Siemens RDF302

Installation

1. 1Wire the Siemens RDF302 to the Modbus RTU bus using a twisted pair cable connected to the A and B terminals on the thermostat.
2. 2Set a unique Modbus slave address on each RDF302 using the on-device configuration menu.
3. 3Configure the serial port on the ModbusCloud gateway (MCG or MLP series) to 19200 baud, even parity (8E1).
4. 4Import the Siemens RDF302 template from the ModbusCloud template library and assign the correct slave address.
5. 5Verify communication by checking that room temperature and setpoint values appear on the ModbusCloud dashboard.

Things to watch for

01

The gateway cannot communicate with the RDF302. What should I check first?

Verify that the baud rate is set to 19200 and parity is configured as even (8E1) on both the gateway and the thermostat. Also confirm that the A and B wiring is not swapped.

02

Can I connect multiple RDF302 thermostats on the same Modbus RTU bus?

Yes. Each thermostat must have a unique slave address. Assign addresses through the RDF302 on-device menu before connecting them to the bus.

03

The room temperature reading shows an unexpected value. What could be wrong?

Check that the register scaling in the template matches the firmware version on your RDF302. Some firmware revisions use a different decimal factor. Also ensure there are no address conflicts on the bus.

04

Can I write the setpoint while someone is also adjusting it locally on the thermostat?

Yes, but the last written value wins. A local change on the thermostat will override a remote setpoint, and vice versa. Coordinate with occupants if both methods are used.

Registers (2)

2 read / 1 write

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