What this MCCB delivers on the panel
The Siemens SENTRON 3VA1120-3EF36-0AG0 is a 3-pole molded case circuit breaker rated for 20 A continuous current with a TM240 thermal-magnetic release. It is configured for line protection — no undervoltage release, no ground fault monitoring, no communication module. The front face carries a trip indicator and one auxiliary switch plus one trip alarm switch, which is the standard complement for remote status feedback on a feeder breaker. Breaking capacity is the headline spec here: 75.6 kA at 240 V, 52.5 kA at 415 V, 32 kA at 440 V, and 10.5 kA at 690 V. That 75.6 kA at 240 V means this breaker handles high available fault current on a 240 V distribution bus — typical for North American commercial/light industrial panels where the transformer is close. The 52.5 kA at 415 V covers European 400 V three-phase networks. At 690 V the 10.5 kA figure is lower but still adequate for most motor control center applications where the upstream transformer limits fault current. Temperature derating is published across the full operating range: full 20 A rating holds through 50 °C, then drops to 19.2 A at 55 °C, 18.8 A at 60 °C, 18.4 A at 65 °C, and 18 A at 70 °C. That 18 A at 70 °C is the number to use if the breaker sits in a hot enclosure near other heat sources — the 20 A nameplate is only valid below 50 °C ambient.
Mounting and integration
Dimensions are 130 mm height, 76.2 mm width, 70 mm depth. The 76.2 mm width is a standard 3-pole MCCB footprint — it fits the same DIN-rail or panel-mount cutout as other 3VA frame-size breakers. The 70 mm depth is shallow enough to clear most standard enclosure back-panels without a spacer. Front protection is IP40 — dust-protected but not sealed. Suitable for indoor panel mounting where no washdown or condensation is expected. The IP40 rating applies to the front face only; the rear terminals are not covered by that rating and require the enclosure's own IP protection. Rated insulation voltage is 800 V, which covers 690 V systems with margin. The latching endurance is 15,000 operations — that is the mechanical life before the latch mechanism wears. For a breaker that cycles infrequently (a few times a year for maintenance isolation), that is effectively a lifetime rating. For a breaker used as a daily disconnect, it is a finite count to track.
Selectivity and coordination notes
The TM240 release is a fixed thermal-magnetic trip — no electronic adjustment, no zone-selective interlocking. That means selectivity with downstream breakers depends on the natural time-current curve separation. For a simple radial feeder, it works fine. For a complex distribution with multiple levels of coordination, an electronic-trip 3VA variant (with adjustable I²t and short-time delay) would give more headroom. The auxiliary switch and trip alarm switch (1 each) are built in. The auxiliary switch follows the main contacts (open when breaker is open, closed when breaker is closed). The trip alarm switch changes state only on a fault trip — it stays in its normal position when the breaker is manually opened. That distinction matters for the PLC logic: use the trip alarm for a fault annunciation, not the auxiliary switch.