- Boilers
- Electric water heater
15
Ariston 15 on a Velis water heater: overheating caused by lack of water
Risk level
High
Professional inspection is recommended.
Urgency
High
Quick answer
On an Ariston Velis, Er 15 means overheating caused by lack of water on the outlet side. Check that water reaches the taps and do not run the heater empty; if the tank is full and Er 15 returns, call the technical service.
Safety first
Stop and check this first
- Do not switch the Velis on without water. Ariston asks for it to be filled with mains water and all air purged through a hot tap before power is applied.
- 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 at the hot taps
- Reset with the ON/OFF button
- Sensor, board and element check
Leave these tasks to a qualified professional
- Do not attempt this professional task: Measurement after a lack of water alarm
- Do not attempt this professional task: Heating test with the tank full
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.
Measurement after a lack of water alarm
What they doThe technician measures the element and the sensors with the heater disconnected and checks that the tank is full and purged.
They must show youthe measured values against Ariston's specification.
In writingwhether air or lack of water was found, which part was replaced and why.
Heating test with the tank full
What they doAfter the work, the heater heats with the tank full and Er 15 does not return.
They must show youthe temperature rising and the display with no code.
In writingthe date and the test 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 at the hot taps
- Who:
- you.
- How:
- open a hot tap and see whether water flows steadily or spits air; check that the main water valve and the heater's valve are open.
- Result that matters:
- Ariston asks for the heater to be filled by opening the main valve and a hot tap until all the air is out, before switching it on.
- If air comes out or no water flows:
- switch the heater off with ON/OFF, open the valves and run the hot tap until water flows without air; then switch it on.
- If water flows steadily and Er 15 remains after the reset:
- the tank is full; move on to the technical service.
- Evidence to keep:
- a note of any water cut and how long the tap ran.
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 15 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 15 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
Sensor, board and element check
- Who:
- a qualified Ariston service technician.
- How:
- with the heater disconnected from the mains, measures the sensor bars and the element, and checks the board.
- Result that matters:
- whether any part measures out of Ariston's specification with the tank full.
- If the element measures out of specification:
- dry heating damage is confirmed.
- If everything measures correctly:
- sensors and board are checked as the cause of a false alarm.
- Evidence to keep:
- a job sheet with the measured values.
Measuring and removing parts requires disconnecting the mains and, for the element, draining the tank. 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
- Ariston Velis 15
- Er 15
- Velis error 15
What it means
Ariston defines code 15 as overheating caused by lack of water on the outlet side of the tank; 25 is the same on the inlet side. It is the protection that cuts out when the element heats without water around it. Ariston asks for the heater to be filled with mains water, opening a hot tap until all the air is out, before switching it on. If the tank is full and the code returns, the code does not distinguish a sensor, the board or a damaged element: the technician separates them by measuring.
Warnings and stop conditions
- Highsource verified
Do not switch the Velis on without water. Ariston asks for it to be filled with mains water and all air purged through a hot tap before power is applied.
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
- Tank empty or holding airCommon
This is the condition Ariston describes. It happens after a water cut, a drain-down or an installation where the air was not purged.
Evidence: Ariston Velis, instrucciones para la instalación, el uso y el mantenimiento de calentadores eléctricos
- Sensor or board reading overheating with the tank fullPossible
If water arrives normally and the code returns after the reset, suspicion moves to the sensor bars or the board, which the technician measures.
Evidence: Ariston Velis, instrucciones para la instalación, el uso y el mantenimiento de calentadores eléctricos
- Element damaged by dry heatingPossible
An element that has run without water may be damaged; the technician measures it before deciding on a replacement.
Evidence: Ariston Velis, instrucciones para la instalación, el uso y el mantenimiento de calentadores eléctricos
Virtual technician
Does 15 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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