- Boilers
- Gas boiler
A08
Cointra A08 on a gas boiler: overheat protection tripped
Risk level
High
Professional inspection is recommended.
Urgency
High
Quick answer
Cointra A08 means the overheat protection has acted and the boiler has locked out. Read the gauge with the system cold, top up to 1 bar if it is below 0.8 bar and press reset for one second, once.
Safety first
Stop and check this first
- If you smell gas, do not reset: do not touch switches or light flames, open windows, close the gas tap if it is within reach, leave and call your gas distributor's emergency number from outside. Cointra says to switch the boiler off when it fails and to have it repaired only by an authorised technician.
- Do not chain resets with A08: it is a temperature safety cut. If it returns, leave the boiler off and wait for the technician. Do not open the boiler or touch the sensor, pump or expansion vessel.
Safe checks you can perform
- Gauge pressure with the system cold
- Cold radiators or air noises
- One reset with the reset key
- Sensor, pump and bleeding check by the technician
Leave these tasks to a qualified professional
- Do not attempt this professional task: Heating sensor check
- Do not attempt this professional task: Pump check and bleeding
- Do not attempt this professional task: Operating test and combustion check
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.
Heating sensor check
What they doThe technician checks the position and operation of the heating sensor and compares its reading with the Cointra table.
They must show youthe measured value against the manufacturer's specification.
In writingthe result and, if it is replaced, the part reference and why.
Pump check and bleeding
What they doThe technician checks that the circulator pump is not seized, that the expansion vessel is charged and bleeds the air from the system.
They must show youthe pump running and the pressure after bleeding.
In writingwhat was checked and corrected.
Operating test and combustion check
What they doAfter the repair, the technician runs the boiler on heating and checks the combustion parameters with an analyser, as Cointra asks at the end of maintenance.
They must show youthe boiler running without A08 and the analyser printout.
In writingthe measured values.
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.
Gauge pressure with the system cold
- Who:
- you.
- How:
- with the system cold, read the boiler gauge. Cointra asks for about 1 bar and to top up if it drops below 0.8 bar.
- Result that matters:
- whether pressure is below 0.8 bar.
- If it is low:
- turn the filling key anticlockwise up to 1 bar, always close it at the end and wait for the Fh air purge cycle.
- If it is correct:
- lack of water does not explain A08; carry on with the checks.
- Evidence to keep:
- a photo of the gauge before and after.
Evidence: Cointra SUPERLATIVE PLUS 24 C, instrucciones de uso, instalación y mantenimiento
Cold radiators or air noises
- Who:
- you.
- How:
- with heating called for, carefully feel whether the radiators warm up and listen for gurgling.
- Result that matters:
- whether water is circulating in the system.
- If the radiators stay cold:
- tell the technician; Cointra lists no circulation.
- If you hear air:
- tell the technician; Cointra lists air in the system.
- Evidence to keep:
- a note of which radiators heat and which do not.
Evidence: Cointra SUPERLATIVE PLUS 24 C, instrucciones de uso, instalación y mantenimiento
One reset with the reset key
- Who:
- you.
- How:
- press the reset key for one second, as Cointra describes for A letter faults. Do it once.
- Result that matters:
- whether the boiler restarts and A08 stays away.
- If it restarts:
- note the date; if A08 or F08 repeats, call the technician.
- If it does not restart or returns:
- Cointra says the fault must be fixed; call an authorised technician.
- Evidence to keep:
- a photo of the display with A08 and the time.
Evidence: Cointra SUPERLATIVE PLUS 24 C, instrucciones de uso, instalación y mantenimiento
Sensor, pump and bleeding check by the technician
- Who:
- authorised technician.
- How:
- checks the heating sensor, that the circulator is not seized, the expansion vessel, and bleeds the system.
- Result that matters:
- whether there was real overheating or the sensor is faulty.
- If the pump is seized or there is air:
- real overheating is confirmed.
- If the sensor does not read correctly:
- the sensor is replaced.
- Evidence to keep:
- a report of what was checked and any part replaced.
Cointra reserves repairs and part replacement for authorised technicians: sensor, pump and expansion vessel are inside the boiler.
Evidence: Cointra SUPERLATIVE PLUS 24 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
- Cointra
- Product type
- Gas boiler
Known code variants
- A 08
- A8
- Beretta A 08
- Bluehelix A08
- Ciao Green A08
- Cointra A 08
- Error A08 Beretta
- Error A08 Cointra
- Error A08 Ferroli
- F08 Ferroli
- Ferroli A 08
- Superlative A08
What it means
In the Superlative Plus fault table, F08 and A08 are the overheat protection acting. Cointra lists as possible causes a faulty heating sensor, no water circulating in the system and air in the system. F letter faults are temporary lockouts that clear by themselves; A letter faults are permanent lockouts cleared with the reset key. The code does not say whether the water really overheated or the sensor is faulty.
Warnings and stop conditions
- Criticaleditorial warning
If you smell gas, do not reset: do not touch switches or light flames, open windows, close the gas tap if it is within reach, leave and call your gas distributor's emergency number from outside. Cointra says to switch the boiler off when it fails and to have it repaired only by an authorised technician.
Evidence: Cointra SUPERLATIVE PLUS 24 C, instrucciones de uso, instalación y mantenimiento
- Higheditorial warning
Do not chain resets with A08: it is a temperature safety cut. If it returns, leave the boiler off and wait for the technician. Do not open the boiler or touch the sensor, pump or expansion vessel.
Evidence: Cointra SUPERLATIVE PLUS 24 C, instrucciones de uso, instalación y mantenimiento
Symptoms and causes
Probable causes · in order
- Faulty heating sensorPossible
Cointra says to check the position and operation of the heating sensor and replace it if needed. It fits if A08 appears with the system cold.
Evidence: Cointra SUPERLATIVE PLUS 24 C, instrucciones de uso, instalación y mantenimiento
- No water circulating in the systemPossible
Cointra says to check the circulator pump. It fits if the radiators stay cold while the boiler heats and then locks out.
Evidence: Cointra SUPERLATIVE PLUS 24 C, instrucciones de uso, instalación y mantenimiento
- Air in the systemPossible
Cointra says to bleed the air from the system. It fits after topping up, after building work or if you hear gurgling in pipes and radiators.
Evidence: Cointra SUPERLATIVE PLUS 24 C, instrucciones de uso, instalación y mantenimiento
Virtual technician
Does A08 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
Cointra SUPERLATIVE PLUS 24 C, instrucciones de uso, instalación y mantenimiento
Cointra · 2017 · manual
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