Glow-worm
Glow-worm 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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F.01
Room thermostat display shows F.01 and will not control heating
Internal Temperature Sensor Fault
F.02
Thermostat shows F.02 and boiler does not respond to heat demands
Room Sensor Short Circuit / Out of Range
F.03
Thermostat displays F.03 and cannot detect room temperature correctly
External Room Sensor Fault (if fitted)
F.04
Smart thermostat shows F.04 and cannot communicate with the boiler
eBus Communication Failure
F.05
Thermostat shows F.05 and heating cannot be enabled
Relay / Output Fault in Thermostat or Receiver
F.06
Thermostat displays F.06 and loses wireless link to the receiver
RF Communication Loss
F.07
Smart thermostat shows F.07 and cannot connect to the internet
Wi‑Fi Connection Failure
F.08
Thermostat shows F.08 and app cannot access heating data
Cloud / Server Communication Error
F.09
Thermostat displays F.09 and schedules cannot be saved
Internal Memory / EEPROM Error
F.10
Thermostat shows F.10 and backlight flickers or unit reboots randomly
Power Supply / Voltage Fault
F.11
Thermostat displays F.11 and cannot detect boiler status
Boiler Status Feedback Fault
F.12
Thermostat shows F.12 and hot water control is unavailable in the app
Hot Water Sensor / Cylinder Sensor Fault
F.13
Thermostat displays F.13 and outdoor temperature is not shown
Outdoor Sensor Fault
F.14
Thermostat shows F.14 and cannot control heating zones correctly
Zone Configuration / Addressing Error
F.15
Thermostat displays F.15 and the time/date keep resetting
Real‑Time Clock / Backup Power Fault
F.16
Thermostat shows F.16 and cannot complete the firmware update
Firmware Update Failure
F.17
Thermostat displays F.17 and shows an incorrect room temperature
Calibration / Offset Error
F.18
Thermostat shows F.18 and the heating demand is locked out
Safety Lockout from Boiler Fault
F.19
Thermostat displays F.19 and cannot detect a heating circuit
No Heating Circuit Detected
F.20
Thermostat shows F.20 and the floor temperature control is disabled
Underfloor Heating Sensor Fault
Symptom
Boiler runs continuously even when the thermostat is set low or off
Stuck Heating Relay / Bypassed Control
Symptom
The thermostat fails to detect open windows, or eco features do not activate.
Comfort / Eco Feature Misconfiguration
Symptom
The thermostat shows condensation inside the display or housing.
Moisture Ingress
Symptom
Thermostat backlight or display flickers when boiler or other loads switch on
Electrical Interference / Poor Power Supply
Symptom
Thermostat batteries drain much faster than expected.
Excessive Power Consumption
Symptom
Thermostat calls for heat but the boiler does not fire
No Heat Demand Reaching Boiler
Symptom
Thermostat cannot be added to the Glow-worm app or account
Device Registration / Binding Issue
Symptom
Thermostat cannot be paired with the RF receiver during installation
Pairing / Binding Failure
Symptom
Thermostat display is completely dead; no lights or response
No Power to Thermostat
Symptom
Thermostat does not control hot water cylinder even though schedules are set
Hot Water Control Wiring / Configuration Fault
Symptom
Thermostat emits a burning smell or becomes unusually hot to touch
Overheating / Component Failure
Symptom
Thermostat frequently loses connection to the app but still controls heating locally
Intermittent Cloud / App Connectivity
Symptom
Thermostat randomly resets to factory settings, losing schedules
Intermittent Power / Memory Retention Issue
Symptom
Thermostat screen is on but unresponsive to touch or button presses
User Interface / Touch Panel Failure
Symptom
Thermostat shows a strong Wi‑Fi signal, but the app reports the device offline.
