Short answer
The Ferroli Domicondens F24 D It is a wall-mounted condensing combi boiler (heating and domestic hot water) of 24 kW natural gas or LPG, with a sealed chamber, forced ventilation, and microprocessor control with a digital display. It belongs to the platform Ferroli Domi condensing (DOMIcondens / DOMIproject D family), which shares a fault code architecture type A (permanent lockout, requires RESET) and type F (temporary lockout, auto-reset when the value returns to the normal range).
Error code table for the Domicondens F24 D
Quick summary of all fault codes. Below you have the details of each one with its cause and solution.
| Code | Meaning |
|---|---|
| A01 | Ignition fault — the burner does not ignite |
| A02 | Flame signal present with burner off |
| A03 | Activation of overtemperature protection |
| A06 | No flame after the ignition phase (lockout after failed attempts) |
| A09 | Fault with the gas valve |
| A16 | Gas valve fault (second lockout) |
| A21 | Combustion anomaly (accumulation of faults F20) |
| A23 | Error in the parameters of the PCB |
| A24 | Error in the parameters of the PCB (second parameter) |
| A41 | Sensor location error |
| A51 | Combustion anomaly due to blockage |
| F04 | Flue thermostat anomaly or control board parameter |
| F05 | Fan or air pressure switch anomaly |
| F07 | Excessive flue gas temperature or control board parameter |
| F10 | Flow sensor 1 anomaly (heating) |
| F11 | Domestic hot water sensor anomaly |
| F14 | Flow sensor 2 anomaly |
| F20 | Combustion control anomaly |
| F34 | Supply voltage below 180 V |
| F35 | Incorrect power supply frequency |
| F37 | Incorrect water system pressure (low pressure) |
| F39 | External sensor anomaly (ambient temperature) |
| F42 | Activation of the heat exchanger protection (heating sensor) |
| F43 | Activation of the heat exchanger protection (circulation) |
| F50 | Gas valve anomaly (modulating actuator) |
What can you check yourself?
Some alerts can be resolved with simple and safe checks: replenishing the water pressure, bleeding the air from the radiators, checking that the gas valve is open, or resetting the boiler after a temporary lockout. If the code reappears after doing this, there is an underlying cause that should be reviewed by a qualified technician. Do not manipulate internal gas components nor electronics.
How to replenish the pressure step by step
- Locate the filling valve under the boiler.
- Open it slowly while observing the pressure gauge.
- Close the valve upon arrival at between 1 and 1.5 bar in cold.
- Bleed the radiators starting with the furthest one and check the pressure again.
- Reset the boiler; if the pressure warning disappears, the problem was resolved.
All fault codes and their solution
A01 — Ignition fault — the burner does not ignite
Why does it appear: Lack of gas supply, air in the pipes, dirty or poorly positioned ignition electrode, faulty gas valve, disconnected valve wiring, insufficient ignition power, or blocked condensate trap
What to do: Check the gas supply and bleed the air from the pipes. Verify the position and condition of the ignition electrode. If the issue persists, a qualified technician should inspect the gas valve and electrical connections. Press RESET after resolving the cause.
Affected component: Ignition/Ionisation Electrode
A02 — Flame signal present with burner off
Why does it appear: Faulty ionisation electrode, short circuit in the electrode wiring, or fault in the control board.
What to do: A qualified technician should check the wiring of the ionisation electrode, verify that it has no deposits, and inspect the control board. Press RESET after the intervention.
Affected component: Ignition/Ionisation Electrode
A03 — Activation of overtemperature protection
Why does it appear: Damaged heating sensor, absence of water circulation, air in the installation, or incorrect control board parameter
What to do: Check that the circulating pump is functioning correctly and bleed the air from the system. A qualified technician should verify the heating sensor and the parameters of the PCB. Press RESET after resolving.
