Extraneous-Conductive-Parts: What Is it? (Definition, Meaning, Examples)

Extraneous-conductive-part: conductive part not forming part of the electrical installation and that is likely to introduce an electric potential, generally the electric potential of a local earth (defined in the IEC 60050-195-2021).

The term “extraneous-conductive part” is hyphenated which means it’s a single word with specific meaning.

In Annex B of IEC 60364-1 the definition of this term from IEC 60050-195 is supplemented by the following note:

Extraneous-conductive-parts may be:

  • metallic parts of the building structure;
  • metal pipe systems for gas, water, heating, etc.;
  • non-insulating floors and walls.

The British Standard BS 7671 defines the term “extraneous-conductive-part” as follows:

A conductive part liable to introduce a potential, generally Earth potential, and not forming part of the electrical installation.

BS 7671:2018+A1:2020

A modern building has a large number of structural elements and equipment that can conduct electric current. These elements, while actually conductive parts, are not part of an electrical installation of the building. To identify the conductive parts of the building and the non-electrical equipment installed in the building, the international regulatory documents use the term “extraneous-conductive-part”.

In order to ensure that extraneous-conductive-parts of the building have an electrical potential equal to that of the local earth potential, they must generally be earthed. To this end, extraneous-conductive-parts are connected to the main earthing terminal by means of the primary equipotential bonding conductors. Supplementary equipotential bonding conductors can also be connected to extraneous-conductive-parts.

What Is an Example of an Extraneous-Conductive-Part?

Extraneous-conductive-parts include all metal structures of the building, such as steel beams and fittings, floors and walls made of sheet metal, as well as equipment installed in the building that is made of conductive materials: metal pipes of gas pipes, water pipes and heating systems, gas stoves, metal baths, sinks, radiators, faucets, etc.

Cast iron bathtub as an example of an extraneous conductive part
Figure 1. Cast iron bathtub as an example of an extraneous-conductive-part


How Do I Determine an Extraneous Conductive Part?

Extraneous conductive parts are any metallic objects that are not intended to be part of the electrical circuit. These parts can create shorts, causing electrical problems. To determine if an object is an extraneous conductive part, follow these steps:

– First, disconnect all power sources from the circuit. This includes removing batteries and unplugging cords from outlets.
– Next, using a multimeter set to the ohmmeter function, touch one probe to one end of the suspected extraneous conductive part. Touch the other probe to the other end of the part.
– If the multimeter reading shows continuity (a complete circuit), then the object is an extraneous conductive part and should be removed from the circuit.
– If the multimeter reading shows no continuity (an open circuit), then the object is not an extraneous conductive part and can be left in the circuit.

Is a Metallic Tray an Extraneous-Conductive-Part?

Yes, a metallic tray can be considered an extraneous-conductive-part. Any time there is a potential for electrical current to flow through a metal surface, there is the potential for that surface to become an extraneous-conductive-part. When this happens, it can create serious safety hazards.

What Is the Difference Between Exposed and Extraneous-Conductive-parts

The main difference between exposed and extraneous-conductive-parts is that the former are parts of electrical equipment which may become energized and thus pose a risk of electric shock, while the latter are parts which are not intended to be energized but may contact energized parts and create a risk of shock.

Another key difference between exposed and extraneous-conductive-parts is that the former must be insulated from all other conductive parts, while the latter need only be insulated from live (energized) parts.

Sources of Further Information

  • IEC 60050-195-2021
  • EC 60364-1
  • BS 7671:2018+A1:2020