SAX SAX Power Home (Plus) (grid)

Installation

1. 1Enable Modbus TCP on the SAX Power Home (Plus) via the device web interface under the communication or Modbus section, and confirm port 502 is accessible on the local network.
2. 2Connect the ModbusCloud Gateway to the same LAN as the SAX Power Home (Plus) using an Ethernet cable, ensuring both devices obtain IP addresses on the same subnet.
3. 3In the ModbusCloud portal, add the gateway, import this template, and set the Modbus unit ID to 40 (decimal), which is the slave ID for the integrated smartmeter entity on SAX Power devices.
4. 4Trigger a manual poll of register 48 in the portal and verify the returned watt value matches the power reading shown on the SAX Power device display or web interface.

Things to watch for

01

Why does register 48 return a value around 16384 instead of the actual grid power?

The SAX Power register map documents an offset of 16384 for register 48. The raw uint16 reading includes this fixed offset, so you must subtract 16384 from the raw value to obtain the real grid power in watts. Configure this offset in your ModbusCloud channel scaling settings.

02

The gateway connects but register 48 returns zero or an error. What should I check?

Verify that the Modbus unit ID is set to 40 (decimal, equivalent to 0x28 hex) in the ModbusCloud portal. The smartmeter values on the SAX Power Home (Plus) are exposed on slave ID 40, not the default ID 1. Using the wrong unit ID is the most common cause of empty readings.

03

Why does the grid power value fluctuate wildly between polls?

The SAX Power Home (Plus) delivers all register values as 16-bit unsigned integers. Ensure the data type in the portal is set to uint16 (big-endian). Using a 32-bit type or wrong byte order will cause the value to appear random or wrap incorrectly across positive and negative power flows.

04

Modbus TCP connection drops intermittently. How can I stabilise it?

The SAX Power device runs its Modbus server on port 502. Avoid polling intervals below 2 seconds, as the embedded TCP stack can reject rapid successive connections. Set the ModbusCloud Gateway poll interval to at least 5 seconds and enable connection keep-alive if supported, to reduce reconnect overhead.

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