Protherm
Protherm Smart Thermostats Error Codes
Complete list of fault codes and troubleshooting guides. Use the search below to find your specific error.
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E1
E1 error and thermostat shows very low or negative room temperature values.
Room Sensor Calibration Error
E2
E2 error and thermostat cannot control cooling mode on systems with reversible heat pumps.
Cooling Mode Configuration / Output Error
E3
E3 error and thermostat indicates low supply voltage or frequently reboots when boiler starts.
Low Voltage Supply / Power Input Error
E4
E4 error and thermostat indicates that maximum floor temperature limit has been exceeded.
Floor Overtemperature Protection Triggered
E5
E5 error and thermostat indicates that minimum flow temperature or boiler protection limit has been violated.
Boiler Flow Temperature Protection Error (via eBUS)
E6
E6 error and thermostat indicates internal humidity sensor fault (on models with humidity control).
Internal Humidity Sensor Failure
E7
E7 error and thermostat cannot detect presence or motion for occupancy-based control.
Occupancy / PIR Sensor Failure
E8
E8 error and thermostat cannot control or detect smart radiator valves (SRVs) in the system.
Smart Radiator Valve Communication Error
E9
E9 error and thermostat indicates that maximum number of devices or zones has been exceeded.
System Capacity / Addressing Error
F0
Thermostat display shows F0 and heating system does not respond to temperature changes.
Internal Sensor Configuration Error
F1
Thermostat shows F1 and does not display room temperature; heating may run continuously or not at all.
Internal Room Temperature Sensor Failure
F2
F2 displayed and thermostat cannot read floor temperature in underfloor heating mode.
Floor Sensor Open Circuit
F3
F3 error and floor temperature reading is extremely high or low, causing heating to shut down.
Floor Sensor Short Circuit
F4
Thermostat shows F4 and cannot communicate with the Protherm boiler; heating does not start on demand.
eBUS / OpenTherm Communication Failure
F5
F5 displayed and thermostat cannot control domestic hot water (DHW) functions on compatible Protherm boilers.
DHW Communication or Configuration Error
F6
Thermostat shows F6 and cannot detect external room sensor when configured to use one.
External Room Sensor Open Circuit
F7
F7 error and thermostat shows unrealistic external temperature or cannot read outdoor sensor.
Outdoor Temperature Sensor Fault
F8
Thermostat displays F8 and cannot control heating zones via external zone module.
Zone Module Communication Error
F9
F9 error and thermostat cannot control wireless relay or receiver; heating does not switch on.
Wireless Receiver Communication Loss
FA
Thermostat shows FA and schedules or settings are frequently lost after power interruptions.
Non-Volatile Memory Error
FB
FB error and thermostat cannot connect to Wi‑Fi or Protherm cloud services.
Wi‑Fi Module Failure or Configuration Error
FC
FC error and thermostat time/date frequently resets or drifts significantly.
Real-Time Clock (RTC) or Backup Power Failure
FD
FD error and thermostat cannot drive heating relay or boiler demand output.
Relay Output Failure
FE
FE error and thermostat becomes unresponsive or frequently restarts.
Overtemperature Protection / Internal Overheat
FF
FF error and thermostat display is blank or frozen, with occasional brief restarts.
Firmware Corruption / Boot Failure
Symptom
Boiler runs continuously and does not turn off even when the set temperature is reached.
Stuck Heating Demand / Relay Welded Closed
Symptom
Thermostat backlight or display is very dim or flickers intermittently.
Display / Backlight Power Issue
Symptom
Thermostat buttons or touchscreen areas do not respond or respond intermittently.
User Interface / Keypad Failure
Symptom
Thermostat causes boiler to short-cycle (frequent on/off) leading to noise and inefficiency.
Improper Cycle Rate / Hysteresis Settings
Symptom
Thermostat causes interference with nearby audio equipment or radio when switching.
Electromagnetic Interference (EMI) from Switching Components
Symptom
Thermostat display is completely blank and does not respond to button presses.
No Power to Thermostat
Symptom
Thermostat does not follow programmed schedule and remains at one temperature all day.
Scheduling / Program Logic Fault
Symptom
Thermostat emits a buzzing or humming noise, especially when switching.
Relay or Transformer Acoustic Noise
Symptom
Thermostat fails to detect or control Protherm-compatible accessories (e.g. external sensors, zone modules) after installation.
Accessory Detection / Bus Configuration Issue
Symptom
Thermostat frequently disconnects from Wi‑Fi and loses connection to the mobile app.
Intermittent Wi‑Fi Connectivity
Symptom
Thermostat is powered but does not turn the boiler on even when room temperature is below setpoint.
No Heat Demand Output
Symptom
Thermostat or surrounding wall feels unusually warm to the touch during normal operation.
Internal Overheating / High Power Dissipation
Symptom
Thermostat randomly resets to factory settings, losing Wi‑Fi and schedule configuration.
Unintended Factory Reset / Memory Instability
Symptom
Thermostat shows room temperature much higher or lower than actual, causing discomfort.
Temperature Measurement Inaccuracy
Symptom
Underfloor heating controlled by the thermostat is slow to warm up or some zones remain cold.
