What the COM800 does on a 3VA panel
The Siemens 3VA9977-0TA10 is the SENTRON COM800 breaker data server — a communication gateway that sits on the DIN rail inside a fixed switchboard and pulls data from up to eight 3VA circuit breakers via the electronic trip unit interface. It speaks PROFINET IO and PROFIBUS DP simultaneously, plus a Modbus RTU serial gateway on the Ethernet port, so the panel can report breaker status (on, off, tripped), current draw, and power metrics to a PLC or SCADA without separate protocol converters. The 100 Mbit/s Fast Ethernet interface uses an RJ45 connector with auto-MDI(X) for straight or crossover cables, and supports up to five active connections.
Mounting and integration constraints
The module occupies 5 modular width units on the DIN rail — 90 mm wide, 90 mm tall, 33.5 mm deep — and can be mounted in any orientation. Power comes from a 24 VDC supply via screw terminals; the unit draws 1.1 A max and dissipates 5 W. It also supplies the electronic trip units on connected breakers, so the control transformer needs to cover that additional load. The total daisy-chain length between breakers is limited to 20 m, with two bus termination connectors included. IP20 rating means it is for enclosed panels only — no washdown exposure.