Protherm
Protherm Boilers Error Codes
Complete list of fault codes and troubleshooting guides. Use the search below to find your specific error.
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F0
Boiler displays F0 and will not start heating or providing hot water
Flow Temperature Sensor Fault / NTC Open or Short
F1
Boiler shows F1 and does not fire, no heating or hot water
Return Temperature Sensor Fault / NTC Open or Short
F10
Boiler displays F10, may start then shut down, temperature readings unstable
Flow/Return Temperature Difference Too High (ΔT Error)
F2
Boiler displays F2 and locks out shortly after starting or during operation
Overheat Thermostat / Safety Temperature Limiter Tripped
F20
Boiler shows F20 and shuts down, casing may feel very hot
General Overheating / Safety Cut‑out
F22
Boiler displays F22, no heating or hot water, pressure gauge near zero
Dry Fire / Low Water Content Protection
F23
Boiler shows F23, heating stops, flow and return temperatures differ greatly
Flow/Return Temperature Difference Too Large (Hydraulic Imbalance)
F24
Boiler displays F24, rapid temperature rise detected, boiler shuts down quickly
Low Flow / Pump Protection Error
F25
Boiler shows F25 and locks out, often accompanied by fan running at high speed
Flue Gas Overtemperature / Flue Blockage Detected
F26
Boiler displays F26, burner does not light or shuts down unexpectedly
Gas Valve Regulation Fault
F27
Boiler shows F27, ignition attempts fail or flame is detected at the wrong time
Flame Detection Error / False Flame Signal
F28
Boiler displays F28, repeated ignition attempts with clicking but no flame
Ignition Lockout / No Flame Establishment
F29
Boiler shows F29, flame is established then lost during operation
Flame Loss During Operation
F3
Boiler shows F3 and will not ignite, fan may not run
Flue Gas Temperature Sensor Fault / Flue NTC Error
F32
Boiler displays F32, fan may not start or runs erratically
Fan Speed Control Fault
F33
Boiler shows F33, fan runs but air pressure switch does not confirm airflow
Air Pressure Switch Not Switching
F37
Boiler displays F37, pressure gauge fluctuates or drops frequently
Low System Pressure / Frequent Pressure Loss
F38
Boiler shows F38, pressure reading abnormally high or unstable
Water Pressure Sensor Signal Error
F4
Boiler displays F4, burner does not light or goes out shortly after ignition attempt
Ignition Failure / Flame Not Detected
F41
Boiler displays F41, burner output limited or boiler shuts down under load
Flow Temperature Rise Too Fast / Pump or Flow Issue
F5
Boiler shows F5 and locks out, fan may run but no ignition
Air Pressure Switch Fault / Fan or Flue Pressure Error
F6
Boiler displays F6 and stops heating, temperature readings appear incorrect
Domestic Hot Water (DHW) Temperature Sensor Fault
F61
Boiler shows F61, no ignition, gas valve not operating correctly
Gas Valve Electrical Fault
F62
Boiler displays F62, gas valve may remain energized incorrectly after shutdown
Gas Valve Shut‑off Delay / PCB Control Fault
F7
Boiler shows F7, may attempt to start but shuts down quickly
Flow Sensor / Turbine Fault (DHW Flow Detection Error)
F70
Boiler shows F70 after PCB replacement or configuration change
Incompatible or Unconfigured PCB
F72
Boiler displays F72, inconsistent readings between flow and return sensors
Flow/Return NTC Mismatch or Fault
F73
Boiler shows F73, pressure reading too low or sensor open circuit
Water Pressure Sensor Open Circuit
F74
Boiler displays F74, pressure reading too high or sensor short circuit
Water Pressure Sensor Short Circuit
F8
Boiler displays F8 and will not operate, often associated with low or no system pressure
Low Water Pressure / Water Pressure Sensor Fault
F9
Boiler shows F9 and locks out, often after a power surge or wiring issue
EEPROM / PCB Configuration Error
Symptom
Boiler display works but buttons or controls do not respond
