Junction box

The junction box usually sits on the back of the module and protects the connections between the output terminals and the cell string interconnectors. It also holds the bypass diodes, which switch on to protect the cells when shading or uneven irradiance causes a strong mismatch. Junction boxes link modules to each other, so when one fails it can cut performance badly and cause internal arcing and even fire. Look for a weathered, brittle, cracked, warped, melted or burned housing or lid, an open or loose lid, a box shifted or detached from the backsheet, yellowed adhesive, and damaged or missing seals. A defective or detached box lets in moisture, which corrodes the interconnections, and a loose box puts mechanical stress on the contacts inside it. Failure modes that affect this part include Junction Box Failure, Junction Box Interconnection Failure and Bypass Diode Failure, and heat from a failed diode can deform or burn the box. Find faults with visual and infrared inspection, diode checks, IV tracing and insulation checks, and replace the module instead of repairing the box, because repairs can lead to new fires. IEC 62790 sets design and test requirements for PV module junction boxes, including a minimum IP55 protection rating.

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• sentence 7: support check: partial - Visual and infrared inspection, IV tracing, and the advice to replace the module because repairs can cause fires are all stated, but the passages mention no diode checks or insulation checks (u3's detection_method does mention verify diode behavior and insulation checks, so it is covered there). -->