What it is and what the ratings mean
The Siemens 3VA1120-5EF32-0HA0 is a SENTRON molded case circuit breaker (MCCB) with three poles, sized for line protection in distribution panels. Its 20 A continuous rating holds across the 40 °C to 55 °C range, then derates to 19 A from 60 °C up to the 70 °C operating maximum — so if the panel runs hot, you lose 1 A of headroom, not a full trip point shift. The TM240 thermal-magnetic release handles overloads and short-circuits; the shunt trip (STL) lets a remote signal or safety relay force the breaker open, which matters when you need an emergency stop to kill power without someone running to the panel.
Breaking capacity — the real coordination number
The interrupting rating is what decides whether this breaker clears a fault or welds shut. At 240 V it's rated 187 kA; at 415 V it drops to 121 kA; at 440 V it's 75.6 kA; and at 500 V or 690 V it's 17 kA. That steep voltage-dependent curve means you cannot assume the 240 V number holds at a higher system voltage — coordination studies need the specific fault current at the point of installation. The 800 V rated insulation voltage (Ui) confirms the internal clearances are designed for 690 V systems, but the actual breaking capacity at that voltage is the 17 kA figure, not the headline 187 kA.
Panel fit and physical constraints
The 3VA1120-5EF32-0HA0 measures 70 mm deep, 76.2 mm wide, and 130 mm tall. The 76.2 mm width (3 inches) matches the standard 3-pole MCCB footprint for DIN-rail or panel-mount installation. Maximum power dissipation is 12 W — check the enclosure's thermal budget if the breaker is in a sealed, uncooled cabinet with other heat sources.