Air Ducts; General Requirements; Ductwork Acoustical Treatment; Supply Air Connection - Carrier 58UHV Installation, Start-Up, And Operating Instructions Manual

AIR FROM INDOOR
58UHV/58UXV
UNCONFINED SPACE
FURNACE
HIGH-FIRE
Free Area
INPUT
of Opening
(BTUH)
60,000
80,000
100,000
117,000
* 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.
2. Air from outside the structure requires 1 of the following
methods:
a. If combustion air is taken from outdoors through 2 vertical
ducts, the openings and ducts MUST have at least 1 sq in.
of free area per 4000 Btuh of total input for all equipment
within the confined space. (See Fig. 4 and Table 2.)
b. If combustion air is taken from outdoors through 2 hori-
zontal ducts, the openings and ducts MUST have at least 1
sq in. of free area per 2000 Btuh of total input for all
equipment within the confined space. (See Fig. 4 and Table
2.)
c. If combustion air is taken from outdoors through a single
opening or duct (horizontal or vertical) commencing within
12 in. of the top of the confined space, opening and duct
MUST have at least 1 sq in. of free area per 3000 Btuh of
the total input for all equipment within the confined space
and not less than the sum of the areas of all vent connectors
in the confined space. (See Fig. 4 and Table 2.) Equipment
clearances to the structure shall be at least 1 in. from the
sides and back and 6 in. from the front of the appliances.
When ducts are used, they must be of the same cross-sectional area
as the free area of the openings to which they connect. The
minimum dimension of ducts must not be less than 3 in. (See Fig.
4.)
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Step 3—Air Ducts

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 Contractors National Association (SMACNA) or
American Society of Heating, Refrigerating and Air Conditioning
Engineers (ASHRAE) or consult factory The Air Systems Design
Guidelines reference tables available from your local distributor.
The duct system should be sized to handle the required system
design airflow CFM at the design external static pressure.
When a furnace is installed so that the supply ducts carry air to
areas outside the space containing the furnace, the return air must
also be handled by a duct(s) sealed to the furnace casing and
terminating outside the space containing the furnace.
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 transmission of vibration. Ductwork passing
through unconditioned space should be insulated to enhance
system performance. When air conditioning is used, a vapor
barrier is recommended.
Maintain a 1-in. clearance from combustible materials to supply air
ductwork for a distance of 36 in. horizontally from the furnace. See
NFPA 90B or local code for further requirements.
Table 2—Minimum Free Area Of Combustion Air Opening*
OUTDOOR AIR THROUGH
VERTICAL DUCTS
Free Area of
Opening and Duct
(Sq In.) (Sq In.)
100 15.0
100 20.0
100 25.0
117 29.3
OUTDOOR AIR THROUGH
HORIZONTAL DUCTS
Round Free Area of
Pipe Opening and Duct
(In. Dia) (Sq In.)
5 30.0
6 40.0
6 50.0
7 58.5

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.
SUPPLY AIR CONNECTIONS
1. Upflow Furnace
Connect supply-air duct to 3/4-in. flange on furnace supply-air
opening outlet. The supply-air duct attachment must ONLY be
connected to furnace supply/outlet 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
accessories MUST be connected external to furnace main
casing.
2. Horizontal Furnaces
Connect supply-air duct to 3/4-in. flange on supply air opening
on furnace. The supply-air duct attachment must ONLY be
connected to furnace 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 furnace main
casing.

RETURN AIR CONNECTIONS

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Never connect return-air ducts to back of furnace. A failure to
follow this warning can cause a fire, personal injury, or death.
1. Upflow Furnaces
The return-air duct must be connected to bottom, sides (left or
right), or a combination of bottom and sides(s) of main furnace
casing as shown in Fig. 1. 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.
2. Horizontal Furnaces
The return-air duct must be connected to return-air opening
provided as shown in Fig. 1. DO NOT cut into casing sides or
back to attach any portion of return-air duct. Bypass humidifier
connections should be made at ductwork or coil casing sides
exterior to furnace.
6
OUTDOOR AIR THROUGH
SINGLE DUCT
Round Free Area of
Pipe Opening and Duct
(In. Dia) (Sq In.)
7 20.0
8 26.7
8 33.4
9 39.0
Round
Pipe
(In. Dia)
6
6
7
8