Unconfined Space; Confined Space - Carrier 58TUA Installation, Start-Up, And Operating Instructions Manual

SUPPLY
AIR
INTERIOR
HEATED
SPACE
RETURN AIR
* Minimum opening size is 100 square in. with
minimum dimensions of 3-In.
†
Minimum of 3-In. when type-B1 vent is used.
Fig. 2—Confined Space: Air for Combustion and
Ventilation from an Unconfined Space
Air for combustion must not be contaminated by halogen
compounds, which include fluoride, chloride, bromide, and
iodide. These elements are found in aerosol sprays, deter-
gents, bleaches, cleaning solvents, salts, air fresheners, and
other household products.
All fuel-burning equipment must be supplied with air for combus-
tion of the fuel. Sufficient air MUST be provided to ensure there
will not be a negative pressure in the equipment room or space. In
addition, a positive seal MUST be made between the furnace
cabinet and the return-air duct to prevent pulling air from the
burner area and draft safeguard opening into the circulating air.
The operation of exhaust fans, kitchen ventilation fans,
clothes dryers, or fireplaces could create a negative air
pressure condition at the furnace. Make-up air must be
provided for these devices, in addition to that required by the
furnace.
Combustion air requirements are determined by whether the
furnace is in an UNCONFINED or CONFINED space.

UNCONFINED SPACE

An unconfined space must have at least 50 cu ft for each 1000
Btuh of input for all the appliances (such as furnaces, clothes
dryer, water heaters, etc.) in the space.
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
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DUCTS
OUTDOORS
12 " MAX
1 SQ IN.
PER 2000
A
SUPPLY
BTUH *
DUCTS
TO
OUTDOORS
1 SQ IN.
PER 2000
B
BTUH *
12 " MAX
RETURN AIR
* Minimum dimensions of 3-In.
NOTE: Use any of the following
combinations of openings:
A & B C & D
Fig. 3—Confined Space: Air for Combustion and
Ventilation from Outdoors
For Example:
58TUA FURNACE HIGH-FIRE
INPUT BTUH
40,000
60,000
80,000
100,000
120,000
133,000
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 air is supplied to the
room.

CONFINED SPACE

A confined space is one whose volume is less than 50 cu ft per
1000 Btuh of the total input rating for all appliances installed in
that 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
which freely communicate with an unconfined space or the
outdoors. (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.
4
1 SQ IN.
PER 4000
BTUH *
TO
D
VENT
THROUGH
F
ROOF
AIR
E
G
C
12 " MAX
DUCT
1 SQ IN.
TO
PER 4000
OUTDOORS
BTUH *
D & E F & G
MINIMUM SQ FT WITH 7-1/2 FT
CEILING
267
400
534
667
800
887
12"
MAX
1 SQ IN.
PER 5000
BTUH *
1 SQ IN.
PER 5000
BTUH *
12"
MAX
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