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Unspecified•Microinverter

Analysis by Marcus & Team

Unspecified Microinverter Leakage Current Causes

Leakage current in microinverters: Causes, solutions, and prevention. Understand the risks and safety procedures for residential PV systems.

Frequently Asked Questions

•What is the NEC code requirement for grounding PV microinverters?

NEC 690.41 through 690.47 covers grounding requirements for PV systems, including microinverters. Proper grounding ensures safety and minimizes the risk of electrical shock.

•How can I test the GFCI breaker protecting my microinverter circuit?

Most GFCI breakers have a test button. Pressing this button should trip the breaker. If it does not trip, the breaker may be faulty and should be replaced by a qualified electrician.

•What are the signs of a failing Y-capacitor in a microinverter?

Failing Y-capacitors can cause increased leakage current, audible noise from the microinverter, or erratic operation. Replacement should be performed by a qualified technician.

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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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Important Warnings:

Working with PV systems involves exposure to high DC voltages. Always disconnect the DC and AC power sources before performing any maintenance or troubleshooting. Adhere to all applicable NEC guidelines and wear appropriate personal protective equipment (PPE), including insulated gloves and safety glasses. Only qualified electricians should perform invasive measurements.

Recommended Action:

1

De-energize the PV system by following NEC 690.15 guidelines for disconnecting the DC and AC sides. Verify absence of voltage using a calibrated multimeter.
2

Visually inspect the microinverter housing for any signs of physical damage, corrosion, or moisture ingress.
3

Use a multimeter to measure the resistance between the microinverter housing and the grounding conductor. A low resistance indicates a direct short.
4

Employ a clamp meter to measure the AC leakage current flowing from the microinverter housing to ground. Compare the reading to the manufacturer's specifications.
5

If possible according to manufacturer instructions, perform an insulation resistance (IR) test on the microinverter's internal circuits to identify insulation breakdown. Qualified personnel only.
6

Replace the microinverter if leakage current exceeds acceptable limits or if internal damage is evident. Ensure proper grounding of the replacement unit per NEC 250.
7

Verify proper operation of the GFCI circuit breaker protecting the AC circuit connected to the microinverter.

Technical Recommendation:

Some microinverters have built-in diagnostics that can be accessed through a monitoring app or service portal. These diagnostics may provide information about insulation resistance or leakage current levels. Consult the manufacturer's documentation for specific instructions.

Possible Causes:

Deteriorated or damaged insulation within the microinverter, leading to capacitive coupling between the internal components and the housing.
Moisture ingress compromising the dielectric strength of insulating materials.
Failure of Y-capacitors (safety capacitors connected between line and ground) inside the microinverter.
Breakdown of the isolation transformer (if present) within the microinverter.
Physical damage to the housing, creating a direct conductive path to internal components.
Improper grounding of the microinverter or the solar panel racking system.

How It Works:

Microinverters convert DC power from solar panels to AC power for grid injection. This involves high-frequency switching and galvanic isolation between the DC and AC sides. Leakage current occurs when unintentional conductive paths exist between the internal circuitry and the grounded aluminum housing. This is most critical in AC coupled residential systems.

What to Look For:

Presence of AC leakage current from the microinverter housing to ground, detectable by a ground fault circuit interrupter (GFCI) tripping or a multimeter measuring AC current between the housing and ground. May also manifest as elevated touch voltage on the aluminum housing.

Preventative Care:

Regularly inspect the microinverters for any signs of damage or corrosion.
Ensure proper ventilation around the microinverters to prevent overheating and moisture buildup.
Follow manufacturer's recommendations for cleaning and maintenance.
Periodically check the grounding connections to ensure they are secure and free of corrosion.
Conduct routine insulation resistance tests as part of a comprehensive maintenance program (qualified personnel only).