Schneider ComPact NSX MCCB: Full Range Review and Specifications

What is the Schneider ComPact NSX MCCB range? ComPact NSX is Schneider Electric's molded case circuit breaker family, spanning roughly 15 A to 630 A across five frame sizes — NSX100, NSX160, NSX250, NSX400, and NSX630 — built around one defining feature: field-swappable trip units, so the same breaker body accepts a thermal-magnetic TM-D/TM-G module or a Micrologic electronic module (2, 5, 6, or 7) without replacing the breaker itself. That single design choice changes how panel builders spec spares, and how a maintenance team handles a protection upgrade years after commissioning. This review covers frame sizing across the range, trip unit options and what each enables, breaking capacity classes from B(25 kA) to L(150 kA) at 415 V, the Vigi earth-leakage add-on, and where ComPact NSX sits against Schneider's EasyPact CVS and GoPact economy lines.

ComPact NSX Frame Architecture: One Family, Five Ratings

NSX100, NSX160, and NSX250 share a frame family — same mechanical footprint, same accessory slots, different current taps. NSX400 and NSX630 step up to a larger frame. That distinction matters at the panel design stage: a busbar layout built around the smaller frame family accepts NSX100, 160, or 250 interchangeably as load current is finalized late in the project, without redesigning the compartment. The larger frames don't share that footprint, so a 400 A or 630 A feeder has to be decided earlier.

Current coverage runs from around 15 A up through 630 A across the five frames, giving one product family for everything from a small distribution feeder to a main incomer on a mid-size panel. Above 630 A, Schneider moves to the ComPact NS or Masterpact air circuit breaker lines — a different mechanism class, not a bigger NSX.

Trip Units: TM-D/TM-G Thermal-Magnetic vs Micrologic Electronic

Every NSX frame up to 250 A can take a TM-D or TM-G thermal-magnetic trip unit — fixed thermal overload, adjustable magnetic instantaneous trip, no electronics, no auxiliary power needed. Simple. Cheap to stock. Fine for a feeder that doesn't need selective coordination or metering.

Above 250 A, thermal-magnetic isn't offered; NSX400 and NSX630 run on Micrologic electronic trip units only. Micrologic 2 gives long-time and instantaneous protection (LI). Micrologic 5 adds short-time protection for coordination (LSI). Micrologic 6 adds ground-fault protection (LSIG). Micrologic 7 adds earth-leakage sensitivity for personnel protection, not just equipment protection. An "E" suffix on any of these adds energy metering — kWh, demand, power factor — read locally or pulled over Modbus.

The trip unit is a plug-in module on a common electrical and mechanical interface across the frame. That's the field-swappable part: a breaker commissioned with Micrologic 5 (LSI) can be upgraded to Micrologic 6 (LSIG) later, when a ground-fault study calls for it, without pulling the breaker body out of the panel.

Breaking Capacity Classes: Reading B/F/N/H/S/L Correctly

ComPact NSX breaking capacity is marked by a letter class: B(25 kA), F(36 kA), N(50 kA), H(70 kA), S(100 kA), L(150 kA) at 415 V, ascending. The letter on the nameplate is the fast way to check whether a breaker clears the available fault current at its installation point — no need to cross-reference a separate table if the switchboard's short-circuit study already states the required kA.

What the letter doesn't tell you directly is the service breaking capacity. Icu (ultimate breaking capacity) is the number on the class label. Ics (service breaking capacity) is what the breaker is rated to clear and remain usable afterward, and it's expressed as a percentage of Icu that Schneider declares per class. On some ComPact NSX classes that ratio runs at 50-75% of Icu rather than the 100% some competing brands use on their top classes. Size the installation around Ics, not the class-label Icu — a breaker that survives one fault at its Icu rating but can't be trusted afterward isn't protecting anything on the second fault.

This is not unique to any one brand — see our breaking capacity rating explainer for how Icu, Ics, and Icw interact across manufacturers. Icw (short-time withstand) mostly applies to air circuit breakers, not molded case — NSX breakers generally carry limited or no Icw rating, which is one reason MCCBs sit downstream of ACBs in a selective coordination scheme rather than upstream.

