Switch disconnector in MCCB form factor
The Siemens 3VA1112-1AA42-0AD0 is a SENTRON switch disconnector built in an MCCB housing — 4-pole, rated for 125 A continuous current (Iu) across the full ambient range from 40 °C to 70 °C with no derating needed per the datasheet. That flat thermal curve simplifies panel design: you size the busbar and enclosure for 125 A at the worst-case ambient, not a derated intermediate value. Rated insulation voltage is 800 V, with maximum operational voltage 690 V AC 50/60 Hz and 600 V DC. The 4-pole configuration handles three-phase plus neutral switching in a single unit, common for main incomers or generator tie-in applications.
Mounting and connection
Main circuit connection is via busbar — front terminal arrangement — so this unit is designed to bolt directly onto a busbar system, not for cable lug termination. Panel builders should plan for busbar stabs or adapter kits; the 101.6 mm width and 70 mm depth fit standard SENTRON 3VA mounting footprints. No undervoltage release or voltage trigger is fitted on this variant; the auxiliary release slot is empty. A motor drive can be added as an optional extension if remote switching is needed later.