SIEMENS RDF302 Flush mount room thermostat
Heating applications
- AC 230 V operating voltage
- Large display with Backlight
- On/off or 3-position control
- Automatic or manual fan speed control
- 1-speed or 3-speed fan selection
- Operating modes: Comfort, Economy and Protection
- Control depending on the room or the return air temperature
- Automatic or manual heating/cooling changeover
- Minimum and maximum limitation of room temperature setpoint
- Commissioning and control parameters via local HMI or RS485 Modbus
- RS485 communicative interface in Modbus RTU slave mode
- Mounting on recessed square conduit box, 60.3 mm fixing centers
- User and parameter settings can be retained or restored with power loss RDF302 & RDF302/VB Only
- 2 multifunctional inputs for keycard contact, external sensor, etc.
Use
Room temperature control (heating or cooling) in individual rooms and zones by means of:
- 2-pipe fan coil units
- 2-pipe fan coil units with electrical heater
- 4-pipe fan coil units
- Compressors in DX-type equipment
- Compressors in DX-type equipment with electrical heater
- The RDF302, RDF302/VB and RDF302.B controls:
- One single or 3-speed fan
- One or two on/off valve actuators
- One on/off valve actuator and one 1-stage electrical heater
- One 3-position valve actuator
- One 1-stage compressor in DX-type equipment, or one 1-stage compressor with electrical heater
Used in systems with:
- Heating or cooling mode
- Automatic heating/cooling changeover
- Manual heating/cooling changeover
- Heating and cooling mode (e.g. 4-pipe system)
- The room thermostats are delivered with a fixed set of applications.
- The relevant application is selected and activated during commissioning using one of the following tools:
- Local DIP switch and HMI
- Modbus commissioning tools
Functions
Maintain room temperature via built-in temperature sensor or external room temperature/return air temperature sensor Changeover between heating and cooling mode (automatic changeover via local sensor/bus or manual changeover) Select application via DIP switches or commissioning tools Select operating mode via operating mode button on the thermostat Single speed or 3-speed fan control (automatic or manual) Display current room temperature or setpoint in °C and/or °F Minimum and maximum limitation of room temperature setpoint Key lock (automatic, manual or via bus)
Two multifunctional inputs, freely selectable for:
- Operating mode switchover contact (keycard)
- Automatic heating/cooling changeover sensor
- External room temperature sensor or return air temperature sensor
- Dew point sensor
- Electrical heater enabled
- Fault input
- Monitor input for temperature sensor or switch status
- Advanced fan control function, e.g. fan kick, fan start, selectable fan operation (enable, disable or depending on heating or cooling mode)
- Purge function together with 2-port valve in a 2-pipe changeover system
- Reminder to clean filters
- Floor heating temperature limit
- Reload factory settings for commissioning and control parameters
- RS 485 Modbus (terminals +, – and REF) for communication with Modbus compatible devices
- Display of outdoor temperature or time of day via Modbus
Applications
The thermostats support the following applications, which can be configured using the DIP switches inside the front panel of the unit or a Modbus commissioning tool. Remote configuration: All DIP switches need to be set to OFF (factory setting) to select an application via commissioning tool
Applications for fan coil systems *)
Applications for Universal systems *)
Applications for heat pump systems *)
Type summary
Ordering
- When ordering, indicate both product number / SSN number and name:
- E.g. RDF302 / S55770-T238 Modbus room thermostat
- Order valve actuators separately
Equipment combinations
3-position actuators
Accessories
Mechanical design
The thermostats consist of 2 parts:
- Front panel with electronics, operating elements and built-in room temperature sensor.
- Mounting base with power electronics.
- The rear of the mounting base contains the screw terminals.
- The base fits on a square conduit box with 60.3 mm fixing centers.
- Slide the front panel in the mounting base and snap on.
Operation and settings
- Operating mode selector
- Change fan operation
- Adjust setpoints and control parameters
Display
Operating mode
Protection
Comfort
Economy
- Displays room temperature, setpoints and control parameters
Symbol indicates current room temperature
- Fan mode
Auto fan active
Fan speed low, medium, high
- Indicates fault or reminder
- Heating/cooling mode
Cooling
Heating
Electrical heater active
- Condensation in room (dew point sensor active)
- Additional user information, like outdoor temperature (
) or time from Modbus (selectable via parameters) 
Key lock active
Engineering notes
- Device address: The device address of each RDF302… was assigned to “1“ (factory setting). If necessary, engineer/installer can change the address value through the parameter P81.
- Baud rate: The Baud rate is selectable. Four options, 4800 bps, 9600 bps, 19200 bps and 38400 bps, are available for the RDF302… adapting into the Modbus network (19200 bps is default).
- Parity: The parity can be set to none, odd or even (even is default).
- Note:: Once you made any changes on the baud rate or parity, you must reset the power before the changes become effective. To reset the power, you can consider by opening the front panel out of the mounting plate and snap it back
Mounting and installation
Mount the room thermostat on a recessed square conduit box with 60.3 mm fixing centers. Do not mount on a wall in niches or bookshelves, behind curtains, above or near heat sources, or exposed to direct solar radiation. Mount about 1.5 m above the floor
Mounting
Mount the room thermostat in a clean, dry indoor place without direct airflow from a heating / cooling device, and not exposed to dripping or splash water. In case of limited space in the conduit box, use mounting bracket ARG70.3 to increase the headroom by 10 mm.
