All register values show zero or NaN. What is wrong?

The UMG604 only produces valid measurements when at least one voltage input exceeds approximately 10 V RMS phase-to-neutral. Confirm the analyser is wired to live conductors and that current transformer connections are correct. Also verify the unit ID in the portal matches the value set on the device.

Float values look scrambled or wildly incorrect. Why?

Each float32 register spans two consecutive 16-bit Modbus words. If your master or gateway swaps word order, the decoded float will be garbage. The UMG604 uses big-endian (high word first) IEEE 754 encoding. Confirm your Modbus master is set to the same byte and word order before assuming a wiring fault.

The gateway connects but the portal shows no data. What should I check?

Confirm TCP port 502 is reachable from the gateway (not blocked by a local firewall or VLAN policy). The UMG604 can also act as a Modbus gateway to RS485 slave devices; if the unit ID is set to route to a downstream slave rather than the UMG604 itself, reads will fail. Set the unit ID to the value assigned to the UMG604 directly.

Address indexing appears off by one compared to the Janitza manual. Why?

Janitza's official Modbus address list uses zero-based addressing, while some Modbus masters add an offset of one. The addresses in this template follow the zero-based convention used by the OpenEMS implementation. If your readings are consistently shifted, check whether your master applies a +1 offset and adjust accordingly.

Free Modbus template: Janitza UMG604

Name: Janitza UMG604
Brand: Janitza
SKU: 7ff049f9-0520-4266-8fb2-6dc870b2a2fd

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Free Modbus template: Janitza UMG604 | ModbusCloud

Registers (17)

17 read / 0 write

Name	Address	Function	Type	Unit	Access
voltage_l1 Phase L1 to neutral RMS voltage, in volts.	1317	FC03	float32	V	R
voltage_l2 Phase L2 to neutral RMS voltage, in volts.	1319	FC03	float32	V	R
voltage_l3 Phase L3 to neutral RMS voltage, in volts.	1321	FC03	float32	V	R
current_l1 RMS current on phase L1, in amperes.	1325	FC03	float32	A	R
current_l2 RMS current on phase L2, in amperes.	1327	FC03	float32	A	R
current_l3 RMS current on phase L3, in amperes.	1329	FC03	float32	A	R
active_power_l1 Instantaneous active power on phase L1, in watts.	1333	FC03	float32	W	R
active_power_l2 Instantaneous active power on phase L2, in watts.	1335	FC03	float32	W	R
active_power_l3 Instantaneous active power on phase L3, in watts.	1337	FC03	float32	W	R
reactive_power_l1 Instantaneous reactive power on phase L1, in var.	1341	FC03	float32	W	R
reactive_power_l2 Instantaneous reactive power on phase L2, in var.	1343	FC03	float32	W	R
reactive_power_l3 Instantaneous reactive power on phase L3, in var.	1345	FC03	float32	W	R
active_power Total three-phase active power sum, in watts.	1369	FC03	float32	W	R
reactive_power Total three-phase reactive power sum, in var.	1371	FC03	float32	var	R
frequency Grid frequency measured at the device, in hertz.	1439	FC03	float32	Hz	R
active_consumption_energy Cumulative active energy drawn from the grid, in watt-hours.	9851	FC03	float32	Wh	R
active_production_energy Cumulative active energy delivered to the grid, in watt-hours.	9863	FC03	float32	Wh	R