Specification

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Venting
Basement
window well
How to determine total equivalent feet
1. Determine the total equivalent feet for each type of fitting
used in the venting system from Tables 1 and 2.
2. Calculate the total feet for the straight lengths of pipe.
3. Add the equivalent feet of the fittings to the total amount
of feet of straight length pipe. This will approximate the
total equivalent feet of the vent system.
4. Find your total equivalent feet in Table 3 to determine
the proper model for your installation.
Example: System Pipe Size= 6"
Step 1 2-90° Elbows (6")= 22 Ft.
Step 2 10-2 Ft. Lengths of 6" Pipe = 20 Ft.
Step 3 6" to 4" reducer= 4 Ft.
Step 4 Total Equivalent Feet= 22 Ft. + 20 Ft. + 4 Ft. = 46 Ft.
Equivalent Feet for Vent Pipe Fittings
VENT PIPE
FITTINGS
VENT PIPE DIAMETER
4" 5" 6" 7"
Tee
25 31 38 44
Y-Connection
13 16 20 23
90° Elbow
7 9 11 12
45° Elbow
4 4 5 6
Table 1
Table 3
Sizing The Vent Riser (Use Maximum GPH Input)
MODEL
MAX*
OIL GPH
INPUT
100psi
MAX*
OIL GPH
INPUT
140psi
MAX*
GAS
BTU/hr.
INPUT
Maximum Equivalent Feet of
Vent Pipe
COMBUSTION
AIR OPTION
VENT
PIPE SIZE
AT MAX
GPH INPUT
AT 60% OF
MAX
GPH INPUT
CV-4VR
1.10 .90 170,000
18 83
yes**
4"
48 100 5"
100 100 6"
100 100 7"
CV-5VR
1.85 1.55 290,000
- 25
yes**
4"
32 81 5"
76 100 6"
100 100 7"
Table 2
Equivalent Feet for a Reducer/Increaser
PIPE SIZE
Small
4" 5"
Large
4" 0 -
5" 2 0
6" 4 2
7" 5 4
To estimate the equivalent foot length of the
Reducer/Increaser chart, find the figure at
the intersection of the small pipe size and the
large pipe size.
* Select vent riser according to the actual rated maximum GPH input. ComboVent GPH ratings
at 100 psi. Do not exceed maximum oil GPH input. For multiple venting system applications
add the input for each. Unit sizing may vary depending on specific application. Consult your
dealer or factory representative for the proper sizing for your particular application.
** Do not use combustion air intake when using gas.
Note: In Table 3, the maximum equivalent footage allowable for the vent pipe is given for
two points, the maximum GPH venting capacity and at 60% of the maximum. This allows for
estimating values between the two given points.
Calculating Equivalent Feet of a Vent System
Sizing the Vent Riser
Vent Riser
™