Schneider ComPact NSX vs Siemens Sentron 3VA: Technical Comparison
Which MCCB range fits your panel: Schneider ComPact NSX or Siemens Sentron 3VA? ComPact NSX spans 15 A to 630 A across two frame families (NSX100/160/250 and NSX400/630), with field-swappable Micrologic trip units under IEC 60947-2. Sentron 3VA splits into a fixed thermal-magnetic 3VA1 line (frames 3VA10-3VA16, to roughly 630 A) and a separate electronic 3VA2 line reaching roughly 1000 A. That split changes spare-parts strategy, retrofit flexibility, and how far LSIG protection and metering scale on one frame. This comparison covers frame sizes and current ranges, breaking-capacity classes, Micrologic vs ETU trip units, modular-swap vs fixed-split architecture, metering options, and Icu/Ics sizing margins for both ranges.
Frame Sizes and Current Ranges: NSX vs 3VA
ComPact NSX is built on two physical frame families. NSX100/160/250 shares one case size from 15 A to 250 A; NSX400/630 is a larger case covering 320 A to 630 A. A panel builder who standardizes on the small NSX frame can cover four decades of current rating (100/160/250) without changing enclosure cutouts, then step up to the larger frame only above 250 A.
Sentron 3VA works differently. 3VA1 (thermal-magnetic, frames 3VA10 through 3VA16) tops out near 630 A, matching the thermal-magnetic ceiling on NSX. 3VA2 is a distinct electronic-trip line that extends to roughly 1000 A — there is no thermal-magnetic 3VA at that current level. If a project needs 800 A with a simple thermal-magnetic trip, Sentron cannot supply it; Schneider cannot either, since NSX400/630 above 630 A also moves to larger frame classes outside NSX. Above 630 A both vendors push you toward electronic trips regardless of brand.
Breaking Capacity Classes Compared
Schneider marks NSX breaking capacity with single letters: B (25 kA), F (36 kA), N (50 kA), H (70 kA), S (100 kA), L (150 kA) at 415 V. Siemens uses a similar letter-class system on 3VA (for example N, M), topping out near 150 kA at 415 V on the highest 3VA2 frames. At the top end the two ranges land in the same ballpark — roughly 150 kA class — but the letter codes are not interchangeable between brands. An "N" class NSX and an "N" class 3VA do not necessarily share the same kA figure; always read the nameplate, not the letter alone.
Where the two diverge is at the low end. NSX's B class (25 kA) gives a genuinely economy-tier breaking capacity option on the small frame. Siemens' entry classes on 3VA1 sit somewhat higher by comparison in most catalog configurations, which can matter on tight-budget feeder boards where 25 kA is enough and every kA of margin above that is unused capacity you paid for.
Micrologic vs ETU: Trip Unit Comparison
Both brands separate thermal-magnetic and electronic protection into distinct product tiers, but the swap mechanics differ. On NSX, Micrologic trip units are physically modular: TM-D/TM-G thermal-magnetic modules cover up to 250 A, and Micrologic electronic modules (2 = LI, 5 = LSI, 6 = LSIG with earth-fault, 7 = earth-leakage, plus an "E" energy-metering variant) slot into the same NSX body. A panel builder can order a bare NSX breaker and fit the trip module that matches the application, or swap the module later without replacing the breaker frame.
Siemens takes a split-product approach instead. 3VA1 carries a fixed TM (thermal-magnetic) trip unit — there is no electronic upgrade path on that frame. Electronic protection lives entirely on 3VA2, where ETU units range from ETU320 (basic LI protection) up to ETU850, which adds a graphic LCD, communications, and metering. ETU gives full LSIG protection on 3VA2, comparable in function to Micrologic 6.
