Maintenance following tripping of a molded case circuit breaker
If a 3VA molded case circuit breaker trips on overcurrent (overload, short circuit) or residual current (ground fault or via residual current device), the cause of the trip must be identified and rectified before the molded case circuit breaker is switched on again.
In the case of 3VA1 molded case circuit breakers with thermal-magnetic trip units, the cause of tripping can be determined, for example, with the assistance of the short circuit alarm switches SAS. With 3VA2 molded case circuit breakers, the cause of tripping can be output via the EFB300 external function box. With electronic trip units ETU 5-series and 8-series, the cause of tripping can be indicated on the LCD display and optionally transferred via communication modules.
An inspection as described in chapter Regular maintenance should be carried out every time the molded case circuit breaker is tripped by the trip unit. In addition, all black residues on the molded case circuit breaker must be removed as they might contain conductive particles. The molded case circuit breaker should then be switched on and off without load at least five times.