29
Table 13 –
Troubleshooting Guide–Heating
SYMPTOM
CAUSE
REMEDY
Burners will not ignite
Water in gas line
Drain. Install drip leg.
No power to furnace
Check power supply fuses, wiring or circuit breaker.
No 20--v power supply to control circuit
Check transformer.
NOTE: Some transformers have internal over--current
protection that requires a cool--down period to reset.
Mis--wired or loose connections
Check all wiring and wire nut connections
Burned--out heat anticipator in thermostat
Replace thermostat
Broken thermostat wire
Replace thermostat
Burned--out heat anticipator in thermostat
Run continuity check. Replace wire if necessary.
Misaligned spark electrodes
Check flame ignition and sense electrode positioning. Ad-
just as necessary
No gas at main burners
1. Check gas line for air. Purge as necessary. NOTE: After
purging gas line of air, wait at least 5 minutes for any gas
to dissipate before attempting to light unit.
2. Check gas valve.
Inadequate heating
Dirty air filter
Clean or replace filter as necessary
Gas input to furnace too low
Check gas pressure at manifold match with that on unit
nameplate
Unit undersized for application
Replace with proper unit or add additional unit
Restricted airflow
Clean or replace filter. Remove any restriction.
Blower speed too low
Use faster speed tap if available, or install alternate motor.
Limit switch cycles main burners
Check rotation of blower, temperature rise of unit. Adjust
as necessary.
Poor flame characteristics
Incomplete combustion results in: Aldehyde odors, carbon mon-
oxide, sooting flame, floating flame
1. Tighten all screws around burner compartment
2. Cracked heat exchanger. Replace.
3. Unit over--fired. Reduce input (change orifices or adjust
gas line or manifold pressure).
4. Check burner alignment.
Table 14 –
Troubleshooting Guide–LED Error Codes
SYMPTOM
CAUSE
REMEDY
Hardware failure
(LED OFF)
Loss of power to control module (IGC)*.
Check 5--amp fuse son IGC*, power to unit, 24--v circuit breaker,
and transformer. Units without a 24--v circuit breaker have an
internal overload in the 24--v transformer. If the overload trips,
allow 10 minutes for automatic reset.
Fan ON/OFF delay modified
(LED/FLASH)
High limit switch opens during heat exchanger warm--up
period before fan--on delay expires. Limit switch opens
within three minutes after blower--off delay timing in heat-
ing mode.
Ensure unit is fired on rate; ensure temperature rise is correct.
Ensure unit’s external static pressure is within application guide-
lines.
Limit switch faults
(LED 2 flashes)
High temperature limit switch is open.
Check the operation of the indoor (evaporator) fan motor. Ensure
that the supply--air temperature rise is in accordance with the
range on the unit nameplate.
Flame sense fault
(LED 3 flashes)
The IGC* sensed flame that should not be present.
Reset unit. If problem persists, replace control board.
4 consecutive limit switch
faults
(LED 4 flashes)
Inadequate airflow to unit.
Check the operation of the indoor (evaporator) fan motor and that
supply--air temperature rise agrees with range on unit nameplate
information.
Ignition lockout
(LED 5 flashes)
Unit unsuccessfully attempted ignition for 15 minutes.
Check ignitor and flame sensor electrode spacing, gaps, etc.
Ensure that fame sense and ignition wires are properly termi-
nated. Verify that unit is obtaining proper amount of gas.
Induced--draft motor fault
(LED 6 flashes)
IGC does not sense that induced--draft motor is operat-
ing.*
Check for proper voltage. If motor is operating, check the speed
sensor plug/IGC Terminal J2 connection. Proper connection:
PIN 1 -- White
PIN 2 -- Red
PIN 3 -- Black
Rollout switch fault
(LED 7 flashes)
Rollout switch has opened.
Rollout switch will automatically reset, but IGC* will continue to
lockout unit. Check gas valve operation. Ensure that induced--
draft blower wheel is properly secured to motor shaft. Reset unit
at unit disconnect.
Roolout control fault
(LED 8 flashes)
Microprocessor has sensed an error in the software or
hardware.
If error code is not cleared by resetting unit power, replace the
IGC*.
Safety Critical fault
(LED 9 flashes)
If Safety Critical Software Redundant Variables Mismatch
occurs then IGC will lockout (This fault will clear after 1
hr.)
Verify that flame sensor wire and spark ignitor wires are not
touching or close together. Ensure unit has a good ground on the
IGC board.
*
WARNING
:
If the IGC must be replaced, be sure to ground yourself to dissipate any electrical charge that my be present before handling new control board. The IGC is
sensitive to static electricity and my be damaged if the necessary precautions are not taken.
IMPORTANT
: Refer to Table 13--Troubleshooting Guide--Heating for additional troubleshooting analysis.
LEGEND
IGC—Integrated Gas Unit Controller
LED—Light--Emitting Diode
574B