Modular Swap vs Fixed Split: What It Means for Spares and Retrofits
This is the practical difference that matters most once the panel is built. Because NSX trip modules are field-swappable within one frame, a spares store can stock bare NSX250 breakers and a handful of Micrologic modules, then configure to order — or upgrade a customer from thermal-magnetic to LSIG protection on-site without pulling the breaker out of the panel. That flexibility carries a cost: Micrologic modules are sold and priced separately from the breaker body, so a fully configured NSX with Micrologic 6 costs more than the bare frame suggests.
Because 3VA1 and 3VA2 are separate product families rather than one frame with swappable modules, retrofitting a 3VA1 (thermal-magnetic) installation to electronic LSIG protection means replacing the whole breaker with a 3VA2, not swapping a module. What we see in the field: this pushes some panel builders to standardize on 3VA2 from the start on any circuit where a future protection upgrade is plausible, even if the initial application only needs basic LI protection, simply to avoid a full breaker swap later. Others deliberately buy 3VA1 to keep spares simple and cheap on non-critical feeders, accepting that any future upgrade is a breaker replacement, not a module swap.
Metering and Communication Options
Both ranges put metering behind the electronic trip tier, not the base breaker. On NSX, the Micrologic "E" variants (5E, 6E) add true RMS energy metering and can report over Modbus via an optional communication module — useful where sub-metering per feeder is required for tenant billing or energy audits. On 3VA2, metering and communications live on the higher ETU tiers (ETU740/ETU850 class), which add a graphic display and Modbus/Profibus connectivity depending on the ordering option.
Neither brand offers metering on its thermal-magnetic tier (TM-D/TM-G on NSX, TM on 3VA1) — if a spec calls for per-circuit energy data, the breaker selection is effectively forced onto the electronic-trip line on both brands, which raises the bill of materials regardless of which manufacturer wins the base breaker.
Icu vs Ics: Sizing Margin Across Both Brands
Icu (ultimate breaking capacity) is the headline kA figure on the nameplate; Ics (service breaking capacity) is what the breaker can interrupt and remain usable afterward, expressed as a percentage of Icu. This matters across both brands because the percentage is not always 100%. On some Schneider NSX classes, Ics is rated at 50-75% of Icu rather than the full figure; ABB and Siemens more commonly rate Ics at 100% of Icu on their higher classes, though this should always be confirmed against the specific frame and class on the datasheet, not assumed from the brand name. Icw (short-time withstand current) mostly applies to air circuit breakers, not MCCBs — most MCCBs on both ranges carry limited or no Icw rating, which affects discrimination studies where an upstream breaker needs to hold through a downstream fault.
Formula: Breaking Capacity Margin Check — Source: IEC 60947-2 §8.3
Icu ≥ Isc,max
| Symbol | Description | Unit |
|---|---|---|
| Icu | Rated ultimate breaking capacity of the selected breaker | kA |
| Isc,max | Maximum prospective short-circuit current at the installation point | kA |
| Ics | Rated service breaking capacity (percentage of Icu, per class) | kA |
Selecting the letter class on either range without checking the actual Ics percentage against expected fault-clearing frequency at that point in the installation is the most common sizing error we see repeated across both brands — full details on class selection are in the breaking capacity rating guide.
When to Pick Which: Application Guidance
Pick ComPact NSX when the project needs field-configurable protection: a spares strategy built around bare frames plus swappable Micrologic modules, or a retrofit path where trip settings and LSIG functions might change without replacing the breaker. NSX also suits projects standardizing on one frame (NSX100/160/250) across a wide current spread to simplify enclosure design.
Pick Sentron 3VA1 when the application is a fixed, non-critical thermal-magnetic feeder up to roughly 630 A and the spec is unlikely to change — the simpler fixed-trip product is normally the lower first cost. Pick 3VA2 when the application needs LSIG protection, metering, or communications from day one, particularly above 630 A where 3VA2 is the only electronic-trip path Siemens offers in this range. This depends on procurement policy too: some panel builders standardize on one brand per project for spares commonality, in which case the frame-family fit (not just the spec sheet) decides the winner. For broader frame and family selection beyond these two brands, see the MCCB engineering guide and the MCCB selection checklist.
