Weil-McLain 88 - Manual (Page 6)

Weil-McLain 88 Water and steam boilers — Series 2 — for Gas, Light Oil, & Gas/Light Oil-Fired Burners
6 Part No. 550-100-068/1009
freely communicate with the outdoors, as follows:
Where directly communicating with the outdoors or where s
communicating to the outdoors through vertical ducts, each
opening shall have a minimum free area of 1 in
2 /4000 Btuh
(550 mm 2 /kW) of total input rating of all appliances in the
enclosure.
Where communicating with the outdoors through horizon-
s
tal ducts, each opening shall have a minimum free area of
1 in
2 /2000 Btuh (1100 mm 2 /kW) of total input rating of all
appliances in the enclosure.
Outside openings 
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 combination
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 adequate sup-
ply of combustion, ventilation, and dilution air and shall he approved
by the authority having jurisdiction.
Mechanical Combustion Air Supply
Where all combustion air is provided by a mechanical air supply
Before installing boiler
(continued)
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, s
additional air shall be provided to replace the
exhausted air.
Each of the appliances served shall be inter-
s
locked to the mechanical air supply system to
prevent main burner operation where the me-
chanical air supply system is not in operation.
Where combustion air is provided by the build-
s
ing’s mechanical 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, venti-
lation, and dilution air shall be based on the
NET
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.
-INIMUM
Screens shall not be smaller than ¼ inch mesh.
-OTORIZED
Motorized louvers shall be interlocked with the appli-
ance so they are proven in the full open position prior
to main burner ignition and during main burner opera-
tion. 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.