Terminal blocks and external wiring of distribution cabinet

Terminal blocks are modular connection points used in distribution cabinets to organize, distribute, and safely connect electrical circuits.

Types of Terminal Blocks

Terminal blocks come in various types depending on the application and wiring method:

• Screw-type terminal blocks: Require tightening screws to secure wires; suitable for both solid and stranded conductors and provide reliable connections in high-vibration environments .
• Push-in terminal blocks: Allow tool-free insertion of solid or ferruled wires, speeding up installation and reducing labor .
• Barrier and distribution blocks (FIX blocks): Used for neutral, protective, or potential distribution, enabling space-saving and clear wiring .
• DIN rail-mounted modular blocks: Standardized for easy installation and expansion, often compatible with accessories like labeling markers and protective covers .

Wiring Techniques

Proper wiring ensures safety, reliability, and compliance with standards:

1. Preparation: Strip insulation from wires (typically 6–10 mm depending on block type) and, for stranded wires, use ferrules to prevent fraying .
2. Insertion: Insert the wire into the terminal opening; for screw terminals, tighten to the recommended torque using a torque screwdriver . Push-in terminals allow direct insertion without tools .
3. Verification: Gently tug the wire to ensure a firm connection. Avoid overfilling terminals to prevent arcing or connection failure .
4. Labeling and organization: Use modular accessories, markers, or color-coded blocks to maintain clarity in complex distribution cabinets .

External Wiring Considerations

• Cross-section compatibility: Terminal blocks support a range of wire sizes; some systems handle up to 70 mm² for main distribution or sub-distribution wiring .
• Neutral and protective conductor distribution: Use dedicated distribution blocks (FIX blocks) for space-efficient and safe routing .
• Aluminum and copper conductors: Certain terminal blocks are designed to accommodate both, with flexible connection areas .
• KNX and automation wiring: Specialized terminal blocks allow clear and compact connections for building automation systems .

Safety and Best Practices

• Always power off circuits before wiring or removing wires .
• Ensure finger-safe covers or profiles are installed to prevent accidental contact with live parts .
• Use standardized modular systems to simplify maintenance, future expansion, and compliance with electrical codes .
• Consider thermal and magnetic protection for distribution blocks handling high currents or sensitive circuits .

By selecting the appropriate terminal block type, following proper wiring procedures, and organizing external wiring efficiently, distribution cabinets can achieve safe, reliable, and maintainable electrical installations.