Sph10K Modbus Register 1021: Grid Power

Technical Definition

The register Grid Power at address 1021 is used to monitor grid power on the Sph10K.

• Protocol: Modbus RTU
• Data Type: S DWORD
• Unit: W
• Access: Read Only

How to Read (Python pymodbus)

Use this code snippet to read this specific value via RS485:

from pymodbus.client.sync import ModbusSerialClient

client = ModbusSerialClient(method='rtu', port='/dev/ttyUSB0', baudrate=9600)
client.connect()

# Read Grid Power (Address: 1021)
# Note: Check if your device uses 0-based or 1-based addressing
result = client.read_input_registers(address=1021, count=2, unit=1)

if not result.isError():
    print(f"Raw Value: {result.registers}")
else:
    print("Error reading register")

client.close()

Integration (Home Assistant)

Paste this into your configuration.yaml:

- platform: modbus_controller
  name: "Grid Power"
  address: 1021
  value_type: S_DWORD
  unit_of_measurement: "W"

Connection Diagram

Here is the standard RS485 wiring for this configuration:

graph TD
    PLC[Host Controller / Home Assistant]
    Device[Sph10K]

    PLC -- "A+ (D+)" --> Device
    PLC -- "B- (D-)" --> Device
    PLC -- GND --> Device

💡 Engineer's Insight

Analysis: Measures the power flowing between the grid and the system. Units: Watts (W). Positive for export, negative for import.

Troubleshooting: Zero means no grid interaction; check grid connection, inverter, or load/generation balance.