PROBLEM
Burners Will Not
Ignite.
Table 37 -- Heating Service Analysis
CAUSE
Misaligned spark electrodes.
No gas at main burners.
Water in gas line.
No power to furnace.
No 24 v power supply to control circuit.
Miswired or loose connections.
Burned-out heat anticipator in thermostat.
Broken thermostat wires.
Inadequate Heating. Dirty air filter.
Gas input to unit too low.
Unit undersized for application.
Restricted airflow.
Blower speed too low.
Limit switch cycles main burners.
Too much outdoor air.
Poor Flame
Characteristics.
Incomplete combustion (lack of combustion air)
results in:
Aldehyde odors, CO (carbon monoxide),
sooting flame, or floating flame.
Burners Will Not Unit is locked into Heating mode for a
Turn Off. one minute minimum.
Table 38 -- IGC Board LED Alarm Codes
LED FLASH DESCRIPTION ACTION TAKEN BY RESET METHOD PROBABLE CAUSE
CODE CONTROL
On Normal Operation -- -- --
Off Hardware Failure No gas heating. -- Loss of power to the IGC. Check 5 amp fuse on IGC,
aower to unit, 24 v circuit breaker, transformer, and wir-
ing to the IGC.
1 Flash Indoor Fan On/Off Delay 5 seconds subtracted from On Power reset. High temperature limit switch opens during heat
Modified delay, exchanger warm-up period before fan-on delay expires.
5 seconds added to Off delay High temperature limit switch opens within
(3 rain max). 10 minutes of heat call (W) Off.
See Limit Switch Fault,
2 Flashes Limit Switch Fault Gas valve and igniter Off. Limit switch closed, or heat High temperature limit switch is open, Check the opera-
Indoor fan and inducer On. call (W) Off. tion of the indoor (evaporator) fan motor, Ensure that the
supply-air temperature rise is within the range on the
unit nameplate, Check wiring and limit switch operation.
3 Flashes Flame Sense Fault Indoor fan and inducer On. Flame sense normal, The IGC sensed a flame when the gas valve should be
Power reset for LED reset, closed. Check wiring, flame sensor, and gas valve
operation.
4 Flashes Four Consecutive Limit Switch No gas heating. Heat call (W) Off. 4 consecutive limit switch faults within a single call for
Fault Power reset for LED reset, heat. See Limit Switch Fault,
5 Flashes Ignition Fault No gas heating. Heat call (W) Off. Unit unsuccessfully attempted ignition for 15 minutes,
Power reset for LED reset. Check igniter and flame sensor electrode spacing, gaps,
etc. Check flame sense and igniter wiring, Check gas
valve operation and gas supply.
6 Flashes Induced Draft Motor Fault If heat off: no gas heating, Inducer sense normal, or Inducer sense On when heat call Off, or inducer sense
If heat on: gas valve Off and heat call (W) Off. Off when heat call On. Check wiring, voltage, and eper-
inducer On. ation of IGC motor. Check speed sensor wiring to IGC.
7 Flashes Rellout Switch Lockout Gas valve and igniter Off. Power reset, Rollout switch has opened, Check gas valve operation.
Indoor fan and inducer On. Check induced-draft blower wheel is properly secured to
motor shaft.
8 Plashes Internal Control Lockout No gas heating. Power reset. IGC has sensed internal hardware or software error, If
fault is not cleared by resetting 24 v power, replace the
IGC.
9 Flashes Temporary Software Lockout No gas heating. 1 hour auto reset, or power Electrical interference is disrupting the IGC
reset, software.
REMEDY
Check flame ignition and sensor electrode positioning. Adjust as needed.
Check gas line for air purge as necessary. After purging gas line of air, allow gas to dis-
sipate for at least 5 minutes before attempting to relight unit.
Check gas valve.
Drain water and install drip leg to trap water,
Check power supply, fuses, wiring, and circuit breaker,
Check transformer, Transformers with internal overcurrent protection require a cool-
down period before resetting, Check 24-v circuit breaker; reset if necessary.
Check all wiring and wirenut connections.
Replace thermostat.
Run continuity check. Replace wires, if necessary.
Clean or replace filter as necessary.
Check gas pressure at manifold. Clock gas meter for input. If too low, increase mani-
fold pressure or replace with correct orifices.
Replace with proper unit or add additional unit,
Clean filter, replace filter, or remove any restrictions.
Use high speed tap, increase fan speed, or install optional blower, as suitable for indi-
vidual units, Adjust pulley.
Check rotation of blower, thermostat heat anticipator settings, and temperature rise of
unit. Adjust as needed.
Adjust minimum position,
Check economizer operation,
Check all screws around flue outlets and burner compartment. Tighten as necessary.
Cracked heat exchanger. Replace.
Overtired unit -- reduce input, change orifices, or adjust gas line or manifold pressure.
Check vent for restriction, Clean as necessary.
Check orifice to burner alignment.
Wait until mandatory one-minute time period has elapsed or reset power to unit,
LEGEND
IGC -- Integrated Gas Unit Control
LED -- Light-Emitting Diode
NOTES:
1. There is a 3-second pause between alarm code displays,
2. If more than one alarm code exists, all applicable alarm codes will be dis-
played in numerical sequence.
3. Alarm codes on the IGC will be lost if power to the unit is interrupted.
4"7
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