Confined Space - Carrier 58CVA Installation, Start-Up, Operating And Service And Maintenance Instructions

ventilation openings must be equivalent to those used for a
confined space (defined below). Return air must not be taken from
the room unless an equal or greater amount of air is supplied to the
room.
Step 2—Confined Space
A confined space has a volume less than 50 cu ft per 1000 Btuh
of total input ratings of all appliances installed in that space. A
confined space must have provisions for supplying air for com-
bustion, ventilation, and dilution of flue gases using one of the
following methods in Table 2 and Fig. 7 and 8.
NOTE: When determining the free area of an opening, the
blocking effect of louvers, grilles, and screens must be considered.
If the free area of the louver or grille design is unknown, assume
wood louvers have a 20 percent free area and metal louvers or
grilles have a 60 percent free area. Screens must not be smaller
than 1/4-in. mesh. Louvers and grilles must be constructed so they
cannot be closed.
AIR
DUCTS
INTERIOR
HEATED
SPACE
AIR DUCTS
* Minimum opening size is 100 sq in. with
minimum dimensions of 3 in.
†
Minimum of 3 in. when type-B1 vent is used.
Fig. 7—Confined Space: Air for Combustion and
Ventilation from an Unconfined Indoor Space
The opening size depends upon whether air comes from outside of
the structure or an unconfined space inside the structure.
1. Air from inside the structure requires 2 openings (for struc-
tures not of unusually tight construction):
a. Each opening must have a minimum free area of not less
than 1 sq in per 1000 Btuh of total input rating for all gas
utilization equipment in the confined space, but not less
than 100 sq in. The minimum dimension of air openings
should be no smaller than 3 in. (See Table 2 and Fig. 7.)
VENT THROUGH ROOF
12" MAX
1 SQ IN.
PER 1000
BTUH * IN DOOR
OR WALL
UNCONFINED
SPACE
6 " MIN
†
(FRONT)
1 SQ IN.
PER 1000
BTUH * IN DOOR
OR WALL
12" MAX
A02038
7
DUCTS
TO
OUTDOORS
12 " MAX
1 SQ IN.
A
PER 2000
BTUH * AIR
DUCTS
DUCTS
TO
OUTDOORS
1 SQ IN.
B
PER 2000
BTUH *
12 " MAX
AIR DUCTS
* Minimum dimensions of 3 in.
NOTE: Use any of the following
combinations of openings:
A & B C & D D & E
Fig. 8—Confined Space: Air for Combustion and
Ventilation from Outdoors
b. If building construction is unusually tight, a permanent
opening directly communicating with the outdoors shall be
provided. (See next section).
c. 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 furnace, all air for combustion
must come from outdoors.
2. Air from outside the structure requires 1 of the following:
a. If combustion air is taken from outdoors through 2 vertical
ducts, the openings and ducts must have at least 1 sq in. of
free area per 4000 Btuh of total input for all equipment
within the confined space. (See Fig. 8 and Table 2.)
b. If combustion air is taken from outdoors through 2 hori-
zontal ducts, the openings and ducts must have at least 1 sq
in. of free area per 2000 Btuh of total input for all
equipment within the confined space. (See Fig. 8 and Table
2.)
c. If combustion air is taken from the outdoors through a
single opening or duct (horizontal or vertical) commencing
within 12 in. of the top of the confined space, the opening
and duct must have at least 1 sq in. of free area per 3000
Btuh of the total input for all equipment within the confined
space and not less than the sum of the areas of all vent
connectors in the confined space. Equipment clearances to
1 SQ IN.
PER 4000
BTUH *
D
12"
MAX
VENT
THROUGH
F
ROOF
1 SQ IN.
PER
4000
BTUH*
1 SQ IN.
PER
4000
BTUH*
E
G
12"
MAX
C
12 " MAX
DUCT
1 SQ IN.
TO
PER 4000
OUTDOORS
BTUH *
F & G
A02165