What it is and where it fits
The Siemens 3VA1112-1AA42-0AA0 is a SENTRON switch disconnector built in an MCCB-style housing — 4 poles, rated 125 A continuously from 40 °C through 70 °C ambient, with no overload or short-circuit protection (it is a disconnect-only device). It mounts on a DIN rail or panel base via the front terminal arrangement, accepting busbar connections for the main circuit. The 70 mm depth and 101.6 mm width fit standard IEC distribution panel cutouts; the IP40 front protects against tool entry and solid objects larger than 1 mm. Rated insulation voltage is 800 V, with AC operating voltage up to 690 V and DC up to 600 V.
What the ratings mean for fit
The 125 A rating holds flat across the full 40 °C to 70 °C operating range — no derating curve to calculate for warm enclosures. That matters when the disconnector sits near transformers or other heat sources in a panel. The 4-pole configuration isolates all three phases plus neutral, typical for three-phase distribution with a switched neutral. No undervoltage release, no auxiliary switch, no trip indicator — this is a pure manual disconnect, not a motor-protective device. The mechanical life of 15 000 operating cycles is standard for a panel-mounted switch disconnector used for infrequent isolation, not daily switching. Maximum power loss of 38 W at rated current helps size enclosure ventilation.
Panel integration notes
Front-terminal busbar connection — the main circuit wires land on the front face, not the rear, which simplifies busbar routing in a distribution board. The 70 mm depth leaves clearance behind the panel door for cable bending. No auxiliary contacts or releases are included; if you need remote status or undervoltage trip, this variant does not carry them. An optional motor drive can be added later for remote switching. Storage temperature range from -40 °C to 80 °C covers most warehouse conditions.