- Boilers
- Electric water heater
12
Ariston 12 on a Velis water heater: general overheating from a board fault
Risk level
High
Professional inspection is recommended.
Urgency
High
Quick answer
On an Ariston Velis, Er 12 means general excessive water temperature on the outlet side, which Ariston attributes to a circuit board fault. Take care with hot water, reset with ON/OFF and, if it returns, call the technical service.
Safety first
Stop and check this first
- The Velis leaves the factory set to 70 °C on the 30, 50 and 80 L models. Ariston warns that water above 50 °C at the tap can cause serious burns instantly and recommends a thermostatic mixing valve.
- Ariston reserves all maintenance for qualified personnel and requires the heater to be disconnected from the mains before any work. The cover, boards, probes, heating elements and anodes carry mains voltage or sit inside the tank: do not touch them yourself.
Safe checks you can perform
- Water temperature at the tap
- Reset with the ON/OFF button
- Board and sensor test
Leave these tasks to a qualified professional
- Do not attempt this professional task: Diagnosis before replacing the board
- Do not attempt this professional task: Cut-out test after the repair
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.
Diagnosis before replacing the board
What they doThe technician measures the sensors and checks the board's cut-out before proposing a replacement.
They must show youthe sensor values against Ariston's specification.
In writingwhy the sensors were ruled out and the reference of the new board.
Cut-out test after the repair
What they doAfter the repair, the heater warms to the set point and the technician checks that it stops.
They must show youthe stop temperature on the display.
In writingthe set point and the result.
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.
Water temperature at the tap
- Who:
- you.
- How:
- open the cold tap first, then the hot one slowly, without putting your hand under it; look for steam.
- Result that matters:
- whether water comes out boiling or with steam, which Ariston treats as a fault.
- If steam or boiling water comes out:
- cut the heater's power with its external switch and leave it off until the visit.
- If the water is hot without steam:
- go on to the reset.
- Evidence to keep:
- a note of what you saw and the time.
Evidence: Ariston Velis, instrucciones para la instalación, el uso y el mantenimiento de calentadores eléctricos
Reset with the ON/OFF button
- Who:
- you.
- How:
- switch the heater off with the ON/OFF button and switch it back on, as Ariston's error table says. Do not open the cover.
- Result that matters:
- whether, after the reset, the display stops showing Er and 12 and the status light stops flashing red.
- If the code clears:
- Ariston says the heater resumes normal operation; note the date in case it comes back.
- If Er 12 returns or the light stays red and flashing:
- Ariston says to contact the technical assistance centre; do not keep resetting it.
- Evidence to keep:
- a photo of the display with the code before and after the reset, with the date.
Evidence: Ariston Velis, instrucciones para la instalación, el uso y el mantenimiento de calentadores eléctricos
Board and sensor test
- Who:
- a qualified Ariston service technician.
- How:
- with the heater disconnected, measures the sensor bars; then, with suitable equipment, checks whether the board cuts the elements when the set point is reached.
- Result that matters:
- separating a sensor that reads wrongly from a board that does not cut out.
- If the sensors read correctly and the board does not cut out:
- the board is confirmed, as Ariston suggests.
- If a sensor reads out of specification:
- the board is not the first suspect.
- Evidence to keep:
- a job sheet with the measured values and the board reference if replaced.
Mains voltage work with the cover open. Technician only.
Evidence: Ariston Velis, instrucciones para la instalación, el uso y el mantenimiento de calentadores eléctricos
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
- Ariston
- Product type
- Electric water heater
Known code variants
- 12
- Ariston Velis 12
- calentador Rinnai 12
- código 12 Rinnai
- Er 12
- error 12 Rinnai
- Rinnai 12
- Rinnai 12 flame failure
- Rinnai code 12
- Rinnai code 12 tankless
- Rinnai error 12
- Velis error 12
What it means
In the Velis table, code 12 is general excessive water temperature on the outlet side and Ariston relates it to a circuit board fault; 22 is the same on the inlet side. Unlike 11, it is not detected by a single sensor. The control stops the appliance and flags it with the flashing red light. Even though Ariston points to the board, the technician should measure sensors and board before replacing it: the code alone does not prove the board is faulty.
Warnings and stop conditions
- Highsource verified
The Velis leaves the factory set to 70 °C on the 30, 50 and 80 L models. Ariston warns that water above 50 °C at the tap can cause serious burns instantly and recommends a thermostatic mixing valve.
Evidence: Ariston Velis, instrucciones para la instalación, el uso y el mantenimiento de calentadores eléctricos
- Highsource verified
Ariston reserves all maintenance for qualified personnel and requires the heater to be disconnected from the mains before any work. The cover, boards, probes, heating elements and anodes carry mains voltage or sit inside the tank: do not touch them yourself.
Evidence: Ariston Velis, instrucciones para la instalación, el uso y el mantenimiento de calentadores eléctricos
Symptoms and causes
Probable causes · in order
- Circuit board faultCommon
This is the cause Ariston writes next to code 12. It is confirmed when the sensors measure correctly and the board does not cut the heating.
Evidence: Ariston Velis, instrucciones para la instalación, el uso y el mantenimiento de calentadores eléctricos
- Temperature sensorsPossible
Ariston includes the sensor bars in the check for boiling water. A sensor that reads wrongly can lead to a mistaken board diagnosis if it is not measured first.
Evidence: Ariston Velis, instrucciones para la instalación, el uso y el mantenimiento de calentadores eléctricos
- Scale build-upPossible
Scale is on Ariston's list for boiling water and is checked with the tank drained. It matters more with hard water.
Evidence: Ariston Velis, instrucciones para la instalación, el uso y el mantenimiento de calentadores eléctricos
Virtual technician
Does 12 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
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