Q: How can I detect if my ARISTON NUOS PRIMO water heater is scaled?

To detect if your ARISTON NUOS PRIMO thermodynamic water heater is scaled, several signs should alert you. First, observe the decrease in performance : if the water takes longer to heat or if the temperature does not rise properly, scaling reduces the system's efficiency. You may also notice unusual noises during operation, such as clicking or crackling, caused by scale deposits heating up and detaching. The soiling of the tank is a recurring problem with this model. If you notice visible limescale during draining or if the condensate drain pipe regularly gets blocked, this is a sign of internal scaling. Cloudy water or water with particles coming from the taps may also indicate circulating limescale. To regularly check the condition of the safety group installed at the cold water inlet, test it once a month . Slightly open the small drain tap: clear water should normally flow out. If you observe cloudy water, whitish particles, or a buildup of deposits, this confirms the presence of scale. This is when you need to remove the scale deposits that could block the device. In case of an E5 error on the control panel, it often indicates severe soiling of the tank. According to the manual, you should then cut off the power, drain the device, remove the resistance sheath, and clean the limescale accumulated in the tank. As a preventive measure, check annually that the condensate drain pipe is not blocked and maintain the cleanliness of the air intake and outlet grilles . If the water in your area is very hard (beyond 25°F), installing a water softener is recommended to reduce scaling. In case of doubt, a professional descaling will help preserve the lifespan and performance of your device.

Q: What does the error code "HP under temperature" mean on an Ariston NUOS water heater and how can it be resolved?

The error code "HP under temperature" displayed on an Ariston NUOS water heater generally indicates that the water temperature is below the expected threshold, which may signal a heating problem or a malfunction of the system. Possible causes Temperature set too low on the thermostat. Electrical supply issue affecting the heating element. Failure or malfunction of the heating element or thermostat. Connection error or internal technical problem. Steps to resolve the issue Check the set temperature: Ensure that the thermostat is set to an adequate temperature, typically between 50°C and 60°C. Check the power supply: Verify that the water heater is powered, that the circuit breaker has not tripped, and that the cables are not damaged. Inspect the connections: Ensure that all electrical connections are secure and in good condition. Allow the water heater to heat: If the water heater has just been turned on, wait a moment to allow the water to reach the desired temperature. Restart the device: Sometimes, a simple restart can reset the system and clear the error code. If after these checks the "HP under temperature" code persists, it is recommended to contact a qualified professional to diagnose and repair the water heater to avoid any risk of breakdown or safety issues.

Question 1

Where is the access panel on an Ariston NUOS water heater?

Accepted Answer

On the Ariston NUOS thermodynamic water heater, there is no traditional access panel at the base of the unit. Access to the internal components is done differently depending on the maintenance areas:

Access to the evaporator filter: The evaporator filter, a key component of the heat pump, is located at the back (rear) of the water heater. It is accessible via a special clip located at the top of the rear (see figure 17 in the manual). You can remove the filter without tools to clean it with water and neutral soap at least once a year, in order to maintain the unit's performance by removing dust and blockages.

Access to the condensate connections: On the side of the unit, a specially designed connection allows for the drainage of condensates with an appropriate pipe and siphon. This connection is easily accessible and should be regularly checked to ensure that the tube is not blocked.

Air grilles: At the back (upper part) of the water heater, there are two grilles: one for air intake and one for exhaust. These grilles should be kept in place during normal operation and checked regularly to ensure sufficient airflow. They can be cleaned without disassembly.

Important: before any maintenance handling, disconnect the unit from the electrical network for your safety. Draining operations and interventions on the refrigeration circuit must be carried out by a qualified person.

Question 2

Where can I find the figure numbers in the Ariston NUOS water heater manual?

Accepted Answer

In the Ariston NUOS water heater manual, the figure numbers are generally placed next to the illustrations or diagrams corresponding to the different steps or components described in the text. These figures help to better visualize the instructions.

