What Is A Solar Junction Box
What Is A Solar Junction Box

What Is A Solar Junction Box

The string box is a fundamental component of a photovoltaic system, as it guarantees the safety of the equipment. It has been something that has been talked about a lot when it comes to the photovoltaic sector. This is because it is vital that it is present to make the system work.

It is an enclosure junction box in which photovoltaic sub-arrays, photovoltaic series, or photovoltaic modules are connected in parallel and can house protection or switching devices.

Therefore, it is vital in terms of system security. Increasingly, the expansion of solar energy has integrated different environments. This system needs to be well-capable to offer the best installation and service to consumers. See more on this subject below.

What is the string box?

The solar energy system’s components are solar panels, inverters, cabling, frames, and string boxes. The latter is a protection component, so the energy production system can be isolated.

Its focus is preventing electrical accidents, such as shorts or electrical surges. This way, it works like a circuit breaker box, interrupting any sign of an electrical short when power is distributed.

Thus, the risk of accidents, such as fire inside the house or company that installed the device, is eliminated.

As its installation is also carried out on the inverter and the electrical grid protection panel, the string box protects the solar panels from damage. For those thinking about installing photovoltaic systems but still in doubt about their safety, it is clear that the string box fulfills this role.

This is because it is a vital element for consumer safety to occur. It should be installed next to the on-grid solar energy system.

String box components

The standard for low voltage electrical installations provides that all installations relating to energy must have as a basic point protection against the following factors:

Electric shock;
Protection against thermal effects and fires;
Overcurrent protection;
And surge protection and sectioning capabilities.

The same standards cover the photovoltaic panel system and must follow these same basic principles. The string box is the protection item for the DC part of the photovoltaic system. It connects the cables coming from the photovoltaic modules to the inverter. A string box has:

1. Housing: where the protection device and electrical connection are located;
2. Disconnecting device: implemented with disconnecting switch;
3. Overvoltage protection device: DPS;
4. DC cables;
5. Overcurrent protection device – fuse.
6. String box functions

Now that you know what components exist in a string box, let’s investigate how they work.


The box where everything is positioned is called the casing. Its primary function is to protect devices and their connections so the user does not receive any electrical discharge.

Its classification depends on the tolerance of dust and water ingestion. Furthermore, they can be classified as suitable for indoor environments (minimum IP2X protection) or outdoor environments (minimum IP55 protection).

The installation standard states that alternating current (AC) and direct current (DC) must not be combined within the same enclosure.

Disconnect switch

A device connects and disconnects the DC part of the photovoltaic system. It becomes safe when it does not offer a chance of electric shock to the user or cause a possible fire.

This switch has several characteristics for each operating voltage value of the switch. There is a maximum operating current.

DPS surge protection device

This is an item that reduces the effects of overvoltage in the circuit. The function of the DPS is to protect the inverter against loads arising from the DC circuit. Atmospheric discharges in the SPDA system and nearby discharges cause currents in the DC circuit to be induced.


This element is an overcurrent and current protection device that fuses a conductive element when the current exceeds its nominal value. They also have several characteristics within them that contribute to the proper functioning of the solar panel and its entire system.

Circuit breaker

This works in the way that many people already know: to stop the device from overheating so that an accident involving a short circuit cannot happen. Every string box has this system so that there can be security regarding local energy generation from a photovoltaic plate connected to the public grid.

String box installation

It is essential to highlight here the importance of having professionals so that the entire installation can be carried out properly because without these professionals, even if a security system is installed, if it is not well configured, problems may end up arising.

A team of experts who know how to carry out their work will undoubtedly know the technical terms and all the specifications necessary for the system to be installed safely.

This is because some inverters already have a string box, eliminating the need for purchasing external equipment. Furthermore, numerous details must be observed, such as the distance between the module and the inverter. Details like this only a professional can notice.


For the customer to have and rely on the best on-grid equipment safely and professionally, they must choose a company and trust to carry out this task.

That’s why we have been working to enable sustainable and economical energy generation through our customers’ photovoltaic panels. You can count on a quality service that meets all your expectations and brings savings to the location where the device was installed.

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