Commercial RTU Fault Matrix
| OEM / Platform | Fault Code | Failure State | Diagnostic Protocol |
|---|---|---|---|
| Carrier WeatherMaker | Code 13 | Limit Switch Lockout | Limit switch tripped 3 consecutive times. High probability of severely restricted return air from post-fire soot. Perform complete VAV box flow test. |
| Carrier WeatherMaker | Code 14 | Ignition Lockout | Check flame sensor for soot binding. Submerged gas valves must be Red Tagged per TSSA guidelines and replaced entirely. |
| Carrier WeatherMaker | Code 24 | Secondary Voltage Fuse | 3-amp fuse blown on control board. Look for dead-shorts in the 24V thermostat wire exposed to flood water. |
| Carrier WeatherMaker | Code 33 / 81 | High Limit Open | Verify evaporator coil for fire-retardant chemical fouling. Requires high-volume chemical neutralization and static pressure delta verification. |
| Carrier InteliSense | Amber LED | Communication Loss | An amber LED must be solid to indicate power. The green LED must illuminate solid to confirm communication between the board and the thermostat. |
| Trane Precedent | Code 2 | System Lockout | Retries exceeded. Often caused by severe storm damage to outdoor exhaust flues. Clear physical debris before resetting ignition sequence. |
| Trane Precedent | Code 3 | Combustion Fail | Draft inducer failure post-water ingestion. Requires inducer assembly replacement and heat exchanger borescope. |
| Trane Precedent | Code 4 | Thermal Limit Open | Indicates extreme overheating of the heat exchanger. Verify variable frequency drive (VFD) parameters on the supply blower. |
| Trane Precedent | COMM Err | RTRM Communication Loss | Power surge or lightning strike protocol. Measure 24VAC to ReliaTel board. If absent, replace transformer; if present, replace RTRM module. |
| Lennox Energence | Alarm 11 | Primary Limit Open | Airflow restriction. Perform hot-wire anemometer readings across return dampers. Ensure building management system (BMS) hasn't closed economizers. |
| Lennox Energence | Alarm 13 | Pressure Switch Open | Combustion air motor failure. High probability in units subjected to prolonged hail or debris storms blocking intake louvers. |
| Lennox Energence | Alarm 113 | Compressor High Pressure | Condenser fan motor failure due to debris ingestion (e.g. tornado/hurricane). Verify fan capacitor microfarads before motor replacement. |
| Lennox Energence | Alarm 413 | Rollout Switch Open | Flame rollout detected. High probability of cracked heat exchanger or blocked flue. Mandatory visual borescope before resetting switch. |
| York Sunline | 3 Flashes | Low Pressure Switch | Refrigerant loss. Recover remaining charge per EPA 608, braze leak, pressure test with nitrogen (400 PSI), vacuum to 500 microns. |
| York Sunline | 4 Flashes | High Pressure Switch | Dirty condenser coils from rooftop ash or environmental fallout. Requires aggressive alkaline foaming coil clean. |
| York Sunline | 9 Flashes | Ignition Control Failure | Internal board fault, often caused by building power surges or brownouts. Requires OEM control board replacement and grounding verification. |
| Goodman / Daikin | Error E0 | Communication Error | Loss of signal between indoor air handler and outdoor inverter. Check shielding on communication wire for rodent or water damage. |
| Goodman / Daikin | Error E3 | Low Pressure Sensor Open | Severe refrigerant leak or failing TXV (Thermostatic Expansion Valve). Conduct thermal imaging scan of coil header. |
| Goodman / Daikin | Error E4 | Temperature Sensor Fault | Thermistor shorted due to extreme thermal exposure. Verify resistance values across sensor harness against 10k thermistor curve at 25°C. |
| Goodman / Daikin | 1 Flash | Ignition Failure | Ignitor is not glowing. Verify 120VAC to silicon nitride ignitor during startup sequence. Replace ignitor if resistance is infinite. |
| Goodman / Daikin | 3 Flashes | Pressure Switch Open | Inducer motor failing to generate required negative pressure. Check internal inducer port for calcium buildup or water blockages. |
| Goodman / Daikin | 4 Flashes | Primary Limit Open | Airflow restriction. In post-fire scenarios, HEPA/MERV filters will rapidly bind with ash. Replace primary and secondary filter stages before replacing limit. |
| Rheem / Ruud | Code 13 | Flame Lost After Estab. | Intermittent gas pressure or burner grounding issue. Check manifold pressure and ensure solid ground connection post-flood structural drying. |
| Rheem / Ruud | Code 14 | Ignition Lockout | Control board has locked out after 4 failed ignition attempts. Ensure spark electrode gap is correctly set to 1/8". |
| Rheem / Ruud | Code 22 | Main Limit / Blower Fault | Ensure blower motor is operational. Variable speed ECM motors subjected to water intrusion must be replaced entirely as internal rectifiers will short. |
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