ABB Tmax XT vs Schneider ComPact NSX: Technical Comparison

What's the real difference between ABB Tmax XT and Schneider ComPact NSX? Both are IEC 60947-2 molded case circuit breakers covering roughly 16 A to 630 A at the frames most panel builders specify, but they split the breaking-capacity ladder differently, mount their electronic trip units differently, and use non-interchangeable accessory lines. The consequence shows up at spec-review time: a drawing that calls out "Tmax XT4 250 A, Ekip LSI" cannot be substituted with an NSX250 Micrologic 5 without re-checking Icu/Ics, terminal kit, and door-mount cutout. This article compares frame structure, breaking-capacity classes, trip unit families (Ekip vs Micrologic), accessory and cassette interchangeability, and gives a straight answer on when to default to each brand.

Frame Structure: XT1-XT7 vs NSX100-NSX630

Tmax XT spans seven frame sizes: XT1 and XT3 are the economy thermal-magnetic frames, rated to 250 A with TMD/TMA trip units and no electronic option. XT2 and XT4 share the same physical footprint as XT1/XT3 but add the Ekip electronic trip and a higher breaking-capacity ceiling — same box, more breaker. XT5 covers 400/630 A, XT6 sits at 630/800 A, and XT7 tops out around 1600 A. That's four distinct frame footprints for four current bands, plus a thermal/electronic split inside the two lowest bands.

ComPact NSX takes a coarser approach: NSX100, NSX160, and NSX250 share one frame family from 15 A up to 250 A, and NSX400/NSX630 form the second family up to 630 A. Fewer physical case sizes to stock, fewer door cutout templates to draft, but less granularity — an NSX160 at 40 A and an NSX160 at 160 A are the same physical breaker with different trip settings, where ABB would likely have moved you into a different XT frame at the top of that range.

Breaking-Capacity Classes: N/S/H/L/V vs B/F/N/H/S/L

Both brands use letter suffixes for breaking capacity, and the letters do not mean the same thing across brands — this trips up people moving between ABB and Schneider catalogs. Tmax XT runs N, S, H, L, V in ascending order, with the V class reaching roughly 200 kA at 415 V on the higher frames. ComPact NSX runs B(25), F(36), N(50), H(70), S(100), L(150) kA at 415 V — six classes instead of five, and the letter N sits in the middle of Schneider's scale (50 kA) rather than near the bottom of ABB's.

Read the class letter against the brand's own table before quoting a value on a drawing. "H class" on a Tmax XT4 and "H class" on an NSX160 are not the same kA figure.

Icu vs Ics — Why the Letter Alone Isn't Enough

Icu tells you what the breaker survives once. Ics tells you what it survives and remains fully rated for afterward. ABB and Siemens generally rate Ics at 100% of Icu on their higher classes; several Schneider NSX classes rate Ics at only 50-75% of Icu. That gap matters on a feeder breaker that's expected to stay in service through nuisance short-circuit events without a swap.

Icw (short-time withstand current) is mostly an air circuit breaker parameter; MCCBs in general — Tmax XT and ComPact NSX included — carry little or no Icw rating, so selective coordination through a fault relies on time-current curve separation, not withstand duration. See our MCCB breaking capacity guide for the class tables in full.

Trip Units: Ekip vs Micrologic

ABB's electronic trip family on Tmax XT2/XT4 and up is Ekip. Ekip Dip is set with physical dip switches — no display, no comms, cheapest electronic option. Ekip Touch and Ekip Hi-Touch add an LCD, metering, and full LSIG protection (long-time, short-time, instantaneous, ground fault) with Modbus or similar fieldbus output on the Hi-Touch variant. Thermal-magnetic frames (XT1/XT3) instead use TMD or TMA, fixed or adjustable, no electronics at all.

Schneider's Micrologic trip units are field-swappable modules on ComPact NSX — pull one cassette, insert another, without replacing the breaker body. Micrologic 2 gives LI (long-time, instantaneous) protection only. Micrologic 5 adds short-time (LSI). Micrologic 6 adds ground-fault protection (LSIG). Micrologic 7 adds earth-leakage sensing. An "E" suffix on any of these adds energy metering. TM-D and TM-G cover the thermal-magnetic tier up to 250 A, parallel to ABB's TMD/TMA.

What we see in the field: Micrologic's swap-in-place design is genuinely useful on a retrofit where the breaker frame is fine but the protection scheme needs to change — you're not pulling wiring off a busbar to do it. Ekip on Tmax XT is less modular in that specific sense, though the Touch/Hi-Touch range covers most of the same functional ground once specified correctly up front.

Accessories and Interchangeability

Neither brand's accessories cross over — motor operators, shunt trips, auxiliary contacts, and undervoltage releases are frame-specific and brand-specific on both Tmax XT and ComPact NSX. This is the detail that catches spec writers who assume "MCCB accessory" is a generic category: an XT4 motor operator will not bolt onto an NSX250, and a Vigi earth-leakage add-on module is Schneider-only, with no direct Ekip equivalent sold as a bolt-on block (earth-fault protection on Ekip comes built into the LSIG trip unit itself, not as a separate add-on module).

Within one brand, interchangeability is stronger. ABB's XT2 and XT4 share a case, so accessories designed for one frame size largely carry to the other. Schneider's NSX100/160/250 family behaves the same way — one accessory catalog across three current ratings. That single-family accessory reuse is a real spares-inventory advantage for a panel shop standardizing on either brand, but it does not extend across brands.

ABB Tmax XT vs Schneider ComPact NSX — Comparison Table

When to Pick Which

Pick Tmax XT when the project needs a fine-grained frame ladder — four footprints across the current range let a panel builder match breaker size to enclosure space more tightly, and the V class gives headroom on the highest-fault-level switchboards without stepping up to an air circuit breaker. Ekip Hi-Touch's comms output fits panels already standardized on ABB's automation stack.

Pick ComPact NSX when the project values a smaller accessory and spares catalog — two frame families instead of four means fewer SKUs on the shelf for a shop running high breaker volume. Micrologic's field-swappable cassette is the stronger argument when the same panel design needs to serve customers who want LI-only protection and customers who want full LSIG, off the same physical breaker body.

Neither answer is universal. This depends on what's already installed upstream and downstream in the panel — a lineup with ABB switchgear elsewhere in the panel usually stays ABB for spares commonality, and the same logic applies in reverse for an existing Schneider installation. See the MCCB selection checklist for the full sizing sequence before locking in a brand.

Conclusion

Tmax XT and ComPact NSX both meet IEC 60947-2 across overlapping current ranges, but the resemblance stops at the datasheet cover page. Frame count, breaking-class letter scales, trip unit architecture, and accessory catalogs are each brand-specific, and none of the four cross over. Match Ics — not the class letter — to the fault level, confirm which trip family the rest of the panel already standardizes on, and treat "equivalent" specs from the two brands as a starting point for verification, not a substitution you can make on the drawing without checking the datasheet. For the broader frame, voltage, and current-rating breakdown across all three major MCCB brands, see the MCCB engineering guide and browse current stock in our molded case circuit breakers collection.