Basic Documentation

Functions
Multifunctional input, digital input
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4.9 Multifunctional input, digital input
The thermostat has 2 basic inputs B1/X1 and S1/X2.
An NTC type sensor such as NTC 3k (AI, analog input) or a switch (DI, digital
input) can be connected to the input terminals. The functionality of the inputs can
be configured via P38 and P39 for B1/X1, P40 and P41 for S1/X2.
The current temperature or state of the inputs B1/S1/X1/X2 is available on Modbus
for monitoring purposes.
The parameters can be set to the following values:
#
Function of input
Description
Type
B1/S1/X1/
X2
0
Not used
No function
--
1
Room temperature
external sensor/return
air temperature
Sensor input for external room temperature
sensor or return air temperature sensor to
acquire the current room temperature, or floor
heating temperature sensor to limit the heating
output.
Note: The room temperature is acquired via the
built-in sensor if the floor temperature limitation
function is enabled in parameter P51.
AI
Heating/
cooling
changeover
2
Heating/cooling
changeover
Analog input for "Automatic heating/cooling
changeover" function.
Heating/cooling changeover is also possible via
Modbus. In this case, the function must not be
assigned to local inputs B1/X1, S1/X2. See also
Additional functions [➙ 26].
Diagnostic value 0 ˚C is displayed for a closed
contact, 100 ˚C for an open contact, if a switch
is connected.
AI
Window contact
3
Window contact
Digital input to change over the operating mode
to Protection.
If the window contact is active, user operations
are ineffective.
Window contact is also possible via Modbus. In
this case, do not assign the function to local
inputs B1/X1, S1/X2. See also Operating modes
[➙ 17].
DI
4
Dewpoint sensor
(RDF660MB only)
Digital input for a dewpoint sensor to detect
condensation. Cooling is stopped if
condensation occurs.
DI
Enable electric
heater
5
Enable electric heater
(RDF660MB only)
Digital input to enable/disable the electric heater
via remote control.
Enable electric heater is also possible via
Mobus. In this case, do not assign the function
to local inputs B1/X1, S1/X2. See also Control
sequences [➙ 31].
DI
Fault information
6
Fault input
(RDF660MB only)
Digital input to signal an external fault (e.g.: dirty
air filter).
Note: Fault displays have no impact on the
thermostat's operation. They merely represent a
visual signal.
DI
B1/X1 input
S1/X2 input