Advanced Wiring Techniques SS2 Solar Photovoltaic Installation & Maintenance Lesson Note

Why “Naked” Wires are Dangerous

In a basic science project, you might just tape wires to a wall. In a professional Solar System, we never leave wires “naked” (exposed).

The enemies of your cables:

1. UV Rays: The Nigerian sun is very harsh. Regular wire insulation will crack and peel off after a few months if left in the sun.
2. Physical Damage: People walking, doors closing, or children pulling on wires.
3. Rodents: Rats love to chew on the “sweet” plastic coating of cables, which causes short circuits and fires.

The Solution: We use Containment. This is the art of hiding wires inside protective “bones” called conduits and trunking.

Conduits – The Protective Pipes

Conduits are tubes (pipes) that we run cables through. For solar, we usually use two types:

• PVC Conduits: These are plastic pipes. They are great for inside walls or underground because they don’t rust.
• Flexible Conduits (Gooseneck): These are bendy pipes. We use these when we need to connect a solar panel to a junction box because they can handle the curves.

Best Practice:

• Don’t Overstuff: Only fill a pipe up to 40%. Wires need “breathing room” so they don’t get too hot.
• Use Saddles: Use clips (saddles) every 1 meter to keep the pipe straight and firm on the wall.

Trunking – The Square Path

Trunking is usually square or rectangular and has a “lid” that snaps on. You see this often in offices or where many wires are running together.

When to use Trunking:

• Inside the Inverter Room: Since you have many wires coming from the batteries and panels, a large trunking keeps them organized and neat.
• Surface Mounting: If you cannot dig into the wall (chasing), you use neat white trunking on the surface.

Pro-Tip: Always use a “Spirit Level” when installing trunking. There is nothing that looks more “quack” than a trunking that is slanted or crooked on a wall!

Protecting the “DC” Side (Solar Cables)

Solar wiring is different because it sits on the roof in the rain and sun.

1. UV-Rated Cables: You must use special “Solar DC Cables.” These are usually black with thick insulation.
2. Corrugated UV Conduits: If you must run wires across the roof tiles, put them inside black corrugated pipes. The black color helps resist sun damage better than white pipes.
3. Glands: When a wire enters a junction box, use a “Cable Gland.” It acts like a rubber seal that stops rain from entering the box and fries your connections.

Professional Finishing & Safety

A great solar installer is known by how “clean” their wiring looks.

• Labeling: Use a marker or a sticker to label your pipes. For example: “DC FROM PANELS” or “AC TO LOAD.” This helps the next person who tries to fix the system.
• Bending: When turning a corner with a pipe, don’t make it a sharp 90-degree “elbow” if you can avoid it. Use a “Bend” so the wires can slide through easily without getting stuck.
• Drip Loops: When bringing a wire from the roof into the house, always make a small “U” shape before it enters the wall. This way, rainwater will drip off the bottom of the “U” instead of running straight into the house!

Summary Checklist:

• Is the pipe straight?
• Are the cables loose inside (not cramped)?
• Are the outdoor connections waterproof with glands?
• Is everything labeled clearly?