What this MCCB carries and where it fits
The Siemens SENTRON 3VA1120-3EF32-0DH0 is a 3-pole molded case circuit breaker rated for 20 A continuous current at 40 °C, with a TM240 thermal-magnetic overcurrent release. It's built for line protection — meaning it guards the feeder or branch circuit against overload and short-circuit, not a specific motor or load. The interrupting ratings climb to 75.6 kA at 240 V and 52.5 kA at 415 V, so it can handle substantial fault currents on a 400 V industrial panel without needing an upstream fuse to back it up. Derating is real with this one: it holds a full 20 A up to 50 °C, then drops to 19.2 A at 55 °C and 18 A at 70 °C. If the panel runs hot — say near a drive stack or in a non-climate-controlled enclosure — size the load against the ambient curve, not the nameplate.
Panel fit and auxiliary wiring
The 3VA1120-3EF32-0DH0 measures 76.2 mm wide by 130 mm tall by 70 mm deep — a compact footprint for a 3-pole MCCB in the 20 A class. It mounts directly onto a DIN rail or panel plate via the standard SENTRON base; no adapter kit required. It ships with 2 auxiliary switches and 1 trip alarm switch (HQ type) integrated, plus an undervoltage release (UVR) as the auxiliary release. The UVR is wired in series with the control supply; if that supply drops, the breaker trips. This is standard for emergency-stop or safety-circuit separation — not a communication-enabled breaker, so no Modbus or PROFIBUS on this variant. Front protection is IP40 — fine for a dry indoor panel, but not rated for washdown or outdoor exposure. The integrated auxiliary trip is order code 3VA9608-0BB25, which is a separate line item if you need a replacement or spare.
Selectivity and coordination notes
With interrupting ratings of 75.6 kA at 240 V, 52.5 kA at 415 V, 32 kA at 440 V, and 10.5 kA at 690 V, this MCCB provides solid SCCR headroom for most 400 V distribution panels. At 690 V the 10.5 kA rating is lower — if your system runs at that voltage and has a high available fault current, verify coordination upstream. The TM240 release is thermal-magnetic: the thermal element handles overloads, the magnetic element handles short-circuits. Latching endurance is 15,000 operations.