User Interface / Control Panel Fault
Symptom
Boiler does not start at all, no display or lights
No Power / Electrical Supply Fault
Symptom
Boiler frequently loses pressure and needs topping up every few days
Chronic Pressure Loss
Symptom
Boiler is very noisy (whining, grinding, or rattling) during operation
Mechanical Noise from Fan, Pump, or Burner
Symptom
Boiler leaking water from underneath the casing
Internal Water Leak
Symptom
Boiler makes loud banging or knocking noises (kettling) during operation
Kettling Due to Scale or Sludge in Heat Exchanger
Symptom
Boiler or flue emits unusual smells (burning, chemical, or exhaust‑like)
Combustion or Electrical Overheating Issue
Symptom
Boiler provides heating but no domestic hot water
DHW Priority / Diverter Valve Fault
Symptom
Boiler provides hot water but no central heating
Heating Circuit Isolation / Diverter Valve Stuck on DHW
Symptom
Boiler runs but radiators do not get hot or only partially warm
Poor Heating Performance / Circulation Problem
Symptom
Boiler starts but shuts down after a few seconds without showing an error code
Short Cycling / Unstable Operation
Symptom
Condensate water dripping from boiler casing or flue joints
Condensate Drainage / Flue Condensate Leak
Symptom
Domestic hot water temperature fluctuates between hot and cold during use
Unstable DHW Temperature Control
Symptom
Room thermostat calling for heat but boiler does not respond
Control Signal / External Thermostat Fault
| Error Code | Symptom | Fault Type | Guide |
|---|---|---|---|
| F0 |
Boiler displays F0 and will not start heating or providing hot water
|
Flow Temperature Sensor Fault / NTC Open or Short | View Details |
| F1 |
Boiler shows F1 and does not fire, no heating or hot water
|
Return Temperature Sensor Fault / NTC Open or Short | View Details |
| F10 |
Boiler displays F10, may start then shut down, temperature readings unstable
|
Flow/Return Temperature Difference Too High (ΔT Error) | View Details |
| F2 |
Boiler displays F2 and locks out shortly after starting or during operation
|
Overheat Thermostat / Safety Temperature Limiter Tripped | View Details |
| F20 |
Boiler shows F20 and shuts down, casing may feel very hot
|
General Overheating / Safety Cut‑out | View Details |
| F22 |
Boiler displays F22, no heating or hot water, pressure gauge near zero
|
Dry Fire / Low Water Content Protection | View Details |
| F23 |
Boiler shows F23, heating stops, flow and return temperatures differ greatly
|
Flow/Return Temperature Difference Too Large (Hydraulic Imbalance) | View Details |
| F24 |
Boiler displays F24, rapid temperature rise detected, boiler shuts down quickly
|
Low Flow / Pump Protection Error | View Details |
| F25 |
Boiler shows F25 and locks out, often accompanied by fan running at high speed
|
Flue Gas Overtemperature / Flue Blockage Detected | View Details |
| F26 |
Boiler displays F26, burner does not light or shuts down unexpectedly
|
Gas Valve Regulation Fault | View Details |
| F27 |
Boiler shows F27, ignition attempts fail or flame is detected at the wrong time
|
Flame Detection Error / False Flame Signal | View Details |
| F28 |
Boiler displays F28, repeated ignition attempts with clicking but no flame
|
Ignition Lockout / No Flame Establishment | View Details |
| F29 |
Boiler shows F29, flame is established then lost during operation
|
Flame Loss During Operation | View Details |
| F3 |
Boiler shows F3 and will not ignite, fan may not run
|
Flue Gas Temperature Sensor Fault / Flue NTC Error | View Details |
| F32 |
Boiler displays F32, fan may not start or runs erratically
|
Fan Speed Control Fault | View Details |
| F33 |
Boiler shows F33, fan runs but air pressure switch does not confirm airflow
|
Air Pressure Switch Not Switching | View Details |
| F37 |
Boiler displays F37, pressure gauge fluctuates or drops frequently
