Ductwork Acoustical Treatment; Air Ducts; Supply Air Connections; Return Air Connections - Carrier 58MCA Installation, Start-Up, And Operating Instructions Manual

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.
Step 2—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.
Step 3—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 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.
DOWNFLOW FURNACES
Connect supply-air duct to 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), when
installed on non-combustible material. When installed on combus-
tible material, supply-air duct attachment must ONLY be con-
nected to an accessory subbase or factory approved air condition-
ing coil casing. 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.
HORIZONTAL FURNACES
Connect supply-air duct to 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.
BLOWER DOOR SWITCH
BLK BLK
WHT WHT
GND
115-V FIELD-
SUPPLIED
DISCONNECT
NOTE 2
W C
FIVE WIRE
THREE-WIRE
HEATING-ONLY
W
C
R
O
N
T
GND
R G
AUXILIARY
O
J-BOX
COM
L
Y
24-V
TERMINAL
BLOCK
NOTES:
FURNACE
Fig. 22—Heating and Cooling Application Wiring Diagram
Step 4—Return Air Connections
UPFLOW FURNACES
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
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 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 connec-
tions should be made at ductwork or coil casing sides exterior to
furnace.
See Fig. 22 for field wiring diagram showing typical field 115-v
and 24-v wiring. Check all factory and field electrical connections
for tightness.
Blower access panel door switch opens 115-v power to
control center. No component operation can occur. Do not
bypass or close switch with panel removed. Failure to follow
this warning could result in personal injury or death.
Furnace control must be grounded for proper operation or
control will lock out. Control is grounded through green wire
routed to gas valve and burner box screw.
Step 1—115-v Wiring
Before proceeding with electrical connections, make certain that
voltage, frequency, and phase correspond to that specified on unit
rating plate. Also, check to be sure that service provided by utility
is sufficient to handle load imposed by this equipment. Refer to
rating plate or Table 4 for equipment electrical specifications.
Make all electrical connections in accordance with National
Electrical Code (NEC) ANSI/NFPA 70-1999 and any local codes
or ordinances that might apply. For Canadian installations, all
electrical connections must be made in accordance with Canadian
Electrical Code CSA C22.1 or subauthorities having jurisdiction.
FIELD 24-V WIRING
FIELD 115-, 208/230-, 460-V WIRING
FACTORY 24-V WIRING
FACTORY 115-V WIRING
THERMOSTAT
R G Y
TERMINALS
NOTE 1
CONDENSING
UNIT
TWO
WIRE
1. Connect Y-terminal in furnace as shown for proper blower operation.
2. Some thermostats require a "C" terminal connection as shown.
3. If any of the original wire, as supplied, must be replaced, use
same type or equivalent wire.
18

ELECTRICAL CONNECTIONS

FIELD-SUPPLIED
DISCONNECT
208/230- OR
460-V
THREE
PHASE
208/230-V
SINGLE
PHASE
GND
A99408