Know how - Bootlace Ferrules

Using bootlace ferrules is an easy way to improve the reliability of electrical connections when terminating stranded wires. Here's what you need to know from colour codes to types and tips on where to use them.

by Gordon Routledge
Sunday 10th May 2020

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Bootlace ferrule french and german colours — Ferrules come in a wide range of colours and types.

Why use ferrules?

A ferrule is a tinned copper sleeve which captures the individual strands of a stranded wire. By adding a ferrule to a wire termination, you are essentially giving a stranded conductor the properties of a solid conductor and therefore enabling a more reliable electrical connection. An alternative to using ferrules would be tinning wires with solder. However, the soldering process can damage wire insulation, and is a risky process to perform on-site or alongside other electrical assemblies

VIDEO - Improving the reliability of electrical connections with ferrules

By capturing and fixing the strands together, you can reduce the potential to damage the conductor by screw terminals. Ferrules also make sure all fine strands of copper make it into the connector. By using a defined ferrule pin length conductors can be prepared to the same length required by a chosen connector.

ferrules safely capture individual strands of copper wire

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Ferrule colour codes

Ferrule colour codes can be very confusing. There are two manufacturer led systems the French system, initially developed by Telemecanique (T), and the German system by Weidmuller (W). Both of these are in everyday use alongside an official German DIN standard.

VIDEO - Ferrule colour codes

Download a printable ferrule colour code

The shoulder colour on insulated ferrules identifies the matching conductor size. However, the three systems contradict each other with different shoulder colours for a conductor of the same size. For example, a black ferrule indicates 1.5mm2 in French and DIN standards but is a 6.0mm2 conductor in the German Weidmuller system. The DIN and French ferrule colour code repeats colours, particularly as conductor sizes increase. With red used for 1.0mm2 and 35.0mm2 in the French system and 1.0mm2, 10.0mm2 and 35.0mm2 in the DIN standard.

Ferrule types

VIDEO - Ferrule types,tips and where to use them

Uninsulated ferrules

Ferrules are available without the plastic shoulder. The non-shouldered or uninsulated versions are useful when termination space is tight or where a shoulder would obstruct an adjacent terminal. You will often see uninsulated shoulders in factory-made wiring found in 13A plugs or flying leads on UK style RCBO's.

Insulated ferrules are easier to work with, especially on smaller conductors, where the shoulder helps to guide wire strands to the ferrule pin. Without the shoulder, uninsulated ferrules can be like threading a needle.

Uninsulated ferrules are useful when termination space is limited.

Twin wire ferrules

Twin, dual or double wire ferrules are useful when you need to wire two conductors into one terminal—often seen when creating a common supply to push button switches in industrial panels. In a residential setting, they are handy to connect multiple terminals within heating or lighting controls. Twin ferrules are available in as insulated or uninsulated versions. Insulated versions have an oval-shaped shoulder to accommodate two conductors including insulation.

A twin ferrule used to insert two conductors in to a small terminal.

The colour coding for twin ferrules follows the same system as a single insulated ferrule—a twin 2.5mm2 in the German (W) system has a blue shoulder. The barrel has double the cross-sectional area - 5.0mm2 (2 x 2.5mm2)

Twin ferrules follow the same colour code as single ferrules

Ferrules are available in a wide range of pin lengths to suit the location of an electrical terminal. A longer ferrule pin is useful to reach recessed PCB terminals within an electrical enclosure. Or they are matched to the exact size of terminals on control or switchgear.

2.5mm2 insulated ferrules are available with 8, 10, 12 or 18mm pins

16mm2 are available with 15 or 21mm pins