- Boilers
- Electric water heater
051
Ariston 051 on a Nuos Plus heat pump water heater: high pressure in the heat pump
Risk level
Medium
Proceed carefully and stop if the check is unclear.
Urgency
Medium
Quick answer
On an Ariston Nuos Plus, 051 means high pressure in the heat pump circuit: the heat pump stops and the electric element keeps heating. Photograph the code and ask the technical service to check the pressure switch and the gas charge.
Safety first
Stop and check this first
- The Nuos Plus holds 0.15 kg of R290 (propane) refrigerant, which is flammable and odourless. Ariston forbids repairing the refrigerant circuit at the installation site and reserves recharging for licensed refrigeration technicians. Keep flames and sparking devices away from the heater.
- Ariston reserves maintenance and repairs for authorised personnel with suitable equipment. Do not open the covers: inside there is mains voltage and the refrigerant circuit.
Safe checks you can perform
- Which heating group still works
- Free air around the heater
- Pressure switch and gas charge
Leave these tasks to a qualified professional
- Do not attempt this professional task: Pressure switch and charge 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.
Pressure switch and charge check
What they doThe technician checks the pressure switch wiring and the amount of gas, in the order Ariston gives.
They must show youthe condition of the wiring and the charge check.
In writingwhat was found and, if the circuit was opened, the amount of R290 recovered and charged.
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.
Which heating group still works
- Who:
- you.
- How:
- look at the display: Ariston says that if the error is in the heat pump, the HP symbol flashes; if it is in the electric element, the element symbol flashes; if both are affected, both flash. Take a photo showing code 051.
- Result that matters:
- Ariston explains that the heater keeps supplying hot water if the error affects only one of the two heating groups.
- If only HP flashes:
- the electric element keeps heating; you will have hot water until the technician arrives.
- If the element symbol or both flash:
- you may have no hot water; book the visit as soon as possible.
- Evidence to keep:
- a photo of the display with the code and the flashing symbols.
Evidence: Ariston Nuos Plus S2 Wi-Fi, calentador de agua con bomba de calor: instrucciones para la instalación, el uso y el mantenimiento
Free air around the heater
- Who:
- you.
- How:
- check without opening anything that the top air openings and any ducts are clear and properly connected.
- Result that matters:
- that air circulates as the manual describes; Ariston warns that unsuitable ducting penalises performance.
- If something blocks the air:
- remove it, note the date and watch whether 051 returns.
- If everything is clear:
- leave the heater on the electric element and book the visit.
- Evidence to keep:
- photos of the air openings and the code.
Evidence: Ariston Nuos Plus S2 Wi-Fi, calentador de agua con bomba de calor: instrucciones para la instalación, el uso y el mantenimiento
Pressure switch and gas charge
- Who:
- an Ariston service refrigeration technician licensed for R290.
- How:
- checks the pressure switch wiring and, if it is fine, checks the gas charge with suitable equipment.
- Result that matters:
- whether the alert comes from the wiring or from real circuit pressure.
- If the wiring is damaged or loose:
- correcting it confirms the cause if 051 does not return.
- If the wiring is fine:
- the gas charge becomes the main suspect.
- Evidence to keep:
- a report of what was checked and, if the charge was touched, the amount of R290.
Flammable refrigerant and mains voltage: licensed refrigeration technicians only.
Evidence: Ariston Nuos Plus S2 Wi-Fi, calentador de agua con bomba de calor: instrucciones para la instalación, el uso y el 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
- Ariston
- Product type
- Electric water heater
Known code variants
- 51
- Ariston error 051
- Ariston Nuos error 051
- Error 051 Ariston
- Nuos 051
What it means
Ariston links 051 to high pressure on the Nuos Plus S2 Wi-Fi: the heat pump goes OFF and the electric element stays ON. The actions it gives are for the technician: check the pressure switch wiring and check the amount of gas. The pressure switch watches the pressure of the R290 refrigerant circuit and cuts out if it is exceeded. The code does not distinguish real high pressure from a pressure switch or wiring giving a false signal.
Warnings and stop conditions
- Criticalsource verified
The Nuos Plus holds 0.15 kg of R290 (propane) refrigerant, which is flammable and odourless. Ariston forbids repairing the refrigerant circuit at the installation site and reserves recharging for licensed refrigeration technicians. Keep flames and sparking devices away from the heater.
Evidence: Ariston Nuos Plus S2 Wi-Fi, calentador de agua con bomba de calor: instrucciones para la instalación, el uso y el mantenimiento
- Highsource verified
Ariston reserves maintenance and repairs for authorised personnel with suitable equipment. Do not open the covers: inside there is mains voltage and the refrigerant circuit.
Evidence: Ariston Nuos Plus S2 Wi-Fi, calentador de agua con bomba de calor: instrucciones para la instalación, el uso y el mantenimiento
Symptoms and causes
Probable causes · in order
- Pressure switch wiringPossible
Ariston has it checked first. A loose or damaged wire gives the same alert without high pressure.
Evidence: Ariston Nuos Plus S2 Wi-Fi, calentador de agua con bomba de calor: instrucciones para la instalación, el uso y el mantenimiento
- Wrong amount of gasPossible
This is Ariston's second check. Adjusting the R290 charge requires a licensed refrigeration technician with suitable equipment.
Evidence: Ariston Nuos Plus S2 Wi-Fi, calentador de agua con bomba de calor: instrucciones para la instalación, el uso y el mantenimiento
Virtual technician
Does 051 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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