What this part is and what it does
The Siemens 3VA1112-1AA42-0CA0 is a SENTRON switch disconnector in MCCB design — a 4-pole, 125 A rated disconnect that provides visible isolation for a circuit without overload or short-circuit protection. It is built to the IEC 60947-3 standard for switch-disconnectors, meaning its primary job is safe on-load switching and isolation, not protection. The part carries a continuous current rating of 125 A across the full ambient temperature range from 40 °C to 70 °C, so no derating is needed up to that ceiling. Rated operational voltage is 690 V AC and 600 V DC, with an insulation voltage of 800 V. The built-in undervoltage release (UVR) is factory-set for 120-127 V AC 50/60 Hz. When control voltage drops below the dropout threshold, the UVR trips the disconnector open — a standard safety function for motor circuits where loss of control power should automatically disconnect the load. The UVR does not include a leading contact for delayed dropout; it releases immediately on undervoltage. Connection is via busbar to front terminals, which is the typical arrangement for panel-mounted MCCB-style disconnectors in distribution boards. The front terminals accept busbar connections for the main current circuit. An optional motor drive (field-installable) is available for remote switching. Mechanical service life is rated at 15,000 operating cycles typical.
Physical fit and environmental limits
Dimensions: 70 mm depth, 101.6 mm width, 130 mm height. The width of 101.6 mm (4 inches) is the standard 4-pole MCCB footprint for this frame size. Front protection class is IP40 — suitable for enclosed distribution boards where the front face is behind a door. Operating temperature range is -25 °C to 70 °C; storage range is -40 °C to 80 °C. Maximum power loss at rated current is 38 W, which should be factored into enclosure thermal calculations.
What it does not include
This is a switch disconnector only — it has no overload protection (no thermal or magnetic trip), no short-circuit protection, and no trip indicator. It is not a circuit breaker. It has no auxiliary contacts (0 CO contacts) and no auxiliary switch. Communication function is not present. The part is designed for applications where isolation and on-load switching are required, and overcurrent protection is provided separately upstream.