Vermont Casting DVRSR - Manual (Page 11)

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Fig. 17
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
system.
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. 18. This does not apply if the 90
degree elbows are used to increase or redi-
rect a vertical rise.
Example: According to the vent chart the maximum
horizontal vent length is 20 ft.when the vertical height is 8
ft. from fireplace base height. If one 90 degree elbow is
required in the horizontal vent it must be reduced to 17 ft.
120"
3048mm
90º elbow=3'
7'
90"
2286mm
84"
2134mm
Fig. 16 SIDE VIEW Fig. 15
When one 90º elbow is installed directly onto another off
the back of the fireplace the maximum horizontal vent
length is 36" (914mm). Fig. 16.
VERTICAL SIDEWALL APPLICATIONS
The maximum number of 90 degree elbows per side wall
installation is four (4), (includes 7DVRT90 off back of unit)
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 number of elbow degrees in a system is
270º. (This does not include transition elbow from rear
vent to vertical vent).
Fig. 15
Sample: 1 - 90º
2 - 45º
3 - 45º
4 - 90º
Total - 270º