Port 502 is open but all registers return errors. Why?

The EMMA requires Modbus TCP to be explicitly enabled via the FusionSolar app using installer credentials. Without this step the service is inactive even if the port appears reachable. Also confirm TLS is disabled in the communication settings, as an encrypted connection will reject plain Modbus frames.

Grid power reads zero even though energy is clearly flowing. What is wrong?

Check that the correct unit ID is configured. The EMMA uses logical device addressing in Modbus TCP frames, so a mismatched unit ID returns no data rather than an error. Confirm the unit ID with the installer documentation and update it in the template assignment.

Power values look inverted: positive when drawing from grid, negative when exporting.

The Huawei EMMA sign convention is: positive means power fed to the grid, negative means power supplied from the grid. If your dashboard logic expects the opposite convention, apply a scaling factor of minus one on the power and energy registers in the ModbusCloud portal channel settings.

Phase current registers show large inconsistent values between polling cycles.

The int32 current registers span two consecutive Modbus registers and use big-endian byte order as documented in the Huawei SmartHEMS Modbus interface specification. Verify that the Gateway reads the full two-register block in a single request and that big-endian word order is selected in the template, otherwise the high and low words will be swapped.

Free Modbus template: Huawei EMMA (grid)

The Huawei EMMA (Energy Management Assistant) is a residential energy management controller that integrates metering, communication, and load coordination in a single unit. This ModbusCloud template reads the EMMA's built-in grid meter via Modbus TCP, capturing grid power, cumulative energy, and per-phase currents (A, B, C) at the grid connection point. The sign convention follows Huawei documentation: positive values indicate power fed to the grid, negative values indicate power drawn from the grid. With these readings in your ModbusCloud portal, you can track import and export behaviour in real time alongside your full Huawei PV and storage installation.

Name	Address	Function	Type	Unit	Access
power Active power at the grid connection point, signed integer in watts.	31657	FC03	int32	W	R
energy Cumulative active energy at the grid connection point, watt-hours.	31679	FC03	int64	Wh	R
currents_a AC current on phase A at the grid connection point.	31651	FC03	int32	A	R
currents_b AC current on phase B at the grid connection point.	31653	FC03	int32	A	R
currents_c AC current on phase C at the grid connection point.	31655	FC03	int32	A	R