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Unspecified•Microinverter

Analysis by Marcus & Team

Unspecified Microinverter DC Overvoltage Error 18xAB

Troubleshooting DC Overvoltage (Error 18xAB) in a residential microinverter system. Diagnose causes, ensure NEC compliance, and prioritize safety.

Frequently Asked Questions

•What is the typical lifespan of a microinverter?

Microinverters typically have a lifespan of 15-25 years, which often matches or exceeds the warranty period.

•How does temperature affect PV panel voltage?

PV panel voltage increases as temperature decreases and decreases as temperature increases. Consult the panel's datasheet for the temperature coefficient.

•What are the NEC requirements for rapid shutdown of PV systems?

NEC 690.12 requires rapid shutdown of PV systems to de-energize conductors within a specified distance of the array. This usually involves a rapid shutdown switch that disconnects the PV panels from the inverter.

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Marcus leads the technical research department at Storage Faults. Together with a team of systems analysts, he specializes in translating complex solar storage error codes into actionable diagnostic steps for the US market.

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Observed Symptoms:

The microinverter reports a 'DC Overvoltage' error (Error 18xAB), indicated by a flashing LED, an error message in the monitoring app, or a complete shutdown of the affected microinverter.

Why This Happens:

Open circuit voltage (Voc) of the PV panel exceeding the microinverter's maximum DC input voltage rating, especially under cold temperatures.
Faulty PV panel with abnormally high voltage output.
Incorrect PV panel wiring configuration (series connections where parallel is required).
Microinverter hardware failure: Damaged DC-DC converter or voltage sensing circuitry.
Grid voltage surge impacting the AC side and reflecting back to the DC side.
Environmental factors: Extreme cold increasing Voc; shading reducing power but not voltage.

Safety Warning:

High DC voltage is present in PV systems. Always disconnect the DC power source before working on any components. Arc flash hazards exist when disconnecting live DC circuits. Only qualified electricians should perform electrical work on solar PV systems. Adhere to all applicable NEC and local electrical codes.

Step-by-Step Fix:

1

*Safety First**: Ensure the PV array DC disconnect is switched OFF before inspecting any wiring or components. Follow NEC 690 guidelines for safe DC disconnecting procedures. Verify proper Rapid Shutdown System (RSD) operation per NEC 2017/2020.
2

*Verify PV Panel Specifications**: Check the PV panel's datasheet for Voc and compare it to the microinverter's maximum DC input voltage rating. Consider temperature coefficients; Voc increases at lower temperatures. Use an IR thermometer to assess panel temperature.
3

*Measure PV Panel Voltage**: Using a calibrated multimeter, measure the DC voltage at the microinverter's input terminals with the PV disconnect OFF then ON. Compare the readings to the expected Voc from the panel datasheet under the current environmental conditions. If voltage exceeds the rated maximum, the panel is likely overvolting the microinverter.
4

*Inspect Wiring and Connections**: Check for loose or corroded connections, damaged wiring, and proper polarity at the PV panel and microinverter terminals. Use a clamp meter to check for current flow after voltage verification.
5

*Isolate the Fault**: If multiple microinverters are connected, disconnect the suspect microinverter and test with a known good PV panel. If the error persists, the microinverter is likely faulty. If the error disappears, the original PV panel is suspect.
6

*Microinverter Replacement**: If the microinverter is faulty, replace it with a new unit that is compatible with the PV panel. Ensure proper grounding and AC/DC connections.
7

*Grid Voltage Monitoring:** Use a power quality analyzer to monitor AC grid voltage. High grid voltage can stress microinverters and potentially contribute to overvoltage errors. Consider installing a surge protection device (SPD) on the AC side.

How It Works:

Microinverters convert DC power from individual solar panels to AC power. They incorporate MPPT to maximize energy harvest and anti-islanding protection to disconnect from the grid during outages. DC overvoltage protection is essential to prevent damage to the microinverter's DC-DC converter stage and downstream components. The microinverter monitors the DC voltage from the PV panel and triggers the error when it exceeds a predefined threshold (typically related to the maximum voltage rating of internal components).

Technical Recommendation:

Some microinverters have a service menu accessible via a specific key combination on the gateway or through a direct connection. This menu may provide detailed voltage and current readings, as well as historical error logs, which can aid in diagnosing the root cause of the DC overvoltage error.

Preventative Care:

Regularly inspect PV panel and microinverter wiring for corrosion or damage.
Monitor microinverter performance through the monitoring app and promptly address any error codes.
Perform periodic firmware updates for the microinverter to ensure optimal performance and bug fixes.
Consider temperature effects on PV panel voltage during system design and selection of components.
Ensure proper ventilation around microinverters to prevent overheating.