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Generac•SnapRS

Analysis by Marcus & Team

Generac SnapRS: Loud Mechanical Snap During Startup

Diagnosing a Generac SnapRS unit making a loud mechanical snap during startup. Potential causes, troubleshooting steps, and safety warnings.

Frequently Asked Questions

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

NEC Article 690 dictates rapid shutdown requirements, mandating voltage reduction to safe levels within a specified timeframe when initiated. Specific requirements vary depending on the NEC edition adopted by the local jurisdiction.

•How can I verify the proper operation of the rapid shutdown system?

Verify by initiating rapid shutdown (following manufacturer’s procedures) and measuring voltage levels at designated points (e.g., array boundary, service entrance). Voltage should drop below the specified threshold (e.g., 30V) within the required timeframe (e.g., 30 seconds).

•What are the potential hazards associated with working on a PV system?

Potential hazards include electrocution from high DC voltage, arc flash, and falls. Always de-energize the system, wear appropriate PPE, and follow safe work practices.

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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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Safety Warning:

High DC voltage is present in PV systems. Always de-energize the system before performing any inspection or maintenance. Wear appropriate personal protective equipment (PPE), including insulated gloves and safety glasses. Refer to NEC Article 690 for PV system safety requirements. A qualified electrician is required for all electrical work.

Solution:

1

*Safety First:** Ensure the PV system is fully de-energized by disconnecting the AC and DC disconnects. Verify zero voltage on the PV string using a calibrated multimeter.
2

*Visual inspection:** Carefully inspect the SnapRS unit for any signs of physical damage, such as cracks, burns, or corrosion. Check wiring connections for looseness or damage.
3

*Voltage Measurement:** After isolating the faulty SnapRS unit and using proper PPE, and with the system de-energized, measure the voltage at the input and output terminals using a multimeter. Note readings.
4

*Continuity Test:** With the system de-energized and isolated, use a multimeter to perform a continuity test across the SnapRS unit's terminals in both the open and closed states. Record readings and compare to the manufacturer's specifications.
5

*Resistance Measurement:** Measure the resistance of the internal switch using a low-resistance ohmmeter. A high or infinite resistance reading when the switch should be closed indicates a faulty relay. Record findings.
6

*Replacement:** If the SnapRS unit is found to be faulty, replace it with a new, compatible Generac SnapRS unit. Follow the manufacturer's instructions for system and wiring.
7

*Verification:** After replacement, re-energize the system and verify that the new SnapRS unit is functioning correctly and that the snapping sound is no longer present. Monitor system performance using the monitoring app, ensuring the system is operating within normal parameters.

Expert Tip:

Use Generac's service portal for detailed troubleshooting guides specific to the SnapRS model. Often the error logs within the Generac inverter will provide clues, specifically about communication errors with the RSD. Check event logs within the inverter's service menu.

Technical Overview:

Generac SnapRS units are module-level rapid shutdown devices (MLPE) designed to comply with NEC 2017/2020 requirements for rapid shutdown of PV systems. They are triggered by a control signal from the inverter or a separate initiation device. Upon activation, the SnapRS units disconnect the PV module from the string, reducing voltage to a safe level (typically <30V) within 30 seconds. The mechanical snap sound suggests a fault in the internal relay or switching mechanism.

Common Causes:

Failed or degraded internal relay within the SnapRS unit preventing proper switching.
Overvoltage or overcurrent condition causing the relay to arc and snap.
Mechanical failure of the switching mechanism due to wear and tear.
Loose wiring or connections leading to voltage spikes and relay malfunction.
Communication failure between the inverter and the SnapRS unit, resulting in erratic behavior.
Environmental factors (temperature extremes, moisture ingress) affecting the SnapRS unit's performance.

What to Look For:

The Generac SnapRS unit emits a loud, distinct mechanical snapping sound during system startup. This occurs after the PV system attempts to energize, indicating a potential issue within the RSD device's switching mechanism.

Prevention:

Implement a regular preventative maintenance schedule
This includes checking for loose wiring, inspecting for corrosion, and ensuring proper ventilation
Firmware updates, when available from the manufacturer, should be applied to ensure optimal performance and compatibility
Thermally scan the SnapRS units periodically to identify overheating, which could indicate a developing fault