The Siemens 3VA1112-1AA42-0BH0 is a SENTRON 3VA1 switch disconnector in an MCCB design, rated for 125 A continuous current across the full operating temperature range from 40 °C to 70 °C — no derating needed up to that ceiling. It is a 4-pole unit (SD100) with no overload or short-circuit protection built in, so it functions purely as a disconnect and isolation device, not a circuit breaker. This variant ships with a factory-fitted undervoltage release (UVR) rated for 24 V DC, plus two auxiliary switches HQ and one trip alarm switch HQ — three CO contacts total. The UVR includes no leading contact, so it drops out immediately on voltage loss below the release threshold.
What the 125 A rating means for fit
The 125 A rating is flat from 40 °C through 70 °C ambient — that is unusual for a molded-case switch and means no thermal derating curve to calculate for most panel environments. The insulation voltage is rated at 800 V, with operating voltage at 690 V AC or 600 V DC, so it handles 480/600 V industrial feeds comfortably. Because it carries no overcurrent trip elements, it is sized purely for the load current and fault-withstand capability of the downstream protection. Use it where a visible break and lockout isolation are required ahead of a fused or breaker-protected branch — typical for motor disconnects or panel main switches where the upstream device handles the fault interruption.
Panel integration and wiring
Front terminal connections for the main circuit, busbar-compatible. Dimensions are 70 mm deep by 101.6 mm wide by 130 mm tall — fits a standard 4-pole MCCB footprint on the DIN rail or panel-mount plate. IP40 on the front, so it is suited for enclosed panel use, not washdown. Mechanical service life is 15,000 operating cycles typical. Optional motor drive can be added for remote switching. The auxiliary switch complement (2 HQ + 1 trip alarm) gives status feedback for PLC or indication circuits without an add-on module.