What this part is and what it does
The Siemens 3VA1225-1AA42-0KH0 is a 4-pole switch disconnector built in an MCCB (moulded-case circuit breaker) form factor, part of the SENTRON family. It is rated for a continuous current Iu of 250 A and carries a maximum operational voltage of 690 V AC (50/60 Hz) or 600 V DC. The main circuit connects via busbar connection with front terminals, making it a direct panel-mount device for isolation and switching duty.
What the ratings mean for your panel
The 250 A continuous rating holds flat from 40 °C through 50 °C, then derates linearly to 223 A at 70 °C — a useful thermal budget for warm enclosures. The 800 V rated insulation voltage (Ui) gives headroom for 690 VAC line-to-line systems. The 4-pole configuration handles three-phase plus neutral isolation in a single unit. Maximum power loss is 57 W, so factor that into enclosure ventilation calculations. Front protection is IP40 — suitable for clean indoor panels, not washdown environments.
Auxiliary and release options
The unit ships with 2 auxiliary switches plus 1 trip alarm switch (HQ configuration), and includes a shunt trip release (STL) for remote tripping. No undervoltage release is fitted. A motor drive is available as an optional extension. The latching endurance is rated at 15,000 operations — a solid mechanical life for a disconnector in frequent-switching duty.
Physical fit and connection
Dimensions are 70 mm deep, 140 mm wide, and 158 mm high. The front-terminal busbar connection is standard for MCCB-style panel layouts. Verify busbar spacing and gland-plate clearance against your enclosure — the 140 mm width is wider than a typical 4-pole MCB, consistent with its 250 A rating.