ABB Tmax XT vs Schneider ComPact NSX vs Siemens Sentron 3VA: MCCB Comparison

What is a molded case circuit breaker (MCCB)? An MCCB is a thermal-magnetic or electronic circuit breaker built into a molded insulating housing, rated from roughly 15 A to 1600 A, that protects distribution feeders and motor circuits against overload and short-circuit currents per IEC 60947-2. Pick the wrong breaking capacity or trip unit and you either pay for headroom you never use or, worse, install a breaker that cannot clear the prospective fault at the busbar. This guide compares the three ranges most engineers cross-shop — ABB Tmax XT, Schneider ComPact NSX, and Siemens Sentron 3VA — on frame structure, breaking-capacity classes, trip units, metering, and where each one earns its place in a panel.

The three families solve the same problem in noticeably different ways. Knowing where they diverge saves you a redesign later. For the full selection methodology behind these ranges, see our molded case circuit breaker engineering guide.

The short answer, before the detail

Here is the one-line verdict: all three clear a well-designed distribution board without complaint up to 630 A. The differences show up at the edges. The very high fault levels, the metering you need for an energy-monitored switchboard, and the accessories on your shelf. Below is the frame-by-frame picture.

Read the table as a starting map, not a verdict. A 250 A feeder at a 36 kA busbar is a commodity — every one of these breakers does it in its sleep. The selection gets interesting above that.

Frame structure: how each maker slices the range

ABB splits Tmax XT into seven frames. XT1 and XT3 are the economy thermal-magnetic workhorses up to 250 A; XT2 and XT4 share the same footprints but add the Ekip electronic trip and push breaking capacity higher. That shared-footprint logic matters in practice: you can start a project with an XT2 thermal-magnetic and later swap in an Ekip electronic unit without touching the enclosure cutout. Engineers often overlook that continuity until they are mid-retrofit.

Schneider takes a different route. ComPact NSX uses three physical sizes — NSX100/160/250 on one frame, NSX400/630 on the larger — and layers trip units on top. The clever part is the trip unit being a separate, field-swappable module across the whole range. One NSX250 body accepts a basic TM-D thermal-magnetic or a Micrologic 6 with earth-fault and metering. That modularity is the family's real selling point.

Siemens draws the sharpest line of the three. The 3VA1 is thermal-magnetic, full stop. The 3VA2 is electronic, with the ETU. There is no in-between. That makes specification unambiguous — you read the family straight off the type code — but a mid-life upgrade from thermal-magnetic to electronic is a breaker change, not a module change. To see how these split by construction, our guide on types of molded case circuit breakers breaks it down further.

Breaking capacity: where the money is

This is the spec that separates a low-cost breaker from a premium one in the same frame. Breaking capacity, the Icu rating, is the prospective short-circuit current the device can interrupt without destroying itself. Our deep dive on MCCB breaking capacity ratings covers the class letters in detail; here is the comparison that matters when choosing between brands.

All three makers sell the same frame in a ladder of breaking-capacity classes, so you buy only the interrupting rating you need. ABB uses the letters N, S, H, L, V; Schneider uses B, F, N, H, S, L; Siemens uses N, M and equivalents. The naming differs, the idea is identical.

At 415 V AC the top of each range lands close together: Tmax XT reaches 200 kA in the V class, while ComPact NSX tops out near 150 kA (L) and Sentron 3VA around 150 kA (M) on its highest electronic frames. In most industrial boards fed from a distribution transformer up to 2500 kVA, prospective fault current sits in the 25–65 kA band, and every one of these families covers it with a mid-tier class. The 150–200 kA classes exist for tight-coupled generation, large parallel transformers, and utility interfaces. Pay for them only when your fault study demands it.

A word of caution on comparing across brands: Icu (ultimate) and Ics (service) are not the same number, and Ics is what tells you whether the breaker stays in service after clearing a fault. ABB and Siemens frequently rate Ics at 100% of Icu on their higher classes; some Schneider NSX classes rate Ics at 50–75% of Icu. Two breakers with the same headline Icu can behave very differently after a real fault. Read the Ics column, not just the poster number.

Trip units and metering

For a plain feeder, a thermal-magnetic trip is honest and cheap. TMD and TMA on Tmax XT, TM-D and TM-G on NSX, and the TM on 3VA1 all give you adjustable overload and either fixed or adjustable magnetic pickup. Nothing to configure, nothing to fail in software.

The moment you need selective coordination, current metering, or earth-fault protection, you move to electronic. Here the three diverge in philosophy:

• ABB Ekip — the Ekip Dip sets protection with physical dip-switches, so no laptop is needed on site, while Ekip Touch and Hi-Touch add an LCD, energy metering, and full LSIG protection. Good when you want a graded line from bare-bones to fully instrumented.
• Schneider Micrologic — numbered by capability: Micrologic 2 is LI, 5 is LSI, 6 adds earth-fault (LSIG), 7 adds earth-leakage. The "E" energy variants meter kWh directly. The clearest numbering in the industry once you learn it.
• Siemens ETU — from the basic ETU320 up to the ETU850 with a graphic display and communication. Metering accuracy on the higher ETUs is strong, and the type code tells you the protection function without a catalog lookup.

In practice the choice here follows your monitoring strategy more than the breaker itself. If the switchboard reports energy to a BMS, the electronic trip is doing double duty as your meter, and you should spec it around the data you need, not the interrupting rating alone. What we typically see in the field is a panel builder standardizing on one trip platform across a project to cut spares and training, even where a competitor frame would fit a single feeder better.

Accessories, availability, and the boring stuff that decides projects

There is no universal answer to "which brand is best," because the deciding factor is usually not the breaker. It is whether the shunt trip, auxiliary contact, motor operator, and Vigi or RC earth-leakage module are on a shelf when your panel builder needs them. All three ranges share accessories within the family, which cuts your spares list. What differs is regional stock depth and lead time.

That is exactly where cross-referencing matters. If a project was drawn around a Sentron 3VA with an ETU and the lead time runs to eight weeks, an ABB XT4 with an equivalent Ekip Touch or a ComPact NSX250 with Micrologic 6 will usually drop into the same duty. Same current, same Icu class, same LSIG function, provided you check the frame dimensions and terminal arrangement against the existing busbar. We do this substitution regularly; the trap is the mounting and connection detail, not the electrical rating. When you get to the selection stage, the MCCB selection checklist keeps the swap honest.

So which one should you specify?

It depends on what the project rewards. Choose Tmax XT when you want the highest top-end breaking capacity and a clean thermal-magnetic-to-electronic upgrade path in a fixed enclosure cutout. Choose ComPact NSX when field-swappable trip units and add-on earth-leakage matter more than the last 50 kA of headroom. Choose Sentron 3VA when unambiguous type coding and strong ETU metering suit your documentation and BMS. For anything below 630 A and 65 kA, honestly, availability and your panel shop's familiarity should break the tie. New to how these compare with smaller devices? See what an MCCB is and how it works.

Conclusion

At the electrical level these three ranges are closer than their marketing suggests. Up to 630 A and 65 kA, the choice comes down to trip-unit ergonomics, the metering your switchboard reports, and what your distributor can ship this week. Tmax XT gives you the highest top-end breaking capacity and a smooth upgrade path. ComPact NSX gives you the cleanest modular trip-unit swap. Sentron 3VA gives you the least ambiguous type coding and strong ETU metering. Size around Ics, match the trip function to your monitoring plan, and keep the cross-reference in your back pocket for when lead times bite. For the full methodology, return to the MCCB engineering guide, or browse in-stock molded case circuit breakers at Stoklink.