Belimo JR Actuator Modbus RTU

Use cases

• Monitor real-time valve position and temperature sensor readings on a cloud dashboard for remote HVAC sites.
• Create an alert when a malfunction flag is raised so the installer can respond before comfort is affected.
• Adjust the relative position setpoint of a butterfly valve remotely to rebalance a chilled water circuit.
• Configure the bus watchdog timeout and fail action to ensure safe valve behavior during communication loss.
• Track actuator service information over time to plan preventive maintenance across multiple buildings.

Installation

1. 1Wire the ModbusCloud gateway (MCG or MLP series) to the Belimo JR actuator using a shielded RS-485 cable, connecting A, B, and GND terminals.
2. 2Set a unique Modbus RTU address on the Belimo JR actuator using the device's configuration interface or DIP switches.
3. 3Confirm the baud rate is set to 19200 on both the actuator and the ModbusCloud gateway.
4. 4Check bus termination by reading register 99 and enable termination on the last device of the RS-485 daisy chain.
5. 5Import the Belimo JR Actuator Modbus RTU template in the ModbusCloud platform and assign it to the correct gateway and Modbus address.
6. 6Verify live data in the ModbusCloud dashboard by confirming position feedback and temperature values are updating correctly.

Things to watch for

01

The gateway cannot communicate with the Belimo JR actuator. What should I check?

Verify that the RS-485 wiring is correct (A to A, B to B, GND to GND). Confirm the baud rate is set to 19200 on both the gateway and the actuator, and ensure the Modbus address is unique on the bus.

02

How do I verify bus termination?

Read register 99 on the actuator to check the current bus termination status. Enable termination only on the first and last device of the RS-485 bus segment.

03

What happens if the Modbus connection is lost?

The bus watchdog feature defines the actuator behavior on communication loss. Configure the watchdog fail action and timeout registers through the template to set a safe fallback position for the valve.

04

Can I connect multiple Belimo JR actuators to one gateway?

Yes, daisy-chain multiple actuators on the same RS-485 bus. Each actuator must have a unique Modbus address. Add a separate template instance in ModbusCloud for each device.

Registers (29)

18 read / 11 write

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