To locate them:

Look in the pages where the detailed instructions are found, in small boxes or captions indicating "Figure 1", "Fig. 2", etc.
The figures may be located in the margins of the text or at the bottom of the page, accompanied by a concise description.
Sometimes, a specific section of the manual is dedicated to illustrations, often at the beginning or end of the document.

In summary, the figure numbers are integrated into the manual near the explanatory images to facilitate the understanding of the installation or usage steps of the water heater.

Question 3

How to remove and clean the filter of the Ariston NUOS water heater?

Accepted Answer

Before any intervention, turn off the power supply to your Ariston NUOS water heater and ensure that the device is unplugged. Wait a few minutes for the system to cool down slightly.

The evaporator filter of your NUOS is located at the back of the device. It can be removed using a special clip located on the back of the product (see figure 17 in the manual). Gently pull on this clip to release the filter without forcing it.

Clean the filter with warm water and mild soap. You can use a soft brush to gently remove dust or debris that has accumulated. Partial blockage of the filter causes a reduction in the performance of your water heater, which is why it is recommended to perform this cleaning at least once a year, or more frequently if you notice a drop in performance.

Once the filter is cleaned and dried, reinstall it by pushing it until you hear the clip lock back into its original position. Ensure that it is securely fastened.

After cleaning the filter, it is advisable to fill and drain the device: close the isolation valve, open a hot water tap to drain the plumbing, then reconnect the power supply and fill the tank by reopening the isolation valve.

Check for any leaks around the filter and that the device is functioning properly. If you still observe a drop in performance or unusual noises, the filter or air ducts may require more thorough cleaning. For any more complex intervention, contact a qualified technician.

Question 4

How can I detect if my ARISTON NUOS PRIMO water heater is scaled?

Accepted Answer

To detect if your ARISTON NUOS PRIMO thermodynamic water heater is scaled, several signs should alert you. First, observe the decrease in performance: if the water takes longer to heat or if the temperature does not rise properly, scaling reduces the system's efficiency. You may also notice unusual noises during operation, such as clicking or crackling, caused by scale deposits heating up and detaching.

The soiling of the tank is a recurring problem with this model. If you notice visible limescale during draining or if the condensate drain pipe regularly gets blocked, this is a sign of internal scaling. Cloudy water or water with particles coming from the taps may also indicate circulating limescale.

To regularly check the condition of the safety group installed at the cold water inlet, test it once a month. Slightly open the small drain tap: clear water should normally flow out. If you observe cloudy water, whitish particles, or a buildup of deposits, this confirms the presence of scale. This is when you need to remove the scale deposits that could block the device.

In case of an E5 error on the control panel, it often indicates severe soiling of the tank. According to the manual, you should then cut off the power, drain the device, remove the resistance sheath, and clean the limescale accumulated in the tank.

As a preventive measure, check annually that the condensate drain pipe is not blocked and maintain the cleanliness of the air intake and outlet grilles. If the water in your area is very hard (beyond 25°F), installing a water softener is recommended to reduce scaling. In case of doubt, a professional descaling will help preserve the lifespan and performance of your device.

Question 5

How to maintain an ARISTON NUOS PRIMO water heater to ensure its proper functioning and longevity?

Accepted Answer

Regular maintenance of your ARISTON NUOS PRIMO water heater is essential to ensure its efficiency, safety, and prolong its lifespan. Here are the main steps to follow:

1. Regular visual inspection

Periodically check the appliance for any water leaks, corrosion, or visible damage. This allows for quick intervention in case of a problem.

2. Descaling

In areas where the water is hard, limescale can accumulate inside the tank. It is recommended to descale every 1 to 2 years to prevent clogging and optimize performance.

3. Temperature control

Set the water temperature around 60°C. This setting limits the risk of burns, reduces energy consumption, and prevents the development of bacteria.

4. Safety valve check

Test the safety valve at least once a year. This operation involves slightly opening the valve to check that it properly releases pressure.

5. Filter cleaning

If your model is equipped with a filter, clean it regularly to ensure good water circulation and avoid blockages.

6. Insulation check

Check the condition of the water heater's insulation and pipes to minimize heat loss and improve energy efficiency.

