- Boilers
- Gas boiler
A03
Ferroli A03 on a gas boiler: overtemperature protection
Risk level
High
Professional inspection is recommended.
Urgency
High
Quick answer
On the DIVAtop MICRO LN F, A03 means the overtemperature protection tripped and the boiler locked out. Check the pressure gauge and do one reset with RESET. If it returns, call the service centre.
Safety first
Stop and check this first
- Do not reset repeatedly if A03 returns: it is a safety protection, and Ferroli says the fault must be eliminated if the boiler does not restart.
- If you smell gas: do not switch lights or appliances on or off, do not use flames or a phone indoors, open doors and windows if you can on your way out, leave the home and call your gas supplier's emergency number or the emergency services from outside.
Safe checks you can perform
- Your exact Ferroli boiler model
- Pressure gauge with the system cold
- One reset with the RESET button
- Inspection by a qualified gas technician
Leave these tasks to a qualified professional
- Do not attempt this professional task: Check the circulating pump
- Do not attempt this professional task: Vent the system
- Do not attempt this professional task: Verify the heating sensor
What a technician must be able to justify
Technician visit
These are the steps they must carry out and show you. Tick them as they work: if steps are skipped, do not accept a part swap.
These are not instructions for opening or handling the equipment yourself. They are the checks that should support a technical conclusion.
Check the circulating pump
What they doThe technician verifies that the circulating pump runs and moves water through the system.
They must show youthe pump running after the check.
In writingthe pump's condition and whether it was replaced.
Vent the system
What they doThe technician vents air from the heating circuit and checks the cold pressure again.
They must show youthe final pressure on the gauge.
In writingthat the system was vented and the resulting pressure.
Verify the heating sensor
What they doThe technician checks the sensor's position on the pipe and its operation with a multimeter against the manufacturer's specification.
They must show youthe measured value against the specification.
In writingthe sensor part number if replaced and the reason.
Before accepting a part or repair
Nothing has been shown yet. Do not accept a part swap based on the code alone.
Follow these steps
Note: Follow the documented order. An error code identifies the affected system, but it does not prove by itself which part has failed.
Your exact Ferroli boiler model
- Who:
- you.
- How:
- find the model name on the front or on the rating plate, without opening the casing, and compare it with your boiler's manual.
- Result that matters:
- confirming what A03 means on your model.
- If it is a DIVAtop MICRO LN F:
- A03 is the overtemperature protection.
- If it is another model:
- check the fault table in its manual before following this page.
- Evidence to keep:
- photo of the rating plate and of the code.
Evidence: Ferroli DIVAtop MICRO LN F instrucciones de uso instalación y mantenimiento
Pressure gauge with the system cold
- Who:
- you.
- How:
- with the heating cold, read the pressure gauge at the bottom of the boiler or the display. Ferroli gives a filling pressure of approx. 1 bar with the system cold.
- Result that matters:
- whether the pressure is at its value or below it.
- If it is low:
- follow the Ferroli F37 page to top up with the filling cock and close it afterwards; a system short of water may not circulate properly.
- If it is correct:
- low pressure does not explain A03; move on to the next check.
- Evidence to keep:
- dated photo of the gauge.
Evidence: Ferroli DIVAtop MICRO LN F instrucciones de uso instalación y mantenimiento
One reset with the RESET button
- Who:
- you.
- How:
- press the RESET button on the panel for 1 second. Ferroli says faults marked with the letter A cause a permanent shutdown that is cleared this way, and that if the boiler fails to start the fault must be eliminated first.
- Result that matters:
- whether A03 comes back.
- If the boiler starts and runs:
- note the date; if A03 returns another day, the technician must know it was reset before.
- If A03 returns:
- do not keep resetting; call the service centre.
- Evidence to keep:
- photo of the code before and after the reset.
Evidence: Ferroli DIVAtop MICRO LN F instrucciones de uso instalación y mantenimiento
Inspection by a qualified gas technician
- Who:
- a qualified gas technician, preferably from Ferroli's service network.
- How:
- checks that the circulating pump works, vents the air from the system and verifies the positioning and operation of the heating sensor.
- Result that matters:
- which branch of Ferroli's fault table is confirmed by measurements.
- If the cause is found:
- they should explain which measurement confirms it before replacing parts.
- If everything measures correctly and the code returns:
- they should move to the next cause in the table, not replace parts at random.
- Evidence to keep:
- job sheet with the measurements and parts replaced.
Opening the casing or touching the gas valve, electrode, burner or flue is work for the technician only. Ferroli says to disconnect the electrical power supply and close the gas cock upstream before any operation inside the boiler.
Evidence: Ferroli DIVAtop MICRO LN F instrucciones de uso instalación y mantenimiento
Still not solved
If the error persists, stop here. See what the technician must do and show you.
Where this code applies
A code is meaningful only inside the right product and version context.
Primary scope
- System
- Boilers
- Brand
- Ferroli
- Product type
- Gas boiler
Known code variants
- A-03
- Anomalía A03 Ferroli
- Beretta A 03
- calentador Cointra A03
- Ciao Green A03
- Cointra A03
- Cointra water heater A03
- CPE T A03
- Error A03 Beretta
- Error A03 Ferroli
- Ferroli A03
- Ferroli A03 boiler
- Ferroli A03 caldera
- Ferroli error A03
- Supreme E TS A03
What it means
On the DIVAtop MICRO LN F, Ferroli defines A03 as overtemperature protection activation. Possible causes are a damaged heating sensor, no water circulation in the system (circulating pump) and air in the system. It is an A code, a permanent lockout. On other Ferroli models A03 can mean something else, so confirm your model. The code does not say which of the three causes tripped it.
Warnings and stop conditions
- Higheditorial warning
Do not reset repeatedly if A03 returns: it is a safety protection, and Ferroli says the fault must be eliminated if the boiler does not restart.
Evidence: Ferroli DIVAtop MICRO LN F instrucciones de uso instalación y mantenimiento
- Criticaleditorial warning
If you smell gas: do not switch lights or appliances on or off, do not use flames or a phone indoors, open doors and windows if you can on your way out, leave the home and call your gas supplier's emergency number or the emergency services from outside.
Evidence: Ferroli DIVAtop MICRO LN F instrucciones de uso instalación y mantenimiento
Symptoms and causes
Probable causes · in order
- No water circulation in the systemPossible
Ferroli says to check the circulating pump. It fits if the radiators stay cold while the boiler heats up.
Evidence: Ferroli DIVAtop MICRO LN F instrucciones de uso instalación y mantenimiento
- Air in the systemPossible
Ferroli says to vent the system. It fits after topping up water or after work on the heating.
Evidence: Ferroli DIVAtop MICRO LN F instrucciones de uso instalación y mantenimiento
- Damaged heating sensorPossible
Ferroli says to check its positioning and operation. It is confirmed by measurement, not by eye.
Evidence: Ferroli DIVAtop MICRO LN F instrucciones de uso instalación y mantenimiento
Virtual technician
Does A03 still appear after these checks?
Answer a few questions to narrow down the likely cause and the safest next action. Guidance only - it never replaces a professional.
Sources and technical references
- 1
Ferroli DIVAtop MICRO LN F instrucciones de uso instalación y mantenimiento
Ferroli · 2015 · manual
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