CTC
CTC Boilers Error Codes
Complete list of fault codes and troubleshooting guides. Use the search below to find your specific error.
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E01
Boiler will not start; display shows E01 shortly after a heat or hot water demand.
Ignition Failure Lockout
E02
Boiler starts then shuts down with E02; burner lights briefly or not at all.
Flame Detection Failure
E03
Boiler locks out with E03; fan may run but burner does not ignite.
Air Pressure Switch / Fan Proving Fault
E04
Boiler shuts down with E04; temperature rises rapidly before lockout.
Primary Flow Overheat / Safety Thermostat Trip
E05
Boiler displays E05 and will not fire; flow temperature reading is implausible or fixed.
Flow Temperature Sensor (NTC) Fault
E06
Boiler shows E06; hot water temperature is unstable or boiler will not fire for DHW.
DHW Temperature Sensor (NTC) Fault
E07
Boiler locks out with E07; fan may start but ignition does not proceed.
Fan Speed / Tachometer Fault
E08
Boiler shows E08 and stops; system pressure gauge is low or fluctuating.
Low Water Pressure / Pressure Switch Fault
E09
Boiler displays E09; burner shuts down and will not restart until reset.
Gas Valve Control Fault
E10
Boiler shows E10; no heating or hot water; pump may run briefly.
Circulation Fault / No Flow Detected
E11
Boiler displays E11; DHW demand not recognised or intermittent.
DHW Flow Sensor / Turbine Fault
E12
Boiler shows E12; heating demand not recognised from room or cylinder controls.
External Control / Thermostat Input Fault
E13
Boiler displays E13; flue gas temperature too high or sensor fault.
Flue Gas Temperature Sensor Fault / Overtemperature
E14
Boiler shows E14; condensate may be present around the base; burner shuts down.
Condensate Drain Blocked
E15
Boiler displays E15; internal leak or water detected in base tray.
Water Leak / Safety Float Switch Activation
E16
Boiler shows E16; communication error between user interface and main PCB.
Communication Bus Fault
E17
Boiler displays E17; outdoor sensor reading is implausible or weather compensation not working.
Outdoor Temperature Sensor Fault
E18
Boiler shows E18; internal temperature too low or frost protection active.
Frost Protection / Low Internal Temperature Fault
E19
Boiler displays E19; power supply or internal fuse fault.
Low Voltage / Power Supply Error
E20
Boiler shows E20; return temperature sensor reading is implausible.
Return Temperature Sensor (NTC) Fault
E21
Boiler displays E21; diverter valve not reaching position or stuck.
Diverter Valve Position Fault
E22
Boiler shows E22; internal overcurrent or short-circuit detected on low-voltage outputs.
Peripheral Short-Circuit Protection
E23
Boiler displays E23; internal memory or configuration error.
Configuration / EEPROM Fault
E24
Boiler shows E24; sensor readings inconsistent or out of range.
General Sensor Calibration Fault
Symptom
Boiler display is blank or unreadable, but heating may still operate.
Display / User Interface Failure
Symptom
Boiler does not start at all; no display or lights on the control panel.
No Power / Dead Boiler
Symptom
Boiler emits a burning smell or plastic odour during operation.
Overheating Electrical Component
Symptom
Boiler frequently goes into frost protection mode even when the property is warm.
Incorrect Frost Detection
Symptom
Boiler frequently loses pressure and needs regular topping up via the filling loop.
Chronic Pressure Loss
Symptom
Boiler frequently short cycles when providing hot water; temperature at taps fluctuates.
DHW Temperature Instability
Symptom
Boiler ignites with a loud bang or pop (hard ignition).
Delayed Ignition
Symptom
Boiler is very noisy, with whistling or roaring sounds from the flue.
Combustion Noise / Flue Resonance
Symptom
Boiler leaking water from underneath the casing or onto the floor.
Internal Hydraulic Leak
Symptom
Boiler makes loud banging or knocking noises (kettling) during operation.
Heat Exchanger Kettling / Localised Boiling
Symptom
Boiler pressure rises rapidly when heating and the pressure relief valve discharges water.
Expansion Vessel Failure / Overpressure
Symptom
Boiler runs but produces no domestic hot water, or hot water is only lukewarm.
DHW Production Failure
Symptom
Boiler runs but some radiators remain cold or only heat at the top.
Airlock / Sludge in Radiators
Symptom
Boiler runs continuously and overshoots the room temperature setpoint.
Control / Thermostat Overshoot
Symptom
Boiler starts then shuts down after a few seconds without showing a specific error code.
Flame Instability / Early Flame Loss
Symptom
Radiators are only lukewarm and the boiler cycles on and off rapidly.
