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g/solar • Posted by u/solar_steve •

SolarEdge production dropping on one string — optimizer issue or something else?

Residential 8kW system, SolarEdge HD-Wave inverter, 24 LG 335W panels. One string of 12 panels is producing about 30% less than the other string of 12, based on the monitoring data.

I pulled optimizer data and one optimizer in the low-producing string is showing significantly lower voltage — about 18V vs 38V for the others. The optimizer isn't faulted, just low production.

Panel IV curve looks normal on the optimizer data. Suggestions?

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u/string_inverter_sarah •

Also verify the panel itself with a thermal camera or shade test. A panel with one bad cell string will show a normal IV curve shape but lower than expected maximum current. On an LG 335W, a shaded or failed bypass diode can cause exactly what you're describing.

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u/battery_backup_brad •

An optimizer showing 18V with a normal IV curve often means a high-resistance connection upstream or downstream of that optimizer. Check the connectors at that optimizer — both MC4 connections. SolarEdge optimizers can be over-power-limited if they're getting voltage but fighting a restriction.

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u/roof_mount_ray •

Any shading hitting that string that's not hitting the other? Even a 10-minute shadow per day can significantly drag down an optimizer's daily production if it coincides with peak irradiance hours. Look at the panel orientation relative to any nearby obstructions.

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