Samsung EHS Fault Codes

Complete reference of Samsung EHS heat pump error codes with causes and solutions. Search by code number or keyword to quickly diagnose issues.

Most Common EHS Errors

E911E912

Flow-Related Errors

The most reported errors on forums. E911 indicates low or no flow when the system expects it; E912 indicates flow when there should be none.

Common causes

Flow switch failures or sensitivity issues
Air trapped in the system
Dirty or clogged filters
Zone valves not opening fast enough
Insufficient flow rate (need >20 L/min)
Stuck relay, faulty PCB, or thermosiphon effect (E912)

Solutions

Install an inline flow meter to verify actual flow rate
Add an automatic bypass valve
Ensure flow rate exceeds 20 L/min
Bleed all air from the system thoroughly
Clean or replace filters and strainers
Check that zone valves open before the compressor starts
For E912: add non-return valve, inspect relay/PCB

E919

Legionella Cycle Failure

The built-in legionella disinfection cycle (runs at 3am Tuesday by default) failed to reach 60°C within 8 hours.

Common causes

Incorrectly positioned tank sensor (not deep enough into pocket)
Immersion heater thermostat set below 60°C
Immersion heater element failed
Sensor positioned below the immersion element

Solutions

Check sensor position — must be 100mm into tank pocket, above the immersion element
Set immersion thermostat above 60°C
Test immersion heater element for continuity
Consider disabling Samsung's built-in cycle (FSV 3041 = 0) and using a weekly timer instead

E101

Indoor/Outdoor Communication Error

The indoor unit cannot receive data from the outdoor unit. Usually wiring-related, this is one of the first errors to appear after installation.

Common causes

Disconnected or damaged communication cables
Wrong cable type (must use 16/2 stranded shielded cable)
Cable grounded at both ends (should only be grounded at outdoor unit)
Blown PCB from electrical fault
Electromagnetic interference from nearby power cables

Solutions

Inspect all cables between indoor and outdoor units
Verify correct cable type: 16/2 stranded shielded
Ensure cable shield is grounded at the outdoor unit only
Check for visible damage or corrosion on connectors
Route communication cables away from power cables
Replace PCB if damaged

Full Fault Code Reference

Communication

Code	Description	Causes	Solutions
E101	Indoor can't receive data from outdoor Causes:Disconnected/damaged cables; Blown PCB Solutions:Check cables; Inspect for damage; Replace PCB	Disconnected/damaged cables Blown PCB	Check cables Inspect for damage Replace PCB
E102	Outdoor unit cannot communicate Causes:Similar to E101 — cable or PCB fault Solutions:Check wiring between units	Similar to E101 — cable or PCB fault	Check wiring between units
E108	Repeated communication address issue Causes:Duplicate indoor unit addresses Solutions:Reconfigure unit addresses	Duplicate indoor unit addresses	Reconfigure unit addresses
E185	Cross-wiring: comm/power cable swapped Causes:Installation error Solutions:Correct cable wiring	Installation error	Correct cable wiring
E186	SPi connection error Causes:SPi module fault Solutions:Check SPi connections	SPi module fault	Check SPi connections
E201	Indoor unit address / comm failure Causes:Address DIP switch misconfiguration Solutions:Verify addresses; Check wiring	Address DIP switch misconfiguration	Verify addresses Check wiring
E202	Indoor/outdoor comm failure Causes:Cable fault; Interference Solutions:Check cables	Cable fault Interference	Check cables
E203	Main/sub outdoor PCB comm error Causes:PCB fault Solutions:Check outdoor PCB connections	PCB fault	Check outdoor PCB connections
E205	All PBA within outdoor unit comm error Causes:Multiple board failures Solutions:Professional service required	Multiple board failures	Professional service required
E210	Outdoor unit/MCU comm error Causes:Wiring or MCU fault Solutions:Check MCU wiring	Wiring or MCU fault	Check MCU wiring
E601	Remote controller/indoor unit comm error Causes:Loose thermostat wiring Solutions:Check thermostat wiring; Reset by powering off for 5 minutes	Loose thermostat wiring	Check thermostat wiring Reset by powering off for 5 minutes
E602	Master/slave remote controller comm error Causes:Inter-controller wiring fault Solutions:Check interconnect wiring	Inter-controller wiring fault	Check interconnect wiring
E603	7-day scheduler/remote controller comm error Causes:Scheduler connection fault Solutions:Check scheduler wiring	Scheduler connection fault	Check scheduler wiring
E604	Remote/DVM Hydro tracking error Causes:Configuration or wiring fault Solutions:Reconfigure tracking	Configuration or wiring fault	Reconfigure tracking

