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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 11
OIL
FURNACE
OIL
FURNACE
Equipment In Confined Space − All Air From
Outside (via 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 12
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 opera-
tion.
Equipment In Confined Space − All Air From
Outside
OUTLET AIR
INLET AIR
Figure 13
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
EQUIPMENT 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 RAT-
ING OF ALL OTHER EQUIPMENT IN THE ENCLOSURE.
WATER
HEATER
WATER
HEATER
CHIMNEY
OR OIL
VENT
CAUTION
The barometric control shall be in the same atmo-
spheric pressure zone as the combustion air inlet to
the furnace. Deviation from this practice will cause
improper burner operation and may result in a fire
hazard or injury.
Direct Connection of Outdoor Air for Combus-
tion
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 facil-
itate 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.
CAUTION
DO NOT USE a barometric draft relief in exhaust vent
pipe if outdoor combustion air is connected directly
to the burner.
