18-CE07D1-1C-EN
43
Sequence of Operation
E
EA
AC
C a
an
nd
d H
HU
UM
M T
Tiim
miin
ng
g
•
EAC relay closes when the blower motor starts in
any mode of operation.
•
EAC relay opens when the blower motor stops.
•
HUM relay closes on a gas heating call when the
blower motor starts and flame is sensed.
•
HUM relay opens when flame is no longer sensed, i.
e. thermostat is satisfied.
N
No
otte
e:: The EAC and HUM terminals are powered with
line voltage.
G
Ga
ass H
He
ea
attiin
ng
g
1. R – W contacts close on the thermostat sending
24VAC to the W low voltage terminal of the IFC.
Technician should read 24VAC from W to C. The
LED will flash GREEN one time per second.
2. The IFC performs a self-check routine and then
confirms that the:
a. Main thermal limit (HI LIMIT), and reverse air
flow (RAF) switches are closed by sending
24VAC out of the HLO terminal and monitoring
the HLI input.
b. Burner box thermal switch (BBOX LIMIT) is
closed by sending 24VAC out of the ROO
terminal and monitoring the ROI input.
3. After steps a & b are confirmed, the inducer
constant torque motor is energized and begins the
Pressure Sensor Verification.
a. The first check is to make sure the transducer
feedback is “null” or zero.
b. The second check is to make sure that the
transducer feedback span is within specification.
The inducer will engage to test the pressure
transducer response.
c. Upon successful completion of steps a & b, the
inducer will start the pre-purge.
N
No
otte
e:: If the feedback is not correct, the IFC will time
out after 90 seconds and flash the proper
fault code.
4. As the inducer ramps up to factory default speed,
the ignitor is energized. The ignitor warm up is
approximately 17 seconds.
N
No
otte
e:: If additional retries are needed, the ignitor
warm up time is successively increased to a
maximum of 30 seconds.
5. After the ignitor warm up, the 1
st
stage of the gas
valve is energized allowing gas flow.
6. The burner system will ignite, providing current to
the flame sensor. Proof of flame must be
established within 4 seconds or a retry will occur.
N
No
otte
e:: Typical flame current ranges from 7 – 10
micro-amps.
7. Once flame sense has been established, the inducer
will ramp to the “run” speed. During this transition,
the pressure switch will close and energize the 2
nd
stage of the gas valve.
8. After the“Heat On Delay” has completed, the
indoor blower is energized.
9. When the temperature raises enough to satisfy the
thermostat setting, contacts R-W will open.
10. The gas valve relay will open, closing the gas valve.
The inducer will continue to run for approximately
30 seconds to remove any combustion by-products
from inside the furnace.
11. The indoor blower continues to run to remove heat
from the heat exchangers. The “blower off” time is
field adjustable. The LED will turn to solid green
when there is no active thermostat demand.
C
Co
oo
olliin
ng
g
1. R-Y1 and R-G contacts on the thermostat close
sending 24VAC to the Y and G low voltage
terminals on the IFC. Technician should read 24VAC
between Y-C and between G-C.
The LED will flash GREEN 2 times.
2. 24VAC is sent to the OD unit via thermostat wiring.
3. After a 6 second “Blower On Delay”, the indoor
blower ramps to the cooling airflow.
N
No
otte
e:: The blower on delay can be field adjusted to
45 seconds if desired but cannot be turned
OFF.
4. When the temperature is lowered enough to satisfy
the thermostat setting, contacts R-Y1 and R-G will
open.
5. The OD unit shuts off and the indoor blower starts
after a 45 second “Cool Off Delay”.
N
No
otte
e:: The 45 second delay is not field adjustable,
and cannot be turned OFF.
