Page 9
ing with the outdoors through horizontal ducts, each open-
ing shall have a minimum free area of 1 square inch (6.4
square centimeters) per 2,000 Btu (586 W) per total input
rating of all equipment in the enclosure (See figure 11).
EQUIPMENT IN CONFINED SPACE
ALL AIR FROM OUTSIDE
(Inlet Air from Crawl Space and
Outlet Air to Ventilated Attic)
NOTE − The inlet and outlet air openings shall each have a free area of
at least one square inch (6.4 square centimeters) per 4,000 Btu (1172
W) per hour of the total input rating of all equipment in the enclosure.
VENTILATION LOUVERS
(Each end of attic)
OUTLET
AIR
WATER
HEATER
INLET
AIR
CHIMNEY
OR OIL
VENT
VENTILATION
LOUVERS
(For unheated
crawl space)
FIGURE 9
OIL
FURNACE
EQUIPMENT IN CONFINED SPACE
ALL AIR FROM OUTSIDE
(All Air Through Ventilated Attic)
NOTE−The inlet and outlet air openings shall each have a free area of at
least one square inch (6.4 square centimeters) per 4,000 Btu (1172 W)
per hour of the total input rating of all equipment in the enclosure.
CHIMNEY
OR OIL
VENT
WATER
HEATER
OUTLET
AIR
VENTILATION LOUVERS
(Each end of attic)
INLET AIR
(Ends 12" above
bottom)
FIGURE 10
OIL
FURNACE
EQUIPMENT IN CONFINED SPACE
ALL AIR FROM OUTSIDE
OUTLET AIR
INLET AIR
WATER
HEATER
CHIMNEY
OR OIL
VENT
FIGURE 11
NOTE − Each air duct opening shall have a free area of at least one
square inch (6.4 square centimeters) per 2,000 Btu (586 W) per hour
of the total input rating of all equipment in the enclosure. If the equip-
ment room is located against an outside wall and the air openings
communicate directly with the outdoors, each opening shall have a
free area of at least one square inch (6.4 square centimeters) per
4,000 Btu (1172 W) per hour of the total input rating of all other equip-
ment in the enclosure.
OIL
FURNACE
When ducts are used, they shall be of the same cross−sec-
tional area as the free area of the openings to which they
connect. The minimum dimension of rectangular air ducts
shall be no less than 3" (76 mm). In calculating free area,
the blocking effect of louvers, grilles, or screens must be
considered. If the design and free area of protective cover-
ing is not known for calculating the size opening required, it
may be assumed that wood louvers will have 20 to 25 per-
cent free area and metal louvers and grilles will have 60 to
75 percent free area. Louvers and grilles must be fixed in
the open position or interlocked with the equipment so that
they are opened automatically during equipment operation.
Direct Connection of Outdoor Air for Combustion
The Beckett AFII burner was designed to allow for direct air
intake piping (4" [102 mm]). The maximum equivalent
length of pipe is 70 feet (21.3 m). A 90
_
elbow equals
6feet (1.8 m). The enclosed intake pipe ring may be used
to facilitate direct air intake to the burner through the right
side of the cabinet. The AFG burner requires a special kit
for direct air intake. Refer to kit instructions.
To convert the AFII burner from confined space to outside
combustion air, simply remove the three screws attaching
the inlet air scoop to the burner and insert 4" (102 mm) di-
rect air intake piping.
The use of a barometric relief placed in the intake pipe is
recommended when outdoor combustion air is directly
connected to the burner. This will allow confined space air
to be used as combustion air in the event that the opening
to the outdoor air becomes blocked. Using a barometric re-
lief in the intake will reduce the chance of sooting.