Indoor Sensors

Code	Description	Causes	Solutions
E121	Room temperature sensor (open/short) Causes:Sensor failure Solutions:Replace sensor	Sensor failure	Replace sensor
E122	Evaporator inlet pipe temp sensor (open/short) Causes:Sensor failure Solutions:Replace sensor	Sensor failure	Replace sensor
E123	Evaporator outlet sensor (open/short) Causes:Sensor failure Solutions:Replace sensor	Sensor failure	Replace sensor
E128	Evaporator inlet sensor detached Causes:Sensor not secured Solutions:Reattach sensor	Sensor not secured	Reattach sensor
E129	Evaporator outlet sensor detached Causes:Sensor not secured Solutions:Reattach sensor	Sensor not secured	Reattach sensor
E130	Both evaporator sensors detached Causes:Both sensors loose Solutions:Reattach both sensors	Both sensors loose	Reattach both sensors
E131	Auxiliary electric heater sensor 1 error Causes:Sensor failure Solutions:Replace sensor	Sensor failure	Replace sensor
E132	Auxiliary electric heater sensor 2 error Causes:Sensor failure Solutions:Replace sensor	Sensor failure	Replace sensor
E133	Auxiliary electric heater sensor 3 error Causes:Sensor failure Solutions:Replace sensor	Sensor failure	Replace sensor
E134	Shutter sensor error Causes:Sensor failure Solutions:Replace sensor	Sensor failure	Replace sensor
E135	Fan sensor / RPM feedback error Causes:Fan sensor failure Solutions:Check fan sensor	Fan sensor failure	Check fan sensor
E140	MCU temperature sensor (open/short) Causes:MCU sensor failure Solutions:Replace sensor	MCU sensor failure	Replace sensor

Indoor Operational

Code	Description	Causes	Solutions
E151	EEV failure to open Causes:Valve stuck; Electrical fault Solutions:Check EEV wiring; Replace valve	Valve stuck Electrical fault	Check EEV wiring Replace valve
E152	EEV failure to close Causes:Valve stuck Solutions:Check EEV; Replace valve	Valve stuck	Check EEV Replace valve
E153	Float switch detection Causes:Condensate overflow Solutions:Check drain; Clean float switch	Condensate overflow	Check drain Clean float switch
E154	Indoor fan motor not rotating Causes:Failed motor; Obstruction Solutions:Check fan blade; Replace motor	Failed motor Obstruction	Check fan blade Replace motor
E161	Mixed heating/cooling operation Causes:Control logic fault Solutions:Reset unit; Check configuration	Control logic fault	Reset unit Check configuration
E162	EEPROM error Causes:Corrupted memory Solutions:Replace indoor PCB	Corrupted memory	Replace indoor PCB
E163	Option code setting error Causes:Incorrect DIP switch settings Solutions:Correct DIP switch settings	Incorrect DIP switch settings	Correct DIP switch settings
E165	Electric heater discharge temp protection Causes:Overheating Solutions:Check heater and airflow	Overheating	Check heater and airflow
E166	Missing fan during heater operation Causes:Fan not running during heater use Solutions:Check fan operation	Fan not running during heater use	Check fan operation
E198	Indoor thermal fuse opened Causes:Overheating protection triggered Solutions:Check cause of overheating; Replace fuse	Overheating protection triggered	Check cause of overheating Replace fuse

Outdoor Sensors

Code	Description	Causes	Solutions
E221	Outside temperature sensor (open/short) Causes:Sensor failure Solutions:Replace sensor	Sensor failure	Replace sensor
E226	Outside temperature sensor disconnected Causes:Sensor detached Solutions:Reattach or replace sensor	Sensor detached	Reattach or replace sensor
E231	Condenser outlet main temp sensor (open/short) Causes:Sensor failure Solutions:Replace sensor	Sensor failure	Replace sensor
E236	Condenser outlet 1 sensor (open/short) Causes:Sensor failure Solutions:Replace sensor	Sensor failure	Replace sensor
E251	Compressor discharge temp sensor (open/short) Causes:Sensor failure Solutions:Replace sensor	Sensor failure	Replace sensor
E271	Sump temperature sensor (open/short) Causes:Sensor failure Solutions:Replace sensor	Sensor failure	Replace sensor
E291	High pressure sensor (open/short) / refrigerant leak Causes:Sensor fault; Refrigerant leak Solutions:Check sensor; Check for leaks	Sensor fault Refrigerant leak	Check sensor Check for leaks
E296	Low pressure sensor (open/short) / refrigerant leak Causes:Sensor fault; Refrigerant leak Solutions:Check sensor; Check for leaks	Sensor fault Refrigerant leak	Check sensor Check for leaks
E301	High pressure sensor disconnected Causes:Sensor detached Solutions:Reattach sensor	Sensor detached	Reattach sensor
E306	Low pressure sensor disconnected Causes:Sensor detached Solutions:Reattach sensor	Sensor detached	Reattach sensor
E308	Suction temperature sensor (open/short) Causes:Sensor failure Solutions:Replace sensor	Sensor failure	Replace sensor
E311	Liquid pipe sensor (open/short) Causes:Sensor failure Solutions:Replace sensor	Sensor failure	Replace sensor
E474	Inverter heatsink temp sensor error Causes:Sensor failure Solutions:Replace sensor	Sensor failure	Replace sensor

