Basic Documentation

Functions
Control sequences
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A6V12166490_en--_c
4.6.3 2-pipe fan coil unit with electric heater
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 [➙ 40].
The diagrams below show the control sequence for On/Off control.
Heating mode
(automatic changeover = heating or
heating only)
Cooling mode
(man. / auto. changeover = cooling or
cooling only)
Heating mode with manual changeover (P01 = 2) (manual changeover = heating)
T[°C] Room temperature
W Room temperature setpoint
V1 Control command “Valve” or
“Compressor”
E1 Control command “Electric
heater”
SDH Switching differential “Heating”
(P30)
SDC Switching differential “Cooling”
(P31)
Xdz Dead zone (P33)
wD Setpoint differential (P34)
● The diagrams only show the PI thermostat’s proportional part.
For setting sequence and control outputs, see Application overview [➙ 21],
Overview of sequences (setting via P01) [➙ 30] and Control outputs [➙ 36].
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
On/Off control
Control sequence
On/Off output
Note