Short answer: a circuit breaker entering Mexico is cleared on a NOM certificate issued against NOM-003-SCFI-2014, the electrical safety regulation, and marked under the NOM-106 labelling rules. The certificate is held by a Mexican legal entity — the importer, or a Mexican subsidiary of the brand — and it is tied to specific models, not to a product range in general. Two grid facts then decide the order: most Mexican residential and light-commercial systems run at 127 V, 60 Hz, with 220 V available phase-to-phase for larger loads, and 60 Hz is not a detail you can wave away on anything that contains a coil.
This page sets out what NOM actually is, who may hold it, how the 127/220 V grid changes the device you should be quoting, and the failure modes that hold containers at the port. It is written from the position of an independent trading company — not a manufacturer, and not an appointed distributor of any brand — so certificates and test evidence are always stated per exact ordering code, never for a whole family.
NOM is a certificate, not a label you buy
Buyers new to Mexico often talk about “getting the NOM sticker”. That framing causes most of the problems, because the sticker is the last and least important part of the chain. Three things have to be true before a breaker can be sold in Mexico, and they belong to three different parties.
The first is a certificate of conformity to NOM-003-SCFI-2014, the Mexican safety specification for electrical products. It is issued by an accredited certification body and it names specific models. The second is NOM-106 marking, which governs what has to appear on the product and its packaging: the NOM mark itself, the identification of the certification body, and the importer’s details. The third is the commercial identity of the importer, which has to match the party named in the certification file — a point that trips up buyers who switch importer between the sample order and the production order.
Clearance reads the certificate, not the invoice.
| Element | What it actually is | Who holds or applies it | Where it fails |
|---|---|---|---|
| NOM certificate | Type conformity to NOM-003-SCFI-2014, issued per model or model family | A Mexican legal entity — importer or Mexican subsidiary | The model list on the certificate drifts from the variants actually shipped |
| NOM-106 marking | Label content rules: mark, certification body identification, importer details | Applied at the factory or at packing, on behalf of the holder | Missing or non-compliant label, or Spanish information absent |
| Importer identity | The party accountable to the authority, tied to its Mexican tax registration | The Mexican importer | Order placed through a different entity than the one on the file |
| Test evidence | The laboratory reports the certificate rests on, under the NMX-J series | Testing laboratory and certification body | Report predates a design change, or tests a different variant |
Who can hold it
The holder must be established under Mexican law — normally the importer, selling under its own responsibility, or a Mexican subsidiary set up by the brand. An overseas exporter cannot hold a NOM certificate in its own name, so the certificate is not a document a factory hands over like a test report: it is a relationship between the Mexican party and the certification body.
When a supplier says “we have NOM”, one of three quite different things is meant: the models are already on someone’s certificate, a Mexican customer holds one that could be extended to cover them, or a certification project could be started. Three timelines, three levels of certainty, and the difference only shows up at the port.
What the type test reads
NOM-003-SCFI-2014 is the umbrella regulation. The test basis underneath it sits in the NMX-J series of Mexican standards, which for wiring accessories and protective devices maps onto the IEC family with national deviations rather than copying it. Switches, for example, are tested against NMX-J-005-ANCE; for breakers the applicable part of the series is confirmed model by model with the certification body, because the mapping is not uniform across device types.
The certification bodies buyers will meet are ANCE and NYCE, with UL’s Mexican operation also active in the sector. An IEC 60898-1 or IEC 60947-2 report is the fastest route to a technical file, but it is evidence, not a certificate: the Mexican scheme runs its own evaluation, on the model it is given, at Mexican voltages and frequencies.
The grid: 127 V, 60 Hz, and a second voltage behind it
Mexico is not a 230 V market with a different plug. Residential service is typically a three-wire 127/220 V arrangement: 127 V from either live conductor to neutral, 220 V between the two live conductors. Industrial and larger commercial installations move to 220 V and above, including three-phase. The device choice follows from that.
