A wire ferrule is a small metal sleeve crimped over stripped stranded wire before it enters a screw terminal. Without one, strands spread under clamping force, contact resistance rises, and connections work loose. EN 60204-1 clause 13.1.1 requires a means of retaining strands on screwed connections — a correctly crimped ferrule is the standard compliance method.
What Is a Wire Ferrule?
A wire ferrule is a short tin-plated copper sleeve crimped over stripped stranded wire before insertion into a screw or spring-clamp terminal. It consolidates loose strands into a stable cylindrical contact, prevents strand splaying under clamping force, and keeps the connection torqued over years of vibration and thermal cycling. Ferrule dimensions and materials are defined under DIN 46228 — Part 1 for uninsulated, Part 4 for insulated — covering 0.5mm² to 16mm² and above.
What Does a Wire Ferrule Do?
The problem with stranded wire in a screw terminal is mechanical, not electrical. When the clamping screw tightens directly against loose strands, a few strands carry most of the load while others deflect sideways. Contact resistance rises. Under vibration or thermal cycling, the strands compact further, the screw loses torque, and the connection loosens. In the worst case, individual strands escape the terminal entirely and create a short circuit risk on high-density terminal strips where slot spacing runs 5mm or less.
A ferrule fixes this at the source. The crimp consolidates all strands into a single copper body that the terminal clamps uniformly across its full face. Contact resistance drops. The connection stays torqued. And the ferrule’s closed end stops strands from migrating into adjacent terminal slots.
There is a secondary benefit: oxidation resistance. Tin plating on the ferrule barrel slows oxidation at the conductor surface, and the compressed crimp leaves no air gaps between strands for moisture ingress. Over a ten-year panel service life, the difference between a ferrule-terminated and a bare-wire terminated connection is measurable in contact resistance drift.
Types of Wire Ferrules
Not all ferrules are interchangeable. Four types cover the majority of industrial panel wiring applications, each suited to a different installation requirement.
Insulated ferrules (DIN 46228 Part 4) The standard choice for most panel wiring. A plastic collar — typically polypropylene or polyamide, rated to 105–110°C — extends over the stripped wire entry point, providing insulation at the termination and a grip surface for insertion. The collar is color-coded by cross-section under DIN 46228 Part 4: white for 0.5mm², grey for 0.75mm², red for 1.0mm², black for 1.5mm², blue for 2.5mm², yellow for 4mm², green for 6mm². This color coding is the fastest quality check in a dense terminal strip — a mismatched color means a wrong size ferrule, visible at a glance without a multimeter.
Non-insulated ferrules (DIN 46228 Part 1) The same copper barrel without the plastic collar. Used where space at the terminal entry is tight, where the terminal design already provides insulation, or where the installation specifies bare terminations for inspection purposes. Non-insulated ferrules require more care during installation — the unprotected barrel makes inadvertent contact with adjacent terminals more likely in confined spaces.
Twin wire ferrules A single ferrule body with a divided barrel that accepts two conductors simultaneously. Used where two wires must share a single terminal position — common in control circuits where a signal loops from one device to the next through the same terminal point. Twin ferrules eliminate the stacked-ferrule workaround (two ferrules side by side in one terminal), which is unreliable and non-compliant with most terminal manufacturers’ installation requirements.
High-temperature ferrules Standard polypropylene collars are rated to around 105°C. Applications near motor drives, transformers, or in enclosures with poor ventilation may exceed this. High-temperature variants use polyamide collars rated to 180°C or above, with the same DIN 46228 Part 4 dimensional compliance.
Wire Ferrule Sizes: How to Read the DIN 46228 Specification
Ferrule sizing follows conductor cross-section in mm², not wire gauge. The ferrule must match the conductor exactly — one size up and the crimp is loose, one size down and the conductor won’t fit or the strands bunch unevenly inside the barrel.
DIN 46228 Part 4 defines the standard insulated ferrule range:
| Cross-Section | Collar Color | Typical Pin Length |
|---|---|---|
| 0.5mm² | White | 8mm |
| 0.75mm² | Grey | 8mm |
| 1.0mm² | Red | 8mm |
| 1.5mm² | Black | 8mm |
| 2.5mm² | Blue | 8mm |
| 4.0mm² | Yellow | 12mm |
| 6.0mm² | Green | 12mm |
| 10.0mm² | Brown | 12mm |
| 16.0mm² | — | 18mm |
Pin length matters as much as cross-section. The ferrule pin must fully engage the terminal’s clamping zone — too short and the clamp contacts the collar rather than the barrel, too long and the pin protrudes beyond the terminal and risks contact with adjacent wiring. Match pin length to the terminal depth specified in the terminal block datasheet.
When Should You Use Wire Ferrules?