Affected component: Temperature sensor
A06 — No flame after ignition phase (lockout after failed attempts)
Why does it appear: Insufficient gas pressure, incorrect regulation of the burner's minimum pressure, defective deflector, obstructed flue duct, or repeated fault F20
What to do: Check the gas pressure in the installation. A qualified technician should verify the burner pressure, the condition of the baffle, and the flue duct. Press RESET after resolving.
Related spare part: Gas valve
A09 — Gas valve fault
Why does it appear: Gas valve wiring interrupted or short-circuited, defective gas valve
What to do: A qualified technician should check the electrical connections of the gas valve and replace it if necessary. Press RESET after the intervention.
Related spare part: Gas valve
A16 — Gas valve fault (second lockout)
Why does it appear: Defective gas valve or fault in the opening/closing of the actuator
What to do: A qualified technician should inspect and replace the gas valve if necessary. Press RESET after the intervention.
Related spare part: Gas valve
A21 — Combustion anomaly (accumulation of faults F20)
Why does it appear: Fault F20 has occurred 6 times in 10 minutes; possible fault with the fan or the deflector.
What to do: Check the cause of fault F20. A qualified technician should inspect the fan, the deflector, and the flue duct. Press RESET after resolving the root cause.
Affected component: Fan / extractor
A23 — Error in the parameters of the PCB
Why does it appear: Incorrect configuration parameter of the card
What to do: A qualified technician must verify and correct the parameters of the PCB. Press RESET after modification.
Related spare part: PCB (control board)
A24 — Error in the parameters of the PCB (second parameter)
Why does it appear: Incorrect configuration parameter of the card
What to do: A qualified technician must verify and correct the parameters of the PCB. Press RESET after modification.
Related spare part: PCB (control board)
A41 — Sensor location error
Why does it appear: Flow sensor or domestic hot water (DHW) sensor detached from the pipe
What to do: A qualified technician should check that the sensors are properly attached to the pipe and verify their operation. Press RESET after the correction.
Affected component: Temperature sensor
A51 — Combustion anomaly due to blockage
Why does it appear: Obstruction in the air intake or flue gas exhaust duct
What to do: A qualified technician should inspect and clean the intake and exhaust ducts. Press RESET after resolving.
Affected component: Fan / extractor
F04 — Flue thermostat anomaly or control board parameter
Why does it appear: Incorrectly configured card parameter, flue thermostat contact open, incorrectly sized flue duct
What to do: A qualified technician should verify the card parameter and check the flue thermostat and the exhaust duct. The fault resets automatically when the value returns to the normal range.
Related spare part: PCB (control board)
F05 — Fan or air pressure switch anomaly
Why does it appear: Incorrect card parameter, faulty or disconnected fan, defective air pressure switch, obstructed flue duct
What to do: A qualified technician should check the fan, its electrical connections, and the air pressure switch. Also verify the flue duct. The fault resets automatically.
Affected component: Fan / extractor
F07 — Excessive flue gas temperature or control board parameter
Why does it appear: Incorrectly configured card parameter, partially obstructed flue duct, or faulty flue sensor
What to do: A qualified technician should check the control board parameters and inspect the flue duct and the flue gas temperature sensor. The fault resets automatically.
Affected component: Temperature sensor
F10 — Flow sensor 1 anomaly (heating)
Why does it appear: Damaged sensor, wiring short-circuited or disconnected
What to do: A qualified technician should check the sensor wiring and replace it if it is defective. The fault resets automatically when the sensor returns to the correct range.
Affected component: Temperature sensor
F11 — Domestic hot water sensor fault
Why does it appear: Damaged sensor, wiring short-circuited or disconnected
What to do: A qualified technician should check the wiring of the DHW sensor and replace it if necessary. The fault resets automatically.
Affected component: Temperature sensor
F14 — Flow sensor 2 anomaly
Why does it appear: Damaged sensor, wiring short-circuited or disconnected
What to do: A qualified technician should check the wiring and replace the sensor if it is defective. The fault resets automatically.
