Siemens RDF302 Documentation page 19

External / return air
temperature sensor
Purge function
Caution
Avoid damage from
moisture
Minimum output
ON-time / OFF-time
Floor heating /
Floor cooling
Floor temperature
limitation function
Recommended values
for P51:
Siemens
Building Technologies
The thermostat acquires the room temperature via built-in sensor, external room
temperature sensor (QAA32), or external return air temperature sensor (QAH11.1)
connected to multifunctional input X1 or X2.
Inputs X1 or X2 must be commissioned accordingly. See section 3.9 "Multi-
functional input".
The changeover sensor ensures changeover from heating to cooling mode based
on the acquired water temperature. We recommend activating the "Purge" function
(parameter P50) with 2-port valves. This function ensures correct acquisition of the
medium temperature even if the 2-port valve is closed for an extended period of
time. The valve is then opened for 1 to 5 minutes (adjustable) at 2-hour intervals
during off hours.
The "Purge" function (parameter P50) must be disabled if the thermostat is used in
compressor-based applications.
In very warm and humid climates, the fan can be run periodically or continuously at
a low fan speed (e.g. in empty apartments or shops) in Economy mode by setting
parameter P61, in order to avoid damage from moisture due to lack of air
circulation. See also section 3.8 "Fan control", under "Fan kick function".
Limit the ON/OFF switching cycle to protect the HVAC equipment, e.g. compressor
and reduce wear and tear. The minimum output on-time and off-time for 2-position
control output can be adjusted from 1 to 20 minutes via parameters P48 and P49.
The factory setting is 1 minute.
Readjusting the setpoint or heating / cooling mode changeover immediately results
in calculation of the output state; the outputs may not hold the minimum 1-minute
ON/OFF time.
If parameter P48 or P49 is set to above 1 minute, the minimum ON/OFF time for
the control output is maintained as set, even if the setpoint or changeover mode is
readjusted.
All heating sequences can also be used for floor heating.
You can use fan coil unit heating / cooling sequences for floor heating or cooling by
disabling the fan via parameter P52.
The floor temperature should be limited for 2 reasons: Comfort and protection of
the floor.
The floor temperature sensor, connected to multifunctional input X1 or X2, acquires
the floor temperature. If the temperature exceeds the parameterized limit (parame-
ter P51), the heating valve is fully closed until the floor temperature drops to a level
2 K below the parameterized limit.
This function is factory-set to OFF (disabled).
Input X1 or X2 must be commissioned accordingly (P38 or P40 = 1).
See section 3.9 "Multifunctional input".
Living rooms:
Up to 26 °C for long-time presence, up to 28 °C for short-time presence.
Bath rooms:
Up to 28 °C for long-time presence, up to 30 °C for short-time presence.
RDF302 Basic documentation
Functions
19 / 58
CE1P3079en
07 Dec 20111