Basic Documentation
Table Of Contents
- 1 About this document
- 2 Overview
- 3 Notes
- 4 Functions
- 4.1 Temperature control
- 4.2 Operating modes
- 4.3 Room temperature setpoint
- 4.4 Application overview
- 4.5 Additional functions
- 4.6 Control sequences
- 4.7 Control outputs
- 4.8 Fan control
- 4.9 Multifunctional input, digital input
- 4.10 Handling system faults
- 4.11 Modbus RTU mode
- 4.12 Communication objects
- 4.13 Control parameters
- 5 Connection
- 6 Technical data
- 7 Dimensions
- Index
Functions
Control sequences
4
A6V12114068_en--_c
33 | 66
4.6.3 2-pipe fan coil unit with electric heater (RDF660MB
only)
In 2-pipe applications with electric heater, the thermostat controls a valve in
heating/cooling mode with changeover, heating only, or cooling only plus an
auxiliary electric heater.
Cooling only is factory-set (P01 = 1) with enabled electric heater (P13).
In cooling mode, the valve receives an Open command if the acquired temperature
is above the setpoint.
The electric heater receives an On command if the acquired room temperature
drops below "setpoint" minus "dead zone" (= setpoint for electric heater) while the
electric heater is enabled (P13 = ON).
"Setpoint for electric heater" is limited by parameter "Maximum setpoint for Comfort
mode" (P10).
In heating mode, the valve receives an Open command if the acquired
temperature is below the setpoint. The electric heater is used as an additional
heating source when the heating energy controlled by the valve is insufficient.
The electric heater receives an On command, if the temperature is below "setpoint"
minus "setpoint differential" (= setpoint for electric heater).
The electric heater is active in heating mode only and the control output for the
valve is permanently disabled when manual changeover is selected (P01 = 2).
Remote enabling/disabling of the electric heater is possible via input X1 or X2 for
tariff regulations, energy savings, etc.
Input X1 or X2 must be commissioned accordingly (P38, P40). See Multifunctional
input, digital input [➙ 43].
The electric heater can also be enabled/disabled via Modbus.
Do not assign the function to a local input X1 or X2 if “Enable electric heater” input
is used via Modbus.
CAUTION
The electric heater must always be protected by a safety limit thermostat!
The diagrams below show the control sequence for On/Off control.
Heating or cooling with
auxiliary heater
Electric heating, active
in cooling mode
Note
Electric heating in
heating mode
Electric heating and
manual changeover
Digital input "Enable
electric heater
Enable electric heater
Note
On/Off control
Control sequence
On/Off output