Compressor/Inverter

Code	Description	Causes	Solutions
E461	Inverter compressor startup failure Causes:Mechanical or electrical fault Solutions:Professional service required	Mechanical or electrical fault	Professional service required
E462	Total current error / compressor stop Causes:Overcurrent Solutions:Check power supply	Overcurrent	Check power supply
E464	IPM over-current error Causes:Short circuit; Compressor failure Solutions:Professional service required	Short circuit Compressor failure	Professional service required
E465	Compressor V-limit/I-limit error Causes:Voltage or current limits exceeded Solutions:Check power supply	Voltage or current limits exceeded	Check power supply
E466	DC-Link over/low voltage Causes:Power fluctuation Solutions:Check mains supply	Power fluctuation	Check mains supply
E467	Compressor wire missing/unconnected Causes:Loose wiring Solutions:Check compressor cables	Loose wiring	Check compressor cables
E468	Inverter output current sensor error Causes:Current sensor failure Solutions:Replace PBA	Current sensor failure	Replace PBA
E469	Inverter DC voltage sensor error Causes:Voltage sensor failure Solutions:Replace PBA	Voltage sensor failure	Replace PBA
E470	EEPROM data error (no data) Causes:Corrupted outdoor PCB Solutions:Replace outdoor PCB	Corrupted outdoor PCB	Replace outdoor PCB
E483	Over-voltage protection Causes:Voltage spike Solutions:Check power supply	Voltage spike	Check power supply
E500	Heatsink over-temperature Causes:Blocked airflow around heatsink Solutions:Clean heatsink; Check ventilation	Blocked airflow around heatsink	Clean heatsink Check ventilation
E504	Compressor self-diagnosis error Causes:Compressor fault Solutions:Professional service required	Compressor fault	Professional service required

Outdoor Fan

Code	Description	Causes	Solutions
E446	Fan 1 operation failure Causes:Motor failure Solutions:Replace fan motor	Motor failure	Replace fan motor
E447	Fan 1 wire not connected Causes:Loose wiring Solutions:Reconnect fan wiring	Loose wiring	Reconnect fan wiring
E448	Fan 1 lock error Causes:Obstruction; Motor seizure Solutions:Clear obstruction; Replace motor	Obstruction Motor seizure	Clear obstruction Replace motor
E452	ZPC / instant power failure Causes:Power interruption Solutions:Check power stability	Power interruption	Check power stability
E453	Fan 1 overheated Causes:High load; Bearing failure Solutions:Allow cooling; Replace motor	High load Bearing failure	Allow cooling Replace motor
E458	Outdoor fan error (general) Causes:Motor failure Solutions:Replace fan motor	Motor failure	Replace fan motor
E915	DC fan non-operating Causes:DC fan failure Solutions:Replace DC fan	DC fan failure	Replace DC fan

