MCCB Cross-Reference: ABB Tmax, Schneider NSX, Siemens 3VA Replacement
Can you replace an ABB Tmax XT breaker with a Schneider ComPact NSX or Siemens Sentron 3VA unit? Cross-referencing an MCCB across brands means matching frame current, breaking-capacity class (Ics per IEC 60947-2 §8.3), pole count, and trip function (LI, LSI, or LSIG) — no universal part-number equivalence exists between manufacturers. Get one of these wrong and the replacement either nuisance-trips on inrush, fails to interrupt a fault within its rated capacity, or will not physically fit the panel cutout. This article covers frame-current matching, breaking-class matching, pole and trip-function matching, a function-based cross-reference table for ABB Tmax XT, Schneider ComPact NSX, and Siemens Sentron 3VA, and the mechanical variables (mounting footprint, terminal type, accessories) that never cross-reference.
Why Cross-Referencing an MCCB Is Not a Part-Number Lookup
No manufacturer publishes a cross-brand equivalence table, and no distributor catalog reliably maps an ABB SKU to a Schneider or Siemens one. Each brand built its frame families around its own current steps, its own breaking-capacity letter codes, and its own trip-unit architecture. A 250 A frame from one brand is not dimensionally or electrically identical to a 250 A frame from another — only the current rating lines up.
Cross-referencing, done properly, is a four-variable match: frame current, breaking class, poles, and trip function. Miss the mechanical layer on top of that — footprint, terminals, accessories — and the electrically "equivalent" breaker still might not go in the panel. Treat every substitution as a verification exercise, not a lookup.
Step 1: Match the Frame Current, Not the Nameplate Setting
Start with the frame, not the trip setting stamped on the dial. An ABB XT4 250 A frame set to trip at 160 A is still a 250 A frame — thermally and mechanically. If you cross-reference against the 160 A setting instead of the 250 A frame, the replacement you select will be undersized for the busbar and connector ratings the original frame was built for.
Read the frame current off the nameplate ampere rating in the top-left corner, not the trip-unit dial. ABB Tmax XT steps in this range run XT1/XT3 to 250 A, XT2/XT4 sharing footprints with added Ekip electronic trip, XT5 at 400/630 A, XT6 at 630/800 A, and XT7 up to 1600 A. Schneider ComPact NSX runs NSX100/160/250 as one frame family and NSX400/630 as a larger one, 15 A to 630 A overall. Siemens Sentron covers thermal-magnetic on 3VA1 (frames 3VA10 to 3VA16, to roughly 630 A) and electronic on 3VA2, to roughly 1000 A. See the voltage, current, and frame size ratings reference for the full breakdown by brand.
Step 2: Match Breaking Capacity by Class, Not the kA Number Alone
Breaking-capacity letter classes are brand-specific codes, and they do not translate directly across manufacturers. ABB uses N, S, H, L, V (ascending, topping out near 200 kA at 415 V on the V class). Schneider ComPact NSX uses B(25), F(36), N(50), H(70), S(100), L(150) kA at 415 V. Siemens Sentron marks classes such as N and M, topping near 150 kA at 415 V on the higher 3VA2 frames. Ignore the letters when cross-referencing — compare the actual kA value at the installation voltage.
Icu (ultimate breaking capacity) and Ics (service breaking capacity) are not the same number, and this is where most cross-reference mistakes happen. ABB and Siemens commonly rate Ics at 100% of Icu on their higher classes. Some Schneider NSX classes rate Ics at only 50-75% of Icu. A breaker that looks like a drop-in match on the Icu nameplate value can be under-rated on Ics — the number that actually governs whether the breaker survives a fault clearing operation and remains serviceable afterward. Size the replacement around Ics, always.
Formula: Minimum Service Breaking Capacity Check — Source: IEC 60947-2, §8.3
Ics(replacement) ≥ Ik,max(pc)
| Symbol | Description | Unit |
|---|---|---|
| Ics(replacement) | Rated service breaking capacity of the substitute breaker at the installation voltage | kA |
| Ik,max(pc) | Maximum prospective short-circuit current at the point of connection | kA |
Icw (short-time withstand current) is largely an air circuit breaker parameter — most MCCBs carry limited or no Icw rating, so it rarely enters the cross-reference decision unless the original application specifically used it for zone selectivity. For the full class-by-class breakdown, see breaking capacity classes explained.
Step 3: Match Poles and Trip Function (LI, LSI, LSIG)
Pole count is the easy part: 3-pole and 4-pole are not interchangeable, and a 4-pole breaker installed where a 3-pole was specified changes neutral switching behavior on the circuit. Confirm this before anything else, because it eliminates candidates fast.
Trip function is where brand naming gets confusing. LI means long-time plus instantaneous protection only — the simplest curve. LSI adds a short-time delayed element for coordination with downstream devices. LSIG adds ground-fault protection on top of LSI. ABB delivers this through Ekip trip units: Ekip Dip uses physical dip switches for settings, Ekip Touch and Hi-Touch add an LCD, metering, and full LSIG. Schneider delivers it through Micrologic modules, which clip into the breaker as field-swappable units: Micrologic 2 is LI, 5 is LSI, 6 adds ground fault for LSIG, 7 adds earth-leakage, and an "E" suffix adds energy metering — a Vigi add-on module handles earth-leakage separately from the main trip unit. Siemens delivers it through ETU units on the 3VA2 frame, from the basic ETU320 up to the graphic-display ETU850 with communications and metering; 3VA1 stays thermal-magnetic only, with no LSIG option at all.
What we see in the field: teams assume "LSIG is LSIG" across brands and copy over the old settings verbatim. That is not a safe assumption. Curve shapes, adjustable ranges, and time-current tolerances differ by manufacturer even at the same nominal function. Any cross-brand substitution on an LSI or LSIG breaker means the coordination study gets re-run, not re-used.
