Why does the gateway report an illegal data address error?

The Wattsonic Modbus TCP interface requires register addresses to be offset by +1 relative to the values published in some documentation tables. If you are polling address 11000 directly via Modbus TCP and receive exception code 2, verify the template addresses match exactly as shipped: the template already accounts for this offset.

The gateway connects but all power values read zero or time out. What now?

Check that the LAN dongle on the inverter shows an active link and that no firewall rule blocks port 502. The Wattsonic TCP server can time out after inactivity. Power-cycling the inverter or re-initiating the TCP connection from the ModbusCloud Gateway usually restores communication within seconds.

Phase current registers return values that seem ten times too large. Is this correct?

Yes, this is expected. Registers currents_a, currents_b, and currents_c are raw uint16 values that must be divided by 10 to obtain amperes. The ModbusCloud template applies a scale factor of 0.1 automatically. If you are building a custom poll alongside this template, remember to apply the same scaling.

The unit ID 255 causes errors in my network. Can I use a different ID?

The Wattsonic LAN dongle responds on Modbus unit ID 255 by default and this is not user-configurable through the standard inverter menu. Ensure no other device on the same Modbus TCP connection is configured with unit ID 255, and direct all poll requests to the inverter IP on port 502 with ID 255 as set in the template.

Free Modbus template: A-Tronix wattsonic (grid)

The A-Tronix wattsonic is a Gen3 hybrid solar inverter distributed under multiple brand names and used in residential and small-commercial PV installations. This template covers the grid meter role of the wattsonic, reading Modbus TCP registers for total grid power, per-phase active power on phases A, B, and C, and per-phase AC grid currents. All registers are read-only. With these seven registers visible in your ModbusCloud portal you can track real-time import and export at both whole-site and per-phase resolution, enabling accurate energy balance reporting and early detection of phase imbalances.

Name	Address	Function	Type	Unit	Access
power Total active grid power, positive = import, negative = export.	11000	FC03	int32	W	R
currents_a AC grid current on phase A, scaled by 0.1 to amperes.	11010	FC03	uint16	A	R
currents_b AC grid current on phase B, scaled by 0.1 to amperes.	11012	FC03	uint16	A	R
currents_c AC grid current on phase C, scaled by 0.1 to amperes.	11014	FC03	uint16	A	R
powers_a Active grid power on phase A, signed watts.	10994	FC03	int32	W	R
powers_b Active grid power on phase B, signed watts.	10996	FC03	int32	W	R
powers_c Active grid power on phase C, signed watts.	10998	FC03	int32	W	R

A-Tronix wattsonic (grid)

Overview

Use cases

Installation

Things to watch for

Registers (7)

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