Refrigerant/Pressure

Code	Description	Causes	Solutions
E401	Freezing detection 1 Causes:Low refrigerant; Poor airflow; Blocked coil Solutions:Check refrigerant charge; Clean coil	Low refrigerant Poor airflow Blocked coil	Check refrigerant charge Clean coil
E402	Freezing detection 2 Causes:Low refrigerant; Poor airflow; Blocked coil Solutions:Check refrigerant charge; Clean coil	Low refrigerant Poor airflow Blocked coil	Check refrigerant charge Clean coil
E403	Freezing detection 3 Causes:Low refrigerant; Poor airflow; Blocked coil Solutions:Check refrigerant charge; Clean coil	Low refrigerant Poor airflow Blocked coil	Check refrigerant charge Clean coil
E407	High pressure protection 1 Causes:Blocked condenser; Overcharge; Fan failure Solutions:Check airflow; Check refrigerant charge	Blocked condenser Overcharge Fan failure	Check airflow Check refrigerant charge
E408	High pressure protection 2 Causes:Blocked condenser; Overcharge; Fan failure Solutions:Check airflow; Check refrigerant charge	Blocked condenser Overcharge Fan failure	Check airflow Check refrigerant charge
E409	High pressure protection 3 Causes:Blocked condenser; Overcharge; Fan failure Solutions:Check airflow; Check refrigerant charge	Blocked condenser Overcharge Fan failure	Check airflow Check refrigerant charge
E410	Low pressure protection 1 Causes:Refrigerant leak; Blocked filter drier Solutions:Check for leaks; Inspect filter drier	Refrigerant leak Blocked filter drier	Check for leaks Inspect filter drier
E411	Low pressure protection 2 Causes:Refrigerant leak; Blocked filter drier Solutions:Check for leaks; Inspect filter drier	Refrigerant leak Blocked filter drier	Check for leaks Inspect filter drier
E412	Low pressure protection 3 Causes:Refrigerant leak; Blocked filter drier Solutions:Check for leaks; Inspect filter drier	Refrigerant leak Blocked filter drier	Check for leaks Inspect filter drier
E413	Sump down protection 1 Causes:Liquid refrigerant in compressor sump Solutions:Check EEV; Check superheat	Liquid refrigerant in compressor sump	Check EEV Check superheat
E414	Sump down protection 2 Causes:Liquid refrigerant in compressor sump Solutions:Check EEV; Check superheat	Liquid refrigerant in compressor sump	Check EEV Check superheat
E415	Sump down protection 3 Causes:Liquid refrigerant in compressor sump Solutions:Check EEV; Check superheat	Liquid refrigerant in compressor sump	Check EEV Check superheat
E416	Discharge temp protection 1 Causes:Low refrigerant; High compression ratio Solutions:Check refrigerant charge	Low refrigerant High compression ratio	Check refrigerant charge
E417	Discharge temp protection 2 Causes:Low refrigerant; High compression ratio Solutions:Check refrigerant charge	Low refrigerant High compression ratio	Check refrigerant charge
E418	Discharge temp protection 3 Causes:Low refrigerant; High compression ratio Solutions:Check refrigerant charge	Low refrigerant High compression ratio	Check refrigerant charge
E419	EEV self-diagnosis error 1 Causes:EEV mechanical or electrical failure Solutions:Check EEV; Replace EEV	EEV mechanical or electrical failure	Check EEV Replace EEV
E420	EEV self-diagnosis error 2 Causes:EEV mechanical or electrical failure Solutions:Check EEV; Replace EEV	EEV mechanical or electrical failure	Check EEV Replace EEV
E421	EEV self-diagnosis error 3 Causes:EEV mechanical or electrical failure Solutions:Check EEV; Replace EEV	EEV mechanical or electrical failure	Check EEV Replace EEV
E422	EEV self-diagnosis error 4 Causes:EEV mechanical or electrical failure Solutions:Check EEV; Replace EEV	EEV mechanical or electrical failure	Check EEV Replace EEV
E423	EEV self-diagnosis error 5 Causes:EEV mechanical or electrical failure Solutions:Check EEV; Replace EEV	EEV mechanical or electrical failure	Check EEV Replace EEV
E424	EEV self-diagnosis error 6 Causes:EEV mechanical or electrical failure Solutions:Check EEV; Replace EEV	EEV mechanical or electrical failure	Check EEV Replace EEV
E425	Reverse phase detection 1 Causes:3-phase wiring error Solutions:Swap two phase wires	3-phase wiring error	Swap two phase wires
E426	Reverse phase detection 2 Causes:3-phase wiring error Solutions:Swap two phase wires	3-phase wiring error	Swap two phase wires
E427	Reverse phase detection 3 Causes:3-phase wiring error Solutions:Swap two phase wires	3-phase wiring error	Swap two phase wires
E428	Compression ratio error 1 Causes:Abnormal pressure differential Solutions:Check circuit; Check valves	Abnormal pressure differential	Check circuit Check valves
E429	Compression ratio error 2 Causes:Abnormal pressure differential Solutions:Check circuit; Check valves	Abnormal pressure differential	Check circuit Check valves
E430	Compression ratio error 3 Causes:Abnormal pressure differential Solutions:Check circuit; Check valves	Abnormal pressure differential	Check circuit Check valves
E439	Refrigerant leakage detected Causes:Refrigerant leak Solutions:Leak test; Repair leak; Recharge system	Refrigerant leak	Leak test Repair leak Recharge system
E442	Charging error in heating mode Causes:Incorrect refrigerant charge Solutions:Correct refrigerant charge	Incorrect refrigerant charge	Correct refrigerant charge
E503	Service valve closed Causes:Valve left shut after maintenance Solutions:Open service valve	Valve left shut after maintenance	Open service valve
E554	Full refrigerant leak detected Causes:Major outdoor unit leak Solutions:Emergency — professional repair required immediately	Major outdoor unit leak	Emergency — professional repair required immediately

