Ferrules Can Be Used for Better Electrical Connections

Posted on 6/13/18 12:40 PM


A ferrule is an internal component that can be used for better electrical connection in applications where the spread of bare strands could cause a problem.

Ferrules offered by Interpower come in two styles—insulated and uninsulated. The insulator, which helps to eliminate arcing in the assembly, is added to the “top” of the ferrule.

 Uninsulated Ferrule  Insulated Ferrule  Doubl-Wire Insulated Ferrule
82031120_1.5   82031260_6 82031510_10 DBL ferrule 

Ferrules are sized by metric measurement, so international wire sizes will fit properly in the ferrules. North American conductors are not sized metrically, so the metric size of North American conductors is approximate. For example, 18 AWG conductor is approximately 0.82mm2. The size is between the metric 0.75 and 1.00mm2. A ferrule meant for 0.75 will be too small, so the next size larger will be needed. (See Ferrules for more details.)

Selecting a Ferrule

In selecting the kind of ferrule to use, there are several factors that should be considered.

  • It needs to be determined whether it will be insulated or uninsulated for the application.
  • It needs to be determined if the application requires a double-wire ferrule, which is an insulated version, and is designed to accept only two wires. 
  • The conductor size needs to be identified. There may be a need to convert from metric wire sizes to AWG sizes. (For reference: Metric conversion guide.)
  • Insulated ferrules can be color coded, while uninsulated ferrules are not. The colors correspond to the rated wire size and each code uses different colors for individual sizes.

Securing Connections with a Ferrule

Using a ferrule can help to ensure that all of the individual wire strands will be conducting current properly.

ferrule-uncrimped If the wire is stranded, the individual strands may tend to move out of the way of the screw as it is tightened. An electrically acceptable connection may or may not exist.
ferrule-crimped One way to ensure a solid electrical connection is to crimp the ferrule. It is important that the ferrule is sized properly so that is slides onto the wire easily. The wire should fill at least 80% of the ferrule.

An insulated ferrule helps to minimize the chance that a loose strand will cause a short circuit.


For proper installation, Interpower recommends using a tool specifically designed for crimping ferrules.

Additional Resources

For more details about how to select the kind of ferrule to use, see Ferrules and the Ferrule Selection Guide. 

If you have questions, Interpower offers free technical support, along with value-added services. For further assistance, please see Interpower’s contact information below.

Topics: product design, ferrules, wire

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