Combustion air must be free of acid
forming chemicals such as sulphur,
fluorine, and chlorine. These
elements are found in aerosol
sprays, detergents, bleaches,
cleaning solvents, air fresheners,
paint and varnish removers,
refrigerants and many other
commercial and household products.
Vapors from these products when
burned in a gas flame form acid
compounds. The acid compounds
increase the dew point temperature
of the flue products and are highly
corrosive after they condense.
A WARNING: ALL FURNACE
INSTALLATIONS MUST COMPLY
WITH THE NATIONAL FUEL GAS
CODE AND LOCAL CODES TO
PROVIDE ADEQUATE COMBUS·
TION AND VENTILATION AIR FOR
THE FURNACE. FAILURE TO DO
SO CAN RESULT IN EXPLOSION,
FIRE, PROPERTY DAMAGE,
CARBON MONOXIDE POISONING,
PERSONAL INJURY OR DEATH.
Combustion air requirements are
determined by whether the furnace is
in an open (unconfined) area or in a
confined space such as a closet or
small room.
FURNACE LOCATED IN AN
UNCONFINED SPACE
Using indoor air for combustion.
An unconfined space must have at
least 50 cubic feet for each 1,000
BTUH of the
total input for all
appliances
in the space. Here are a
few examples of the room sizes
required for different inputs. The
sizes are based on 8 foot ceilings.
If the open space containing the
furnace is in a building with tight
construction (contemporary
construction), outside air may still be
required for the furnace to operate
and vent properly. Outside air
openings should be sized the same
as for a confined space.
TABLE12
UNCONFINED SPACE
DIMENSIONS
BTUH Minimum Sq. Feel
TypicalRoomSize
Input
With 8 Foot Ceiling With 8 lool Ceiling
45,000
281 14' x 20' OR 16' x 18'
60.000 375
15' x 25' OR 19' x 20'
75.000
469 15' x31'0R 20' x24'
90,000
563 20' x 28' OR 24' x 24'
105,000
657 20' x 33' OR 26' x 25'
120,000
750
25' x 30' OR 24' x 32'
FURNACE LOCATED IN A
CONFINED SPACE.
A confined space (any space smaller
than shown before as "unconfined")
must have
two openings into the
space. One opening must be
within 12" of the ceiling and the
other must be within 12" of the
floor.
The openings must be sized
by how they connect to the heated
area or to the outside, and by the
input of all appliances in the space.
If the confined space is within a
building with tight construction,
combustion air must be taken from
outdoors or areas freely
communicating with the outdoors.
A. USING INDOOR AIR FOR
COMBUSTION
If combustion air is taken from the
heated area, the openings must
each have at least 100 square
inches of tree area.
Each opening
must have at least
one square inch
of free area for each 1,000 BTUH
of total input
in the space. See
Table 13 for some examples of
typical openings required.
IMPORTANT: DO NOT TAKE AIR
FROM A HEATED SPACE WITH A
FIREPLACE, EXHAUST FAN OR
OTHER DEVICE THAT MAY PAO·
DUCE A NEGATIVE PRESSURE.
FIGURE27
AIR FROM HEATED SPACE
TABLE 13
INDOOR AIR OPENING
DIMENSIONS
BTUH Free Area
Input
EachOpening
45.000
100 square inches
60,000 100 square inches
75.000 100 square inches
90,000 100 square inches
105,000 105 square inches
120.000 120 square inches
f
t
B.
USING OUTDOOR AIR FOR
COMBUSTION
Method 1
If combustion air is taken from
outdoors through
verti.cal ducts, the
openings and ducts must have at
least
one square inch of free area
for each 4,000 BTUH
of total
appliance input. See table 14 for
some typical sizes.
y
TABLE14
VERTICAL OUTDOOR AIR
OPENING DIMENSIONS
BTUH Free Area
RoundPipe
Input EachOpening Size
45,000
11.25 square inches
4"
60,000 15 00 square inches
5"
75,000 18.75 square inches
5"
90,000 22.50 square inches 6"
105,000
26.25 square inches
6"
120.000
30.00 square inches
7"
f
t
f
!
I
i
~
l~A~:
WATER
HEATER
!
D
NOTE:
EACH OPENING SHALL
HAVE
A FREEAREA OF
NOT LESS THAN ONE
SQUARE INCH PER
1,000 BTU PER HOUR
OF THE TOTAL INPUT
RATING OF ALL
EQUIPMENT IN THE
ENCLOSURE, BUT NOT
LESS THAN 100
SQUARE INCHES.
30
To Next Page
Loading...