7. Professional maintenance

Have a complete maintenance performed by a professional every 2 to 3 years. A technician can carry out a thorough diagnosis, clean internal components, and ensure overall proper functioning.

By following these tips, you will help keep your ARISTON NUOS PRIMO water heater in perfect working condition and avoid premature breakdowns.

Question 6

What is the required power supply voltage for the ARISTON NUOS PRIMO water heater?

Accepted Answer

The ARISTON NUOS PRIMO water heater requires a power supply of 230 volts to operate correctly. This voltage is standard for domestic installations in many countries.

To ensure safe and optimal operation, it is important that your electrical installation complies with local regulations, particularly regarding differential circuit breaker protection and grounding.

If you are considering the installation or maintenance of your water heater, make sure that the dedicated electrical circuit is suitable for the device's power and that the connections are made by a qualified professional.

Question 7

What does the error code "HP under temperature" mean on an Ariston NUOS water heater and how can it be resolved?

Accepted Answer

The error code "HP under temperature" displayed on an Ariston NUOS water heater generally indicates that the water temperature is below the expected threshold, which may signal a heating problem or a malfunction of the system.

Possible causes

Temperature set too low on the thermostat.
Electrical supply issue affecting the heating element.
Failure or malfunction of the heating element or thermostat.
Connection error or internal technical problem.

Steps to resolve the issue

Check the set temperature: Ensure that the thermostat is set to an adequate temperature, typically between 50°C and 60°C.
Check the power supply: Verify that the water heater is powered, that the circuit breaker has not tripped, and that the cables are not damaged.
Inspect the connections: Ensure that all electrical connections are secure and in good condition.
Allow the water heater to heat: If the water heater has just been turned on, wait a moment to allow the water to reach the desired temperature.
Restart the device: Sometimes, a simple restart can reset the system and clear the error code.

If after these checks the "HP under temperature" code persists, it is recommended to contact a qualified professional to diagnose and repair the water heater to avoid any risk of breakdown or safety issues.

Question 8

What does the error code H4 mean on an Ariston NUOS PRIMO water heater and how can it be resolved?

Accepted Answer

The error code H4 on an Ariston NUOS PRIMO water heater means “Evaporator obstructed”. This evaporator is part of the heat pump, which is the system that efficiently heats the water. When this code appears, the display shows the “HP” symbol flashing to indicate a heat pump anomaly.

The obstruction of the evaporator generally occurs due to a lack of maintenance of the condensate drainage tube. As a thermodynamic water heater, the NUOS PRIMO produces condensate during its operation. This condensate must drain properly through a specialized tube located at the back of the unit. If this tube becomes blocked by limescale deposits, impurities, or calcium, the evaporator can no longer function properly.

Solutions to resolve the H4 code: The first action is to check the condensate drainage tube located at the back of the unit. Ensure that it is not blocked or crushed. If you notice limescale or a blockage, gently clean the tube or descale it with an appropriate solution. Also, ensure that this tube is properly connected to a drainage siphon and that it is sloped continuously downward to allow for the natural drainage of the condensate.

Next, check the safety group of the unit, whose operation is closely linked to that of the evaporator. Test it by pressing the lever designed for this purpose once a month to ensure it is not stuck, and clean any limescale deposits that may be present.

If the condensate drainage tube is clear and the safety group is functioning properly, you can restart the unit by turning it off for a few minutes and then turning it back on to see if the H4 code disappears. Make sure to turn off the power by cutting the electricity from the dedicated circuit breaker beforehand.

If the H4 code persists after these interventions, or if you notice a leak at the condensate drainage tube or the safety group, contact a qualified professional. The evaporator or the condensation system of the heat pump may require thorough cleaning or replacement of internal components, operations that must be carried out by an authorized Ariston technician.

Question 9

What should I do if the ARISTON NUOS PRIMO water heater shows no error lights but does not heat the water?

