Installation guide

Single Wall Venting (Room Air Dependent)
78
Vent Length Requirements (continued)
Maximum vent pipe length - vertical
Size the exhaust vent pipe as specified
in table 51 This table lists the
maximum allowable vent length in feet
and meters of the exhaust piping. Vent
diameter must not be reduced at any
point in the installation.
Table 51. Maximum allowable equivalent length - vertical
Boiler Model
System Ø Max. equivalent
vent length “a”
*3
HWB1B 10-26, 10-35 2” / 51mm
*1
3” / 76mm
4” / 102mm
*2
86ft. / 31m
164ft. / 50m
200ft. / 61m
HWB2B 9-19, 9-26, 9-35 2” / 51mm
*1
3” / 76mm
4” / 102mm
*2
115ft. / 35m
148ft. / 45m
180ft. / 55m
HWB2B 17-45, 17-60 3” / 76mm
4” / 102mm
98ft. / 30m
148ft. / 45m
HWB2B 30-80, 30-105 4” / 102mm 131ft. / 40m
*1
2” diameter system o nly available with CPVC system
*2
4” (3” to 4” increaser field supplied. Do not order Viessmann 3” or 4”
starter adaptor).
*3
See figure 72
Maximum of five 90° elbows allowed in the vent system (first 90º elbow is not included)
(see fig. 73).
Minimum vent length is 3.3 ft. / 1m.
Legend
Exhaust (straight coupling) with
screen
Flashings
Support system
Combustion air intake (left, right or
through co-axial opening),remove
and discard air intake cover
(WB1B 10-26/35 and
WB2B 9-19/26/35)
E Combustion air opening
a Equivalent length (exhaust)
b min. 18” / 457mm
max. 48” / 1219mm
5368 815 v2.0 b
Fig. 72
a
b
E