Three-Phase Eastron Meter Wiring Guide for Sunsynk and Deye Inverters

Key Takeaways

• The Eastron SDM630MCT and SDM630MCT v2 are fully compatible with Sunsynk and Deye 8kW, 10kW, and 12kW low-voltage three-phase hybrid inverters.
• Terminal bridging is strictly required: link connection 5 (LA) to an active phase (connections 2, 3, or 4) and connection 6 (NA) to neutral (connection 1).
• All three current transformers must be installed with directional arrows pointing towards the electrical loads.
• RS485 data lines connect meter terminal 14 (TX+A) to inverter Pin 5 (485-A) and terminal 13 (TX-B) to Pin 4 (485-B).
• Always de-energize the distribution board, isolate reference voltage miniature circuit breakers, and follow national wiring safety isolation rules before wiring.

Eastron Meter Compatibility for Three-Phase Inverters

Three-phase Sunsynk and Deye hybrid systems depend on specialized external power meters designed to sample voltage, line current, active power, and reactive power across all three electrical phases simultaneously.

The primary supported meter for these platforms is the Eastron SDM630MCT, which utilizes external current transformers (typically with 1A or 5A secondary outputs) rather than direct-feed internal shunts. In addition to the original SDM630MCT, another compatible three-phase meter model is the SDM630MCT v2. While the physical terminal layout, terminal numbering, and serial wiring interface remain consistent between these hardware revisions, the internal software menu structure for configuring current transformer ratios differs significantly between the original and second-generation models.

Installing an external meter becomes necessary whenever the physical distance between the incoming utility supply point on the main distribution board and the hybrid inverter exceeds the practical limits of standard analogue CT extension leads. High-frequency electrical noise across extended analogue leads distorts current wave shapes, leading to inaccurate power readings and erratic inverter behavior. Digital Modbus serial communication over shielded twisted-pair cabling resolves this issue by transmitting packetized digital telemetry over substantial installation runs.

Step-by-Step Auxiliary Power Supply Bridging

Unlike self-powered residential single-phase meters, the Eastron SDM630MCT requires independent auxiliary AC power to energize its internal measurement microprocessors and digital display circuitry. Installers frequently overlook this operational requirement, leaving terminals 5 and 6 unpowered and assuming the meter draws operating power purely from the monitored voltage phases.

To power the internal meter electronics correctly, physical bridging wires must be installed across the lower terminal block:

1. Phase Bridge Connection: Fabricate a short jumper wire from insulated panel wire and create a bridge from connection 5 labelled LA to one of the phases (connection 2, 3, or 4). This supplies active phase voltage to the internal power supply module.
2. Neutral Bridge Connection: Fabricate a matching neutral jumper wire and create a bridge from connection 6 labelled NA to the neutral (connection 1). This completes the return path to the main neutral busbar.
3. Reference Phase Connections: Connect incoming utility reference voltages directly to terminal 1 (Neutral), terminal 2 (Phase 1 / L1), terminal 3 (Phase 2 / L2), and terminal 4 (Phase 3 / L3) through dedicated, appropriately rated miniature circuit breakers (MCBs) installed on the distribution board.

```
EASTRON SDM630MCT TERMINAL BLOCK (AUXILIARY BRIDGES)
+---------------------------------------------------+
| [1] [2] [3] [4] [5] [6] |
| Neutral L1 L2 L3 LA NA |
+---|------|-----|-----|---------|----------|-------+
| | | | | |
| +-----+-----+---------+ |
| Phase Jumper Bridge |
+---------------------------------------+
Neutral Jumper Bridge
```

All terminal connections must be torqued securely according to manufacturer specifications to eliminate high-resistance thermal joints. In South African electrical installations governed by national wiring standards, reference voltage sensing lines must be protected by local overcurrent protection devices to permit safe isolation during maintenance procedures.

Three-Phase Current Transformer Orientation and Phasing

Accurate energy metering requires strict alignment between reference voltage inputs and current transformer sampling channels. If a current transformer installed on Phase 1 is inadvertently terminated into the Phase 2 inputs on the meter, or if a clamp is installed in reverse orientation, the calculated power factor becomes negative, and active power calculations fail.

CT Installation Polarity Rules

Each current transformer features a directional marking molded onto its casing:

• The CT clamp has an arrow that must point towards the loads (consumer unit, what South African electricians call the main distribution board) and away from the incoming utility service head.
• Installing the CT clamp with the arrow facing backwards towards the grid causes the inverter to interpret imported power as solar export, leading to rapid system shutoff or tripping prepaid utility meters.

Terminal Wiring Array

The secondary wiring leads from each split-core or solid-core CT must be connected to the corresponding terminal blocks located on the meter:

• From left to right in the image above you have L1, L2, then L3 current measurement pairs.
• For each phase, connect the white secondary conductor (S1) to the positive terminal and the black return conductor (S2) to the negative terminal.
• Ensure that the phase conductor passing through the L1 CT corresponds strictly to the voltage conductor supplying terminal 2. Any phase mismatch between voltage sensing and current sensing causes severe active power calculation errors.