ComPact NSX Range at a Glance

The table below summarizes current coverage, trip unit options, and typical breaking class span by frame. Exact class availability at a given current tap depends on the specific catalog reference and voltage — check the selected reference against the project's short-circuit study before ordering.

Notice the pattern: thermal-magnetic disappears once the frame passes 250 A, and the breaking class ceiling generally trends down as the frame gets physically bigger. That's a mechanical reality across most MCCB brands, not a Schneider-specific limitation — see the MCCB voltage, current, and frame size guide for how the same trend plays out on Tmax XT and Sentron 3VA.

Vigi Add-On: Turning Any NSX Into an Earth-Leakage Breaker

Vigi is a bolt-on residual current module that mounts to the base of an NSX breaker and adds earth-leakage detection independent of the trip unit's own ground-fault function. It's the practical route to residual current protection (RCD/GFCI-class sensitivity) on a breaker that would otherwise only trip on overcurrent and short circuit.

Where this matters in practice: a Micrologic 2 (LI-only) breaker with no ground-fault curve of its own still gets earth-leakage protection if a Vigi module is specified — useful on a feeder where the budget doesn't justify Micrologic 6, but code or insurance still requires residual current protection at that point. What we see in the field is Vigi specified more often on final distribution feeders than on incomers, where a Micrologic 6/7's built-in LSIG usually covers the requirement without the extra module.

Where ComPact NSX Sits Against EasyPact CVS and GoPact

Schneider doesn't sell ComPact NSX as the only MCCB option. EasyPact CVS is the economy tier, covering a similar current span up to 630 A but without the same depth of Micrologic trip options or the field-swap flexibility that defines NSX. GoPact is a newer economy line positioned the same way — lower cost, simpler spec, aimed at projects where breaking class headroom and trip unit upgrade paths aren't a requirement.

The practical selection question isn't "which is cheaper" — it's whether the installation is likely to need a protection upgrade later, or whether the fault current at that point in the switchboard already sits close to the economy tier's ceiling. Most panels stocking molded case circuit breakers for export projects keep NSX as the default for exactly this reason: the upgrade path stays open after the panel ships. If either is uncertain, NSX's field-swappable Micrologic modules and wider class span buy flexibility that's expensive to add after the fact. If the load and fault level are well known and fixed, EasyPact CVS or GoPact removes cost without removing protection margin.

Field Swaps: What You Can Change After Installation, What You Can't

Trip unit: swappable, within the frame's Micrologic family, no breaker replacement. Vigi module: addable after the fact on frames that support it, since it mounts externally to the breaker body. Breaking class and frame size: fixed at manufacture — the class is tied to the breaker's internal arc chamber and contact design, cast into that specific reference, not something a module change alters.

This depends on duty cycle in one respect worth flagging: a trip unit swapped from TM-D to Micrologic on a breaker that's already seen years of switching cycles is a valid upgrade, but it doesn't reset the mechanical wear on the breaker body itself. Some engineers treat a trip unit upgrade as equivalent to a new breaker; in practice it isn't — the interrupting mechanism and contacts are the same ones that were already in service.

For a structured approach to matching frame, trip unit, and breaking class to a specific feeder or motor load, see our MCCB selection checklist, and for the underlying reasoning on how thermal-magnetic and electronic trips compare across brands, the MCCB engineering guide covers the fundamentals this review assumes.

Conclusion

ComPact NSX earns its position as Schneider's mainstream MCCB range through one mechanical decision: the trip unit is a swappable module, not a fixed part of the breaker. That buys flexibility on protection curve and metering that fixed-trip economy lines like EasyPact CVS and GoPact don't offer. It doesn't change the physics of breaking capacity — class letters and their Icu/Ics split still have to match the fault current study at the installation point, and that check doesn't get easier just because the trip unit is upgradable. Match frame and current to the load, match breaking class to the fault study, and treat the trip unit choice as the one decision you can still revisit after the panel ships.