What this part is and what it does
The Siemens 3VA1112-1AA36-0AF0 is a SENTRON switch disconnector in the 3VA1 IEC frame 160 platform — a three-pole device rated for 125 A continuous current (Iu) that provides visible isolation of a circuit but carries no overload or short-circuit protection elements. It is designed strictly as a load-break disconnect for maintenance and safety isolation, not as a circuit breaker. The part ships with one auxiliary switch HQ and one trip alarm switch HQ integrated, giving two CO contacts for status feedback to a PLC or indicator lamp.
Key ratings and what they mean for fit
Rated continuous current Iu is 125 A — this is the maximum current the disconnect can carry continuously without exceeding its thermal limits. The maximum power loss at that load is 38 W, so panel ventilation matters if multiple units are ganged. Rated insulation voltage Ui is 800 V, and the maximum operational voltage is 690 V AC (50/60 Hz) or 500 V DC. That DC rating is the one to watch for battery or rectifier circuits: the disconnect can handle 500 V DC, but the switching arc behavior is different from AC, so verify the DC switching capacity for your specific load type. Short-time withstand current is rated at 2 kA for both 0.5 s and 1 s durations. This tells you the disconnect can survive a fault current up to 2 kA for up to one second without welding its contacts — but it will not interrupt that fault. Upstream protection (a fuse or circuit breaker) must clear the fault before the disconnect's thermal limit is reached. The mechanical endurance is 15,000 operating cycles, which is typical for a panel disconnect that sees daily switching but not continuous motor starting. Operating temperature range is -25 °C to +70 °C, with storage from -40 °C to +80 °C. The IP40 rating on the front means it is protected against tools and wires >1 mm but not against water ingress — mount it inside an enclosure rated for the environment.
Where it goes in the panel
The 3VA1112-1AA36-0AF0 mounts on a DIN rail via the standard 3VA frame footprint: 70 mm deep, 76.2 mm wide (3 inches), 130 mm tall. That is the same physical envelope as the 3VA1 molded-case circuit breakers, so it drops into the same panel layout. Front terminal connection for the main circuit — clamp-type terminals accept copper or aluminum conductors. The auxiliary contact block is factory-integrated, so no add-on module occupies adjacent DIN space. An optional motor drive can be added for remote switching (product extension optional).
How it compares to the 3VA1110-5EF32-0AM0
The closest functional peer in the same frame is the 3VA1110-5EF32-0AM0, which is a full molded-case circuit breaker with thermal-magnetic overcurrent protection (TM240), rated 100 A at 40 °C, and carries a much higher interrupting capacity (187 kA at 240 V AC). By contrast, the 3VA1112-1AA36-0AF0 is a switch disconnector only — no overcurrent trip, no fault interruption capability, and a lower short-time withstand (2 kA). The physical footprint is identical (same 70×76.2×130 mm envelope), so a panel designed for the breaker can accept the disconnect without rewiring the bus bars or DIN-rail position. The decision between them is purely functional: if the circuit already has upstream overcurrent protection and you only need a local disconnect, the 3VA1112-1AA36-0AF0 is the correct choice; if you need integrated branch-circuit protection, use the 3VA1110-5EF32-0AM0.