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CONTINUOUS FAN MODE:
"F" is displayed. This is then toggled
with two numbers which indicate the
CFM of the main circulating blower
divided by 100. For example, if "18" is
displayed, the furnace is attempting to
deliver 1800 CFM of air.
For example, if "F" is displayed followed
by "12" (toggling), this would indicate
that the system is in continuous fan
mode with the airflow operating at 1200
CFM.
FAULT PRESENT MODE:
When a fault is present, it is displayed
continuously and is not toggled with
another number. For example, if the
furnace loses flame sense unexpected-
ly, "13" is displayed continuously until
the fault clears.
24 VAC THERMOSTAT
(TSTAT) INPUTS (J4 & J6)
24 VAC THERMOSTAT (TSTAT)
INPUTS (E-115)
These connections are used with any tra-
ditional 24VAC one-stage or two-stage
thermostat or the modulating, non-com-
municating, thermostat specified for this
modulating furnace. Fully communicating
thermostats must be connected to the
COMM NETWORK CONNECTION (see
section titled COMMUNICATING SYS-
TEMS of this document for details).
Optimum heating performance will be
realized only with the fully modulating
thermostat (either communicating or non-
communicating).
W1, Y1, Y2, G, C and R are the tradition-
al thermostat inputs used in nearly all
HVAC equipment. Installation of the ther-
mostat to these connections is straight-
forward and simple.
HUM STAT – This terminal is used to
connect the output of a humidistat to the
furnace control to control humidification
and/or dehumidification. Optional equip-
ment is required for these features.
Please see the section titled HUMIDIFIC-
TION AND DEHUMIDIFICATION of this
document for more details.
V/W2 – This terminal is used to connect
the modulating signal (V) from a non-
communicating, fully modulating thermo-
stat specified for use with this furnace. It
is used to transmit the firing rate (deter-
mined by the thermostat) to the furnace
control. In addition, a traditional 24VAC
signal from a two-stage thermostat termi-
nal labeled "W2" can be connected to
this terminal to activate the timed staging
feature of this furnace.
Note: Do not apply 24vac to the V/W2
terminal (as with a jumper to R for diag-
nostic purposes) when a non-communi-
cating, modulating thermostat is installed.
B – This terminal is used to pass a
reversing valve signal to a condenser. It
is only a holding place for connecting a
wire from the thermostat and a wire from
the condenser. It does not change the
airflow of the cool/heat commands.
SPECIAL CONFIGURATION
– COMMUNICATING THER-
MOSTAT AND FURNACE
WITH A NON-
COMMUNICATING
CONDENSER
Y1 – This terminal may be used to con-
nect directly to a non-communicating
condenser when a communicating ther-
mostat is installed to the furnace but a
non-communicating condenser is
installed in the system. While the opti-
mum configuration is with a communi-
cating condenser connected to the net-
work, there may be installations where
this is not desired. In these cases, the
thermostat will be communicating with
the furnace control and the furnace
control will energize the condenser as
necessary (the additional relays have
been added to the furnace control to
allow this operation).
The thermostat connection labeled "Y1"
on the I.F.C. is normally an input to the
furnace control to turn on the blower
when they are energized. However, in
this configuration, this (normally) input
becomes an output to energize the
condenser when a cooling call has
been sent from the communicating
thermostat.
When this configuration is desired, use
the wiring diagram in Figure 38 to con-
nect the thermostat and condenser to
the furnace control.
NOTE: A heat pump condenser cannot
be installed with this configuration.
There is no control for the reversing
valve.
FUSE (F1)
A three-amp automotive-style (ATC
blade type) fuse is supplied on-board
the furnace control. This fuse should
provide protection from short-circuits on
the control board and associated 24
VAC wiring.
115 VAC TERMINALS
These terminals supply 115 VAC to the
furnace control from the input at the
junction box of the furnace.
Additionally, spare terminals are provid-
ed for use with electronic air cleaners
and other accessories as needed
(Check the voltage rating of your equip-
ment.)
INDUCED DRAFT MOTOR
(INDUCER) CONTROL OUT-
PUT (E8)
This four-pin connector is white in color
and provides control command to both
the high and low speed inducer out-
puts.
For troubleshooting purposes, follow
the wiring diagram and troubleshooting
flowchart supplied in this manual and
on the inside of the furnace blower
door. Additionally, the pin designations
for the connector are specified below:
Pin 1 to Inducer 12V
Pin 2 to Inducer Rx
Pin 3 to inducer GND
Pin 4 to inducer Tx
NEUTRAL TERMINALS
These terminals connect 115VAC
neutral to the furnace control from
the input at the junction box of the
furnace. Additionally, spare termi-
nals are provided for use with elec-
tronic air cleaners, humidifiers and
other accessories as needed (Check
the voltage rating of your equip-
ment.)
ELECTRONIC AIR
CLEANER (E.A.C.) OUT-
PUT (E-103)
This output is used to energize an
electronic air cleaner. The output
will provide 1.0 amp at 115 VAC.
This output is energized any time
the blower motor is above 40% of
maximum airflow capacity. Airflow
below this value is not considered to
be enough for a typical electronic air
cleaner to perform properly.
For 1/2HP motors – Electronic air
cleaner is energized any time the
blower is above 480 CFM (1200
CFM x 0.4)
For 1 HP motors - Electronic air
cleaner is energized any time the
blower is above 800 CFM (2000
CFM x 0.4)
HUMIDIFIER OUTPUT
(J8)
Details about the humidifier outputs
and wiring diagrams can be found in
the section titled HUMIDIFICATION
AND DEHUMIDIFICATION of this
document.
STEPPER GAS VALVE
CONTROL (E113)
For furnaces equipped with a step-
per modulating gas valve, a five-pin
connector is used to control and
sense the gas valve. The valve uses
a PWM (Pulse Width Modulated)
signal to control the firing rate. The
duty cycle of this signal is five per-
cent less than the expected firing
rate. For example, if the firing rate is
90%, the PWM to (and from) the
valve will be 85% duty cycle. The
connector also provides the 24VAC
signal to energize the main valve
solenoid. Reference the wiring dia-
gram for the furnace printed in this
document or on the inside of the fur-
nace blower door.
For troubleshooting purposes, follow
the wiring diagram and troubleshoot-
ing flowchart supplied in this manual
and on the inside of the furnace
blower door. Additionally, the pin
designations for the connector are
specified below:
Pin 1 to stepper modulating gas
valve connector Pin 1 (TH)
47
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Troubleshooting
