“IP68 junction box with compatible connectors” is not a controlled PV module bill of materials. The electrical tail includes the junction-box model, internal connections, bypass diodes, sealing system, output cables, lead lengths, connector manufacturer and polarity. A change to any of those items can affect qualification, installation and service records.
This guide helps module buyers define evidence for that assembly without requesting unnecessary proprietary information. It does not authorize opening or repairing a junction box, select a module or approve an electrical design. Use the PV connector compatibility guide for the separate rules governing a mated connector pair.
Define the complete electrical-tail BOM
Begin with the full module model and drawing revision. Then request the junction-box manufacturer, exact model or controlled type, rated voltage and current, temperature category, enclosure protection evidence and applicable certification file. Identify whether the design uses one central box, split boxes or another arrangement, and record the number and placement of cell-string connections.
For the bypass diodes, request a controlled identity or approved specification, diode count, ratings used in the qualified design, thermal evidence and approved alternatives. The buyer needs enough identity and change control to connect the delivered configuration with the module evidence without demanding confidential design details.
For each output lead, state cable type and standard, conductor cross-section, temperature rating, polarity, marking and length. Define the connector manufacturer, product family, exact plug and socket models, assembly method and any locking accessory.
Avoid umbrella descriptions such as MC4 compatible, TÜV connector, equivalent diode or custom cable. They do not identify the delivered interface. If more than one approved BOM is permitted, require each alternative to be listed and traceable rather than allowing an unrestricted “or equivalent.”
Use junction-box standards within their scope
The IEC catalogue currently lists IEC 62790:2020, Edition 2.0, with a stability date of 2030. Its public scope covers safety and construction requirements and tests for junction boxes up to 1,500 V DC used on PV modules. The edition added a bypass-diode thermal-test procedure and a reverse-overload-current test. This supports requests for applicable component evidence, but the public scope does not prove that an unnamed box is certified or qualified with the quoted module. IEC 62790 official publication record.
IEC 61215-2:2021, Edition 2.0, remains the edition displayed in the official IEC catalogue on the source-check date. Its published changes identify MQT 18 as the bypass-diode thermal test and state that three selected diodes, rather than all diodes, are tested. Its listed stability date is 2026, so the RFQ should name the exact edition and recheck publication status when the procurement package is released. IEC 61215-2 official publication record.
For a North American evidence path, UL marks UL 3730 active, last revised April 2, 2025. Its public scope covers junction boxes attached to PV modules and panels for factory or field wiring and notes that they may include wiring leads or PV connectors. Treat the junction box, leads and connectors as identified elements of the delivered configuration instead of assuming the box certificate covers every cable or connector substitution. UL 3730 official scope and revision record.
Keep the bypass diode and string fuse functions separate
A bypass diode is connected across a cell string. During partial shading or a hot-spot condition, it can provide an alternate current path around the affected section. It is not the overcurrent protective device for the PV string.
JinkoSolar's A1.8 global installation manual, dated May 2026, says that for the module families it lists, bypass diodes are associated with cell strings, are not overcurrent protection and should not be accessed by opening the module junction box. Suspected replacement needs are directed back to JinkoSolar. JinkoSolar Global Installation Manual A1.8, bypass-diode section.
LONGi's 2026 DGBG module manual gives the same boundary for the module families it covers: the bypass diode is connected in parallel with a cell string, can operate during a hot-spot condition, is not an overcurrent protection device and should not be accessed by opening the box in the field. The manual directs suspected defects to LONGi. LONGi DGBG PV Module User Manual, April 2026.
Use those manufacturer statements to prevent two procurement errors. First, do not delete string overcurrent review because the module contains bypass diodes. The PV string fuse sizing guide covers that separate decision. Second, do not write a field-repair instruction that conflicts with the selected module manual. Request the manufacturer’s service and disposition process instead.
Turn lead length into an inspectable drawing
Cable length affects array routing, connector reach, bend condition and the need for extensions. “Standard lead” or “one metre cable” is ambiguous unless the measurement datum and connector inclusion are defined.
State whether length is measured from the box, cable exit, strain-relief edge or another datum. Define connector inclusion, positive and negative lengths, tolerance and allowed routing. Identify portrait, landscape, staggered-row or tracker routing that the lead must support.