Accepted Answer

If your NUOS PRIMO thermodynamic water heater shows no error code on the screen but you have no hot water, start by checking the following points in order:

1. Check the temperature setting - This is the most common cause. Use the adjustment knob to check that the set temperature is correctly configured. The temperature ranges in heat pump mode are from 50 to 55°C by default (40 to 55°C after installer menu modification). In resistance mode, the maximum temperature is 65°C by default (75°C after modification). If the setpoint is too low, increase it by turning the knob.

2. Check the power supply - Ensure that the device is actually powered. Check for current at the circuit breaker switch. Turn the water heater off and back on by pressing the ON/OFF button: a delay of 5 minutes is normal on the first start of the heat pump. Also, check the cable connections at the back of the device.

3. Clean the evaporator - A dirty evaporator significantly reduces the performance of the heat pump. Remove the screws from the front and top cover, then gently clean the fins with a brush. Also, check that the air intake and exhaust grilles are not blocked. The condensate drain pipe should not be blocked.

4. Check the operating mode and the Time W setting - In GREEN mode, only the heat pump operates (recommended above 0°C). In AUTO mode, the heat pump is assisted by the resistance if necessary to reach the temperature in a maximum of 8 hours (duration adjustable). In BOOST mode, rapid heating with both systems. If you have a bi-hourly rate, check that the "Time W" setting is not too low and that the day/night contactor is functioning properly. Wait at least 8 days after each modification of the Time W for the device to adapt.

5. Insufficient outdoor temperature - The heat pump operates with outdoor air temperatures from 7 to 35°C. Outside this range, only the resistance heats. If the outdoor temperature is too low or too high, the device may not heat properly with the heat pump alone.

6. Internal clogging issues - A high level of limescale or deposits in the tank reduces performance. If you suspect a blockage, troubleshooting the hydraulic circuit (leaks, blockages) or internal cleaning requires qualified intervention.

If after these checks the water remains cold or insufficiently hot, check for any error codes on the screen (refer to the error table in the booklet). If no identified cause explains the problem, contact customer service as a repair by a qualified professional will be necessary.

Question 10

What is the function of the temperature probe on the Ariston NUOS PRIMO water heater and how to check its status?

Accepted Answer

The Ariston NUOS PRIMO water heater is equipped with NTC type temperature probes (negative temperature coefficient thermistors) that play a crucial role in the automatic regulation of the device. These sensors continuously measure the water temperature at different points in the tank and circuit to optimize the operation of the heat pump and the electric resistance.

The NUOS PRIMO has several distinct probes: one temperature probe at the bottom of the tank (W1), one at the top of the tank (W2), one on the hot water outlet pipe (W3), one on the evaporator, and one on the air inlet. These probes constantly communicate with the control electronics to adjust the heating power, select between the heat pump and the resistance, and activate safety functions such as anti-legionella protection or automatic defrosting.

To check the status of the probes, start by consulting the information menu of your water heater: press and hold the central knob for 5 seconds, then scroll to parameters L1 to L5 which display the temperatures measured by each probe. The values should be consistent with the actual water temperature. If you observe abnormal discrepancies or values that do not change at all, this may indicate a malfunction.

A probe failure is generally indicated by specific error codes displayed on the screen: E4 indicates a problem with the resistance probes, E5 signals an excessive temperature difference between the probes, H6 concerns the air probe, H7 the evaporator probe, and H8 the hot water pipe probe. Each of these codes triggers the shutdown of the concerned function but the device continues to operate partially with the other heating system.

If you notice an error code related to the probes, start by checking the electrical connections of the sensors (the device must be turned off before any intervention). Ensure that the cables are not damaged, corroded, or poorly connected to the electronic board. A simple reconnection is sometimes enough to resolve the issue. If the error persists or if a probe never registers any temperature variation, the probe needs to be replaced and should be entrusted to a qualified professional, who will use an original Ariston spare part.

In normal mode, the absence of an error code means that all probes are functioning correctly. Regular maintenance of the evaporator (at least once a year) helps prevent faults, as dirt can distort readings and generate errors. To keep your probes in good condition, ensure that the system is powered stably and avoid electrical surges.

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