The Siemens SENTRON 3VA1112-1AA42-0KA0 is a 4-pole switch disconnector in an MCCB-style package, rated 125 A continuous across the full 40 °C to 70 °C ambient range — no derating needed as the panel warms up. It carries the IEC frame 160 footprint and comes factory-fitted with a shunt trip (STL) release for remote tripping on 220–250 V DC or 208–277 V AC control circuits.
What the ratings mean for your BOM
Rated insulation voltage Ui is 800 V, and the maximum operating voltage reaches 690 V AC or 600 V DC — so it handles 480 V and 600 V class systems comfortably, with headroom for 690 V industrial networks. The 125 A rating holds flat from 40 °C through 70 °C, meaning a panel that runs hot (say, 55 °C inside the enclosure) still carries the full 125 A without a sizing penalty. That flat curve is unusual for a switch disconnector and simplifies panel design. The shunt trip release is a voltage-trigger device — apply control voltage and it opens the switch. It is specified for 220–250 V DC or 208–277 V AC, which covers common North American and European control voltages. There is no undervoltage release or auxiliary switch on this variant; the shunt trip is the only auxiliary release fitted. Mechanical service life is 15 000 operating cycles typical. For a switch disconnector used mainly for isolation (not frequent motor starting), that is a solid figure — it will outlast most panel reconfigurations.
Panel fit and integration
Front terminals accept busbar connection — the main current circuit is wired from the front, which keeps the panel layout clean and allows busbar stacking. Dimensions are 70 mm deep, 101.6 mm wide, 130 mm tall. The 4-pole width (101.6 mm) is roughly 4 inches, so it occupies a standard 4-module MCCB footprint on the DIN rail or mounting plate. Front IP40 protection means it is splash-safe in a closed panel but not washdown-rated. Power loss is 38 W maximum at rated current. That is moderate for a 125 A 4-pole device — account for it in the enclosure thermal calculation, especially if several units are ganged.