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SMA Inverter Grounding Fault Event 901

Diagnose and resolve SMA inverter Event 901 grounding faults in residential solar+storage systems. Ensure safety, NEC compliance, and optimal system performance.

Frequently Asked Questions

•What are the common causes of Event 901 on an SMA inverter?

Loose grounding connections, corroded wiring, undersized grounding conductors, or internal inverter faults are common causes of Event 901.

•How do I safely troubleshoot a grounding fault on my solar system?

Always de-energize the system using the DC and AC disconnects and verify zero voltage with a multimeter. Only qualified electricians should perform troubleshooting and repairs.

•What NEC requirements apply to grounding solar PV systems?

NEC Article 690 covers grounding requirements for solar PV systems, including conductor sizing, bonding, and grounding electrode system requirements. Refer to the latest NEC edition.

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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 SMA hybrid inverter relies on a solid grounding system for safety and proper operation. The Protective Earth (PE) connection provides a low-impedance path for fault currents, ensuring that overcurrent protection devices (circuit breakers or fuses) trip quickly in the event of a ground fault. This protects both the equipment and personnel from electrical shock. The inverter continuously monitors the grounding impedance to detect any issues with the grounding bonds.

Symptoms:

Inverter reports Event 901, indicating a potential issue with the US grounding bonds or a missing Protective Earth (PE) connection. This can manifest as intermittent system shutdowns, reduced power output, or complete system failure. The inverter monitoring app may display error messages related to grounding or grid connection.

Possible Causes:

Loose or corroded grounding connections at the inverter, the service panel, or the grounding electrode.
Damaged or undersized grounding conductors.
Open neutral condition in the AC distribution panel.
Incorrect wiring or grounding of the PV array.
Failure of the internal ground fault detection circuitry within the SMA inverter.
Galvanic corrosion between dissimilar metals in the grounding system.

Solution:

1

De-energize the PV system by engaging the DC disconnect switch and the AC disconnect breaker. Verify zero voltage using a calibrated multimeter.
2

Inspect all grounding connections at the inverter, service panel, grounding electrode, and PV array for looseness, corrosion, or damage. Tighten or replace connections as needed.
3

Verify the grounding conductor size is adequate per NEC Table 250.122 based on the size of the overcurrent protection device. Use a clamp meter to measure ground fault current during a test condition (performed by a qualified electrician).
4

Perform a ground impedance test using a ground resistance tester to ensure the grounding system meets NEC requirements (typically less than 25 ohms).
5

Check for an open neutral condition at the AC distribution panel using a multimeter. Correct any wiring errors.
6

If the grounding system appears sound, consult the SMA inverter system manual for troubleshooting steps related to Event 901. It may be necessary to contact SMA technical support for further assistance.
7

After making any repairs, re-energize the system and monitor the inverter for proper operation. Verify that Event 901 has cleared.

Safety Warning:

Working with electrical systems involves the risk of electric shock and arc flash. De-energize all circuits before performing any work. Wear appropriate personal protective equipment (PPE), including insulated gloves and safety glasses. Only qualified electricians should perform grounding system repairs. Refer to NEC Article 690 for solar PV system grounding requirements. NEC 2017/2020 rapid shutdown compliance is mandatory.

Prevention:

• Periodically inspect grounding connections for looseness or corrosion, especially in areas with high humidity or salt air.
• Ensure that all grounding conductors are properly sized and installed according to NEC requirements.
• Schedule regular maintenance inspections by a qualified electrician to identify and address potential grounding issues before they become critical.
• Perform thermal scans of grounding connections with an IR thermometer to identify hotspots indicating loose or corroded connections.

Expert Tip:

Many SMA inverters have a hidden service menu accessible via a specific key combination on the display. This menu may contain diagnostic information related to grounding system performance, such as ground impedance measurements or fault history. Consult the SMA system manual or contact SMA technical support for instructions on accessing the service menu and interpreting the data.