Chafing Points: An Underestimated Fire Risk
When photovoltaic cables on the roof rub against rough surfaces, chafing points develop over time. The insulation becomes thinner until the bare conductor is exposed. With DC voltages of up to 1,000 volts, this can lead to arc faults and, in the worst case, a roof fire. For solar installers, preventing chafing points is therefore not a trivial matter, but a safety-critical obligation.
Where do chafing points occur?
Critical points are always where cables meet hard or sharp-edged materials:
- Tile edges: Especially with untreated clay tiles with a rough surface
- Sheet metal flashings: Gutters, valleys, and connection flashings often have sharp edges
- Mounting frame: Metal rails and clamps can cut into cables
- Roof penetrations: Rigid or drilled penetrations create friction points
- Cable ties: Cable ties that are pulled too tight can cut into cables due to temperature fluctuations
The Physical Hazard: Arc Fault
An arc fault occurs when a cable is damaged and current flows over a fault. The temperatures generated can reach over 3,000 °C – enough to ignite wood, insulation material, and roofing felt. While modern inverters are sometimes equipped with arc fault detection (AFCI), this does not provide complete protection.
Prevention: Avoiding Chafing Points from the Start
During cable installation
- Lay cables with sufficient distance from sharp edges
- Use protective sleeves or edge protection profiles at unavoidable contact points
- Secure cables at regular intervals with UV-resistant cable clamps
- Observe bending radii according to manufacturer's specifications – too tight radii weaken the insulation
- Avoid loose cable lengths that can flutter in the wind
During roof penetration
The risk of chafing points is particularly high at the roof penetration. Conventional solutions with drilled tiles create sharp edges directly on the cable. NEXCAPE roof penetrations made of TPU (Thermoplastic Polyurethane) eliminate this risk:
- No drilling necessary: Tool-free installation creates no sharp edges
- Flexible material: TPU yields to movement instead of abrading the cable
- Smooth cable routing: The cable channels are inherently smooth due to production
- MC4 connectors remain mounted: No unnecessary handling that stresses the cables
Regular Inspection is Mandatory
DIN VDE 0100-600 prescribes the inspection of electrical installations. For PV systems, a visual inspection of the cable routing should be carried out at least every two years. Special attention should be paid to:
- Discoloration or abrasion of the cable insulation
- Loose cable fastenings
- Changes to the roof penetration
Fire protection begins with the correct roof penetration: find suitable PV roof penetrations
