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VII. Venting (continued)
H. Optional Room Air for Combustion
1. General Guidelines
a. Room air is optional for commercial applications.
Follow the requirements in this section when air
for combustion is supplied from the boiler room.
b. Avoid combustion air contaminants in the boiler
room. Permanently remove any contaminants
found in the boiler room. If contaminants cannot
be removed, do not use room air for combustion.
2. Outdoor Openings to Boiler Room
a. Provide combustion and ventilation air to the
boiler room or enclosure. Follow the National
fuel Gas Code, ANSI Z223.1, or, in Canada,
Installation Code for Gas Burning Appliances and
Equipment, CGA Standard B149 Code as well as all
applicable local codes. Use one of the following
methods.
b. Two Permanent Openings Method: Provide two
permanent openings, one within 12 in. (300 mm)
from the top of the enclosure and one within 12
in. (300 mm) from the bottom of the enclosure.
Openings must communicate directly, or by
ducts, with the outdoors or spaces that freely
communicate with the outdoors. Ensure the
ducts to communicate with outdoors have the
same cross-sectional area as the free area of the
opening to which they are connected.
i.
Direct communication or through vertical ducts:
minimum free area of each opening shall be 1
in.
/4000 Btu/hr (550 mm
2
rating of all appliances within the enclosure.
ii. Horizontal ducts: minimum free area of each
opening shall be 1 in.
kW) of total input rating of all appliances within
the enclosure.
c. One Permanent Opening Method: Provide one
permanent opening, commencing within 12 in.
(300 mm) of the top of the enclosure.
i.
The opening shall communicate through a
vertical or horizontal duct to the outdoors
or spaces that freely communicate with the
outdoors and shall have a minimum free area
of the following:
ii. 1 in.
/3000 Btu/hr (700 mm
2
input rating of all appliances located within the
enclosure.
iii. Not less than the sum of the areas of all vent
connectors in the space.
3. Motorized Louvers or Dampers
/kW) of total input
2
/2000 Btu/hr (1100 mm
2
2
/kW) of total
2
Motorized louvers or dampers must be interlocked
with the appliance to allow ignition and firing of
the burner only when louvers are in the fully-open
position. Wire the interlock to the Auto Reset
External Limit connections. See the "Electrical"
section in this manual.
4. Terminations
a. When using room air for combustion, use 90°
elbow or tee for sidewall vent termination.
!
Sources of combustion air contaminants, including
chlorines, chlorofluorocarbons (CFC's), petroleum
distillates, detergents, volatile vapors or other
chemicals must not be present in the boiler room.
/
If any of these contaminants are present, severe
corrosion and failure will result.
33
WARNING
WARNING
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