Short answer: both the NB1-63 and the NXB-63 are 1–63 A miniature circuit breakers to IEC/EN 60898-1, with B, C and D curves, a 6 kA standard rating and a 10 kA high-breaking variant. The difference is not the headline number. The NXB-63 is the newer platform: 10,000 electrical operations, a side-mounted 9 mm accessory family (AX-X1, AL-X3, SHT-X1, UVT-X1, OVT-X3) and a certificate file weighted towards export markets. The NB1-63 keeps 4,000 electrical operations, clip-on accessories (XF9, XF9J, S9, V9) and a TÜV / VDE / CB / UL file that many European buyers already recognise. Choose by accessory family and certificate file — not by kA.
This page compares the two series the way a buyer actually has to choose between them: what is identical, what is not, and which line on the purchase order decides the outcome. It is written from the position of an independent trading company — not a manufacturer, and not an appointed distributor of any brand. Every certificate statement is tied to an exact ordering code rather than to a brand name.
What the two series have in common
Both are DIN-rail modular devices with 9 mm per pole, rated 50/60 Hz, with a rated insulation voltage of 500 V and a rated impulse withstand of 4 kV. Both cover 1 A to 63 A in the standard current steps — 1, 2, 3, 4, 6, 10, 13, 16, 20, 25, 32, 40, 50 and 63 A — and both offer 1P, 1P+N, 2P, 3P, 3P+N and 4P configurations. Both are IP20 at the front face, designed for enclosure mounting, and both trip on the same B, C and D magnetic bands: 3–5 In, 5–10 In and 10–20 In.
That overlap matters: for a lighting or socket final circuit with no shunt trip, no remote alarm and no specific national certificate, either series closes the line. The decision only becomes real when the accessory, the certificate or the service life is on the drawing.
Where the two series actually differ
| Attribute | NB1-63 (and NB1-63H) | NXB-63 (and NXB-63H) |
|---|---|---|
| Standard | IEC/EN 60898-1; separate manuals exist for the IEC 60947-2 and UL 1077 versions | IEC/EN 60898-1 |
| Rated voltage marking | 230/400–240/415 V AC | 220/230/240 V AC for 1P, 1P+N, 2P; 380/400/415 V AC for 2P, 3P, 3P+N, 4P |
| Breaking capacity | Icn 6 kA; 10 kA on the -63H variant | Icn 6 kA; 10 kA on the H variant (Ics 7.5 kA at 2P 220–240 V) |
| Electrical life | 4,000 operations | 10,000 operations |
| Mechanical life | 20,000 operations | 20,000 operations |
| Auxiliary accessories | XF9 auxiliary contact, XF9J alarm contact, S9 shunt release, V9 undervoltage release | AX-X1 / AX-X3 auxiliary, AL-X3 alarm, SHT-X1 / SHT-X3 shunt, UVT-X1 / UVT-X3 undervoltage, OVT-X3 overvoltage |
| Accessory mounting | Clip-on to the breaker body | Side-mounted on the left, 9 mm module |
| Published certificate files | TÜV, VDE, CB, UL (US), CCC, CE declaration | UKCA, IRAM, KC, plus CE, SNI, NOM, EAC and SII listed across regional catalogues |
The life figure is the difference buyers underestimate. At 4,000 electrical operations the NB1-63 is a domestic and light-commercial device — roughly a decade of normal switching in a flat, far less where the breaker doubles as the daily isolator. At 10,000 operations the NXB-63 survives being switched twice a day for thirteen years.
The accessory family decides more than the breaker
A shunt trip is where most of these comparisons stop being academic. Remote tripping from a fire panel, a timer or a building management contact needs a release coil that physically matches the breaker. The NB1-63 takes the S9 shunt release and the V9 undervoltage release. The NXB-63 takes the SHT-X1 or SHT-X3 shunt and the UVT-X1 or UVT-X3 undervoltage release, mounted on the left side in a 9 mm module. The two families do not interchange — a bracket for one will not accept the other’s coil, and the trip paddle sits at a different height.
For NXB-63 the auxiliary contact is rated AC 415 V 3 A, AC 240 V 6 A and DC 24 V 6 A, with a mechanical and electrical life of at least 10,000 operations. That is enough for a status input to a PLC or a lamp on a panel door. It is not a contact for switching a contactor coil directly at 230 V; use it to drive an interposing relay. The AL-X3 alarm contact is the one that reports a trip rather than the handle position — useful when the breaker sits behind a locked enclosure door and the panel only shows a summary alarm.