Affected component: Temperature sensor
F20 — Combustion control anomaly
Why does it appear: Obstruction in the flue duct, incorrect sizing of the duct, disconnected wiring, gas valve fault, fan fault, or blocked baffle
What to do: A qualified technician should check the deflector and replace it if necessary, verify the flue, the gas valve, and the fan. The fault resets automatically if the cause is resolved.
Affected component: Fan / extractor
F34 — Supply voltage below 180 V
Why does it appear: Problems in the electrical supply network
What to do: Check the home's electrical installation. If the mains voltage is correct, a qualified technician should check the boiler's power supply wiring. The fault resets automatically.
Affected component: Electrical installation
F35 — Incorrect supply frequency
Why does it appear: Stability issues in the electrical grid
What to do: Check the electrical installation. If the mains frequency is correct and the error persists, a qualified technician should inspect the equipment. The fault resets automatically.
Affected component: Electrical installation
F37 — Incorrect water pressure in the system (low pressure)
Why does it appear: Insufficient pressure in the heating circuit, water pressure switch damaged or disconnected
What to do: Fill the system until it reaches between 1.0 and 1.5 bar with the system cold. If the pressure repeatedly drops, there may be a leak; consult a technician. Also check the connection of the pressure switch.
Related spare part: Pressure sensor / filling key
F39 — External sensor anomaly (ambient temperature)
Why does it appear: Damaged outdoor sensor, wiring short-circuited, sensor disconnected after activating adaptive temperature.
What to do: Reconnect the outdoor sensor or deactivate the sliding temperature function. A qualified technician should check the wiring and replace the sensor if it is defective. The fault resets automatically.
Affected component: Temperature sensor
F42 — Activation of heat exchanger protection (heating sensor)
Why does it appear: Heating sensor fault, absence of water or air circulation in the installation
What to do: A qualified technician should replace the sensor if it is defective, check the operation of the circulating pump, and bleed the air from the system. The fault resets automatically.
Affected component: Heat exchanger
F43 — Activation of heat exchanger protection (circulation)
Why does it appear: No water circulation in the system, air in the heating circuit, or circulator pump fault
What to do: Check that the circulating pump is working and bleed the air from the system. A qualified technician should inspect the pump if the fault persists. The fault resets automatically.
Related spare part: Circulation pump
F50 — Gas valve anomaly (modulating actuator)
Why does it appear: Wiring of the modulating gas valve actuator interrupted or defective gas valve
What to do: A qualified technician should check the connections of the modulating actuator and replace the gas valve if necessary. The fault resets automatically.
Related spare part: Gas valve
When to call a technician
Fault codes related to sensors, electronics, gas valve, fan, or flue gas evacuation require a qualified technician with the appropriate equipment. If the same fault code reappears after a reset, or if the pressure drops repeatedly, a professional inspection is advisable. In Uniclima do you find spare parts for this boiler.
Frequently Asked Questions
Type A faults cause a permanent lockout that does not recover on its own. To reset it, press the RESET button for approximately one second. If the fault reappears after resetting, do not attempt more than twice: the underlying cause has not been resolved and it is advisable to call a qualified technician.
The F37 code indicates insufficient pressure in the heating circuit. With the system cold, the pressure should be between 1.0 and 1.5 bar. You can refill the circuit by slowly opening the filling valve until reaching that value and then closing it again. If the pressure drops frequently, there may be a leak in the installation, and a technician should inspect it.
Type A faults (e.g., A01, A03, A09) cause a permanent lockout: the boiler does not resume operation on its own and requires pressing the RESET button manually. Type F faults (e.g., F37, F43, F10) are temporary lockouts that automatically reset as soon as the value causing the problem returns to the normal range, although the underlying cause may persist.
The A01 indicates that the burner has failed to ignite within the allowed attempts. Even if there is gas, the fault may be due to a dirty or misaligned ignition electrode, loose connections on the gas valve, air in the gas pipe (common after a supply interruption), or a blocked condensate trap. Press RESET once; if the error returns, a qualified technician should diagnose the responsible component.