A801X-SVX001-1B-EN
27
Air for Combustion and
Ventilation
Adequate flow of combustion and ventilating air must
not be obstructed from reaching the Furnace. Air
openings provided in the Furnace casing must be kept
free of obstructions which restrict the flow of air.
Airflow restrictions affect the efficiency and safe
operation of the Furnace. Keep this in mind should you
choose to remodel or change the area which contains
your Furnace. Furnaces must have a free flow of air for
proper performance.
Provisions for combustion and ventilation air shall be
made in accordance with "latest edition" of Section 9.3,
Air for Combustion and Ventilation, of the National
Fuel Gas Code, ANSI Z223.1 / NFPA 54. Installation
Codes, and applicable provisions of the local building
codes. Special conditions created by mechanical
exhausting of air and fireplaces must be considered to
avoid unsatisfactory Furnace operation.
Furnace location may be in an uunnccoonnffiinneedd space or a
ccoonnffiinneedd space.
UUnnccoonnffiinneedd space are installations with 50 cu. ft. or
more per 1000 BTU/hr input from all equipment
installed. Unconfined spaces are defined in the table
and illustration for various furnace sizes. These spaces
may have adequate air by infiltration to provide air for
combustion, ventilation, and dilution of flue gases.
Buildings with tight construction (for example, weather
stripping, heavily insulated, caulked, vapor barrier,
etc.), may need additional air provided as described for
confined space.
Minimum Area in Square Feet for Unconfined Space Installations
Furnace Maximum BTUH Input
Rating
With 8 Ft. Ceiling,
Minimum Area in Square Feet
of Unconfined Space
40,000
60,000
80,000
100,000
120,000
250
375
500
625
750
NO
DOORS
FURNACE
WATER
HEATER
CLOTHES
DRYER
UNCONFINED
50 CU. FT. OR MORE
PER 1000 BTU/HR INPUT
ALL EQUIP. INSTALLED
CCoonnffiinneedd spaces are installations with less than 50 cu.
ft. of space per 1000 BTU/ hr input from all equipment
installed. Confined spaces are defined in the table and
illustration for various furnace sizes. Air for combustion
and ventilation requirements can be supplied from
inside the building.
The following types of installations will rreeqquuiirree use of
OUTDOOR AIR for combustion, due to chemical
exposures:
• Commercial buildings
• Buildings with indoor pools
• Furnaces installed in commercial laundry rooms
• Furnaces installed in hobby or craft rooms
• Furnaces installed near chemical storage areas
Exposure to the following substances in the
combustion air supply will also require OUTDOOR AIR
for combustion:
• Permanent wave solutions
• Chlorinated waxes and cleaners
• Chlorine based swimming pool chemicals
• Water softening chemicals
• Deicing salts or chemicals
• Carbon Tetrachloride
• Halogen type refrigerants
• Cleaning solvents (such as perchloroethylene)
• Printing inks, paint removers, varnish, etc.
• Hydrochloric acid
• Cements and glues
• Antistatic fabric softeners for clothes dryers
• Masonry acid washing material
NNoottee:: Extended warranties are not available in some
instances. Extended warranty does not cover
repairs to equipment installed in establishments
with corrosive atmospheres, including but not
limited to, dry cleaners, beauty shops, and
printing facilities.
Minimum Free Area in Square Inches Each Opening (Furnace
Only) in a Confined Space
Furnace Max
BTUH.Input
Rtg.
Air From
Inside
Air From Outside
Vertical Duct
(a)
Horizontal
Duct (b)
40,000
60,000
80,000
100,000
120,000
100
100
100
100
120
10
15
20
25
30
20
30
40
50
60
(a) 1 Square inch per 4000 BTU/hr Vertical Duct.
(b) 1 Square inch per 2000 BTU/hr Horizontal Duct.
FFuurrnnaaccee GGeenneerraall IInnssttaallllaattiioonn
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