What this 20 A MCCB covers on the line
The Siemens 3VA1120-4GE42-0AA0 is a SENTRON molded case circuit breaker (MCCB) rated for 20 A continuous at 40 °C, with a 4-pole configuration and a TM220 thermal-magnetic release. Its headline breaking capacity hits 121 kA at 240 V — that is the figure that governs fault clearing in a low-voltage distribution panel where the available fault current is high. The 4-pole design means it switches all three phases plus neutral, with 100% N-conductor protection built in, which is what you need for a 3-phase + N feed where you cannot tolerate an unprotected neutral.
Breaking capacity across voltage taps — what the numbers mean
The 3VA1120-4GE42-0AA0 carries multiple interrupting ratings because the same arc-extinction chamber performs differently as system voltage rises. At 240 V it clears 121 kA; at 415 V it is still 75.6 kA; at 500 V and 690 V it drops to 11.9 kA. For a 480 V panel in North America the 75.6 kA at 415 V is the closest reference — that is well above typical 480 V SCCR requirements for most industrial switchboards. The 11.9 kA at 690 V is the limiting case: if your system runs 600 V class, this breaker still holds a useful 11.9 kA, enough for most motor control centers but not for high-fault utility feeds at that voltage.
Thermal derating and panel environment
Rated 20 A from 40 °C up to 55 °C, then derates to 19 A at 60–70 °C. That flat 20 A band through 55 °C is useful — many MCCBs start derating at 40 °C, so this one gives you full rating in a warm enclosure. Operating range is -25 °C to 70 °C; storage from -40 °C to 80 °C. The IP40 on the front means it is protected against solid objects over 1 mm but not sealed against moisture — standard for a panel-mounted breaker, but not for washdown areas.
Panel fit and mounting
Dimensions: 130 mm height, 101.6 mm width, 70 mm depth. The 70 mm depth is the dimension that matters for enclosure depth clearance — standard 200 mm deep enclosures have plenty of room. Width of 101.6 mm (4 inches) fits a standard 4-module MCCB footprint on a DIN rail or mounting plate. The optional motor drive accessory (listed as available) means you can add remote trip or reset without changing the breaker frame.
What the TM220 release does
The TM220 designation means a thermal-magnetic release with a fixed thermal pickup at 20 A and a magnetic short-circuit pickup set at 20x In (400 A). That is a standard distribution profile — the magnetic trip is high enough to avoid nuisance tripping on motor inrush or capacitor bank charging, but still fast on a bolted fault. No ground-fault monitoring built in; if you need GF protection, you add an external module or specify the GF variant.