Water/Hydro

Code	Description	Causes	Solutions
E901	Water inlet pipe sensor (short/open) Causes:Sensor failure Solutions:Replace sensor	Sensor failure	Replace sensor
E902	Water outlet pipe sensor (short/open) Causes:Sensor failure Solutions:Replace sensor	Sensor failure	Replace sensor
E904	Water tank sensor (short/open) Causes:Sensor failure Solutions:Replace sensor	Sensor failure	Replace sensor
E907	Pipe rupture protection Causes:Abnormal pressure or flow detected Solutions:Check piping for damage	Abnormal pressure or flow detected	Check piping for damage
E908	Freeze prevention (recoverable) Causes:Freezing risk detected Solutions:Check antifreeze concentration; Check insulation	Freezing risk detected	Check antifreeze concentration Check insulation
E909	Freeze prevention (non-recoverable) Causes:Critical freeze event Solutions:Professional service required	Critical freeze event	Professional service required
E910	Water outlet sensor detached Causes:Sensor not in pocket Solutions:Reinsert sensor into pocket	Sensor not in pocket	Reinsert sensor into pocket
E911	Flow switch ON / pump OFF / low flow Causes:Flow switch malfunction; Low flow rate; Zone valve not opening; Clogged filter; Air in system Solutions:Replace flow switch; Clean filter; Bleed air from system; Check valves are opening; Add bypass valve; Check pump speed	Flow switch malfunction Low flow rate Zone valve not opening Clogged filter Air in system	Replace flow switch Clean filter Bleed air from system Check valves are opening Add bypass valve Check pump speed
E912	Flow detected with no demand Causes:Stuck relay or valve; Faulty PCB; Thermosiphon effect Solutions:Check valves; Inspect relay and PCB; Add non-return valve	Stuck relay or valve Faulty PCB Thermosiphon effect	Check valves Inspect relay and PCB Add non-return valve
E913	Six flow switch errors (lockout) Causes:Repeated E911/E912 errors Solutions:Resolve underlying flow issue; Reset unit	Repeated E911/E912 errors	Resolve underlying flow issue Reset unit
E914	Incorrect thermostat connection Causes:Wired incorrectly Solutions:Rewire per installation manual	Wired incorrectly	Rewire per installation manual
E917	Water tank sensor config error Causes:Misconfigured or absent sensor Solutions:Configure sensor correctly	Misconfigured or absent sensor	Configure sensor correctly
E919	Legionella disinfection incomplete Causes:Cylinder didn't reach 60°C in 8 hours; Runs at 3am Tuesday by default Solutions:Check immersion heater is working; Verify sensor position (100mm into tank, above immersion element); Set thermostat above 60°C; Disable if mains-fed unvented tank	Cylinder didn't reach 60°C in 8 hours Runs at 3am Tuesday by default	Check immersion heater is working Verify sensor position (100mm into tank, above immersion element) Set thermostat above 60°C Disable if mains-fed unvented tank

Display/Informational

Code	Description	Causes	Solutions
Ch	Compressor starting delay / crankcase heater Causes:Normal startup sequence Solutions:No action needed — normal operation	Normal startup sequence	No action needed — normal operation
CF	Filter cleaning reminder Causes:Scheduled maintenance reminder Solutions:Clean the filter	Scheduled maintenance reminder	Clean the filter
CI	Auto clean function Causes:Normal auto-clean cycle Solutions:No action needed — normal operation	Normal auto-clean cycle	No action needed — normal operation
dF	Defrost in progress Causes:Ice build-up on outdoor coil Solutions:No action needed — normal defrost cycle	Ice build-up on outdoor coil	No action needed — normal defrost cycle
E551	Defrosting operation Causes:Active defrost cycle Solutions:No action needed — normal operation	Active defrost cycle	No action needed — normal operation
E553	Equability operation Causes:System balancing in progress Solutions:No action needed — system balancing	System balancing in progress	No action needed — system balancing

Sources

Samsung EHS Installer Reference Manual (Mono Tank Integrated Type)
Samsung Gen 6 Fault Code List — Energy Lab UK
BuildHub.org.uk forum — Samsung EHS fault code discussions
OpenEnergyMonitor community — Samsung heat pump troubleshooting
Samsung Climate Solutions UK — Official support documentation