Combiner box anomaly
Abnormal heating in or around a DC combiner box — typically a high-resistance termination or a failing protection device carrying the combined current of many strings. Treated as a safety-critical finding.
This class is part of the taxonomy our reports are written in, but our analysis does not currently flag it. The page is field reference for your own review. The eight classes we do flag today, and how well, are on the validation page.
Thermal signature
A localised hot signature at combiner or enclosure positions rather than on module glass: a warm lug, breaker or fuse-holder position standing out against the enclosure, or the enclosure body itself reading well above its surroundings.
Typical ΔT
10–40 °C or more at the affected termination. Because combiner faults sit on high-current aggregation points, they are escalated to the safety class at lower ΔT than module-level findings (typical industry interpretation aligned with IEC TS 62446-3).
What causes it
- Loose or under-torqued lugs and busbar terminations
- Corroded or thermally cycled connections
- Failing breakers, fuse holders or DC disconnects
- String imbalance overloading individual inputs
Power impact
A combiner failure can take every connected string offline at once, and the failure mode — arcing at a high-current DC termination — is a genuine fire hazard. The exposure is measured in whole blocks of the site, not single modules.
Recommended action
Fix: immediate
Act immediately. Have a qualified electrician inspect the combiner: thermographic confirmation at close range, torque check on all terminations, and replacement of any heat-damaged devices. Follow site procedures for working on or isolating live DC aggregation equipment.
Frequently asked questions
Why do combiner findings outrank most module findings?
Current and consequence. A combiner aggregates the output of many strings, so a single failing termination carries far more current than any module connection, and its failure can drop or endanger a whole block of the array rather than one panel.
Can aerial thermography really see inside a combiner box?
Not through a closed metal enclosure — what it sees is abnormal external heating of the enclosure or exposed terminations, which is itself a red flag. The aerial finding is a trigger for a close-range inspection with the enclosure opened by an electrician, not a substitute for one.
Related anomalies
Planning a thermal inspection?
This class (Combiner box anomaly) is not flagged by our analysis today; the page is field reference for your own review. The eight classes we do flag, with their measured performance, are on the validation page. 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.