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VII. Venting (continued)
D. Optional Room Air for Combustion
a. Room air is optional for commercial
1. General Guidelines
applications. Follow the requirements in
this section when air for combustion is
supplied from 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
to the boiler room or enclosure. Follow
a. Provide combustion and ventilation air
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 two
methods.
Provide two permanent openings, one
b. Two Permanent Openings Method:
within 12 in. (300 mm) of the top of the
enclosure and one within 12 in. (300 mm)
of 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.
of all appliances within the enclosure.
(550 mm
ii. Horizontal ducts: minimum free area
of each opening shall be 1 in.
input rating of all appliances within
Btu/hr (1100 mm
the enclosure.
c. One Permanent Opening Method: Provide
one permanent opening, commencing
within 12 in. (300 mm) of the top of the
enclosure.
/kW) of total input rating
/4000 Btu/hr
2
2
/kW) of total
/2000
2
2
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:
i. 1 in.
of total input rating of all appliances
2
located within the enclosure.
ii. Not less than the sum of the areas of all
vent connectors in the space.
louvers or dampers must be interlocked
d. Motorized Louvers or Dampers: Motorized
with the boiler 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 Section VIII "Electrical".
a.
For standard horizontal sidewall
3. Terminations
terminations, see Figure 7 and 8. For
vertical roof terminations, see Figure 9 and
10.
b. When using room air for combustion,
use 90° elbow or tee for sidewall vent
termination.
When an existing boiler is removed from a
E. Removing Existing Boiler
common venting system, the common venting
system is likely to be too large for proper
venting of the remaining appliances. At the time
of removal of an existing boiler, the following
steps should be performed with each appliance
remaining connected to the common venting
system. Make sure the appliance are not in
operation while carrying out these stapes.
Sources of combustion air contaminants,
including
chlorines,
(CFC's),
petroleum
volatile vapors or other chemicals must not
be present in the boiler room. If any of these
contaminants is present, severe boiler corrosion
and failure will result.
28
/3000 Btu/hr (700 mm
WARNING
chlorofluorocarbons
distillates,
detergents,
/kW)
2
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