What this SENTRON switch disconnector is — and isn't
The Siemens 3VA1112-1AA42-0AB0 is a 4-pole switch disconnector in the SENTRON 3VA family, built on the IEC frame 160 platform with a rated continuous current Iu of 125 A. It is explicitly designed as a switch disconnector — not a molded case circuit breaker — meaning it provides no overload protection (no thermal or magnetic trip) and no short-circuit protection. Its job is safe isolation and disconnection under load, not fault interruption. Rated for AC operation up to 690 V and DC up to 600 V, with a rated insulation voltage Ui of 800 V. The 4-pole configuration switches three phases and neutral.
Key ratings and what they mean for fit
The 125 A continuous rating (Iu) governs the maximum uninterrupted current the disconnector can carry without exceeding its thermal limits. This is the number that decides conductor sizing and upstream protection coordination — the disconnector itself does not clear faults, so the upstream breaker or fuse must be sized to protect the downstream cable and load. Mechanical endurance is rated at 15 000 operating cycles — this is a latching endurance figure, meaning the mechanism is good for that many open-close operations before wear-out. For a switch disconnector used primarily for infrequent isolation (maintenance lockout, process changeover), that's a long service life; for daily switching duty, consider a contactor or load-break switch instead. Power loss is 38 W maximum at rated current. The IP40 front-face protection covers the operator interface.
Where it fits in the panel
Dimensions are 70 mm deep, 101.6 mm wide, and 130 mm tall — the 101.6 mm width (4-inch nominal) is the 4-pole frame width on the SENTRON 3VA platform. The main current circuit connects via busbar connection at the front terminal, which means it's designed for horizontal busbar systems or pre-fabricated distribution bus. No box terminals on this variant; the busbar connection is fixed. Comes with 2 auxiliary switches (HP type) pre-installed, providing 2 CO (changeover) contacts for status feedback to a PLC or indication lamp. The auxiliary contacts are wired via the front terminal block. Optional motor drive can be added via the product extension slot.