Temperature control - Basic Documentation - RDF302 - RDF302.B - RDF302/VB

Semi-flush mount room thermostats with RS485 Modbus communications RDF302, RDF302.B, RDF302/VB

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Thermostats (temperature controller with sensor)
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Technical Documentation > Basic Documentation
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General note: Parameters

Setting of the control parameters (P01, etc., mentioned throughout the document) is described in section 3.13.

Temperature control

The thermostat acquires the room temperature via built-in sensor, external room temperature sensor (QAA32), or external return air temperature sensor (QAH11.1), and maintains the setpoint by delivering actuator control commands to heating and/or cooling equipment. The following control outputs are available:

  • ON/OFF control (2-position)

  • Modulating PI/P control with 3-position control output (only for 2-pipe applications)

The switching differential or proportional band is 2 K for heating mode and 1 K for cooling mode (adjustable via parameters P30 and P31).
The integral action time for modulating PI control is 5 minutes (adjustable via parameter P35).


The display shows the acquired room temperature or the Comfort setpoint, selecta­ble via parameter P06. The factory setting displays the current room temperature.
Use parameter P04 to display the room temperature or setpoint in °F rather than °C as needed.

Room temperature

The acquired room temperature (internal or external sensor) is also available as information on the Modbus.


  • With automatic changeover or continuous heating / cooling, symbols / indicate that the system currently heats or cools (heating or cooling output is activated).

  • With manual changeover (P01 = 2), symbols / indicate that the system currently operates in heating or cooling mode. Thus, the symbols are displayed even when the thermostat operates in the neutral zone.

Concurrent display of
°C and °F

Concurrent display of the current temperature or setpoint in °C and °F (parameter P07 = 1) is possible on the thermostats.

Outside temperature

The outside temperature can be displayed on the room thermostat by setting parameter P07 = 2. This temperature value has only information character which comes from the master device in the Modbus network.

Time of day

Time of day via Modbus can be displayed on the room thermostat by setting parameter P07 = 3 or 4. The display format is either in 12- or in 24-hour format.
The information can be received from a master device in the Modbus network.