Carrier 58PAV - Manual (Page 3)

I
Combustion air requirements are determined by whether
the fiunace is in an UNCONFINED or CONFINED space.
A confined space is a space whose volume is less than 50
cubic ft per 1000 Btu per hour of the total output rating for
aU appliances installed in that space.
A. Unconfined Space
An unconfined space must have at least 50 cubic ft for each
1000 Btuh of input for all the appliances (i.e. furnaces,
clothes dryer, water heaters, etc.) in the space.
For Example:
58PAV Furnace
Input Btuh
Minimum Sq Ft
with
7-1/2 Ft Ceiling
44,000 293
66,000 440
88,000 587
110,000 733
132,000 880
154,000 1026
If the unconfined space is of unusually tight construction,
air for combustion and ventilation MUST come from either
the outdoors or spaces freely communicating with the out­
doors. Combustion and ventilation openings must be sized
the same as for a confined space. A minimum opening hav­
ing a total of not less than 1 square in. per 5000 Btuh of
total input rating for all equipment must be provided.
Return air must not be taken from the room, unless an equal
or greater eimount of air is supplied to the room.
B. Confined Space
A confined space MUST have two permanent openings, one
within 12-ins. of the ceiLing, and the other within 12-ins. of
the floor. See Fig. 2.
NOTE: In deterniining the free area of an opening, the
blocking effect of the louvers, grilles and screens must be
considered. If the free area of a louver or grille design is
unknown, it may be assumed that wood louvers have a 20
percent free area and metal louvers or grilles have a 60 per­
cent free area. Screens, when used, must not be smaller than
1/4-in. mesh. Louvers and grilles must be constructed so
they cannot be closed.
The size of the openings depend upon whether the air comes
from inside or outside of the structure.
SUPPLY
AIR
r~Hn
VENT TO ROOF
12 MAX
^ 1 SQ INCH
PER 1000
I BTUH*
INTERIOR
HEATED
SPACE
-6 MIN
(FRONT)
A89012
♦Minimum opening size is 100 square ins.
tMinimum of 3 ins. when type-B vent is used.
Fig. 2
1. All air from inside the structure
Each opening MUST have at least 1 square in. of free
area per 1000 Btuh of the total input for all equipment
within the confined space, but not less than 100 square
ins. per opening. See Fig. 2.
For Example:
58PAV Furnace
Input Btuh
Free Area per Opening
(square ins.)
44,000 100
66,000 100
88,000 100
110,000 110
132,000 132
154,000 154
If the building is of unusually tight construction, a perma­
nent opening directly communicating with the outdoors
shall be provided. This opening shall have a minimum free
area of 1 square in. per 5000 Btuh of total input rating for
all equipment in the enclosure.
If the furnace is installed on a raised platform to provide a
return air plenum, and return air is taken directly from the
hallway or space adjacent to the furnace, aU air for combus­
tion must come from outdoors.
2. All air from outdoors
a. If combustion air is taken from outdoors through
vertical ducts, the openings and ducts MUST have
at least one square inch of free area per 4000 Btuh
of the total input for aU equipment within the con­
fined space. See Fig. 3.
For Example:
58PAV Furnace
input Btuh
Free Area per Opening
(square ins.)
Round Pipe
(ins. dia)
44,000 11.0 4
66,000 16.5 5
88,000 22.0 6
110,000 27.5 6
132,000 33.0 7
154,000 38.5 7
b. If combustion air is taken from the outdoors through
horizontal ducts, the openings and ducts MUST have
at least one square in. of free area per 2000 Btuh of the
DUCTS
TO ROOF-
1 so INCH PER
4000 BTUH
I'. ".I
MAX 12
1 SQ INCH PERT
2000 BTUH
DUCTS TO
OUTS DE
1 SQ INCH PER
2000 BTUH ^
MAX 12
SUPPLY D
AIR
A A VENT
T TO ROOF
A
RETURN AIR
j
i
2 MAX
1 SQ INCH
,^PER 4000
BTUH
DUCT
TO OUTSIDE
USE ANY OF THE FOLLOWING
COMBINATIONS
OF OPENINGS:
A&B C&D D&E
A89013
Fig-3