The Siemens 3VA1120-6EF32-0JC0 is a SENTRON molded case circuit breaker (MCCB) rated for line protection in industrial distribution panels. It carries a continuous current of 20 A at 40 °C through three poles, with an insulation voltage of 800 V — suitable for 480Y/277 V and 600 V delta systems where the breaker's voltage class exceeds the line-to-line potential.
Breaking capacity and selectivity
The interrupting rating at 240 V is 220 kA, dropping to 154 kA at 415 V and 121 kA at 440 V. At 500 V and 690 V the rating holds at 17 kA. These figures let the breaker clear high-fault currents on the secondary side of a large transformer without upstream devices needing to open — useful for maintaining selectivity in a multi-level distribution scheme.
Thermal performance and derating
The breaker holds 20 A continuously from 40 °C up to 55 °C. At 60 °C and 65 °C it derates to 19 A, and at 70 °C it stays at 19 A. The maximum power loss is 12 W. If the breaker lives in a warm enclosure — say, near a curing press or drive cabinet — the 19 A ceiling at 60 °C is the number to size against, not the 20 A nameplate.
Integrated accessories
This variant ships with a shunt trip (STL) for remote opening and two auxiliary switches (HQ) for status feedback to a PLC or annunciator. There is no undervoltage release, no ground-fault monitoring, and no communication module. The auxiliary switches are pre-installed; no field-assembly of add-on blocks is needed.