Underfloor Heating Control / Actuator Issue
| Error Code | Symptom | Fault Type | Guide |
|---|---|---|---|
| E1 |
E1 error and thermostat shows very low or negative room temperature values.
|
Room Sensor Calibration Error | View Details |
| E2 |
E2 error and thermostat cannot control cooling mode on systems with reversible heat pumps.
|
Cooling Mode Configuration / Output Error | View Details |
| E3 |
E3 error and thermostat indicates low supply voltage or frequently reboots when boiler starts.
|
Low Voltage Supply / Power Input Error | View Details |
| E4 |
E4 error and thermostat indicates that maximum floor temperature limit has been exceeded.
|
Floor Overtemperature Protection Triggered | View Details |
| E5 |
E5 error and thermostat indicates that minimum flow temperature or boiler protection limit has been violated.
|
Boiler Flow Temperature Protection Error (via eBUS) | View Details |
| E6 |
E6 error and thermostat indicates internal humidity sensor fault (on models with humidity control).
|
Internal Humidity Sensor Failure | View Details |
| E7 |
E7 error and thermostat cannot detect presence or motion for occupancy-based control.
|
Occupancy / PIR Sensor Failure | View Details |
| E8 |
E8 error and thermostat cannot control or detect smart radiator valves (SRVs) in the system.
|
Smart Radiator Valve Communication Error | View Details |
| E9 |
E9 error and thermostat indicates that maximum number of devices or zones has been exceeded.
|
System Capacity / Addressing Error | View Details |
| F0 |
Thermostat display shows F0 and heating system does not respond to temperature changes.
|
Internal Sensor Configuration Error | View Details |
| F1 |
Thermostat shows F1 and does not display room temperature; heating may run continuously or not at all.
|
Internal Room Temperature Sensor Failure | View Details |
| F2 |
F2 displayed and thermostat cannot read floor temperature in underfloor heating mode.
|
Floor Sensor Open Circuit | View Details |
| F3 |
F3 error and floor temperature reading is extremely high or low, causing heating to shut down.
|
Floor Sensor Short Circuit | View Details |
| F4 |
Thermostat shows F4 and cannot communicate with the Protherm boiler; heating does not start on demand.
|
eBUS / OpenTherm Communication Failure | View Details |
| F5 |
F5 displayed and thermostat cannot control domestic hot water (DHW) functions on compatible Protherm boilers.
|
DHW Communication or Configuration Error | View Details |
| F6 |
Thermostat shows F6 and cannot detect external room sensor when configured to use one.
|
External Room Sensor Open Circuit | View Details |
| F7 |
F7 error and thermostat shows unrealistic external temperature or cannot read outdoor sensor.
|
Outdoor Temperature Sensor Fault | View Details |
| F8 |
Thermostat displays F8 and cannot control heating zones via external zone module.
|
Zone Module Communication Error | View Details |
| F9 |
F9 error and thermostat cannot control wireless relay or receiver; heating does not switch on.
|
Wireless Receiver Communication Loss | View Details |
| FA |
Thermostat shows FA and schedules or settings are frequently lost after power interruptions.
|
Non-Volatile Memory Error | View Details |
| FB |
FB error and thermostat cannot connect to Wi‑Fi or Protherm cloud services.
|
Wi‑Fi Module Failure or Configuration Error | View Details |
| FC |
FC error and thermostat time/date frequently resets or drifts significantly.
|
Real-Time Clock (RTC) or Backup Power Failure | View Details |
| FD |
FD error and thermostat cannot drive heating relay or boiler demand output.
|
Relay Output Failure | View Details |
| FE |
FE error and thermostat becomes unresponsive or frequently restarts.
|
Overtemperature Protection / Internal Overheat | View Details |
| FF |
FF error and thermostat display is blank or frozen, with occasional brief restarts.
|
Firmware Corruption / Boot Failure | View Details |
| – |
Boiler runs continuously and does not turn off even when the set temperature is reached.
|
Stuck Heating Demand / Relay Welded Closed | View Details |
| – |
Thermostat backlight or display is very dim or flickers intermittently.
|
Display / Backlight Power Issue | View Details |
| – |
Thermostat buttons or touchscreen areas do not respond or respond intermittently.
|
User Interface / Keypad Failure | View Details |
| – |
Thermostat causes boiler to short-cycle (frequent on/off) leading to noise and inefficiency.
|
Improper Cycle Rate / Hysteresis Settings | View Details |
| – |
Thermostat causes interference with nearby audio equipment or radio when switching.
|
Electromagnetic Interference (EMI) from Switching Components | View Details |
| – |
Thermostat display is completely blank and does not respond to button presses.
|
No Power to Thermostat | View Details |
| – |
Thermostat does not follow programmed schedule and remains at one temperature all day.
|
Scheduling / Program Logic Fault | View Details |
| – |
Thermostat emits a buzzing or humming noise, especially when switching.
|
Relay or Transformer Acoustic Noise | View Details |
| – |
Thermostat fails to detect or control Protherm-compatible accessories (e.g. external sensors, zone modules) after installation.
|
Accessory Detection / Bus Configuration Issue | View Details |
| – |
Thermostat frequently disconnects from Wi‑Fi and loses connection to the mobile app.
|
Intermittent Wi‑Fi Connectivity | View Details |
| – |
Thermostat is powered but does not turn the boiler on even when room temperature is below setpoint.
|
No Heat Demand Output | View Details |
| – |
Thermostat or surrounding wall feels unusually warm to the touch during normal operation.
|
Internal Overheating / High Power Dissipation | View Details |
| – |
Thermostat randomly resets to factory settings, losing Wi‑Fi and schedule configuration.
|
Unintended Factory Reset / Memory Instability | View Details |
| – |
Thermostat shows room temperature much higher or lower than actual, causing discomfort.
|
Temperature Measurement Inaccuracy | View Details |
| – |
Underfloor heating controlled by the thermostat is slow to warm up or some zones remain cold.
|
Underfloor Heating Control / Actuator Issue | View Details |
No matching codes found
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