What this trip unit does and why it matters
The C4036M320 is a MicroLogic 6.3 E-M electronic trip unit for the ComPacT NSX400...630 molded-case circuit breaker family. It's rated 320 A at 65 °C and provides LSIG protection — long-time (L), short-time (S), instantaneous (I), and ground-fault (G) — specifically tuned for motor loads. The E-M designation means it includes complementary motor protection functions like protracted starting time, current unbalance, underload, and stalled rotor protection, with selectable trip classes 5, 10, 20, or 30. That trip class selection lets you match the thermal curve to the motor's starting profile — a pump with a long start-up time needs class 20 or 30 to avoid nuisance tripping during acceleration.
Protection and metering in one unit
This trip unit isn't just a protective relay — it's also an energy meter. The LCD display shows instantaneous and demand values, power quality data, and time-stamped event logs. Zone selective interlocking (ZSI) is built in, which lets multiple breakers in a cascade coordinate their short-time trip delays — the breaker closest to the fault clears first, while upstream breakers hold off, keeping the rest of the line live.
The trip unit snaps into a fixed-mount ComPacT NSX breaker. The breaker itself occupies a standard DIN-rail footprint, though the NSX frame is bolted, not DIN-clipped. The IP40 front-of-panel protection means it's fine for a clean indoor enclosure, but keep it away from washdown zones. The 3D protected poles description means all three poles are monitored for ground fault, not just one.