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Siemens RDF20U Technical Instructions

Room temperature controller with lcd for two-pipe fan coil units with electric heat
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RDF20U
Room Temperature Controller
with LCD for Two-Pipe Fan Coil
Units with Electric Heat
Description
Features
Application
Product Number
Room temperature controller with LCD for two-pipe fan coil units with electric heat.
•
Output for an on/off valve actuator
•
Output for electric heat.
•
Outputs for a three-speed fan.
•
Control depending on the room or the return air temperature.
•
Automatic heating/cooling changeover.
•
Operating modes: Normal, Economy and Standby.
•
Operating mode changeover input for remote control (Day/Night).
•
Air movement control function for avoiding damage resulting from moisture.
•
Selectable installation and control parameters.
•
Display of room temperature or setpoint (selectable).
•
Electronic minimum and maximum setpoint limits.
•
Operating voltage 24 Vac.
Typical use:
•
Control of the room temperature in individual rooms that are heated or cooled with
two-pipe fan coil units equipped with electric heat.
•
Opening or closing a valve.
•
Switching electric heat.
•
Switching a three-speed fan.
Suitable for two-pipe fan coil unit systems with:
•
Automatic heating/cooling changeover.
•
Continuous heating or cooling mode.
RDF20U
Technical Instructions
Document No. 155-334
September 27, 2007
Siemens Industry, Inc.

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Summary of Contents for Siemens RDF20U

  • Page 1 • Opening or closing a valve. • Switching electric heat. • Switching a three-speed fan. Suitable for two-pipe fan coil unit systems with: • Automatic heating/cooling changeover. • Continuous heating or cooling mode. Product Number RDF20U Siemens Industry, Inc.

  • Page 2: Operation

    60 seconds (default Parameter 21) when the electric heat is switched off. CAUTION: In the event of failure, the RDF20U cannot protect the electric heat against overheating. Therefore, the electric heat must be equipped with a separate safety device (high temperature detection thermostat).
  • Page 3 RDF20U Room Temperature Controller with LCD Technical Instructions For Two-Pipe Fan Coil Units with Electric Heat Document Number 155-334 September 27, 2007 Water-based Fan Coil Use in conjunction with one valve, either for heating and/or cooling with changeover, Application heating only or cooling only operation.
  • Page 4 Parameter P16 and exiting the parameter setting mode. Return Air Temperature The RDF20U provides control based on the measured room temperature or the fan coil (Optional) unit’s return air temperature. It detects if a QAH11.1 cable temperature sensor is connected to input 8-9 and then operates automatically according to that temperature.
  • Page 5 RDF20U Room Temperature Controller with LCD Technical Instructions For Two-Pipe Fan Coil Units with Electric Heat Document Number 155-334 September 27, 2007 Application Diagrams Figure 4. Heating Mode (Hot Water Plus Figure 5. Cooling Mode with Optional Electric Heat). Electric Heat (DIP Switch 4: ON, Electric Heat Enabled)).

  • Page 6: Operating Modes

    Technical Instructions RDF20U Room Temperature Controller with LCD Document Number 155-334 for Two-Pipe Fan Coil Units with Electric Heat September 27, 2007 Operating Modes Heating or Cooling mode with automatic changeover and manually selected fan speed (III, II or I). In Normal mode, the controller maintains the adjusted setpoint.
  • Page 7 RDF20U Room Temperature Controller with LCD Technical Instructions For Two-Pipe Fan Coil Units with Electric Heat Document Number 155-334 September 27, 2007 Table 1. Control Parameters. Para- Description Setting Range Factory meter Setting Heating setpoint in Economy mode OFF, 61F (operating mode changeover contact activated ) 41F to 68F (5C to 20C) (in increments of 0.5 K)

  • Page 8: Mechanical Design

    Technical Instructions RDF20U Room Temperature Controller with LCD Document Number 155-334 for Two-Pipe Fan Coil Units with Electric Heat September 27, 2007 Ordering The QAH11.1 temperature sensor can be used as a return air temperature or changeover sensor. The changeover sensor and the valves must be ordered separately.
  • Page 9 Active in Cooling mode Inactive in Cooling mode Engineering Notes With the RDF20U, the controller input for automatic heating/cooling changeover can also be used without the QAH11.1 cable temperature sensor: ▪ In systems without automatic changeover, the temperature sensor can be replaced by an external switch (suited for live voltage) for manual changeover.

  • Page 10: Specifications

    The cables used must meet the insulation requirements for live voltage. Calibrating the Sensor If the room temperature displayed by the controller is inconsistent with the room temperature being measured, the temperature sensor of the RDF20U can be recalibrated. To recalibrate, change Parameter P09. Operating voltage 24 Vac, +20/-25%...

  • Page 11: Wiring Terminals

    RDF20U Room Temperature Controller with LCD Technical Instructions For Two-Pipe Fan Coil Units with Electric Heat Document Number 155-334 September 27, 2007 Operation Specifications, Temperature 32°F to 122°F (0°C to 50°C) Continued Humidity <95% rh Environmental Conditions Transport and storage Temperature -13°F to 158°F (-25°C to 70°C)
  • Page 12 (Millimeters) Figure 12. Base Plate. Figure 11. RDF20U Controller. Information in this publication is based on current specifications. The company reserves the right to make changes in specifications and models as design improvements are introduced. Product or company names mentioned herein may be the trademarks of their respective owners.

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