Wiring
- See Mounting Instructions M3079 enclosed with the thermostat.
- Comply with local regulations to wire, protection and earth the thermostat.
- The device has no internal fuse for supply lines to fan and actuators. To avoid risk of fire and injury due to short-circuits, the AC 230 V mains supply line must have a circuit breaker with a rated current of no more than 10 A.
- Properly size the cables to the thermostat, fan and valve actuators for AC 230 V mains voltage.
- Use only valve actuators rated for AC 230 V.
The wiring cross section used for power supply (L, N), fan/relays (Qx) and 230 V outputs (Yx -N) must be adapted to the preceding overload protection elements (max 10A) under all circumstances. Comply under all circumstances with local regulations. - Cables of SELV inputs X1-M / X2-M: Use cables with min 230 V insulation, as the conduit box carries AC 230 V mains voltage.
- Inputs X1-M or X2-M: Several switches (e.g. summer / winter switch) may be connected in parallel. Consider overall maximum contact sensing current for switch rating.
- Isolate the cables of Modbus communication input +, – and REF for 230 V.
- No cables provided with a metal sheild.
- Disconnect from supply before opening the cover.
Commissioning notes
Applications: The room thermostats are delivered with a fixed set of applications. Select and activate the relevant application during commissioning using one of the following tools:
- Local DIP switch and HMI
- Modbus commissioning tools
Set the DIP switches before snapping the front panel to the mounting plate, if you want to select an application via DIP switches. All DIP switches need to be set to “OFF” (“remote configuration”), if you want to select an application via commissioning tools. After power is applied, the thermostat resets and all LCD segments flash, indicating that the reset was correct. After the reset, which takes about 3 seconds, the thermostat is ready for commissioning by qualified HVAC staff. RDF302.B does not have input X1 and X2.
Display “NONE”: If the “NONE” displays on the LCD, it means that the DIP switches was set to OFFOFF for remote configuration, but the application had not yet assigned to the device. The application can be set by commissioning tools via the RS485 Modbus. Each time the application is changed, the thermostat reloads the factory setting for all control parameters, except for baud rate (P68), parity (P70) and zone addresses (P81)!
Control parameters: The thermostat’s control parameters can be set to ensure optimum performance of the entire system. The parameters can be adjusted using
- Local HMI
- Modbus commissioning tools
Control sequence: The control sequence may need to be set via parameter P01 depending on the application. The factory setting for the 2-pipe application is “Cooling only”; and “Heating and Cooling” for the 4-pipe application.
Compressor-based application: When the thermostat is used with a compressor, adjust the minimum output ontime (parameter P48) and off-time (parameter P49) for Y11/Y21 to avoid damaging the compressor or shortening its life due to frequent switching.
Calibrate sensor: Recalibrate the temperature sensor if the room temperature displayed on the thermostat does not match the room temperature measured (after minimum 1 hour of operation). To do this, change parameter P05.
Setpoint and range limitation: We recommend to review the setpoints and setpoint ranges (parameters P08…P12) and change them as needed to achieve maximum comfort and save energy.
Disposal
This symbol or any other national label indicate that the product, its packaging, and, where applicable, any batteries may not be disposed of as domestic waste. Delete all personal data and dispose of the item(s) at separate collection and recycling facilities in accordance with local and national legislation. For additional details, refer to www.siemens.com/bt/disposal
Technical data
Connection terminals
- L, N Operating voltage AC 230 V
- Q1 Control output “Fan speed 1 AC 230 V”
- Q2 Control output “Fan speed 2 AC 230 V”
- Q3 Control output “Fan speed 3 AC 230 V”
- Y11,Y21 Control output “Valve” AC 230 V (N.O., for normally closed valves), output for compressor or output for electrical heater
- X1, X2 1) Multifunctional input for temperature sensor (e.g. QAH11.1) or potential-free switch
- Factory setting: X1 = Operating mode switchover contact X2 = External sensor (function can be selected via parameter P38/P40).
- M 1) Measuring neutral for sensor and switch
- + RS485 Modbus connection
- – RS485 Modbus connection
- REF RS485 signal / common ground (Differential common)
- 1) RDF302.B does not have inputs X1, X2 and M.
Connection diagrams
Application
- N1 Room thermostat RDF302…
- M1 1- or 3-speed fan
- V1 Valve actuator, 2- or 3-position
- V1, V2 Valve actuator, 2-position
- E1 Electric heater
- C1, C2 1-stage compressor
- S1, S2 Switch (keycard, window contact, presence detector, etc.)
- B1, B2 Temperature sensor (return air temperature, external room temperature, changeover sensor, etc.)
- + RS485 Modbus connection
- – RS485 Modbus connection
- REF RS485 signal/common ground (Differential common)
- RDF302.B does not have inputs X1, X2 and M.
Dimensions (mm)
Issued by
- Siemens Switzerland Ltd.
- Building Technologies Division
- International Headquarters
- Theilerstrasse 1a
- CH-6300 Zug
- Tel. +41 58 724 2424
- www.siemens.com/buildingtechnologies
SIEMENS RDF302 Flush mount room thermostat Product Specifications Guide