ErrorBase
Independent technical referenceOfficial site
  • Boilers
  • Gas boiler

A09

Ferroli A09 on a gas boiler: exchanger or overtemperature protection

Verified with sources2 sourcesReviewed Oct 3, 2026
Technician coming? See the 2 steps they must show you
Wall-mounted combi gas boiler installed in a home
Kai KemmannCC BY-SA 4.0Image source

Risk level

High

Professional inspection is recommended.

Urgency

High

Quick answer

The boiler tripped a protection for abnormal heating and locked out. Check the gauge pressure with the system cold and do one reset with RESET. If A09 returns, call the service centre.

Safety first

Stop and check this first

  • Do not reset repeatedly if A09 returns: it is a thermal protection and the cause must be corrected before the boiler is used again.
  • 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 circulation and vent
  • Do not attempt this professional task: Inspect exchanger or return 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.

  1. Check circulation and vent

    What they doThe technician verifies the circulating pump and the heating system and vents the air.

    They must show youthe pump running and the final pressure.

    In writingwhat was found and corrected.

  2. Inspect exchanger or return sensor

    What they doOn the HiTech the technician checks whether the exchanger is clogged; on the TECH RRT 28 C they measure the return sensor against the manufacturer's specification.

    They must show youthe measurement or condition observed.

    In writingthe part 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.

  1. Your exact Ferroli boiler model

    No special tools

    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 A09 means on your model.
    If it is a BlueHelix HiTech RRT C:
    A09 is the exchanger protection. If it is a BLUEHELIX TECH RRT 28 C: A09 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 BlueHelix HiTech RRT C instrucciones de uso instalación y mantenimiento · Ferroli BLUEHELIX TECH RRT 28 C instrucciones de uso instalación y mantenimiento

  2. Pressure gauge with the system cold

    No special tools

    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 A09; move on to the next check.
    Evidence to keep:
    dated photo of the gauge.

    Evidence: Ferroli BlueHelix HiTech RRT C instrucciones de uso instalación y mantenimiento · Ferroli BLUEHELIX TECH RRT 28 C instrucciones de uso instalación y mantenimiento

  3. One reset with the RESET button

    No special tools

    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 A09 comes back.
    If the boiler starts and runs:
    note the date; if A09 returns another day, the technician must know it was reset before.
    If A09 returns:
    do not keep resetting; call the service centre.
    Evidence to keep:
    photo of the code before and after the reset.

    Evidence: Ferroli BLUEHELIX TECH RRT 28 C instrucciones de uso instalación y mantenimiento

  4. Inspection by a qualified gas technician

    Tools required

    Who:
    a qualified gas technician, preferably from Ferroli's service network.
    How:
    checks the circulating pump and the system, vents the air and inspects the exchanger or the return sensor depending on the model.
    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 BlueHelix HiTech RRT C instrucciones de uso instalación y mantenimiento · Ferroli BLUEHELIX TECH RRT 28 C 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-09
  • A9
  • Anomalía A09 Ferroli
  • Beretta A 09
  • Ciao Green A09
  • Cointra A 09
  • Error A09 Beretta
  • Error A09 Cointra
  • Error A09 Ferroli
  • Ferroli A09
  • Ferroli A09 boiler
  • Ferroli A09 caldera
  • Ferroli error A09
  • Superlative A09

What it means

The meaning depends on the model. On the BlueHelix HiTech RRT C, Ferroli defines A09 as exchanger protection activation: no circulation, poor circulation with an abnormal rise of the flow sensor temperature, or a clogged exchanger. On the BLUEHELIX TECH RRT 28 C it is overtemperature protection activation: faulty return sensor, no circulation or air in the system. It is an A code, a lockout. It does not point to a specific part.

Warnings and stop conditions

  • Higheditorial warning

    Do not reset repeatedly if A09 returns: it is a thermal protection and the cause must be corrected before the boiler is used again.

    Evidence: Ferroli BlueHelix HiTech RRT C instrucciones de uso instalación y mantenimiento · Ferroli BLUEHELIX TECH RRT 28 C 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 BlueHelix HiTech RRT C instrucciones de uso instalación y mantenimiento

Symptoms and causes

Probable causes · in order

  • No water circulation in the systemPossible

    Common to both models. Ferroli says to check the circulating pump and the heating system.

    Evidence: Ferroli BlueHelix HiTech RRT C instrucciones de uso instalación y mantenimiento · Ferroli BLUEHELIX TECH RRT 28 C instrucciones de uso instalación y mantenimiento

  • Air in the systemPossible

    Ferroli says to vent the air. It fits after topping up water or a repair.

    Evidence: Ferroli BlueHelix HiTech RRT C instrucciones de uso instalación y mantenimiento · Ferroli BLUEHELIX TECH RRT 28 C instrucciones de uso instalación y mantenimiento

  • Clogged exchanger (HiTech)Possible

    On the BlueHelix HiTech RRT C, Ferroli says to check the exchanger and the system.

    Evidence: Ferroli BlueHelix HiTech RRT C instrucciones de uso instalación y mantenimiento

  • Faulty return sensor (TECH RRT 28 C)Possible

    On the BLUEHELIX TECH RRT 28 C, Ferroli says to check its position and operation.

    Evidence: Ferroli BLUEHELIX TECH RRT 28 C instrucciones de uso instalación y mantenimiento

Virtual technician

Does A09 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.

Start diagnosis

Sources and technical references

  1. 1

    Ferroli BlueHelix HiTech RRT C instrucciones de uso instalación y mantenimiento

    Ferroli · 2021 · manual

  2. 2

    Ferroli BLUEHELIX TECH RRT 28 C instrucciones de uso instalación y mantenimiento

    Ferroli · 2018 · manual

Sources: Ferroli BlueHelix HiTech RRT C instrucciones de uso instalación y mantenimiento · Ferroli BLUEHELIX TECH RRT 28 C instrucciones de uso instalación y mantenimientoreviewed 2026-10-03 · verified

Was this entry useful?