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 sq in. with
minimum dimensions of 3 in.
†
Minimum of 3 in. when type-B1 vent is used.
Fig. 3—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 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 furnace cabinet
and return-air duct to prevent pulling air from 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 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 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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OUTDOORS
12" MAX
1 SQ IN.
PER 2000
BTUH*
DUCTS
TO
OUTDOORS
1 SQ IN.
PER 2000
BTUH*
12" MAX
RETURN AIR
*Minimum dimensions of 3 in.
NOTE: Use any of the following
combinations of openings:
A & B
Fig. 4—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 defined as a space whose volume is 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 combustion, ventilation, and dilution of flue
gases using 1 of the following methods. (See Fig. 3 and Table 2.)
NOTE: In determining free area of an opening, the blocking
effect of louvers, grilles, and screens must be considered. If free
area of louver or grille design is unknown, assume 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.
5
1 SQ IN.
PER 4000
DUCTS
BTUH*
TO
D
VENT
A
THROUGH
F
SUPPLY ROOF
AIR
E
G
B
C
12" MAX
DUCT
1 SQ IN.
TO
PER 4000
OUTDOORS
BTUH*
C & D 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
4000
BTUH*
1 SQ IN.
PER
4000
BTUH*
12"
MAX
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