Questions and Answers

the most frequent questions


The system can handle any type of generator provided that it generates a voltage of 230 V +/- 10% and a frequency of 50.0 Hz. The connection is made at a frequency between 49.0 and 51.0 Hz, the disconnection instead takes place below 46.5 and 52.5 Hz.

For the off grid system, the MPPT controller accepts a voltage range between 90 and 160 V (recommended at 120 V in order to obtain the best performance of the MPPT). The maximum power output per MPPT shall not exceed 3,3kw. For the on grid instead the MPPT controller accepts a voltage range between 200 and 600 V recommended between 300 and 400 V.

Off grid: the "string cards" are responsible for making the parallel between the photovoltaic strings, usually composed of 3 or 4 panels connected in series. Each string must have a voltage between 90 - 160 V (recommended 120 V in order to obtain the best performance of the MPPT) and a current not exceeding 10 A (12 with appropriate fuses). The strings must be inserted through the dedicated holes in the ZHERO casing and screwed to the terminal board, paying attention to the connection order.

On grid: the "string cards" are responsible for making the parallel between the photovoltaic strings, generally composed of 7 to 15 panels connected in series. Each string must have a voltage between 200 and 600V (recommended between 300 - 400 V in order to obtain the best performance of the MPPT) and a current not exceeding 10 A (12 with appropriate fuses). Strings must be inserted via dedicated connectors within ZHERO.

Zhero was thinked to use on single-phase residential systems. ZHERO can be installed in a three-phase line along one of the 3 phases as long as it only supplies single-phase users. This is due to the fact that in case of interruption of the phase passing through ZHERO, the other phases of the system would not be interrupted, causing possible breakages of the connected devices.

No. The system automatically bypasses under abnormal conditions. Even if this does not happen, the user can manually rotate the main disconnector in position 2, an operation that allows manual bypass of the system, restoring the power supply, until the installer intervention.

Yes, it is possible to use ZHERO as a back-up unit, which can be recharged either by photovoltaic system or by electricity grid, or by generator. It is not certified as UPS.

There are several factors that influence the sizing of a photovoltaic system with accumulation such as: the place in installation, sun exposure, the maximum installed power, the type of use of the system etc...

The ambient temperature range of ZHERO is from -10 to +40 °C

It is sufficient to remove the protective foot socket and use a normal pallet truck. In case of need, you can decompose it into 3 parts: battery body, main body and hat. The central body can be further freed from the side protections.

Maintenance shall be carried out by authorised personnel. The device only requires a good cleaning of the air filters along the front pockets and the upper fan, so that the accumulation of dust does not cause a difficult flow of air. It is a good norm on these occasions also to ask the maintainer to verify the correct tightening of the various AC and DC terminals of the machine.

It is advisable to install ZHERO in a discreetly ventilated technical environment even if in principle there are no special requirements. In any case it is good to avoid excessively hot places, avoid exposing ZHERO to direct sunlight and avoid places where flooding is frequent. It is also necessary to check that the floor supports 300 kg/m2.

The degree of protection of ZHERO is IP20.

Yes, but currently the communication protocol is not implemented with electric cars. You can still connect the 220V power supply to ZHERO as you do with a normal electrical outlet.

Indicativamente la percentuale di energia auto consumata da un utente con un contratto di scambio sul posto si aggira tra il 20 e il 30%. Con ZHERO, confrontando diversi sistemi installati sul campo, si aggira tra il 65 e il 75%, con punte fino al 90%. L’aleatorietà dei numeri è condizionata all’utilizzo intelligente dell’energia.

Yes. The machine is designed for this function. The preferred load can be programmed according to the user’s needs. Currently it is a clean contact that is closed.

Yes. The CPU card is already set up for connection through a clean contact that can be carried out by ZHERO.

Yes, the exchange system is called Owner Grid.

Absolutely not. Every intervention must be approved by UNE and executed exclusively by authorized personnel.

No, the whole system is grounded and completely secure. In the event of loss of insulation, the system shall ensure its own security.

Yes, golfers placed on the ZHERO cap can be used precisely for this purpose. In addition, the lower base of the system has holes that allow it to be fixed to the floor to ensure further stability.
Yes, ZHERO is equipped with special earth unloaders (OPZ). In addition, within the system, there are numerous fuses that make it difficult to further propagate the discharge.
Yes, however, you must follow the requirements concerning the container box and the connection methods indicated by UNE in the installation manual.

