The Siemens SENTRON 3VA1112-1AA42-0KC0 is a 4-pole switch disconnector in MCCB design, rated for 125 A continuous current on the IEC 160 A frame. This is a pure isolator — it carries no overload or short-circuit protection, so it is specified where the upstream breaker handles fault interruption and this device provides visible isolation and switching. The shunt trip release (STL) operates on 220–250 V DC or 208–277 V AC, and the two HQ auxiliary switches report the main contact position back to the control system.
What the ratings mean for fit
Rated continuous current Iu is 125 A on a 160 A frame — that is the maximum current it can carry continuously without exceeding the 70 °C operating limit. The 4-pole design means it simultaneously disconnects all three phases and the neutral, which is mandatory for TN-S or TT systems where the neutral must be switched for full isolation. Rated insulation voltage Ui is 800 V, and the maximum operational voltage is 690 V AC 50/60 Hz or 600 V DC, so it covers 400 V and 480 V distribution panels with headroom. The shunt trip voltage range (220–250 V DC / 208–277 V AC) matches standard control voltages in North American and European panels. If your control voltage is 24 V DC, this release will not pick up — you need a different undervoltage or shunt trip variant.
Panel integration
The 3VA1112-1AA42-0KC0 mounts via the front terminals with busbar connection for the main circuit — it is designed for DIN-rail or direct-panel mounting in a distribution board. Dimensions are 70 mm deep, 101.6 mm wide, and 130 mm tall. The 4-pole width means it occupies four module spaces on the rail. IP40 on the front means it is protected against tools and small wires entering from the front, but not against water ingress — install inside a rated enclosure if washdown or outdoor exposure is expected. The two HQ auxiliary switches are built-in; no separate aux block purchase is needed for status feedback.