A hotspot is a part of a module, connection or other component that shows up hotter than its surroundings in an infrared image taken while the system is under load. Scan in clear, stable weather with high irradiance and the inverter running. Avoid reflections from clouds and nearby objects, then compare the module with its neighbours in the same string. A hot cell or a hot localized area points to cracked cells, broken front glass, solder bond or cell interconnection faults, or mismatch that forces cells into reverse bias. Hot junction box terminals, connectors, cables or fuse clamps usually mean a loose or poor electrical connection, not a fault in the cells. A warm substring or a heated bypass diode suggests the diode is conducting. Check first for shading or debris on that module, and suspect a bad module or a shorted diode if none is found. Treat one thermal image as a screening result only. Confirm it with string current, the IV curve shape and visual inspection, and add EL imaging where cell damage is suspected. Raise the priority when the hotspot appears again on later inspections, when several modules in one string show it, or when there is a safety risk, because strong hotspots can lead to smouldering fires.
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observed_asc1 drafted · lead Localized IR hotspot
Localized heating during loaded operation; linked to poor solder joints, cracked cells, poor connections or severe mismatch inside a module.
sec=h4 h=a46a7d318434sec=h8 h=9f1fbad653f1sec=h13 h=fd7deb3c6e41c2 drafted · lead Hot cell in IR image
Broken front glass often leaves broken hot cells in the damaged module; cracked cells also show as hot cells.
sec=h4 h=a46a7d318434sec=2.3.1.1 h=767c056a514ac3 verified · fact Warm substring in IR image
Inactive substrings or modules look warmer than active parts, but the difference is small and grows with irradiance, so low-irradiance scans can miss it.
sec=h4 h=a46a7d318434sec=h13 h=fd7deb3c6e41sec=h54 h=e6e5453ce084verified by: joshuahamsaverified on: 2026-10-20
c4 verified · fact Hot electrical connection
Covers junction box terminals with loose internal connections, overheated DC connectors, cables and fuse clamps.
fig=7 h=eb7dd22abf25sec=2.3.1.6 h=50d53aeafc51sec=5 h=fc0f2dc6c73fverified by: joshuahamsaverified on: 2026-10-20
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