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Table L: Category I Vertical Venting
* Vent lengths are based on a lateral length of 2 ft. Refer to the latest edition of the NFGC for further details.
When vertical height exceeds 25 ft, consult factory prior to installation.
** Subtract 10 ft per elbow. Max. 3 elbows.
Maximum combustion air duct length terminated at 100 equivalent ft.
load. Consult available guides for proper sizing of the
manifold and the chimney. At no time should the area
of the common vent be less than the area of the
largest heater exhaust outlet.
Common venting systems may be too large once an
existing unit is removed. At the time of removal of an
existing appliance,
the following steps must be fol-
lowed
with each appliance remaining connected to the
common venting system placed in operation, while the
other appliances remaining connected to the common
venting system are not in operation.
WARNING:
Vent connectors serving appliances
vented by natural draft shall not be connected into
any portion of mechanical draft systems operating
under a positive pressure.
CAUTION:
Vent connectors for natural draft
venting systems must be Type B or better.
1.
Seal any unused opening in the common venting
system.
2.
Visually inspect the venting system for proper size
and horizontal pitch and verify there is no block-
age, restriction, leakage, corrosion or other unsafe
condition.
3.
Insofar as is practical, close all building doors and
windows and all doors between the space in which
the appliances remaining connected to the com-
mon venting system are located and other spaces
of the building. Turn on clothes dryers and any ap-
pliance not connected to the common vent
system. Turn on any exhaust fans, such as range
hoods and bathroom exhausts, at maximum
Model
No.
Certified
Venting
Material
Vent
Size
Vertical Venting
Height*
Combustion
Air
Intake Pipe
Material
Air Inlet Max. Length**
Min.
Max.
6”
8”
10”
12”
399B
Category I
(Type B
Equivalent)
6”
5’
25’
Galvanized
Steel,
PVC, ABS,
CPVC
100’
499B
75’
100’
649B
8”
40’
749B
899B
989B
10”
75’
100’
1259B
12”
1529B
1799B
14”
40’
75’
1999B
2069B
2339B
16”
