Why does power_a always read zero even in bright sunlight?

Modbus TCP must be explicitly enabled on the S10 and the E3/DC protocol selected in the menu. If the interface is active but power_a stays zero, confirm the unit ID is set to 1 and the gateway is polling address 40067, not 40068. A one-register offset is a frequent configuration mistake across Modbus clients.

The gateway connects but no values appear in the portal. What now?

Check that the S10 IP is accessible on TCP port 502 from the Gateway network segment. Firewalls or VLANs can silently block Modbus traffic. Also verify the reconnect interval is configured: after an S10 restart the Modbus connection is not re-established automatically unless a reconnect timeout is set.

Why does power_b sometimes show very large numbers?

Power_b is the high 16-bit word of the grid power int32 pair. When the E3/DC system is exporting to the grid, this word will be 32768 or above as part of the two's-complement int32 encoding. Read the value as a signed int32 spanning both registers, not as a standalone uint16, to get the correct grid direction and magnitude.

Values look correct most of the time but jump to garbage after several hours. Why?

The E3/DC Modbus connection can time out silently. If your polling interval is very long or network interruptions occur, the S10 may drop the TCP session. Configure the ModbusCloud Gateway with a reconnect interval so connections are automatically re-established without requiring a manual portal intervention.

Free Modbus template: E3/DC e3dc (pv)

Name: E3/DC e3dc (pv)
Brand: E3/DC
SKU: 568c324b-347d-4399-8f2b-7e3c531ec35b

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Free Modbus template: E3/DC e3dc (pv) | ModbusCloud

Registers (2)

2 read / 0 write

Name	Address	Function	Type	Unit	Access
power_a Instantaneous PV generation power in watts, signed int32.	40067	FC03	int32	W	R
power_b High word of grid power int32, used to resolve direction.	40075	FC03	int32		R