ComPact NSX vs Sentron 3VA: Side-by-Side
| Criteria | Schneider ComPact NSX | Siemens Sentron 3VA |
|---|---|---|
| Frame families | NSX100/160/250 and NSX400/630 (two cases) | 3VA1 (TM) and 3VA2 (ETU), separate product lines |
| Current range | 15 A - 630 A | 3VA1 to ~630 A; 3VA2 to ~1000 A |
| Breaking classes (415 V) | B(25) F(36) N(50) H(70) S(100) L(150) kA | Letter classes to ~150 kA on top 3VA2 frames |
| Trip unit architecture | Field-swappable Micrologic modules on one frame | Fixed TM on 3VA1; fixed-family ETU on 3VA2 |
| Electronic trip functions | LI/LSI/LSIG/earth-leakage via Micrologic 2/5/6/7 | LI up to LSIG via ETU320-ETU850 |
| Metering | Micrologic "E" variants, optional Modbus | Higher ETU tiers, optional Modbus/Profibus |
| Ics vs Icu | Some classes rated 50-75% of Icu | Commonly rated closer to 100% on higher classes |
| Retrofit path | Swap trip module, keep breaker frame | 3VA1-to-electronic upgrade requires full breaker swap to 3VA2 |
Frequently Asked Questions
Can a Sentron 3VA1 be upgraded to electronic protection later?
No. 3VA1 carries a fixed thermal-magnetic trip unit with no electronic upgrade path on that frame. Moving to LSIG or metering means replacing the breaker with a 3VA2, not swapping a module.
Are Schneider and Siemens breaking-capacity letter classes the same kA value?
No. Both brands use letter codes for breaking class, but the kA figure behind each letter differs by product line and frame. Always confirm the actual kA rating on the datasheet rather than assuming letters match across brands.
Which range is cheaper for a simple feeder breaker with no metering?
Sentron 3VA1 or the base thermal-magnetic NSX (TM-D/TM-G module) are typically the lower-cost options, since neither carries the electronic trip unit's added cost. Between the two, pricing is project- and distributor-specific.
Does Micrologic 6 give the same protection functions as a Siemens ETU with LSIG?
Functionally yes — both provide long-time, short-time, instantaneous, and ground-fault protection (LSIG). The difference is architecture: Micrologic 6 is a swappable module on an NSX frame; the equivalent ETU on 3VA2 is tied to that frame family.
Is Icw relevant when comparing NSX and 3VA?
Rarely. Short-time withstand current (Icw) mainly applies to air circuit breakers used for selective coordination. Most MCCBs on both ranges, including NSX and 3VA, carry limited or no Icw rating, so discrimination studies typically rely on time-current curve coordination instead.
Can NSX and 3VA breakers be mixed in the same panel?
Electrically, yes — both comply with IEC 60947-2 and can be applied on the same distribution board as long as each breaker is individually sized to its circuit's fault current and load. Mixing brands does complicate spares stocking and selectivity studies, since coordination tables are brand-specific.
Conclusion
ComPact NSX and Sentron 3VA cover overlapping current and breaking-capacity ranges, and on paper the top-tier classes land close together. The real decision point is architecture: NSX's field-swappable Micrologic modules on one frame versus 3VA's split between a fixed 3VA1 and an electronic-only 3VA2. That choice affects spares stocking, retrofit cost, and how the project handles protection changes after commissioning — factors that matter more, in practice, than a few kA of difference in breaking class. Confirm the exact Ics percentage and Icw applicability against the installation's fault-current study before finalizing either brand; see the frame size and current rating guide and the IEC 60947-2 standards overview for the underlying clauses referenced above. Both ranges are stocked across current and breaking-capacity variants in the molded case circuit breakers collection.
