DIN Rail Terminal Block, DIN 46228 Ferrule Color Codes, and Cable Lug Sizing Guide
IEC 60947-7-1 DIN rail terminal block current ratings, DIN 46228-4 bootlace ferrule color codes, twin ferrules, and DIN 46235 vs standard tubular copper cable lug sizing.
Matching terminal blocks, bootlace ferrules, and tubular cable lugs eliminates loose-clamp hot spots and arc failures inside industrial control and distribution panels. Clamping bare Class 5 fine-stranded wire (H05V-K / H07V-K) directly under a screw shears strands and raises contact resistance; compliant panel builds use DIN 46228-4 insulated ferrules on control wires, DIN 46235 / tubular lugs on power feeders, and IEC 60947-7-1 terminal blocks on 35 mm DIN rails.
> Related Category: Filter termination components in Terminal Blocks, DIN Rail Terminal Blocks, Cable Ferrules, and Cable Lugs.
IEC 60947-7-1 DIN rail terminal block current and torque ratings
| Rated cross-section | IEC 60947-7-1 test current | Typical screw torque | Typical panel circuit |
|---|---|---|---|
| 2.5 mm² | 24 A | 0.4 – 0.6 Nm | PLC I/O, sensors, control & 16 A final circuits |
| 4 mm² | 32 A | 0.5 – 0.8 Nm | Motor control & 20–25 A feeders |
| 6 mm² | 41 A | 0.8 – 1.2 Nm | 32 A power branches & sub-circuits |
| 10 mm² | 57 A | 1.2 – 1.8 Nm | PFC capacitor stages & 40–50 A feeders |
| 16 mm² | 76 A | 2.0 – 2.5 Nm | Sub-panel incomers & 63 A breaker outputs |
| 35 mm² | 125 A | 3.2 – 4.0 Nm | Main distribution & heavy motor feeders |
| 70 – 240 mm² | 192 – 415 A | 6.0 – 20 Nm (hex / stud) | Main busbar incoming feeders |
Compare clamping technologies in Screw vs Spring and Push-in Terminal Block Difference, and use 450 V lever or push-wire junction box terminal blocks inside wall boxes.
DIN 46228-4 insulated bootlace ferrule color code chart
Tinned electrolytic copper cable ferrules identify conductor size by plastic collar color (note the difference between German DIN 46228-4 Series 2 and French Series 1 on 0.75, 2.5, and 4 mm²):
| Conductor size | DIN 46228-4 collar color | French (Series 1) color | Standard barrel length |
|---|---|---|---|
| 0.50 mm² | White | White | 8 mm |
| 0.75 mm² | Grey | Blue | 8 mm |
| 1.0 mm² | Red | Red | 8 mm |
| 1.5 mm² | Black | Black | 8 or 10 mm |
| 2.5 mm² | Blue | Grey | 8 or 12 mm |
| 4.0 mm² | Grey | Orange | 10 or 12 mm |
| 6.0 mm² | Yellow | Green | 12 mm |
| 10 mm² | Red | Brown | 12 or 18 mm |
| 16 mm² | Blue | White / Ivory | 12 or 18 mm |
Always crimp using a ratcheting ferrule crimping plier rather than side-cutters, and use twin (dual-entry) ferrules whenever bridging two fine-stranded wires into one terminal cage.
DIN 46235 vs standard tubular copper cable lugs
Tubular copper lug part numbers state conductor cross-section (`mm²`) – stud bolt size (`M`) (for example, 35–8 fits a 35 mm² copper conductor onto an M8 stud with an Ø8.4 mm palm hole):
- DIN 46235 compression lugs: Heavy-wall barrels stamped with die-code index marks and crimp-count bands for calibrated hexagonal hydraulic crimping in switchgear and transformer bays.
- Standard & eco tubular (SKP) lugs: Shorter barrels tailored to compact MCCB/ACB terminal shrouds, often with an inspection window to verify full strand insertion.
Never crimp bare aluminum conductors into pure copper lugs—see Aluminum (NAYY) vs Copper (NYY) Cable Sizing and Bimetallic Termination.
Frequently asked questions
Should ferrules be crimped onto solid Class 1 wire?
No. Class 1 solid conductors (NYA, NYM) clamp directly into screw and push-in terminals; ferrules are engineered specifically for Class 5/6 fine-stranded flexible conductors.
Can tinned solder replace a ferrule on stranded wire?
Never (IEC 60999-1 / IEC 60364-5-52). Solder creeps under screw pressure and thermal cycling, loosening the joint until arcing and overheating occur.
Can bare stranded wire enter a push-in terminal block without a ferrule?
Yes, provided you depress the orange actuator pusher button with a screwdriver to open the spring; direct tool-free push-in insertion requires either a solid conductor or a gas-tight crimped ferrule.
Why does stud hole size matter on a 50 mm² lug (e.g., 50-8 vs 50-12)?
Mounting an oversized M12 palm hole onto an M8 busbar bolt drastically shrinks palm contact area and allows the lug to twist, causing localized busbar heating.