36
18-CD19D8-18
Installer’s Guide
IFC Error Flash Codes
ABNORMAL CONDITIONS
1. EXCESSIVE COMBUSTION PRESSURE (WIND IN
EXCESS OF 40 M.P.H.) VENT OR FLUE BLOCKAGE
On a call for heat, the variable speed draft inducer must
first ramp up to speed and close the pressure switch
before the ignition sequence is allowed to begin. If the
pressure switch does not close, the motor will ramp up to
maximum speed and continue to operate there for about
1 minute.
After one minute the integrated furnace control will turn
the motor off for about 30 seconds then back on in an
attempt to reestablish proper operation. This condition
is indicative of a highly restricted or blocked inlet or
outlet vent pipe or a failed pressure switch.
If pressure against induced draft blower outlet becomes
excessive, the pressure switch will open. If the pressure
switch is open for more than 3.5 seconds, the variable
speed draft inducer will speed up and attempt to close
the pressure switch. If the pressure switch is not closed
within 12 seconds or if the maximum speed of the motor
is reached, the draft inducer sends a fault signal to the
integrated furnace control. If the unit is operating in
second stage, an inducer fault will cause the furnace
control to transition the system to first stage and it will
operate there for 10 minutes before attempting to run
again in second stage. If the unit is operating in first
stage, an inducer fault will cause the furnace control to
shut the system down and wait 30 seconds before
attempting to reestablish operation in first stage.
2. LOSS OF FLAME
If loss of flame occurs during a heating cycle, or flame is
not present at the sensor, the flame control module will
close the gas valve. The flame control module will then
recycle the ignition sequence, then if ignition is not
achieved, it will shut off the gas valve and lock out the
system.
3. POWER FAILURE
If there is a power failure during a heating cycle, the
system will restart the ignition sequence automatically
when power is restored, if the thermostat still calls for
heat.
4. GAS SUPPLY FAILURE
If loss of flame occurs during a heating cycle, the system
integrated control module will recycle the ignition sequence,
then if ignition is not achieved, the integrated control
module will shut off the gas valve and lock out the system.
5. INDUCED DRAFT BLOWER FAILURE
Please refer to the variable speed draft inducer
troubleshooting manual for diagnostic assistance.
6. CONDENSATE DRAIN BLOCKAGE
If the condensate drain is blocked, either by debris,
improper draining, or by freezing condensate, the
pressure switch will sense the accumulation of conden-
sate in the furnace drain pan. The unit will not operate
properly until the condensate drain has been cleared, and
the condensate flows freely.
7. RESET AFTER LOCKOUT
When the integrated control module has shut the system
down and gone into lockout, the system must be manu-
ally reset before the unit will restart. The system can be
reset by turning the system power off for more than
1 second, or by removing 24VAC from the control for more
than 1 second, or by removing the thermostat call for
heat for more than 1 second but less than 20 seconds.
8. RESET AFTER BURNER BOX LIMIT SHUTDOWN
If the furnace shuts down, one thing that can be checked
is the burner box temperature limit switch. It is located
on the bottom of the burner box. The vent and combus-
tion air inlet terminations should be checked for block-
age. If blockage exists, clear the problem and then the
reset button may be depressed.
If there is no block-
age of the terminations, the limit switch must be
reset by a qualified servicer.