20
FURNACE
MODEL
NUMBER
FURNACE
INPUT
(BTUH)
CABINET
WIDTH
(IN.)
NOMINAL
ELECTRICAL
SUPPLY
MAXIMUM
OPERATING
VOLTAGE
MINIMUM
OPERATING
VOLTAGE
MAXIMUM
FURNACE
AMPERES
MAXIMUM
FUSE OR CIRCUIT
BREAKER AMPS*
*SD-050U-T23A
50,000
14 ¼
120-60-1
132
108
9.8
15
*SD-100U-T35C
100,000
21
120-60-1
132
108
12.5
20
* Time-delay fuses or circuit breakers are required.
THERMOSTAT WIRE GAUGE
RECOMMENDED THERMOSTAT WIRE LENGTH
2 - WIRE - HEATING
4 OR 5 WIRE - COOLING
24
55 ft.
25 ft.
22
90 ft.
45 ft.
20
140 ft.
70 ft.
18
225 ft.
110 ft.
Table 5. Wire Length & Voltage Specifications
Thermostat
Furnace
Control
Board
Condensing Unit
Control Box
C
Y1
Y2
Figure 20. Low Voltage Field, Four-wire
Heating/Cooling Applications
Figure 19. Line Voltage Field Wiring
Field Supplied
Disconnect within
Sight of Furnace
Field Supplied
Panel Connector
Field Supplied
Fused Service
Panel
Black (Hot)
White (Neutral)
Green or Bare (Ground)
Field Line Voltage Wiring
Factory Line Voltage Wiring
Ground
Ground
Junction Box (may be int. or ext. to the furnace). These connections can be made in the field supplied disconnect at the furnace.
NOTE:
Connections made within the furnace burner compartment do not require a junction box.
Ground
Black
White
Black
White
Black
White
START-UP & ADJUSTMENTS
Pre-Start Check List
√
Verify the polarity of the connections are correct, the line
voltage power leads are securely connected and the
furnace is properly grounded.
√
Verify the thermostat wires (
R
,
W
,
Y1
,
Y2
&
C
) are
securely connected to the correct leads on the terminal
strip of the circuit board.
√
Verify the air switches are wired correctly according to
√
Verify the gas line service pressure does not exceed 10.0
inches of W.C., and is not less than 4.5 inches W.C. for
natural gas.
√
DO NOT install a jumper wire across a switch to defeat
its function. If a switch reopens on startup, identify and
correct the fault condition.
√
Verify the blower door is in place, which closes the door
switch. This ensures line voltage gets to the blower motor.
√
Verify the gas line has been purged and all connections
are leak free.
Start-up Procedures
Do not perform these steps until all of the checks in the
previous steps have been completed:
1. Set the thermostat to the lowest setting.
2. Turn off all electrical power to the furnace.
3. Follow the Operating Instructions on the label attached to
the furnace.
4. Set the thermostat above room temperature and verify the
5. After 5 minutes of operation, set the thermostat below
room temperature and verify steps 9 - 10 of the Operating
Sequence.