It depends heavily on the type of consumer. It is possible to evaluate the consumption of the house and evaluate the necessary investment.

Depends. It is possible to maintain the photovoltaic system, but it is necessary to verify that the strings have a maximum voltage between 80 - 180 V and a current for each not exceeding 10 - 12 A. In addition, the old inverter becomes completely obsolete as everything comes and must be managed by ZHERO.

In the case of an existing dwelling there is a deduction of 50% on the total amount spent refunded in 10 years. When combined with a heat pump or thermal plant, the deduction is 65%.

It is possible with a correct sizing of the plant and a careful use of the energy produced to obtain long periods of complete autonomy from the grid. Total energy independence requires an external generator that compensates for periods of low photovoltaic production.
No, ZHERO is designed to work with its own salt batteries
In case the generator is an outdated or poor quality model and can generate an irregular frequency or out of the acceptable range, the connection is made difficult. In this case it is better to replace the old generator with a model of the latest generation.
No, golf rings are for wall mounting.
Yes, it is possible to upgrade the storage capacity by requiring immediately the preparation of the second battery or to perform the complete upgrade at a later time.
Yes, the system was also designed for this functionality, even without a generator.
ZHERO is shipped on pallets already fully assembled and ready for commissioning. In the case of special installations it is possible to ship the disassembled system.
Yes, as for a normal connection of the photovoltaic grid is required an external production meter. In case you are in an off-grid situation you will not need to.
Yes, a differential magnetothermic should be installed at the beginning of the line and it is recommended in class A, 300ma selective.
The space exists, however it is preferable to keep the disconnectors outside the machine close to the production counter.
Currently 1 but on request UNE is available for any customization.
It is possible to access the terminal blocks DC and AC through the holes to break through the box. In fact, 4 preholes have been created to be removed according to the cabling needs, to which cable glands (PG36) or sheath box fittings can be applied.
Certainly it is necessary to switch to a meter from 3 to 6 kW so that you can make the most of the functionality of the ZHERO. It is not advisable to use a power higher than your meter both in terms of electrical safety and regulation.
Yes. Input power and pick power need not be the same. It can have an input power of 6 kW for the presence of the ZHERO and a withdrawal power (contractual) of 3 kW. However, the 6 kW of power can only be used if the system has sufficient battery power and, hypothetically, only in months where there is high radiation. In winter, for example, you will often be connected to the public network for lack or low radiation so if you are used to exceed 3 kW you could have some disruptions caused by the click of the Enel counter. A user attentive to this aspect can also do it, the one a little less attentive could perceive this disservice as a malfunction of the system.
There is no obligation to switch to a three-phase supply. What matters for the relationship with the network is the output power of the inverter.


It depends. If the battery does not deliver power, self-consumption is around 100 Wh and during residential use about 50 Wh. Over 800 W supplied by the battery the PWM are switched off.
Absolutely not. The batteries are 100% safe, they resist to strong thermal changes, they do not produce harmful vapors and they even resist to immersion in salt water without causing any danger to things or people.

It is currently possible to monitor the system remotely using the web app developed by UNE at: This web app, accessible from both a fixed PC and a mobile device, allows you to view the operating status, the presence of anomalies and all the energy flows of the house. The commands from remote instead, have been implemented but are not made available to the user to avoid that a lotus improper use can cause malfunctions of ZHERO.

