> ## Documentation Index
> Fetch the complete documentation index at: https://docs.ariscomfort.com/llms.txt
> Use this file to discover all available pages before exploring further.

# Fault Codes

> Reference for Aris system fault codes

Fault codes are reported in `activeFaults` arrays on device objects (HCU, Heat Pump, FCU, Sensor). Each code is a 4-character alphanumeric identifier indicating a specific fault condition.

## HCU Faults (Process & Flow)

Codes relating to hydraulic integrity, flow delivery, and system integration.

| Code   | Name                          | Description                                            |
| ------ | ----------------------------- | ------------------------------------------------------ |
| `E001` | Water Inlet Sensor Failure    | Inlet temperature sensor open or shorted               |
| `E002` | Water Outlet Sensor Failure   | Outlet temperature sensor open or shorted              |
| `E003` | Flow Switch Failure           | Flow switch malfunctioning or disconnected             |
| `E004` | Flow Protection               | Insufficient water flow during operation               |
| `E100` | Outdoor Communication Failure | Cannot communicate with outdoor heat pump              |
| `E101` | Indoor Communication Failure  | Internal communication failure with hydronic board     |
| `E201` | Defrost Failure               | Three unsuccessful defrost attempts; operation stopped |
| `E202` | Outlet Temp High (Heat)       | Water temp exceeded safety limits in heating mode      |
| `E203` | Outlet Temp Low (Cool)        | Water temp below safety limits in cooling mode         |
| `E204` | Outlet Temp Low (Heat/DHW)    | Cannot reach target temp; possible capacity issue      |
| `E205` | Anti-Freeze Protection        | Emergency circulation to prevent pipe freezing         |

## Heat Pump Faults

Codes specific to heat pump hardware, populated when `source_type = heat_pump`.

### Sensors

| Code   | Name                        | Description                                 |
| ------ | --------------------------- | ------------------------------------------- |
| `E010` | Ambient Temp Sensor Fault   | Outdoor air temperature sensor failure      |
| `E011` | Coil Temp Sensor Fault      | Refrigerant coil temperature sensor failure |
| `E012` | Discharge Temp Sensor Fault | Compressor discharge temp sensor failure    |
| `E013` | Suction Temp Sensor Fault   | Compressor suction temp sensor failure      |
| `E014` | High Pressure Sensor Fault  | Refrigerant high-pressure sensor failure    |
| `E015` | Low Pressure Sensor Fault   | Refrigerant low-pressure sensor failure     |
| `E102` | Driver Communication Fault  | Lost communication with compressor inverter |
| `E103` | EEPROM Failure              | Critical memory error on controller board   |

### Electrical

| Code   | Name                   | Description                            |
| ------ | ---------------------- | -------------------------------------- |
| `P001` | AC Input Over-Voltage  | Supply voltage exceeded upper limit    |
| `P002` | AC Input Under-Voltage | Supply voltage below lower limit       |
| `P003` | AC Input Over-Current  | Current draw exceeded system rating    |
| `P004` | Input Phase Error      | Missing phase or incorrect sequence    |
| `P005` | DC Bus Over-Voltage    | Internal DC bus voltage too high       |
| `P006` | DC Bus Under-Voltage   | Internal DC bus voltage too low        |
| `P007` | PFC Hardware Fault     | Power Factor Correction module failure |

### Refrigerant

| Code   | Name                     | Description                                |
| ------ | ------------------------ | ------------------------------------------ |
| `P101` | High Pressure Protection | High-pressure switch tripped               |
| `P102` | Low Pressure Protection  | Low-pressure switch tripped; possible leak |
| `P103` | Discharge Temp High      | Discharge gas temp exceeded limit          |
| `P104` | Oil Return Protection    | Oil return cycle triggered                 |
| `P105` | 4-Way Valve Failure      | Reversing valve stuck or failed            |

### Compressor

| Code   | Name                    | Description                                |
| ------ | ----------------------- | ------------------------------------------ |
| `P201` | IPM Module Protection   | Inverter module detected a fault           |
| `P202` | IPM Over-Heat           | Inverter module temperature too high       |
| `P203` | Compressor Phase Error  | Open phase or winding imbalance            |
| `P204` | Compressor Over-Current | Compressor current exceeded limits         |
| `P205` | Compressor Stall        | Compressor failed to start or stalled      |
| `P206` | Fan Motor Failure       | DC fan motor failed or not reporting speed |
| `P207` | Driver Failure          | Compressor driver board failure            |

## FCU Faults

Codes for fan coil unit hardware and process issues.

| Code   | Name                     | Description                                 |
| ------ | ------------------------ | ------------------------------------------- |
| `F010` | Airflow Fault            | Fan failed to start or insufficient airflow |
| `F011` | Condensate / Drain Fault | Condensate pan full or drain blocked        |
| `F012` | Coil Temp Sensor Fault   | Coil temperature sensor open/short          |
| `F013` | Comm Fault (Local)       | Internal FCU communication failure          |
| `F014` | FCU Communication Lost   | Brain lost contact with FCU (auto-clears)   |

## Sensor Faults

Codes for standalone sensors and system-level threshold violations.

| Code   | Name                          | Description                                |
| ------ | ----------------------------- | ------------------------------------------ |
| `S001` | Sensor Communication Lost     | No data from sensor within expected window |
| `S002` | Sensor Reading Invalid        | Value outside physically possible range    |
| `S100` | System Pressure Critical Low  | Below 0.75 bar; likely major leak          |
| `S101` | System Pressure Warning Low   | 0.75-1.0 bar; possible slow leak           |
| `S102` | System Pressure Warning High  | 1.4-1.7 bar; check expansion vessel        |
| `S103` | System Pressure Critical High | Above 1.7 bar; PRV may trigger             |
| `S200` | Disk Space Critical           | Storage below 5% free                      |
| `S201` | Disk Space Warning            | Storage below 10% free                     |

## Legionella Faults

Codes for DHW sanitization cycles.

| Code   | Name                 | Description                               |
| ------ | -------------------- | ----------------------------------------- |
| `L001` | Sanitization Timeout | DHW tank did not reach 60C within 3 hours |