Undervoltage release for SENTRON 3VA breakers
The Siemens 3VA9908-0BB12 is a SENTRON-branded undervoltage release accessory designed specifically for the 3VA1 and 3VA20 through 3VA25 series of molded-case circuit breakers. Rated for 48 V DC operation, the release draws a maximum of 2.5 W under steady-state DC conditions. That means it's designed for the fixed-installation environment inside a distribution panel where transient overvoltages from the mains are expected and conductive pollution (dust, condensation) is possible — typical for industrial switchgear rooms.
The accessory occupies three slots in the breaker's accessory compartment. Physical dimensions are 65.1 mm high, 25.7 mm wide, and 28.8 mm deep — the depth is the critical dimension when checking clearance inside the enclosure door or against a rear-mounted busbar. Wiring termination requires a 10 mm strip length (0.4 in) on the conductor. That's a standard measurement for cage-clamp or screw terminals in this class — set your wire stripper to 10 mm and no more; over-stripping leaves bare conductor exposed past the terminal entry.