RS485 Modbus Cable Preparation and Pinouts

The Eastron SDM630 communicates with the hybrid inverter via a half-duplex RS485 serial communication bus operating over Modbus RTU protocol. Standard Cat5e or Cat6 shielded twisted-pair (STP) cabling must be used to guarantee signal integrity across commercial plant rooms.

On the Eastron meter casing:

• Connection 14 is designated as TX+A (RS485 positive data differential).
• Connection 13 is designated as TX-B (RS485 negative data differential).

Termination Procedure

1. Strip the outer PVC sheath of the Cat5e or Cat6 communication cable carefully, ensuring the internal foil shield and bare drain wire are preserved.
2. Choose which solid coloured cable (eg Brown) to connect into TX+A (connection 14) and choose its opposite Colour / White cable (eg Brown/White) and connect to TX-B (connection 13).
3. On the inverter side of the cable run, terminate the twisted pair into a standard male RJ45 modular plug using a precision ratcheting crimping tool.
4. The communication pin allocation on the inverter chassis requires that Pin 4 = 485-B and Pin 5 = 485-A and plug RJ45 into Meter/RS485 Port.
5. This pin out applies to the 8/10/12kW Three-Phase Low-Voltage inverter units.

```
+---------------------+-------------------+---------------------+

+---------------------+-------------------+---------------------+

+---------------------+-------------------+---------------------+
```

The overall cable drain wire must be bonded to electrical earth at a single point (typically at the main distribution board chassis) to prevent ground loops. Never connect the shield drain wire to electrical earth at both ends of the cable run.

Programming the Eastron SDM630 Meter Parameters

Once physical wiring and communication lines are verified, the Eastron meter must be programmed via its front panel navigation buttons to establish operational communication parameters.

```
+---------------------------------------------------+
| EASTRON SDM630MCT |
| +---------------------------------------------+ |
| | SET P 1000 | |
| +---------------------------------------------+ |
| |
| [ E ] [ P ] [ V/I ] |
| Scroll/Up Scroll/Down Enter/Hold |
+---------------------------------------------------+
```

Entering Setup Mode

1. Ensure the meter is energized via the auxiliary voltage bridge terminals 5 and 6.
2. Press and hold the navigation button for 3 seconds until the password screen appears.
3. The password is 1000. Each digit flashes sequentially from left to right; use the scroll buttons to set the correct value and confirm each number.
4. After confirming the final digit, press the confirmation key to exit the number setting routine. The SET indicator on the LCD panel will update to reflect active programming status.

Serial Protocol and CT Configuration

Navigate through the setup sub-menus to confirm the following settings:

• Modbus Slave Address: Set the meter ID address to 1 (default for primary grid metering).
• Baud Rate: Confirm the communication speed is configured to 9600 bps, matching the default firmware polling rate of the hybrid inverter.
• Parity / Stop Bits: Set to None parity with 1 stop bit (n.1).
• Current Transformer Ratios: Enter the CT primary rating (CT1) and secondary rating (CT2) matching the physical coils installed on the main phase conductors.
• Lockout Notice: CT ratio settings can only be set once during initial commissioning. If incorrect values are confirmed, the parameter table locks permanently, requiring an override password from Eastron technical support to modify.

Inverter Firmware Configuration and Ex_Meter Activation

After configuring the physical meter, the hybrid inverter firmware must be updated via its digital touchscreen interface to stop listening to internal CT ports and begin polling the RS485 serial bus.

1. Unlock the inverter touchscreen display by tapping the screen and entering the technician access credentials.
2. Go into the Settings page and select Advanced Settings and select the ‘Others’ tab.
3. Locate the current transformer selection toggle and select Ex_Meter for CT.
4. In the adjacent drop-down menu, choose Eastron from the listed options to initialize the Modbus communications driver.
5. Save the configuration and allow the inverter processor to reinitialize its serial communications interface.

Live Telemetry Verification and Troubleshooting

Proper commissioning ends with end-to-end telemetry verification between the meter and the inverter control board.

Normal Communication State

• If communication is successful, you will now see an AC Load on the inverter home screen.
• The power readings displayed on the inverter screen should dynamically match the active power readings recorded on the Eastron LCD panel.
• Switching on high-current loads (such as electric water heaters or borehole pumps) should cause immediate, proportional increases in both meter readings and inverter load telemetry.

Alarm Conditions and Fault Rectification

• If the connection fails, you will receive a warning ‘W04_Meter_Comm_Fail’ on the inverter alarm log.
• Reversed Data Conductors: A common root cause of W04 is swapping differential lines A and B. Ensure terminal 14 on the meter connects cleanly to Pin 5 on the RJ45 jack, and terminal 13 connects to Pin 4.
• Incompatible Baud Rate: Verify that the meter baud rate has not been altered from 9600 bps.
• Cable Length Constraints: For extended RS485 runs exceeding practical limits, ensure termination resistors (120-ohm metal film resistors across lines A and B) are fitted at the ends of the bus to dampen signal reflections.

Following this structured procedure guarantees reliable communication, protects sensitive prepaid municipal meters against accidental reverse power tripping, and ensures South African three-phase solar microgrids operate safely and efficiently.