What this MCCB is and what it does
The Siemens 3VA1120-5EF32-0AD0 is a 3-pole molded case circuit breaker from the SENTRON family, designed for line protection in distribution panels. It's rated 20 A continuous at 40 °C ambient, with a TM240 thermal-magnetic release that handles overload and short-circuit trip curves without external power. The interrupting capacity hits 187 kA at 240 V AC — that's the SCCR you'd spec for a high-fault panel feeding a motor control center or a transformer secondary. Insulation voltage is rated 800 V, so it's comfortable on 480/277 V systems with headroom.
Ratings that decide the fit
The headline number is the 187 kA interrupting rating at 240 V AC — that's the fault current this MCCB can safely clear without welding contacts or venting plasma. At 415 V it's still 121 kA, at 440 V it drops to 75.6 kA, and at 500/690 V it holds at 17 kA. For a 20 A frame, those are high-interrupt values; you're buying this for the SCCR, not the continuous current. The TM240 release means the thermal element is fixed at 20 A; no field-adjustable rating plug. Power loss maxes at 12 W, which matters for enclosure heat rise in a packed panel. Dimensions are 130 mm tall, 76.2 mm wide, 70 mm deep — standard 3-pole MCCB footprint for DIN-rail or screw-mount backpan.
Where it lands in the panel
Mounts on DIN rail or directly to a backpan via the screw terminals. The 3VA frame shares the same width and depth as the 3VA1 family, so if you're swapping a 3VA1110-5EF32-0AM0 (also 3-pole, 20 A, but with a different release or accessory set), the footprint is identical — no rewiring the bus bars or re-drilling the panel. The auxiliary switch option is listed as 3 auxiliary switches HQ, which means the breaker can accept up to three HQ-style aux contacts for status feedback to a PLC or indication lamp.