What this part is and isn't
The Siemens 3VA1112-1AA36-0AE0 is a SENTRON switch disconnector in a 3VA MCCB-style frame, rated for 125 A continuous current (Iu) across 3 poles. It is not a molded case circuit breaker — there is no overload or short-circuit protection inside this unit. The product designation and the description both make this clear: it is a switch disconnector only, designed for isolation and switching duty where the upstream protection handles the fault interruption. The frame is the IEC 160 A size, so the 125 A rating leaves thermal headroom. It carries a short-time withstand of 2 kA for 1 second — enough to ride through a downstream fault while the upstream breaker clears, but not a high-fault device itself. The 38 W maximum power loss at rated current matters for enclosure heat rise calculations; plan ventilation accordingly if you are packing several in a panel.
Auxiliary switching and connectivity
This variant ships with 4 auxiliary switches (HQ type — high-capacity, high-reliability contacts), giving you 4 CO (changeover) contacts for status feedback, interlocking, or PLC inputs. That is a lot of auxiliary capacity for a 3-pole switch disconnector; most MCCB-style switches come with 1 or 2. If your panel needs to signal open/closed status to multiple destinations, this saves adding an external auxiliary block. Connection is via front terminals (clamp-type, not box lug) for the main circuit. The terminal arrangement is front-facing, which means the switch can be panel-mounted with busbars or cables landing from the front — typical for distribution panels where rear-access is tight. The optional motor drive (not included here but supported as an accessory) allows remote switching if you need to add it later.
Where it fits — ratings and environment
Rated for AC operation up to 690 V 50/60 Hz and DC up to 500 V. The insulation voltage is 800 V, so it is comfortable in 400 V or 480 V distribution without derating concerns. Operating temperature range is -25 °C to +70 °C; storage from -40 °C to +80 °C. The IP40 front protection means it is fine inside a closed panel but not for washdown or outdoor exposure without an enclosure. Mechanical endurance is rated at 15,000 operating cycles. That is typical for a switch disconnector in this class — designed for daily isolation but not for frequent motor starting. If you need a switching device for repeated load make/break, look at a contactor instead.
Physical fit and panel integration
Dimensions are 130 mm height, 76.2 mm width, and 70 mm depth. The 3-pole frame width of 76.2 mm (3 inches) is standard for the 3VA 160 A frame — it occupies the same footprint as the equivalent MCCB version. If you are replacing a 3VA1110-5ED36-0AC0 or 3VA1112-5EE32-0AA0, the mounting hole pattern and busbar spacing are identical; the swap is mechanical, not a re-panel job.