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SolarEdge•18KPV

Analysis by Marcus & Team

SolarEdge 18KPV: Fault Code F71 Ground Bonding Error

Troubleshoot SolarEdge 18KPV F71 ground bonding error. Diagnose ground faults, check wiring, ensure NEC compliance. Safety first: qualified electrician required.

Frequently Asked Questions

•What tools are needed to diagnose a ground fault in a solar PV system?

A multimeter, clamp meter, low-resistance ohmmeter (DLRO), insulation resistance tester (megohmmeter), torque wrench, and appropriate hand tools are essential for diagnosing ground faults.

•What are the common causes of ground faults in residential PV systems?

Common causes include damaged module insulation, loose or corroded grounding connections, undersized grounding conductors, and improper bonding of metallic enclosures.

•How does NEC 690 address grounding requirements for solar PV systems?

NEC 690 provides detailed requirements for grounding and bonding of PV systems, including conductor sizing, equipment grounding, and ground fault protection. Compliance with NEC 690 is crucial for safety and code compliance.

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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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Technical Background:

The SolarEdge 18KPV hybrid inverter is a grid-tied inverter with battery backup capabilities. Grounding is critical for safety and proper operation. The grounding system provides a low-impedance path for fault currents, allowing overcurrent protection devices (circuit breakers or fuses) to quickly clear faults. The F71 error typically arises from a high resistance or open circuit in the grounding path, preventing proper fault current flow and creating a shock hazard. The inverter continuously monitors the ground impedance and triggers the F71 error when it exceeds a predetermined threshold. This error is a critical safety mechanism to prevent electrical shock and equipment damage.

Critical Safety Precautions:

High DC voltages (up to 600V or higher) are present in PV systems. Only qualified electricians with experience in PV system system and maintenance should perform troubleshooting and repairs. Always follow proper lockout/tagout procedures and wear appropriate personal protective equipment (PPE), including insulated gloves, safety glasses, and arc-rated clothing. Be aware of potential arc flash hazards. Never work on live circuits. NEC 690 provides specific requirements for PV system safety.

Recommended Action:

1

*Safety First**: De-energize the PV system by disconnecting the DC disconnect switch and the AC breaker feeding the inverter. Verify zero voltage with a calibrated multimeter at both the AC and DC terminals of the inverter.
2

*Visual inspection**: Carefully inspect all grounding conductors and connections from the PV array, through the inverter, to the main service panel. Look for loose connections, corrosion, or physical damage. Document findings with photographs.
3

*Grounding Resistance Measurement**: Use a low-resistance ohmmeter (DLRO) to measure the resistance between the inverter grounding terminal and the main service panel ground bus. The resistance should be very low (typically less than 0.1 ohm). Record the measurement.
4

*PV Array Ground Fault Isolation**: If the grounding resistance is high, isolate the PV array by disconnecting the PV strings at the inverter DC input. Measure the resistance between each PV string conductor (positive and negative) and ground. High resistance (megohms) indicates good insulation. Low resistance indicates a ground fault within the PV array. Use an insulation resistance tester (megohmmeter) to further evaluate insulation integrity.
5

*Grounding Conductor Sizing**: Verify that the grounding conductor is properly sized according to NEC 250.166 based on the size of the ungrounded conductors. Replace undersized conductors with appropriately sized ones.
6

*Tighten and Clean Connections**: Clean and tighten all grounding connections using appropriate tools. Apply an anti-corrosion compound to prevent future corrosion. Ensure torque specifications are met.
7

*Re-test and Monitor**: After making corrections, re-energize the system and monitor the inverter for the F71 error. Use the SolarEdge monitoring portal to observe system performance and identify any further issues. Document all steps taken and measurements recorded.

Common Causes:

Loose or corroded grounding connections at the inverter, PV array, or electrical service panel.
Damaged or undersized grounding conductor.
Improper bonding of metallic enclosures (e.g., junction boxes, conduit).
Ground fault within the PV array (e.g., damaged module insulation).
Neutral-ground bond issue at the service panel (especially in older systems).
Failure within the inverter's internal ground fault detection circuitry.

What to Look For:

The SolarEdge 18KPV hybrid inverter displays an 'F71 Ground Bonding Error'. This error indicates a potential issue with the grounding connection between the inverter, the PV array, and the electrical service panel. The system may shut down or derate its power output.

Prevention:

Perform annual visual inspections of all grounding connections for corrosion or looseness.
Re-torque grounding connections every 3-5 years as part of routine maintenance.
Regularly inspect PV modules for signs of damage or degradation, which could lead to ground faults.
Ensure proper system and maintenance of surge protection devices (SPDs) to protect against voltage surges that can stress grounding systems.
Keep detailed records of all maintenance activities and repairs.