Wire Ferrule Crimping Guide: Color Code, Tools, and When to Use Them (2026)
Mar 23, 2026
Wire ferrules (also called cord end terminals or bootlace ferrules) are small metal sleeves crimped onto the end of stranded wire to create a solid, gas-tight termination. They prevent strand separation, improve connection reliability in screw terminals, and are increasingly required in industrial and European electrical installations. This guide covers why, when, and how to use them.
Why ferrules matter
When you insert stranded wire into a screw terminal and tighten, the strands splay. Some strands take more pressure than others. Over time, thermal cycling loosens the connection. Individual strands can escape and touch adjacent terminals, causing short circuits. Ferrules solve all three problems by consolidating the strands into a solid, uniform termination.
In European electrical standards (IEC/DIN), ferrules are mandatory for stranded wire in screw and spring terminals. US practice is catching up, particularly in industrial controls, VFD wiring, and panel building.
Ferrule color code (DIN 46228)
| AWG | mm2 | Color | Common applications |
|---|---|---|---|
| 22 AWG | 0.5 | White | PLC I/O, sensor wiring |
| 20 AWG | 0.75 | Gray | Control circuits, instrumentation |
| 18 AWG | 1.0 | Red | Control circuits, light-duty power |
| 16 AWG | 1.5 | Black | Motor control, contactors, breakers |
| 14 AWG | 2.5 | Blue | Branch circuits, sub-panels |
| 12 AWG | 4.0 | Gray | Power distribution, motor feeders |
| 10 AWG | 6.0 | Green | Heavy equipment, large VFDs |
| 8 AWG | 10.0 | Brown | Large feeders, bus connections |
How to crimp ferrules
- Strip wire: Strip insulation to the ferrule barrel length (usually 8-12mm). Use a precision stripper to avoid nicking strands.
- Insert into ferrule: Push all strands into the metal barrel. No strands should be outside the barrel. The insulation collar should sit flush against the wire insulation.
- Select die: Self-adjusting ferrule crimpers (like Knipex 97 53 14 or Weidmuller PZ 6 Roto) automatically select the correct die based on ferrule size. Manual crimpers require matching the die to the color code.
- Crimp: Place the ferrule in the die with the wire facing away from the tool. Squeeze until the ratchet releases. The crimp should be uniform and square (trapezoid profile) with no cracks in the barrel.
- Inspect: The ferrule should not rotate on the wire. Pull-test should hold firm. No visible strands outside the barrel. The insulation collar should be intact.
Single vs twin ferrules
Single ferrules terminate one wire per ferrule. This is the standard configuration for most applications.
Twin (dual) ferrules hold two wires in a single ferrule barrel for applications where two conductors share a single terminal (e.g., input and jumper in a terminal block). Twin ferrules are color-coded differently and use a longer barrel.
When ferrules are required vs optional
Required: IEC 61439 panel building, UL 508A industrial control panels (recommended practice), any terminal block specifying ferrule termination, and European electrical installations.
Optional but recommended: Any stranded wire going into a screw terminal, VFD inputs and outputs, PLC connections, and any application where vibration is present.
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