How to Align Ex Certification of Multi Cable Transit With Enclosure Ex Rating?

A BESS container builder sent me their junction box certificate and asked if the Ex certification of a multi cable transit had to match it. Their auditor had frozen shipment.

Align Ex certification of a multi cable transit with the enclosure Ex rating by matching the protection concept (Ex e, Ex tb, Ex d), gas or dust group, EPL, temperature range, and an IP rating equal to or higher than the enclosure, then following the transit’s certificate installation conditions.

That frozen shipment cost them three weeks. The transit was certified. The enclosure was certified. But the two certificates did not describe the same system. In this article I will walk through how we help buyers avoid that gap, what to ask for, and what happens when nobody asks.

How do I know which Ex certification my cable transit needs to match my enclosure's zone rating?

Every quotation forces a trade-off for us: a module that seals to IP68 costs more rubber than one that stops at IP54. The enclosure certificate decides which one you need.

Read the enclosure's own certificate first. Note its protection concept (Ex e, Ex tb, Ex d), gas group, temperature class, EPL, and IP rating. Your cable transit must be certified for the same concept and group, and its IP rating must equal or exceed the enclosure's.

The mistake I see most often is starting from the transit catalog. The right order is the reverse. Start with the hazardous area classification ¹ of the location. That gives you the zone. The zone gives you the required EPL. The EPL and the enclosure certificate together tell you which protection concept the entry must preserve.

Start from the zone, not from the product

Zone 1 gas areas usually call for EPL Gb. Zone 21 dust areas call for EPL Db. The enclosure manufacturer has already chosen a protection concept to meet that level. Your cable entry system must not break that concept. Here is how the common concepts translate into entry requirements.

Ex and IP are two different questions

Ingress Protection (IP rating) is not the same as the Ex marking. Both matter. A transit can carry a valid Ex eb marking and still fail your project if the enclosure is IP66 and the transit is tested only to IP54. The assembly takes the lower value. In our TSC and TSR module tests we push to IP68 because it removes this argument for most enclosures we see in BESS containers and modular data centers.

Gas groups and temperature classes narrow the choice further

Gas groups and temperature classes appear on both certificates. If the enclosure is marked IIC T6, the transit must cover IIC and its service temperature range must include the enclosure's full ambient range. A seal rated only to a narrower temperature band can harden or relax and open a leak path.

For a flameproof enclosure (Ex d), IEC 60079-14 ³ adds one more layer. Vendor summaries of the standard indicate that barrier-type entries become mandatory in specific cases: cable lengths under 3 m for IIC and IIB plus hydrogen, cable lengths under 0.5 m for IIA and IIB, and enclosure volumes above 2,000 cm³ unless the enclosure certificate says otherwise. A non-barrier elastomeric sealing module is not a substitute for a barrier entry in those cases.

What documents should I request to verify Ex compliance between my MCT and enclosure?

During a factory inspection last year, an auditor pulled one TSC module off our line and asked for its paper trail. We had the IP68 and gas-tight reports ready within minutes.

Request the ATEX or IECEx certificate for the exact MCT model, its installation instructions with X conditions, the IP test report, service temperature data, and a declaration of conformity. Then compare each item line by line against the enclosure's own certificate and instructions.

Paper is what an inspector checks. Not the rubber. So the document set has to be complete and it has to describe the exact model you installed. I have seen buyers receive a certificate for a product family and assume it covers every insert size. It often does not.

The five documents I ask any supplier for

1. The Ex certificate itself. Under the ATEX Directive ⁴ this is an EU-type examination certificate. Under the IECEx System ⁵ it is an IECEx Certificate of Conformity. Check the certificate number, the issuing body, the marking, and the list of covered model codes.
2. The installation instructions. These carry the legal limits: cable diameter range per insert, fill factor, tightening torque, approved lubricant, and minimum cable length. ATEX and IECEx assessments test the product with those exact torques and lubricants. Change them and the certificate no longer describes what you built.
3. The IP test report. Ask for the report, not the number on the datasheet. For Ex tb applications you want dust-tight IP6X evidence. For Ex e you want the report to match or exceed the enclosure rating.
4. Service temperature data. The MCT's certified temperature range must fully cover the enclosure's ambient and internal operating range.
5. The declaration of conformity signed by the manufacturer, not by a trading company.

U component versus equipment certificate

This is where most confusion sits. A certificate ending in "U" means the transit is an Ex component. It is not complete equipment. It only becomes compliant inside an assembly that is itself certified or assessed. A full equipment certificate can carry an "X" suffix, which means specific conditions for safe use apply. Those X conditions on the enclosure must not conflict with the installation limits on the transit.

What we put in our own package

Our modules are tested for IP68 and for watertight and gas-tight sealing between 0.01 and 0.4 MPa. We send those reports on request, together with the model cross-reference table and CAD or STEP files. For Ex projects I tell buyers plainly which report applies to which module size. A general brochure claim is not evidence. A report with a serial number and a test date is.

Can I switch to a second-source MCT supplier without losing my enclosure's Ex certification?

