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Weil-McLain 94 Series 3 Water and steam boilers — for Gas, Light Oil, & Gas/Light Oil-Fired Burners
6 Part No. 550-110-275/1018
Before installing boiler
(continued)
freely communicate with the outdoors, as follows:
• Where directly communicating with the outdoors or
where communicating to the outdoors through vertical
ducts, each opening shall have a minimum free area of
1 in
2
⁄4000 Btuh (550 mm2/kW) of total input rating of
all appliances in the enclosure.
• Where communicating with the outdoors through hori-
zontal ducts, each opening shall have a minimum free
area of 1 in
2
⁄2000Btuh (1100 mm
2
/kW) of total input
rating of all appliances in the enclosure.
Outside openings: ONE permanent opening method
One permanent opening, commencing within 12 inches
(300 mm) of the top of the enclosure, shall be provided. The
appliance shall have clearances of at least 1 in. (25 mm) from
the sides and back and 6 inches (150 mm) from the front of the
appliance. The opening shall directly communicate with the
outdoors or 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:
(1) 1 in
2
⁄3000 Btu/hr (700 mm
2
per kW) of the total input rating
of all appliances located in the enclosure, and . . .
(2) Not less than the sum of the areas of all vent connectors in
the space.
Combustion air — combination indoor
and outdoor openings
ANSI/NFPA 54 allows combustion air to be taken from a com-
bination of openings to outside and to interior spaces. Follow all
requirements of the standard to determine the minimum volume
of interior spaces and to calculate minimum sizes of openings.
Engineered Installations
Engineered combustion air installations shall provide an ad-
equate supply of combustion, ventilation, and dilution air and
shall be approved by the authority having jurisdiction.
Mechanical Combustion Air Supply
Where all combustion air is provided by a mechanical air supply
system, the combustion air shall be supplied from outdoors at
the minimum rate of 0.35 ft
3
/minute per 1000 Btuh (0.034 m
3
/
min per kW) for all appliances located within the space.
• Where exhaust fans are installed in the building, addi-
tional air shall be provided to replace the exhausted air.
• Each of the appliances served shall be interlocked to the
mechanical air supply system to prevent main burner
operation where the mechanical air supply system is not
in operation.
• Where combustion air is provided by the building’s me-
chanical ventilation system, the system shall provide the
specified combustion air rate in addition to the required
ventilation air.
Louvers, Grilles, and Screens.
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 or grille or screen
is known, 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 known,
it shall be assumed that wood louvers will have 25 percent free
area, and metal louvers and grilles will have 75 percent free area.
Non-motorized louvers and grilles shall be fixed in the open
position.
Minimum screen mesh size
Screens shall not be smaller than ¼ inch mesh.
Motorized louvers
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. Means shall be proved 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 louvers close during burner operation.
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