All register values read as zero or clearly wrong. Why?

The EM300 returns int32 values as two consecutive 16-bit words in MSB-first (big-endian) byte order within each word, but the word order is most-significant word first. Confirm your Modbus master is assembling the two words in the correct order. A swapped word order produces a value that is numerically plausible but wrong by a large factor.

The gateway connects but active power reads negative unexpectedly. Is that an error?

No. The EM300 protocol defines negative active power as exported power and positive as imported power. If your site is a net exporter at the measurement point, negative readings are correct. Verify the CT orientation matches the intended import direction per the installation manual.

RS485 communication is intermittent or produces CRC errors. How do I fix it?

Intermittent errors on RS485 are almost always caused by missing bus termination. The EM300 communication protocol requires a 120-ohm resistor between the A and B lines at the master end and at the last device on the bus. Also verify that baud rate and parity settings on the meter and Gateway match exactly.

Apparent power unit in the register list shows W but should be VA. Is the scaling correct?

The template input labels apparent_power with the unit W, but the EM300 protocol reports apparent power in VA at the same numeric scale as the active-power registers. Treat the raw value as VA when reading address 42. Reactive power at address 44 is likewise in var. No additional scaling factor is applied beyond the int32 raw value.

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Registers (19)

19 read / 0 write

Name	Address	Function	Type	Unit	Access
voltage_l1 Phase L1 line-to-neutral voltage, in volts.	0	FC04	int32	V	R
voltage_l2 Phase L2 line-to-neutral voltage, in volts.	2	FC04	int32	V	R
voltage_l3 Phase L3 line-to-neutral voltage, in volts.	4	FC04	int32	V	R
current_l1 Instantaneous current on phase L1, in amperes.	12	FC04	int32	A	R
current_l2 Instantaneous current on phase L2, in amperes.	14	FC04	int32	A	R
current_l3 Instantaneous current on phase L3, in amperes.	16	FC04	int32	A	R
active_power_l1 Instantaneous active power on phase L1, in watts.	18	FC04	int32	W	R
active_power_l2 Instantaneous active power on phase L2, in watts.	20	FC04	int32	W	R
active_power_l3 Instantaneous active power on phase L3, in watts.	22	FC04	int32	W	R
apparent_power_l1 Instantaneous apparent power on phase L1, in volt-amperes.	24	FC04	int32	W	R
apparent_power_l2 Instantaneous apparent power on phase L2, in volt-amperes.	26	FC04	int32	W	R
apparent_power_l3 Instantaneous apparent power on phase L3, in volt-amperes.	28	FC04	int32	W	R
reactive_power_l1 Instantaneous reactive power on phase L1, in var.	30	FC04	int32	W	R
reactive_power_l2 Instantaneous reactive power on phase L2, in var.	32	FC04	int32	W	R
reactive_power_l3 Instantaneous reactive power on phase L3, in var.	34	FC04	int32	W	R
active_power Total three-phase active power sum, in watts.	40	FC04	int32	W	R
apparent_power Total three-phase apparent power sum, in volt-amperes.	42	FC04	int32	VA	R
reactive_power Total three-phase reactive power sum, in var.	44	FC04	int32	var	R
frequency Grid frequency, in hertz, typically 50 or 60.	51	FC04	uint16	Hz	R