A European switchgear buyer told me his real fear was not price. It was an auditor asking why the transit brand in the panel no longer matched the drawing.

Yes, if the second-source MCT carries its own Ex certificate for the same protection concept, gas or dust group, temperature range, and an equal or higher IP rating, and its installation conditions fit your enclosure. If the enclosure certificate names a specific transit, you need the enclosure manufacturer's approval.

Switching supplier is a legitimate engineering decision. It saves money. It protects lead time. But it must be done in the right order, and the order depends on how the enclosure was certified in the first place.

Three situations, three answers

Case one: the enclosure certificate is silent on the entry device. This is the most common case for Ex e and Ex tb junction boxes. The certificate requires the installer to use a suitably certified entry that preserves the IP rating. Here you are free to choose any transit that meets the matching rules from the first section. Document the match in your drawing and FAT checklist.

Case two: the enclosure certificate lists an approved entry by type. Here a substitute must be equivalent on every listed parameter. Ask the enclosure manufacturer to confirm in writing. Most will do so once they see matching certificates.

Case three: the transit was part of the enclosure type test. This is typical for a flameproof enclosure (Ex d). A change here is a change to the certified equipment. It needs reassessment by the notified body ⁶ or certification body. Do not substitute without it.

How we make qualification easier

Our sealing modules are dimensionally compatible with common 120-frame standards. They drop into the existing frame cutout. That solves the mechanical question. The certification question still has to be solved with documents, and I do not pretend otherwise. So our second-source process for an Ex project runs like this:

1. You send us the existing model code and the enclosure certificate.
2. We return a cross-reference table showing the DEWIN equivalent and its dimensions.
3. We ship free validation samples so your engineers can fit-check the frame and cable diameters.
4. We send the test reports for IP68 and gas-tight sealing, plus the module's applicable certificate documents.
5. Your team runs the line-by-line comparison against the enclosure certificate and X conditions.
6. The approved combination goes onto the drawing and into the FAT and SAT checklist.

The cost side matters too. Buyers typically see 40 to 60 percent lower module cost against the original brand. That is only useful if the certification chain stays intact. Our ISO 9001 and IATF 16949 systems and BV-approved factory status exist so that the paperwork holds up when the auditor arrives.

What happens to my enclosure's Ex rating if the cable transit sealing doesn't match?

The hardest lesson from our early years was this: a seal that passes on our test rig can fail in the field if the installer uses the wrong cable diameter.

A mismatched cable transit downgrades the whole enclosure. The assembly takes the lower IP rating, the Ex marking becomes invalid for that installation, and the enclosure can no longer be signed off under IEC 60079-14. Gas, dust, or flame can then enter through the entry point.

A mismatch is not one problem. It is several, and they show up at different times. Some appear at installation. Some appear years later during a periodic Ex inspection. I want to lay them out clearly, because the procurement decision made today sets up every one of them.

The failure modes and their consequences

Cold flow and time

Cable insulation materials creep under sustained compression. Engineers call this cold flow. A seal that was tight at commissioning can relax over months as the cable jacket deforms. In a flameproof enclosure (Ex d) this matters most, because the flame path depends on maintained compression. Step-core EPDM helps here because the layers are peeled to the exact cable size, which keeps the compression even. But the installation instructions still set the inspection interval, and a second cable pulled through later can undo the original seal.

Heat and the T-code

A high-density transit is a large block of rubber in the enclosure wall. It can act as an insulator. That changes the internal temperature rise of the enclosure. The enclosure's temperature class was assigned with a specific heat path in mind. For dense bundles in a small enclosure I recommend a simple thermal check to confirm the T-code still holds. This is one reason we ask for the cable schedule before quoting a fill arrangement.

Mechanical strength and inspection

IEC 60079-0 defines high-risk mechanical danger locations. The transit frame must meet the impact requirement for the enclosure's location, not just the enclosure body. Our welded galvanized frames are built for this, but the drawing must record the mounting position.

Finally, think about the inspector. Ex inspections under IEC 60079-14 and the related inspection standards check that the installed parts still match the documents. Digital asset tags on individual transit blocks let an inspector confirm the module certificate without dismantling the assembly. I encourage buyers to record the module code, insert sizes, torque, and installation date at commissioning. It costs minutes. It saves the enclosure's rating when the inspector arrives.

Conclusion

A certified transit is only compliant when it preserves your enclosure's exact protection concept and IP rating. Match, document, and verify, or the whole enclosure loses its Ex status.

Footnotes

1. The IECEx portal provides authoritative information on hazardous area classification and international compliance standards. ↩︎

2. The International Electrotechnical Commission’s homepage, the body responsible for global flameproof enclosure standards. ↩︎

3. Official site of the IEC, providing access to international standards like IEC 60079-14 for explosive atmospheres. ↩︎

4. Official European Commission page for the directive governing equipment used in explosive atmospheres. ↩︎

5. Official website for the international IECEx system for certification of equipment in explosive atmospheres. ↩︎

6. EU Commission resource explaining the role of notified bodies in assessing equipment for the European market. ↩︎