- Heat pumps
- Air-to-water heat pump
2P2
Ariston 2P2 on Nimbus heat pump: incomplete disinfection
Risk level
Medium
Proceed carefully and stop if the check is unclear.
Urgency
Medium
Quick answer
On Ariston Nimbus heat pumps with the SENSYS HD interface, code 2P2 means the thermal disinfection cycle was not completed because the sterilisation temperature was not reached within 6 hours. Avoid drawing hot water during the scheduled cycle and have the electric heater checked if 2P2 repeats.
Safety first
Stop and check this first
- When the anti-legionella function runs, the domestic hot water cylinder is heated to and held at 60 °C for one hour; take care when opening hot taps to avoid scalding.
- Never open the hydraulic module or cylinder electrical enclosures or bypass any immersion heater safety thermostat; all electrical and heating element checks are strictly for qualified professionals.
Safe checks you can perform
- Check the scheduled anti-legionella start time on the SENSYS HD controller
- Avoid drawing domestic hot water during the next day's automatic retry
- Review the active hot water settings on the SENSYS HD user menu
Leave these tasks to a qualified professional
- Do not attempt this professional task: Professional check of electric heating element activation (including manual test 1.11.6)
- Do not attempt this professional task: Installer verification of backup electric heating parameters (1.4.1, 1.4.4 and 1.9.6)
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.
Professional check of electric heating element activation (including manual test 1.11.6)
What they doFollowing Ariston's resolution table for code 2P2, the technician must check that the electric heating element switches on properly (using manual test parameter 1.11.6 for a cylinder immersion element where fitted, and checking its power supply and safety thermostats).
They must show youthe live activation test of the backup electric heating element and temperature rise in the DHW cylinder.
In writingthe service report confirming the electrical check of the heating element and successful completion of the thermal disinfection cycle.
Installer verification of backup electric heating parameters (1.4.1, 1.4.4 and 1.9.6)
What they doAn authorised installer or service technician should check technical parameters 1.4.0 and 1.4.1 (active electric heater stages in DHW mode), 1.4.4 (electric immersion element in the DHW cylinder) and 1.9.6/1.9.7 to ensure backup heating is enabled for thermal sterilisation.
They must show youthe installer parameter settings for 1.4.1, 1.4.4 and 1.9.6 on the system interface.
In writingthe recorded parameter values and confirmation of how backup electric heating is configured for anti-legionella cycles.
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.
Check the scheduled anti-legionella start time on the SENSYS HD controller
- Who:
- you.
- How:
- open the user menu on the SENSYS HD interface, go to Hot water settings (Ajustes agua caliente) and select Anti-legionella function (Función antilegionela, section 3.6.1) to check the frequency (24 hours to 30 days) and the scheduled start time (Inicio ciclo antilegionela [hh:mm], default 01:00).
- Result that matters:
- identifying the exact time window when the system attempts to heat the DHW cylinder to 60 °C.
- If the start time overlaps with household hot water use:
- adjust the start time to an overnight hour when no taps are opened.
- If the start time is already set to a quiet overnight hour:
- monitor the automatic retry on the following day.
- Evidence to keep:
- photo of the Anti-legionella function screen on the SENSYS HD interface showing the frequency and start time.
Evidence: Ariston NIMBUS POCKET M NET R32, instrucciones técnicas de instalación y mantenimiento · Ariston NIMBUS S NET, manual de uso para el usuario (ES/PT)
Avoid drawing domestic hot water during the next day's automatic retry
- Who:
- you.
- How:
- because the Nimbus user manual states that an incomplete thermal sterilisation cycle automatically repeats the next day at the scheduled time, avoid running hot taps or showers during that window.
- Result that matters:
- allowing the storage cylinder to reach and hold 60 °C within the 6-hour limit without cold mains water entering.
- If the cycle completes the next day and 2P2 does not return:
- hot water draw-offs had interrupted the previous cycle.
- If code 2P2 reappears on SENSYS HD even with zero hot water use:
- have your installer check the backup electric heating element.
- Evidence to keep:
- note of whether code 2P2 reappeared after an uninterrupted overnight sterilisation window.
Evidence: Ariston NIMBUS POCKET M NET R32, instrucciones técnicas de instalación y mantenimiento · Ariston NIMBUS S NET, manual de uso para el usuario (ES/PT)
Review the active hot water settings on the SENSYS HD user menu
- Who:
- you.
