Page 20
2.D Locating Vent & Combustion Air
Terminals
2.D.1
Side Wall Vent Terminal
Category lll only
An appropriate quality side wall vent terminal must be used.
The terminal provides a means of installing the vent
piping through the building wall, and must be
located in accordance with ANSI Z223.1/NFPA
54 and applicable local codes. In Canada, the
installation must be in accordance with CSA
B149.1 or .2 and local applicable codes. Consider
the following when installing the terminal:
1. Figure 1 shows the requirements for mechanical
vent terminal clearances for the U.S. and Canada.
2. Vent terminals for condensing appliances or
appliances with condensing vents are
not
permitted to terminate above a public walkway,
or over an area where condensate or vapor could
create a nuisance or hazard.
3. Locate the vent terminal so that vent gases cannot
be drawn into air conditioning system inlets.
4. Locate the vent terminal so that vent gases cannot
enter the building through doors, windows, gravity
inlets or other openings. Whenever possible,
locations under windows or near doors should be
avoided.
5. Locate the vent terminal so that it cannot be blocked
by snow. The installer may determine that a vent
terminal must be higher than the minimum shown in
codes, depending upon local conditions.
6. Locate the terminal so the vent exhaust does not
settle on building surfaces or other nearby objects.
Vent products may damage such surfaces or
objects.
7. If the boiler or water heater uses ducted
combustion air from an intake terminal located on
the same wall, locate the vent terminal at least 7
feet (213 cm) horizontally from the combustion air
terminal, and locate the vent terminal at least 1
foot (0.3m) above the combustion air terminal.
2.D.2
Side-wall Combustion Air Terminal
Category l and lll
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
least 7 feet ( 2.1 m) 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.
For Category lll only:
4. If the unit is side-wall vented to the same wall as
it's ducted combustion air, use Figure 3 on page
22 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 3)
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 3).
2.D.3
Vertical Vent Terminal
Category l and lll
When the unit is 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 horizontal 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.
2.D.4
Vertical Combustion Air Terminal
Category l and lll
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 2 on page 22
NOTE:
For US installations, the vent for this appliance shall
not terminate:
i) over public walkways; or
ii) near soffit vents or crawl space vents or other
areas where condensate or vapor could create a
nuisance or hazard or cause property damage; or
iii) where condensate vapor could cause damage
or could be detrimental to the operation of
regulators, relief valves, or other equipment.
LAARS Heating Systems
