1. Why you need it
Lightning does not have to hit the panels to cause damage: even a nearby strike induces surges on the cables, which can destroy the inverter. Surge protective devices (SPDs) divert these surges to earth before they reach the equipment.
2. First question: does the house have a lightning rod?
No: bond the panel structures and frames to earth as per the manual, and fit a type 2 SPD on the panel side (DC).
Yes: go to the second question.
3. Second question: are the panels inside the protected zone?
Yes, and the safety distances from the lightning rod are respected: a type 2 SPD is enough.
No: you need a type 1 (or 1+2) SPD where the cables enter the house, and the system must be bonded to the lightning protection.
4. Always, in every case
- Choose the SPD on the panels' open-circuit voltage in the cold.
- A separate SPD on the AC side.
- + and − cables close together, no wide loops; short, straight earth wires.
- On long cables, one SPD at each end.
- Check the SPDs after storms.
If the cables between panels and inverter are short (under 10 m) and the inverter already has built-in SPDs, the external one may not be needed: the technician decides. The CEG string box comes with SPDs fitted. DC box
5. Who decides
The lightning risk assessment follows the applicable standards (IEC/EN 62305) and is done by a qualified technician. This diagram explains the choices; it does not replace that assessment.
6. The detailed wiring diagram
The block diagram helps you understand how it works. The detailed wiring diagram, with terminals and connections, is reserved for those who bought through Carmine Energia Gratis: write to Carmine with your CEG pre-order number. Wiring and testing must be done by a qualified electrician.
7. Frequently asked questions
What is the difference between type 1 and type 2 SPDs?
Type 1 is made for very high currents, such as a direct strike coming from the lightning protection system. Type 2 protects against surges induced by nearby strikes, which is the most common case.
If I have a lightning rod, are my panels already protected?
Only if they are inside the protected zone and at the right distance. Otherwise you need a type 1 (or 1+2) SPD and bonding to the lightning protection.
The inverter has built-in SPDs: is that enough?
With short cables, under 10 m, it may be. With long cables an SPD near the panels is also needed. The technician decides.
How often should SPDs be checked?
After every strong storm and during maintenance. Many SPDs have a small window that changes colour when they need replacing.
Talk to Carmine
Before choosing components and connections, let us check your system together.