Single-Phase Eastron Meter Wiring Guide for Sunsynk and Deye

Key Takeaways

• Single-phase Eastron meters (SDM120CT and SDM230) are strictly incompatible with three-phase inverters; three-phase systems require dedicated three-phase Eastron meters.
• On the SDM120CT, terminate AC mains power into port 4 (Live) and port 3 (Neutral), and external CT coil leads into port 2 (Black) and port 1 (White).
• For standard single-phase inverters, connect RS485 into RJ45 pin 4 (solid blue) and pin 5 (blue/white); high-capacity 10kW, 12kW, and 16kW models use pins 1 and 2.
• The SDM230 utilizes an internal inline current passthrough rather than an external CT clamp, requiring full line current to route through the meter base.
• In the inverter Advanced Settings menu, enable External Meter for CT and select Eastron-1P to establish telemetry; communication failure triggers warning W04_Meter_Comm_Fail.

Compatibility Warning: Single-Phase Only

Digital energy meters provide high-precision revenue-grade metering over RS485 serial communication, eliminating the electrical noise and distance limitations of analogue CT clamp cables. In South African installations where the main distribution board is situated far from the inverter, Eastron single-phase meters are the preferred metering standard.

Hard Incompatibility Rule

Three-Phase Prohibition: Please note that this Eastron meter is not compatible with a three-phase inverter. Attempting to connect an SDM120CT or SDM230 to a three-phase Sunsynk or Deye unit prevents phase vector balance and triggers communication alarms. Three-phase systems must use a three-phase meter such as the three-phase Eastron meter.

Architecture: SDM120CT vs SDM230

Installers encounter two common single-phase Eastron meter variants:

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1. Eastron SDM120CT: Utilises an external current transformer coil. The meter requires separate AC voltage reference connections and dedicated CT sensor inputs.
2. Eastron SDM230: As this meter measures power using the meter passthrough as opposed to a CT measurement, line current routes directly into and out of the meter enclosure.

SDM120CT Wiring: AC Voltage, CT Coil & RS485

Wiring the SDM120CT involves three distinct wiring interfaces: AC supply, CT sensor, and RS485 serial communications.

Electrical Shock Hazard

Mains Voltage Isolation: Before landing conductors on DIN-rail meter terminals, disconnect the incoming municipal utility supply at the main circuit breaker. Verify the absence of AC potential using a verified voltage tester.

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Step 1: AC Voltage Reference

• Connect the incoming Live mains conductor into port 4.
• Connect the system Neutral conductor into port 3.
  These connections provide operational power to the internal microprocessor and supply the reference voltage waveform for real-time active power calculations.

Step 2: External CT Coil Connection

• Connect the external CT coil black lead into port 2.
• Connect the external CT coil white lead into port 1.
  Position the external CT clamp on the main incoming live feed ahead of all distribution breakers, ensuring the molded arrow points away from the grid towards the consumer loads.

Step 3: RS485 Serial Communication

Using twisted-pair cable such as CAT-5 or CAT-6:

• Select the blue pair: use solid blue and blue/white, and move the unused cores away.
• Connect the solid blue core to RS485-B (port 9).
• Connect the blue/white core to RS485-A (port 10).

Inverter RJ45 Pinouts: Standard vs High-Capacity Models

At the opposite end of the communication cable, terminate the twisted pair into a standard 8P8C (RJ45) modular plug. The physical pinout differs depending on the inverter power rating:

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1. Standard Inverter Pinout: On standard single-phase residential units, crimp the solid blue core into pin 4 and the blue/white core into pin 5.
2. High-Capacity Pinout Exception: Note that if using the 10kW, 12kW, or 16kW single-phase inverters, communication routes through pins 1 and 2 in the RJ45 plug.
3. Port Insertion: Insert the finished RJ45 connector firmly into the dedicated METER port on the underside of the inverter. If your specific hardware revision does not feature a separate METER jack, insert the plug into the general RS485 port.

SDM230 Passthrough Meter Wiring

When deploying the direct-connect SDM230 meter:

1. Passthrough Power Wiring: Route the incoming live feed directly through the meter power terminals as indicated on the side-mounted connection label.
2. RS485 Serial Terminals:

• Connect solid blue (RS485-B) into port 6.
• Connect blue/white (RS485-A) into port 5.

3. RJ45 Termination: On the inverter side, use an RJ45 connector and terminate solid blue into pin 4 and blue/white into pin 5 for standard single-phase inverters (or pins 1 and 2 for 10kW, 12kW, and 16kW units).

Modbus Register Configuration & Setup Password

For the inverter to communicate successfully with the Eastron meter, serial transmission parameters on the meter must match the inverter polling settings:

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Accessing Meter Programming

1. Press and hold the navigation button on the Eastron meter front panel until the configuration screen appears.
2. If prompted for a security code to modify parameters, enter the default setup code.
3. Verify and adjust the following communication settings:

• Set Address: 001
• Set Baude Rate: 9.6k
• Set Parity: None

4. If communication issues persist, verify that the physical wiring is not swapped between A and B, and re-check that the meter serial parameters match these values.

Inverter Touchscreen Software Setup & Alarms

Once physical wiring and meter Modbus registers are verified, configure the inverter control software:

1. Wake the inverter display and tap the Gear / Settings icon.
2. Navigate to Advanced Settings.
3. Locate the metering submenu and select the External Meter for CT checkbox.
4. On the Meter Select dropdown field, tap and select Eastron-1P.
5. Tap OK to commit the settings into non-volatile memory.

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Telemetry Verification & W04 Troubleshooting

• Successful Link: Return to the inverter home screen. The power flow diagram will immediately populate with real-time AC Load data reflecting domestic grid import and export.
• Communication Failure: If the serial handshake fails, the inverter illuminates the warning indicator and logs the event: W04_Meter_Comm_Fail.
• If W04 occurs, immediately check whether RS485-A and RS485-B are reversed, confirm that RJ45 pinouts match the inverter capacity class (pins 4 & 5 vs pins 1 & 2 on 10kW, 12kW, or 16kW units), and verify that baud rate is locked to 9.6k.

Wiring Reference Summary Matrix

Following this precise terminal mapping ensures seamless Modbus RTU telemetry between single-phase Eastron meters and Sunsynk or Deye hybrid inverters, preventing W04 alarms and enabling reliable zero-export power control.