Carrier 58TMA - Unconfined Space; Confined Space

Canadian installations must be in accordance with NSCNGPIC
and all authorities having jurisdiction.
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.
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.
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 avoid pulling air from the burner
area and draft safeguard opening into the circulating air.
The requirements for combustion and ventilation air depend upon
whether the furnace is located in a CONFINED or UNCONFINED
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.
For Example:
58TMA FURNACE
HIGH-FIRE INPUT
BTUH
MINIMUM SQ FT
WITH
7-1/2 FT CEILING
63,000 420
84,000 560
105,000 700
123,000 820
If the unconfined space is constructed unusually tight, 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 the total input ratings of 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.)
Fig. 2—Confined Space: Air for Combustion and
Ventilation from an Unconfined Space
A93387
RETURN
AIR
6″ MIN
(FRONT)
†
SUPPLY AIR
VENT THROUGH ROOF
(CATEGORY I)
1 SQ IN.
PER 1000
BTUH
*
IN DOOR
OR WALL
12″ MAX
1 SQ IN.
PER 1000
BTUH
*
IN DOOR
OR WALL
12″ MAX
INTERIOR
HEATED
SPACE
* Minimum opening size is 100 square in. with
minimum dimensions of 3-In.
†
Minimum of 3-In. when type B-1 vent is used.
UNCONFINED
SPACE
Fig. 3—Confined Space: Air for Combustion and
Ventilation from Outdoors
A93388
DUCTS TO
OUTDOORS
1 SQ IN.
PER 4000
BTUH
*
RETURN
AIR
VENT
THROUGH
ROOF
(CATEGORY I)
D
B
A
C
E
1 SQ IN.
PER 4000
BTUH
DUCT
TO
OUTDOORS
SUPPLY AIR
1 SQ IN.
PER 2000
BTUH
*
DUCTS
TO
OUTSIDE
12″ MAX
12″ MAX
CONFINED
SPACE
12″
MAX
12″
MAX
1 SQ IN.
PER 4000
BTUH
*
OUTDOORS
1 SQ IN.
PER 4000
BTUH
*
1 SQ IN.
PER 2000
BTUH
*
12″ MAX
Use any of the following
combinations of openings:
A & B C & D D & E F & G
NOTE:
*
Minimum dimensions of 3-In.
F
G
4