290699-YIM-B-0607
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Unitary Products Group
cuit is indicated, then check the wiring between the
ICB and the draft motor. If the wiring is not shorted
together, then replace the draft motor. If an open cir-
cuit is indicated, then reconnect the 9 pin wiring har-
ness to the ICB and remove power to the unit for at
least 20 seconds. Restore power to the unit. If the
ICB continues to flash a code 3, then replace the ICB.
PILOT FLAME LOCKOUT
The ICB counts the number of flame losses during the
same call for heat. If more than 16 flame losses occur
within the same call for heat, then the control tempo-
rarily locks out furnace operation for 5 minutes (flash
code 5). If the call for heat remains after the 5 minutes,
then the ICB will retry the ignition sequence. The flame
losses can be due to low inlet pressure, debris around
flame sensor, plugged pilot burner, soot on the surface
of the flame sensor or misadjusted pilot pressure.
Remove the power to the unit for 20 seconds and then
restore power to the unit. Induce a call for heat and
observe the pilot flame in the flame sensor area to
determine the best course of action.
1.
If the flame is strong and stable in the flame sensor
area, then verify the position of the flame sensor
per the start up procedures. If ok, then remove the
flame sensor and check the cleanliness of the elec-
trode. If clean, then replace the flame sensor and
adjust pilot per the start up procedures. If not
clean, then clean, reinstall and adjust pilot per the
start up procedures.
2.
If the flame is weak or unstable in the flame sensor
area, then verify the gas inlet pressure. If gas inlet
pressure is above the minimum inlet pressure stated
on unit data label, then adjust the pilot pressure per
the start up procedures. If the pilot cannot be
adjusted to obtain a strong and stable flame in the
flame sensor area, then remove the burner assem-
bly and verify the pilot burner assembly is open
internally and the holes in the burner are clean.
Check the pilot orifice size to the unit data plate and
the cleanliness of the pilot orifice. Verify that the
flame sensor electrode is clean and is adjusted
properly. After cleaning or replacement of the pilot
assembly components, reinstall the burner assem-
bly and adjust pilot per the start up procedure.
PRIMARY OR AUX TEMPERATURE LIMIT
The temperature limits limit the temperature in the fur-
nace to a safe level. If a temperature higher than the
preset limit is achieved due to low or no air flow
through the furnace, then the temperature limits opens
and the ICB closes the gas valve and flashes code 6.
The primary limit is automatic reset type while the aux-
iliary limit is manual reset type. If either one opens,
then the ICB removes power to the gas valve and the
UCB energizes the indoor blower until the primary limit
automatically resets or the auxiliary limit is manually
reset. Verify adequate air flow through the furnace. If
air flow is nonexistent or weak, then troubleshoot and
repair the conditioned space air circulation system as
necessary. Reset the auxiliary limit and verify proper
operation of the furnace. If airflow is normal, then verify
the gas input rate to the furnace following the start up
procedures (auxiliary limit must be reset before the fur-
nace will operate). If after verifying the circulating air
system, the input rate to the furnace and that the air
temperature rise through the furnace is within the rise
range on the unit data plate the flash code still exists,
then set the gas valve to the off position and tempo-
rarily apply control voltage (~24 volts) to pin 9 of the 9
pin ICB connector. With power applied to the unit, if the
ICB LED continues to flash a code 6, then replace the
ICB and return unit to operation (you must remove the
temporary voltage to pin 9 before the gas valve is
turned on). If the ICB LED flashes a heartbeat, then
replace the limit that is opening, remove the temporary
voltage applied to pin 9, turn on the gas valve, restart
the furnace and verify proper operation of the furnace.
ROLLOUT SWITCH
The rollout switch is installed to protect the furnace from
damage due to excessive heat in the burner area. There
are 4 main reasons the rollout switch will open (flash code
7) due to excessive heat in the burner area. You must
remove power to the unit for 20 seconds to reset the ICB.
1.
A blocked flue outlet is the most common cause for
the rollout switch to open. Check the flue outlet for
debris and clear if necessary.
2.
Loose blower wheel on draft motor. Verify that the
blower wheel is securely fastened to the draft
motor shaft.
3.
Unit operating outside the air temperature rise
range stated on the unit data plate. Either the air
flow through the furnace is not sufficient or the gas
input rate to the furnace exceeds the recom-
mended rate. Verify both conditions are within the
published ranges.
4.
Cracked heat exchanger tube(s). If a heat
exchanger tube or tubes is cracked, then the flow
through the heat exchanger is restricted and the
flame will either roll out of the tube inlet or heat will
build to an abnormal level in the burner area. This
can usually be determined by observing burner
flame with and without indoor blower operation. If
