Service Manual

46
speed. Error code “E0” is flashed during the Soft Lock-
out period.
The retry count is cleared if flame is sensed for longer
than 10 seconds after exiting Trial for Ignition, or
upon exit of Soft Lockout.
Ignition Recycles:
When flame is established during Trial for Ignition, and
then lost:
• The gas valve is de-energized.
• The inducer moves to the ignition speed and holds
for the Inter-purge Period.
• The circulator if already running remains energized
at the current CFM for the circulator fan off delay
period.
• When the Inter-purge Period expires, the control pro-
ceeds to the HSI Warm-up and then a new Trial for
Ignition is started.
• A maximum of two recycles (3 flame losses) are al-
lowed on a single call for heat before the control pro-
ceeds to Soft Lockout through the Post-purge where
the inducer remains energized at the current speed.
Error code “E0” is flashed during the Soft Lockout
period.
• The recycle count is not cleared until the current de-
mand for heat is satisfied or upon exit of Soft Lock-
out.
Rollout Circuit Operation
If the manual reset rollout switch circuit opens during a
heating cycle:
• The valve is immediately de-energized.
• The inducer will run for the Post-purge period at its
current speed
• If the circulator fan is on it will run for the normal fan
off delay at the current heat speed.
• An error code is logged and displayed indicating the
rollout switch circuit has opened.
• All future thermostat heat requests are ignored..
The IFC will remain in this state until the rollout switch
closes. Once the manual rollout switch has been re-
set the IFC will clear the error code and return to
normal operation.
If the rollout switch circuit opens in any mode, other than
Heat, it will be ignored.
Limit Switch Operation
If the limit switch circuit is open during a heating cycle:
• The valve is immediately de-energized.
• The inducer will run for the Post-purge period at its
current speed.
• The circulator is immediately energized at high heat
speed. The IFC will remain in this state until the
limit switch circuit closes.
• The IFC logs and displays an error code indicating the
limit circuit is open.
• Once the limit switch circuit closes and a call for heat
is present, a new ignition sequence is started and
the circulator will remain energized for the selected
fan off delay. If the burner is lit before expiration of
the selected fan off delay, the fan off timing is
stopped and the circulator will adjust to the speed
requested by the heating sequence.
If the limit switch circuit opens in any mode, other than
Heat, it will be ignored.
Pressure Switch Configuration
• The IFC monitors the contacts of a SPST (single pole
single throw) low pressure switch with a set point that
ensures the switch will be closed at approximately
35% of the firing rate of the furnace.
• The IFC monitors the contacts of a SPST high pres-
sure switch with a set point that ensures the switch
will be closed at approximately 100% of the firing rate
of the furnace.
H Fitting
Restricting Orifice
Restricting Orifice
The H-fitting
“conditions”
the negative
pressure
signal which
is applied to
the gas valve
"H" Fitting
The low pressure switch assembly includes an H fitting as-
sembly and tubing that provides pressure signals to the
Honeywell amplified gas/air gas valve. The H fitting con-
tains an orifice which conditions the negative air pressure
controlling the gas valve. This has the effect of allowing
only smooth changes in air pressure to reach the gas valve.
Low Pressure Switch Operation
• If a call for heat exists and the low pressure switch is
closed already (before the ignition sequence has be-
gun), the IFC will wait 5 minutes. After the 5 minute
delay, and if the LPS is still closed, the IFC will log
and display an error code indicating the low pressure
switch is stuck closed. When the LPS is sensed open,
the IFC clears the error code and resumes normal op-
eration.
If the ignition sequence has begun and the low pressure
switch fails to close within 30 seconds, the IFC logs and
displays an error code indicating the low pressure switch is
stuck open. The inducer continues to run for a total of 5
OPERATION