BaseUnit for ET 200SP — BU20-P6+A2+4D
The Siemens 6ES7193-6BP20-0DC0 is a SIMATIC ET 200SP BaseUnit, type BU20-P6+A2+4D (BU type C0), with push-in terminals and two AUX terminals for creating a new load group. It provides the mechanical and electrical interface between the I/O module and the backplane bus, carrying up to 10 A on the / bus and the AUX bus at 230 V. The 20 mm width and 117 mm height fit the standard ET 200SP mounting rail footprint.
What the Ratings Mean for Fit
The 10 A rating on the / bus and AUX bus (up to 60 °C horizontal installation) sets the maximum current the BaseUnit can carry to downstream modules — size your load group so the sum of module currents stays under this limit. The process terminals are rated 5 A, with terminals 5 and 6 handling 10 A, which matters when you are feeding higher-current actuators or sensors through those specific positions. Push-in terminals accept 0.14 mm² to 2.5 mm² (AWG 26 to 14) solid or ferruled stranded wire — a standard range for control wiring, so no special termination tooling is needed beyond a push-in screwdriver. The 35 mm depth keeps the unit within the standard ET 200SP envelope, leaving room for wiring ducts in the cabinet. Automatic encoding (FS10 and higher) means the BaseUnit reads the module's electronic ID and routes the backplane signals correctly — no manual DIP-switch setting for slot addressing. This reduces commissioning errors when swapping modules. Isolation tested at 3 100 V DC between the backplane bus and supply voltage, and between process terminals and supply voltage, confirms galvanic separation for the 230 V AUX bus — important for maintaining a clean control ground and avoiding ground loops in mixed-voltage cabinets.
Where It Fits in the System
This BaseUnit is designed for the SIMATIC ET 200SP distributed I/O system, mounting on a DIN rail in a control cabinet or junction box. It creates a new load group, meaning the AUX bus is fed from a separate 230 V supply, isolated from the / bus — useful when you need to group modules by power zone or safety circuit. The optional system-integrated shield connection lets you terminate cable shields directly at the BaseUnit, saving a separate grounding terminal block. External protection is required: a 10 A miniature circuit breaker with type B or C tripping characteristic on the supply lines. This is not optional — the BaseUnit has no internal overcurrent protection, so the breaker is the sole short-circuit and overload safeguard for the load group. Rated for horizontal installation from -30 °C to 60 °C, and vertical from -30 °C to 50 °C. If your cabinet orientation or airflow differs, derate accordingly. Installation altitude up to 2 000 m standard; higher altitudes available on request.