DISCHARGE DUCT
FLANGE
NO
Fig. 21--Duct Flanges
A93029
When a furnace is instal!ed so that the supply ducts catty air
circulated by the f_trnace to areas outside the space containing the
furnace, the return air shal! also be handled by a duct(s) sealed to
the _\u'nace casing and tem_inating outside the space containing the
]._tlrllace.
Secure ductwork with proper f_steners fbr type of ductwork use&
Seal supply- and return-duct connections to furnace with code
approved tape or duct sealer.
Flexible connecfions should be used between ductwork arid
furnace to prevent transmission of vibration. Ductwork passing
through unconditioned space should be insulated to enhance
system perfbm_ance. When air conditioning is used, a vapor
barrier is recommended.
Maintain a 1=in. clearance f)om combustible materials to supply air
ductwork for a distance of 36-in. horizontally fi'om the fhmace.
See NFPA 90B or local code fbr further requirements.
For a f:urnace not equipped with a cooling coil, the outlet duct shall
be provided with a removable access panel. This opening shal! be
accessible when the fi/mace is installed arid shall be of such a size
that d_e heat exchanger can be viewed fbr possible openings using
light assistance or a probe can be inserted fbr sampling the air
stream. The cover attachment shall prevent leaks.
DUCTWORK AC()USTICAL 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
SMA(NA construction standard on fibrous glass ducts. Both
aconsficai lining and fibrous ductwork shall comply with NFPA
90B as tested by UL Standard 18! for (?lass 1 Rigid air ducts.
II
II
II
II
s/8-1N.ROD
ANGLE
IRON OR
EQ
53/4_
(B)
(A) ROD LOCATION
USING DIMPLE
LOCATORS
(SEE DIMENSIONAL 3/8-1N.
DWG FOR & WASHER (4)
LOCATIONS) REQD PER ROD
I
l
I
A:: MAX
(B) ALTERNATE SUPPORT
LOCATION FROM BACK
(A) PREFERRED ROD LOCATION
(B) ALTERNATE ROD LOCATION
NOTES: 1. A 1 In. clearance minimum between top of
furnace and combustible material.
2. The entire length of furnace must be
supported when furnace is used in horizontal
position to ensure proper drainage.
Fig. 22--Crawispace HorizontN Application
17
ALTERNATE SUPPORT
LOCATION 4-IN. MIN
8-IN. MAX
A93304
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