Module offline (open circuit)
A single module is not exporting power while the rest of its string keeps operating. The whole panel runs warm because its bypass diodes carry the string current around it.
Thermal signature
One complete module appears uniformly warmer than every neighbour in the same string, with an even temperature across the full face rather than a hot patch. The rest of the string looks normal, which distinguishes it from a string-level outage.
Typical ΔT
2–8 °C above neighbouring modules, uniform across the whole module (typical industry interpretation aligned with IEC TS 62446-3).
What causes it
- All substrings bypassed — three conducting or shorted bypass diodes
- Internal cell-interconnect ribbon failure inside the laminate
- Junction-box failure (burnt terminals, detached leads)
- Faulty or unmated module connectors within the string
Power impact
The module's full output is lost while the fault persists, plus a small additional mismatch penalty on the rest of the string. A persistent whole-module outage rarely recovers on its own.
Recommended action
Fix: within 30 days
Schedule repair within 30 days. Verify on site with a clamp meter and open-circuit voltage test, inspect the junction box and connectors, and replace the module if the fault is internal to the laminate.
Frequently asked questions
How is an offline module different from an offline string?
Scale and mechanism. An offline string means the whole series circuit is broken and nothing in it produces. An offline module means one panel has dropped out while its bypass diodes let string current continue around it — the string still produces, minus that module.
Can an offline module fix itself?
Occasionally, if the cause was a temporary condition such as severe shading engaging all bypass diodes. But a module that appears offline under good, unshaded test conditions almost always has a hardware fault — diodes, interconnects or junction box — and needs physical attention.
Related anomalies
Suspect module offline (open circuit) on your site?
Fly the site, upload the thermal frames, and get every module graded against this taxonomy — severity-ranked, with flagged imagery and per-module locations. Quote your site size in seconds.
ΔT figures and abnormality classes on this page describe the typical industry interpretation aligned with IEC TS 62446-3 — indicative engineering guidance, not normative text from the specification. Temperature differentials are only meaningful when captured at ≥600 W/m² irradiance (per the TS) and verified on site before repair work.