Why equipotential bonding is mandatory for PV systems
Equipotential bonding is one of the safety-relevant measures for any photovoltaic system. It protects people and buildings from dangerous contact voltages and safely dissipates lightning currents. For solar installers, correct execution is not optional, but normatively required.
Normative Basis
The relevant standards for equipotential bonding in PV systems include:
- DIN VDE 0100-712: Erection of low-voltage installations – Photovoltaic (PV) power supply systems
- DIN EN 62305 (VDE 0185-305): Lightning protection
- DIN VDE 0100-540: Earthing arrangements and protective conductors
Essentially, these standards require that all conductive parts of the PV system – module frames, mounting structure, and, if applicable, inverter housings – be included in the equipotential bonding.
Routing the earthing cable from the roof into the building
A frequently underestimated challenge: The earthing cable (PE) must be routed from the roof to the equipotential bonding bar in the building. The same requirements for roof watertightness apply as for DC cables.
Common errors when routing the earthing cable
- Earthing cable is temporarily squeezed next to the DC cables through an opening that is too small
- Separate drilling without sealing is used as a makeshift solution
- Earthing cable is routed down the outside of the building instead of through the roof penetration
All these solutions endanger the roof integrity or do not comply with recognized technical standards.
The clean solution: Roof penetration with PE channel
NEXCAPE offers all roof penetrations in a PE variant. This includes a separate passage for the earthing cable in addition to the PV cable channels. Available configurations:
- 2 PV+PE – 2 solar cables plus earthing
- 4 PV+PE – 4 solar cables plus earthing
- 6 PV+PE – 6 solar cables plus earthing
The material TPU (Thermoplastic Polyurethane) is non-conductive and ensures safe insulation between the cables. The tool-free installation also applies to the PE variants.
Cross-sections for equipotential bonding
| Application | Minimum cross-section |
| Equipotential bonding module frame | 6 mm² Cu |
| Main equipotential bonding | 6 mm² Cu (min.) |
| External lightning protection (if present) | 16 mm² Cu |
The PE channels of NEXCAPE penetrations are designed for common earthing cable diameters.
Practical tip: Plan for the PE variant from the start
Even if external lightning protection is not always present during initial installation: The PE variant costs only minimally more and offers the possibility of retrofitting equipotential bonding at any time. All variants are available in lengths of 105 mm, 125 mm, and 150 mm.
Order roof penetrations with integrated PE channel: Roof penetrations for solar cables (105/125/150 mm)
