Wattsonic Wattsonic GEN3 (pv)

Installation

1. 1Ensure the Wattsonic GEN3 LAN dongle is installed and connected to your site network; Modbus TCP is available natively on port 502 with unit ID 255 and requires no separate RS485 adapter.
2. 2Connect the ModbusCloud Gateway to the same LAN segment as the inverter, confirming the Gateway can reach the inverter's IP address on port 502.
3. 3In the ModbusCloud portal, add a new device, import the Wattsonic GEN3 (pv) template, and set the unit ID to 255 with the inverter's local IP address and port 502.
4. 4Spot-check the power register in the portal's live data view during daylight hours to confirm a positive non-zero watt reading appears, indicating a successful connection.

Things to watch for

01

The gateway connects but the power register always reads zero.

Confirm the inverter is actively generating: the register returns zero at night or when the inverter is in standby. During daylight, check that the LAN dongle's status LED is active and that no firewall rule is blocking port 502 between the ModbusCloud Gateway and the inverter's IP address.

02

I get an 'illegal data address' error on function code 3.

Some Wattsonic GEN3 firmware versions offset register addresses by one. If address 11028 returns exception code 2, try address 11029. Confirm the unit ID is set to 255, as the inverter's LAN dongle requires this specific value and will reject requests sent to other unit IDs.

03

The power value is negative or unexpectedly large. Is the scaling wrong?

The register is a signed int32 and returns watts directly with no scaling factor. Negative values can appear briefly during startup or fault states. If values are implausibly large, verify the decode type is int32 and not uint16 or uint32, as an incorrect decode type will misinterpret the two-register word order.

04

Communication drops out intermittently after a few minutes.

The Wattsonic GEN3 LAN dongle has a known sensitivity to concurrent TCP connections. Ensure only one Modbus TCP client is polling the inverter at a time. If another system such as a home automation controller is also polling the same IP and port, the connections will collide and cause timeouts. Use a single polling source or increase the poll interval.

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