What this MCCB is and what it does
The Siemens 3VA1120-5ED26-0AA0 is a SENTRON molded case circuit breaker (MCCB) designed for line protection in distribution panels. It's a 2-pole unit rated 20 A continuous at 40 °C, with a TM210 thermal-magnetic release that handles overloads and short circuits without external trip electronics. The 187 kA interrupting rating at 240 V AC and 121 kA at 415 V AC means it can safely clear high-fault currents in industrial mains — useful where the available fault current is substantial and selectivity with downstream breakers matters.
Key ratings and what they mean for fit
Rated current holds at 20 A from 40 °C through 55 °C, then derates to 19 A at 60 °C through 70 °C — no derating needed in most ventilated enclosures, but worth checking if the breaker sits in a hot compartment near other heat sources. The TM210 release is a fixed thermal-magnetic type; no interchangeable trip units, so the 20 A rating is baked in. Breaking capacity of 187 kA at 240 V AC covers high-capacity transformer secondaries and large motor control centers; the 121 kA at 415 V AC still handles most 400 V industrial feeds. Insulation voltage rated 500 V, operating voltage up to 415 V AC or 250 V DC. Power loss max 8 W — modest for a 20 A MCCB, helps with enclosure thermal budgeting.
Panel integration and physical fit
Mounts on a DIN rail or panel-mount base. Dimensions: 70 mm deep, 50.8 mm wide (2 inches), 130 mm high. The 2-pole width is standard for a 2-pole MCCB — fits a 2-module space in most distribution boards. IP40 on the front means protection against tools and wires >1 mm, but not against water ingress; suitable for indoor panel installation, not washdown areas. No undervoltage release, no ground-fault monitoring, no communication function — this is a plain line-protection breaker with no auxiliary electronics.