Heating Troubleshooting - Carrier 48LC Series Controls, Start-Up, Operation And Troubleshooting

Heating Troubleshooting

Use the unit SystemVut Display or a CCN device to view the
heating status display and the heating diagnostic display (see
Appendices) for information on the heating operation. Check the
current alarms and alarm history for any heating alarm codes and
correct any causes. (See Table 13.) 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.)
PROBLEM
Heat Will Not Turn On.
Burners Will Not Ignite.
Inadequate Heating.
Poor Flame
Characteristics.
Burners Will Not Turn Off.
Table 18 – Gas Heating Service Analysis
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.
Gas Heat (48LC Units)
See Table 18 for general gas heating service analysis. See Fig. 24
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 19.)
Electric Heat (50LC Units)
See Table 20 for electric heating service analysis.
Check heating configurations using the SystemVu Display
Check active alarms using SystemVu Display and the IGC flash
codes.
Check power supply, fuses, wiring, and circuit breakers.
Check fuses and plugs.
Check using SystemVu Display and the IGC flash codes.
Check using SystemVu Display.
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 SystemVu Display.
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 SystemVu Display and the IGC flash codes.
Check using SystemVu Display.
Turn off gas supply and unit power. Replace gas valve.
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REMEDY