The power register always reads zero or a fixed wrong value. What is wrong?

E3/DC stores its 32-bit power values in swapped word order (low word first, high word second), sometimes called int32s or int32sw. If your client reads the two 16-bit registers in standard big-endian order, the result will be incorrect. Confirm that your Modbus client or the ModbusCloud Gateway decodes the register as a swapped int32.

The gateway connects but the portal shows no data. What should I check?

First confirm that Modbus TCP is actually switched on in the E3/DC menu, not just Modbus. The feature requires two separate toggles: Modbus enabled, then Modbus TCP enabled. Also verify the unit ID matches (default is 1) and that no local firewall or VLAN is blocking port 502 between the Gateway and the E3/DC device.

Register values look correct at first but then freeze or disconnect intermittently.

E3/DC devices do not always re-establish a dropped TCP connection automatically. If the ModbusCloud Gateway loses the session, it must reconnect. Ensure the polling interval is not set too short, as very frequent queries can stress the E3/DC Modbus stack. A poll interval of 10 seconds or longer is generally stable.

The sign of the power value seems inverted. Is positive import or export?

Per the E3/DC Modbus specification, a positive value at register 40073 means the system is drawing power from the grid (import), and a negative value means the system is feeding power into the grid (export). If your dashboard shows the opposite of what you expect, check that no scale factor of -1 has been applied in the template or your portal configuration.

Free Modbus template: E3/DC e3dc (grid)

Name: E3/DC e3dc (grid)
Brand: E3/DC
SKU: 25d8d71d-3acb-40a2-ba3c-2d169862a78c

The E3/DC e3dc (grid) is a single-register Modbus TCP meter template targeting the grid connection point of E3/DC home power stations (S10 product family). It reads the instantaneous grid power from holding register 40073 as a signed 32-bit integer: positive values indicate power drawn from the grid, negative values indicate export to the grid. The ModbusCloud Gateway connects to the E3/DC unit over the local Ethernet network on port 502. This template gives installers and energy managers a live view of grid exchange in the ModbusCloud portal without any additional hardware.