Page 20
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 22
OIL
FURNACE
EQUIPMENT IN CONFINED SPACE
ALL AIR FROM OUTSIDE
OUTLET AIR
INLET AIR
WATER
HEATER
CHIMNEY
OR OIL
VENT
FIGURE 23
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 con
sidered. If the design and free area of protective covering 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 equip
ment so that they are opened automatically during equip
ment operation.
CAUTION
Combustion air openings in the front of the furnace
must be kept free of obstructions. Any obstruction
will cause improper burner operation and may result
in a fire hazard or injury.
CAUTION
The barometric shall be in the same atmospheric
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 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).
To convert the AFII burner from confined space to out
side combustion air, simply remove the three screws at
taching the inlet air scoop to the burner and insert 4"
(102 mm) direct 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 relief 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. The only exception are baro
metric draft reliefs as required by FIELD or TJERN
LUND power vents.
Removal of Unit from Common Venting System
In the event that an existing furnace is removed from a venting
system commonly run with separate appliances, the venting
system is likely to be too large to properly vent the remaining
attached appliances. The following test should be conducted
while each appliance is in operation and the other ap
pliances not in operation remain connected to the com
mon venting system. If venting system has been installed
improperly, the system must be corrected as outlined in the
previous section.
1− Seal any unused openings in the common venting sys
tem.
2− Visually inspect venting system for proper size and hori
zontal pitch and determine there is no blockage or restric
tion, leakage, corrosion or other deficiencies which could
cause an unsafe condition.
