: According to PUE section 3.1.6 , supply wires should ideally be connected to the static (stationary) contacts , which are almost always at the top of the breaker.
: High-quality brands like ABB or Legrand may allow input from either side, but keeping a consistent "top-in, bottom-out" pattern across the panel is crucial for safety and easier troubleshooting. 2. Linking Multiple Breakers shema soedinenija avtomatov
While many modern breakers are universal, standard practice and regulations often dictate where the "supply" wire should be connected. : According to PUE section 3
: Pin-type (universal pole structure) and Fork-type (U-shaped for screw terminals). : According to PUE section 3.1.6
: Hand-made bridges using insulated wire.