Both power registers read zero even during daylight. Why?

The most common cause is an incorrect slave ID. The FoxESS H3 Series uses slave ID 247 by default. Confirm the value in the inverter communication menu and ensure the ModbusCloud Gateway is configured to poll the same ID. A mismatched ID returns no error, just zero or empty responses.

The gateway connects but register values seem stuck or frozen. What now?

The H3 COM connector shares pins with the energy meter or CT clamp. If the meter is also wired to the Modbus pins, bus contention can cause stale reads. Confirm your RS485 wires connect only to the designated Modbus pins on the H3 COM connector, not to the meter input pins.

Why do power_a and power_b return unexpected negative values?

Registers 31002 and 31005 are signed int16 values. Negative readings are not expected for PV power under normal operation and usually indicate a wiring polarity issue on the RS485 bus (A and B lines swapped) or a firmware edge case at very low irradiance near sunrise or sunset.

I get exception code 0x83 from the inverter. What does that mean?

Exception code 0x83 (function code 3 error) with exception 2 means the requested register address is not available on this firmware version or model variant. Confirm you are using an H3 Series unit and not an H3 PRO or H3 Smart, which use different register addresses for PV power.

Free Modbus template: FoxESS H3 Series Hybrid Inverter (pv)

The FoxESS H3 Series is a three-phase hybrid solar inverter designed for residential and small commercial PV installations with battery storage. This Modbus RTU template reads the per-string DC power output of the H3 Series inverter: PV string 1 power at register 31002 and PV string 2 power at register 31005, both as signed 16-bit watt values. Connecting these two live readings into the ModbusCloud Gateway lets installers verify string-level generation balance, catch shading or soiling issues early, and keep a timestamped record of PV yield without relying on the FoxESS cloud.

Name	Address	Function	Type	Unit	Access
power_a Instantaneous DC power output of PV string 1, watts.	31002	FC03	int16	W	R
power_b Instantaneous DC power output of PV string 2, watts.	31005	FC03	int16	W	R