The Schneider Electric A9K24720 is a 3P+N miniature circuit breaker from the Acti9 iK60N series, rated 20 A at 30 °C with a C-curve trip characteristic. It breaks 6000 A at 400 V AC (Icn per EN/IEC 60898-1), which covers most residential and light commercial distribution panels — the 6 kA rating is the standard for final subcircuits in a TN or TT system where the prospective fault current at the board is under that level.
The 3P+N form factor takes 8 x 9 mm pitches of rail space — 72 mm wide. Neutral is on the left, which matters when laying out a distribution board with busbar links that expect that order. Tunnel terminals accept 1 to 25 mm² rigid or 1 to 16 mm² flexible; tighten to 2 N·m. Strip 14 mm of insulation.
Thermal-magnetic trip unit. The magnetic trip threshold is 5 to 10 times the rated current (100 to 200 A), which is the standard C-curve window — fast enough for moderate inrush from small motors or transformers, but selective enough to ride out the brief startup of a lighting bank or a few contactor coils. Rated insulation voltage is 440 V AC.