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How is the earthing continuity assured between the Masterpact and the metallic switchboad?

Published date: 24 January 2019

Masterpact circuit breakers are mainly installed in metal enclosures. Even if the enclosure is painted, earthing continuity between each part of the switchboard is assured by using dedicated screws, nuts, bolts delivered by the manufacturer (washers with claws which scratch the paint). This equipotential bonding will protect the persons and property against the effects of an electric shock. The structural part of the metallic switchboard contributes to conduct the earth fault current to the ground.

The standard IEC-61439-1, paragraph 8.4.3.2.2 defines: "All exposed conductive parts of the ASSEMBLY shall be interconnected together and to the protective conductor of the supply or via an earthing conductor to the earthing arrangement. These interconnections may be achieved either by metal screwed connections, welding or other conductive connections or by a separate protective conductor."

If the Masterpact circuit breaker with or without chassis is installed in a metallic enclosure, it is grounded through the screws tightened into the mounting plate. If there is some insulation part interrupting the earthing continuity or there is a special requirement defined by the beneficiary, the earthing openings on the chassis side of NT / NW can be used.
The additional connection to the earthing conductor can be made using a PE cable with a cross section of 10mm².

Recommended screw to be used: GENERAL SCREW METRIC; Machine Screw; Hexalobular Socket; Countersunk Head; -; M8; LENGTH 16mm; Steel; 8.8; 0; Zn8/C

 

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