Growatt Smart Meter Wiring and Zero Export Guide

This guide details the definitive wiring and configuration procedures for Growatt inverters when paired with Eastron smart meters (SPM-E and SDM630-Modbus) to achieve zero export. We will cover RS485 communication terminal wiring, correct CT clamp orientation, troubleshooting for reverse CT readings, and programming the Export Limit via ShinePhone.

Understanding Growatt Zero Export

Growatt inverters, manufactured by Growatt New Energy, can be configured to prevent excess solar power from being exported to the grid. This "zero export" functionality relies on a smart meter to accurately measure grid power flow. The smart meter communicates with the inverter, allowing it to dynamically adjust its output to match household consumption. This setup is compatible with residential single-phase and commercial three-phase energy storage installations globally.

Required Smart Meters

Growatt inverters utilize specific Eastron smart meters for this functionality:

• Eastron SPM-E: For single-phase installations.
• Eastron SDM630-Modbus: For three-phase installations.

These smart meters communicate with Growatt hybrid and string inverters via dedicated RS485 terminal connections.

Safety First: Before You Begin Any Wiring

Working with electrical systems carries inherent risks. Always prioritize safety to prevent injury or damage to equipment.

Isolate Power: Before performing any wiring, it is critical to de-energize the main distribution board and isolate all circuit breakers. This includes both AC and DC isolators.

Capacitor Discharge: After switching off all AC and DC isolators, wait at least 5 minutes before opening inverter wiring compartments. This allows internal capacitors to safely discharge.

Wiring the Smart Meter

Correct installation and wiring of the smart meter are crucial for accurate power measurement and effective zero export control.

1. Smart Meter Physical Placement

The smart meter must be installed at the main grid connection point before any distribution sub-circuits. This ensures it measures the total power flowing to and from the grid for the entire premises.

2. RS485 Communication Wiring

The smart meter communicates with the Growatt inverter via an RS485 connection.

Procedure:

1. Ensure all power is isolated as per the safety instructions above.
2. Connect a communication cable to the RS485-A and RS485-B terminals on the smart energy meter.
3. Use a shielded twisted pair cable for this connection to minimize interference.
4. Connect the other end of this cable to the corresponding RS485-A and RS485-B terminals on your Growatt inverter. Refer to your specific inverter's manual for exact terminal locations.

3. CT Clamp Installation and Orientation

Current Transformers (CT clamps) measure the current flowing through the grid lines. Their orientation is critical.

Procedure:

1. Ensure all power is isolated.
2. Position the external current transformers on the incoming grid phases.
3. Crucially, ensure the arrows on the CT clamps are pointing towards the household loads. This indicates the direction of current flow from the grid into your property.
4. In three-phase installations, verify that voltage phases (L1, L2, L3) correspond strictly to the respective CT clamp phases.

Configuring Zero Export in ShinePhone/Inverter

Once the smart meter is correctly wired, you need to configure the inverter for zero export.

Procedure:

1. Access the inverter settings via the ShinePhone app or the inverter's OLED menu.
2. Navigate to the "Export Limit" setting.
3. Enable "Export Limit".
4. Set the export power limit to 0 Watts.

This configuration instructs the inverter to limit its output so that no power is sent back to the grid.

Troubleshooting Common Issues

Reverse CT Clamp Reading

A common issue during smart meter installation is incorrect CT clamp orientation.

Diagnostic Indicator: If the smart meter power reading shows negative during grid import, this indicates that the CT clamp is installed in reverse. Grid import should always show as a positive power flow from the grid.

Solution: To correct this, reverse the CT clamp orientation on the main line. Ensure the arrow on the CT clamp points towards the household loads.

Verifying Operation

After installation and configuration, you can verify the system's operation. Accurate meter connection enables ShineServer to display real-time household consumption and solar self-consumption, confirming that your zero export system is functioning as intended.