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W415-0153 / A / 10.29.01
HORIZONTAL RUN NOT TO EXCEED VERTICAL RISE
SPECIAL INSTALLATION EXAMPLE
When a horizontal offset is required in a through-the-roof
installation, the following procedure for vent length calcula-
tions must be followed:
In an installation as shown in FIGURE 7,
lengths A and C are known based on
room height and roof requirements.
Length C must never be less than 29
inches. Any 90° and 45° elbows must
be calculated as 5 feet of venting
each.
The allowable horizontal run can be cal-
culated using these parameters. In this
example, the total vertical height is 20
feet (length "A" is required to be 11 feet
while length "C" needs to be 9 feet). The
maximum vertical length is 40 feet and
all runs and elbows must be subtracted
from this maximum vertical length.
The maximum allowable horizontal run that "B" can be is:
40 ft. (maximum vertical run length)
-11 ft. (through the roof vertical rise "A")
-10 ft. (2 - 90° elbow)
- 9 ft. (vertical run "C")
10 ft. (maximum allowable horizontal length for "B")
The length of "B" must never be greater than the length
of "A" and "C" combined.
OFFSET INSTALLATION EXAMPLE
FIGS 5
FIGURE 4
If a first run of 72 inches is re-
quired, using the "First Vent Run"
on the chart shows that a maxi-
mum second run of 48 inches
is allowable.
IF NECESSARY, THE FIRST
RUN AND THE SECOND
RUN MAY BE REVERSED.
REQUIRED
VERTICAL
RISE FROM
FIREPLACE
TO FIRST EL-
BOW IN
INCHES
FIGURE 6
CALCULATED HORIZONTAL VENT RUN IN FEET
For optimum flame appearance and stove performance,
keep the vent length and number of elbows to a minimum.
The air terminal must remain unobstructed at all times.
Examine the air terminal at least once a year to verify that it
is unobstructed and undamaged.
The maximum horizontal run is 34 inches with a 90° elbow
located 29" above the stove. FIGURE 4.
The maximum horizontal run with a 57 inch vertical rise
immediately above the stove is 20 feet . Figures 5.
If vertical rises greater than 57 inches are necessary,
the increased rise must be deducted from the maxi-
mum horizontal run.
Use chart, Figure 6, to calculate horizontal runs for vertical
rises between 29 and 57 inches.
When calculating maximum run lengths, include 10 feet
for each 90° elbow or 5 feet for each 45° elbow.
Do not include the first elbow directly off the unit.
FIGURE 8
57"
first run
72"
second run
48"
FIGURE 9
C
B
A
FIGURE 7