Siemens 3VA1225-4EF42-0AD0 — 250 A SENTRON MCCB
The Siemens 3VA1225-4EF42-0AD0 is a 4-pole SENTRON molded case circuit breaker rated for 250 A continuous current at 40 °C ambient, with a TM240 thermal-magnetic overcurrent release. Its interrupting capacity reaches 121 kA at 240 VAC — enough for high-fault utility feeds or large transformer secondaries. The 800 V rated insulation voltage (Ui) covers most 480/277 V and 600 V industrial distribution panels without derating the basic insulation level. This is a line-protection version (no undervoltage release, no ground-fault monitoring, no communication module) — a clean main breaker for a switchboard or a feeder tap. The 3 auxiliary switches (HQ type) provide status feedback to a PLC or SCADA without a separate contactor block.
Breaking capacity across voltages
The interrupting rating drops sharply as line voltage rises: 121 kA at 240 V, 75.6 kA at 415 V, 52.5 kA at 440 V, 17 kA at 500 V, and 11.9 kA at 690 V. For a 480 V panel the relevant figure is the 440 V or 500 V column — 52.5 kA or 17 kA respectively — which still exceeds typical 480 V fault levels (usually 10–65 kA) for most commercial-industrial installations. At 690 V the 11.9 kA rating limits this breaker to low-fault motor control centers or downstream sub-distribution.
Thermal derating and ambient limits
The 250 A rating holds flat from 40 °C through 50 °C — no derating needed in a typical 40 °C switchboard. Above 50 °C it steps down: 243 A at 55 °C, 237 A at 60 °C, 230 A at 65 °C, and 223 A at 70 °C. If the breaker sits in a non-ventilated enclosure near transformers or drives, the 70 °C ambient case drops the usable current by about 11 % from the nameplate. Operating range spans −25 °C to +70 °C; storage from −40 °C to +80 °C.
Physical fit and panel integration
Dimensions: 140 mm wide × 158 mm tall × 70 mm deep. The 70 mm depth (2.76 in) means it clears most 200–300 mm deep enclosures with room for rear-mounted busbars or cable ladders. The 4-pole body occupies 140 mm of DIN-rail or mounting-plate width — plan for a 175 mm minimum bay width to allow finger space for lug torqueing. The HQ auxiliary switch block adds roughly 18 mm to the side, so account for that in the wiring gutter.