All registers return zero or an illegal-address error. Why?

The wattsonic firmware requires the polled address to be the documented address plus one when accessed over TCP. If you have manually configured register addresses, verify each address is offset by plus one from the value shown in third-party documentation. The addresses in this template already account for the correct offset as implemented by OpenEMS.

The gateway connects but no values appear after import. What now?

Confirm the LAN dongle is active and its LED shows a network link. Check that unit ID is set to 255 in the portal device settings. If the inverter is on a different VLAN or behind a firewall rule, port 502 TCP must be open. Try pinging the inverter IP from a device on the same segment to rule out routing issues.

Phase current values look ten times too large. What is the scaling?

Registers 11010, 11012, and 11014 return current as uint16 values in tenths of an ampere, so a raw value of 153 represents 15.3 A. Ensure your portal channel applies a scale factor of 0.1 to these three registers. The total power register at 11000 is in whole watts and requires no scaling.

Per-phase powers do not sum to the total power reading. Is this normal?

Minor discrepancies between the sum of per-phase powers at 10994 to 10998 and the total at 11000 can occur because both sets are read in separate Modbus transactions. Short-lived load transients between polls cause the mismatch. If the gap is consistently large, check for firmware updates on the wattsonic inverter through the Wattsonic app.

Free Modbus template: Sunway wattsonic (grid)

The Sunway wattsonic is a three-phase hybrid solar inverter sold under the Sunway brand, deployed in residential and light-commercial PV-plus-storage installations. This template reads the inverter's built-in grid meter over Modbus TCP, capturing total grid power at address 11000 and per-phase active power across phases A, B, and C at addresses 10994 to 10998. Phase currents for all three phases are read from addresses 11010 to 11014. Positive values indicate grid import; negative values indicate export. Connecting the wattsonic to ModbusCloud Gateway gives installers continuous visibility into grid exchange balance and per-phase load asymmetry without additional metering hardware.

Name	Address	Function	Type	Unit	Access
power Total active power at the grid connection point, signed in watts.	11000	FC03	int32	W	R
currents_a AC current on grid phase A, scaled in tenths of an ampere.	11010	FC03	uint16	A	R
currents_b AC current on grid phase B, scaled in tenths of an ampere.	11012	FC03	uint16	A	R
currents_c AC current on grid phase C, scaled in tenths of an ampere.	11014	FC03	uint16	A	R
powers_a Active power at the grid meter for phase A, signed in watts.	10994	FC03	int32	W	R
powers_b Active power at the grid meter for phase B, signed in watts.	10996	FC03	int32	W	R
powers_c Active power at the grid meter for phase C, signed in watts.	10998	FC03	int32	W	R

Sunway wattsonic (grid)

Overview

Use cases

Installation

Things to watch for

Registers (7)

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