Viessmann Vitocrossal 300 CU3A Installation Instructions Manual page 39

CU3A Venting Systems Installation
Vent Length Requirements
Legend
A Vent adaptor 110 to 100 mm (if required)
B Increaser 80 to 100 mm (if required) field supplied
C Adaptor (if required)
D Short vent length 1.6 ft. (0.5 m)
E Elbow 90°
F Long vent length 3.3 ft. (1 m)
G Coaxial adaptor (supplied by vent manufacturer)
H Horizontal coaxial termination
I Vertical coaxial termination
J Bird screen
IMPORTANT
Always include vent termination length in calculations.
Equivalent vent length calculation example
(Vitocrossal 300 CU3A 26/35 systems diameter 3 in.)
2 x 90º stainless steel elbow....................6 ft. (1.83 m)
2 x 45º stainless steel elbow....................4 ft. (1.22 m)
Air intake pipe
1 x 90º plastic (ABS/CPVC/PVC) elbow.....5 ft. (1.52 m)
1 x 45º plastic (ABS/CPVC/PVC) elbow.....3 ft. (0.91 m)
Exhaust vent pipe..................................10 ft. (3.05 m)
Air intake pipe.......................................10 ft. (3.05 m)
Combined total equivalent vent length
(a+b)...................................................38 ft. (11.58 m)
(continued)
Two pipe system with coaxial termination only
Standard long sweep elbows
Material
Stainless steel
CPVC, ABS, PVC
plastic pipe
PP(s)
Standard long sweep elbows (for CPVC pipe only)
Note: If standard sweep elbows are used the allowable
vent lengths are reduced. One standard 90° elbow
is equivalent to 8 ft. (2.4 m) of straight pipe.
Long sweep elbows are recommended for use
with venting system.
Maximum equivalent length -
vertical exhaust / horizontal air intake (hybrid)
Boiler model
CU3A 26, 35
CU3A 45, 57
A 7% boiler input reduction @ 60 m for all sizes and all
configurations.
Direct Venting (Two-pipe System)
90° elbow 45° elbow
equivalent equivalent
length length
ft. (m) ft. (m)
3 (0.91) 2 (0.61)
5 (1.52) 3 (0.91)
- 1 (0.30)
Intake Ø Exhaust Ø
3 in. 3 in.
(80 mm) (80 mm)
3 in. 4 in.
(80 mm) (110 mm)
87° elbow
/ inspection
tee
ft. (m)
-
-
1.6 (0.50)
Equivalent
length
198 ft.
(60 m)
198 ft.
(60 m)
39