The Siemens 3VU2931-4C is a release detector module designed as a field-serviceable add-on for the 3VU2.4 and 3VU2.5 motor-protective circuit-breaker frames. It carries one normally-open contact, one normally-closed contact, and a dedicated release detector that signals when the breaker has tripped on overload or short-circuit.
Where it snaps in
This module clips directly onto the side of the 3VU2.4 or 3VU2.5 breaker — no tools, no wiring between the two. The release detector mechanically couples to the breaker's trip mechanism, so when the breaker opens, the detector changes state and the 1NO/1NC contacts follow. That gives the panel a positive remote signal that the motor circuit is off, without needing an auxiliary contact block that might miss a fault trip.