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Analysis by Marcus & Team

SolarEdge Inverter: String Voltage Too High Error

Troubleshoot SolarEdge "String Voltage Too High" errors in residential solar systems. Learn causes, solutions, prevention, and safety tips for your hybrid inverter.

Frequently Asked Questions

•How does temperature affect the string voltage in a SolarEdge system?

Lower temperatures increase the open-circuit voltage (Voc) of PV modules, potentially causing the string voltage to exceed the inverter's maximum input voltage.

•What are the NEC requirements for rapid shutdown in residential solar systems?

NEC 690 requires rapid shutdown systems to de-energize conductors within the array boundary to 30V within 30 seconds of initiation. For areas outside the array boundary, the voltage must be reduced to 80V within 30 seconds.

•How often should I inspect my SolarEdge system for potential issues?

A visual inspection of wiring, connections, and system components should be performed at least annually. More frequent inspections may be necessary in harsh environments.

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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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Common Causes:

Defective optimizer causing abnormally high voltage output.
Incorrect string configuration (too many modules in series).
Low ambient temperature causing increased PV module Voc.
Inaccurate string voltage sensor within the inverter.
DC surge protection device (SPD) failure causing voltage clamping issues.
Ground fault condition elevating string voltage.

Pro Tip:

To quickly identify a potentially faulty optimizer, use the SolarEdge monitoring portal to compare the power output of each module within a string. A module with significantly lower power output than its neighbors may have a malfunctioning optimizer.

Technical Overview:

SolarEdge inverters utilize string inverters with DC optimizers. Each PV module connects to a DC optimizer, which then connects in series to form a string. The string voltage is the sum of the individual optimizer output voltages. Cold temperatures increase the open-circuit voltage (Voc) of PV modules. The inverter monitors string voltage to prevent exceeding its maximum input voltage, which could damage internal components like DC capacitors and semiconductors. The MPPT algorithm constantly adjusts to maximize power extraction while staying within voltage limits. AC coupling is relevant if batteries are installed, and the inverter needs to maintain the AC frequency in isolation.

Important Warnings:

High DC voltage is present in PV systems, even when the inverter is shut down. Always disconnect the DC disconnect switch and follow proper lockout/tagout procedures before working on any PV system components. Arc flash hazards are present when disconnecting live DC circuits. A qualified electrician is required for all electrical work.

Solution:

1

*Safety First**: Disconnect the AC power to the inverter and engage the DC disconnect switch per NEC 690 guidelines. Verify rapid shutdown functionality if applicable.
2

*Voltage Measurement**: Using a calibrated multimeter, measure the open-circuit voltage (Voc) of each PV module string at the inverter DC input terminals. Record the temperature of the modules.
3

*Optimizer Testing**: If a string has a significantly higher voltage, disconnect the string and individually measure the voltage at each optimizer output. Use an IR thermometer to check for overheating components. Replace any defective optimizers.
4

*String Configuration Verification**: Confirm the number of PV modules in series within each string matches the inverter's specifications and the SolarEdge design tool. Ensure the Voc at the lowest expected temperature will not exceed the inverter's maximum input voltage.
5

*Inverter Sensor Calibration**: Check the inverter's service menu for voltage sensor calibration options. Consult the SolarEdge system manual for the correct procedure. This usually requires specialized software and inverter admin credentials.
6

*SPD inspection**: Inspect the DC surge protection device (SPD) for damage or degradation. Use a multimeter to test the SPD's clamping voltage. Replace if necessary.
7

*Ground Fault Isolation**: Use a Megger or insulation resistance tester to check for ground faults on the DC side of the system. Follow manufacturer's safety guidelines.

Symptoms:

The SolarEdge inverter displays a "String Voltage Too High" error, typically occurring during cold winter mornings. This may result in the inverter shutting down or limiting power production to prevent exceeding its maximum input voltage rating.

Maintenance Tips:

Regularly inspect PV module wiring and optimizer connections for corrosion or damage.
Perform annual string voltage measurements during cold weather to identify potential issues early.
Update the inverter firmware to the latest version to benefit from improved voltage monitoring and control algorithms.
Implement a thermal monitoring program using IR cameras to detect hotspots in PV modules and optimizers.
Utilize SolarEdge's monitoring platform to track string voltage trends and identify anomalies.