Vent Length; Equivalent Vent Length Calculation Example - Viessmann Vitodens 200-W WB2B Series Installation Instructions Manual

Vitodens Rigid and Flex Venting Systems Installation
Venting Length
Equivalent vent length calculation
Legend
A 87º elbow
B Vent pipe 3.3 ft. (1 m)
C Vent pipe 1.6 ft. (0.5 m)
D Vent termination
* 4 First elbow not included in equivalent vent calculation.

Equivalent vent length calculation example

2 x 87º elbow...........................................3.2 ft. (1 m)
2 x vent pipe (1 m)....................................6.6 ft. (2 m)
1 x vent pipe (0.5 m)..............................1.6 ft. (0.5 m)
1 x vent termination................................2.4 ft. (0.73 m)
.
Total equivalent length...........................13.8 ft. (4.23 m)
IMPORTANT
First elbow is excluded from in equivalent vent calculation.
Always include vent termination length in calculations.
Note: Depending on the selected vent manufacturer,
a service clearance of 36 in. may be required.
Consult the vent manufacturer if using two-pipe
to coaxial adaptor directly at the back of the boiler.
(continued)
Side Wall Vent Installation (Coaxial)
Do not exceed the maximum vent length.

First 87º elbow on boiler is not included in equivalent

vent length calculation.
Type of fitting
87º elbow/
87º inspection tee
45º elbow
A 10% boiler input reduction @ 99 ft. (30 m) for all sizes
and all configurations.
Equivalent length
1.6 ft. (0.5 m)
1 ft. (0.3 m)
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