Correct Application of P8000/P9000 Trunking for PV DC String Installations –Avoiding Misuse and Ensuring Compliance

Cabstrut is committed to promoting safe, compliant, and durable electrical installations across all applications. We have become aware of instances where our P8000 and P9000 trunking products are being incorrectly utilised as wireways for DC photovoltaic (PV) strings on outdoor roofmounted systems. While we appreciate the trust placed in our products, this application falls outside their intended design parameters and poses significant risks to system performance, safety, and compliance with relevant standards.

Key Concerns with Misuse in PV DC Applications

The P8000 (76 mm x 76 mm) and P9000 (127 mm x 76 mm) trunking series are engineered as solid, pre-galvanized mild steel (Z275 coating) wiring ducts for general indoor cable reticulation and protection in low-heat, protected environments (e.g., suspended ceilings, walls, or floors). They are not suitable for outdoor, high-temperature DC PV string routing due to the following issues:

• Heat Buildup: The enclosed design restricts natural ventilation, leading to excessive temperatures (often exceeding 60°C in direct sunlight) that accelerate cable insulation degradation. This increases the risk of arcing, short circuits, and fire hazards under DC loads.

• Water Ingress: Roof exposure to rain, condensation, and humidity can pool within the trunking, compromising the cable sheathing and promoting corrosion of the galvanizing layer.

• Unauthorised Modifications: Reports indicate contractors drilling holes for ventilation or drainage, such alterations also breach the galvanizing integrity, leading to premature rusting and reduced lifespan.

These factors not only endanger personnel and property but also invalidate warranties, insurance coverage, and certification for the installation. Cabstrut strongly advises against such use to prevent non-compliance and potential liability.

Recommended Resolution and Alternatives

To ensure optimal performance and adherence to best practices for outdoor PV DC strings, we recommend transitioning to ventilated cable support systems that facilitate airflow and drainage while maintaining structural integrity. Cabstrut's perforated cable tray range is specifically designed for these demanding applications: for reference, please refer to our perforated cable tray range.