Heating Troubleshooting
Use the unit Scrolling Marquee display or a CCN device to view the heating status display and the heating diagnostic display (see Appendix A) for information on the heating operation. Check the current alarms and alarm history for any heating alarm codes and correct any causes. (See Table 12.) Verify any unique control configurations per installed site requirements or accessories. If alarms conditions are corrected and cleared, operation of the heat stages and indoor fan may be verified by using the Service Test mode. (See Table 4.)
Gas Heat (48PG Units)
See Table 17 for general gas heating service analysis. See Fig. 21 for service analysis of the IGC board logic. Check the status LED on the IGC board for any flashing alarm codes and correct any causes. (See Table 18.)
Electric Heat (50PG Units)
See Table 19 for electric heating service analysis.
Table 17 – Gas Heating Service Analysis
48/50PG and PM
PROBLEM
Heat Will Not Turn On.
Burners Will Not Ignite.
Inadequate Heating.
Poor Flame
Characteristics.
Burners Will Not Turn Off.
CAUSE
Unit is NOT configured for heat.
Active alarm.
No power to unit.
No power to IGC (Integrated Gas Control).
Heaters off due to time guard to prevent short cycling.
Thermostat or occupancy schedule set point not calling for Cooling.
No gas at main burners.
Water in gas line. Dirty air filters. Gas input too low.
Thermostat or occupancy schedule set point only calling for W1.
Unit undersized for load.
Restricted airflow.
Too much outdoor air.
Limit switch cycles main burners.
Incomplete combustion (lack of combustion air) results in: Aldehyde odors, CO, sooting flame, or floating flame.
Unit is in Minimum on‐time.
Unit running in Service Test mode.
Main gas valve stuck.
REMEDY
Check heating configurations using the ComfortLink Scrolling Marquee
Check active alarms using ComfortLink Scrolling Marquee and the IGC flash codes.
Check power supply, fuses, wiring, and circuit breakers. Check fuses and plugs.
Check using ComfortLink Scrolling Marquee and the IGC flash codes.
Check using ComfortLink Scrolling Marquee.
Check gas line for air and purge as necessary. After purging gas line of air, allow gas to dissipate for at least 5 minutes before attempting to re‐light unit.
Drain water and install drip. Replace air filters.
Check gas pressure at manifold. Refer to gas valve adjustment. Allow time for W2 to energize or adjust setpoints.
Decrease load or increase of size of unit.
Remove restriction. Check SAT compared to the SAT heating limits.
Check economizer position and configuration. Adjust minimum position using ComfortLink Scrolling Marquee.
Check rotation of blower, thermostat heat anticipator settings, and temperature rise of unit. Adjust as needed.
Check all screws around flue outlets and burner compartment. Tighten as necessary.
Cracked heat exchanger, replace.
Unit is over‐fired, reduce input. Adjust gas line or manifold pressure.
Check vent for restriction. Clean as necessary. Check orifice to burner alignment.
Check using ComfortLink Scrolling Marquee and the IGC flash codes.
Check using ComfortLink Scrolling Marquee.
Turn off gas supply and unit power. Replace gas valve.
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