Earthing and Equipotential Bonding Fittings

Earthing and equipotential bonding screw connections enable direct current transfer through the screw when insulating layers such as paint or oxide prevent direct contact between conductors. Electrical conductivity is enhanced by special contact discs, while mechanical requirements—such as embedding and relaxation behavior—must be taken into account through an elastic design. Due to the lack of standards, the design of such connections is practice-oriented and follows proven recommendations, e.g., from *Elektropraktiker* or from manufacturers such as Rittal. In such cases, electrical conductivity is specifically established or supported by contact discs—e.g., of the NSK®-K type.

Function and scope
of application: Earthing and equipotential bonding screw connections are used to transfer current directly via the screw connection when insulating layers, such as paint or oxide, prevent a direct conductive connection between two conductors. In such cases, electrical conductivity is specifically established or enhanced by means of contact discs – e.g. of the NSK®-K type.

Typical applications
This type of screw connection is used in particular for situational current flows, such as equipotential bonding or earthing. A typical example of application is the earthing screw connection on a painted switch cabinet sheet metal panel, where the screw ensures electrical contact across the insulating paint layer.

Regulatory framework
There are no binding regulatory requirements governing the design of electrical screw-type connections. Consequently, practical recommendations from specialist sources such as ‘Elektropraktiker (EP)’ or from manufacturers such as Rittal are of particular importance for the design and implementation.

Design recommendations
From a technical perspective, it is advisable to minimise the number of components used and the number of interface surfaces in order to reduce settlement and increase mechanical stability. At the same time, the assembly should have a spring-like effect – for example, through the use of suitable spring washers – to compensate for creeping, embedding and relaxation effects.

Holistic approach
The design of such bolted connections must not only be electrically conductive but also mechanically stable over the long term. Earthing and equipotential bonding bolted connections thus represent a combined electrical and mechanical functional unit, the reliable operation of which depends on careful planning and implementation.

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