A JinkoSolar module datasheet illustrates why this detail belongs in the RFQ. It lists an IP68-rated junction box, 4.0 mm² output cables, positive and negative leads of 400 mm and 200 mm “or customized length,” and connector choices shown as “JK03M/MC4/Others.” Those options may be useful in a product family, but they are not a final purchase identity. A released order should select one actual connector system and one controlled lead drawing. JinkoSolar 430–455 W module datasheet.
Check cable routing against the module and mounting drawings. Leads should not depend on pulling the cable at the box, forcing a tight bend, resting a connector on the roof or mixing connector brands to gain reach. Keep connector current and temperature limits linked to the PV connector derating guide.
Control sealing, attachment and external interfaces
Identify the qualified junction-box attachment and sealing system by controlled specification. Records may include adhesive or encapsulant identity, application and cure controls, surface preparation, production inspection and environmental qualification. Do not invent a universal pull force, cure time or IP test.
Define external acceptance checks that do not require opening the box: location and orientation, visible adhesion or seal condition, enclosure damage, cable-exit condition, cable marking, lead length, connector identity, polarity and serial trace. If a hidden internal attribute needs verification, request supplier production or qualification evidence rather than destructive incoming inspection of saleable modules.
Connector identity needs special attention. A plug from one manufacturer and a socket from another may share a general interface appearance without being an approved mated pair. Record the actual two sides that will meet in the field and the supporting instructions. The PV connector contact-resistance guide explains why the completed pair, termination and thermal condition belong in the evidence package.
Compare the critical evidence in one schedule
Use a consistent schedule across suppliers so a generic datasheet does not receive the same completeness score as a controlled module-specific package.
On small screens, swipe or scroll sideways to read every column. Keyboard users can focus the table and use the arrow keys.
| Critical RFQ field | Required supplier evidence | Hold point before release |
|---|---|---|
| Junction box and diode assembly | Exact manufacturer/model or controlled identity, diode count and specification, ratings, certificate and module qualification reference | Generic “IP68 three-diode box” or an unapproved alternative |
| Leads and connectors | Cable standard/type/size, positive and negative lengths with datum and tolerance, exact connector manufacturer/model and polarity | “MC4 compatible,” “others” or “custom length” remains in the final quotation |
| Production and change control | Approved BOM revision, module or serial trace, external inspection plan and prior-approval process for critical substitutions | Supplier may change the electrical tail without documented review |
Require the module datasheet, controlled drawing, certificate schedule and quotation to agree. If the public datasheet lists several connector or lead options, the order-specific record must identify which one will ship. Ask for a sample label, cable marking or other non-destructive identification method so receiving inspection can verify that choice.
Define change notice and service evidence
Require prior notice before a change to the junction box, diode, connector, cable, sealing system, lead length or production site when that change affects the approved evidence. The change package should identify affected module models, old and new controlled identities, reason, qualification or certificate impact, implementation lot or serial range and disposition of existing stock.
Link the electrical-tail BOM to module serial or production-lot records at the project’s required traceability level. This complements the solar panel flash-test and EL traceability guide; flash and image records do not identify the junction-box and connector BOM.
For service, request the module manufacturer’s method for suspected diode, cable, connector or box damage. Define quarantine, diagnosis, replacement and warranty-contact records without promising a repair outcome. Preserve photographs and electrical observations, but do not open the junction box when the manufacturer prohibits it.
Send a PV junction-box evidence RFQ
Send the exact module model, system voltage, current basis, required connector pair, positive and negative cable routes, lead-length datums, environmental conditions and certification needs. Ask bidders to return the controlled electrical-tail BOM, drawing, certificate references, inspection plan and substitution process.
Buyer FAQ
Does an IP68 statement fully define the junction-box assembly?
No. It does not identify the exact box, test conditions, diode assembly, cable entries, connector state or qualified module configuration. Request the applicable report or certificate and controlled part identity.
Is a bypass diode a substitute for a string fuse?
No. The cited module manuals describe the diode as a cell-string bypass during shading or hot-spot conditions and expressly distinguish it from overcurrent protection. Review string protection separately.
Can customized cable length be approved in an email?
Use a controlled drawing or order specification that states the measurement datum, positive and negative lengths, tolerance, connector inclusion, polarity and routing constraints. Link it to the module and BOM revision.
Should an installer open the junction box to replace a suspected diode?
Follow the exact module instructions. The cited JinkoSolar and LONGi manuals direct users not to open the box and to contact the manufacturer or service provider when a diode is suspected to be defective.