NAT / Port or Firewall Blocking
Symptom
Thermostat shows incorrect day/time or schedule runs at wrong times
Clock / Time Zone Misconfiguration
Symptom
Thermostat shows large temperature swings in rooms with underfloor heating
Improper Underfloor Heating Control
Symptom
Thermostat shows very slow response; rooms overshoot set temperature by several degrees
Poor Control Tuning / Location Issue
| Error Code | Symptom | Fault Type | Guide |
|---|---|---|---|
| F.01 |
Room thermostat display shows F.01 and will not control heating
|
Internal Temperature Sensor Fault | View Details |
| F.02 |
Thermostat shows F.02 and boiler does not respond to heat demands
|
Room Sensor Short Circuit / Out of Range | View Details |
| F.03 |
Thermostat displays F.03 and cannot detect room temperature correctly
|
External Room Sensor Fault (if fitted) | View Details |
| F.04 |
Smart thermostat shows F.04 and cannot communicate with the boiler
|
eBus Communication Failure | View Details |
| F.05 |
Thermostat shows F.05 and heating cannot be enabled
|
Relay / Output Fault in Thermostat or Receiver | View Details |
| F.06 |
Thermostat displays F.06 and loses wireless link to the receiver
|
RF Communication Loss | View Details |
| F.07 |
Smart thermostat shows F.07 and cannot connect to the internet
|
Wi‑Fi Connection Failure | View Details |
| F.08 |
Thermostat shows F.08 and app cannot access heating data
|
Cloud / Server Communication Error | View Details |
| F.09 |
Thermostat displays F.09 and schedules cannot be saved
|
Internal Memory / EEPROM Error | View Details |
| F.10 |
Thermostat shows F.10 and backlight flickers or unit reboots randomly
|
Power Supply / Voltage Fault | View Details |
| F.11 |
Thermostat displays F.11 and cannot detect boiler status
|
Boiler Status Feedback Fault | View Details |
| F.12 |
Thermostat shows F.12 and hot water control is unavailable in the app
|
Hot Water Sensor / Cylinder Sensor Fault | View Details |
| F.13 |
Thermostat displays F.13 and outdoor temperature is not shown
|
Outdoor Sensor Fault | View Details |
| F.14 |
Thermostat shows F.14 and cannot control heating zones correctly
|
Zone Configuration / Addressing Error | View Details |
| F.15 |
Thermostat displays F.15 and the time/date keep resetting
|
Real‑Time Clock / Backup Power Fault | View Details |
| F.16 |
Thermostat shows F.16 and cannot complete the firmware update
|
Firmware Update Failure | View Details |
| F.17 |
Thermostat displays F.17 and shows an incorrect room temperature
|
Calibration / Offset Error | View Details |
| F.18 |
Thermostat shows F.18 and the heating demand is locked out
|
Safety Lockout from Boiler Fault | View Details |
| F.19 |
Thermostat displays F.19 and cannot detect a heating circuit
|
No Heating Circuit Detected | View Details |
| F.20 |
Thermostat shows F.20 and the floor temperature control is disabled
|
Underfloor Heating Sensor Fault | View Details |
| – |
Boiler runs continuously even when the thermostat is set low or off
|
Stuck Heating Relay / Bypassed Control | View Details |
| – |
The thermostat fails to detect open windows, or eco features do not activate.
|
Comfort / Eco Feature Misconfiguration | View Details |
| – |
The thermostat shows condensation inside the display or housing.
|
Moisture Ingress | View Details |
| – |
Thermostat backlight or display flickers when boiler or other loads switch on
|
Electrical Interference / Poor Power Supply | View Details |
| – |
Thermostat batteries drain much faster than expected.
|
Excessive Power Consumption | View Details |
| – |
Thermostat calls for heat but the boiler does not fire
|
No Heat Demand Reaching Boiler | View Details |
| – |
Thermostat cannot be added to the Glow-worm app or account
|
Device Registration / Binding Issue | View Details |
| – |
Thermostat cannot be paired with the RF receiver during installation
|
Pairing / Binding Failure | View Details |
| – |
Thermostat display is completely dead; no lights or response
|
No Power to Thermostat | View Details |
| – |
Thermostat does not control hot water cylinder even though schedules are set
|
Hot Water Control Wiring / Configuration Fault | View Details |
| – |
Thermostat emits a burning smell or becomes unusually hot to touch
|
Overheating / Component Failure | View Details |
| – |
Thermostat frequently loses connection to the app but still controls heating locally
|
Intermittent Cloud / App Connectivity | View Details |
| – |
Thermostat randomly resets to factory settings, losing schedules
|
Intermittent Power / Memory Retention Issue | View Details |
| – |
Thermostat screen is on but unresponsive to touch or button presses
|
User Interface / Touch Panel Failure | View Details |
| – |
Thermostat shows a strong Wi‑Fi signal, but the app reports the device offline.
|
NAT / Port or Firewall Blocking | View Details |
| – |
Thermostat shows incorrect day/time or schedule runs at wrong times
|
Clock / Time Zone Misconfiguration | View Details |
| – |
Thermostat shows large temperature swings in rooms with underfloor heating
|
Improper Underfloor Heating Control | View Details |
| – |
Thermostat shows very slow response; rooms overshoot set temperature by several degrees
|
Poor Control Tuning / Location Issue | View Details |
No matching codes found
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