Port 502 is closed even after enabling Modbus TCP. Why?

The EMMA requires the exact client IP address of the polling device to be entered in the Modbus TCP settings in the FusionSolar app. If the field is left blank or contains a wrong IP, the EMMA will refuse connections. Re-enter the ModbusCloud Gateway's IP, save, and retry. Some firmware versions also require a device restart before the port opens.

The power register reads zero at midday. What should I check?

Confirm the inverter is powered on and producing. The EMMA exposes PV output power via the inverter it manages over RS485; if the RS485 link between the EMMA and the SUN2000 inverter is broken or the inverter is in standby, the register will return zero. Check the RS485 wiring and the inverter status in the FusionSolar app.

Energy values look unexpectedly large or small. Is there a scaling issue?

Yes. The official SmartHEMS Modbus definition specifies a gain of 100 for the energy register (address 30344), meaning the raw register value is in units of 0.01 kWh. Ensure your ModbusCloud template applies this scaling. If the portal shows raw counts instead of kWh, check that the template's scaling factor is correctly applied.

Only one client can connect at a time. How do I avoid conflicts?

The Huawei EMMA Modbus TCP interface typically accepts only one concurrent client connection. If another system (such as a home automation platform) is already polling the EMMA, the ModbusCloud Gateway will be refused or will receive no response. Disable or schedule around other polling clients, or configure a single aggregator to forward data.

Free Modbus template: Huawei EMMA (pv)

The Huawei EMMA (Energy Management Assistant) is a DIN-rail smart energy controller that connects to Huawei SUN2000 inverters via RS485 and exposes plant data over Modbus TCP. This template reads the two core PV registers: real-time PV output power and cumulative inverter total energy yield. With these values in ModbusCloud, installers get a live and historical view of solar generation without deploying a separate data logger. The Huawei EMMA (pv) template requires Modbus TCP to be enabled under the device's communication settings before the ModbusCloud Gateway can poll it.

Name	Address	Function	Type	Unit	Access
power Real-time PV output power reported by the inverter, in watts.	30354	FC03	int32	W	R
energy Cumulative inverter total energy yield, in watt-hours.	30344	FC03	uint32	Wh	R