Surge protection for PV rooftop systems Find out about the ideal surge protection for your application.

In order that planned amortization times are not exceeded, long downtimes and high repair costs should be avoided. However, the effects of lightning strikes and surge voltages can cause considerable damage to the system. A surge protection concept is therefore of paramount importance for the trouble-free operation of PV rooftop systems. The concept should include the protection of the inverter, the PV panels, and, in PV rooftop systems with an external lightning protection system, the building itself.

Standards are an effective tool for ensuring quality, efficiency, and safety. For PV rooftop systems, the focus on two standards:

1. HD-60364-7-712 for planning and installing PV systems
2. EN 62305-3 Supplement 5 for the selection and installation of lightning and surge protection

What requirements must surge voltage concepts for rooftop systems meet? The following dimensioning in accordance with EN 62305-3 Supplement 5 should be of aid:

In response to these challenges, we provide, as part of our preassembled system solutions, reliable string combiner boxes that protect the inverters in rooftop PV systems directly downstream of the DC voltage inputs. As a result, surge voltage couplings are discharged directly to the ground potential.

There is no general regulation for so-called fire department switch disconnectors in rooftop PV systems, but fire protection organizations and insurers are increasingly recommending their use.
The main objective is to “automatically” switch off the PV strings as close to the PV panels as possible in the event of an emergency. This minimizes the risks for the emergency services. Safe firefighting is ensured.

Regardless of whether the building is equipped with a photovoltaic system or not, a voltage-free state must be ensured before any extinguishing work can be started in the affected area. This can be ensured, for example, by actuating the main switch or by pulling fuses. This approach also interrupts the power supply of the motorized switch disconnectors in the string combiner box, which “automatically” de-energizes the DC cables in the building. Another advantage is the motorized reactivation of the switch disconnector. Intentional, unintentional, or mains failure-related shutdowns do not lead to expensive service actions, because the switch disconnectors are reactivated via motor when reset.

Discover many more exciting aids in the field of surge protection for PV systems and the use of string combiner boxes in our comprehensive FAQs section. You will find detailed answers and helpful information to help you plan and implement your projects here.

A DC switch disconnector is mandatory in every photovoltaic system, because it contributes to safety and ease of maintenance. Connections can only be disconnected safely in a load-free state. Switch disconnectors are often integrated into the inverter; however, a large part of the system remains live when long cables are used. This should be prevented during maintenance and repair work.
The solution: installing an additional DC switch disconnector closed to the PV panels. Our string combiner boxes combine this switch with surge protection and simplify the cable installation up to the inverter.

In Europe, according to HD 60364 Part 7-712, PV fuses are only required in systems with three or more parallel-connected PV strings per MPP tracker. In systems with three or more PV strings connected in parallel, residual currents can damage modules and cables. In such cases, PV fuses are crucial for avoiding personal injury and damage to buildings. Many of the latest inverters only allow the connection of up to 2 strings per MPP tracker. Information on reverse current resistance and maximum fuse protection can be found in the module manufacturer’s data sheet. Among the exceptions are PV systems with DC power optimizers or inverters with selective string shutdown, which can prevent residual currents. In this case, it is sometimes possible to do without PV fuses, although it is imperative that manufacturer’s information is always observed.

Selecting the right connection technology for string combiner boxes has a decisive influence on the efficiency, safety, durability, and ease of maintenance of the system. Two options are available:

1. Plug-in connection technology: SUNCLIX
This technology features a high level of ease of installation and ease of maintenance. The required connectors are supplied with the string combiner box, and thanks to the spring connection technology, a crimping tool is not required. The patented unlocking mechanism works without special tools and also enables compact string combiner box designs.

2. Direct connection via connection terminal blocks with Push-in Technology
In addition to plug-in solutions, the cables can also be inserted via cable glands. Connection terminal blocks with Push-in Technology enable easy and direct conductor connection.

Aluminum conductors are a popular choice in photovoltaic installations due to their low weight and cost efficiency. However, they require special connection terminal blocks and technologies for ensuring a safe and permanent connection. Because standard SCBs are not designed for the direct connection of aluminum conductors, tailor-made solutions are required. These prevent corrosion and contact problems.

Installing string combiner boxes (SCBs) in unprotected outdoor areas is sometimes unavoidable. Even though SCBs with a degree of protection of IP65 are dust-proof and protected against jet water, the tests in accordance with DIN EN 60529 are only comparative and do not simulate any real conditions. Weatherproof canopies are therefore essential. They protect string combiner boxes installed outdoors from becoming waterlogged, overheated due to sunlight, and condensation. They therefore significantly increase the service life and reliability of the string combiner boxes.

Due to varying location conditions, certain PV rooftop systems may need very long cables. To minimize power dissipation, it may be necessary to increase the cable cross-sections. A large number of standard SCBs can only accommodate a limited range of connection cross-sections. A selection of our versions, on the other hand, enables an extended connection cross-section to meet these requirements.

A photovoltaic system and an external lightning protection system share the roof space. The PV system and lightning protection system can be installed at the same time without any problems. When retrofitting a photovoltaic system on a roof on which a lightning protection system is already installed, several aspects must be taken into consideration. Find out more about separation distances, slopes, shading, and cable routing here.

Feel free to contact us. We will consult with you to find the ideal solution together.