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Analysis by Marcus & Team

SolarEdge PV String Voltage Drop Troubleshooting

Troubleshooting sudden voltage drops in SolarEdge PV strings. Diagnosis of possible causes and solutions for residential SolarEdge hybrid inverter systems.

Frequently Asked Questions

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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Technical Background:

SolarEdge hybrid inverters use DC optimizers connected to each PV module. These optimizers perform Maximum Power Point Tracking (MPPT) individually for each module and then boost the voltage to a common DC bus voltage. The inverter then converts this DC voltage to AC voltage for grid export or household use. A sudden voltage drop indicates a problem affecting the entire string's voltage output *before* the DC/AC conversion stage. The optimizers rely on communication with the inverter. NEC 2017/2020 mandates rapid shutdown (RSD) which this system implements. This system's architecture includes PV modules, DC optimizers, string wiring, string fuses, DC disconnect, the inverter itself, and grid interconnection.

Symptoms:

The entire SolarEdge PV string voltage drops significantly or to zero, observed either on the inverter display, monitoring app, or through direct voltage measurement at the string's DC disconnect. This voltage drop may occur suddenly and can be intermittent or persistent. Power output from the affected string is also reduced or absent.

Possible Causes:

A faulty or tripped string fuse within the combiner box or at the inverter DC input.
A loose or corroded wiring connection within the string, particularly at combiner boxes, disconnects, or module connectors (MC4).
Failure of the SolarEdge inverter's MPPT or DC boost circuitry for that specific string input.
A communication issue between the SolarEdge inverter and the optimizers within the affected string, preventing proper MPPT operation.
Activation of the rapid shutdown (RSD) system due to a fault condition or manual initiation.
Ground fault within the string wiring or PV modules.

Solution:

1

*Safety First**: Engage the AC and DC disconnects for the SolarEdge system. Verify zero voltage using a calibrated multimeter before proceeding.
2

*Visual inspection**: Check all wiring connections, fuses, and disconnects within the affected string for signs of damage, corrosion, or loose connections. Use an IR thermometer to scan for hot spots which indicate faulty connections.
3

*Fuse Testing**: Use a multimeter to verify the continuity of each string fuse. Replace any blown fuses with appropriately rated replacements. Ensure fuse ratings comply with NEC 2017/2020 requirements and local codes.
4

*Voltage Measurement (Open Circuit)**: With the system disconnected, measure the open-circuit voltage (Voc) of each PV module and the entire string using a calibrated multimeter. Compare readings to manufacturer specifications and neighboring strings. Significant deviations indicate a problem with individual modules or string wiring. Ensure the meter is CAT III rated for high voltage DC.
5

*Isolate the Problem**: If the Voc is normal, reconnect the string and use a clamp meter to measure the current in each section of the string. Compare current readings to the inverter display or monitoring app. A sudden drop in current indicates a problem between those two points.
6

*Optimizer Communication Check**: Access the SolarEdge monitoring portal (installer level) or contact SolarEdge support to check the communication status of each optimizer within the string. Replace any non-communicating optimizers.
7

*Inverter Diagnostics**: Consult the SolarEdge inverter's manual for troubleshooting procedures related to string voltage and current faults. If necessary, contact SolarEdge technical support for assistance.

Safety Warning:

Solar PV systems operate at high DC voltages, posing a significant electrical shock and arc flash hazard. Never attempt to work on a live solar PV system. Always engage both AC and DC disconnects and verify zero voltage with a calibrated multimeter before touching any components. Work should only be performed by a qualified electrician familiar with NEC 2017/2020 Article 690 requirements for solar PV systems and SolarEdge-specific safety procedures.

Prevention:

• Conduct annual visual inspections of all wiring connections, fuses, and disconnects.
• Monitor string voltage and current readings regularly through the SolarEdge monitoring app.
• Perform routine cleaning of PV modules to maintain optimal performance.
• Ensure the inverter firmware is updated to the latest version. Schedule preventative maintenance with a qualified electrician every 3-5 years.

Expert Tip:

In the SolarEdge monitoring portal, check the "Events" log for the affected inverter. Look for recurring or recent events related to DC voltage, current, or communication faults. These events can provide valuable clues to the cause of the voltage drop. Also, use the SolarEdge SetApp to perform on-site diagnostics and firmware updates.