Cross-Reference Table by Function
This table maps by function and frame tier, not by specific part number — treat it as a starting shortlist, then verify the exact model against a current datasheet before ordering. It deliberately avoids exact catalog codes where the mapping depends on options (trip unit, terminal, accessories) chosen at order time.
| Function / Frame Tier | ABB Tmax XT | Schneider ComPact NSX | Siemens Sentron 3VA |
|---|---|---|---|
| Economy thermal-magnetic, to ~250 A | XT1/XT3, TMD trip | NSX100-250, TM-D/G trip | 3VA1, TM trip |
| Mid-frame, electronic trip option, ~160-630 A | XT4, Ekip Dip/Touch | NSX250-630, Micrologic 2/5 | 3VA2, ETU320-ETU350 |
| High electronic, LSIG + metering, ~250-630 A | XT5/XT6, Ekip Hi-Touch | NSX400-630, Micrologic 6/6E/7 | 3VA2, ETU656/ETU850 |
| Large frame, electronic only, above 630 A | XT7, to 1600 A | no MCCB frame beyond NSX630 — larger ratings move to the ACB range | 3VA2, to roughly 1000 A — no MCCB frame above that |
| Trip unit field-swappable without frame change | typically factory-fitted at order time | yes — Micrologic/TM modules clip in and out | typically factory-fitted at order time |
| Top breaking class at 415 V (approx.) | ~200 kA (V class) | 150 kA (L class) | ~150 kA (high 3VA2 frames) |
Read the table by row, not by column: pick the function you need first, then compare which brand's frame and trip family covers it. If the original breaker sits in the "large frame above 630 A" row and the replacement has to come from ComPact NSX, there is no MCCB-class substitute — that gap gets flagged, not papered over with an undersized frame.
What Never Cross-References: Mounting, Terminals, Accessories
Frame current, breaking class, and trip function are electrical parameters. Mounting footprint, terminal type, and accessory compatibility are mechanical parameters, and none of them are standardized across brands — sometimes not even across frame sizes within the same brand.
Mounting footprint: hole spacing, mounting depth, and DIN-rail versus base-mount options differ by frame and by brand. A breaker that matches electrically can still be 15-20 mm too deep for the enclosure, or use a bolt pattern that does not line up with the existing cutout.
Terminal type: front-connected, rear-connected, extended terminals, box lugs, and ring-and-flag lugs are frame-specific options, not universal fittings. A busbar drilled for one brand's rear terminal spacing will not necessarily accept another brand's rear terminal, even at the same frame current.
Accessories: shunt trips, undervoltage releases, auxiliary and alarm contacts, and motor operators mount into brand-specific and often frame-specific cradles. An auxiliary contact block from one manufacturer's 250 A frame does not clip into a competitor's 250 A frame, and in most cases not into a different frame size from the same manufacturer either.
When to Request an Equivalent Instead of Guessing
If the original breaker is obsolete, the datasheet is unavailable, or the fault-level data at the point of connection is uncertain, guessing at a cross-reference carries real risk — an under-rated breaker on Ics is a fault-clearing failure waiting for the wrong day. This depends on how well-documented the original installation is; a panel with as-built drawings and a recent fault-level study is a different situation from a legacy board with no paperwork.
Send Stoklink the nameplate details — frame current, breaking class or kA rating, pole count, trip function, and mounting type if known — and request a verified equivalent across ABB, Schneider, and Siemens stock before ordering. Browse current availability across the three brands in the molded case circuit breakers collection, or check the MCCB selection checklist and the IEC 60947-2 standards reference for the full parameter list to gather before you ask.
Frequently Asked Questions
Can I directly swap an ABB Tmax XT breaker for a Schneider ComPact NSX in the same panel?
Only if frame current, Ics, poles, and trip function all match, and the enclosure cutout and terminals accept the new frame's footprint. Electrical equivalence does not guarantee mechanical fit — check both.
Do breaking-capacity classes mean the same thing across ABB, Schneider, and Siemens?
No. The letter codes are brand-specific — ABB uses N/S/H/L/V, Schneider uses B/F/N/H/S/L, Siemens uses codes like N/M. Compare the actual kA value at your system voltage, not the letters.
Should I match Icu or Ics when cross-referencing breaking capacity?
Match Ics. It is the capacity the breaker retains after clearing a fault without needing full inspection or rebuild. Some Schneider NSX classes rate Ics at only 50-75% of Icu, lower than the 100% common on ABB and Siemens's higher classes.
Will an LSIG trip unit from one brand behave exactly like LSIG from another?
No. The function name matches, but curve shapes, adjustable ranges, and time-current tolerances differ by manufacturer. Any cross-brand substitution on an LSI or LSIG breaker means the downstream coordination study needs to be re-checked.
What information should I send Stoklink to get a cross-reference recommendation?
The original SKU or a nameplate photo, frame current, system voltage, prospective fault current at the point of installation, pole count, and the trip function required. Mounting type and terminal style, if known, narrow the mechanical fit as well.
Conclusion
A reliable MCCB cross-reference runs through four checks in order: frame current off the nameplate, breaking class compared by kA value at your voltage (Ics, not Icu), pole count, and trip function. None of that guarantees mechanical fit — footprint, terminal type, and accessory compatibility are brand-specific and have to be verified against the actual panel separately. Treat any cross-brand substitution as unverified until both the electrical and mechanical checks clear, and when the original breaker's data is incomplete, get a verified equivalent from Stoklink before ordering rather than sizing on a guess. For the underlying selection criteria, the MCCB engineering guide covers the full sizing and selection process end to end.
