What this MCCB does on the line
The Siemens SENTRON 3VA1120-4EF36-0AF0 is a 3-pole molded case circuit breaker (MCCB) rated for line protection — meaning it sits at the feeder or branch point to protect cable and bus against overload and short circuit, not as a motor-protective device with integrated overload relay. Continuous current rating holds at 20 A from 40 °C through 55 °C ambient, then derates to 19 A at 60 °C and 65 °C — useful if the breaker lives in a warm enclosure or next to other heat sources. Interrupting capacity reaches 121 kA at 240 V, dropping to 75.6 kA at 415 V, 52.5 kA at 440 V, and 11.9 kA at 500 V and 690 V — the 121 kA figure at 240 V means it can clear a high-fault utility transformer secondary without upstream fuses, but at 480/500 V systems the available fault current must stay under 11.9 kA.
Thermal-magnetic release and internal configuration
Fitted with a TM240 thermal-magnetic overcurrent release — the thermal element handles overloads (inverse-time), the magnetic element handles short circuits (instantaneous). The '240' designator typically refers to the frame size or release rating; the breaker ships with a 1 auxiliary switch + 1 trip alarm switch (HQ type) pre-installed, so you get a remote status contact and a separate alarm contact for trip indication without adding a module. Trip indicator present on the front face — a visual flag or window shows whether the breaker tripped on fault versus being manually switched off, which speeds fault isolation on a panel walk-down. No undervoltage release, no ground-fault monitoring, no communication function built in — this is a straight thermal-magnetic line-protection breaker. If you need UVR, GFCI, or Modbus, you add external accessories or step to a 3VA2 electronic-trip variant.
Panel fit and environmental limits
Operating temperature range -25 °C to +70 °C; storage range -40 °C to +80 °C. Maximum power dissipation 12 W — account for that heat in a sealed enclosure with multiple breakers ganged together. Rated insulation voltage 800 V — the breaker's internal creepage and clearance are designed for 800 V systems, so it can be used on 690 V line-to-line circuits with margin.