3VA molded case circuit breakers equipped with the electronic trip unit systems ETU 3-series, ETU 5-series and ETU 8-series can be optionally upgraded with an EFB300 external function box.
The EFB300 external function box receives information from the ETU via a cable connection. This information can be used to output active trip alarms and tripping reasons (configurable using powerconfig), which are attributable to a thermal overload event, as remote feedback via four digital outputs.
Zone selective interlocking functionality (ZSI, see chapter Zone Selective Interlocking) can also be implemented via the EFB300. The EFB300 also supplies the ETU with power which means that the ETU can be parameterized via the display even when a 3VA molded case circuit breaker is in the de-energized state.