Napoleon STARfire GD70NT-S Installation And Operation Instructions Manual page 8

8
DEFINITIONS
for the following symbols used in the venting calcula-
tions and examples are:
> - greater than
> - equal to or greater than
< - less than
< - equal to or less than
H
- total of both horizontal vent lengths (H
T
(H ) in feet
O
H
- combined horizontal vent lengths in feet
R
H
- offset factor: .03(total degrees of offset - 90°* ) in
O
feet
V
- combined vertical vent lengths in feet
T
TOP EXIT / HORIZONTAL TERMINATION
when (H ) < (V )
T T
Simple venting configuration (only one 90° elbow)
FIGURE 6
See graph to determine the required vertical rise V
required horizontal run H
T
VERTICAL
R I S E I N
FEET
V
T
HORIZONTAL VENT RUN PLUS OFFSET IN
The shaded area within the lines represents acceptable
values for H and V .
T T
W415-0434 / D / 09.06.07
) and offsets
R
T
.
FEET
ELBOW VENT LENGTH VALUES
1°
15°
30°
45°
90°*
* the first 90° offset has a zero value and is shown in
the formula as -90°
For vent configurations requiring more than one 90° el-
bow, the following formulas apply:
Formula 1: H
Formula 2: H
Example 1:
FIGURE 7
for the
V
= 3 ft
1
V
= 8 ft
2
V = V + V
T 1 2
H
= 2.5 ft
1
H
= 2 ft
2
H = H + H
= 2.5 + 2 = 4.5 ft
R 1 2
H
= .03(three 90° elbows - 90°) = .03(270° - 90°) = 5.4 ft
O
H = H + H
T R O
H + V
= 9.9 + 11 = 20.9 ft
T T
H
Formula 1:
T
9.9 < 11
H
Formula 2:
T
20.9 < 40
Since both formulas are met, this vent configuration is ac-
ceptable.
feet inches
0.03
0.45
0.9 11.0
1.35 16.0
2.7 32.0
< V
T T
+ V < 40 feet
T T
90°
V
2
90°
H
90°
1
V
1
= 3 + 8 = 11 ft
= 4.5 + 5.4 = 9.9 ft
< V
T
+ V < 40 feet
T
0.5
6.0
H
2