The Schneider Electric A9SCO140 is a 1-pole changeover switch from the Acti9 iSSW series, rated 40 A operational current at 230/240 V AC. It's built for switching between two supply sources — mains and generator, or utility and backup — in a single-phase panel. The 40 A rating covers most residential and light commercial service-entrance or sub-feed changeovers, with the AC-23A utilisation category meaning it handles motor loads (up to 5 kW at 240 V) and AC-22A covers mixed resistive-inductive loads (up to 7.7 kW at 240 V).
The 690 V rated insulation voltage (Ui) gives headroom above the 230/240 V operating voltage, and the 6 kV impulse withstand (Uimp) means it survives surge events typical in residential and commercial AC mains without flashover. Short-time withstand current (Icw) is 0.8 kA for 1 second at 230/240 V, with a peak making capacity (Icm) of 0.8 kA. That's the fault current the switch can close onto and hold for one cycle — adequate for a 40 A service fed by a typical 63 A or 80 A upstream breaker on a 10 kA prospective fault level. For higher fault-current installations, verify the upstream protective device limits let-through energy below this rating. The toggle has three positions (ON-OFF-ON) with a padlockable ON position, and the contact position indicator gives visual confirmation of the active source.
Snaps onto 35 mm DIN rail, occupies 2 x 9 mm pitches (17.5 mm width). Screw terminals accept 1–16 mm² rigid or 1–10 mm² flexible wire; strip length 12 mm, tighten to 2.5 N·m. Mount vertically or in any position, but the -25°C to +60°C operating range applies — outside that, the mechanical durability of 10,000 cycles and electrical durability of 7,000 cycles may derate.