36
operation. Use only AWG No. 18, color--coded, copper thermostat
wire.
NOTE
: Use AWG No. 18 color-coded copper thermostat wire for
lengths up to 100 ft. (31 M). For wire lengths over 100 ft., use
AWG No. 16 wire.
The 24--v circuit contains an automotive--type, 3--amp. fuse located
on the control. Any direct shorts during installation, service, or
maintenance could cause this fuse to blow. If fuse replacement is
required, use ONLY a 3--amp. fuse of identical size. See Fig. 34.
Thermostats
For best results, use a communicating wall control to control this
modulating furnace. A single stage or two--stage heating and
cooling thermostat can be used with the furnace. The furnace
control board CPU will control the furnace and outdoor unit
staging. A two stage heating and cooling thermostat can also be
used to control the staging. However, full modulating capability
will not be available when the furnace staging is controlled by the
thermostat. Furnace staging will be limited to Minimum and
Maximum inputs or Intermediate and Maximum inputs depending
on the configuration of set-up switches SW1-2 and SW4-2. For
two stage thermostat control of a 2-stage outdoor unit, remove the
ACRDJ jumper from the furnace control board. Refer to typical
thermostat wiring diagrams and the Sequence of Operation section
for additional details. Consult the thermostat installation
instructions for specific information about configuring the
thermostat. See Fig. 34 and 35.
Accessories
(See Fig. 32 and 34.)
1. Electronic Air Cleaner (EAC)
Connect an accessory Electronic Air Cleaner (if used) using
1/4--in. female quick connect terminals to the two male
1/4--in. quick--connect terminals on the control board
marked EAC--1 and EAC--2. The terminals are rated for
115VAC, 1.0 amps maximum and are energized during
blower motor operation.
2. Humidifier (HUM)
The HUM terminal is a 24 VAC output, energized when the blower
is operating during a call for heat.
Connect an accessory 24 VAC, 0.5 amp. maximum humidifier (if
used) to the
¼
--in. male quick--connect HUM terminal and
COM--24V screw terminal on the control board thermostat strip.
NOTE
: If the humidifier has its own 24 VAC power supply, an
isolation relay may be required. Connect the 24 VAC coil of the
isolation relay to the HUM and COM/24V screw terminal on the
control board thermostat strip. See Fig. 32.
3. Communication Connector (communication connection)
This connection is used when the furnace is controlled by
an optional communicating User Interface instead of a
standard thermostat. The communication plug is supplied
with the User Interface. Refer to the instructions supplied
with the User Interface for complete details. See Fig. 34.
4. Outside Air Thermistor (OAT)
The OAT connection is used in conjunction with commu-
nicating User Interface. It is not required when the furnace
is controlled by a standard type thermostat. Refer to the in-
structions supplied with the User Interface for complete de-
tails.
Alternate Power Supplies
This furnace is designed to operate on utility generated power
which has a smooth sinusoidal waveform. If the furnace is to be
operated on a generator or other alternate power supply, the
alternate power supply must produce a smooth sinusoidal
waveform for compatibility with the furnace electronics. The
alternate power supply must generate the same voltage, phase, and
frequency (Hz) as shown in Table 11 or the furnace rating plate.
Power from an alternate power supply that is non-sinusoidal may
damage the furnace electronics or cause erratic operation.
Contact the alternate power supply manufacturer for specifications
and details.
Table 11 – Electrical Data
MODULATING
UNIT SIZE
VOLTS---
HERTZ---
PHASE
OPERATING VOLTAGE
RANGE*
MAXIMUM
UNIT
AMPS
UNIT
AMPACITY#
MINIMUM
WIRE
SIZE
AWG
MAXIMUM
WIRE
LENGTH
FT (M)
}
MAXIMUM
FUSE OR CKT
BKR
AMPS
{
Maximum* Minimum*
42060
115---60---1
127
104
9.7
12.7
14
29 (8.8)
15
60060
115---60---1
127
104
14.8
19.1
12
30 (9.1)
20
42080
115---60---1
127
104
9.7
12.7
14
29 (8.8)
15
60080
115---60---1
127
104
14.8
19.1
12
30 (9.1)
20
66100
115---60---1
127
104
14.8
19.1
12
30 (9.1)
20
66120
115---60---1
127
104
14.8
19.1
12
30 (9.1)
20
* Permissible limits of the voltage range at which the unit operates satisfactorily.
# Unit ampacity = 125 percent of largest operating component’s full load amps plus 100 percent of all other potential operating components’ (EAC, humidifier,
etc.) full load amps.
{
Time---delay type is recommended.
}
Length shown is as measured one way along wire path between furnace and service panel for maximum 2 percent voltage drop.
987MA