These are the mode of operation of the machine, depending on the type of use you intend to make (off-grid, on-grid, transfer to the network, etc.). These are set and allow the machine to adapt to the needs of the end user.
You can set up a USB output to connect and, by using the dedicated software Unesrlcomunication, you can view and download all the data of the machine in 1s steps.
The weight of the system is around 240 kg for the single-battery model, while for the double- battery model it is around 340 kg.
The inverter has a maximum power output of 6kw. In the case of a user with a lower connection contract, the power may be limited to adapt to the supply of the network.
ZHERO is guaranteed 10 years on the battery and 5 years on the inverter. It is also guaranteed for life on the risks of explosion, gas emissions and flammability.
The life expectancy of the battery, used within the ZHERO system, stands at 20 years.
Yes, ZHERO is anything but a closed system. It is possible to implement many features to best adapt it to the customer’s needs.
ZHERO and all its components ) are entirely designed, manufactured and assembled in Italy. (except the battery that is manufactured in Switzerland by an Italian company)
ZHERO firmware updates will be made remotely through internet connection without the need of external intervention.
In general, the battery shows good thermal inertia both against the cold and against the heat, thanks to its insulation and its intelligent management of the heaters. In fact, it can function correctly in an ambient temperature range from -40 to +60 =C. Since the temperature inside is almost kept constant, the temperature only affects the frequency of ignition of the internal heaters.
The battery is perfectly conserved. In fact, once turned off, it cools going to solidify the molten salts inside it and also fossilizing its state of charge; so even years later there will be no phenomena common to other batteries such as: deterioration, decline in the state of charge, memory effect etc...
The battery capacity can be 7.6 kWh, 9.6 multiplied by two of the same capacity. It is classified as C4. The DOD is up to 90%.
During normal operation it does not exceed 25 db. In the case of forced ventilation ignition, which usually occurs only during the hottest summer days, can reach 30 db.
ZHERO contains all the devices and components necessary for a system with accumulation.
The alarm is displayed via the red alarm lamp and the error code displayed on the display. The type of problem is reported by sending an email with the details of the malfunction, both to the user and the installer. They will then be able to agree on a solution.
The Owner grid is a single-phase 230 V AC power grid that can be installed between 2 or more ZHERO systems. Through this network, following particular rules, it is possible to transfer the excess of photovoltaic production to the other system or receive them if necessary. This excess energy exchange is set as a priority channel compared to the transfer to the grid to promote energy autonomy. Currently this change in Italy is only allowed provided you create a smart grid completely separated from the national network, while in some foreign countries it is already allowed.
ZHERO is about 600 cm wide, 600 cm deep and 1360 cm high.
Its main purpose is to protect the feet from accidental blows. It also reduces thermal dispersion and uniforms the aesthetics.
All technology and know-how are the property of UNE
At the first power on, with cold battery, it will take between 10 - 12 hours for a total of 3 - 4 kWh of consumption.
In case of overload it is recommended to detach the loads that caused it and press on the ZHERO AC panel. The red overload lamp and system will return regularly in operation.
Yes, it is possible up to a maximum of 18 kwp of photovoltaic.
The installations of the first systems date back to 2013.
The technology of sodium batteries exists since the 80s and it has been used mainly for telecommunications, transport, green areas etc... With ZHERO, it is also inserted in residential environments.
No, the battery is exclusively sold together with the ZHERO system.
Yes, but the installer has to.

The system is CE certified, CEI-021, residential and light industry, as well as all tests passed in tests performed by the certification body EUROFINS. You can view and download copies of the certificates directly from our website. The remaining documentation can be obtained directly from

They use MPPT technology. The controllers always look for the point of maximum efficiency to maximize the photovoltaic production.
There are no specific standards to clarify this point, because it is an extremely complex and unique system, with various operating modes. You have very high returns: over 97% efficiency, analyzing the individual components.
It depends on the mode of operation. In case of on grid mode, the excess of production is resold to the network operator. In off grid mode you have the possibility to pour this energy on a privileged line CP1, to which you can connect loads. In case of Owner grid, this energy will be exchanged with other systems that need it at that time.
The battery during the charging phase can absorb a maximum of 2.16 kW while in discharge it can yield up to 6 kW. So for dual battery systems, the maximum power they can absorb is 4.32 kW, while the output remains unchanged.
There is an app on which the basic quantities are displayed, including the state of charge of the battery, the power output, the power taken from the grid, photovoltaic production and alarms.
The charge status is calculated by the CPU by averaging the Socs of the connected batteries. This data is extracted from the batteries thanks to a constant communication between the BMS of the battery and the CPU card.
Thanks to an irradiation sensor is made the difference between the actual production generated by the MPPT and the measurement found by the sensor. In this way, the excess power to be assigned to privileged loads is calculated.
The system already has an additional module prepared on our Modbus RTU rs485 motherboard ready to communicate externally with other devices. The communication protocol with these devices is to be implemented because everyone uses a proprietary protocol.