What it is — and what the ratings mean for your panel
The Siemens 3VA1220-5GF42-0AG0 is a SENTRON molded case circuit breaker (MCCB) built for line protection in distribution panels. It's a 4-pole, 200 A frame with a TM240 thermal-magnetic release — the 'TM' means it uses a bimetal strip for overloads and a solenoid for short-circuits, no electronics, so it's field-reliable and doesn't need auxiliary power. The interrupting ratings tell you where it fits: 187 kA at 240 V, 121 kA at 415 V, 75.6 kA at 440 V, 30 kA at 500 V, and 17 kA at 690 V. That 187 kA at 240 V is a high-interrupting-capacity (HIC) class — it handles faults from large transformers or utility feeds without needing an upstream current-limiting fuse. The thermal derating curve is honest: 200 A continuous from 40 °C through 50 °C, then it tapers — 194 A at 55 °C, 188 A at 60 °C, 182 A at 65 °C, 176 A at 70 °C. If your panel ambient runs above 50 °C, you don't get the full 200 A; size the downstream load against the temperature-corrected value, not the frame rating. The 70 mm depth (2.76 in), 140 mm width (5.51 in), and 158 mm height (6.22 in) fit a standard MCCB footprint on DIN rail or direct-mount plate — measure your enclosure depth before ordering, especially if there's a gland plate or wiring duct behind it.
Panel integration and wiring
The internal basic switch is order code 3VA12205GF420AA0 — that's the sub-assembly that actually carries the current and trips. The main breaker frame is the enclosure and mechanism; the switch is the replaceable insert. If you ever need to swap the internal switch without pulling the whole breaker, that's the part number to order alongside this one.