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

API Reference

Health

System

Zones

DHW

TES

HCU

Heat Pumps

FCUs

Weather

Events

Metrics

Prometheus

Tokens

Config

Firmware

HCU Faults (Process & Flow)

Heat Pump Faults

Sensors

Electrical

Refrigerant

Compressor

FCU Faults

Sensor Faults

Legionella Faults

​HCU Faults (Process & Flow)

​Heat Pump Faults

​Sensors

​Electrical

​Refrigerant

​Compressor

​FCU Faults

​Sensor Faults

​Legionella Faults

HCU Faults (Process & Flow)

Heat Pump Faults

Sensors

Electrical

Refrigerant

Compressor

FCU Faults

Sensor Faults

Legionella Faults