MCB Selectivity / Discrimination Checker
Pick two Schneider Acti9 MCBs in series and get an indicative selectivity verdict — whether a downstream fault is likely to trip only the local device, and up to roughly what fault level. A first-pass sanity check, not a manufacturer discrimination study.
Generic indicative check — a real discrimination study needs Schneider's tested selectivity tables and time/current curves.
This checker uses a generic trip-band method (a downstream fault below the upstream device's magnetic-trip threshold is cleared by the downstream device alone). It is a feasibility aid only. MCB-to-MCB pairs rarely achieve full selectivity without a manufacturer-tested table, so every device pair must be confirmed against Schneider's published selectivity data and time/current curves before it is relied upon.
Why Discrimination Matters
When a fault occurs on a final circuit, only that circuit's device should trip — not the board's incomer, which would black out everything downstream. That is discrimination (selectivity). For MCBs it depends on the trip curves, the rating ratio and the fault level, and full selectivity usually needs the manufacturer's tested tables. This tool gives the quick indication; the audited discrimination study — with real time/current curves and fault levels at each point — is our ProDesign protection coordination service. Read more: discrimination & selectivity explained.