|
Low System Pressure / Frequent Pressure Loss | View Details |
| F38 |
Boiler shows F38, pressure reading abnormally high or unstable
|
Water Pressure Sensor Signal Error | View Details |
| F4 |
Boiler displays F4, burner does not light or goes out shortly after ignition attempt
|
Ignition Failure / Flame Not Detected | View Details |
| F41 |
Boiler displays F41, burner output limited or boiler shuts down under load
|
Flow Temperature Rise Too Fast / Pump or Flow Issue | View Details |
| F5 |
Boiler shows F5 and locks out, fan may run but no ignition
|
Air Pressure Switch Fault / Fan or Flue Pressure Error | View Details |
| F6 |
Boiler displays F6 and stops heating, temperature readings appear incorrect
|
Domestic Hot Water (DHW) Temperature Sensor Fault | View Details |
| F61 |
Boiler shows F61, no ignition, gas valve not operating correctly
|
Gas Valve Electrical Fault | View Details |
| F62 |
Boiler displays F62, gas valve may remain energized incorrectly after shutdown
|
Gas Valve Shut‑off Delay / PCB Control Fault | View Details |
| F7 |
Boiler shows F7, may attempt to start but shuts down quickly
|
Flow Sensor / Turbine Fault (DHW Flow Detection Error) | View Details |
| F70 |
Boiler shows F70 after PCB replacement or configuration change
|
Incompatible or Unconfigured PCB | View Details |
| F72 |
Boiler displays F72, inconsistent readings between flow and return sensors
|
Flow/Return NTC Mismatch or Fault | View Details |
| F73 |
Boiler shows F73, pressure reading too low or sensor open circuit
|
Water Pressure Sensor Open Circuit | View Details |
| F74 |
Boiler displays F74, pressure reading too high or sensor short circuit
|
Water Pressure Sensor Short Circuit | View Details |
| F8 |
Boiler displays F8 and will not operate, often associated with low or no system pressure
|
Low Water Pressure / Water Pressure Sensor Fault | View Details |
| F9 |
Boiler shows F9 and locks out, often after a power surge or wiring issue
|
EEPROM / PCB Configuration Error | View Details |
| – |
Boiler display works but buttons or controls do not respond
|
User Interface / Control Panel Fault | View Details |
| – |
Boiler does not start at all, no display or lights
|
No Power / Electrical Supply Fault | View Details |
| – |
Boiler frequently loses pressure and needs topping up every few days
|
Chronic Pressure Loss | View Details |
| – |
Boiler is very noisy (whining, grinding, or rattling) during operation
|
Mechanical Noise from Fan, Pump, or Burner | View Details |
| – |
Boiler leaking water from underneath the casing
|
Internal Water Leak | View Details |
| – |
Boiler makes loud banging or knocking noises (kettling) during operation
|
Kettling Due to Scale or Sludge in Heat Exchanger | View Details |
| – |
Boiler or flue emits unusual smells (burning, chemical, or exhaust‑like)
|
Combustion or Electrical Overheating Issue | View Details |
| – |
Boiler provides heating but no domestic hot water
|
DHW Priority / Diverter Valve Fault | View Details |
| – |
Boiler provides hot water but no central heating
|
Heating Circuit Isolation / Diverter Valve Stuck on DHW | View Details |
| – |
Boiler runs but radiators do not get hot or only partially warm
|
Poor Heating Performance / Circulation Problem | View Details |
| – |
Boiler starts but shuts down after a few seconds without showing an error code
|
Short Cycling / Unstable Operation | View Details |
| – |
Condensate water dripping from boiler casing or flue joints
|
Condensate Drainage / Flue Condensate Leak | View Details |
| – |
Domestic hot water temperature fluctuates between hot and cold during use
|
Unstable DHW Temperature Control | View Details |
| – |
Room thermostat calling for heat but boiler does not respond
|
Control Signal / External Thermostat Fault | View Details |
No matching codes found
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