This is not a general-purpose feeder breaker; its coordination curve is tailored for motor starting inrush, so it holds during start and trips on a sustained fault. The 45 mm width (three 18 mm modules) keeps the footprint tight on a DIN rail — useful when you're packing multiple motor starters into a single enclosure.
The 97 mm depth means it protrudes about 10 mm beyond a standard 80 mm deep enclosure backplate — check your gland plate depth before committing.
The 3RV2321-4CC20 delivers 55 kA at 400 V AC and 25 kA at 400 V — the higher figure is the ultimate breaking capacity (Icu), the lower is the service breaking capacity (Ics) at that voltage. At 690 V it still interrupts 2 kA, enough for most 690 V motor circuits. The gL/gG fuse backup ratings (63 A at 400 V, 50 A at 500/690 V) tell you what upstream fuse preserves the breaker's SCCR if fault current exceeds its standalone rating — useful when retrofitting into an existing panel with unknown available fault current.
Motor ratings and thermal environment
Motor full-load current ratings: 3 hp at 230 V, 7.5 hp at 200/208 V and 220/230 V, 15 hp at 460/480 V. The 480 V rating is 22 A, which aligns with a NEMA size 1 starter.