Poor Circulation / Short Cycling
| Error Code | Symptom | Fault Type | Guide |
|---|---|---|---|
| E01 |
Boiler will not start; display shows E01 shortly after a heat or hot water demand.
|
Ignition Failure Lockout | View Details |
| E02 |
Boiler starts then shuts down with E02; burner lights briefly or not at all.
|
Flame Detection Failure | View Details |
| E03 |
Boiler locks out with E03; fan may run but burner does not ignite.
|
Air Pressure Switch / Fan Proving Fault | View Details |
| E04 |
Boiler shuts down with E04; temperature rises rapidly before lockout.
|
Primary Flow Overheat / Safety Thermostat Trip | View Details |
| E05 |
Boiler displays E05 and will not fire; flow temperature reading is implausible or fixed.
|
Flow Temperature Sensor (NTC) Fault | View Details |
| E06 |
Boiler shows E06; hot water temperature is unstable or boiler will not fire for DHW.
|
DHW Temperature Sensor (NTC) Fault | View Details |
| E07 |
Boiler locks out with E07; fan may start but ignition does not proceed.
|
Fan Speed / Tachometer Fault | View Details |
| E08 |
Boiler shows E08 and stops; system pressure gauge is low or fluctuating.
|
Low Water Pressure / Pressure Switch Fault | View Details |
| E09 |
Boiler displays E09; burner shuts down and will not restart until reset.
|
Gas Valve Control Fault | View Details |
| E10 |
Boiler shows E10; no heating or hot water; pump may run briefly.
|
Circulation Fault / No Flow Detected | View Details |
| E11 |
Boiler displays E11; DHW demand not recognised or intermittent.
|
DHW Flow Sensor / Turbine Fault | View Details |
| E12 |
Boiler shows E12; heating demand not recognised from room or cylinder controls.
|
External Control / Thermostat Input Fault | View Details |
| E13 |
Boiler displays E13; flue gas temperature too high or sensor fault.
|
Flue Gas Temperature Sensor Fault / Overtemperature | View Details |
| E14 |
Boiler shows E14; condensate may be present around the base; burner shuts down.
|
Condensate Drain Blocked | View Details |
| E15 |
Boiler displays E15; internal leak or water detected in base tray.
|
Water Leak / Safety Float Switch Activation | View Details |
| E16 |
Boiler shows E16; communication error between user interface and main PCB.
|
Communication Bus Fault | View Details |
| E17 |
Boiler displays E17; outdoor sensor reading is implausible or weather compensation not working.
|
Outdoor Temperature Sensor Fault | View Details |
| E18 |
Boiler shows E18; internal temperature too low or frost protection active.
|
Frost Protection / Low Internal Temperature Fault | View Details |
| E19 |
Boiler displays E19; power supply or internal fuse fault.
|
Low Voltage / Power Supply Error | View Details |
| E20 |
Boiler shows E20; return temperature sensor reading is implausible.
|
Return Temperature Sensor (NTC) Fault | View Details |
| E21 |
Boiler displays E21; diverter valve not reaching position or stuck.
|
Diverter Valve Position Fault | View Details |
| E22 |
Boiler shows E22; internal overcurrent or short-circuit detected on low-voltage outputs.
|
Peripheral Short-Circuit Protection | View Details |
| E23 |
Boiler displays E23; internal memory or configuration error.
|
Configuration / EEPROM Fault | View Details |
| E24 |
Boiler shows E24; sensor readings inconsistent or out of range.
|
General Sensor Calibration Fault | View Details |
| – |
Boiler display is blank or unreadable, but heating may still operate.
|
Display / User Interface Failure | View Details |
| – |
Boiler does not start at all; no display or lights on the control panel.
|
No Power / Dead Boiler | View Details |
| – |
Boiler emits a burning smell or plastic odour during operation.
|
Overheating Electrical Component | View Details |
| – |
Boiler frequently goes into frost protection mode even when the property is warm.
|
Incorrect Frost Detection | View Details |
| – |
Boiler frequently loses pressure and needs regular topping up via the filling loop.
|
Chronic Pressure Loss | View Details |
| – |
Boiler frequently short cycles when providing hot water; temperature at taps fluctuates.
|
DHW Temperature Instability | View Details |
| – |
Boiler ignites with a loud bang or pop (hard ignition).
|
Delayed Ignition | View Details |
| – |
Boiler is very noisy, with whistling or roaring sounds from the flue.
|
Combustion Noise / Flue Resonance | View Details |
| – |
Boiler leaking water from underneath the casing or onto the floor.
|
Internal Hydraulic Leak | View Details |
| – |
Boiler makes loud banging or knocking noises (kettling) during operation.
|
Heat Exchanger Kettling / Localised Boiling | View Details |
| – |
Boiler pressure rises rapidly when heating and the pressure relief valve discharges water.
|
Expansion Vessel Failure / Overpressure | View Details |
| – |
Boiler runs but produces no domestic hot water, or hot water is only lukewarm.
|
DHW Production Failure | View Details |
| – |
Boiler runs but some radiators remain cold or only heat at the top.
|
Airlock / Sludge in Radiators | View Details |
| – |
Boiler runs continuously and overshoots the room temperature setpoint.
|
Control / Thermostat Overshoot | View Details |
| – |
Boiler starts then shuts down after a few seconds without showing a specific error code.
|
Flame Instability / Early Flame Loss | View Details |
| – |
Radiators are only lukewarm and the boiler cycles on and off rapidly.
|
Poor Circulation / Short Cycling | View Details |
No matching codes found
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