In a control panel, the rule is simple: whenever stranded wire terminates in a screw or spring-clamp terminal, use a ferrule.
EN 60204-1 clause 13.1.1 is the regulatory basis — finely stranded Class 5 or Class 6 conductors used with screwed connections require a means of retaining the strands. A correctly crimped ferrule is the standard compliance method. This covers the vast majority of industrial control panel wiring, where flexible stranded cable is the norm for routing through cable ducts and around components.
Three situations where ferrules are non-negotiable:
High-density terminal strips — where strand migration into an adjacent slot creates a short circuit. Ferrules are the only reliable prevention method at 5mm or narrower terminal pitch.
Vibrating environments — machine panels, motor control centres, transport equipment. Bare stranded wire compacts and loosens under vibration. A ferrule-terminated connection holds torque over the equipment service life.
Maintenance-heavy installations — where terminals are opened and re-terminated repeatedly. Bare wire frays with each re-termination cycle. A ferrule presents a clean, consistent contact every time.
Solid wire does not need ferrules — the conductor itself provides the rigid contact surface. Ferrules are a stranded-wire solution.
How to Select the Right Wire Ferrule
Three parameters, in order:
1. Cross-section — match exactly Select the ferrule cross-section to match the conductor’s nominal mm² rating. Do not round up. A 1.5mm² conductor takes a 1.5mm² ferrule — the barrel inner diameter is sized to compress the strands to the correct contact density at that cross-section. A larger ferrule leaves the crimp loose; a smaller one won’t accept the conductor cleanly.
2. Insulated or non-insulated Default to insulated (DIN 46228 Part 4) for standard panel wiring. Use non-insulated (DIN 46228 Part 1) only where the terminal entry is too narrow for the collar, or where the installation specification requires bare terminations.
3. Pin length — match terminal depth Check the terminal block datasheet for clamping depth. Standard 8mm pin covers most DIN rail terminal blocks up to 2.5mm². Move to 12mm pin for 4–6mm² and larger. When in doubt, 8mm is the safe default for control panel terminal strips.
Twin ferrule selection For twin ferrule applications, both conductors must be the same cross-section — a twin ferrule is sized for two identical conductors, not a mixed pair. Check the terminal manufacturer’s approval for twin ferrule use; not all terminals are rated for it.
All Termnex wire ferrules meet DIN 46228 Part 1 and Part 4 requirements, available in insulated and non-insulated versions across the full 0.5–16mm² range.
FAQ
What is a wire ferrule?
A wire ferrule is a short tin-plated copper sleeve crimped over the stripped end of a stranded wire before insertion into a screw or spring-clamp terminal. It consolidates the wire strands into a stable cylindrical contact, preventing splaying, loosening, and strand migration. Ferrule dimensions and materials are standardised under DIN 46228.
What is the difference between insulated and non-insulated ferrules?
Insulated ferrules (DIN 46228 Part 4) have a plastic collar that provides insulation at the wire entry point and color-codes the ferrule by cross-section for quick visual verification. Non-insulated ferrules (DIN 46228 Part 1) have no collar — used where terminal entry space is limited or where the installation specifies bare terminations. For standard panel wiring, insulated is the default choice.
Do I need ferrules on stranded wire?
In industrial control panels, yes. EN 60204-1 clause 13.1.1 requires that finely stranded conductors used with screwed connections have a means of retaining their strands. A correctly crimped ferrule is the standard compliance method. Solid wire does not require ferrules.
What size ferrule do I need?
Match the ferrule cross-section exactly to the conductor’s nominal mm² rating. For pin length, 8mm covers most DIN rail terminal blocks up to 2.5mm²; use 12mm for 4–6mm² conductors. Check the terminal block datasheet for clamping depth when in doubt.
What is DIN 46228?
DIN 46228 is the German standard that defines dimensions, materials, tolerances, and test requirements for wire end ferrules. Part 1 covers non-insulated ferrules, Part 4 covers insulated ferrules with plastic collars. Most industrial ferrule products reference DIN 46228 compliance as the baseline quality standard.
Can I use one ferrule for two wires?
Only with a twin wire ferrule specifically designed for that purpose. Standard single ferrules must not be used with two conductors — the barrel is sized for one conductor cross-section and the crimp will be unreliable. Twin ferrules require both conductors to be the same cross-section, and the terminal block must be rated for twin ferrule use.
Termnex Wire Ferrules
Termnex supplies insulated and non-insulated wire ferrules across the full DIN 46228 range, from 0.5mm² to 16mm², with twin wire ferrule options for shared terminal applications. CE certified. Sample orders dispatch within 3–5 business days with MOQ of 1 piece for evaluation.
Contact the Termnex team for specifications and bulk pricing: https://termnex.com/contact-us/
