INSTALLATION INSTRUCTIONS
Gas Furnace: (F/G)9MVT, (F/G)9MXT, (F/G)9MXE
440 01 4001 05
33
Specifications subject to change without notice.
NOTE
: Use AWG No. 18 color-coded copper thermostat wire
for lengths up to 100 ft. (30.5 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
Figure 41
or
Figure 42
)
See the Service and Technical Support manual for detailed
instructions on control wiring and setup.
Thermostats and Control Settings for
(F/G)9MVT Variable Speed Furnaces
Communicating, single
−
stage and two
−
stage thermostats may
all be used with these furnaces. Refer to typical thermostat
wiring diagrams and the Sequence of Operation section of the
Service and Technical Support manual for details on
configuring the furnace control board. Consult the thermostat
installation instructions for specific information about
configuring the thermostat.
Thermostats and Control Settings for
(F/G)9MXT Two
−
Stage Furnaces
A single
−
stage or two
−
stage heating and single
−
stage or
two
−
stage cooling thermostat may be used with the furnace.
Refer to typical thermostat wiring diagrams and the Sequence
of Operation section of the Service and Technical Support
manual for details on configuring the furnace control board.
Consult the thermostat installation instructions for specific
information about configuring the thermostat.
Thermostats and Control Settings for
(F/G)9MXE Single
−
Stage Furnaces
A single stage heating and single
−
stage or two
−
stage cooling
thermostat may be used with the furnace. Refer to typical
thermostat wiring diagrams and the Sequence of Operation
section of the Service and Technical Support manual for details
on configuring the furnace control board. Consult the
thermostat installation instructions for specific information about
configuring the thermostat.
Accessories
(
See
Figure 39
,
Figure 40
,
Figure 41
,
and/or
Figure 42
)
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)
(F/G)9MVT
The HUM terminal is a 24 VAC output,
energized when the blower is operating during a call
for heat. (See
Figure 40
)
(F/G)9MXT
There are two humidifier outputs on the
furnace control. The 115 VAC HUM terminal is
energized when the Induced Draft Relay closes. The
24 VAC HUM terminal is energized when the low
pressure switch closes during a call for heat. Connect
an accessory 115 VAC accessory humidifier to the
HUM terminal and L2 on the furnace control. Connect
a 24 VAC humidifier to the 24 VAC HUM terminal and
C screw terminal strip on the control board thermostat
strip. (See
Figure 41
)
(F/G)9MXE
The HUM 24 VAC terminal is a 24 VAC
output energized when the gas valve relay closes
during a call for heat.
NOTE
: There is not a HUM 115V terminal on the single stage
ECM furnace control board. Available ONLY on the two
−
stage
ECM and PSC single
−
stage furnace control board.
Connect an accessory 24 VAC, 0.5 amp. Maximum (if
used) to the 1/4
−
in. male quick
−
connect HUM 24 VAC
terminal and C screw terminal on the control board
thermostat strip. (See
Figure 42
)
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 24 VAC and C screw terminal on the
control board thermostat strip. (See
Figure 39
)
3.
(F/G)9MVT
−
Communication Connector
This connection is used when the furnace is
controlled by an optional communicating wall control
instead of a standard thermostat. The communication
plug is supplied with the communicating wall control.
Refer to the instructions supplied with the
communicating wall control for complete details. (See
Figure 40
)
4.
(F/G)9MVT
−
Outside Air Thermistor (OAT)
The OAT connection is used in conjunction with
communicating wall control. It is not required when the
furnace is controlled by a standard type thermostat.
Refer to the instructions supplied with the
communicating wall control for complete details. (See
Figure 40
)
Alternate Power Supplies
This furnace is designed to operate on a 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 furnace electronics.
The alternate power supply must generate the same voltage,
phase, and frequency (Hz) as shown in
Table 11
or on the
furnace rating plate.
Power from an alternate power supply that non-sinusoidal may
damage the furnace or cause erratic furnace operation.
Contact the alternate power supply manufacturer for
specifications and details.
