What it is and what it does
The Siemens 3VA1120-3EF36-0HC0 is a SENTRON molded case circuit breaker (MCCB) designed for line protection in industrial distribution panels. Three poles, rated 20 A continuous at 40 °C, with a breaking capacity of 75.6 kA at 240 V AC — that's the short-circuit current it can safely interrupt without welding or rupturing. The 800 V rated insulation voltage gives headroom for 480 V and 600 V systems.
Key ratings and what they mean for fit
Rated current holds at 20 A from 40 °C up to 50 °C, then derates to 19 A at 60–70 °C (–). That means in a warm panel (say 55 °C ambient), the breaker still carries the full 20 A — no need to oversize. Breaking capacity steps down with voltage: 75.6 kA at 240 V, 52.5 kA at 415 V, 32 kA at 440 V, 11.9 kA at 500 V and 690 V (–). For a 480 V system, the 32 kA at 440 V is the closest published point; the actual SCCR at 480 V will be between 32 kA and 11.9 kA — coordination study needed if fault current approaches that range. The breaker ships with a shunt trip release (STL) and two HQ auxiliary switches. The shunt trip allows remote tripping from a PLC or emergency-stop circuit; the HQ aux switches provide status feedback (open/closed/tripped) to a control system. No undervoltage release or ground-fault module on this variant. Maximum power loss is 12 W — negligible for panel thermal budgeting, but worth noting if the breaker is in a sealed enclosure with other heat sources.
Integration notes
Mounts on a standard DIN rail or panel-mount plate. Dimensions: 130 mm height, 76.2 mm width, 70 mm depth (–). The 3-pole footprint matches the SENTRON 3VA family — if you're replacing a 3VA1110-5ED36-0AC0, the width and depth are identical; the height is the same 130 mm. No rewiring needed for the line and load lugs, but verify the shunt trip wiring and aux contact assignment against the existing panel schematic.