Short answer
The Ferroli Domicompact F24 It is a compact wall-mounted boiler from the same technical family as the Domiproject, and it shares its diagnostic system by codes. When a notification like A01, A03, or F37 appears, the display indicates where the problem is. In this guide, you have the meaning of each code, why it occurs, and how to act, as well as the exact spare part when the fault corresponds to a specific component. Remember: the codes A are lockouts (usually require reset) and the F they are anomalies of sensors, pressure, or electrical network.
Error code table for the Domicompact F24
Quick summary of all fault codes. Below you have the details of each one with its cause and solution.
| Code | Meaning |
|---|---|
| A01 | The burner does not ignite (ignition lockout) |
| A02 | Flame detected with the burner off |
| A03 | Overtemperature protection operation |
| A06 | The flame goes out after ignition. |
| F04 | Flue thermostat anomaly |
| F05 | The air pressure switch does not close contacts when the fan starts. |
| F10 | Heating sensor anomaly |
| F34 | Supply voltage below 170 V |
| F35 | Abnormal electrical grid frequency |
| F37 | Water pressure too low |
| F39 | Outdoor sensor anomaly |
| F40 | Water pressure too high |
| F47 | Water pressure transducer anomaly |
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 — The burner does not ignite (ignition lockout)
Why does it appear: Lack of gas or closed gas valve, ignition or detection electrode dirty or improperly positioned, defective gas valve, or insufficient ignition power.
What to do: Ensure the gas valve is open and there is supply, and reset the boiler. If the lockout repeats, a technician should check the electrodes, wiring, and gas valve.
Related spare part: Gas valve
A02 — Flame detected with the burner off
Why does it appear: Ionisation electrode fault or PCB fault, interpreting a non-existent flame.
What to do: Technical inspection of the ionisation electrode, its wiring, and the control board is needed.
Related spare part: PCB (control board)
A03 — Activation of overtemperature protection
Why does it appear: The heating sensor measures an excessive temperature: poor water circulation, blocked pump, air in the circuit, or faulty sensor.
What to do: Check the pressure and bleed the radiators. If it trips again, inspect the circulation pump and the heating sensor.
Related spare part: Circulation pump
A06 — The flame goes out after ignition
Why does it appear: Repeated flame separations after ignition: low gas pressure, dirty detection electrode, or poor combustion.
What to do: Check the gas supply. The gas regulation and the detection electrode should be inspected by a technician.
Related spare part: Gas valve
F04 — Flue thermostat anomaly
Why does it appear: Poor flue gas evacuation, obstructed duct, or defective flue thermostat (natural draught versions).
What to do: Never bypass the flue thermostat: it protects against poor gas exhaust. The duct and the thermostat need to be checked.
F05 — The air pressure switch does not close contacts when the fan starts
Why does it appear: Weak or faulty fan, blocked or loose pressure tube, obstructed flue, or defective air pressure switch (sealed versions).
What to do: You need to check the fan, the pressure tubes, and the air pressure switch.
Related spare part: Pressure sensor / filling key
F10 — Heating sensor anomaly
Why does it appear: Flow sensor in short circuit, open circuit, or poorly connected.
What to do: Check the wiring and, if necessary, replace the heating sensor.
Affected component: Temperature sensor
F34 — Supply voltage below 170 V
Why does it appear: Voltage drop in the network or faulty electrical installation.
What to do: Check the mains voltage. It is an issue with the electrical installation, not the boiler.
Affected component: Electrical installation
F35 — Abnormal mains frequency
Why does it appear: Anomaly in the power supply network.
What to do: Check the electrical installation and the supply network.
Affected component: Electrical installation
F37 — Water pressure too low
Why does it appear: Water loss in the circuit, lack of filling, or defective water pressure switch.
What to do: Replenish the pressure to 1-1.5 bar when cold using the filling key. If it drops repeatedly, there is a leak that needs to be located.
Related spare part: Pressure sensor / filling key
F39 — External sensor anomaly
Why does it appear: External temperature sensor disconnected or faulty (if installed).
What to do: Check the external sensor and its wiring, or deactivate it in the parameters if it is no longer in use.
Affected component: Temperature sensor
F40 — Water pressure too high
Why does it appear: Overfilling, expansion vessel without air pre-charge, or faulty safety valve.
What to do: Lower the pressure by bleeding a radiator to 1-1.5 bar when cold. If it rises on its own, check the expansion vessel.
Related spare part: Pressure sensor / filling key
F47 — Water pressure transducer anomaly
Why does it appear: Water pressure sensor or pressure switch faulty or with interrupted wiring.
What to do: Check the wiring and replace the water pressure sensor or pressure switch if it is defective.
Related spare part: Pressure sensor / filling key
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
The burner has not ignited. The usual causes are a lack of gas, the gas valve being closed, or a dirty ignition electrode. After checking the gas, you can reset; if it repeats, the electrodes and gas valve need to be checked.
On the control panel, using the function selector or the reset button. If the code reappears after resetting, do not insist: there is a fault that must be checked by a qualified technician.
The correct cold pressure is 1 to 1.5 bar. If it frequently drops, it usually indicates a leak in the installation or in the boiler, or an exhausted expansion vessel.
It's not advisable. The F04 affects the flue gas evacuation and the flue gas thermostat should never be bypassed. The duct and the thermostat need to be checked before using it normally again.