Terminal Blocks

Terminal blocks look interchangeable, but the rail, the wire range and the connection technology decide whether a replacement fits and clamps properly.

Rail and pitch

Most modular blocks snap onto 35 mm DIN rail, and the width of one block (its pitch) sets how many positions fit on a length of rail; signal and control blocks are typically 5 to 10 mm wide and power blocks are wider. Blocks from different makers do not always share jumper bars, end plates and markers, so accessories usually have to come from the same family as the block.

Wire range and connection type

Check the conductor size range (for example 0.2 to 2.5 mm2, or 24 to 12 AWG), the rated current and voltage, and the connection: screw clamp, spring clamp or push-in. Spring and push-in blocks are quicker to wire and less sensitive to loosening under vibration, but they are not automatic drop-in replacements for screw blocks, so compare the footprint before you swap.

Block function

Feed-through blocks simply connect two wires. Ground (PE) blocks bond the conductor to the rail and are usually green and yellow. Fuse and disconnect blocks hold a fuse or open the circuit. Multi-level blocks stack two or three circuits in the height of one, and power distribution blocks split one supply to several outputs. The function matters more than the colour or the brand.

What to have ready

• The catalog or series number printed on the block
• Rail type and the width of one block
• Wire size range, current and voltage
• Connection type: screw, spring or push-in
• Function and the accessories needed: jumpers, end covers, markers

Related guides and tools

• Tool: AWG Wire Gauge Chart
• Guide: Wire Ferrule Sizing Guide
• Tool: Wire & Ferrule Calculator
• Tool: Obsolete Part Lookup

Not sure which one you have? Send us the number, a nameplate photo or the dimensions and the order desk replies within 1 business day.