Page 21
The
O
MNI
T
HERM
2.C.2
Side-wall Combustion Air Terminal
Consider the following when installing the terminal.
1. Do not locate the air inlet terminal near a source
of corrosive chemical fumes (e.g., cleaning fluid,
chlorine compounds, etc.).
2.
Locate the terminal so that it will not be subject to
damage by accident or vandalism. It must be at leat
7 feet (2.1m) above a public walkway.
3. Locate the combustion air terminal so that it cannot
be blocked by snow. The National Fuel Gas Code
requires that it be at least 12 inches (30 cm) above
grade, but the installer may determine it should be
higher, depending upon local conditions.
4. If the unit is side-wall vented to the same wall, use
Figure 2 to determine the proper mounting locations.
5. Multiple vent kits should be installed such that the
horizontal distance between outlet group and inlet
group is 84” (213 cm). (See Figure 2).
6. The vent outlet must be at least 12” above the top
of the air inlet and must be at least 84” (213 cm)
horizontally from the air inlet. (See Figure 2).
2.C.3 Vertical Vent Terminal
When the unit vented through the roof, the vent must
extend at least 3 feet (0.9 m) above the point at which
it penetrates the roof. It must extend at least 2 feet (0.6
m) higher than any portion of a building within a horizon-
tal distance of 10 feet (3.0 m), and high enough above
the roof line to prevent blockage from snow. When the
combustion air is taken from the roof, the combustion
air must terminate at least 12” (30 cm) below the vent
terminal.
84”
2”
Min. (Typ)
Multiple Vents
Window
2” Min. (Typ)
Multiple Air Intakes
Above expected snow line
213
36”
90
12”
OUTLET
INLET
12”
Terminals must be placed such that they are a Minimum of 12” above the
expected snow line. Local codes may have more specific requirements and
must be consulted. Refer to the NFPA 54 National Fuel Gas Code and your
local codes for all required clearances for venting.
Figure 2. Minimum Side-wall Venting Distance for Single and Multiple Units.
2.C.4 Vertical Combustion Air Terminal
When combustion air is taken from the roof, a field-
supplied rain cap or an elbow arrangement must be used
to prevent entry of rain water. The opening on the end of
the terminal must be at least 12” (30 cm) above the point
at which it penetrates the roof, and high enough above the
roof line to prevent blockage from snow. When the vent
terminates on the roof, the combustion air must terminate
at least 12” (30 cm) below the vent terminal. See Figure 3.
Figure 3. Combustion Air and Vent through Roof
