General Requirements; Ductwork Acoustical Treatment; Supply Ai; Return Air Connections - Carrier 58MXA Installation, Start-Up, And Operating Instructions Manual

angle iron s_/pports (See Fig. 22.) Cut hanger bolts (4 each 3/8=in.
all=thread rod) to desired tength. Use 1 X 3/8=in flat washers,
3/8-in. tock washers, and 3/8=in nuts on hanger rods as shown in
Fig 22. Dimples are provided fbr hole locations. (See Fig 2)
if constructed and installed in accordance with the latest edition of
SMAENA construction 18 standard on fibrous glass ducts. Both
acoustical lining and fibrous ductwork shall comply with NFPA
90B as tested by EL Standard 18! for (?lass 1 Rigid air ducts.
DISCHARGE DUCT
FLANGE
210°
MIN
NO
YES
YES
A93029
Fig. 21--Duct Flanges
Step 4--Air Duets
GENERAL REQUIREMENTS
The duct system should be designed and sized according to
accepted national standards such as those published by: Air
Conditioning Contractors Association (ACCA), Sheet Metal and
Air Conditioning ContIactors National Association (SMACNA) or
American Society of Heating, Refrigerating and Air Conditioning
Engineers (ASHRAE) or consult
Fhe Air 51v,ste_s Desiglv
G_ide-
trees rel:_rence rabies available fiom your local distributor. The
duct system should be sized to handle the required system design
CFM at the design static pressure.
When a furnace is installed so that the supply ducts catty- air
circulated by the t:urnace to areas outside the space containing the
Nrnace, the return air shall also be handled by a duct(s) sealed to
the furnace casing and tem_inating outside the space containing the
furp, ace
Secure ductwork with proper fasteners for type of ductwork used.
Seal supply- and return-duct connections to furnace with code
approved tape or duct sealer.
Flexible connections should be used between ductwork and
furnace to prevent tlansmission of vibration. Ductwork passing
through unconditioned space should be insulated to enhance
system performance. When air conditioning is used, a vapor
battier is recommended.
Maintain a l-in. clearance fi'om combustible materials to supply air
ductwork for a distance of 36=in. horizontally fiom the furnace.
See NFPA 90B or local code fbr further requirements.
For a fhmace not equipped with a cooling coil, the outlet duct shall
be provided with a removable access panel. This opening shall be
accessible when the t:urnace is installed and shall be of such a size
that the heat exchanger can be viewed fbr possible openings using
light assistance or a probe can be inserted for sampling the air
stream. The cover attachment shall prevent leaks.
DUCTWORK ACOUSTIE AL 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 aheraative, fibrous ductwmk may be used
SUPPLY AIR CONNECTIONS
Upflow Furnaces
Connect supply=air duct to 3/4-in. flange on furnace supply-air
outlet. The supply=air duct attachment must be connected to
ONLY fhmace supply-/outlet=air duct flanges or air conditioning
coil casing (when used) DO NOT cut main fhmace casing to
attach supply side air duct, humidifier, or other accessories All
accessories MUST be connected external to furnace main casing.
Downflow Furnaces
(onnect supply-air duct to supply-air opening on fllrnace. The
supply-air duct attachment must be connected to ONLY fhrnace
supply/outlet or air conditioning coil casing (when used), when
installed on non=combustible material. When installed on combus-
tible material, supply=air duct attachment must be connected to
ONLY an accessory subbase or Pactory approved air conditioning
coil casing. D() NOT cut main furnace casing to attach supply side
air duct, humidifier, or other accessories. All accessories MUST be
connected external to furnace main casing. Supply air opening duct
flanges must be modified per Fig. 21.
Horizontal Furnaces
Connect supply=air duct to supply air opening on furnace. The
supply-air duct attachment must be connected to ONLY fhmace
supply/outlet or air conditioning coil casing {when used). DO NOT
cut main furnace casing to attach supply side air duct, humidifier,
or other accessories. All accessories MUST be connected external
to fhrnace main casing.
RETURN AIR CONNECTIONS
The furnace and its return air system shall be designed and
installed so that negative pressure created by the air circulating fan
cannot affect another appliance's combustion air supply or act to
mix products of combustion with circulating air. The air circulat-
ing fhn of the furnace, if installed in an enclosure communicating
with another filel=buming appliance not of the direct=vent type,
shall be operable only when any door or panel covering an opening
in the fhmace fhn compartment or in a return air plenum on ducts
is in the closed position.
FIRE HAZARD
A failure to _bltow this warning could result in fire, personal
injury, or death.
Never connect return=air ducts to d_e back of the _hmace.
Return=air duct connections on furnace side{s) peimitted in
upflow applications only
Upflow Furnaces
The return-air duct mttst be connected to bottom, sides (le_:_ or
right), or a congbination of bottom and side(s) of main furnace
casing as shown in Fig. 2. Bypass humidifier may be attached into
unused side return air portion of the furnace casing DO NOT
connect any portion of return=air duct to back of furnace casing
Downflow and Horizontal Furnaces
The return=air duct must be connected to end inlet opening
provided as shown in Fig. 2. DO NOT cut into casing sides or back
to attach any portion of return-air duct. Bypass humidifier connec-
tions should be made at ductwork or coil casing sides exterior to
furnace
17