Buying · standards in plain English
IEC vs UL circuit breakers: what US sites need to know
European-built turbines, lines and switchboards arrive with breakers built to IEC 60947-2. Most US distribution equipment uses breakers listed to UL 489 or UL 1066. Here is what the difference means, why your site has IEC frames, and what a repair does and doesn't change.
- IECIEC 60947-2
- UL, molded caseUL 489
- UL, power breakersUL 1066 · ANSI C37.13
- Our roleRepair as designed, no re-listing
The short answer
Two families of standards for the same job
An IEC breaker and a UL breaker do the same job: carry current, open on overload and short circuit, and survive doing it. They are designed, tested and rated to different standards, and the ratings are stated in different ways. You can't read one nameplate as if it were the other.
A repair doesn't move a breaker from one family to the other. An IEC breaker comes back an IEC breaker, with the same frame, ratings and trip characteristic. A UL-listed breaker comes back the same model, repaired and tested, but we don't re-certify its listing.
That is usually exactly what you want: the breaker your equipment was designed and accepted with, working as it did when new.
The standards
Which standard covers which breaker
| Standard | What it covers | Where you'll meet it |
|---|---|---|
| IEC 60947-2 | Low-voltage circuit breakers of all kinds, air and molded case, in one standard. | Europe and most of the world. The Emax, Masterpact, 3WL and IZM in European-built equipment. |
| UL 489 | Molded-case circuit breakers, including insulated-case breakers. | Most US panelboards, switchboards and feeders. |
| UL 1066 with ANSI C37.13 | Low-voltage AC power circuit breakers used in enclosures. UL 1066 is the safety standard; ANSI C37.13 sets the ratings and performance. | US switchgear incomers, ties and large feeders. UL-listed versions of Emax, such as the "-A" models. |
| IEC 60947-4-1 | Contactors and motor starters, rated by utilization category such as AC-3 (motors) and AC-1 (resistive loads). | The LC1F, AF and 3RT contactors in European machinery. An LC1F780 is rated 780 A AC-3 and 1600 A AC-1. |
The differences
What actually differs
The detail fills hundreds of pages. These are the points that matter when an IEC breaker sits on a US site.
Voltage
IEC equipment is commonly rated at 400, 415 or 690 V. US equipment is built around 208, 240, 480 and 600 V systems; the UL Emax plate above shows ratings at 254, 508 and 635 V. A breaker rated for 690 V IEC service has no direct UL counterpart at that voltage.
Short-circuit ratings
IEC states an ultimate breaking capacity (Icu), a service breaking capacity (Ics) and a short-time withstand (Icw) for a stated time. UL and ANSI state an interrupting rating at the listed voltage and, for power breakers, a short-time rating. The numbers aren't interchangeable.
Testing and loading
The test sequences, enclosure assumptions and continuous-load assumptions differ. Many UL 489 breakers are applied on the basis that continuous load stays within 80% of rating unless marked 100% rated. Your engineer will know which applies.
Why your site has IEC frames
The equipment came from Europe, so did its breakers
European turbine makers, machine builders and switchboard designers specify the breakers they know, built to the standard they work to. Turbines from Vestas, Siemens Gamesa, Nordex and the older GE platforms built on European designs arrived with IEC breakers and contactors, and the main breaker in a turbine base is typically a 690 V unit. Production lines, presses and compressors often arrive with a complete IEC switchboard.
That equipment was accepted onto your site by some route: as part of a listed or evaluated assembly, through a field evaluation, or by the approval of the authority having jurisdiction (AHJ). We can't tell you which route applied at your site. Your records or your engineer of record can.
What a repair does
It keeps the breaker as designed and installed
- Same frame, same rating, same trip unit type, same settings
- Wear measured against OEM limits and worn parts replaced
- Every enabled protection element proven by secondary injection against the published curve
- Contact resistance and insulation resistance recorded pole by pole
- Back into the same cradle, with the same busbar and secondary connections
We don't up-rate a breaker, convert it from IEC to UL, or apply or renew a UL mark. How we test.
UL-listed variants
Some IEC ranges also come in UL versions
Several of the European ranges were also built in UL-listed versions for the North American market. ABB's Emax "-A" models are one example, and Masterpact NW and NT also came in UL versions. We repair these too.
Our sample ACB certificate is for an ABB SACE Emax E3N-A 20, a 2000 A UL-listed power circuit breaker built to ANSI C37.13. It came in with a broken charging handle, a missing CLOSE button and corrosion throughout, and went back rebuilt with new coils and a full injection test.
We repair and test the breaker. We don't re-certify UL listings. If your site needs a listing decision on a repaired breaker, that is a question for your AHJ or engineer of record.
Every unit we return carries our asset label with its service date, so your records show when it was last overhauled and by whom.
The alternative
Swapping an IEC breaker for a UL one
Replacing an IEC breaker with a UL-listed one sounds tidy. In practice it rarely drops into the same space. A different breaker usually means a different depth and footprint, a different cradle, different busbar connections and a different secondary connector. The cell or the busbars often have to change.
The trip unit changes too, so the protection settings and the coordination study need revisiting. On a turbine, the controller's I/O may need remapping. Changing the assembly may also bring its own approval question.
Sometimes that project is worth doing. Often it isn't, when repairing the original keeps everything as it was accepted. Talk to your engineer of record before you decide, and send us the nameplate so you know what the repair route looks like.
This page is a plain-English overview, not legal or code advice. The standards and the electrical code that apply to your site, and how your AHJ applies them, are for your engineer of record and AHJ to confirm.
Ranges we repair
FAQ
IEC and UL questions
Is an IEC breaker allowed on a US site?
Many US sites run IEC breakers that arrived inside European-built equipment and were accepted with it. Whether a particular installation is acceptable is decided by your AHJ, so check with them or your engineer of record if you're unsure.
Does repairing an IEC breaker change its status?
A repair keeps the breaker as designed: same frame, ratings, trip characteristic and settings, proven by injection test. It doesn't convert it to a UL product or change its ratings.
Do you repair UL-listed breakers?
Yes, including UL-listed Emax "-A" versions. Our sample certificate is for a UL-listed Emax E3N-A. We repair and test the breaker; we don't re-certify UL listings.
Why are so many European breakers rated 690 V?
690 V is a standard IEC low-voltage level, used widely in wind turbines and large drive systems. US systems are built around 208, 240, 480 and 600 V, so a 690 V IEC breaker has no direct UL equivalent at that voltage.
Can we replace our IEC breaker with a UL one instead?
Sometimes, but it usually means cell or busbar changes, a new cradle and secondary connections, and a revised coordination study. Talk to your engineer of record before deciding.
Send us the nameplate
A photo of the nameplate and the fault is enough for a first answer. We reply the same working day with a recommendation and a price for diagnosis and freight.