What this part is and what it does
The Siemens 3VA1112-1AA36-0BH0 is a SENTRON IEC frame 160 switch disconnector — a 3-pole, 125 A rated continuous current device designed for isolation and switching of loads under load, but without integral overload or short-circuit protection. It's built for applications where the upstream protection is handled separately and the requirement is a reliable, lockable disconnect point with auxiliary status feedback. Rated for 690 V AC and 500 V DC, with a 125 A continuous rating (Iu).
Key ratings and what they mean for fit
The 125 A continuous rating sets the maximum uninterrupted current. The 800 V rated insulation voltage (Ui) provides headroom for 690 V systems. The undervoltage release (UVR) is a DC coil that trips the switch when control voltage drops below its dropout threshold. It holds in when energized and releases when power is removed. The switch is rated for 2 kA limited to 1 second and 2 kA limited to 0.5 seconds — this is the short-time withstand current, not a breaking capacity. It means the switch can pass a fault current of 2 kA for up to 1 second without damage, which is typical for a disconnect that relies on an upstream breaker for fault interruption. In a panel with a 50 kA SCCR upstream, this switch is fine as long as the upstream device clears the fault within its rated time. Temperature range: operates from -25 °C to +70 °C, stores from -40 °C to +80 °C. The 38 W maximum power loss at full load means the switch dissipates heat into the enclosure — in a sealed panel with multiple devices, derating may be needed above 40 °C ambient.
Where it goes and how it mounts
The 3VA1112-1AA36-0BH0 is a front-terminal device with clamp connections for the main circuit — no lug kit required, just strip and clamp. The 70 mm depth, 76.2 mm width, and 130 mm height fit the standard 3VA IEC frame 160 footprint, which is common across the SENTRON 3VA family. IP40 on the front means it's protected against tools and wires >1 mm but not against dust ingress; it's intended for enclosed panel mounting, not standalone outdoor use. The optional motor drive (product extension) allows remote motorized operation — useful for applications where the disconnect must be opened from a DCS or SCADA without an operator pulling the handle. The auxiliary contacts are wired via the front terminal block, accessible with the switch in place.