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1. Two Permanent Opening Method
a. One opening starting within 12" of the top
of the boiler room and one starting within
12" of the bottom of the boiler room shall
be provided. The openings shall be open
directly to the outside or ducted directly to
the outside.
b. When directly open to the outside or ducted
to the outside by vertical ducts, each opening
or duct shall have a minimum free open area
2
of 1 in
per 4000 BTU total input rating of the
boiler(s) in the room.
c. If ducted to the outside through horizontal
ducts, each opening or duct shall have a
minimum free area of 1 in
total input rating of the boiler(s) in the room.
2. One Permanent Opening Method
a. One opening commencing within 12" of
the top of the room shall be provided. The
opening shall be directly to the outside
or shall be ducted to the outside with a
horizontal or vertical duct.
b. The opening or duct shall have a minimum
free area of:
2
c. 1 in
/ 3000 BTU/hour of the total input rating
of all appliances (boilers) in the room.
d. Additional area must be provided for other air
consuming equipment in the room.
3. Mechanical Air Supply Systems
a. The combustion air supply may be provided
by a mechanical air supply system. If utilized,
the combustion air must be provided from the
outside at a minimum rate of 0.35 ft
for every 1000 Btu/hr. input for all appliances
located in the space.
b. If exhaust fans are utilized, additional air shall
be provided to replace the exhausted air.
c. Each boiler and other appliance must be
interlocked to prevent operation when
the mechanical air supply system is not in
operation.
Thermal Solutions, 1175 Manheim Pike, Lancaster, PA 17601 Website: www.thermalsolutions.com
Phone: 717-239-7642 Fax: 877-501-5212 Email: sales@thermalsolutions.com
2
per 2000 BTU
3
/min.
d. If the combustion air is provided by a
buildings mechanical ventilation system, the
system shall be sized to provide the specified
combustion air in addition to the ventilation
air requirements.
4. Louvers and Grilles
a. The required size of openings for combustion,
ventilation, and dilution air shall be based on
the net free area of each opening. Where the
free area through a design of louver, grille, or
screen is new, it shall be used in calculating
the size opening required to provide the free
area specified. Where the louver and grille
design and free area are not new, it shall be
assumed that wood louvers have a 25 percent
free area, and metal louvers and grilles have a
75 percent free area. Non-motorized louvers
and grilles shall be fixed in the open position.
5. Screens
a. Screens shall not be smaller than 1/4" mesh.
6. Motorized Louvers
a. Motorized louvers shall be interlocked with
the appliance so they are proven in the full
open position prior to main burner ignition
and during main burner operation. Mens
shall be provided to prevent the main burner
from igniting should the louver fail to open
during burner startup and to shut down the
main burner if the louver closes during burner
operation.
7. Combustion Air Ducts
a. Combustion air ducts shall comply with the
following:
b. Ducts shall be constructed of galvanized steel
or a material having equivalent corrosion
resistance, strength and rigidity.
c. Ducts shall terminate in an unobstructed
space, allowing free movement of combustion
air to the appliances.
d. Ducts shall serve a single space.
13
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