The Siemens 3VA1120-5EF32-0HC0 is a SENTRON molded case circuit breaker built for line protection in distribution panels. Three poles, 20 A continuous at 40 °C, and a short-circuit breaking capacity that hits 187 kA at 240 V AC — that's the headline number for high-fault service entrances or industrial sub-distribution where the upstream transformer can dump serious current into a bolted fault. The 187 kA at 240 V tells you this breaker is sized for the high-end of SCCR requirements on 240 V delta or 240/120 V center-tapped services. Drop to 415 V and it still holds 121 kA; at 440 V it's 75.6 kA; at 500 V and 690 V it holds 17 kA. That curve means the breaker clears fast enough to protect downstream gear across a wide voltage range without cascading failure — useful when the same panel feeds both 480 V and 240 V loads through separate transformers. Rated insulation voltage is 800 V, so the internal clearances and creepage are built for 690 V systems with margin. The 20 A rating holds flat from 40 °C through 55 °C, then derates to 19 A at 60–70 °C — no surprise for a thermal-magnetic MCCB, but worth noting if the breaker lives in a hot enclosure next to a transformer or drive.
Auxiliary and shunt trip fit
This variant ships with a shunt trip (STL) release and two auxiliary switches HQ factory-installed. The shunt trip lets a remote signal — from an E-stop, fire alarm relay, or PLC output — open the breaker electrically without a person at the handle. The two auxiliary switches provide status feedback (open/closed/tripped) to the control system or HMI. No undervoltage release on this code; if UVR is required, that's a different suffix. The auxiliary switches are designated HQ type — that's Siemens' notation for early-make / late-break contacts used in signaling circuits. They mount on the left side of the breaker and are wired through the terminal cover. The shunt trip coil draws from the control voltage; verify polarity and voltage rating against the panel's control transformer before wiring.
Panel fit and footprint
Dimensions: 76.2 mm wide, 130 mm tall, 70 mm deep. Maximum power loss is 12 W at rated load. That's moderate for a 20 A MCCB; in a dense panel with multiple breakers side-by-side, account for the cumulative heat in the enclosure sizing calculation.