CONQUEST 80 - Furnace Located in Unconfined Space Using Indoor Air; Furnace Located in Aconfined Space; Using Indoor Air for Combustion; Using Outdoor Air for Combustion

FURNACES LOCATED IN AN
UNCONFINED SPACE AND USING
INDOOR AIR FOR COMBUSTION
An unconfined space must have at
least 50 CUBIC FEET volume for
each 1,000 BTUH of the TOTAL
INPUT FOR ALL COMBUSTION
APPLIANCES in the space. The
following table gives examples of the
room sizes required for different
inputs. The room dimensions are
based on an eight foot ceiling height.
TABLE 16
UNCONFINED SPACE
DIMENSIONS
•
BTUH
Min. Sq. Feet Typ. Room Size
Input With 8' Ceiling With 8' Ceiling
45,000
281 12'x24' or 16'x18'
50,000 312
14'x24' or 18'x18'
67,500
421 15'x28' or 20'x21'
75,000
469
15'x31' or 20'x24'
100,000 625
20'x31' or 25'x25'
125,000 833
23'x34' or 26'x30'
150,000 938
25'x38' or 30'x31'
FURNACE LOCATED IN A
CONFINED SPACE
If the open space containing the
J
furnace is in a building with
contemporary tight construction,
outside air may still be required for
the furnace to operate and vent
properly. Size any outside air
openings the same as for a
confined space.
A confined space is any space
housing a combustion appliance with
dimensions smaller than those shown
before as unconfined.
A confined
space must have openings into
the space, which are located in
accordance with the requirements
set forth in following sections.
Size each opening based on 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
tightly constructed building,
combustion air must be drawn from
outdoors or from an area freely
communicating with the outdoors.
USING INDOOR AIR FOR
COMBUSTION
If combustion air comes from a
heated area, EACH opening must
have at least one square inch of
free area for each 1,000 BTUH of
total input in the space. In no case
should each opening have less than
100 square inches of free area.
Here are examples of typical
openings required.
FIGURE 23
AIR FROM HEATED SPACE
ii
GAS
WATER
HEATER
i :J
i 'I
FURNACE
I
l
12·
MAX.
TABLE17
INDOOR AIR OPENING
DIMENSIONS
BTUH Input
Free Area Each Opening
45,000
100,000
150,000
100 sq. inches
100 sq. inches
150 sq. inches
IMPORTANT: NEVER TAKE
COMBUSTION AIR FROM A
HEATED SPACE CONTAINING .\
FIREPLACE, EXHAUST FAN, OR
OTHER DEVICE THAT CAN CAUSE
A NEGATIVE PRESSURE.
NOTE:
EACH OPENING SHALL
HAVE A FREE AREA
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.
USING OUTDOOR AIR FOR
COMBUSTION
IMPORTANT:NEVERTAKE
COMBUSTION AIR FROM AN
ATTIC SPACE THAT IS EQUIPPED
WITH POWER VENTILATION.
The confined space must communi-
cate with the outdoors according to
Methods 1 and 2. The minimum air
opening dimension shall not be less
than 3 inches. When using ducts,
they shall be of the same cross-
sectional area as the free area of the
openings to which they connect.
Method 1
Provide two permanent openings,
one located within 12 inches of the
top and one located within 12 inches
of the bottom of the enclosure. Each
opening shall communicate directly,
31