Siemens 3VA1112-1AA42-0AC0 is a SENTRON switch disconnector in MCCB design — 4-pole, rated 125 A continuous across 40 °C to 70 °C without derating. This is a pure disconnect — no overload protection, no short-circuit protection. The description flags it as SD100 (switch disconnector), so it's intended for isolation and switching under load where upstream protection (a fuse or MCCB) handles the fault clearing. The 2 HQ auxiliary switches (2 CO contacts) give status feedback to a PLC or panel lamp. Rated insulation voltage is 800 V, operating voltage 690 V AC and 600 V DC. Mechanical service life is 15,000 operating cycles typical.
Panel fit and integration
Dimensions are 70 mm deep by 101.6 mm wide by 130 mm high. Front IP40 protection on the front. Operating temperature range is -25 °C to 70 °C; storage range -40 °C to 80 °C. The auxiliary switch block is integrated as 2 HQ switches — these are high-rupturing-capacity microswitches suitable for direct switching of PLC inputs without an interposing relay in most cases. No undervoltage release, no voltage trigger, no communication function. Motor drive is listed as an optional extension.
Maximum power loss is 38 W. That's the heat to account for in the enclosure thermal calculation. For a 125 A disconnect running near full load, it's not negligible — plan ventilation or derating if the panel is densely packed.