Vent Length Requirements; Maximum Vent/Air Intake Pipe Length - Horizontal; Maximum Allowable Vent Length - Horizontal; Flashing And Storm Collar Installation - Viessmann Vitocrossal 300 CU3A Installation Instructions Manual

CU3A Venting Systems Installation

Vent Length Requirements

IMPORTANT
Always include vent termination length in calculations.
Note: For combination of different vent/air intake pipe
diameters, such as Ø 4 in. stainless steel vent with
Ø 3 in. (CVPC, PVC, ABS) air intake pipe, the
total equivalent length must be used for the smaller
pipe diameter.
Minimum vent length is 3.3 ft. (1 m).
Legend
a Equivalent vent length (exhaust)
b Equivalent vent length (air intake)
c Min. 6 in. (152 mm)
d Min. 2 in. (50 mm)

Maximum vent/air intake pipe length - horizontal

The total equivalent length specified for a two pipe system
consisting of stainless steel, CPVC or PP(s) is the total
combined length of the exhaust vent and air intake pipe
system.
Do not exceed these maximum lengths.
All PP(s) vent material and air intake (if PP(s) used) must
be ULC S636 or UL1738 listed.
IMPORTANT
For PP(s) systems, all exhaust vent and air intake piping
and elbows exposed outside, must be UV resistant
polypropylene (supplied by the vent manufacturer).
Maximum equivalent length - horizontal
Flue
Boiler model
Air
CU3A 26, 35
CU3A 45, 57
A 7% boiler input reduction @ 60 m for all sizes and all
configurations.

Flashing and storm collar installation

Flashings and storm collars are field supplied.
Flashings and storm collars suitable for Type B vent
materials (or better) may be used.
To obtain flashings and storm collars, please contact
your local vent material supplier. Follow the installation
instructions supplied by the special venting manufacturer.
Follow local codes to properly isolate the exhaust vent
pipe when passing through floors, ceiling and roof.
Always check the marking on the pipe to make sure you
are using the correct material.
Direct Venting (Two-pipe System)
Intake Ø Exhaust Ø
3 in. 3 in.
(80 mm) (80 mm)
3 in. 4 in.
(80 mm) (110 mm)
Equivalent
length
198 ft.
(60 m)
198 ft.
(60 m)
35