Short answer: a DZ15 frame and a DZ158 frame are not interchangeable, even when the ampere rating on the old label matches. DZ15 is a GB-standard moulded-case device rated for domestic 220/380 V systems with frames up to 250 A; DZ158 is the IEC 60947-2 modular line, In up to 125 A, in 1P to 3P. A replacement therefore has three questions before the price: does the current fit inside 125 A, do the poles match, and what breaking capacity does the fault level at that board actually require.
Upgrades of this kind turn up in two situations: an old installation being re-certified for export duty, and a plant replacing a discontinued frame where the drawings still say DZ15. Both look like a part-number swap on paper. Neither is, and the failure mode is quiet — a device that fits the rail, carries the load, and does not have the short-circuit rating the installation was designed around. We are an independent trading company: not a manufacturer, not an appointed distributor of any brand.
What DZ15 is, and why the label does not travel
DZ15 is a moulded-case circuit breaker built to Chinese national standards rather than to the IEC 60947 series, with domestic sample ratings quoted at 220/380 V and frames reaching 250 A in the Chinese catalogue. That description is accurate and it is also the problem: the ratings are domestic, the voltage basis is a 220/380 V system, and the test evidence behind them is not the document a European, Gulf or Latin American authority will accept.
Two things follow. The first is documentation: a certificate that satisfies a domestic market does not answer an importer’s question elsewhere, and the CCC mark is a Chinese market requirement — not an export selling point. The second is engineering: a 220/380 V rating is a different insulation basis from a 240/415 V one. DZ158 is the IEC 60947-2 line that occupies the same application space internationally: In up to 125 A, 1P to 3P, a published English product page, and a modular format that shares the rail and busbar logic of the NB1 and NXB families.
| DZ15 (old frame) | DZ158 | NXB-125G | NM1 / NXM | |
|---|---|---|---|---|
| Standard basis | GB (domestic) | IEC 60947-2 | IEC 60947-2 | IEC 60947-2 |
| Rated current | Domestic sample up to 250 A | Up to 125 A | 1–125 A | 10–1250 A (NM1), 16–1600 A (NXM) |
| Voltage basis | 220/380 V domestic | IEC marking | IEC marking | Up to 690 V AC |
| Poles | 2P, 3P, 4P | 1P, 2P, 3P | Confirm per code | 2P, 3P, 4P |
| Format | Moulded case, older frame dimensions | Modular, DIN rail | Modular, DIN rail | Moulded case, fixed or plug-in |
| Certificate basis | Domestic | Per ordering code | Per ordering code | CB, KEMA and others per frame |
The first trap is the frame ceiling
DZ15 frames run beyond 125 A. DZ158 stops at 125 A. That single line decides the shape of the project, because a 160 A or 250 A DZ15 cannot be replaced by a larger DZ158 — there is no larger DZ158. Above 125 A the replacement becomes an MCCB, and an MCCB brings different enclosure depth, different terminal arrangements, different cable lug sizes and a different busbar layout.
This is where budgets go wrong. The plan assumes a rail swap; the reality is a board rebuild for the affected ways. List every outgoing way with its current and frame, mark the ones above 125 A, and price those as an MCCB change. Where the load is genuinely below 125 A but the old frame was oversized, the modular replacement is straightforward — and often an improvement, because a 125 A modular device occupies less width and leaves room for the same number of ways.
The second trap is the fourth pole
DZ15 was commonly installed as 2P, 3P and 4P; DZ158 is published as 1P to 3P. A 4-pole DZ15 therefore has no like-for-like answer, and there are only two honest routes: move to a family that offers a 4-pole device at that current, or use a 3-pole device plus a separate switched neutral, which changes the isolation logic on the board. The second route is often what the installer proposes and rarely what the drawing allows — if the neutral was a switched pole, a solid link changes what the isolation point actually isolates.
The third trap is breaking capacity
The usually quoted figure for the 125 A frame is 10 kA on the H variant, and 10 kA is a serious number for a modular device — but it is not a universal answer. Breaking capacity is stated at a voltage and for a frame, and the fault level at the point of installation is what has to be compared. A 10 kA device at the incoming of a small sub-board is comfortable; the same device at a point with 15 kA prospective fault current is not, and no amount of derating in the catalogue fixes it.
