What it is and what it does
The Siemens 3VA1020-4ED36-0JH0 is a SENTRON molded case circuit breaker (MCCB) designed for line protection — the workhorse of a distribution panel, sized to protect a feeder or a branch circuit from overloads and short circuits. It carries a 20 A rating across the 40 °C to 55 °C ambient range, and derates to 19 A at 60 °C and above. That steady thermal curve means you can spec it into a warm panel without recalculating at every degree. Breaking capacity is the headline number that decides whether this breaker clears a fault without welding its contacts. At 240 V it interrupts 121 kA, at 415 V it handles 75.6 kA, and at 690 V it still manages 11.9 kA. That kind of headroom means it slots into high-fault panels — think industrial switchgear near a large transformer — without needing a current-limiting fuse upstream.
Panel fit and integration
Three-pole design, 76.2 mm wide, 130 mm tall, 70 mm deep. That 3-inch width is a standard MCCB footprint — it occupies one 3-pole position on a DIN rail or bolts directly to a mounting plate. The 12 W max power loss at full load is manageable; no forced cooling needed in a ventilated enclosure, but if you're stacking multiple breakers in a sealed box, factor that into the thermal calcs. Comes with two auxiliary switches and one trip alarm switch (HQ type), plus a shunt trip (STL) for remote tripping. That's enough for status feedback to a PLC and an emergency-off circuit — no separate contactor block needed for basic signalling.