Junction box inspection

Junction box inspection means checking the module junction box by eye and with a thermal camera. It is used together with diode checks, IV tracing and insulation checks when damage is suspected. For bypass diode failure, junction-box checks are combined with IV curve signatures, infrared thermography and visual searches for burn marks to find diodes that are open or shorted. Visual inspection is the usual way to find junction box failures, such as boxes that are open, badly bonded to the backsheet, poorly wired, loose, oxidised or corroded. Heat from a failed bypass diode can deform or burn the junction box, so burn marks and melting on the box are key signs. An infrared camera can find higher resistance or mismatch in the box. A box that runs hotter than the others may point to a cold solder joint. Some faults cannot be found this way. An open connection that only matters under shade stays hidden without shading or a night reverse-bias string test, and a failed diode cannot always be told apart from a bad joint without opening the box destructively. For safety, remember that parts inside DC boxes fed by a PV array may still be live after isolation. Isolate any module that shows arcing or burn evidence. If one junction box failure is found, test all modules because the fire risk is high.

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• sentence 4: support check: partial - Heat from bypass diode failure deforming or burning the box is stated, but 'melting' and 'key signs' are not. -->