There is also a documentation trap: domestic DZ15 sample values cannot be carried across to an export project as if they were IEC ratings. If the old board’s short-circuit study quoted domestic values, it has to be redone against the new device’s IEC data — smaller than it sounds, and much smaller than replacing a welded breaker after a fault.
Accessories and the small parts that stop a project
DZ158 takes the AX-1 auxiliary contact, an IEC/EN 60947-5-1 device with a mechanical life of 10,000 operations and an electrical life above 6,000. It is the part that turns a breaker into a status signal for a PLC or panel lamp, and it is the part that gets forgotten until commissioning. The same contact family serves the DZ158LE variant, so check which variant the replacement is before ordering contacts for it.
The migration sequence that works
| Step | What to record | Why it decides the order |
|---|---|---|
| 1. Survey the existing device | Frame, In, poles, trip type, breaking capacity marked on the front, mounting method | The nameplate is the only reliable record; drawings are often out of date |
| 2. Survey the circuit | Cable size, load current, ambient, enclosure type | The old frame may have been oversized; size by cable and load, not by label |
| 3. Establish the fault level | Prospective short-circuit current at that point | Decides whether a modular device is acceptable at all |
| 4. Decide the pole strategy | Whether the neutral was switched | A 4-pole old device has no direct DZ158 equivalent |
| 5. Check the physical fit | Enclosure width, rail type, busbar pitch, cable lug size | Frame changes force enclosure changes |
| 6. Confirm the certificate | Destination market and the file required there | Domestic certification does not travel with the goods |
| 7. Update the documentation | Panel schedule, labels, single-line diagram | A board with the wrong label on the door is a liability during maintenance |
Done in that order, the project is a bill of materials. Done in reverse — order first, survey later — it becomes a site visit, a return shipment and a conversation about who pays for the enclosure modification.
What to put on the purchase order
Series and frame; rated current and trip characteristic; poles, and whether the neutral is switched; breaking capacity class and the voltage at which it is claimed; accessories by code (AX-1 auxiliary, alarm or shunt where needed); destination country, system voltage and frequency; and the certificate file that destination requires. Add the fault level if it is known — that is the line that turns a shortlist into a selection.
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. As an independent trading company we do not manufacture the device and we are not an appointed distributor of any brand, so the accuracy of the code is the only thing worth selling.
FAQ
Is DZ158 a direct replacement for DZ15?
Only below 125 A and only where the poles and breaking capacity match. DZ158 is an IEC 60947-2 modular line with a 125 A ceiling and 1P to 3P configurations; DZ15 frames run to 250 A and were commonly installed as 4-pole. Above 125 A the replacement is an MCCB, not a larger DZ158.
Can I keep the old 4-pole arrangement?
Not with DZ158. The range publishes 1P to 3P, so a 4-pole old device needs either a family that offers four poles at that current or a 3-pole device with a separate switched neutral — and the second option changes what the isolation point actually isolates.
What breaking capacity should I order?
Whatever exceeds the prospective fault current at the installation point, at the voltage of that system. The 125 A frame is quoted at 10 kA on the H variant, which covers many small sub-boards, but the number has to be checked against the board’s fault level rather than assumed from the old device.
Does the old DZ15 certificate help with export documentation?
No. The ratings in the domestic catalogue are quoted on a 220/380 V basis and against national standards, so they do not answer an importer’s question in another market. The CCC mark is a Chinese market requirement and should not be presented as an export qualification.
What accessory do I need for a status signal?
The AX-1 auxiliary contact, rated under IEC/EN 60947-5-1 with a mechanical life of 10,000 operations and an electrical life above 6,000. Order it with the breaker: it is a code on the order, not a part the installer can improvise.
Related: NB1-63 miniature circuit breakers · MCB range overview · MCCB range overview · How to read an MCCB datasheet · Shunt, undervoltage and auxiliary accessories · Cross-reference an existing breaker · How we verify genuine product · Request a quotation