Installation guide

Single Wall Venting (Room Air Dependent)
77
Vent Length Requirements
Maximum vent pipe length - horizontal
Size the exhaust vent pipe as specified
in the table 50 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 50. Maximum allowable equivalent length - horizontal
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 71
Maximum of five 90° elbows allowed in the entire vent system (see fig. 73)
Minimum vent length is 3.3 ft. / 1m.
Legend
Support system
Exhaust vent termination
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)
Combustion air opening
a Equivalent vent length (exhaust)
5368 815 v2.0 b
First elbow not included in equivalent
vent calculation.
Always include vent termination length
in calculations.
IMPORTANT
Fig. 71
Exhaust vent pipe
and fittings
Field supplied
Side wall
Caulk here
(exterior caulking)
Flue starter adaptor
Flue
a
Support
System
Support
System