II.
DUCTWORK ACOUSTICAL TREATMENT
Metal duct systems that do not have a 90 degree elbow and 10 ft
of main duct to the first branch take-off may require internal
acoustical lining. As an alternative, fibrous ductwork may be used
if constructed and installed in accordance with the latest edition of
SMACNA construction standard on fibrous glass ducts. Both
acoustical lining and fibrous ductwork shall comply with NFPA
90B as tested by UL Standard 181 for Class 1 Rigid air ducts.
III.
SUPPLY AIR CONNECTIONS
Connect supply-air duct to 3/4-in. flange on furnace supply-air
outlet. The supply-air duct attachment must ONLY be connected
to furnace supply-/outlet-air duct flanges or air conditioning coil
casing (when used). DO NOT cut main furnace casing to attach
supply side air duct, humidifier, or other accessories. All accesso-
ries MUST be connected external to furnace main casing.
IV.
RETURN AIR CONNECTIONS
WARNING:
Never connect return-air ducts to the back
of the furnace. A failure to follow this warning can cause
a fire, personal injury, or death.
The return-air duct must be connected to bottom , sides (left or
right), or a combination of bottom and side(s) of main furnace
casing as shown in Fig. 1. Bypass humidifier may be attached into
Fig. 3—Confined Space: Air For Combustion and Ventila-
tion from an Indoor Unconfined Space
A89012
SUPPLY
AIR
6
″
MIN
(FRONT)
†
RETURN AIR
VENT THROUGH ROOF
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 sq in. with
minimum dimensions of 3 in.
†
Minimum of 3 in. when type-B1 vent is used.
UNCONFINED
SPACE
CONFINED
SPACE
Fig. 4—Confined Space: Air For Combustion and Ventila-
tion from Outdoors
A89013
1 SQ IN.
PER
4000
BTUH*
DUCTS
TO
OUTDOORS
1 SQ IN.
PER 4000
BTUH*
SUPPLY
AIR
VENT
THROUGH
ROOF
D
B
A
C
E
1 SQ IN.
PER 4000
BTUH*
DUCT
TO
OUTDOORS
RETURN AIR
1 SQ IN.
PER 2000
BTUH*
1 SQ IN.
PER 2000
BTUH*
DUCTS
TO
OUTDOORS
12
″
MAX
12
″
MAX
12
″
MAX
Use any of the following
combinations of openings:
A & B C & D D & E F & G
NOTE:
*
Minimum dimensions of 3 in.
CONFINED
SPACE
12
″
MAX
12
″
MAX
OUTDOORS
1 SQ IN.
PER
4000
BTUH*
F
G
→
TABLE 2—MINIMUM FREE AREA OF COMBUSTION AIR OPENING
383KAV
FURNACE
INPUT
(BTUH)
AIR FROM INDOOR
UNCONFINED SPACE
OUTDOOR AIR THROUGH
VERTICAL DUCTS
OUTDOOR AIR THROUGH
HORIZONTAL DUCTS
OUTDOOR AIR THROUGH
SINGLE DUCT
Free Area
of Opening
(Sq In.)
Free Area of
Opening and Duct
(Sq In.)
Round
Pipe
(In. Dia)
Free Area of
Opening and Duct
(Sq In.)
Round
Pipe
(In. Dia)
Free Area of
Opening and Duct
(Sq In.)
Round
Pipe
(In. Dia)
44,000
100
11.0
4
22.0
6
14.67
5
66,000
100
16.5
5
33.0
7
22.00
6
88,000
100
22.0
6
44.0
8
29.33
7
110,000
110
27.5
6
55.0
9
36.67
7
132,000
132
33.0
7
66.0
10
44.00
8
154,000
154
38.5
8
77.0
10
51.33
9
* Free area shall be equal to or greater than the sum of the areas of all vent connectors in the confined space. Opening area must be increased, if other gas appliances
in the space require combustion air.
—6—
Содержание GAS-FIRED INDUCED-COMBUSTION FURNACES 383KAV
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