| System | Voltage | Frequency | What it changes for the breaker |
|---|---|---|---|
| Residential branch circuit | 127 V live-to-neutral | 60 Hz | One-pole device. The rated voltage must cover 127 V with margin, and the calibration has to be read at the ambient of a Mexican board, not a European one |
| Residential two-pole load (dryer, range, small A/C) | 220 V live-to-live | 60 Hz | Both conductors are live. A 1P+N device leaves one live conductor unprotected — this is a two-pole job, not a neutral-switching one |
| Commercial and light industrial | 220 V single-phase, 220/440 V three-phase | 60 Hz | Breaking capacity is quoted at the system voltage, because Icu falls as voltage rises; a headline kA figure belongs to one voltage only |
| Anything with a coil in it | — | 60 Hz | Contactors, timers and meters are the frequency-sensitive parts. The breaker is not |
The breakers themselves are the easy part of the frequency question. IEC 60898-1 miniature circuit breakers are rated 50/60 Hz, thermal-magnetic operation is essentially frequency-independent, and a standard MCB does not care whether the supply is 50 or 60 Hz. What does care is everything the breaker feeds or sits beside: a contactor coil quoted for 50 Hz will not pull in reliably on 60 Hz, and a timer or meter not specified for 60 Hz misbehaves quietly for a month before anyone notices. We cover that mechanism in contactor coil voltage and 50 Hz versus 60 Hz.
For residual current devices the question is not frequency but system shape. In a 127/220 V installation the choice between RCCB and RCBO, and the pole configuration of each, follows from whether the neutral is a live conductor for that circuit — in split-phase systems it often is. The general argument is in 230 V circuit breakers in 110–127 V markets.
Where orders actually fail
Five failure modes account for most Mexican order problems. None is exotic; all are cheap to avoid at quotation.
- Test report offered as a certificate. The IEC report exists, the NOM evaluation does not, and the buyer has budgeted for neither the audit nor the timeline.
- Holder mismatch. The certificate is held by one importer and the container is cleared by another. A new importer generally needs its own arrangement even for identical goods.
- Model list drift. The certificate covers a family; the shipment contains a variant outside it — a different pole count, a different curve, a different breaking-capacity step. The variant is what customs reads.
- Labelling. NOM-106 mark, certification body identification and importer details, with the Spanish-language information the regulation requires. This is decided at packing, which is late and expensive to fix.
- Catalogue voltage used as system voltage. A 230/400 V headline device quoted into a 127/220 V system gives the wrong pole configuration and an overstated breaking capacity for the actual voltage. The device may still work; the selection is still wrong.
One further point belongs to the application rather than the certificate. IEC 60898-1 devices are calibrated at a 30 °C reference ambient; a metal board in a Mexican summer runs hotter, and every breaker in it carries less current than its rating suggests. Derating is a design decision, not a compliance one, and it is the difference between a board that holds and one that nuisance-trips in August.
FAQ
Do I need a Mexican company to get NOM?
The certificate holder must be established under Mexican law — normally the importer or a Mexican subsidiary of the brand. An overseas exporter cannot hold it in its own name.
Is an IEC 60898-1 test report enough for NOM?
No. It is the strongest input to the technical file and it shortens the work, but the Mexican scheme issues its own certificate after its own evaluation. Treat the report as evidence and the certificate as a separate document with a separate holder.
Can a 230 V MCB be used on a 127 V system?
Electrically the device is rated above the system voltage, so it will operate. The selection questions are elsewhere: the pole configuration in a 127/220 V three-wire system, the breaking capacity at 127 V, and whether the device is the model covered by the certificate. A device that works is not automatically admissible.
Does 60 Hz matter for miniature circuit breakers?
No. IEC 60898-1 MCBs are rated 50/60 Hz and thermal-magnetic tripping is essentially frequency-independent. It matters for contactor coils, timers and meters.
How long is a NOM certificate valid?
Validity is set by the scheme the certificate was issued under, with surveillance obligations attached; the expiry date printed on the certificate is the only one that counts. Renewal is the holder’s responsibility, and a lapsed certificate stops the next shipment rather than the current one.
What to send us for a quotation
Model or ordering code · quantity · destination city in Mexico · the system — 127 V single-phase, 220 V single-phase or 220/440 V three-phase, 60 Hz · pole configuration · whether a NOM certificate exists for the model and who holds it · breaking capacity needed at the system voltage. You get unit price, packing data and the certificate evidence for the exact ordering code. Request a quotation.
Related: 230 V breakers in 110–127 V markets · Which certificate does my country require? · Miniature circuit breakers · Markets we serve · Cross-reference