Rated current and interrupting capacity — what the numbers mean for your panel
The Siemens SENTRON 3VA1120-3EF32-0HC0 is a 3-pole molded case circuit breaker rated 20 A continuous at 40 °C ambient, with no derating needed up to 55 °C — it holds 20 A through that band, then steps to 19 A at 60 °C and 70 °C. That means in a typical 40 °C panel environment you get the full 20 A; only above 55 °C do you lose 1 A. The interrupting ratings step with system voltage: 75.6 kA at 240 V, 52.5 kA at 415 V, 32 kA at 440 V, and 11.9 kA at both 500 V and 690 V. For a 480 V distribution panel, the 32 kA at 440 V is the closest published point — the 11.9 kA at 500 V is conservative for 480 V systems. The rated insulation voltage is 800 V, so the breaker is built for 690 V line-to-line applications without additional creepage concern. This is a line-protection design, not a motor-protection or generator-protection variant — the thermal-magnetic trip curve is set for feeder and distribution duty. It ships with a shunt trip release (STL) and two HQ auxiliary switches integrated, so remote tripping and status feedback are built in without an external accessory module.
Dimensions and panel fit
The breaker measures 130 mm high, 76.2 mm wide, and 70 mm deep. That 70 mm depth is the body only — no allowance for the handle throw or rear terminals. In a standard 600 mm deep enclosure, you have clearance for wiring gutters and the shunt trip leads. The 76.2 mm width (3 inches) is a standard 3-pole MCCB footprint; it occupies one 3-pole position on a DIN rail or panel-mount base.
Power loss and thermal management
Maximum power loss is 12 W at rated current. In a densely packed panel, that 12 W per breaker adds up — if you have ten of these in a row, you're looking at 120 W of heat to evacuate. The operating temperature range is -25 °C to 70 °C; storage range is -40 °C to 80 °C. The storage minimum is the handling limit, not the running limit.