- How:
- in Hot water settings (Ajustes agua caliente) on the SENSYS HD screen, review the comfort temperature, comfort function mode and cylinder mode without entering password-protected installer menus.
- Result that matters:
- recording the current DHW user settings to share with your heating technician.
- If you notice a recently changed DHW schedule or mode:
- note it down for your installer.
- If all user settings look normal and 2P2 persists:
- book a technician to inspect the electric backup heating stages.
- Evidence to keep:
- photo of the Hot water settings menu on the SENSYS HD controller.
Evidence: Ariston NIMBUS POCKET M NET R32, instrucciones técnicas de instalación y mantenimiento · Ariston NIMBUS S NET, manual de uso para el usuario (ES/PT)
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
- Heat pumps
- Brand
- Ariston
- Product type
- Air-to-water heat pump
Known code variants
- 2P2 thermal disinfection not completed
- aerotermia Ariston 2P2
- Ariston 2P2
- Ariston error 2P2
- Ariston heat pump 2P2
- Ariston Nimbus 2P2
- disinfección térmica no completada 2P2
- Error 2P2 Ariston
- Nimbus 2P2
- Sensys HD 2P2
What it means
In the indoor unit error list of the official Spanish manuals for the Ariston NIMBUS POCKET M NET R32 (installation, 2022) and Ariston NIMBUS S NET (user manual, 2022), code 2P2 on the SENSYS HD interface means Thermal disinfection cycle not completed (Ciclo de disinfección térmica no completado), triggered when the sterilisation temperature (60 °C held for one hour under parameter 1.9.6) is not reached within 6 hours. The user manual notes that an uncompleted cycle repeats the next day at the scheduled time. Other Ariston heat pump families may use different settings. By itself, code 2P2 does not prove that the immersion heater or heat pump has failed.
Warnings and stop conditions
- Mediumeditorial warning
When the anti-legionella function runs, the domestic hot water cylinder is heated to and held at 60 °C for one hour; take care when opening hot taps to avoid scalding.
Evidence: Ariston NIMBUS POCKET M NET R32, instrucciones técnicas de instalación y mantenimiento · Ariston NIMBUS S NET, manual de uso para el usuario (ES/PT)
- Higheditorial warning
Never open the hydraulic module or cylinder electrical enclosures or bypass any immersion heater safety thermostat; all electrical and heating element checks are strictly for qualified professionals.
Evidence: Ariston NIMBUS POCKET M NET R32, instrucciones técnicas de instalación y mantenimiento · Ariston NIMBUS S NET, manual de uso para el usuario (ES/PT)
Symptoms and causes
Probable causes · in order
- Domestic hot water draw-offs during the 6-hour thermal sterilisation windowCommon
Ariston's resolution table lists domestic hot water draw-offs during the thermal sterilisation cycle as the primary reason the cylinder fails to reach 60 °C within 6 hours.
Evidence: Ariston NIMBUS POCKET M NET R32, instrucciones técnicas de instalación y mantenimiento · Ariston NIMBUS S NET, manual de uso para el usuario (ES/PT)
- Backup electric heating element disabled or not switching on during DHW sterilisationPossible
The technical manual notes under parameters 1.4.1 and 1.9.6 that if backup heat sources or electric heater stages are disabled (Par. 1.4.1 = 0) or absent, the anti-legionella cycle may fail to finish due to heat pump operating limits.
Evidence: Ariston NIMBUS POCKET M NET R32, instrucciones técnicas de instalación y mantenimiento · Ariston NIMBUS S NET, manual de uso para el usuario (ES/PT)
- Anti-legionella start time scheduled during peak household hot water demandLess common
The scheduled start time in parameter 1.9.7 (Inicio ciclo antilegionela, default 01:00) overlaps with household showers or off-peak tariff restrictions (Par. 1.9.3).
Evidence: Ariston NIMBUS POCKET M NET R32, instrucciones técnicas de instalación y mantenimiento · Ariston NIMBUS S NET, manual de uso para el usuario (ES/PT)
Virtual technician
Does 2P2 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
Ariston NIMBUS POCKET M NET R32, instrucciones técnicas de instalación y mantenimiento
Ariston · 2022 · manual
- 2
Ariston NIMBUS S NET, manual de uso para el usuario (ES/PT)
Ariston · 2022 · manual
Was this entry useful?