On the NB1-63 the equivalents are XF9 for auxiliary and XF9J for alarm, clipped to the device without extra rail space — an advantage in a crowded consumer unit where a 9 mm side module can push the row past the way count.
Certificates: one brand, two different files
Neither series carries a brand-wide certificate, and this is where catalogue pages mislead. The NB1-63 file includes TÜV, VDE, CB and UL documents alongside the CE declaration; the CCC mark there is a Chinese domestic requirement, not an export selling point. The NXB-63 file leans the other way: UKCA for Britain, IRAM for Argentina, KC for Korea, with CE, SNI, NOM, EAC and SII listed regionally.
Two consequences follow. First, if the destination asks for a European-type certificate file that a consultant can read quickly, the NB1-63 family is the easier conversation. Second, if the destination is Argentina, Korea or the UK, the NXB-63 usually has the paperwork already open — but only for the ratings and poles actually covered by that certificate, which is why the ordering code has to be quoted before anyone confirms anything. A CB report for a 2P 25 A device does not certify a 4P 63 A device.
One more distinction worth keeping straight: the NB1-63 has a UL 1077 supplementary-protector manual version. UL 1077 is supplementary protection inside listed equipment. It is not UL 489 branch-circuit protection, and a UL 1077 device cannot replace a UL 489 breaker in a North American panel. The same caution applies to any 240 V IEC device proposed for a 120 V market: the voltage marking is a maximum, so a 240 V breaker on a 120 V system is not overstressed, but what a 120 V market actually accepts is its own listing — UL, CSA or NOM — not an IEC type test.
Which series to order
| Application | Suggested series | Reason |
|---|---|---|
| Residential final circuits, no accessories | NB1-63 | Lowest cost for the job; 6 kA is ample downstream of a 6 kA board |
| Shop or workshop main board switched daily | NXB-63 | 10,000 electrical operations; 9 mm side accessories for a status lamp |
| Fire-panel or BMS remote trip | NXB-63 with SHT-X1/X3, or NB1-63 with S9 | Pick the family whose release coil is available for that exact code |
| Argentina, Korea or UK destination | NXB-63 | IRAM, KC and UKCA files are open on this series |
| European consultant specification with a VDE/TÜV file | NB1-63 | Certificate file is the one the reviewer expects to see |
| Solar DC string, 1000 V DC | Neither — use NB1-63DC | AC MCBs are not rated for DC arcs; the DC series is a separate device |
What to put on the purchase order
The breaker’s series, current, curve, poles, breaking capacity letter and accessory codes — plus the destination country, the system voltage and frequency, and whether the board needs a shunt trip or an auxiliary contact. Anything shorter and the supplier quotes a device that fits the ampere rating but not the drawing. We quote the code that matches the grid and the certificate file that exists for that code, and we say plainly when a file does not exist yet.
FAQ
Is NXB-63 a replacement for NB1-63?
No — they are parallel ranges. NXB-63 is the newer platform with longer electrical life and a different accessory family, but NB1-63 remains in the catalogue and is the series with the TÜV/VDE/CB/UL documents. Replacing one with the other changes the accessory mounting, so it is a board-level decision, not a like-for-like swap.
Can I use NB1-63 accessories on an NXB-63?
No. The XF9, XF9J, S9 and V9 clip to the NB1 body; the AX-X1, AL-X3, SHT-X1 and UVT-X1 family mounts on the left in a 9 mm module. The trip interface and the physical height differ.
Does the 10 kA version cost the same as the 6 kA?
Pricing depends on the exact code, quantity and destination, and we quote it per enquiry rather than publishing numbers that go stale. The 10 kA variant is a different device inside, not a label change.
Which series should I use at 127 V or 120 V?
The voltage marking on either series is a maximum, so a 240 V device on a 120 V system is not overstressed — but a 120 V market accepts its own listing, and an IEC type test is not that listing. Tell us the grid and the destination and we will quote the code whose certificate actually covers that market.
Does the H suffix mean 10 kA on both series?
Yes, in both families the H variant raises Icn from 6 kA to 10 kA. Confirm the exact ordering code, because the certificate file and the Ics value can differ between frames and pole configurations.
Related: NB1-63 miniature circuit breakers · MCB range overview · 6 kA vs 10 kA breaking capacity · MCB trip curves B, C and D · How to read an MCB marking · Cross-reference an existing breaker · How we verify genuine product · Request a quotation