | 120" |
|
| |
|
| 3048mm |
90" | 90¼ elbow=3' | |
2286mm |
|
|
|
| Fig. 38 |
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