All power registers read zero even though the meter is live. Why?

Modbus TCP slave mode must be explicitly enabled in the EM300 web interface. If it was never activated, the device will accept TCP connections but return zeroed holding registers. Log in to the meter's web UI, navigate to the communication settings, enable Modbus TCP, and save. Then restart the poll in the ModbusCloud portal.

Power values appear but seem roughly half the expected figure. What is wrong?

The EM300 reports active and reactive power as unsigned 32-bit integers split into positive (import) and negative (export) registers. If you are summing them without accounting for direction, the net result will be incorrect. Use active_power_pos minus active_power_neg to derive net active power in your dashboard formula.

The Gateway connects but register reads time out intermittently. What should I check?

The EM300 supports a limited number of simultaneous Modbus TCP connections. If other systems (inverters, building controllers) are also polling the meter, connection slots may be exhausted. Reduce the number of concurrent Modbus clients or increase the poll interval in the ModbusCloud portal to avoid contention.

Energy totalizer registers (addresses 512 and above) return unexpected large values. Is scaling off?

The cumulative energy registers are 64-bit unsigned integers (uint64) spread across four consecutive 16-bit Modbus words in big-endian word order. Ensure your Modbus client assembles all four words with the most-significant word first. Misassembly of word order is the most common cause of implausible energy totals.

Free Modbus template: BControl EM300

Name: BControl EM300
Brand: BControl
SKU: b3f56adc-5803-48c7-a556-72505d7c97d7

The BControl EM300 is a three-phase bidirectional energy meter designed for industrial and commercial grid monitoring, typically deployed at the grid connection point of PV systems, battery storage installations, and multi-circuit distribution boards. This template reads the meter over Modbus TCP, covering total and per-phase active power (import and export), reactive power (inductive and capacitive), per-phase voltage and current, grid frequency, and cumulative energy totals for both consumption and production. Installers gain a complete real-time picture of grid interaction without additional hardware.

Registers (31)

31 read / 0 write

Name	Address	Function	Type	Unit	Access
active_power_pos Total active power import (consumption) across all three phases.	0	FC03	uint32	W	R
active_power_neg Total active power export (feed-in) across all three phases.	2	FC03	uint32	W	R
reactive_power_pos Total reactive power in the inductive direction, all phases.	4	FC03	uint32	var	R
reactive_power_neg Total reactive power in the capacitive direction, all phases.	6	FC03	uint32	var	R
frequency Grid frequency in hertz, typically 50 Hz.	26	FC03	uint32	Hz	R
active_power_l1_pos Active power import on phase L1.	40	FC03	uint32	W	R
active_power_l1_neg Active power export on phase L1.	42	FC03	uint32	W	R
reactive_power_l1_pos Inductive reactive power on phase L1.	44	FC03	uint32	var	R
reactive_power_l1_neg Capacitive reactive power on phase L1.	46	FC03	uint32	var	R
current_l1 RMS current on phase L1, amperes.	60	FC03	uint32	A	R
voltage_l1 RMS phase-to-neutral voltage on phase L1, volts.	62	FC03	uint32	V	R
active_power_l2_pos Active power import on phase L2.	80	FC03	uint32	W	R
active_power_l2_neg Active power export on phase L2.	82	FC03	uint32	W	R
reactive_power_l2_pos Inductive reactive power on phase L2.	84	FC03	uint32	var	R
reactive_power_l2_neg Capacitive reactive power on phase L2.	86	FC03	uint32	var	R
current_l2 RMS current on phase L2, amperes.	100	FC03	uint32	A	R
voltage_l2 RMS phase-to-neutral voltage on phase L2, volts.	102	FC03	uint32	V	R
active_power_l3_pos Active power import on phase L3.	120	FC03	uint32	W	R
active_power_l3_neg Active power export on phase L3.	122	FC03	uint32	W	R
reactive_power_l3_pos Inductive reactive power on phase L3.	124	FC03	uint32	var	R
reactive_power_l3_neg Capacitive reactive power on phase L3.	126	FC03	uint32	var	R
current_l3 RMS current on phase L3, amperes.	140	FC03	uint32	A	R
voltage_l3 RMS phase-to-neutral voltage on phase L3, volts.	142	FC03	uint32	V	R
active_consumption_energy Cumulative active energy imported from the grid, watt-hours.	512	FC03	uint64	Wh	R
active_production_energy Cumulative active energy exported to the grid, watt-hours.	516	FC03	uint64	Wh	R
active_consumption_energy_l1 Cumulative active energy imported on phase L1.	592	FC03	uint64	Wh	R
active_production_energy_l1 Cumulative active energy exported on phase L1.	596	FC03	uint64	Wh	R
active_consumption_energy_l2 Cumulative active energy imported on phase L2.	672	FC03	uint64	Wh	R
active_production_energy_l2 Cumulative active energy exported on phase L2.	676	FC03	uint64	Wh	R
active_consumption_energy_l3 Cumulative active energy imported on phase L3.	752	FC03	uint64	Wh	R
active_production_energy_l3 Cumulative active energy exported on phase L3.	756	FC03	uint64	Wh	R