Carrier 58TUA - Manual (Page 4)

For Example:
58TUA FURNACE
HIGH FIRE INPUT BTUH
MINIMUM SQ FT WITH
7-1/2 FT CEILING
40,000 267
60,000 400
80,000 534
100,000 667
120,000 800
140,000 934
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 outdoors. Combustion
and ventilation openings must be sized the same as for a confined
space as defined below. Return air must not be taken from the
room unless an equal or greater amount of ait is supplied to the
room.
CONFINED SPACE
A confined space MUST have 2 permanent openings, 1 within 12
in. of the ceiling, and the other within 12 in. of the floor. (See Fig.
2 .)
NOTE: In determining 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 percent 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.
SUPPLY
AIR
VENT THROUGH ROOF
(CATEGORY 1) OR WALL
(CATEGORY 111)
~r~
_12MAX
Q_i
1 SO IN.
Щ PER 1000
BTUH*
INTERIOR
HEATED
SPACE
6 IN. MIN
(FRONT) t
1 SO IN.
PER 1000
BTUH*
* Minimum opening size is 100 square in. with
minimum dimensions of 3 in.
1 Minimum of 3 in. when type-B vent is used.
A89012
Fig. 2—Air For Combustion and Ventiiation
(inside Air)
The size of the openings depends upon whether the air comes from
inside or outside of the structure.
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 in. per opening.
(See Fig. 2.) The minimum dimension of air openings shall be
not less than 3 in.
For Example:
58TUA FURNACE
HIGH FIRE INPUT
BTUH
FREE AREA OPEN­
ING (SQUARE IN.)
40,000 100
60,000 100
80,000 100
100,000 100
120,000 120
140,000 140
If the building is constructed unusually tight, a permanent opening
directly communicating with the outdoors should 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, all air for combustion 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 1 square
in. of free area per 4000 Btuh of the total input for all
equipment within the confined space. (See Fig. 3.)
For Example:
58TUA FURNACE
HIGH FIRE INPUT
BTUH
FREE AREA PER
OPENING
(SQUARE IN.)
ROUND PIPE
(IN. DIA)
40,000 10.0 4
60,000 15.0 5
80,000 20.0 6
100,000 25.0 6
120,000 30.0 7
140,000 35.0 7
b. If combustion air is taken from the outdoors through
horizontal ducts, the openings and ducts MUST have at
least 1 square in. of free area per 2000 Btuh of the total
input for all equipment within the confined space. (See Fig.
3)
For Example:
58TUA FURNACE
HIGH FIRE INPUT BTUH
FREE AREA PER OPENING
(SQUARE IN.)
ROUND PIPE
(IN. DIA)
40,000 20.0 6
60,000 30.0 7
80,000 40.0 8
100,000 50.0 8
120,000 60.0 9
140,000 70.0 10
When ducts are used, they must be of the same cross-sectional area
as the free area of the openings to which they connect. The
minimum dimension of rectangular ducts must not be less than 3
in. (See Fig. 3.)