What this MCCB is and where it fits
The Siemens 3VA1220-5MH32-0AD0 is a 3-pole SENTRON molded case circuit breaker (MCCB) rated for 200 A continuous, with a TM120M thermal-magnetic overcurrent release. It's built for starter protection duty — meaning it's sized to sit ahead of a motor starter combination, handling both overload and short-circuit fault clearing in one package. The interrupting capacity hits 187 kA at 240 V, 121 kA at 415 V, and still delivers 75.6 kA at 440 V, so it's comfortable on high-fault industrial distribution panels where the available short-circuit current is substantial. Rated insulation voltage is 800 V, which covers 480/600 V class systems with headroom.
Thermal derating — the real continuous current
At 40 °C, 45 °C, and 50 °C this breaker holds its full 200 A rating. At 55 °C it derates to 194 A, at 60 °C to 188 A, at 65 °C to 182 A, and at 70 °C to 176 A. If the panel ambient runs hot — say inside a non-conditioned enclosure near a furnace line — the 70 °C figure is the one to size against. The maximum power loss is 42 W, which matters for internal enclosure heat rise calculations.
Physical fit and internal build
Dimensions are 105 mm wide, 158 mm high, 70 mm deep. That's a 4.13 x 6.22 x 2.76 inch footprint — standard for a 200 A frame MCCB. It mounts on a DIN rail or directly to a backplate. Inside, the basic switch is a 3VA12205MH320AA0, and the auxiliary switch configuration is three HQ-style aux switches. No undervoltage release, no ground-fault monitoring, no communication module — this is a straight thermal-magnetic breaker with aux contacts for status feedback.