All three voltage registers return zero. What is wrong?

The UMG 801 only produces measurements when at least one voltage input carries an L-N voltage above 10 Veff. Confirm the voltage measurement terminals are correctly wired and that the supply is live. Also verify that the device has completed startup before polling.

Voltage readings look correct on the display but wrong in the portal.

Janitza float registers use Big-Endian (MSB-first) word order. Confirm your Modbus TCP client is set to Big-Endian for 32-bit floats. A swapped word order will produce values that are either garbled or implausibly large. The ModbusCloud Gateway handles this automatically when using the supplied template.

The gateway connects but register reads time out intermittently.

The UMG 801 refreshes its Modbus registers every 200 ms. Timeouts often result from network congestion or an overly short TCP timeout in the polling configuration. Set the read timeout to at least 1000 ms, and ensure no other Modbus master is polling the same unit ID at the same time.

I cannot reach the UMG 801 by IP. How do I find its address?

If the device has no DHCP assignment and no static IP is known, connect a PC directly to the UMG 801 with a patch cable and access the default IP address documented in the Janitza commissioning guide. Alternatively, use the front panel navigation buttons to read the current IP address from the network settings screen.

Free Modbus template: Janitza UMG801

The Janitza UMG 801 is a modular DIN-rail power analyzer used in industrial and commercial energy monitoring systems. This ModbusCloud template reads the three phase-to-neutral voltages (L1, L2, L3) from the UMG 801 over Modbus TCP, using 32-bit float registers updated every 200 ms. Values are delivered with transformer ratios already applied, so no additional scaling is required in your portal. Connecting the Janitza UMG 801 to the ModbusCloud Gateway gives installers a live, per-phase voltage view across all monitored distribution points.

Name	Address	Function	Type	Unit	Access
voltage_l1 Phase-to-neutral voltage on line L1, in volts.	19000	FC03	float32	V	R
voltage_l2 Phase-to-neutral voltage on line L2, in volts.	19002	FC03	float32	V	R
voltage_l3 Phase-to-neutral voltage on line L3, in volts.	19004	FC03	float32	V	R