What this trip unit does on the line
The ENW21422 is the brains for an EasyPact NW air circuit breaker — the Trip System 2.0A control unit that decides when to hold and when to trip. It covers the 800 to 4000 A range at 690 V AC, with LI protection: overload (long-time) and instantaneous short-circuit. That means you get adjustable long-time pickup from 0.4 to 1 x In and instantaneous pickup from 1.5 to 10 x Ir, both with nine settings each. The long-time delay stretches from 0.5 to 24 seconds at 6 x Ir, so you can shape the curve for coordination downstream.
Field diagnostics that save a midnight call
This unit has a digital display and fault indication for short-circuit, internal fault, overload, and earth fault. It measures instantaneous current on all three phases plus neutral, 0.2 to 1.2 In with ±1.5% accuracy, and logs maximum current the same way. That means when a line drops, you walk up and read the last fault — no laptop needed.
Selectivity and coordination
Zone selective interlocking (ZSI) is built in. That lets multiple breakers in a cascade communicate during a fault — the downstream breaker clears the fault instantly without waiting for the upstream unit to time out, while a fault between breakers still gets full coordination. For standard industrial applications, this is what keeps a single feeder fault from taking out the whole switchboard. Neutral protection is configurable: 3D (no neutral protection), 3D + N/2 (half-rated neutral), or 4D (full neutral protection). Poles description covers 3P and 4P configurations.