Outside And Ambient Combustion Air; Estimated Free Area; Free Area; Unconfined Space Minimum Area In Square Inch - York FC9C UP Series Installation Manual

This type of installation requires that the supply air to the appli-
ance(s) be of a sufficient amount to support all of the appliance(s)
in the area. Operation of a mechanical exhaust, such as an exhaust
fan, kitchen ventilation system, clothes dryer or fireplace may cre-
ate conditions requiring special attention to avoid unsatisfactory
operation of gas appliances. A venting problem or a lack of supply
air will result in a hazardous condition, which can cause the appli-
ance to soot and generate dangerous levels of CARBON MONOX-
IDE, which can lead to serious injury, property damage and / or
death.
Combustion Air Source From Outdoors
The blocking effects of louvers, grilles and screens must be given con-
sideration in calculating free area. If the free area of a specific louver or
grille is not known, refer to Table 10, to estimate free area.
TABLE 10: Estimated Free Area
Wood or Metal
Louvers or Grilles
Screens+
* Do not use less than 1/4" (0.635 cm) mesh.
+ Free area or louvers and grille varies widely; the installer should follow lou-
ver or grille
manufacturer's instructions.
Dampers, Louvers and Grilles (Canada Only)
1. The free area of a supply air opening shall be calculated by sub-
tracting the blockage area of all fixed louvers grilles or screens
from the gross area of the opening.
2. Apertures in a fixed louver, a grille, or screen shall have no dimen-
sion smaller than 0.25" (6.4 mm).
GAS
GABLE
VENT
VENT
VENTILATED
ATTIC
OPTIONAL
TOP ABOVE
INLET (a)
INSULATION
OUTLET
SOFFIT
AIR (a)
VENT
GAS
WATER
HEATER
VENTILATED
CRAWL SPACE
5. A square or rectangular shaped duct shall only be used
when the required free area of the supply opening is
2 2
9 in (58.06 cm ) or larger. When a square or rectangular
duct is used, its small dimensionshall not be less than
3 in (7.6 cm).
6. An air inlet supply from outdoors shall be equipped with
a means to prevent the direct entry of rain and wind.
Such means shall not reduce the required free area of
the air supply opening.
7. An air supply inlet opening from the outdoors shall
be located not less than 12" (30.5 cm) above the
outside grade level.
FIGURE 20: Outside and Ambient Combustion Air
Unitary Products Group
Wood 20-25%*
Metal 60-70% *
1/4" (0.635 cm)
mesh or larger 100%
AIR SUPPLY OPENINGS AND DUCTS
1. An opening may be used in lieu of a duct to provide to provide the outside air
supply to an appliance unless otherwise permitted by the authority having
jurisdiction. The opening shall be located within 12" (30.5 cm) horizontally from,
the burner level of the appliance. Refer to "AIR SOURCE FROM OUTDOORS
AND VENT AND SUPPLY AIR SAFETY CHECK" in these instructions for
additional information and safety check procedure.
2. The duct shall be either metal, or a material meeting the class 1
requirements of CAN4-S110 Standard for Air Ducts.
3. The duct shall be least the same cross-sectional area as the free
area of the air supply inlet opening to which it connects.
4. The duct shall terminate within 12 in (30.5 cm) above, and
within 24 in (61 cm) horizontally from, the burner level of
the appliance having the largest input.
GABLE
VENT
VENTILATED
ATTIC
TOP ABOVE
INSULATION
SOFFIT
VENT
GAS
WATER
HEATER
INLET
AIR (b)
3. A manually operated damper or manually adjustable louvers are
not permitted for use.
4. A automatically operated damper or automatically adjustable lou-
vers shall be interlocked so that the main burner cannot operate
unless either the damper or the louver is in the fully open position.
TABLE 11: Free Area
Minimum Free Area Required for Each Opening
BTUH
Input
Horizontal Duct
Rating
(2,000 BTUH)
60,000
30 sq. in. (194 cm
80,000
40 sq. in. (258 cm
100,000
50 sq. in. (323 cm
120,000
60 sq. in. (387 cm
EXAMPLE: Determining Free Area.
Appliance 1Appliance
+ 30,000 = (130,000 ÷ 4,000) = 32.5 Sq. In. Vertical
100,000
Appliance 1Appliance
+ 30,000 = (130,000 ÷ 2,000) = 65 Sq. In. Horizontal
100,000
TABLE 12: Unconfined Space Minimum Area in Square Inch
BTUH Input Rating Minimum Free Area Required for Each Opening
60,000
80,000
100,000
120,000
OUTLET
AIR (b)
INLET
AIR (b)
COMBUSTION AIR SOURCE FROM OUTDOORS
1. Two permanent openings, one within 12 in (30.5 mm) of the top and
GAS
one within 12 in (30.5 mm) of bottom of the confined space,
VENT
permanent openings,
with the outdoors, crawl spaces or attic spaces.
2. One permanent openings, commencing within 12 in (30.5 mm)of the
top of the enclosure shall be permitted where the equipment has
clearances of at least 1 in (2.54 cm) from the sides and back and
6 in (15.24 cm) from the front of the appliance. The opening shall
communicate directly with the outdoors and shall have a minimum
free area of:
a. 1 square in per 3000 Btu per hour (6.45
total input rating of all equipment located in the enclosure.
b.
Not less than the sum of all vent connectors in the confined space.
3. The duct shall be least the same cross-sectional area as the free
area of the air supply inlet opening to which it connects.
INLET
4. The blocking effects of louvers, grilles and screens must be given
AIR (a)
consideration in calculating free area. If the free area of a specific
louver aor grille is not known.
292278-UIM-A-0108
Vertical Duct or
Round Duct
Opening to Outside
(4,000 BTUH)
(4,000 BTUH)
2 2
) 15 sq. in. (97 cm ) 5" (13 cm
2 2
) 20 sq. in. (129 cm ) 5" (13 cm
2 2
) 25 sq. in. (161 cm ) 6" (15 cm
2 2
) 30 sq. in. (194 cm ) 7" (18 cm
2Total Input
2Total Input
2
60 (387 cm )
2
80 (516 cm )
2
100 (645 cm )
2
120 (774 cm )
GAS
VENT
OUTLET
AIR (a)
GAS
WATER
HEATER
INLET
AIR (a)
Two
shall communicate directly or by means of ducts
3
cm per 0.879 kW) of the
2
)
2
)
2
)
2
)
19