Siemens RDF660MB

Installation

1. 1Wire the Siemens RDF660MB to the Modbus RTU bus using a twisted pair cable, connecting A and B terminals correctly.
2. 2Set a unique Modbus slave address on the RDF660MB using its local configuration menu.
3. 3Configure the baud rate to 9600 on both the thermostat and the Modbus gateway to ensure matching communication settings.
4. 4Connect the Modbus RTU bus to your ModbusCloud gateway (MCG or MLP series) via the RS485 port.
5. 5Import the Siemens RDF660MB template from the ModbusCloud template library and assign the correct slave address.
6. 6Verify communication by checking live room temperature and setpoint values on the ModbusCloud dashboard.

Things to watch for

01

Why do I read the correct room temperature but cannot change the setpoint?

The read and write registers for the room setpoint use different Modbus addresses. The read address is 4 and the write address is 103. Make sure your template is configured with both addresses correctly.

02

The gateway cannot communicate with the RDF660MB. What should I check?

Verify that the baud rate is set to 9600 on both the thermostat and the gateway. Also confirm that the A and B wiring is not swapped and that the Modbus slave address matches the one configured in ModbusCloud.

03

Can I connect multiple RDF660MB thermostats on the same Modbus RTU bus?

Yes. Assign a unique slave address to each thermostat and add a separate device instance in ModbusCloud for each one, using the same template.

04

Do I need to enable Modbus communication on the RDF660MB?

The RDF660MB variant is the Modbus enabled model. Ensure you have the MB version, as standard RDF660 models without the MB suffix do not support Modbus RTU.

Registers (3)

2 read / 1 write

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