Carrier 48HC 04-28 Manual

Also see for /50HC 04-28: Controls, Start-Up, Operation and Troubleshooting

Carrier 48HC 04-28 Manual Manual pdf 43 page image

43Heating TroubleshootingUse the unit Scrolling Marquee display or a CCN device to viewthe heating status display and the heating diagnostic display (seeAppendix A) for information on the heating operation. Check thecurrent alarms and alarm history for any heating alarm codes andcorrect any causes. (See Table 9.) Verify any unique controlconfigurations per installed site requirements or accessories. Ifalarms conditions are corrected and cleared, operation of the heatstages and indoor fan may be verified by using the Service Testmode. (See Table 4.)Gas Heat (48HC Units)See Table 14 for general gas heating service analysis. See Fig. 15for service analysis of the IGC board logic. Check the status LEDon the IGC board for any flashing alarm codes and correct anycauses. (See Table 15.)Electric Heat (50HC Units)See Table 16 for electric heating service analysis.Table 14 – Gas Heating Service AnalysisPROBLEM CAUSE REMEDYHeat Will Not Turn On. Unit is NOT configured for heat. Check heating configurations using the ComfortLink ScrollingMarqueeBurners Will Not Ignite.Active alarm. Check active alarms using ComfortLink Scrolling Marquee andthe IGC flash codes.No power to unit. Check power supply, fuses, wiring, and circuit breakers.No power to IGC (Integrated Gas Control). Check fuses and plugs.Heaters off due to time guard to prevent shortcycling.Check using ComfortLink Scrolling Marquee and the IGC flashcodes.Thermostat or occupancy schedule set point notcalling for Cooling.Check using ComfortLink Scrolling Marquee.No gas at main burners. Check gas line for air and purge as necessary. After purging gasline of air, allow gas to dissipate for at least 5 minutes beforeattempting to re-light unit.Water in gas line. Drain water and install drip.Inadequate Heating. Dirty air filters. Replace air filters.Gas input too low. Check gas pressure at manifold. Refer to gas valve adjustment.Thermostat or occupancy schedule set point onlycalling for W1. Allow time for W2 to energize or adjust setpoints.Unit undersized for load. Decrease load or increase of size of unit.Restricted airflow. Remove restriction. Check SAT compared to the SAT heatinglimits.Too much outdoor air. Check economizer position and configuration. Adjust minimumposition using ComfortLink Scrolling Marquee.Limit switch cycles main burners. Check rotation of blower, thermostat heat anticipator settings,and temperature rise of unit. Adjust as needed.Poor FlameCharacteristics. Incomplete combustion (lack of combustion air)results in: Aldehyde odors, CO, sooting flame, orfloating flame.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 manifoldpressure.Check vent for restriction. Clean as necessary.Check orifice to burner alignment.Burners Will Not Turn Off. Unit is in Minimum on-time. Check using ComfortLink Scrolling Marquee and the IGC flashcodes.Unit running in Service Test mode. Check using ComfortLink Scrolling Marquee.Main gas valve stuck. Turn off gas supply and unit power. Replace gas valve.ComfortLINK v1.X