Panel fit and mounting
The 5SY4403-8: It takes 4 modular width units on a DIN rail, 72 mm wide, 90 mm tall, 76 mm deep — the same footprint as other 4-pole SENTRON breakers. The quick assembly system clips onto the rail and accepts bottom and top combined terminals. Mounting in any position works, and the operating temperature range is -40 °C to 75 °C with humidity derating at the high end. Pollution degree 3 and overvoltage category III make it suitable for fixed industrial panels. Touch protection is built in; IP20 with connected conductors is the hands-off spec.
Lifecycle and sourcing
No direct second-source or replacement is needed at this stage. If you're stocking a critical spare, the standard SENTRON shell means the same accessory range (aux contacts, shunt trips, busbars) fits across the 5SY44 family.